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authorEduardo Chappa <echappa@gmx.com>2013-02-03 00:59:38 -0700
committerEduardo Chappa <echappa@gmx.com>2013-02-03 00:59:38 -0700
commit094ca96844842928810f14844413109fc6cdd890 (patch)
treee60efbb980f38ba9308ccb4fb2b77b87bbc115f3 /imap/docs/rfc
downloadalpine-094ca96844842928810f14844413109fc6cdd890.tar.xz
Initial Alpine Version
Diffstat (limited to 'imap/docs/rfc')
-rw-r--r--imap/docs/rfc/README70
-rw-r--r--imap/docs/rfc/rfc1732.txt283
-rw-r--r--imap/docs/rfc/rfc1733.txt171
-rw-r--r--imap/docs/rfc/rfc2061.txt171
-rw-r--r--imap/docs/rfc/rfc2062.txt451
-rw-r--r--imap/docs/rfc/rfc2087.txt283
-rw-r--r--imap/docs/rfc/rfc2088.txt115
-rw-r--r--imap/docs/rfc/rfc2177.txt227
-rw-r--r--imap/docs/rfc/rfc2180.txt787
-rw-r--r--imap/docs/rfc/rfc2193.txt507
-rw-r--r--imap/docs/rfc/rfc2195.txt283
-rw-r--r--imap/docs/rfc/rfc2221.txt283
-rw-r--r--imap/docs/rfc/rfc2342.txt563
-rw-r--r--imap/docs/rfc/rfc2683.txt1291
-rw-r--r--imap/docs/rfc/rfc2971.txt451
-rw-r--r--imap/docs/rfc/rfc3348.txt339
-rw-r--r--imap/docs/rfc/rfc3501.txt6052
-rw-r--r--imap/docs/rfc/rfc3502.txt395
-rw-r--r--imap/docs/rfc/rfc3503.txt507
-rw-r--r--imap/docs/rfc/rfc3516.txt451
-rw-r--r--imap/docs/rfc/rfc3656.txt1067
-rw-r--r--imap/docs/rfc/rfc3691.txt283
-rw-r--r--imap/docs/rfc/rfc4314.txt1515
-rw-r--r--imap/docs/rfc/rfc4315.txt451
-rw-r--r--imap/docs/rfc/rfc4422.txt1851
-rw-r--r--imap/docs/rfc/rfc4466.txt955
-rw-r--r--imap/docs/rfc/rfc4467.txt1011
-rw-r--r--imap/docs/rfc/rfc4468.txt787
-rw-r--r--imap/docs/rfc/rfc4469.txt731
-rw-r--r--imap/docs/rfc/rfc4505.txt507
-rw-r--r--imap/docs/rfc/rfc4549.txt1963
-rw-r--r--imap/docs/rfc/rfc4551.txt1403
-rw-r--r--imap/docs/rfc/rfc4616.txt619
-rw-r--r--imap/docs/rfc/rfc4731.txt451
-rw-r--r--imap/docs/rfc/rfc4752.txt563
-rw-r--r--imap/docs/rfc/rfc4790.txt1459
-rw-r--r--imap/docs/rfc/rfc4959.txt395
-rw-r--r--imap/docs/rfc/rfc4978.txt507
-rw-r--r--imap/docs/rfc/rfc5032.txt283
-rw-r--r--imap/docs/rfc/rfc5051.txt395
-rw-r--r--imap/docs/rfc/rfc5092.txt1795
-rw-r--r--imap/docs/rfc/rfc5161.txt395
-rw-r--r--imap/docs/rfc/rfc5162.txt1291
-rw-r--r--imap/docs/rfc/rfc5234.txt899
44 files changed, 35256 insertions, 0 deletions
diff --git a/imap/docs/rfc/README b/imap/docs/rfc/README
new file mode 100644
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--- /dev/null
+++ b/imap/docs/rfc/README
@@ -0,0 +1,70 @@
+The following documents are necessary to understand the syntax rules
+most of the remaining documents. Note that some documents refer to
+RFC 2234 which has been replaced by RFC 5234:
+ rfc5234.txt Augmented BNF for Syntax Specifications - ABNF
+ rfc4466.txt Collected Extensions to IMAP4 ABNF
+
+
+The following documents specify the IMAP protocol:
+ rfc3501.txt Internet Message Access Protocol - Version 4rev1
+
+
+The following documents provide additional information which is useful
+in understanding the IMAP protocol:
+ rfc1733.txt Distributed Electronic Mail Models in IMAP4
+ rfc2180.txt IMAP4 Multi-Accessed Mailbox Practice
+ rfc2683.txt IMAP4 Implementation Recommendations
+ rfc4549.txt Synchronization Operations for Disconnected IMAP4 Clients
+
+
+The following documents describe extensions to the IMAP protocol.
+Items marked with "*" are supported in this distribution:
+ rfc4314.txt ACL
+ * rfc3516.txt BINARY
+ rfc4469.txt CATENATE
+ * rfc3348.txt CHILDREN
+ rfc4978.txt COMPRESS
+ rfc4551.txt CONDSTORE
+ rfc5161.txt ENABLE
+ * rfc4731.txt ESEARCH
+ rfc2971.txt ID
+ * rfc2177.txt IDLE
+ * rfc2088.txt LITERAL+
+ * rfc2221.txt LOGIN-REFERRALS
+ * rfc2193.txt MAILBOX-REFERRALS
+ * rfc3502.txt MULTIAPPEND
+ * rfc2342.txt NAMESPACE
+ rfc5162.txt QRESYNC
+ rfc2087.txt QUOTA
+ * rfc4959.txt SASL-IR
+ * rfc4315.txt UIDPLUS
+ * rfc3691.txt UNSELECT
+ rfc4467.txt URLAUTH
+ * rfc5032.txt WITHIN
+
+
+The following documents describe SASL:
+ rfc4422.txt Simple Authentication and Security Layer (SASL)
+and the SASL mechanisms supported in this distribution:
+ rfc4505.txt ANONYMOUS
+ rfc2195.txt CRAM-MD5
+ rfc4752.txt GSSAPI
+ rfc4616.txt PLAIN
+
+
+The following documents relate to internationalization issues:
+ rfc4790.txt Internet Application Protocol Collation Registry
+ rfc5051.txt i;unicode-casemap - Simple Unicode Collation Algorithm
+
+
+The following documents are primarily of historic interest:
+ rfc1732.txt IMAP4 Compatibility with IMAP2 and IMAP2bis
+ rfc2061.txt IMAP4 Compatibility with IMAP2bis
+ rfc2062.txt Internet Message Access Protocol - Obsolete Syntax
+
+
+The following documents discuss matters which are related to IMAP:
+ rfc3503.txt MDN Profile for IMAP
+ rfc3656.txt MUPDATE Distributed Mailbox Database Protocol
+ rfc4468.txt Message Submission BURL Extension
+ rfc5092.txt IMAP URL Scheme
diff --git a/imap/docs/rfc/rfc1732.txt b/imap/docs/rfc/rfc1732.txt
new file mode 100644
index 00000000..cfae89c0
--- /dev/null
+++ b/imap/docs/rfc/rfc1732.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 1732 University of Washington
+Category: Informational December 1994
+
+
+ IMAP4 COMPATIBILITY WITH IMAP2 AND IMAP2BIS
+
+
+Status of this Memo
+
+ This memo provides information for the Internet community. This memo
+ does not specify an Internet standard of any kind. Distribution of
+ this memo is unlimited.
+
+Introduction
+
+ This is a summary of hints and recommendations to enable an IMAP4
+ implementation to interoperate with implementations that conform to
+ earlier specifications. None of these hints and recommendations are
+ required by the IMAP4 specification; implementors must decide for
+ themselves whether they want their implementation to fail if it
+ encounters old software.
+
+ IMAP4 has been designed to be upwards compatible with earlier
+ specifications. For the most part, IMAP4 facilities that were not in
+ earlier specifications should be invisible to clients unless the
+ client asks for the facility.
+
+ In some cases, older servers may support some of the capabilities
+ listed as being "new in IMAP4" as experimental extensions to the
+ IMAP2 protocol described in RFC 1176.
+
+ This information may not be complete; it reflects current knowledge
+ of server and client implementations as well as "folklore" acquired
+ in the evolution of the protocol.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin [Page 1]
+
+RFC 1732 IMAP4 - Compatibility December 1994
+
+
+IMAP4 client interoperability with old servers
+
+ In general, a client should be able to discover whether an IMAP2
+ server supports a facility by trial-and-error; if an attempt to use a
+ facility generates a BAD response, the client can assume that the
+ server does not support the facility.
+
+ A quick way to check whether a server implementation supports the
+ IMAP4 specification is to try the CAPABILITY command. An OK response
+ that includes the IMAP4 capability value indicates a server that
+ supports IMAP4; a BAD response or one without the IMAP4 capability
+ value indicates an older server.
+
+ The following is a list of facilities that are only in IMAP4, and
+ suggestions for how new clients might interoperate with old servers:
+
+ CAPABILITY command
+ A BAD response to this command indicates that the server
+ implements IMAP2 (or IMAP2bis) and not IMAP4.
+
+ AUTHENTICATE command.
+ Use the LOGIN command.
+
+ LSUB and LIST commands
+ Try the RFC 1176 FIND command.
+
+ * in a sequence
+ Use the number of messages in the mailbox from the EXISTS
+ unsolicited response.
+
+ SEARCH extensions (character set, additional criteria)
+ Reformulate the search request using only the searching
+ options listed in search_old in the IMAP4 grammar. This may
+ entail doing multiple searches to achieve the desired
+ results.
+
+ BODYSTRUCTURE fetch data item
+ Try to fetch the non-extensible BODY data item.
+
+ body section number 0
+ Fetch the entire message and extract the header.
+
+ RFC822.HEADER.LINES and RFC822.HEADER.LINES.NOT fetch data items
+ Use RFC822.HEADER and remove the unwanted information.
+
+ BODY.PEEK[section], RFC822.PEEK, and RFC822.TEXT.PEEK fetch data
+ items Use the corresponding non-PEEK versions and manually
+ clear the \Seen flag as necessary.
+
+
+
+Crispin [Page 2]
+
+RFC 1732 IMAP4 - Compatibility December 1994
+
+
+ UID fetch data item and the UID commands
+ No equivalent capabilitity exists in older servers.
+
+ FLAGS.SILENT, +FLAGS.SILENT, and -FLAGS.SILENT store data items
+ Use the corresponding non-SILENT versions and ignore the
+ untagged FETCH responses which com eback.
+
+
+ The following IMAP4 facilities were introduced in the experimental
+ IMAP2bis revisions to RFC-1176, and may be present in a server that
+ does not support the CAPABILITY command:
+
+ CREATE, DELETE, and RENAME commands
+ To test whether these commands are present, try a CREATE
+ INBOX command. If the response is NO, these commands are
+ supported by the server. If the response is BAD, they are
+ not. Older servers without the CREATE capability may sup-
+ port implicit creation of a mailbox by a COPY command with a
+ non-existant name as the destination.
+
+ APPEND command
+ To test whether this command is present, try to append a
+ zero-length stream to a mailbox name that is known not to
+ exist (or at least, highly unlikely to exist) on the remote
+ system.
+
+ SUBSCRIBE and UNSUBSCRIBE commands
+ Try the form of these commands with the optional MAILBOX
+ keyword.
+
+ EXAMINE command
+ Use the SELECT command instead.
+
+ flags and internal date argument to APPEND command
+ Try the APPEND without any flag list and internal date argu-
+ ments.
+
+ BODY, BODY[section], and FULL fetch data items
+ Use RFC822.TEXT and ALL instead. Server does not support
+ MIME.
+
+ PARTIAL command
+ Use the appropriate FETCH command and ignore the unwanted
+ data.
+
+
+ IMAP4 client implementations must accept all responses and data for-
+ mats documented in the IMAP4 specification, including those labeled
+
+
+
+Crispin [Page 3]
+
+RFC 1732 IMAP4 - Compatibility December 1994
+
+
+ as obsolete. This includes the COPY and STORE unsolicited responses
+ and the old format of dates and times. In particular, client imple-
+ mentations must not treat a date/time as a fixed format string; nor
+ may they assume that the time begins at a particular octet.
+
+ IMAP4 client implementations must not depend upon the presence of any
+ server extensions that are not in the base IMAP4 specification.
+
+ The experimental IMAP2bis version specified that the TRYCREATE spe-
+ cial information token is sent as a separate unsolicited OK response
+ instead of inside the NO response.
+
+ The FIND BBOARDS, FIND ALL.BBOARDS, and BBOARD commands of RFC 1176
+ are removed from IMAP4. There is no equivalent to the bboard com-
+ mands, which provided a separate namespace with implicit restrictions
+ on what may be done in that namespace.
+
+ Older server implementations may automatically create the destination
+ mailbox on COPY if that mailbox does not already exist. This was how
+ a new mailbox was created in older specifications. If the server
+ does not support the CREATE command (see above for how to test for
+ this), it will probably create a mailbox on COPY.
+
+ Older server implementations may not preserve flags or internal dates
+ on COPY. Some server implementations may not permit the preservation
+ of certain flags on COPY or their setting with APPEND as site policy.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin [Page 4]
+
+RFC 1732 IMAP4 - Compatibility December 1994
+
+
+IMAP4 server interoperability with old clients
+
+ In general, there should be no interoperation problem between a
+ server conforming to the IMAP4 specification and a well-written
+ client that conforms to an earlier specification. Known problems are
+ noted below:
+
+ Poor wording in the description of the CHECK command in earlier
+ specifications implied that a CHECK command is the way to get the
+ current number of messages in the mailbox. This is incorrect. A
+ CHECK command does not necessarily result in an EXISTS response.
+ Clients must remember the most recent EXISTS value sent from the
+ server, and should not generate unnecessary CHECK commands.
+
+ An incompatibility exists with COPY in IMAP4. COPY in IMAP4
+ servers does not automatically create the destination mailbox if
+ that mailbox does not already exist. This may cause problems with
+ old clients that expect automatic mailbox creation in COPY.
+
+ The PREAUTH unsolicited response is new in IMAP4. It is highly
+ unlikely that an old client would ever see this response.
+
+ The format of dates and times has changed due to the impending end
+ of the century. Clients that fail to accept a four-digit year or
+ a signed four-digit timezone value will not work properly with
+ IMAP4.
+
+ An incompatibility exists with the use of "\" in quoted strings.
+ This is best avoided by using literals instead of quoted strings
+ if "\" or <"> is embedded in the string.
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+Author's Address:
+
+ Mark R. Crispin
+ Networks and Distributed Computing, JE-30
+ University of Washington
+ Seattle, WA 98195
+
+ Phone: (206) 543-5762
+
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+Crispin [Page 5]
+
diff --git a/imap/docs/rfc/rfc1733.txt b/imap/docs/rfc/rfc1733.txt
new file mode 100644
index 00000000..2ec385f0
--- /dev/null
+++ b/imap/docs/rfc/rfc1733.txt
@@ -0,0 +1,171 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 1733 University of Washington
+Category: Informational December 1994
+
+
+ DISTRIBUTED ELECTRONIC MAIL MODELS IN IMAP4
+
+
+Status of this Memo
+
+ This memo provides information for the Internet community. This memo
+ does not specify an Internet standard of any kind. Distribution of
+ this memo is unlimited.
+
+
+Distributed Electronic Mail Models
+
+ There are three fundamental models of client/server email: offline,
+ online, and disconnected use. IMAP4 can be used in any one of these
+ three models.
+
+ The offline model is the most familiar form of client/server email
+ today, and is used by protocols such as POP-3 (RFC 1225) and UUCP.
+ In this model, a client application periodically connects to a
+ server. It downloads all the pending messages to the client machine
+ and deletes these from the server. Thereafter, all mail processing
+ is local to the client. This model is store-and-forward; it moves
+ mail on demand from an intermediate server (maildrop) to a single
+ destination machine.
+
+ The online model is most commonly used with remote filesystem
+ protocols such as NFS. In this model, a client application
+ manipulates mailbox data on a server machine. A connection to the
+ server is maintained throughout the session. No mailbox data are
+ kept on the client; the client retrieves data from the server as is
+ needed. IMAP4 introduces a form of the online model that requires
+ considerably less network bandwidth than a remote filesystem
+ protocol, and provides the opportunity for using the server for CPU
+ or I/O intensive functions such as parsing and searching.
+
+ The disconnected use model is a hybrid of the offline and online
+ models, and is used by protocols such as PCMAIL (RFC 1056). In this
+ model, a client user downloads some set of messages from the server,
+ manipulates them offline, then at some later time uploads the
+ changes. The server remains the authoritative repository of the
+ messages. The problems of synchronization (particularly when
+ multiple clients are involved) are handled through the means of
+ unique identifiers for each message.
+
+
+
+Crispin [Page 1]
+
+RFC 1733 IMAP4 - Model December 1994
+
+
+ Each of these models have their own strengths and weaknesses:
+
+ Feature Offline Online Disc
+ ------- ------- ------ ----
+ Can use multiple clients NO YES YES
+ Minimum use of server connect time YES NO YES
+ Minimum use of server resources YES NO NO
+ Minimum use of client disk resources NO YES NO
+ Multiple remote mailboxes NO YES YES
+ Fast startup NO YES NO
+ Mail processing when not online YES NO YES
+
+ Although IMAP4 has its origins as a protocol designed to accommodate
+ the online model, it can support the other two models as well. This
+ makes possible the creation of clients that can be used in any of the
+ three models. For example, a user may wish to switch between the
+ online and disconnected models on a regular basis (e.g. owing to
+ travel).
+
+ IMAP4 is designed to transmit message data on demand, and to provide
+ the facilities necessary for a client to decide what data it needs at
+ any particular time. There is generally no need to do a wholesale
+ transfer of an entire mailbox or even of the complete text of a
+ message. This makes a difference in situations where the mailbox is
+ large, or when the link to the server is slow.
+
+ More specifically, IMAP4 supports server-based RFC 822 and MIME
+ processing. With this information, it is possible for a client to
+ determine in advance whether it wishes to retrieve a particular
+ message or part of a message. For example, a user connected to an
+ IMAP4 server via a dialup link can determine that a message has a
+ 2000 byte text segment and a 40 megabyte video segment, and elect to
+ fetch only the text segment.
+
+ In IMAP4, the client/server relationship lasts only for the duration
+ of the TCP connection. There is no registration of clients. Except
+ for any unique identifiers used in disconnected use operation, the
+ client initially has no knowledge of mailbox state and learns it from
+ the IMAP4 server when a mailbox is selected. This initial transfer
+ is minimal; the client requests additional state data as it needs.
+
+ As noted above, the choice for the location of mailbox data depends
+ upon the model chosen. The location of message state (e.g. whether
+ or not a message has been read or answered) is also determined by the
+ model, and is not necessarily the same as the location of the mailbox
+ data. For example, in the online model message state can be co-
+ located with mailbox data; it can also be located elsewhere (on the
+ client or on a third agent) using unique identifiers to achieve
+
+
+
+Crispin [Page 2]
+
+RFC 1733 IMAP4 - Model December 1994
+
+
+ common reference across sessions. The latter is particularly useful
+ with a server that exports public data such as netnews and does not
+ maintain per-user state.
+
+ The IMAP4 protocol provides the generality to implement these
+ different models. This is done by means of server and (especially)
+ client configuration, and not by requiring changes to the protocol or
+ the implementation of the protocol.
+
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+
+Author's Address:
+
+ Mark R. Crispin
+ Networks and Distributed Computing, JE-30
+ University of Washington
+ Seattle, WA 98195
+
+ Phone: (206) 543-5762
+
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin [Page 3]
+
diff --git a/imap/docs/rfc/rfc2061.txt b/imap/docs/rfc/rfc2061.txt
new file mode 100644
index 00000000..7cb02bb2
--- /dev/null
+++ b/imap/docs/rfc/rfc2061.txt
@@ -0,0 +1,171 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 2061 University of Washington
+Category: Informational December 1996
+
+
+ IMAP4 COMPATIBILITY WITH IMAP2BIS
+
+Status of this Memo
+
+ This memo provides information for the Internet community. This memo
+ does not specify an Internet standard of any kind. Distribution of
+ this memo is unlimited.
+
+Introduction
+
+ The Internet Message Access Protocol (IMAP) has been through several
+ revisions and variants in its 10-year history. Many of these are
+ either extinct or extremely rare; in particular, several undocumented
+ variants and the variants described in RFC 1064, RFC 1176, and RFC
+ 1203 fall into this category.
+
+ One variant, IMAP2bis, is at the time of this writing very common and
+ has been widely distributed with the Pine mailer. Unfortunately,
+ there is no definite document describing IMAP2bis. This document is
+ intended to be read along with RFC 1176 and the most recent IMAP4
+ specification (RFC 2060) to assist implementors in creating an IMAP4
+ implementation to interoperate with implementations that conform to
+ earlier specifications. Nothing in this document is required by the
+ IMAP4 specification; implementors must decide for themselves whether
+ they want their implementation to fail if it encounters old software.
+
+ At the time of this writing, IMAP4 has been updated from the version
+ described in RFC 1730. An implementor who wishes to interoperate
+ with both RFC 1730 and RFC 2060 should refer to both documents.
+
+ This information is not complete; it reflects current knowledge of
+ server and client implementations as well as "folklore" acquired in
+ the evolution of the protocol. It is NOT a description of how to
+ interoperate with all variants of IMAP, but rather with the old
+ variant that is most likely to be encountered. For detailed
+ information on interoperating with other old variants, refer to RFC
+ 1732.
+
+IMAP4 client interoperability with IMAP2bis servers
+
+ A quick way to check whether a server implementation supports the
+ IMAP4 specification is to try the CAPABILITY command. An OK response
+ will indicate which variant(s) of IMAP4 are supported by the server.
+
+
+
+Crispin Informational [Page 1]
+
+RFC 2061 IMAP4 Compatibility December 1996
+
+
+ If the client does not find any of its known variant in the response,
+ it should treat the server as IMAP2bis. A BAD response indicates an
+ IMAP2bis or older server.
+
+ Most IMAP4 facilities are in IMAP2bis. The following exceptions
+ exist:
+
+ CAPABILITY command
+ The absense of this command indicates IMAP2bis (or older).
+
+ AUTHENTICATE command.
+ Use the LOGIN command.
+
+ LSUB, SUBSCRIBE, and UNSUBSCRIBE commands
+ No direct functional equivalent. IMAP2bis had a concept
+ called "bboards" which is not in IMAP4. RFC 1176 supported
+ these with the BBOARD and FIND BBOARDS commands. IMAP2bis
+ augmented these with the FIND ALL.BBOARDS, SUBSCRIBE BBOARD,
+ and UNSUBSCRIBE BBOARD commands. It is recommended that
+ none of these commands be implemented in new software,
+ including servers that support old clients.
+
+ LIST command
+ Use the command FIND ALL.MAILBOXES, which has a similar syn-
+ tax and response to the FIND MAILBOXES command described in
+ RFC 1176. The FIND MAILBOXES command is unlikely to produce
+ useful information.
+
+ * in a sequence
+ Use the number of messages in the mailbox from the EXISTS
+ unsolicited response.
+
+ SEARCH extensions (character set, additional criteria)
+ Reformulate the search request using only the RFC 1176 syn-
+ tax. This may entail doing multiple searches to achieve the
+ desired results.
+
+ BODYSTRUCTURE fetch data item
+ Use the non-extensible BODY data item.
+
+ body sections HEADER, TEXT, MIME, HEADER.FIELDS, HEADER.FIELDS.NOT
+ Use body section numbers only.
+
+ BODY.PEEK[section]
+ Use BODY[section] and manually clear the \Seen flag as
+ necessary.
+
+
+
+
+
+Crispin Informational [Page 2]
+
+RFC 2061 IMAP4 Compatibility December 1996
+
+
+ FLAGS.SILENT, +FLAGS.SILENT, and -FLAGS.SILENT store data items
+ Use the corresponding non-SILENT versions and ignore the
+ untagged FETCH responses which come back.
+
+ UID fetch data item and the UID commands
+ No functional equivalent.
+
+ CLOSE command
+ No functional equivalent.
+
+
+ In IMAP2bis, the TRYCREATE special information token is sent as a
+ separate unsolicited OK response instead of inside the NO response.
+
+ IMAP2bis is ambiguous about whether or not flags or internal dates
+ are preserved on COPY. It is impossible to know what behavior is
+ supported by the server.
+
+IMAP4 server interoperability with IMAP2bis clients
+
+ The only interoperability problem between an IMAP4 server and a
+ well-written IMAP2bis client is an incompatibility with the use of
+ "\" in quoted strings. This is best avoided by using literals
+ instead of quoted strings if "\" or <"> is embedded in the string.
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Aveneue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Informational [Page 3]
+
diff --git a/imap/docs/rfc/rfc2062.txt b/imap/docs/rfc/rfc2062.txt
new file mode 100644
index 00000000..865d1dad
--- /dev/null
+++ b/imap/docs/rfc/rfc2062.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 2062 University of Washington
+Category: Informational December 1996
+
+
+ Internet Message Access Protocol - Obsolete Syntax
+
+Status of this Memo
+
+ This memo provides information for the Internet community. This memo
+ does not specify an Internet standard of any kind. Distribution of
+ this memo is unlimited.
+
+Abstract
+
+ This document describes obsolete syntax which may be encountered by
+ IMAP4 implementations which deal with older versions of the Internet
+ Mail Access Protocol. IMAP4 implementations MAY implement this
+ syntax in order to maximize interoperability with older
+ implementations.
+
+ This document repeats information from earlier documents, most
+ notably RFC 1176 and RFC 1730.
+
+Obsolete Commands and Fetch Data Items
+
+ The following commands are OBSOLETE. It is NOT required to support
+ any of these commands or fetch data items in new server
+ implementations. These commands are documented here for the benefit
+ of implementors who may wish to support them for compatibility with
+ old client implementations.
+
+ The section headings of these commands are intended to correspond
+ with where they would be located in the main document if they were
+ not obsoleted.
+
+6.3.OBS.1. FIND ALL.MAILBOXES Command
+
+ Arguments: mailbox name with possible wildcards
+
+ Data: untagged responses: MAILBOX
+
+ Result: OK - find completed
+ NO - find failure: can't list that name
+ BAD - command unknown or arguments invalid
+
+
+
+
+
+
+Crispin Informational [Page 1]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+ The FIND ALL.MAILBOXES command returns a subset of names from the
+ complete set of all names available to the user. It returns zero
+ or more untagged MAILBOX replies. The mailbox argument to FIND
+ ALL.MAILBOXES is similar to that for LIST with an empty reference,
+ except that the characters "%" and "?" match a single character.
+
+ Example: C: A002 FIND ALL.MAILBOXES *
+ S: * MAILBOX blurdybloop
+ S: * MAILBOX INBOX
+ S: A002 OK FIND ALL.MAILBOXES completed
+
+6.3.OBS.2. FIND MAILBOXES Command
+
+ Arguments: mailbox name with possible wildcards
+
+ Data: untagged responses: MAILBOX
+
+ Result: OK - find completed
+ NO - find failure: can't list that name
+ BAD - command unknown or arguments invalid
+
+ The FIND MAILBOXES command returns a subset of names from the set
+ of names that the user has declared as being "active" or
+ "subscribed". It returns zero or more untagged MAILBOX replies.
+ The mailbox argument to FIND MAILBOXES is similar to that for LSUB
+ with an empty reference, except that the characters "%" and "?"
+ match a single character.
+
+ Example: C: A002 FIND MAILBOXES *
+ S: * MAILBOX blurdybloop
+ S: * MAILBOX INBOX
+ S: A002 OK FIND MAILBOXES completed
+
+6.3.OBS.3. SUBSCRIBE MAILBOX Command
+
+ Arguments: mailbox name
+
+ Data: no specific data for this command
+
+ Result: OK - subscribe completed
+ NO - subscribe failure: can't subscribe to that name
+ BAD - command unknown or arguments invalid
+
+ The SUBSCRIBE MAILBOX command is identical in effect to the
+ SUBSCRIBE command. A server which implements this command must be
+ able to distinguish between a SUBSCRIBE MAILBOX command and a
+ SUBSCRIBE command with a mailbox name argument of "MAILBOX".
+
+
+
+
+Crispin Informational [Page 2]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+ Example: C: A002 SUBSCRIBE MAILBOX #news.comp.mail.mime
+ S: A002 OK SUBSCRIBE MAILBOX to #news.comp.mail.mime
+ completed
+ C: A003 SUBSCRIBE MAILBOX
+ S: A003 OK SUBSCRIBE to MAILBOX completed
+
+
+6.3.OBS.4. UNSUBSCRIBE MAILBOX Command
+
+ Arguments: mailbox name
+
+ Data: no specific data for this command
+
+ Result: OK - unsubscribe completed
+ NO - unsubscribe failure: can't unsubscribe that name
+ BAD - command unknown or arguments invalid
+
+ The UNSUBSCRIBE MAILBOX command is identical in effect to the
+ UNSUBSCRIBE command. A server which implements this command must
+ be able to distinguish between a UNSUBSCRIBE MAILBOX command and
+ an UNSUBSCRIBE command with a mailbox name argument of "MAILBOX".
+
+ Example: C: A002 UNSUBSCRIBE MAILBOX #news.comp.mail.mime
+ S: A002 OK UNSUBSCRIBE MAILBOX from #news.comp.mail.mime
+ completed
+ C: A003 UNSUBSCRIBE MAILBOX
+ S: A003 OK UNSUBSCRIBE from MAILBOX completed
+
+6.4.OBS.1 PARTIAL Command
+
+ Arguments: message sequence number
+ message data item name
+ position of first octet
+ number of octets
+
+ Data: untagged responses: FETCH
+
+ Result: OK - partial completed
+ NO - partial error: can't fetch that data
+ BAD - command unknown or arguments invalid
+
+ The PARTIAL command is equivalent to the associated FETCH command,
+ with the added functionality that only the specified number of
+ octets, beginning at the specified starting octet, are returned.
+ Only a single message can be fetched at a time. The first octet
+ of a message, and hence the minimum for the starting octet, is
+ octet 1.
+
+
+
+
+Crispin Informational [Page 3]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+ The following FETCH items are valid data for PARTIAL: RFC822,
+ RFC822.HEADER, RFC822.TEXT, BODY[<section>], as well as any .PEEK
+ forms of these.
+
+ Any partial fetch that attempts to read beyond the end of the text
+ is truncated as appropriate. If the starting octet is beyond the
+ end of the text, an empty string is returned.
+
+ The data are returned with the FETCH response. There is no
+ indication of the range of the partial data in this response. It
+ is not possible to stream multiple PARTIAL commands of the same
+ data item without processing and synchronizing at each step, since
+ streamed commands may be executed out of order.
+
+ There is no requirement that partial fetches follow any sequence.
+ For example, if a partial fetch of octets 1 through 10000 breaks
+ in an awkward place for BASE64 decoding, it is permitted to
+ continue with a partial fetch of 9987 through 19987, etc.
+
+ The handling of the \Seen flag is the same as in the associated
+ FETCH command.
+
+ Example: C: A005 PARTIAL 4 RFC822 1 1024
+ S: * 1 FETCH (RFC822 {1024}
+ S: Return-Path: <gray@cac.washington.edu>
+ S: ...
+ S: ......... FLAGS (\Seen))
+ S: A005 OK PARTIAL completed
+
+6.4.5.OBS.1 Obsolete FETCH Data Items
+
+ The following FETCH data items are obsolete:
+
+ BODY[<...>0] A body part number of 0 is the [RFC-822] header of
+ the message. BODY[0] is functionally equivalent to
+ BODY[HEADER], differing in the syntax of the
+ resulting untagged FETCH data (BODY[0] is
+ returned).
+
+ RFC822.HEADER.LINES <header_list>
+ Functionally equivalent to BODY.PEEK[HEADER.LINES
+ <header_list>], differing in the syntax of the
+ resulting untagged FETCH data (RFC822.HEADER is
+ returned).
+
+
+
+
+
+
+
+Crispin Informational [Page 4]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+ RFC822.HEADER.LINES.NOT <header_list>
+ Functionally equivalent to
+ BODY.PEEK[HEADER.LINES.NOT <header_list>],
+ differing in the syntax of the resulting untagged
+ FETCH data (RFC822.HEADER is returned).
+
+ RFC822.PEEK Functionally equivalent to BODY.PEEK[], except for
+ the syntax of the resulting untagged FETCH data
+ (RFC822 is returned).
+
+ RFC822.TEXT.PEEK
+ Functionally equivalent to BODY.PEEK[TEXT], except
+ for the syntax of the resulting untagged FETCH data
+ (RFC822.TEXT is returned).
+
+Obsolete Responses
+
+ The following responses are OBSOLETE. Except as noted below, these
+ responses MUST NOT be transmitted by new server implementations.
+ Client implementations SHOULD accept these responses.
+
+ The section headings of these responses are intended to correspond
+ with where they would be located in the main document if they were
+ not obsoleted.
+
+7.2.OBS.1. MAILBOX Response
+
+ Data: name
+
+ The MAILBOX response MUST NOT be transmitted by server
+ implementations except in response to the obsolete FIND MAILBOXES
+ and FIND ALL.MAILBOXES commands. Client implementations that do
+ not use these commands MAY ignore this response. It is documented
+ here for the benefit of implementors who may wish to support it
+ for compatibility with old client implementations.
+
+ This response occurs as a result of the FIND MAILBOXES and FIND
+ ALL.MAILBOXES commands. It returns a single name that matches the
+ FIND specification. There are no attributes or hierarchy
+ delimiter.
+
+ Example: S: * MAILBOX blurdybloop
+
+
+
+
+
+
+
+
+
+Crispin Informational [Page 5]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+7.3.OBS.1. COPY Response
+
+ Data: none
+
+ The COPY response MUST NOT be transmitted by new server
+ implementations. Client implementations MUST ignore the COPY
+ response. It is documented here for the benefit of client
+ implementors who may encounter this response from old server
+ implementations.
+
+ In some experimental versions of this protocol, this response was
+ returned in response to a COPY command to indicate on a
+ per-message basis that the message was copied successfully.
+
+ Example: S: * 44 COPY
+
+7.3.OBS.2. STORE Response
+
+ Data: message data
+
+ The STORE response MUST NOT be transmitted by new server
+ implementations. Client implementations MUST treat the STORE
+ response as equivalent to the FETCH response. It is documented
+ here for the benefit of client implementors who may encounter this
+ response from old server implementations.
+
+ In some experimental versions of this protocol, this response was
+ returned instead of FETCH in response to a STORE command to report
+ the new value of the flags.
+
+ Example: S: * 69 STORE (FLAGS (\Deleted))
+
+Formal Syntax of Obsolete Commands and Responses
+
+ Each obsolete syntax rule that is suffixed with "_old" is added to
+ the corresponding name in the formal syntax. For example,
+ command_auth_old adds the FIND command to command_auth.
+
+ command_auth_old ::= find
+
+ command_select_old
+ ::= partial
+
+ date_year_old ::= 2digit
+ ;; (year - 1900)
+
+ date_time_old ::= <"> date_day_fixed "-" date_month "-" date_year
+ SPACE time "-" zone_name <">
+
+
+
+Crispin Informational [Page 6]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+ find ::= "FIND" SPACE ["ALL."] "MAILBOXES" SPACE
+ list_mailbox
+
+ fetch_att_old ::= "RFC822.HEADER.LINES" [".NOT"] SPACE header_list /
+ fetch_text_old
+
+ fetch_text_old ::= "BODY" [".PEEK"] section_old /
+ "RFC822" [".HEADER" / ".TEXT" [".PEEK"]]
+
+ msg_data_old ::= "COPY" / ("STORE" SPACE msg_att)
+
+ partial ::= "PARTIAL" SPACE nz_number SPACE fetch_text_old SPACE
+ number SPACE number
+
+ section_old ::= "[" (number ["." number]) "]"
+
+ subscribe_old ::= "SUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
+
+ unsubscribe_old ::= "UNSUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
+
+ zone_name ::= "UT" / "GMT" / "Z" / ;; +0000
+ "AST" / "EDT" / ;; -0400
+ "EST" / "CDT" / ;; -0500
+ "CST" / "MDT" / ;; -0600
+ "MST" / "PDT" / ;; -0700
+ "PST" / "YDT" / ;; -0800
+ "YST" / "HDT" / ;; -0900
+ "HST" / "BDT" / ;; -1000
+ "BST" / ;; -1100
+ "A" / "B" / "C" / "D" / "E" / "F" / ;; +1 to +6
+ "G" / "H" / "I" / "K" / "L" / "M" / ;; +7 to +12
+ "N" / "O" / "P" / "Q" / "R" / "S" / ;; -1 to -6
+ "T" / "U" / "V" / "W" / "X" / "Y" ;; -7 to -12
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Informational [Page 7]
+
+RFC 2062 IMAP4 Obsolete December 1996
+
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Aveneue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Informational [Page 8]
+
diff --git a/imap/docs/rfc/rfc2087.txt b/imap/docs/rfc/rfc2087.txt
new file mode 100644
index 00000000..1db5b57b
--- /dev/null
+++ b/imap/docs/rfc/rfc2087.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group J. Myers
+Request for Comments: 2087 Carnegie Mellon
+Category: Standards Track January 1997
+
+
+ IMAP4 QUOTA extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+1. Abstract
+
+ The QUOTA extension of the Internet Message Access Protocol [IMAP4]
+ permits administrative limits on resource usage (quotas) to be
+ manipulated through the IMAP protocol.
+
+Table of Contents
+
+ 1. Abstract........................................... 1
+ 2. Conventions Used in this Document.................. 1
+ 3. Introduction and Overview.......................... 2
+ 4. Commands........................................... 2
+ 4.1. SETQUOTA Command................................... 2
+ 4.2. GETQUOTA Command................................... 2
+ 4.3. GETQUOTAROOT Command............................... 3
+ 5. Responses.......................................... 3
+ 5.1. QUOTA Response..................................... 3
+ 5.2. QUOTAROOT Response................................. 4
+ 6. Formal syntax...................................... 4
+ 7. References......................................... 5
+ 8. Security Considerations............................ 5
+ 9. Author's Address................................... 5
+
+
+2. Conventions Used in this Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+
+
+
+
+
+
+
+Myers Standards Track [Page 1]
+
+RFC 2087 QUOTA January 1997
+
+
+3. Introduction and Overview
+
+ The QUOTA extension is present in any IMAP4 implementation which
+ returns "QUOTA" as one of the supported capabilities to the
+ CAPABILITY command.
+
+ An IMAP4 server which supports the QUOTA capability may support
+ limits on any number of resources. Each resource has an atom name
+ and an implementation-defined interpretation which evaluates to an
+ integer. Examples of such resources are:
+
+ Name Interpretation
+
+ STORAGE Sum of messages' RFC822.SIZE, in units of 1024 octets
+ MESSAGE Number of messages
+
+
+ Each mailbox has zero or more implementation-defined named "quota
+ roots". Each quota root has zero or more resource limits. All
+ mailboxes that share the same named quota root share the resource
+ limits of the quota root.
+
+ Quota root names do not necessarily have to match the names of
+ existing mailboxes.
+
+4. Commands
+
+4.1. SETQUOTA Command
+
+ Arguments: quota root
+ list of resource limits
+
+ Data: untagged responses: QUOTA
+
+ Result: OK - setquota completed
+ NO - setquota error: can't set that data
+ BAD - command unknown or arguments invalid
+
+ The SETQUOTA command takes the name of a mailbox quota root and a
+ list of resource limits. The resource limits for the named quota root
+ are changed to be the specified limits. Any previous resource limits
+ for the named quota root are discarded.
+
+ If the named quota root did not previously exist, an implementation
+ may optionally create it and change the quota roots for any number of
+ existing mailboxes in an implementation-defined manner.
+
+
+
+
+
+Myers Standards Track [Page 2]
+
+RFC 2087 QUOTA January 1997
+
+
+ Example: C: A001 SETQUOTA "" (STORAGE 512)
+ S: * QUOTA "" (STORAGE 10 512)
+ S: A001 OK Setquota completed
+
+4.2. GETQUOTA Command
+
+ Arguments: quota root
+
+ Data: untagged responses: QUOTA
+
+ Result: OK - getquota completed
+ NO - getquota error: no such quota root, permission
+ denied
+ BAD - command unknown or arguments invalid
+
+ The GETQUOTA command takes the name of a quota root and returns the
+ quota root's resource usage and limits in an untagged QUOTA response.
+
+ Example: C: A003 GETQUOTA ""
+ S: * QUOTA "" (STORAGE 10 512)
+ S: A003 OK Getquota completed
+
+4.3. GETQUOTAROOT Command
+
+ Arguments: mailbox name
+
+ Data: untagged responses: QUOTAROOT, QUOTA
+
+ Result: OK - getquota completed
+ NO - getquota error: no such mailbox, permission denied
+ BAD - command unknown or arguments invalid
+
+ The GETQUOTAROOT command takes the name of a mailbox and returns the
+ list of quota roots for the mailbox in an untagged QUOTAROOT
+ response. For each listed quota root, it also returns the quota
+ root's resource usage and limits in an untagged QUOTA response.
+
+ Example: C: A003 GETQUOTAROOT INBOX
+ S: * QUOTAROOT INBOX ""
+ S: * QUOTA "" (STORAGE 10 512)
+ S: A003 OK Getquota completed
+
+
+
+
+
+
+
+
+
+
+Myers Standards Track [Page 3]
+
+RFC 2087 QUOTA January 1997
+
+
+5. Responses
+
+5.1. QUOTA Response
+
+ Data: quota root name
+ list of resource names, usages, and limits
+
+ This response occurs as a result of a GETQUOTA or GETQUOTAROOT
+ command. The first string is the name of the quota root for which
+ this quota applies.
+
+ The name is followed by a S-expression format list of the resource
+ usage and limits of the quota root. The list contains zero or
+ more triplets. Each triplet conatins a resource name, the current
+ usage of the resource, and the resource limit.
+
+ Resources not named in the list are not limited in the quota root.
+ Thus, an empty list means there are no administrative resource
+ limits in the quota root.
+
+ Example: S: * QUOTA "" (STORAGE 10 512)
+
+5.2. QUOTAROOT Response
+
+ Data: mailbox name
+ zero or more quota root names
+
+ This response occurs as a result of a GETQUOTAROOT command. The
+ first string is the mailbox and the remaining strings are the
+ names of the quota roots for the mailbox.
+
+ Example: S: * QUOTAROOT INBOX ""
+ S: * QUOTAROOT comp.mail.mime
+
+6. Formal syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) notation as specified in RFC 822 with one exception; the
+ delimiter used with the "#" construct is a single space (SP) and not
+ one or more commas.
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+
+
+
+
+
+Myers Standards Track [Page 4]
+
+RFC 2087 QUOTA January 1997
+
+
+ getquota ::= "GETQUOTA" SP astring
+
+ getquotaroot ::= "GETQUOTAROOT" SP astring
+
+ quota_list ::= "(" #quota_resource ")"
+
+ quota_resource ::= atom SP number SP number
+
+ quota_response ::= "QUOTA" SP astring SP quota_list
+
+ quotaroot_response
+ ::= "QUOTAROOT" SP astring *(SP astring)
+
+ setquota ::= "SETQUOTA" SP astring SP setquota_list
+
+ setquota_list ::= "(" 0#setquota_resource ")"
+
+ setquota_resource ::= atom SP number
+
+7. References
+
+ [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
+ RFC 1730, University of Washington, December 1994.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822.
+
+8. Security Considerations
+
+ Implementors should be careful to make sure the implementation of
+ these commands does not violate the site's security policy. The
+ resource usage of other users is likely to be considered confidential
+ information and should not be divulged to unauthorized persons.
+
+9. Author's Address
+
+ John G. Myers
+ Carnegie-Mellon University
+ 5000 Forbes Ave.
+ Pittsburgh PA, 15213-3890
+
+ EMail: jgm+@cmu.edu
+
+
+
+
+
+
+
+
+
+Myers Standards Track [Page 5]
+
diff --git a/imap/docs/rfc/rfc2088.txt b/imap/docs/rfc/rfc2088.txt
new file mode 100644
index 00000000..f36cc764
--- /dev/null
+++ b/imap/docs/rfc/rfc2088.txt
@@ -0,0 +1,115 @@
+
+
+
+
+
+
+Network Working Group J. Myers
+Request for Comments: 2088 Carnegie Mellon
+Cateogry: Standards Track January 1997
+
+
+ IMAP4 non-synchronizing literals
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+1. Abstract
+
+ The Internet Message Access Protocol [IMAP4] contains the "literal"
+ syntactic construct for communicating strings. When sending a
+ literal from client to server, IMAP4 requires the client to wait for
+ the server to send a command continuation request between sending the
+ octet count and the string data. This document specifies an
+ alternate form of literal which does not require this network round
+ trip.
+
+2. Conventions Used in this Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+3. Specification
+
+ The non-synchronizing literal is added an alternate form of literal,
+ and may appear in communication from client to server instead of the
+ IMAP4 form of literal. The IMAP4 form of literal, used in
+ communication from client to server, is referred to as a
+ synchronizing literal.
+
+ Non-synchronizing literals may be used with any IMAP4 server
+ implementation which returns "LITERAL+" as one of the supported
+ capabilities to the CAPABILITY command. If the server does not
+ advertise the LITERAL+ capability, the client must use synchronizing
+ literals instead.
+
+ The non-synchronizing literal is distinguished from the original
+ synchronizing literal by having a plus ('+') between the octet count
+ and the closing brace ('}'). The server does not generate a command
+ continuation request in response to a non-synchronizing literal, and
+
+
+
+Myers Standards Track [Page 1]
+
+RFC 2088 LITERAL January 1997
+
+
+ clients are not required to wait before sending the octets of a non-
+ synchronizing literal.
+
+ The protocol receiver of an IMAP4 server must check the end of every
+ received line for an open brace ('{') followed by an octet count, a
+ plus ('+'), and a close brace ('}') immediately preceeding the CRLF.
+ If it finds this sequence, it is the octet count of a non-
+ synchronizing literal and the server MUST treat the specified number
+ of following octets and the following line as part of the same
+ command. A server MAY still process commands and reject errors on a
+ line-by-line basis, as long as it checks for non-synchronizing
+ literals at the end of each line.
+
+ Example: C: A001 LOGIN {11+}
+ C: FRED FOOBAR {7+}
+ C: fat man
+ S: A001 OK LOGIN completed
+
+4. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
+ Non-terminals referenced but not defined below are as defined by
+ [IMAP4].
+
+ literal ::= "{" number ["+"] "}" CRLF *CHAR8
+ ;; Number represents the number of CHAR8 octets
+
+6. References
+
+ [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
+ draft-crispin-imap-base-XX.txt, University of Washington, April 1996.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
+ Messages", STD 11, RFC 822.
+
+7. Security Considerations
+
+ There are no known security issues with this extension.
+
+8. Author's Address
+
+ John G. Myers
+ Carnegie-Mellon University
+ 5000 Forbes Ave.
+ Pittsburgh PA, 15213-3890
+
+ Email: jgm+@cmu.edu
+
+
+
+Myers Standards Track [Page 2]
+
diff --git a/imap/docs/rfc/rfc2177.txt b/imap/docs/rfc/rfc2177.txt
new file mode 100644
index 00000000..c11c7654
--- /dev/null
+++ b/imap/docs/rfc/rfc2177.txt
@@ -0,0 +1,227 @@
+
+
+
+
+
+
+Network Working Group B. Leiba
+Request for Comments: 2177 IBM T.J. Watson Research Center
+Category: Standards Track June 1997
+
+
+ IMAP4 IDLE command
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+1. Abstract
+
+ The Internet Message Access Protocol [IMAP4] requires a client to
+ poll the server for changes to the selected mailbox (new mail,
+ deletions). It's often more desirable to have the server transmit
+ updates to the client in real time. This allows a user to see new
+ mail immediately. It also helps some real-time applications based on
+ IMAP, which might otherwise need to poll extremely often (such as
+ every few seconds). (While the spec actually does allow a server to
+ push EXISTS responses aysynchronously, a client can't expect this
+ behaviour and must poll.)
+
+ This document specifies the syntax of an IDLE command, which will
+ allow a client to tell the server that it's ready to accept such
+ real-time updates.
+
+2. Conventions Used in this Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as described in RFC 2060
+ [IMAP4].
+
+3. Specification
+
+ IDLE Command
+
+ Arguments: none
+
+ Responses: continuation data will be requested; the client sends
+ the continuation data "DONE" to end the command
+
+
+
+Leiba Standards Track [Page 1]
+
+RFC 2177 IMAP4 IDLE command June 1997
+
+
+
+ Result: OK - IDLE completed after client sent "DONE"
+ NO - failure: the server will not allow the IDLE
+ command at this time
+ BAD - command unknown or arguments invalid
+
+ The IDLE command may be used with any IMAP4 server implementation
+ that returns "IDLE" as one of the supported capabilities to the
+ CAPABILITY command. If the server does not advertise the IDLE
+ capability, the client MUST NOT use the IDLE command and must poll
+ for mailbox updates. In particular, the client MUST continue to be
+ able to accept unsolicited untagged responses to ANY command, as
+ specified in the base IMAP specification.
+
+ The IDLE command is sent from the client to the server when the
+ client is ready to accept unsolicited mailbox update messages. The
+ server requests a response to the IDLE command using the continuation
+ ("+") response. The IDLE command remains active until the client
+ responds to the continuation, and as long as an IDLE command is
+ active, the server is now free to send untagged EXISTS, EXPUNGE, and
+ other messages at any time.
+
+ The IDLE command is terminated by the receipt of a "DONE"
+ continuation from the client; such response satisfies the server's
+ continuation request. At that point, the server MAY send any
+ remaining queued untagged responses and then MUST immediately send
+ the tagged response to the IDLE command and prepare to process other
+ commands. As in the base specification, the processing of any new
+ command may cause the sending of unsolicited untagged responses,
+ subject to the ambiguity limitations. The client MUST NOT send a
+ command while the server is waiting for the DONE, since the server
+ will not be able to distinguish a command from a continuation.
+
+ The server MAY consider a client inactive if it has an IDLE command
+ running, and if such a server has an inactivity timeout it MAY log
+ the client off implicitly at the end of its timeout period. Because
+ of that, clients using IDLE are advised to terminate the IDLE and
+ re-issue it at least every 29 minutes to avoid being logged off.
+ This still allows a client to receive immediate mailbox updates even
+ though it need only "poll" at half hour intervals.
+
+
+
+
+
+
+
+
+
+
+
+Leiba Standards Track [Page 2]
+
+RFC 2177 IMAP4 IDLE command June 1997
+
+
+ Example: C: A001 SELECT INBOX
+ S: * FLAGS (Deleted Seen)
+ S: * 3 EXISTS
+ S: * 0 RECENT
+ S: * OK [UIDVALIDITY 1]
+ S: A001 OK SELECT completed
+ C: A002 IDLE
+ S: + idling
+ ...time passes; new mail arrives...
+ S: * 4 EXISTS
+ C: DONE
+ S: A002 OK IDLE terminated
+ ...another client expunges message 2 now...
+ C: A003 FETCH 4 ALL
+ S: * 4 FETCH (...)
+ S: A003 OK FETCH completed
+ C: A004 IDLE
+ S: * 2 EXPUNGE
+ S: * 3 EXISTS
+ S: + idling
+ ...time passes; another client expunges message 3...
+ S: * 3 EXPUNGE
+ S: * 2 EXISTS
+ ...time passes; new mail arrives...
+ S: * 3 EXISTS
+ C: DONE
+ S: A004 OK IDLE terminated
+ C: A005 FETCH 3 ALL
+ S: * 3 FETCH (...)
+ S: A005 OK FETCH completed
+ C: A006 IDLE
+
+4. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
+ Non-terminals referenced but not defined below are as defined by
+ [IMAP4].
+
+ command_auth ::= append / create / delete / examine / list / lsub /
+ rename / select / status / subscribe / unsubscribe
+ / idle
+ ;; Valid only in Authenticated or Selected state
+
+ idle ::= "IDLE" CRLF "DONE"
+
+
+
+
+
+
+Leiba Standards Track [Page 3]
+
+RFC 2177 IMAP4 IDLE command June 1997
+
+
+5. References
+
+ [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+6. Security Considerations
+
+ There are no known security issues with this extension.
+
+7. Author's Address
+
+ Barry Leiba
+ IBM T.J. Watson Research Center
+ 30 Saw Mill River Road
+ Hawthorne, NY 10532
+
+ Email: leiba@watson.ibm.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Leiba Standards Track [Page 4]
+
diff --git a/imap/docs/rfc/rfc2180.txt b/imap/docs/rfc/rfc2180.txt
new file mode 100644
index 00000000..57607002
--- /dev/null
+++ b/imap/docs/rfc/rfc2180.txt
@@ -0,0 +1,787 @@
+
+
+
+
+
+
+Network Working Group M. Gahrns
+Request for Comments: 2180 Microsoft
+Category: Informational July 1997
+
+
+ IMAP4 Multi-Accessed Mailbox Practice
+
+Status of this Memo
+
+ This memo provides information for the Internet community. This memo
+ does not specify an Internet standard of any kind. Distribution of
+ this memo is unlimited.
+
+1. Abstract
+
+ IMAP4[RFC-2060] is rich client/server protocol that allows a client
+ to access and manipulate electronic mail messages on a server.
+ Within the protocol framework, it is possible to have differing
+ results for particular client/server interactions. If a protocol does
+ not allow for this, it is often unduly restrictive.
+
+ For example, when multiple clients are accessing a mailbox and one
+ attempts to delete the mailbox, an IMAP4 server may choose to
+ implement a solution based upon server architectural constraints or
+ individual preference.
+
+ With this flexibility comes greater client responsibility. It is not
+ sufficient for a client to be written based upon the behavior of a
+ particular IMAP server. Rather the client must be based upon the
+ behavior allowed by the protocol.
+
+ By documenting common IMAP4 server practice for the case of
+ simultaneous client access to a mailbox, we hope to ensure the widest
+ amount of inter-operation between IMAP4 clients and servers.
+
+ The behavior described in this document reflects the practice of some
+ existing servers or behavior that the consensus of the IMAP mailing
+ list has deemed to be reasonable. The behavior described within this
+ document is believed to be [RFC-2060] compliant. However, this
+ document is not meant to define IMAP4 compliance, nor is it an
+ exhaustive list of valid IMAP4 behavior. [RFC-2060] must always be
+ consulted to determine IMAP4 compliance, especially for server
+ behavior not described within this document.
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 1]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+2. Conventions used in this document
+
+ In examples,"C1:", "C2:" and "C3:" indicate lines sent by 3 different
+ clients (client #1, client #2 and client #3) that are connected to a
+ server. "S1:", "S2:" and "S3:" indicated lines sent by the server to
+ client #1, client #2 and client #3 respectively.
+
+ A shared mailbox, is a mailbox that can be used by multiple users.
+
+ A multi-accessed mailbox, is a mailbox that has multiple clients
+ simultaneously accessing it.
+
+ A client is said to have accessed a mailbox after a successful SELECT
+ or EXAMINE command.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+
+3. Deletion/Renaming of a multi-accessed mailbox
+
+ If an external agent or multiple clients are accessing a mailbox,
+ care must be taken when handling the deletion or renaming of the
+ mailbox. Following are some strategies an IMAP server may choose to
+ use when dealing with this situation.
+
+
+3.1. The server MAY fail the DELETE/RENAME command of a multi-accessed
+ mailbox
+
+ In some cases, this behavior may not be practical. For example, if a
+ large number of clients are accessing a shared mailbox, the window in
+ which no clients have the mailbox accessed may be small or non-
+ existent, effectively rendering the mailbox undeletable or
+ unrenamable.
+
+ Example:
+
+ <Client #1 and Client #2 have mailbox FOO accessed. Client #1 tries
+ to DELETE the mailbox and is refused>
+
+ C1: A001 DELETE FOO
+ S1: A001 NO Mailbox FOO is in use by another user.
+
+
+
+
+
+
+
+Gahrns Informational [Page 2]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+3.2. The server MAY allow the DELETE command of a multi-accessed
+ mailbox, but keep the information in the mailbox available for
+ those clients that currently have access to the mailbox.
+
+ When all clients have finished accessing the mailbox, it is
+ permanently removed. For clients that do not already have access to
+ the mailbox, the 'ghosted' mailbox would not be available. For
+ example, it would not be returned to these clients in a subsequent
+ LIST or LSUB command and would not be a valid mailbox argument to any
+ other IMAP command until the reference count of clients accessing the
+ mailbox reached 0.
+
+ In some cases, this behavior may not be desirable. For example if
+ someone created a mailbox with offensive or sensitive information,
+ one might prefer to have the mailbox deleted and all access to the
+ information contained within removed immediately, rather than
+ continuing to allow access until the client closes the mailbox.
+
+ Furthermore, this behavior, may prevent 'recycling' of the same
+ mailbox name until all clients have finished accessing the original
+ mailbox.
+
+ Example:
+
+ <Client #1 and Client #2 have mailbox FOO selected. Client #1 DELETEs
+ mailbox FOO>
+
+ C1: A001 DELETE FOO
+ S1: A001 OK Mailbox FOO is deleted.
+
+ <Client #2 is still able to operate on the deleted mailbox>
+
+ C2: B001 STORE 1 +FLAGS (\Seen)
+ S2: * 1 FETCH FLAGS (\Seen)
+ S2: B001 OK STORE completed
+
+ <Client #3 which did not have access to the mailbox prior to the
+ deletion by client #1 does not have access to the mailbox>
+
+ C3: C001 STATUS FOO (MESSAGES)
+ S3: C001 NO Mailbox does not exist
+
+ <Nor is client #3 able to create a mailbox with the name FOO, while
+ the reference count is non zero>
+
+ C3: C002 CREATE FOO
+ S3: C002 NO Mailbox FOO is still in use. Try again later.
+
+
+
+
+Gahrns Informational [Page 3]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+ <Client #2 closes its access to the mailbox, no other clients have
+ access to the mailbox FOO and reference count becomes 0>
+
+ C2: B002 CLOSE
+ S2: B002 OK CLOSE Completed
+
+ <Now that the reference count on FOO has reached 0, the mailbox name
+ can be recycled>
+
+ C3: C003 CREATE FOO
+ S3: C003 OK CREATE Completed
+
+
+3.3. The server MAY allow the DELETE/RENAME of a multi-accessed
+ mailbox, but disconnect all other clients who have the mailbox
+ accessed by sending a untagged BYE response.
+
+ A server may often choose to disconnect clients in the DELETE case,
+ but may choose to implement a "friendlier" method for the RENAME
+ case.
+
+ Example:
+
+ <Client #1 and Client #2 have mailbox FOO accessed. Client #1 DELETEs
+ the mailbox FOO>
+
+ C1: A002 DELETE FOO
+ S1: A002 OK DELETE completed.
+
+ <Server disconnects all other users of the mailbox>
+ S2: * BYE Mailbox FOO has been deleted.
+
+
+3.4. The server MAY allow the RENAME of a multi-accessed mailbox by
+ simply changing the name attribute on the mailbox.
+
+ Other clients that have access to the mailbox can continue issuing
+ commands such as FETCH that do not reference the mailbox name.
+ Clients would discover the renaming the next time they referred to
+ the old mailbox name. Some servers MAY choose to include the
+ [NEWNAME] response code in their tagged NO response to a command that
+ contained the old mailbox name, as a hint to the client that the
+ operation can succeed if the command is issued with the new mailbox
+ name.
+
+
+
+
+
+
+
+Gahrns Informational [Page 4]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+ Example:
+
+ <Client #1 and Client #2 have mailbox FOO accessed. Client #1 RENAMEs
+ the mailbox.>
+
+ C1: A001 RENAME FOO BAR
+ S1: A001 OK RENAME completed.
+
+ <Client #2 is still able to do operations that do not reference the
+ mailbox name>
+
+ C2: B001 FETCH 2:4 (FLAGS)
+ S2: * 2 FETCH . . .
+ S2: * 3 FETCH . . .
+ S2: * 4 FETCH . . .
+ S2: B001 OK FETCH completed
+
+ <Client #2 is not able to do operations that reference the mailbox
+ name>
+
+ C2: B002 APPEND FOO {300} C2: Date: Mon, 7 Feb 1994
+ 21:52:25 0800 (PST) C2: . . . S2: B002 NO [NEWNAME FOO
+ BAR] Mailbox has been renamed
+
+
+4. Expunging of messages on a multi-accessed mailbox
+
+ If an external agent or multiple clients are accessing a mailbox,
+ care must be taken when handling the EXPUNGE of messages. Other
+ clients accessing the mailbox may be in the midst of issuing a
+ command that depends upon message sequence numbers. Because an
+ EXPUNGE response can not be sent while responding to a FETCH, STORE
+ or SEARCH command, it is not possible to immediately notify the
+ client of the EXPUNGE. This can result in ambiguity if the client
+ issues a FETCH, STORE or SEARCH operation on a message that has been
+ EXPUNGED.
+
+
+4.1. Fetching of expunged messages
+
+ Following are some strategies an IMAP server may choose to use when
+ dealing with a FETCH command on expunged messages.
+
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 5]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+ Consider the following scenario:
+
+ - Client #1 and Client #2 have mailbox FOO selected.
+ - There are 7 messages in the mailbox.
+ - Messages 4:7 are marked for deletion.
+ - Client #1 issues an EXPUNGE, to expunge messages 4:7
+
+
+4.1.1. The server MAY allow the EXPUNGE of a multi-accessed mailbox but
+ keep the messages available to satisfy subsequent FETCH commands
+ until it is able to send an EXPUNGE response to each client.
+
+ In some cases, the behavior of keeping "ghosted" messages may not be
+ desirable. For example if a message contained offensive or sensitive
+ information, one might prefer to instantaneously remove all access to
+ the information, regardless of whether another client is in the midst
+ of accessing it.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 is still able to access the expunged messages because the
+ server has kept a 'ghosted' copy of the messages until it is able to
+ notify client #2 of the EXPUNGE>
+
+ C2: B001 FETCH 4:7 RFC822
+ S2: * 4 FETCH RFC822 . . . (RFC822 info returned)
+ S2: * 5 FETCH RFC822 . . . (RFC822 info returned)
+ S2: * 6 FETCH RFC822 . . . (RFC822 info returned)
+ S2: * 7 FETCH RFC822 . . . (RFC822 info returned)
+ S2: B001 OK FETCH Completed
+
+ <Client #2 issues a command where it can get notified of the EXPUNGE>
+
+ C2: B002 NOOP
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 3 EXISTS
+ S2: B002 OK NOOP Complete
+
+ <Client #2 no longer has access to the expunged messages>
+
+ C2: B003 FETCH 4:7 RFC822
+ S2: B003 NO Messages 4:7 are no longer available.
+
+
+
+
+
+
+Gahrns Informational [Page 6]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+4.1.2 The server MAY allow the EXPUNGE of a multi-accessed mailbox,
+ and on subsequent FETCH commands return FETCH responses only for
+ non-expunged messages and a tagged NO.
+
+ After receiving a tagged NO FETCH response, the client SHOULD issue a
+ NOOP command so that it will be informed of any pending EXPUNGE
+ responses. The client may then either reissue the failed FETCH
+ command, or by examining the EXPUNGE response from the NOOP and the
+ FETCH response from the FETCH, determine that the FETCH failed
+ because of pending expunges.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 attempts to FETCH a mix of expunged and non-expunged
+ messages. A FETCH response is returned only for then non-expunged
+ messages along with a tagged NO>
+
+ C2: B001 FETCH 3:5 ENVELOPE
+ S2: * 3 FETCH ENVELOPE . . . (ENVELOPE info returned)
+ S2: B001 NO Some of the requested messages no longer exist
+
+ <Upon receiving a tagged NO FETCH response, Client #2 issues a NOOP
+ to be informed of any pending EXPUNGE responses>
+
+ C2: B002 NOOP
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 3 EXISTS
+ S2: B002 OK NOOP Completed.
+
+ <By receiving a FETCH response for message 3, and an EXPUNGE response
+ that indicates messages 4:7 have been expunged, the client does not
+ need to re-issue the FETCH>
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 7]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+4.1.3 The server MAY allow the EXPUNGE of a multi-accessed mailbox, and
+ on subsequent FETCH commands return the usual FETCH responses for
+ non-expunged messages, "NIL FETCH Responses" for expunged
+ messages, and a tagged OK response.
+
+ If all of the messages in the subsequent FETCH command have been
+ expunged, the server SHOULD return only a tagged NO. In this case,
+ the client SHOULD issue a NOOP command so that it will be informed of
+ any pending EXPUNGE responses. The client may then either reissue
+ the failed FETCH command, or by examining the EXPUNGE response from
+ the NOOP, determine that the FETCH failed because of pending
+ expunges.
+
+ "NIL FETCH responses" are a representation of empty data as
+ appropriate for the FETCH argument specified.
+
+ Example:
+
+ * 1 FETCH (ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL))
+ * 1 FETCH (FLAGS ())
+ * 1 FETCH (INTERNALDATE "00-Jan-0000 00:00:00 +0000")
+ * 1 FETCH (RFC822 "")
+ * 1 FETCH (RFC822.HEADER "")
+ * 1 FETCH (RFC822.TEXT "")
+ * 1 FETCH (RFC822.SIZE 0)
+ * 1 FETCH (BODY ("TEXT" "PLAIN" NIL NIL NIL "7BIT" 0 0)
+ * 1 FETCH (BODYSTRUCTURE ("TEXT" "PLAIN" NIL NIL NIL "7BIT" 0 0)
+ * 1 FETCH (BODY[<section>] "")
+ * 1 FETCH (BODY[<section>]<partial> "")
+
+ In some cases, a client may not be able to distinguish between "NIL
+ FETCH responses" received because a message was expunged and those
+ received because the data actually was NIL. For example, a * 5
+ FETCH (FLAGS ()) response could be received if no flags were set on
+ message 5, or because message 5 was expunged. In a case of potential
+ ambiguity, the client SHOULD issue a command such as NOOP to force
+ the sending of the EXPUNGE responses to resolve any ambiguity.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 attempts to access a mix of expunged and non-expunged
+ messages. Normal data is returned for non-expunged message, "NIL
+ FETCH responses" are returned for expunged messages>
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 8]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+ C2: B002 FETCH 3:5 ENVELOPE
+ S2: * 3 FETCH ENVELOPE . . . (ENVELOPE info returned)
+ S2: * 4 FETCH ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL
+ NIL NIL)
+ S2: * 5 FETCH ENVELOPE (NIL NIL NIL NIL NIL NIL NIL NIL
+ NIL NIL)
+ S2: B002 OK FETCH Completed
+
+ <Client #2 attempts to FETCH only expunged messages and receives a
+ tagged NO response>
+
+ C2: B002 FETCH 4:7 ENVELOPE
+ S2: B002 NO Messages 4:7 have been expunged.
+
+
+4.1.4 To avoid the situation altogether, the server MAY fail the
+ EXPUNGE of a multi-accessed mailbox
+
+ In some cases, this behavior may not be practical. For example, if a
+ large number of clients are accessing a shared mailbox, the window in
+ which no clients have the mailbox accessed may be small or non-
+ existent, effectively rendering the message unexpungeable.
+
+
+4.2. Storing of expunged messages
+
+ Following are some strategies an IMAP server may choose to use when
+ dealing with a STORE command on expunged messages.
+
+
+4.2.1 If the ".SILENT" suffix is used, and the STORE completed
+ successfully for all the non-expunged messages, the server SHOULD
+ return a tagged OK.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 tries to silently STORE flags on expunged and non-
+ expunged messages. The server sets the flags on the non-expunged
+ messages and returns OK>
+
+ C2: B001 STORE 1:7 +FLAGS.SILENT (\SEEN)
+ S2: B001 OK
+
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 9]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+4.2.2. If the ".SILENT" suffix is not used, and only expunged messages
+ are referenced, the server SHOULD return only a tagged NO.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 tries to STORE flags only on expunged messages>
+
+ C2: B001 STORE 5:7 +FLAGS (\SEEN)
+ S2: B001 NO Messages have been expunged
+
+
+4.2.3. If the ".SILENT" suffix is not used, and a mixture of expunged
+ and non-expunged messages are referenced, the server MAY set the
+ flags and return a FETCH response for the non-expunged messages
+ along with a tagged NO.
+
+ After receiving a tagged NO STORE response, the client SHOULD issue a
+ NOOP command so that it will be informed of any pending EXPUNGE
+ responses. The client may then either reissue the failed STORE
+ command, or by examining the EXPUNGE responses from the NOOP and
+ FETCH responses from the STORE, determine that the STORE failed
+ because of pending expunges.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 tries to STORE flags on a mixture of expunged and non-
+ expunged messages>
+
+ C2: B001 STORE 1:7 +FLAGS (\SEEN)
+ S2: * FETCH 1 FLAGS (\SEEN)
+ S2: * FETCH 2 FLAGS (\SEEN)
+ S2: * FETCH 3 FLAGS (\SEEN)
+ S2: B001 NO Some of the messages no longer exist.
+
+ C2: B002 NOOP
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 3 EXISTS
+ S2: B002 OK NOOP Completed.
+
+ <By receiving FETCH responses for messages 1:3, and an EXPUNGE
+ response that indicates messages 4:7 have been expunged, the client
+ does not need to re-issue the STORE>
+
+
+
+
+
+
+Gahrns Informational [Page 10]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+4.2.4. If the ".SILENT" suffix is not used, and a mixture of expunged
+ and non-expunged messages are referenced, the server MAY return
+ an untagged NO and not set any flags.
+
+ After receiving a tagged NO STORE response, the client SHOULD issue a
+ NOOP command so that it will be informed of any pending EXPUNGE
+ responses. The client would then re-issue the STORE command after
+ updating its message list per any EXPUNGE response.
+
+ If a large number of clients are accessing a shared mailbox, the
+ window in which there are no pending expunges may be small or non-
+ existent, effectively disallowing a client from setting the flags on
+ all messages at once.
+
+ Example: (Building upon the scenario outlined in 4.1.)
+
+ <Client #2 tries to STORE flags on a mixture of expunged and non-
+ expunged messages>
+
+ C2: B001 STORE 1:7 +FLAGS (\SEEN)
+ S2: B001 NO Some of the messages no longer exist.
+
+ <Client #2 issues a NOOP to be informed of the EXPUNGED messages>
+
+ C2: B002 NOOP
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 4 EXPUNGE
+ S2: * 3 EXISTS
+ S2: B002 OK NOOP Completed.
+
+ <Client #2 updates its message list and re-issues the STORE on only
+ those messages that have not been expunged>
+
+ C2: B003 STORE 1:3 +FLAGS (\SEEN) S2: * FETCH 1 FLAGS
+ (\SEEN) S2: * FETCH 2 FLAGS (\SEEN) S2: * FETCH 3 FLAGS
+ (\SEEN) S2: B003 OK STORE Completed
+
+
+4.3. Searching of expunged messages
+
+ A server MAY simply not return a search response for messages that
+ have been expunged and it has not been able to inform the client
+ about. If a client was expecting a particular message to be returned
+ in a search result, and it was not, the client SHOULD issue a NOOP
+ command to see if the message was expunged by another client.
+
+
+
+
+Gahrns Informational [Page 11]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+4.4 Copying of expunged messages
+
+ COPY is the only IMAP4 sequence number command that is safe to allow
+ an EXPUNGE response on. This is because a client is not permitted to
+ cascade several COPY commands together. A client is required to wait
+ and confirm that the copy worked before issuing another one.
+
+4.4.1 The server MAY disallow the COPY of messages in a multi-access
+ mailbox that contains expunged messages.
+
+ Pending EXPUNGE response(s) MUST be returned to the COPY command.
+
+ Example:
+
+ C: A001 COPY 2,4,6,8 FRED
+ S: * 4 EXPUNGE
+ S: A001 NO COPY rejected, because some of the requested
+ messages were expunged
+
+ Note: Non of the above messages are copied because if a COPY command
+ is unsuccessful, the server MUST restore the destination mailbox to
+ its state before the COPY attempt.
+
+
+4.4.2 The server MAY allow the COPY of messages in a multi-access
+ mailbox that contains expunged messages.
+
+ Pending EXPUNGE response(s) MUST be returned to the COPY command.
+ Messages that are copied are messages corresponding to sequence
+ numbers before any EXPUNGE response.
+
+ Example:
+
+ C: A001 COPY 2,4,6,8 FRED
+ S: * 3 EXPUNGE
+ S: A001 OK COPY completed
+
+ In the above example, the messages that are copied to FRED are
+ messages 2,4,6,8 at the start of the COPY command. These are
+ equivalent to messages 2,3,5,7 at the end of the COPY command. The
+ EXPUNGE response can't take place until after the messages from the
+ COPY command are identified (because of the "no expunge while no
+ commands in progress" rule).
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 12]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+ Example:
+
+ C: A001 COPY 2,4,6,8 FRED
+ S: * 4 EXPUNGE
+ S: A001 OK COPY completed
+
+ In the above example, message 4 was copied before it was expunged,
+ and MUST appear in the destination mailbox FRED.
+
+
+5. Security Considerations
+
+ This document describes behavior of servers that use the IMAP4
+ protocol, and as such, has the same security considerations as
+ described in [RFC-2060].
+
+ In particular, some described server behavior does not allow for the
+ immediate deletion of information when a mailbox is accessed by
+ multiple clients. This may be a consideration when dealing with
+ sensitive information where immediate deletion would be preferred.
+
+
+6. References
+
+ [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, University of Washington, December 1996.
+
+ [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, Harvard University, March 1997.
+
+
+7. Acknowledgments
+
+ This document is the result of discussions on the IMAP4 mailing list
+ and is meant to reflect consensus of this group. In particular,
+ Raymond Cheng, Mark Crispin, Jim Evans, Erik Forsberg, Steve Hole,
+ Mark Keasling, Barry Leiba, Syd Logan, John Mani, Pat Moran, Larry
+ Osterman, Chris Newman, Bart Schaefer, Vladimir Vulovic, and Jack De
+ Winter were active participants in this discussion or made
+ suggestions to this document.
+
+
+
+
+
+
+
+
+
+
+
+Gahrns Informational [Page 13]
+
+RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
+
+
+8. Author's Address
+
+ Mike Gahrns
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98072
+
+ Phone: (206) 936-9833
+ EMail: mikega@microsoft.com
+
+
+
+
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+Gahrns Informational [Page 14]
+
diff --git a/imap/docs/rfc/rfc2193.txt b/imap/docs/rfc/rfc2193.txt
new file mode 100644
index 00000000..2fec58d7
--- /dev/null
+++ b/imap/docs/rfc/rfc2193.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group M. Gahrns
+Request for Comments: 2193 Microsoft
+Category: Standards Track September 1997
+
+
+ IMAP4 Mailbox Referrals
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+1. Abstract
+
+ When dealing with large amounts of users, messages and geographically
+ dispersed IMAP4 [RFC-2060] servers, it is often desirable to
+ distribute messages amongst different servers within an organization.
+ For example an administrator may choose to store user's personal
+ mailboxes on a local IMAP4 server, while storing shared mailboxes
+ remotely on another server. This type of configuration is common
+ when it is uneconomical to store all data centrally due to limited
+ bandwidth or disk resources.
+
+ Mailbox referrals allow clients to seamlessly access mailboxes that
+ are distributed across several IMAP4 servers.
+
+ A referral mechanism can provide efficiencies over the alternative
+ "proxy method", in which the local IMAP4 server contacts the remote
+ server on behalf of the client, and then transfers the data from the
+ remote server to itself, and then on to the client. The referral
+ mechanism's direct client connection to the remote server is often a
+ more efficient use of bandwidth, and does not require the local
+ server to impersonate the client when authenticating to the remote
+ server.
+
+2. Conventions used in this document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ A home server, is an IMAP4 server that contains the user's inbox.
+
+ A remote mailbox is a mailbox that is not hosted on the user's home
+ server.
+
+
+
+
+Gahrns Standards Track [Page 1]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ A remote server is a server that contains remote mailboxes.
+
+ A shared mailbox, is a mailbox that multiple users have access to.
+
+ An IMAP mailbox referral is when the server directs the client to
+ another IMAP mailbox.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+ IMAP4 servers that support this extension MUST list the keyword
+ MAILBOX-REFERRALS in their CAPABILITY response. No client action is
+ needed to invoke the MAILBOX-REFERRALS capability in a server.
+
+ A MAILBOX-REFERRALS capable IMAP4 server MUST NOT return referrals
+ that result in a referrals loop.
+
+ A referral response consists of a tagged NO response and a REFERRAL
+ response code. The REFERRAL response code MUST contain as an
+ argument a one or more valid URLs separated by a space as defined in
+ [RFC-1738]. If a server replies with multiple URLs for a particular
+ object, they MUST all be of the same type. In this case, the URL MUST
+ be an IMAP URL as defined in [RFC-2192]. A client that supports the
+ REFERRALS extension MUST be prepared for a URL of any type, but it
+ need only be able to process IMAP URLs.
+
+ A server MAY respond with multiple IMAP mailbox referrals if there is
+ more than one replica of the mailbox. This allows the implementation
+ of a load balancing or failover scheme. How a server keeps multiple
+ replicas of a mailbox in sync is not addressed by this document.
+
+ If the server has a preferred order in which the client should
+ attempt to access the URLs, the preferred URL SHOULD be listed in the
+ first, with the remaining URLs presented in descending order of
+ preference. If multiple referrals are given for a mailbox, a server
+ should be aware that there are synchronization issues for a client if
+ the UIDVALIDITY of the referred mailboxes are different.
+
+ An IMAP mailbox referral may be given in response to an IMAP command
+ that specifies a mailbox as an argument.
+
+
+
+
+
+
+
+
+Gahrns Standards Track [Page 2]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ Example:
+
+ A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/REMOTE]Remote Mailbox
+
+ NOTE: user;AUTH=* is specified as required by [RFC-2192] to avoid a
+ client falling back to anonymous login.
+
+ Remote mailboxes and their inferiors, that are accessible only via
+ referrals SHOULD NOT appear in LIST and LSUB responses issued against
+ the user's home server. They MUST appear in RLIST and RLSUB
+ responses issued against the user's home server. Hierarchy referrals,
+ in which a client would be required to connect to the remote server
+ to issue a LIST to discover the inferiors of a mailbox are not
+ addressed in this document.
+
+ For example, if shared mailboxes were only accessible via referrals
+ on a remote server, a RLIST "" "#SHARED/%" command would return the
+ same response if issued against the user's home server or the remote
+ server.
+
+ Note: Mailboxes that are available on the user's home server do not
+ need to be available on the remote server. In addition, there may be
+ additional mailboxes available on the remote server, but they will
+ not accessible to the client via referrals unless they appear in the
+ LIST response to the RLIST command against the user's home server.
+
+ A MAILBOX-REFERRALS capable client will issue the RLIST and RLSUB
+ commands in lieu of LIST and LSUB. The RLIST and RLSUB commands
+ behave identically to their LIST and LSUB counterparts, except remote
+ mailboxes are returned in addition to local mailboxes in the LIST and
+ LSUB responses. This avoids displaying to a non MAILBOX-REFERRALS
+ enabled client inaccessible remote mailboxes.
+
+4.1. SELECT, EXAMINE, DELETE, SUBSCRIBE, UNSUBSCRIBE, STATUS and APPEND
+ Referrals
+
+ An IMAP4 server MAY respond to the SELECT, EXAMINE, DELETE,
+ SUBSCRIBE, UNSUBSCRIBE, STATUS or APPEND command with one or more
+ IMAP mailbox referrals to indicate to the client that the mailbox is
+ hosted on a remote server.
+
+ When a client processes an IMAP mailbox referral, it will open a new
+ connection or use an existing connection to the remote server so that
+ it is able to issue the commands necessary to process the remote
+ mailbox.
+
+
+
+
+
+
+Gahrns Standards Track [Page 3]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ Example: <IMAP4 connection to home server>
+
+ C: A001 DELETE "SHARED/FOO"
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+ Remote mailbox. Try SERVER2.
+
+ <Client established a second connection to SERVER2 and
+ issues the DELETE command on the referred mailbox>
+
+ S: * OK IMAP4rev1 server ready
+ C: B001 AUTHENTICATE KERBEROS_V4
+ <authentication exchange>
+ S: B001 OK user is authenticated
+
+ C: B002 DELETE "SHARED/FOO"
+ S: B002 OK DELETE completed
+
+ Example: <IMAP4 connection to home server>
+
+ C: A001 SELECT REMOTE
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/REMOTE
+ IMAP://user;AUTH=*@SERVER3/REMOTE] Remote mailbox.
+ Try SERVER2 or SERVER3.
+
+ <Client opens second connection to remote server, and
+ issues the commands needed to process the items in the
+ remote mailbox>
+
+ S: * OK IMAP4rev1 server ready
+ C: B001 AUTHENTICATE KERBEROS_V4
+ <authentication exchange>
+ S: B001 OK user is authenticated
+
+ C: B002 SELECT REMOTE
+ S: * 12 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 10] Message 10 is first unseen
+ S: * OK [UIDVALIDITY 123456789]
+ S: * FLAGS (Answered Flagged Deleted Seen Draft)
+ S: * OK [PERMANENTFLAGS (Answered Deleted Seen ]
+ S: B002 OK [READ-WRITE] Selected completed
+
+ C: B003 FETCH 10:12 RFC822
+ S: * 10 FETCH . . .
+ S: * 11 FETCH . . .
+ S: * 12 FETCH . . .
+ S: B003 OK FETCH Completed
+
+
+
+
+Gahrns Standards Track [Page 4]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ <Client is finished processing the REMOTE mailbox and
+ wants to process a mailbox on its home server>
+
+ C: B004 LOGOUT
+ S: * BYE IMAP4rev1 server logging out
+ S: B004 OK LOGOUT Completed
+
+ <Client continues with first connection>
+
+ C: A002 SELECT INBOX
+ S: * 16 EXISTS
+ S: * 2 RECENT
+ S: * OK [UNSEEN 10] Message 10 is first unseen
+ S: * OK [UIDVALIDITY 123456789]
+ S: * FLAGS (Answered Flagged Deleted Seen Draft)
+ S: * OK [PERMANENTFLAGS (Answered Deleted Seen ]
+ S: A002 OK [READ-WRITE] Selected completed
+
+4.2. CREATE Referrals
+
+ An IMAP4 server MAY respond to the CREATE command with one or more
+ IMAP mailbox referrals, if it wishes to direct the client to issue
+ the CREATE against another server. The server can employ any means,
+ such as examining the hierarchy of the specified mailbox name, in
+ determining which server the mailbox should be created on.
+
+ Example:
+
+ C: A001 CREATE "SHARED/FOO"
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+ Mailbox should be created on remote server
+
+ Alternatively, because a home server is required to maintain a
+ listing of referred remote mailboxes, a server MAY allow the creation
+ of a mailbox that will ultimately reside on a remote server against
+ the home server, and provide referrals on subsequent commands that
+ manipulate the mailbox.
+
+ Example:
+
+ C: A001 CREATE "SHARED/FOO"
+ S: A001 OK CREATE succeeded
+
+ C: A002 SELECT "SHARED/FOO"
+ S: A002 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
+ Remote mailbox. Try SERVER2
+
+
+
+
+
+Gahrns Standards Track [Page 5]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+4.3. RENAME Referrals
+
+ An IMAP4 server MAY respond to the RENAME command with one or more
+ pairs of IMAP mailbox referrals. In each pair of IMAP mailbox
+ referrals, the first one is an URL to the existing mailbox name and
+ the second is an URL to the requested new mailbox name.
+
+ If within an IMAP mailbox referral pair, the existing and new mailbox
+ URLs are on different servers, the remote servers are unable to
+ perform the RENAME operation. To achieve the same behavior of
+ server RENAME, the client MAY issue the constituent CREATE, FETCH,
+ APPEND, and DELETE commands against both servers.
+
+ If within an IMAP mailbox referral pair, the existing and new mailbox
+ URLs are on the same server it is an indication that the currently
+ connected server is unable to perform the operation. The client can
+ simply re-issue the RENAME command on the remote server.
+
+ Example:
+
+ C: A001 RENAME FOO BAR
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER1/FOO
+ IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
+ across servers
+
+ Since the existing and new mailbox names are on different servers,
+ the client would be required to make a connection to both servers and
+ issue the constituent commands require to achieve the RENAME.
+
+ Example:
+
+ C: A001 RENAME FOO BAR
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/FOO
+ IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
+ located on SERVER2
+
+ Since both the existing and new mailbox are on the same remote
+ server, the client can simply make a connection to the remote server
+ and re-issue the RENAME command.
+
+4.4. COPY Referrals
+
+ An IMAP4 server MAY respond to the COPY command with one or more IMAP
+ mailbox referrals. This indicates that the destination mailbox is on
+ a remote server. To achieve the same behavior of a server COPY, the
+ client MAY issue the constituent FETCH and APPEND commands against
+ both servers.
+
+
+
+
+Gahrns Standards Track [Page 6]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ Example:
+
+ C: A001 COPY 1 "SHARED/STUFF"
+ S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/STUFF]
+ Unable to copy message(s) to SERVER2.
+
+5.1 RLIST command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LIST
+
+ Result: OK - RLIST Completed
+ NO - RLIST Failure
+ BAD - command unknown or arguments invalid
+
+ The RLIST command behaves identically to its LIST counterpart, except
+ remote mailboxes are returned in addition to local mailboxes in the
+ LIST responses.
+
+5.2 RLSUB Command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LSUB
+
+ Result: OK - RLSUB Completed
+ NO - RLSUB Failure
+ BAD - command unknown or arguments invalid
+
+ The RLSUB command behaves identically to its LSUB counterpart, except
+ remote mailboxes are returned in addition to local mailboxes in the
+ LSUB responses.
+
+6. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) as described in [ABNF].
+
+ list_mailbox = <list_mailbox> as defined in [RFC-2060]
+
+ mailbox = <mailbox> as defined in [RFC-2060]
+
+ mailbox_referral = <tag> SPACE "NO" SPACE
+ <referral_response_code> (text / text_mime2)
+ ; See [RFC-2060] for <tag>, text and text_mime2 definition
+
+
+
+Gahrns Standards Track [Page 7]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+ referral_response_code = "[" "REFERRAL" 1*(SPACE <url>) "]"
+ ; See [RFC-1738] for <url> definition
+
+ rlist = "RLIST" SPACE mailbox SPACE list_mailbox
+
+ rlsub = "RLSUB" SPACE mailbox SPACE list_mailbox
+
+6. Security Considerations
+
+ The IMAP4 referral mechanism makes use of IMAP URLs, and as such,
+ have the same security considerations as general internet URLs [RFC-
+ 1738], and in particular IMAP URLs [RFC-2192].
+
+ With the MAILBOX-REFERRALS capability, it is potentially easier to
+ write a rogue server that injects a bogus referral response that
+ directs a user to an incorrect mailbox. Although referrals reduce
+ the effort to write such a server, the referral response makes
+ detection of the intrusion easier.
+
+7. References
+
+ [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, University of Washington, December 1996.
+
+ [RFC-2192], Newman, C., "IMAP URL Scheme", RFC 2192, Innosoft,
+ September 1997.
+
+ [RFC-1738], Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
+ Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation,
+ University of Minnesota, December 1994.
+
+ [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, Harvard University, March 1997.
+
+ [ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
+ Syntax Specifications: ABNF", Work in Progress, Internet Mail
+ Consortium, April 1997.
+
+8. Acknowledgments
+
+ Many valuable suggestions were received from private discussions and
+ the IMAP4 mailing list. In particular, Raymond Cheng, Mark Crispin,
+ Mark Keasling, Chris Newman and Larry Osterman made significant
+ contributions to this document.
+
+
+
+
+
+
+
+Gahrns Standards Track [Page 8]
+
+RFC 2193 IMAP4 Mailbox Referrals September 1997
+
+
+9. Author's Address
+
+ Mike Gahrns
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98072
+
+ Phone: (206) 936-9833
+ EMail: mikega@microsoft.com
+
+
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+Gahrns Standards Track [Page 9]
+
diff --git a/imap/docs/rfc/rfc2195.txt b/imap/docs/rfc/rfc2195.txt
new file mode 100644
index 00000000..4a2725bf
--- /dev/null
+++ b/imap/docs/rfc/rfc2195.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group J. Klensin
+Request for Comments: 2195 R. Catoe
+Category: Standards Track P. Krumviede
+Obsoletes: 2095 MCI
+ September 1997
+
+
+ IMAP/POP AUTHorize Extension for Simple Challenge/Response
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ While IMAP4 supports a number of strong authentication mechanisms as
+ described in RFC 1731, it lacks any mechanism that neither passes
+ cleartext, reusable passwords across the network nor requires either
+ a significant security infrastructure or that the mail server update
+ a mail-system-wide user authentication file on each mail access.
+ This specification provides a simple challenge-response
+ authentication protocol that is suitable for use with IMAP4. Since
+ it utilizes Keyed-MD5 digests and does not require that the secret be
+ stored in the clear on the server, it may also constitute an
+ improvement on APOP for POP3 use as specified in RFC 1734.
+
+1. Introduction
+
+ Existing Proposed Standards specify an AUTHENTICATE mechanism for the
+ IMAP4 protocol [IMAP, IMAP-AUTH] and a parallel AUTH mechanism for
+ the POP3 protocol [POP3-AUTH]. The AUTHENTICATE mechanism is
+ intended to be extensible; the four methods specified in [IMAP-AUTH]
+ are all fairly powerful and require some security infrastructure to
+ support. The base POP3 specification [POP3] also contains a
+ lightweight challenge-response mechanism called APOP. APOP is
+ associated with most of the risks associated with such protocols: in
+ particular, it requires that both the client and server machines have
+ access to the shared secret in cleartext form. CRAM offers a method
+ for avoiding such cleartext storage while retaining the algorithmic
+ simplicity of APOP in using only MD5, though in a "keyed" method.
+
+
+
+
+
+
+
+Klensin, Catoe & Krumviede Standards Track [Page 1]
+
+RFC 2195 IMAP/POP AUTHorize Extension September 1997
+
+
+ At present, IMAP [IMAP] lacks any facility corresponding to APOP.
+ The only alternative to the strong mechanisms identified in [IMAP-
+ AUTH] is a presumably cleartext username and password, supported
+ through the LOGIN command in [IMAP]. This document describes a
+ simple challenge-response mechanism, similar to APOP and PPP CHAP
+ [PPP], that can be used with IMAP (and, in principle, with POP3).
+
+ This mechanism also has the advantage over some possible alternatives
+ of not requiring that the server maintain information about email
+ "logins" on a per-login basis. While mechanisms that do require such
+ per-login history records may offer enhanced security, protocols such
+ as IMAP, which may have several connections between a given client
+ and server open more or less simultaneous, may make their
+ implementation particularly challenging.
+
+2. Challenge-Response Authentication Mechanism (CRAM)
+
+ The authentication type associated with CRAM is "CRAM-MD5".
+
+ The data encoded in the first ready response contains an
+ presumptively arbitrary string of random digits, a timestamp, and the
+ fully-qualified primary host name of the server. The syntax of the
+ unencoded form must correspond to that of an RFC 822 'msg-id'
+ [RFC822] as described in [POP3].
+
+ The client makes note of the data and then responds with a string
+ consisting of the user name, a space, and a 'digest'. The latter is
+ computed by applying the keyed MD5 algorithm from [KEYED-MD5] where
+ the key is a shared secret and the digested text is the timestamp
+ (including angle-brackets).
+
+ This shared secret is a string known only to the client and server.
+ The `digest' parameter itself is a 16-octet value which is sent in
+ hexadecimal format, using lower-case ASCII characters.
+
+ When the server receives this client response, it verifies the digest
+ provided. If the digest is correct, the server should consider the
+ client authenticated and respond appropriately.
+
+ Keyed MD5 is chosen for this application because of the greater
+ security imparted to authentication of short messages. In addition,
+ the use of the techniques described in [KEYED-MD5] for precomputation
+ of intermediate results make it possible to avoid explicit cleartext
+ storage of the shared secret on the server system by instead storing
+ the intermediate results which are known as "contexts".
+
+
+
+
+
+
+Klensin, Catoe & Krumviede Standards Track [Page 2]
+
+RFC 2195 IMAP/POP AUTHorize Extension September 1997
+
+
+ CRAM does not support a protection mechanism.
+
+ Example:
+
+ The examples in this document show the use of the CRAM mechanism with
+ the IMAP4 AUTHENTICATE command [IMAP-AUTH]. The base64 encoding of
+ the challenges and responses is part of the IMAP4 AUTHENTICATE
+ command, not part of the CRAM specification itself.
+
+ S: * OK IMAP4 Server
+ C: A0001 AUTHENTICATE CRAM-MD5
+ S: + PDE4OTYuNjk3MTcwOTUyQHBvc3RvZmZpY2UucmVzdG9uLm1jaS5uZXQ+
+ C: dGltIGI5MTNhNjAyYzdlZGE3YTQ5NWI0ZTZlNzMzNGQzODkw
+ S: A0001 OK CRAM authentication successful
+
+ In this example, the shared secret is the string
+ 'tanstaaftanstaaf'. Hence, the Keyed MD5 digest is produced by
+ calculating
+
+ MD5((tanstaaftanstaaf XOR opad),
+ MD5((tanstaaftanstaaf XOR ipad),
+ <1896.697170952@postoffice.reston.mci.net>))
+
+ where ipad and opad are as defined in the keyed-MD5 Work in
+ Progress [KEYED-MD5] and the string shown in the challenge is the
+ base64 encoding of <1896.697170952@postoffice.reston.mci.net>. The
+ shared secret is null-padded to a length of 64 bytes. If the
+ shared secret is longer than 64 bytes, the MD5 digest of the
+ shared secret is used as a 16 byte input to the keyed MD5
+ calculation.
+
+ This produces a digest value (in hexadecimal) of
+
+ b913a602c7eda7a495b4e6e7334d3890
+
+ The user name is then prepended to it, forming
+
+ tim b913a602c7eda7a495b4e6e7334d3890
+
+ Which is then base64 encoded to meet the requirements of the IMAP4
+ AUTHENTICATE command (or the similar POP3 AUTH command), yielding
+
+ dGltIGI5MTNhNjAyYzdlZGE3YTQ5NWI0ZTZlNzMzNGQzODkw
+
+
+
+
+
+
+
+
+Klensin, Catoe & Krumviede Standards Track [Page 3]
+
+RFC 2195 IMAP/POP AUTHorize Extension September 1997
+
+
+3. References
+
+ [CHAP] Lloyd, B., and W. Simpson, "PPP Authentication Protocols",
+ RFC 1334, October 1992.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, University of Washington, December 1996.
+
+ [IMAP-AUTH] Myers, J., "IMAP4 Authentication Mechanisms",
+ RFC 1731, Carnegie Mellon, December 1994.
+
+ [KEYED-MD5] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for
+ Message Authentication", RFC 2104, February 1997.
+
+ [MD5] Rivest, R., "The MD5 Message Digest Algorithm",
+ RFC 1321, MIT Laboratory for Computer Science, April 1992.
+
+ [POP3] Myers, J., and M. Rose, "Post Office Protocol - Version 3",
+ STD 53, RFC 1939, Carnegie Mellon, May 1996.
+
+ [POP3-AUTH] Myers, J., "POP3 AUTHentication command", RFC 1734,
+ Carnegie Mellon, December, 1994.
+
+4. Security Considerations
+
+ It is conjectured that use of the CRAM authentication mechanism
+ provides origin identification and replay protection for a session.
+ Accordingly, a server that implements both a cleartext password
+ command and this authentication type should not allow both methods of
+ access for a given user.
+
+ While the saving, on the server, of "contexts" (see section 2) is
+ marginally better than saving the shared secrets in cleartext as is
+ required by CHAP [CHAP] and APOP [POP3], it is not sufficient to
+ protect the secrets if the server itself is compromised.
+ Consequently, servers that store the secrets or contexts must both be
+ protected to a level appropriate to the potential information value
+ in user mailboxes and identities.
+
+ As the length of the shared secret increases, so does the difficulty
+ of deriving it.
+
+ While there are now suggestions in the literature that the use of MD5
+ and keyed MD5 in authentication procedures probably has a limited
+ effective lifetime, the technique is now widely deployed and widely
+ understood. It is believed that this general understanding may
+ assist with the rapid replacement, by CRAM-MD5, of the current uses
+ of permanent cleartext passwords in IMAP. This document has been
+
+
+
+Klensin, Catoe & Krumviede Standards Track [Page 4]
+
+RFC 2195 IMAP/POP AUTHorize Extension September 1997
+
+
+ deliberately written to permit easy upgrading to use SHA (or whatever
+ alternatives emerge) when they are considered to be widely available
+ and adequately safe.
+
+ Even with the use of CRAM, users are still vulnerable to active
+ attacks. An example of an increasingly common active attack is 'TCP
+ Session Hijacking' as described in CERT Advisory CA-95:01 [CERT95].
+
+ See section 1 above for additional discussion.
+
+5. Acknowledgements
+
+ This memo borrows ideas and some text liberally from [POP3] and
+ [RFC-1731] and thanks are due the authors of those documents. Ran
+ Atkinson made a number of valuable technical and editorial
+ contributions to the document.
+
+6. Authors' Addresses
+
+ John C. Klensin
+ MCI Telecommunications
+ 800 Boylston St, 7th floor
+ Boston, MA 02199
+ USA
+
+ EMail: klensin@mci.net
+ Phone: +1 617 960 1011
+
+ Randy Catoe
+ MCI Telecommunications
+ 2100 Reston Parkway
+ Reston, VA 22091
+ USA
+
+ EMail: randy@mci.net
+ Phone: +1 703 715 7366
+
+ Paul Krumviede
+ MCI Telecommunications
+ 2100 Reston Parkway
+ Reston, VA 22091
+ USA
+
+ EMail: paul@mci.net
+ Phone: +1 703 715 7251
+
+
+
+
+
+
+Klensin, Catoe & Krumviede Standards Track [Page 5]
+
diff --git a/imap/docs/rfc/rfc2221.txt b/imap/docs/rfc/rfc2221.txt
new file mode 100644
index 00000000..81d00620
--- /dev/null
+++ b/imap/docs/rfc/rfc2221.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group M. Gahrns
+Request for Comments: 2221 Microsoft
+Category: Standards Track October 1997
+
+
+ IMAP4 Login Referrals
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1997). All Rights Reserved.
+
+1. Abstract
+
+ When dealing with large amounts of users and many IMAP4 [RFC-2060]
+ servers, it is often necessary to move users from one IMAP4 server to
+ another. For example, hardware failures or organizational changes
+ may dictate such a move.
+
+ Login referrals allow clients to transparently connect to an
+ alternate IMAP4 server, if their home IMAP4 server has changed.
+
+ A referral mechanism can provide efficiencies over the alternative
+ 'proxy method', in which the local IMAP4 server contacts the remote
+ server on behalf of the client, and then transfers the data from the
+ remote server to itself, and then on to the client. The referral
+ mechanism's direct client connection to the remote server is often a
+ more efficient use of bandwidth, and does not require the local
+ server to impersonate the client when authenticating to the remote
+ server.
+
+2. Conventions used in this document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ A home server, is an IMAP4 server that contains the user's inbox.
+
+ A remote server is a server that contains remote mailboxes.
+
+
+
+
+
+Gahrns Standards Track [Page 1]
+
+RFC 2221 IMAP4 Login Referrals October 1997
+
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+ IMAP4 servers that support this extension MUST list the keyword
+ LOGIN-REFERRALS in their CAPABILITY response. No client action is
+ needed to invoke the LOGIN-REFERRALS capability in a server.
+
+ A LOGIN-REFERRALS capable IMAP4 server SHOULD NOT return a referral
+ to a server that will return a referral. A client MUST NOT follow
+ more than 10 levels of referral without consulting the user.
+
+ A LOGIN-REFERRALS response code MUST contain as an argument a valid
+ IMAP server URL as defined in [IMAP-URL].
+
+ A home server referral consists of either a tagged NO or OK, or an
+ untagged BYE response that contains a LOGIN-REFERRALS response code.
+
+ Example: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/] Remote Server
+
+ NOTE: user;AUTH=* is specified as required by [IMAP-URL] to avoid a
+ client falling back to anonymous login.
+
+4. Home Server Referrals
+
+ A home server referral may be returned in response to an AUTHENTICATE
+ or LOGIN command, or it may appear in the connection startup banner.
+ If a server returns a home server referral in a tagged NO response,
+ that server does not contain any mailboxes that are accessible to the
+ user. If a server returns a home server referral in a tagged OK
+ response, it indicates that the user's personal mailboxes are
+ elsewhere, but the server contains public mailboxes which are
+ readable by the user. After receiving a home server referral, the
+ client can not make any assumptions as to whether this was a
+ permanent or temporary move of the user.
+
+4.1. LOGIN and AUTHENTICATE Referrals
+
+ An IMAP4 server MAY respond to a LOGIN or AUTHENTICATE command with a
+ home server referral if it wishes to direct the user to another IMAP4
+ server.
+
+ Example: C: A001 LOGIN MIKE PASSWORD
+ S: A001 NO [REFERRAL IMAP://MIKE@SERVER2/] Specified user
+ is invalid on this server. Try SERVER2.
+
+
+
+
+Gahrns Standards Track [Page 2]
+
+RFC 2221 IMAP4 Login Referrals October 1997
+
+
+ Example: C: A001 LOGIN MATTHEW PASSWORD
+ S: A001 OK [REFERRAL IMAP://MATTHEW@SERVER2/] Specified
+ user's personal mailboxes located on Server2, but
+ public mailboxes are available.
+
+ Example: C: A001 AUTHENTICATE GSSAPI
+ <authentication exchange>
+ S: A001 NO [REFERRAL IMAP://user;AUTH=GSSAPI@SERVER2/]
+ Specified user is invalid on this server. Try
+ SERVER2.
+
+4.2. BYE at connection startup referral
+
+ An IMAP4 server MAY respond with an untagged BYE and a REFERRAL
+ response code that contains an IMAP URL to a home server if it is not
+ willing to accept connections and wishes to direct the client to
+ another IMAP4 server.
+
+ Example: S: * BYE [REFERRAL IMAP://user;AUTH=*@SERVER2/] Server not
+ accepting connections. Try SERVER2
+
+5. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) as described in [ABNF].
+
+ This amends the "resp_text_code" element of the IMAP4 grammar
+ described in [RFC-2060]
+
+ resp_text_code =/ "REFERRAL" SPACE <imapurl>
+ ; See [IMAP-URL] for definition of <imapurl>
+ ; See [RFC-2060] for base definition of resp_text_code
+
+6. Security Considerations
+
+ The IMAP4 login referral mechanism makes use of IMAP URLs, and as
+ such, have the same security considerations as general internet URLs
+ [RFC-1738], and in particular IMAP URLs [IMAP-URL].
+
+ A server MUST NOT give a login referral if authentication for that
+ user fails. This is to avoid revealing information about the user's
+ account to an unauthorized user.
+
+ With the LOGIN-REFERRALS capability, it is potentially easier to
+ write a rogue 'password catching' server that collects login data and
+ then refers the client to their actual IMAP4 server. Although
+ referrals reduce the effort to write such a server, the referral
+ response makes detection of the intrusion easier.
+
+
+
+Gahrns Standards Track [Page 3]
+
+RFC 2221 IMAP4 Login Referrals October 1997
+
+
+7. References
+
+ [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+ [IMAP-URL], Newman, C., "IMAP URL Scheme", RFC 2192, Innosoft,
+ September 1997.
+
+ [RFC-1738], Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
+ Resource Locators (URL)", RFC 1738, December 1994.
+
+ [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, March 1997.
+
+ [ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
+ Syntax Specifications: ABNF", Work in Progress.
+
+8. Acknowledgments
+
+ Many valuable suggestions were received from private discussions and
+ the IMAP4 mailing list. In particular, Raymond Cheng, Mark Crispin,
+ Mark Keasling Chris Newman and Larry Osterman made significant
+ contributions to this document.
+
+9. Author's Address
+
+ Mike Gahrns
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98072
+
+ Phone: (206) 936-9833
+ EMail: mikega@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns Standards Track [Page 4]
+
+RFC 2221 IMAP4 Login Referrals October 1997
+
+
+10. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1997). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implmentation may be prepared, copied, published
+ andand distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns Standards Track [Page 5]
+
diff --git a/imap/docs/rfc/rfc2342.txt b/imap/docs/rfc/rfc2342.txt
new file mode 100644
index 00000000..0926646d
--- /dev/null
+++ b/imap/docs/rfc/rfc2342.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group M. Gahrns
+Request for Comments: 2342 Microsoft
+Category: Standards Track C. Newman
+ Innosoft
+ May 1998
+
+
+ IMAP4 Namespace
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+1. Abstract
+
+ IMAP4 [RFC-2060] does not define a default server namespace. As a
+ result, two common namespace models have evolved:
+
+ The "Personal Mailbox" model, in which the default namespace that is
+ presented consists of only the user's personal mailboxes. To access
+ shared mailboxes, the user must use an escape mechanism to reach
+ another namespace.
+
+ The "Complete Hierarchy" model, in which the default namespace that
+ is presented includes the user's personal mailboxes along with any
+ other mailboxes they have access to.
+
+ These two models, create difficulties for certain client operations.
+ This document defines a NAMESPACE command that allows a client to
+ discover the prefixes of namespaces used by a server for personal
+ mailboxes, other users' mailboxes, and shared mailboxes. This allows
+ a client to avoid much of the manual user configuration that is now
+ necessary when mixing and matching IMAP4 clients and servers.
+
+2. Conventions used in this document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. If such lines are wrapped without a new "C:" or
+ "S:" label, then the wrapping is for editorial clarity and is not
+ part of the command.
+
+
+
+Gahrns & Newman Standards Track [Page 1]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ Personal Namespace: A namespace that the server considers within the
+ personal scope of the authenticated user on a particular connection.
+ Typically, only the authenticated user has access to mailboxes in
+ their Personal Namespace. It is the part of the namespace that
+ belongs to the user that is allocated for mailboxes. If an INBOX
+ exists for a user, it MUST appear within the user's personal
+ namespace. In the typical case, there SHOULD be only one Personal
+ Namespace on a server.
+
+ Other Users' Namespace: A namespace that consists of mailboxes from
+ the Personal Namespaces of other users. To access mailboxes in the
+ Other Users' Namespace, the currently authenticated user MUST be
+ explicitly granted access rights. For example, it is common for a
+ manager to grant to their secretary access rights to their mailbox.
+ In the typical case, there SHOULD be only one Other Users' Namespace
+ on a server.
+
+ Shared Namespace: A namespace that consists of mailboxes that are
+ intended to be shared amongst users and do not exist within a user's
+ Personal Namespace.
+
+ The namespaces a server uses MAY differ on a per-user basis.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+3. Introduction and Overview
+
+ Clients often attempt to create mailboxes for such purposes as
+ maintaining a record of sent messages (e.g. "Sent Mail") or
+ temporarily saving messages being composed (e.g. "Drafts"). For
+ these clients to inter-operate correctly with the variety of IMAP4
+ servers available, the user must enter the prefix of the Personal
+ Namespace used by the server. Using the NAMESPACE command, a client
+ is able to automatically discover this prefix without manual user
+ configuration.
+
+ In addition, users are often required to manually enter the prefixes
+ of various namespaces in order to view the mailboxes located there.
+ For example, they might be required to enter the prefix of #shared to
+ view the shared mailboxes namespace. The NAMESPACE command allows a
+ client to automatically discover the namespaces that are available on
+ a server. This allows a client to present the available namespaces to
+ the user in what ever manner it deems appropriate. For example, a
+
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 2]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ client could choose to initially display only personal mailboxes, or
+ it may choose to display the complete list of mailboxes available,
+ and initially position the user at the root of their Personal
+ Namespace.
+
+ A server MAY choose to make available to the NAMESPACE command only a
+ subset of the complete set of namespaces the server supports. To
+ provide the ability to access these namespaces, a client SHOULD allow
+ the user the ability to manually enter a namespace prefix.
+
+4. Requirements
+
+ IMAP4 servers that support this extension MUST list the keyword
+ NAMESPACE in their CAPABILITY response.
+
+ The NAMESPACE command is valid in the Authenticated and Selected
+ state.
+
+5. NAMESPACE Command
+
+ Arguments: none
+
+ Response: an untagged NAMESPACE response that contains the prefix
+ and hierarchy delimiter to the server's Personal
+ Namespace(s), Other Users' Namespace(s), and Shared
+ Namespace(s) that the server wishes to expose. The
+ response will contain a NIL for any namespace class
+ that is not available. Namespace_Response_Extensions
+ MAY be included in the response.
+ Namespace_Response_Extensions which are not on the IETF
+ standards track, MUST be prefixed with an "X-".
+
+ Result: OK - Command completed
+ NO - Error: Can't complete command
+ BAD - argument invalid
+
+ Example 5.1:
+ ===========
+
+ < A server that supports a single personal namespace. No leading
+ prefix is used on personal mailboxes and "/" is the hierarchy
+ delimiter.>
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) NIL NIL
+ S: A001 OK NAMESPACE command completed
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 3]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ Example 5.2:
+ ===========
+
+ < A user logged on anonymously to a server. No personal mailboxes
+ are associated with the anonymous user and the user does not have
+ access to the Other Users' Namespace. No prefix is required to
+ access shared mailboxes and the hierarchy delimiter is "." >
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE NIL NIL (("" "."))
+ S: A001 OK NAMESPACE command completed
+
+ Example 5.3:
+ ===========
+
+ < A server that contains a Personal Namespace and a single Shared
+ Namespace. >
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) NIL (("Public Folders/" "/"))
+ S: A001 OK NAMESPACE command completed
+
+ Example 5.4:
+ ===========
+
+ < A server that contains a Personal Namespace, Other Users'
+ Namespace and multiple Shared Namespaces. Note that the hierarchy
+ delimiter used within each namespace can be different. >
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) (("~" "/")) (("#shared/" "/")
+ ("#public/" "/")("#ftp/" "/")("#news." "."))
+ S: A001 OK NAMESPACE command completed
+
+ The prefix string allows a client to do things such as automatically
+ creating personal mailboxes or LISTing all available mailboxes within
+ a namespace.
+
+ Example 5.5:
+ ===========
+
+ < A server that supports only the Personal Namespace, with a
+ leading prefix of INBOX to personal mailboxes and a hierarchy
+ delimiter of ".">
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("INBOX." ".")) NIL NIL
+ S: A001 OK NAMESPACE command completed
+
+
+
+Gahrns & Newman Standards Track [Page 4]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ < Automatically create a mailbox to store sent items.>
+
+ C: A002 CREATE "INBOX.Sent Mail"
+ S: A002 OK CREATE command completed
+
+ Although typically a server will support only a single Personal
+ Namespace, and a single Other User's Namespace, circumstances exist
+ where there MAY be multiples of these, and a client MUST be prepared
+ for them. If a client is configured such that it is required to
+ create a certain mailbox, there can be circumstances where it is
+ unclear which Personal Namespaces it should create the mailbox in.
+ In these situations a client SHOULD let the user select which
+ namespaces to create the mailbox in.
+
+ Example 5.6:
+ ===========
+
+ < In this example, a server supports 2 Personal Namespaces. In
+ addition to the regular Personal Namespace, the user has an
+ additional personal namespace to allow access to mailboxes in an
+ MH format mailstore. >
+
+ < The client is configured to save a copy of all mail sent by the
+ user into a mailbox called 'Sent Mail'. Furthermore, after a
+ message is deleted from a mailbox, the client is configured to
+ move that message to a mailbox called 'Deleted Items'.>
+
+ < Note that this example demonstrates how some extension flags can
+ be passed to further describe the #mh namespace. >
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")("#mh/" "/" "X-PARAM" ("FLAG1" "FLAG2")))
+ NIL NIL
+ S: A001 OK NAMESPACE command completed
+
+ < It is desired to keep only one copy of sent mail. It is unclear
+ which Personal Namespace the client should use to create the 'Sent
+ Mail' mailbox. The user is prompted to select a namespace and
+ only one 'Sent Mail' mailbox is created. >
+
+ C: A002 CREATE "Sent Mail"
+ S: A002 OK CREATE command completed
+
+ < The client is designed so that it keeps two 'Deleted Items'
+ mailboxes, one for each namespace. >
+
+ C: A003 CREATE "Delete Items"
+ S: A003 OK CREATE command completed
+
+
+
+Gahrns & Newman Standards Track [Page 5]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ C: A004 CREATE "#mh/Deleted Items"
+ S: A004 OK CREATE command completed
+
+ The next level of hierarchy following the Other Users' Namespace
+ prefix SHOULD consist of <username>, where <username> is a user name
+ as per the IMAP4 LOGIN or AUTHENTICATE command.
+
+ A client can construct a LIST command by appending a "%" to the Other
+ Users' Namespace prefix to discover the Personal Namespaces of other
+ users that are available to the currently authenticated user.
+
+ In response to such a LIST command, a server SHOULD NOT return user
+ names that have not granted access to their personal mailboxes to the
+ user in question.
+
+ A server MAY return a LIST response containing only the names of
+ users that have explicitly granted access to the user in question.
+
+ Alternatively, a server MAY return NO to such a LIST command,
+ requiring that a user name be included with the Other Users'
+ Namespace prefix before listing any other user's mailboxes.
+
+ Example 5.7:
+ ===========
+
+ < A server that supports providing a list of other user's
+ mailboxes that are accessible to the currently logged on user. >
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) (("Other Users/" "/")) NIL
+ S: A001 OK NAMESPACE command completed
+
+ C: A002 LIST "" "Other Users/%"
+ S: * LIST () "/" "Other Users/Mike"
+ S: * LIST () "/" "Other Users/Karen"
+ S: * LIST () "/" "Other Users/Matthew"
+ S: * LIST () "/" "Other Users/Tesa"
+ S: A002 OK LIST command completed
+
+ Example 5.8:
+ ===========
+
+ < A server that does not support providing a list of other user's
+ mailboxes that are accessible to the currently logged on user.
+ The mailboxes are listable if the client includes the name of the
+ other user with the Other Users' Namespace prefix. >
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 6]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) (("#Users/" "/")) NIL
+ S: A001 OK NAMESPACE command completed
+
+ < In this example, the currently logged on user has access to the
+ Personal Namespace of user Mike, but the server chose to suppress
+ this information in the LIST response. However, by appending the
+ user name Mike (received through user input) to the Other Users'
+ Namespace prefix, the client is able to get a listing of the
+ personal mailboxes of user Mike. >
+
+ C: A002 LIST "" "#Users/%"
+ S: A002 NO The requested item could not be found.
+
+ C: A003 LIST "" "#Users/Mike/%"
+ S: * LIST () "/" "#Users/Mike/INBOX"
+ S: * LIST () "/" "#Users/Mike/Foo"
+ S: A003 OK LIST command completed.
+
+ A prefix string might not contain a hierarchy delimiter, because
+ in some cases it is not needed as part of the prefix.
+
+ Example 5.9:
+ ===========
+
+ < A server that allows access to the Other Users' Namespace by
+ prefixing the others' mailboxes with a '~' followed by <username>,
+ where <username> is a user name as per the IMAP4 LOGIN or
+ AUTHENTICATE command.>
+
+ C: A001 NAMESPACE
+ S: * NAMESPACE (("" "/")) (("~" "/")) NIL
+ S: A001 OK NAMESPACE command completed
+
+ < List the mailboxes for user mark >
+
+ C: A002 LIST "" "~mark/%"
+ S: * LIST () "/" "~mark/INBOX"
+ S: * LIST () "/" "~mark/foo"
+ S: A002 OK LIST command completed
+
+ Historical convention has been to start all namespaces with the "#"
+ character. Namespaces that include the "#" character are not IMAP
+ URL [IMAP-URL] friendly requiring the "#" character to be represented
+ as %23 when within URLs. As such, server implementers MAY instead
+ consider using namespace prefixes that do not contain the "#"
+ character.
+
+
+
+
+Gahrns & Newman Standards Track [Page 7]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+6. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) as described in [ABNF].
+
+ atom = <atom>
+ ; <atom> as defined in [RFC-2060]
+
+ Namespace = nil / "(" 1*( "(" string SP (<"> QUOTED_CHAR <"> /
+ nil) *(Namespace_Response_Extension) ")" ) ")"
+
+ Namespace_Command = "NAMESPACE"
+
+ Namespace_Response_Extension = SP string SP "(" string *(SP string)
+ ")"
+
+ Namespace_Response = "*" SP "NAMESPACE" SP Namespace SP Namespace SP
+ Namespace
+
+ ; The first Namespace is the Personal Namespace(s)
+ ; The second Namespace is the Other Users' Namespace(s)
+ ; The third Namespace is the Shared Namespace(s)
+
+ nil = <nil>
+ ; <nil> as defined in [RFC-2060]
+
+ QUOTED_CHAR = <QUOTED_CHAR>
+ ; <QUOTED_CHAR> as defined in [RFC-2060]
+
+ string = <string>
+ ; <string> as defined in [RFC-2060]
+ ; Note that the namespace prefix is to a mailbox and following
+ ; IMAP4 convention, any international string in the NAMESPACE
+ ; response MUST be of modified UTF-7 format as described in
+ ; [RFC-2060].
+
+7. Security Considerations
+
+ In response to a LIST command containing an argument of the Other
+ Users' Namespace prefix, a server SHOULD NOT list users that have not
+ granted list access to their personal mailboxes to the currently
+ authenticated user. Providing such a list, could compromise security
+ by potentially disclosing confidential information of who is located
+ on the server, or providing a starting point of a list of user
+ accounts to attack.
+
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 8]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+8. References
+
+ [RFC-2060], Crispin, M., "Internet Message Access Protocol Version
+ 4rev1", RFC 2060, December 1996.
+
+ [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [ABNF] Crocker, D., Editor, and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+ [IMAP-URL], Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+9. Acknowledgments
+
+ Many people have participated in the discussion of IMAP namespaces on
+ the IMAP mailing list. In particular, the authors would like to
+ thank Mark Crispin for many of the concepts relating to the Personal
+ Namespace and accessing the Personal Namespace of other users, Steve
+ Hole for summarizing the two namespace models, John Myers and Jack De
+ Winter for their work in a preceding effort trying to define a
+ standardized personal namespace, and Larry Osterman for his review
+ and collaboration on this document.
+
+11. Authors' Addresses
+
+ Mike Gahrns
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98072, USA
+
+ Phone: (425) 936-9833
+ EMail: mikega@microsoft.com
+
+
+ Chris Newman
+ Innosoft International, Inc.
+ 1050 East Garvey Ave. South
+ West Covina, CA, 91790, USA
+
+ EMail: chris.newman@innosoft.com
+
+
+
+
+
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 9]
+
+RFC 2342 IMAP4 Namespace May 1998
+
+
+12. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1998). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns & Newman Standards Track [Page 10]
+
diff --git a/imap/docs/rfc/rfc2683.txt b/imap/docs/rfc/rfc2683.txt
new file mode 100644
index 00000000..d92e3405
--- /dev/null
+++ b/imap/docs/rfc/rfc2683.txt
@@ -0,0 +1,1291 @@
+
+
+
+
+
+
+Network Working Group B. Leiba
+Request for Comments: 2683 IBM T.J. Watson Research Center
+Category: Informational September 1999
+
+
+ IMAP4 Implementation Recommendations
+
+Status of this Memo
+
+ This memo provides information for the Internet community. It does
+ not specify an Internet standard of any kind. Distribution of this
+ memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+1. Abstract
+
+ The IMAP4 specification [RFC-2060] describes a rich protocol for use
+ in building clients and servers for storage, retrieval, and
+ manipulation of electronic mail. Because the protocol is so rich and
+ has so many implementation choices, there are often trade-offs that
+ must be made and issues that must be considered when designing such
+ clients and servers. This document attempts to outline these issues
+ and to make recommendations in order to make the end products as
+ interoperable as possible.
+
+2. Conventions used in this document
+
+ In examples, "C:" indicates lines sent by a client that is connected
+ to a server. "S:" indicates lines sent by the server to the client.
+
+ The words "must", "must not", "should", "should not", and "may" are
+ used with specific meaning in this document; since their meaning is
+ somewhat different from that specified in RFC 2119, we do not put
+ them in all caps here. Their meaning is as follows:
+
+ must -- This word means that the action described is necessary
+ to ensure interoperability. The recommendation should
+ not be ignored.
+ must not -- This phrase means that the action described will be
+ almost certain to hurt interoperability. The
+ recommendation should not be ignored.
+
+
+
+
+
+
+
+Leiba Informational [Page 1]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ should -- This word means that the action described is strongly
+ recommended and will enhance interoperability or
+ usability. The recommendation should not be ignored
+ without careful consideration.
+ should not -- This phrase means that the action described is strongly
+ recommended against, and might hurt interoperability or
+ usability. The recommendation should not be ignored
+ without careful consideration.
+ may -- This word means that the action described is an
+ acceptable implementation choice. No specific
+ recommendation is implied; this word is used to point
+ out a choice that might not be obvious, or to let
+ implementors know what choices have been made by
+ existing implementations.
+
+3. Interoperability Issues and Recommendations
+
+3.1. Accessibility
+
+ This section describes the issues related to access to servers and
+ server resources. Concerns here include data sharing and maintenance
+ of client/server connections.
+
+3.1.1. Multiple Accesses of the Same Mailbox
+
+ One strong point of IMAP4 is that, unlike POP3, it allows for
+ multiple simultaneous access to a single mailbox. A user can, thus,
+ read mail from a client at home while the client in the office is
+ still connected; or the help desk staff can all work out of the same
+ inbox, all seeing the same pool of questions. An important point
+ about this capability, though is that NO SERVER IS GUARANTEED TO
+ SUPPORT THIS. If you are selecting an IMAP server and this facility
+ is important to you, be sure that the server you choose to install,
+ in the configuration you choose to use, supports it.
+
+ If you are designing a client, you must not assume that you can
+ access the same mailbox more than once at a time. That means
+
+ 1. you must handle gracefully the failure of a SELECT command if the
+ server refuses the second SELECT,
+ 2. you must handle reasonably the severing of your connection (see
+ "Severed Connections", below) if the server chooses to allow the
+ second SELECT by forcing the first off,
+ 3. you must avoid making multiple connections to the same mailbox in
+ your own client (for load balancing or other such reasons), and
+ 4. you must avoid using the STATUS command on a mailbox that you have
+ selected (with some server implementations the STATUS command has
+ the same problems with multiple access as do the SELECT and
+
+
+
+Leiba Informational [Page 2]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ EXAMINE commands).
+
+ A further note about STATUS: The STATUS command is sometimes used to
+ check a non-selected mailbox for new mail. This mechanism must not
+ be used to check for new mail in the selected mailbox; section 5.2 of
+ [RFC-2060] specifically forbids this in its last paragraph. Further,
+ since STATUS takes a mailbox name it is an independent operation, not
+ operating on the selected mailbox. Because of this, the information
+ it returns is not necessarily in synchronization with the selected
+ mailbox state.
+
+3.1.2. Severed Connections
+
+ The client/server connection may be severed for one of three reasons:
+ the client severs the connection, the server severs the connection,
+ or the connection is severed by outside forces beyond the control of
+ the client and the server (a telephone line drops, for example).
+ Clients and servers must both deal with these situations.
+
+ When the client wants to sever a connection, it's usually because it
+ has finished the work it needed to do on that connection. The client
+ should send a LOGOUT command, wait for the tagged response, and then
+ close the socket. But note that, while this is what's intended in
+ the protocol design, there isn't universal agreement here. Some
+ contend that sending the LOGOUT and waiting for the two responses
+ (untagged BYE and tagged OK) is wasteful and unnecessary, and that
+ the client can simply close the socket. The server should interpret
+ the closed socket as a log out by the client. The counterargument is
+ that it's useful from the standpoint of cleanup, problem
+ determination, and the like, to have an explicit client log out,
+ because otherwise there is no way for the server to tell the
+ difference between "closed socket because of log out" and "closed
+ socket because communication was disrupted". If there is a
+ client/server interaction problem, a client which routinely
+ terminates a session by breaking the connection without a LOGOUT will
+ make it much more difficult to determine the problem.
+
+ Because of this disagreement, server designers must be aware that
+ some clients might close the socket without sending a LOGOUT. In any
+ case, whether or not a LOGOUT was sent, the server should not
+ implicitly expunge any messages from the selected mailbox. If a
+ client wants the server to do so, it must send a CLOSE or EXPUNGE
+ command explicitly.
+
+ When the server wants to sever a connection it's usually due to an
+ inactivity timeout or is because a situation has arisen that has
+ changed the state of the mail store in a way that the server can not
+ communicate to the client. The server should send an untagged BYE
+
+
+
+Leiba Informational [Page 3]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ response to the client and then close the socket. Sending an
+ untagged BYE response before severing allows the server to send a
+ human-readable explanation of the problem to the client, which the
+ client may then log, display to the user, or both (see section 7.1.5
+ of [RFC-2060]).
+
+ Regarding inactivity timeouts, there is some controversy. Unlike
+ POP, for which the design is for a client to connect, retrieve mail,
+ and log out, IMAP's design encourages long-lived (and mostly
+ inactive) client/server sessions. As the number of users grows, this
+ can use up a lot of server resources, especially with clients that
+ are designed to maintain sessions for mailboxes that the user has
+ finished accessing. To alleviate this, a server may implement an
+ inactivity timeout, unilaterally closing a session (after first
+ sending an untagged BYE, as noted above). Some server operators have
+ reported dramatic improvements in server performance after doing
+ this. As specified in [RFC-2060], if such a timeout is done it must
+ not be until at least 30 minutes of inactivity. The reason for this
+ specification is to prevent clients from sending commands (such as
+ NOOP) to the server at frequent intervals simply to avert a too-early
+ timeout. If the client knows that the server may not time out the
+ session for at least 30 minutes, then the client need not poll at
+ intervals more frequent than, say, 25 minutes.
+
+3.2. Scaling
+
+ IMAP4 has many features that allow for scalability, as mail stores
+ become larger and more numerous. Large numbers of users, mailboxes,
+ and messages, and very large messages require thought to handle
+ efficiently. This document will not address the administrative
+ issues involved in large numbers of users, but we will look at the
+ other items.
+
+3.2.1. Flood Control
+
+ There are three situations when a client can make a request that will
+ result in a very large response - too large for the client reasonably
+ to deal with: there are a great many mailboxes available, there are a
+ great many messages in the selected mailbox, or there is a very large
+ message part. The danger here is that the end user will be stuck
+ waiting while the server sends (and the client processes) an enormous
+ response. In all of these cases there are things a client can do to
+ reduce that danger.
+
+ There is also the case where a client can flood a server, by sending
+ an arbitratily long command. We'll discuss that issue, too, in this
+ section.
+
+
+
+
+Leiba Informational [Page 4]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+3.2.1.1. Listing Mailboxes
+
+ Some servers present Usenet newsgroups to IMAP users. Newsgroups,
+ and other such hierarchical mailbox structures, can be very numerous
+ but may have only a few entries at the top level of hierarchy. Also,
+ some servers are built against mail stores that can, unbeknownst to
+ the server, have circular hierarchies - that is, it's possible for
+ "a/b/c/d" to resolve to the same file structure as "a", which would
+ then mean that "a/b/c/d/b" is the same as "a/b", and the hierarchy
+ will never end. The LIST response in this case will be unlimited.
+
+ Clients that will have trouble with this are those that use
+
+ C: 001 LIST "" *
+
+ to determine the mailbox list. Because of this, clients should not
+ use an unqualified "*" that way in the LIST command. A safer
+ approach is to list each level of hierarchy individually, allowing
+ the user to traverse the tree one limb at a time, thus:
+
+ C: 001 LIST "" %
+ S: * LIST () "/" Banana
+ S: * LIST ...etc...
+ S: 001 OK done
+
+ and then
+
+ C: 002 LIST "" Banana/%
+ S: * LIST () "/" Banana/Apple
+ S: * LIST ...etc...
+ S: 002 OK done
+
+ Using this technique the client's user interface can give the user
+ full flexibility without choking on the voluminous reply to "LIST *".
+
+ Of course, it is still possible that the reply to
+
+ C: 005 LIST "" alt.fan.celebrity.%
+
+ may be thousands of entries long, and there is, unfortunately,
+ nothing the client can do to protect itself from that. This has not
+ yet been a notable problem.
+
+ Servers that may export circular hierarchies (any server that
+ directly presents a UNIX file system, for instance) should limit the
+ hierarchy depth to prevent unlimited LIST responses. A suggested
+ depth limit is 20 hierarchy levels.
+
+
+
+
+Leiba Informational [Page 5]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+3.2.1.2. Fetching the List of Messages
+
+ When a client selects a mailbox, it is given a count, in the untagged
+ EXISTS response, of the messages in the mailbox. This number can be
+ very large. In such a case it might be unwise to use
+
+ C: 004 FETCH 1:* ALL
+
+ to populate the user's view of the mailbox. One good method to avoid
+ problems with this is to batch the requests, thus:
+
+ C: 004 FETCH 1:50 ALL
+ S: * 1 FETCH ...etc...
+ S: 004 OK done
+ C: 005 FETCH 51:100 ALL
+ S: * 51 FETCH ...etc...
+ S: 005 OK done
+ C: 006 FETCH 101:150 ALL
+ ...etc...
+
+ Using this method, another command, such as "FETCH 6 BODY[1]" can be
+ inserted as necessary, and the client will not have its access to the
+ server blocked by a storm of FETCH replies. (Such a method could be
+ reversed to fetch the LAST 50 messages first, then the 50 prior to
+ that, and so on.)
+
+ As a smart extension of this, a well designed client, prepared for
+ very large mailboxes, will not automatically fetch data for all
+ messages AT ALL. Rather, the client will populate the user's view
+ only as the user sees it, possibly pre-fetching selected information,
+ and only fetching other information as the user scrolls to it. For
+ example, to select only those messages beginning with the first
+ unseen one:
+
+ C: 003 SELECT INBOX
+ S: * 10000 EXISTS
+ S: * 80 RECENT
+ S: * FLAGS (\Answered \Flagged \Deleted \Draft \Seen)
+ S: * OK [UIDVALIDITY 824708485] UID validity status
+ S: * OK [UNSEEN 9921] First unseen message
+ S: 003 OK [READ-WRITE] SELECT completed
+ C: 004 FETCH 9921:* ALL
+ ... etc...
+
+ If the server does not return an OK [UNSEEN] response, the client may
+ use SEARCH UNSEEN to obtain that value.
+
+
+
+
+
+Leiba Informational [Page 6]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ This mechanism is good as a default presentation method, but only
+ works well if the default message order is acceptable. A client may
+ want to present various sort orders to the user (by subject, by date
+ sent, by sender, and so on) and in that case (lacking a SORT
+ extension on the server side) the client WILL have to retrieve all
+ message descriptors. A client that provides this service should not
+ do it by default and should inform the user of the costs of choosing
+ this option for large mailboxes.
+
+3.2.1.3. Fetching a Large Body Part
+
+ The issue here is similar to the one for a list of messages. In the
+ BODYSTRUCTURE response the client knows the size, in bytes, of the
+ body part it plans to fetch. Suppose this is a 70 MB video clip. The
+ client can use partial fetches to retrieve the body part in pieces,
+ avoiding the problem of an uninterruptible 70 MB literal coming back
+ from the server:
+
+ C: 022 FETCH 3 BODY[1]<0.20000>
+ S: * 3 FETCH (FLAGS(\Seen) BODY[1]<0> {20000}
+ S: ...data...)
+ S: 022 OK done
+ C: 023 FETCH 3 BODY[1]<20001.20000>
+ S: * 3 FETCH (BODY[1]<20001> {20000}
+ S: ...data...)
+ S: 023 OK done
+ C: 024 FETCH 3 BODY[1]<40001.20000>
+ ...etc...
+
+3.2.1.4. BODYSTRUCTURE vs. Entire Messages
+
+ Because FETCH BODYSTRUCTURE is necessary in order to determine the
+ number of body parts, and, thus, whether a message has "attachments",
+ clients often use FETCH FULL as their normal method of populating the
+ user's view of a mailbox. The benefit is that the client can display
+ a paperclip icon or some such indication along with the normal
+ message summary. However, this comes at a significant cost with some
+ server configurations. The parsing needed to generate the FETCH
+ BODYSTRUCTURE response may be time-consuming compared with that
+ needed for FETCH ENVELOPE. The client developer should consider this
+ issue when deciding whether the ability to add a paperclip icon is
+ worth the tradeoff in performance, especially with large mailboxes.
+
+ Some clients, rather than using FETCH BODYSTRUCTURE, use FETCH BODY[]
+ (or the equivalent FETCH RFC822) to retrieve the entire message.
+ They then do the MIME parsing in the client. This may give the
+ client slightly more flexibility in some areas (access, for instance,
+ to header fields that aren't returned in the BODYSTRUCTURE and
+
+
+
+Leiba Informational [Page 7]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ ENVELOPE responses), but it can cause severe performance problems by
+ forcing the transfer of all body parts when the user might only want
+ to see some of them - a user logged on by modem and reading a small
+ text message with a large ZIP file attached may prefer to read the
+ text only and save the ZIP file for later. Therefore, a client
+ should not normally retrieve entire messages and should retrieve
+ message body parts selectively.
+
+3.2.1.5. Long Command Lines
+
+ A client can wind up building a very long command line in an effort to
+ try to be efficient about requesting information from a server. This
+ can typically happen when a client builds a message set from selected
+ messages and doesn't recognise that contiguous blocks of messages may
+ be group in a range. Suppose a user selects all 10,000 messages in a
+ large mailbox and then unselects message 287. The client could build
+ that message set as "1:286,288:10000", but a client that doesn't
+ handle that might try to enumerate each message individually and build
+ "1,2,3,4, [and so on] ,9999,10000". Adding that to the fetch command
+ results in a command line that's almost 49,000 octets long, and,
+ clearly, one can construct a command line that's even longer.
+
+ A client should limit the length of the command lines it generates to
+ approximately 1000 octets (including all quoted strings but not
+ including literals). If the client is unable to group things into
+ ranges so that the command line is within that length, it should
+ split the request into multiple commands. The client should use
+ literals instead of long quoted strings, in order to keep the command
+ length down.
+
+ For its part, a server should allow for a command line of at least
+ 8000 octets. This provides plenty of leeway for accepting reasonable
+ length commands from clients. The server should send a BAD response
+ to a command that does not end within the server's maximum accepted
+ command length.
+
+3.2.2. Subscriptions
+
+ The client isn't the only entity that can get flooded: the end user,
+ too, may need some flood control. The IMAP4 protocol provides such
+ control in the form of subscriptions. Most servers support the
+ SUBSCRIBE, UNSUBSCRIBE, and LSUB commands, and many users choose to
+ narrow down a large list of available mailboxes by subscribing to the
+ ones that they usually want to see. Clients, with this in mind,
+ should give the user a way to see only subscribed mailboxes. A
+ client that never uses the LSUB command takes a significant usability
+ feature away from the user. Of course, the client would not want to
+ hide the LIST command completely; the user needs to have a way to
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ choose between LIST and LSUB. The usual way to do this is to provide
+ a setting like "show which mailboxes?: [] all [] subscribed only".
+
+3.2.3. Searching
+
+ IMAP SEARCH commands can become particularly troublesome (that is,
+ slow) on mailboxes containing a large number of messages. So let's
+ put a few things in perspective in that regard.
+
+ The flag searches should be fast. The flag searches (ALL, [UN]SEEN,
+ [UN]ANSWERED, [UN]DELETED, [UN]DRAFT, [UN]FLAGGED, NEW, OLD, RECENT)
+ are known to be used by clients for the client's own use (for
+ instance, some clients use "SEARCH UNSEEN" to find unseen mail and
+ "SEARCH DELETED" to warn the user before expunging messages).
+
+ Other searches, particularly the text searches (HEADER, TEXT, BODY)
+ are initiated by the user, rather than by the client itself, and
+ somewhat slower performance can be tolerated, since the user is aware
+ that the search is being done (and is probably aware that it might be
+ time-consuming). A smart server might use dynamic indexing to speed
+ commonly used text searches.
+
+ The client may allow other commands to be sent to the server while a
+ SEARCH is in progress, but at the time of this writing there is
+ little or no server support for parallel processing of multiple
+ commands in the same session (and see "Multiple Accesses of the Same
+ Mailbox" above for a description of the dangers of trying to work
+ around this by doing your SEARCH in another session).
+
+ Another word about text searches: some servers, built on database
+ back-ends with indexed search capabilities, may return search results
+ that do not match the IMAP spec's "case-insensitive substring"
+ requirements. While these servers are in violation of the protocol,
+ there is little harm in the violation as long as the search results
+ are used only in response to a user's request. Still, developers of
+ such servers should be aware that they ARE violating the protocol,
+ should think carefully about that behaviour, and must be certain that
+ their servers respond accurately to the flag searches for the reasons
+ outlined above.
+
+ In addition, servers should support CHARSET UTF-8 [UTF-8] in
+ searches.
+
+
+
+
+
+
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+3.3 Avoiding Invalid Requests
+
+ IMAP4 provides ways for a server to tell a client in advance what is
+ and isn't permitted in some circumstances. Clients should use these
+ features to avoid sending requests that a well designed client would
+ know to be invalid. This section explains this in more detail.
+
+3.3.1. The CAPABILITY Command
+
+ All IMAP4 clients should use the CAPABILITY command to determine what
+ version of IMAP and what optional features a server supports. The
+ client should not send IMAP4rev1 commands and arguments to a server
+ that does not advertize IMAP4rev1 in its CAPABILITY response.
+ Similarly, the client should not send IMAP4 commands that no longer
+ exist in IMAP4rev1 to a server that does not advertize IMAP4 in its
+ CAPABILITY response. An IMAP4rev1 server is NOT required to support
+ obsolete IMAP4 or IMAP2bis commands (though some do; do not let this
+ fact lull you into thinking that it's valid to send such commands to
+ an IMAP4rev1 server).
+
+ A client should not send commands to probe for the existance of
+ certain extensions. All standard and standards-track extensions
+ include CAPABILITY tokens indicating their presense. All private and
+ experimental extensions should do the same, and clients that take
+ advantage of them should use the CAPABILITY response to determine
+ whether they may be used or not.
+
+3.3.2. Don't Do What the Server Says You Can't
+
+ In many cases, the server, in response to a command, will tell the
+ client something about what can and can't be done with a particular
+ mailbox. The client should pay attention to this information and
+ should not try to do things that it's been told it can't do.
+
+ Examples:
+
+ * Do not try to SELECT a mailbox that has the \Noselect flag set.
+ * Do not try to CREATE a sub-mailbox in a mailbox that has the
+ \Noinferiors flag set.
+ * Do not respond to a failing COPY or APPEND command by trying to
+ CREATE the target mailbox if the server does not respond with a
+ [TRYCREATE] response code.
+ * Do not try to expunge a mailbox that has been selected with the
+ [READ-ONLY] response code.
+
+
+
+
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+3.4. Miscellaneous Protocol Considerations
+
+ We describe here a number of important protocol-related issues, the
+ misunderstanding of which has caused significant interoperability
+ problems in IMAP4 implementations. One general item is that every
+ implementer should be certain to take note of and to understand
+ section 2.2.2 and the preamble to section 7 of the IMAP4rev1 spec
+ [RFC-2060].
+
+3.4.1. Well Formed Protocol
+
+ We cannot stress enough the importance of adhering strictly to the
+ protocol grammar. The specification of the protocol is quite rigid;
+ do not assume that you can insert blank space for "readability" if
+ none is called for. Keep in mind that there are parsers out there
+ that will crash if there are protocol errors. There are clients that
+ will report every parser burp to the user. And in any case,
+ information that cannot be parsed is information that is lost. Be
+ careful in your protocol generation. And see "A Word About Testing",
+ below.
+
+ In particular, note that the string in the INTERNALDATE response is
+ NOT an RFC-822 date string - that is, it is not in the same format as
+ the first string in the ENVELOPE response. Since most clients will,
+ in fact, accept an RFC-822 date string in the INTERNALDATE response,
+ it's easy to miss this in your interoperability testing. But it will
+ cause a problem with some client, so be sure to generate the correct
+ string for this field.
+
+3.4.2. Special Characters
+
+ Certain characters, currently the double-quote and the backslash, may
+ not be sent as-is inside a quoted string. These characters must be
+ preceded by the escape character if they are in a quoted string, or
+ else the string must be sent as a literal. Both clients and servers
+ must handle this, both on output (they must send these characters
+ properly) and on input (they must be able to receive escaped
+ characters in quoted strings). Example:
+
+ C: 001 LIST "" %
+ S: * LIST () "" INBOX
+ S: * LIST () "\\" TEST
+ S: * LIST () "\\" {12}
+ S: "My" mailbox
+ S: 001 OK done
+ C: 002 LIST "" "\"My\" mailbox\\%"
+ S: * LIST () "\\" {17}
+ S: "My" mailbox\Junk
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ S: 002 OK done
+
+ Note that in the example the server sent the hierarchy delimiter as
+ an escaped character in the quoted string and sent the mailbox name
+ containing imbedded double-quotes as a literal. The client used only
+ quoted strings, escaping both the backslash and the double-quote
+ characters.
+
+ The CR and LF characters may be sent ONLY in literals; they are not
+ allowed, even if escaped, inside quoted strings.
+
+ And while we're talking about special characters: the IMAP spec, in
+ the section titled "Mailbox International Naming Convention",
+ describes how to encode mailbox names in modified UTF-7 [UTF-7 and
+ RFC-2060]. Implementations must adhere to this in order to be
+ interoperable in the international market, and servers should
+ validate mailbox names sent by client and reject names that do not
+ conform.
+
+ As to special characters in userids and passwords: clients must not
+ restrict what a user may type in for a userid or a password. The
+ formal grammar specifies that these are "astrings", and an astring
+ can be a literal. A literal, in turn can contain any 8-bit
+ character, and clients must allow users to enter all 8-bit characters
+ here, and must pass them, unchanged, to the server (being careful to
+ send them as literals when necessary). In particular, some server
+ configurations use "@" in user names, and some clients do not allow
+ that character to be entered; this creates a severe interoperability
+ problem.
+
+3.4.3. UIDs and UIDVALIDITY
+
+ Servers that support existing back-end mail stores often have no good
+ place to save UIDs for messages. Often the existing mail store will
+ not have the concept of UIDs in the sense that IMAP has: strictly
+ increasing, never re-issued, 32-bit integers. Some servers solve
+ this by storing the UIDs in a place that's accessible to end users,
+ allowing for the possibility that the users will delete them. Others
+ solve it by re-assigning UIDs every time a mailbox is selected.
+
+ The server should maintain UIDs permanently for all messages if it
+ can. If that's not possible, the server must change the UIDVALIDITY
+ value for the mailbox whenever any of the UIDs may have become
+ invalid. Clients must recognize that the UIDVALIDITY has changed and
+ must respond to that condition by throwing away any information that
+ they have saved about UIDs in that mailbox. There have been many
+ problems in this area when clients have failed to do this; in the
+ worst case it will result in loss of mail when a client deletes the
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ wrong piece of mail by using a stale UID.
+
+ It seems to be a common misunderstanding that "the UIDVALIDITY and
+ the UID, taken together, form a 64-bit identifier that uniquely
+ identifies a message on a server". This is absolutely NOT TRUE.
+ There is no assurance that the UIDVALIDITY values of two mailboxes be
+ different, so the UIDVALIDITY in no way identifies a mailbox. The
+ ONLY purpose of UIDVALIDITY is, as its name indicates, to give the
+ client a way to check the validity of the UIDs it has cached. While
+ it is a valid implementation choice to put these values together to
+ make a 64-bit identifier for the message, the important concept here
+ is that UIDs are not unique between mailboxes; they are only unique
+ WITHIN a given mailbox.
+
+ Some server implementations have attempted to make UIDs unique across
+ the entire server. This is inadvisable, in that it limits the life
+ of UIDs unnecessarily. The UID is a 32-bit number and will run out
+ in reasonably finite time if it's global across the server. If you
+ assign UIDs sequentially in one mailbox, you will not have to start
+ re-using them until you have had, at one time or another, 2**32
+ different messages in that mailbox. In the global case, you will
+ have to reuse them once you have had, at one time or another, 2**32
+ different messages in the entire mail store. Suppose your server has
+ around 8000 users registered (2**13). That gives an average of 2**19
+ UIDs per user. Suppose each user gets 32 messages (2**5) per day.
+ That gives you 2**14 days (16000+ days = about 45 years) before you
+ run out. That may seem like enough, but multiply the usage just a
+ little (a lot of spam, a lot of mailing list subscriptions, more
+ users) and you limit yourself too much.
+
+ What's worse is that if you have to wrap the UIDs, and, thus, you
+ have to change UIDVALIDITY and invalidate the UIDs in the mailbox,
+ you have to do it for EVERY mailbox in the system, since they all
+ share the same UID pool. If you assign UIDs per mailbox and you have
+ a problem, you only have to kill the UIDs for that one mailbox.
+
+ Under extreme circumstances (and this is extreme, indeed), the server
+ may have to invalidate UIDs while a mailbox is in use by a client -
+ that is, the UIDs that the client knows about in its active mailbox
+ are no longer valid. In that case, the server must immediately
+ change the UIDVALIDITY and must communicate this to the client. The
+ server may do this by sending an unsolicited UIDVALIDITY message, in
+ the same form as in response to the SELECT command. Clients must be
+ prepared to handle such a message and the possibly coincident failure
+ of the command in process. For example:
+
+
+
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ C: 032 UID STORE 382 +Flags.silent \Deleted
+ S: * OK [UIDVALIDITY 12345] New UIDVALIDITY value!
+ S: 032 NO UID command rejected because UIDVALIDITY changed!
+ C: ...invalidates local information and re-fetches...
+ C: 033 FETCH 1:* UID
+ ...etc...
+
+ At the time of the writing of this document, the only server known to
+ do this does so only under the following condition: the client
+ selects INBOX, but there is not yet a physical INBOX file created.
+ Nonetheless, the SELECT succeeds, exporting an empty INBOX with a
+ temporary UIDVALIDITY of 1. While the INBOX remains selected, mail
+ is delivered to the user, which creates the real INBOX file and
+ assigns a permanent UIDVALIDITY (that is likely not to be 1). The
+ server reports the change of UIDVALIDITY, but as there were no
+ messages before, so no UIDs have actually changed, all the client
+ must do is accept the change in UIDVALIDITY.
+
+ Alternatively, a server may force the client to re-select the
+ mailbox, at which time it will obtain a new UIDVALIDITY value. To do
+ this, the server closes this client session (see "Severed
+ Connections" above) and the client then reconnects and gets back in
+ synch. Clients must be prepared for either of these behaviours.
+
+ We do not know of, nor do we anticipate the future existance of, a
+ server that changes UIDVALIDITY while there are existing messages,
+ but clients must be prepared to handle this eventuality.
+
+3.4.4. FETCH Responses
+
+ When a client asks for certain information in a FETCH command, the
+ server may return the requested information in any order, not
+ necessarily in the order that it was requested. Further, the server
+ may return the information in separate FETCH responses and may also
+ return information that was not explicitly requested (to reflect to
+ the client changes in the state of the subject message). Some
+ examples:
+
+ C: 001 FETCH 1 UID FLAGS INTERNALDATE
+ S: * 5 FETCH (FLAGS (\Deleted))
+ S: * 1 FETCH (FLAGS (\Seen) INTERNALDATE "..." UID 345)
+ S: 001 OK done
+
+ (In this case, the responses are in a different order. Also, the
+ server returned a flag update for message 5, which wasn't part of the
+ client's request.)
+
+
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ C: 002 FETCH 2 UID FLAGS INTERNALDATE
+ S: * 2 FETCH (INTERNALDATE "...")
+ S: * 2 FETCH (UID 399)
+ S: * 2 FETCH (FLAGS ())
+ S: 002 OK done
+
+ (In this case, the responses are in a different order and were
+ returned in separate responses.)
+
+ C: 003 FETCH 2 BODY[1]
+ S: * 2 FETCH (FLAGS (\Seen) BODY[1] {14}
+ S: Hello world!
+ S: )
+ S: 003 OK done
+
+ (In this case, the FLAGS response was added by the server, since
+ fetching the body part caused the server to set the \Seen flag.)
+
+ Because of this characteristic a client must be ready to receive any
+ FETCH response at any time and should use that information to update
+ its local information about the message to which the FETCH response
+ refers. A client must not assume that any FETCH responses will come
+ in any particular order, or even that any will come at all. If after
+ receiving the tagged response for a FETCH command the client finds
+ that it did not get all of the information requested, the client
+ should send a NOOP command to the server to ensure that the server
+ has an opportunity to send any pending EXPUNGE responses to the
+ client (see [RFC-2180]).
+
+3.4.5. RFC822.SIZE
+
+ Some back-end mail stores keep the mail in a canonical form, rather
+ than retaining the original MIME format of the messages. This means
+ that the server must reassemble the message to produce a MIME stream
+ when a client does a fetch such as RFC822 or BODY[], requesting the
+ entire message. It also may mean that the server has no convenient
+ way to know the RFC822.SIZE of the message. Often, such a server
+ will actually have to build the MIME stream to compute the size, only
+ to throw the stream away and report the size to the client.
+
+ When this is the case, some servers have chosen to estimate the size,
+ rather than to compute it precisely. Such an estimate allows the
+ client to display an approximate size to the user and to use the
+ estimate in flood control considerations (q.v.), but requires that
+ the client not use the size for things such as allocation of buffers,
+ because those buffers might then be too small to hold the actual MIME
+ stream. Instead, a client should use the size that's returned in the
+ literal when you fetch the data.
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ The protocol requires that the RFC822.SIZE value returned by the
+ server be EXACT. Estimating the size is a protocol violation, and
+ server designers must be aware that, despite the performance savings
+ they might realize in using an estimate, this practice will cause
+ some clients to fail in various ways. If possible, the server should
+ compute the RFC822.SIZE for a particular message once, and then save
+ it for later retrieval. If that's not possible, the server must
+ compute the value exactly every time. Incorrect estimates do cause
+ severe interoperability problems with some clients.
+
+3.4.6. Expunged Messages
+
+ If the server allows multiple connections to the same mailbox, it is
+ often possible for messages to be expunged in one client unbeknownst
+ to another client. Since the server is not allowed to tell the
+ client about these expunged messages in response to a FETCH command,
+ the server may have to deal with the issue of how to return
+ information about an expunged message. There was extensive
+ discussion about this issue, and the results of that discussion are
+ summarized in [RFC-2180]. See that reference for a detailed
+ explanation and for recommendations.
+
+3.4.7. The Namespace Issue
+
+ Namespaces are a very muddy area in IMAP4 implementation right now
+ (see [NAMESPACE] for a proposal to clear the water a bit). Until the
+ issue is resolved, the important thing for client developers to
+ understand is that some servers provide access through IMAP to more
+ than just the user's personal mailboxes, and, in fact, the user's
+ personal mailboxes may be "hidden" somewhere in the user's default
+ hierarchy. The client, therefore, should provide a setting wherein
+ the user can specify a prefix to be used when accessing mailboxes. If
+ the user's mailboxes are all in "~/mail/", for instance, then the
+ user can put that string in the prefix. The client would then put
+ the prefix in front of any name pattern in the LIST and LSUB
+ commands:
+
+ C: 001 LIST "" ~/mail/%
+
+ (See also "Reference Names in the LIST Command" below.)
+
+3.4.8. Creating Special-Use Mailboxes
+
+ It may seem at first that this is part of the namespace issue; it is
+ not, and is only indirectly related to it. A number of clients like
+ to create special-use mailboxes with particular names. Most
+ commonly, clients with a "trash folder" model of message deletion
+ want to create a mailbox with the name "Trash" or "Deleted". Some
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ clients want to create a "Drafts" mailbox, an "Outbox" mailbox, or a
+ "Sent Mail" mailbox. And so on. There are two major
+ interoperability problems with this practice:
+
+ 1. different clients may use different names for mailboxes with
+ similar functions (such as "Trash" and "Deleted"), or may manage
+ the same mailboxes in different ways, causing problems if a user
+ switches between clients and
+ 2. there is no guarantee that the server will allow the creation of
+ the desired mailbox.
+
+ The client developer is, therefore, well advised to consider
+ carefully the creation of any special-use mailboxes on the server,
+ and, further, the client must not require such mailbox creation -
+ that is, if you do decide to do this, you must handle gracefully the
+ failure of the CREATE command and behave reasonably when your
+ special-use mailboxes do not exist and can not be created.
+
+ In addition, the client developer should provide a convenient way for
+ the user to select the names for any special-use mailboxes, allowing
+ the user to make these names the same in all clients used and to put
+ them where the user wants them.
+
+3.4.9. Reference Names in the LIST Command
+
+ Many implementers of both clients and servers are confused by the
+ "reference name" on the LIST command. The reference name is intended
+ to be used in much the way a "cd" (change directory) command is used
+ on Unix, PC DOS, Windows, and OS/2 systems. That is, the mailbox
+ name is interpreted in much the same way as a file of that name would
+ be found if one had done a "cd" command into the directory specified
+ by the reference name. For example, in Unix we have the following:
+
+ > cd /u/jones/junk
+ > vi banana [file is "/u/jones/junk/banana"]
+ > vi stuff/banana [file is "/u/jones/junk/stuff/banana"]
+ > vi /etc/hosts [file is "/etc/hosts"]
+
+ In the past, there have been several interoperability problems with
+ this. First, while some IMAP servers are built on Unix or PC file
+ systems, many others are not, and the file system semantics do not
+ make sense in those configurations. Second, while some IMAP servers
+ expose the underlying file system to the clients, others allow access
+ only to the user's personal mailboxes, or to some other limited set
+ of files, making such file-system-like semantics less meaningful.
+ Third, because the IMAP spec leaves the interpretation of the
+ reference name as "implementation-dependent", in the past the various
+ server implementations handled it in vastly differing ways.
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ The following recommendations are the result of significant
+ operational experience, and are intended to maximize
+ interoperability.
+
+ Server implementations must implement the reference argument in a way
+ that matches the intended "change directory" operation as closely as
+ possible. As a minimum implementation, the reference argument may be
+ prepended to the mailbox name (while suppressing double delimiters;
+ see the next paragraph). Even servers that do not provide a way to
+ break out of the current hierarchy (see "breakout facility" below)
+ must provide a reasonable implementation of the reference argument,
+ as described here, so that they will interoperate with clients that
+ use it.
+
+ Server implementations that prepend the reference argument to the
+ mailbox name should insert a hierarchy delimiter between them, and
+ must not insert a second if one is already present:
+
+ C: A001 LIST ABC DEF
+ S: * LIST () "/" ABC/DEF <=== should do this
+ S: A001 OK done
+
+ C: A002 LIST ABC/ /DEF
+ S: * LIST () "/" ABC//DEF <=== must not do this
+ S: A002 OK done
+
+ On clients, the reference argument is chiefly used to implement a
+ "breakout facility", wherein the user may directly access a mailbox
+ outside the "current directory" hierarchy. Client implementations
+ should have an operational mode that does not use the reference
+ argument. This is to interoperate with older servers that did not
+ implement the reference argument properly. While it's a good idea to
+ give the user access to a breakout facility, clients that do not
+ intend to do so should not use the reference argument at all.
+
+ Client implementations should always place a trailing hierarchy
+ delimiter on the reference argument. This is because some servers
+ prepend the reference argument to the mailbox name without inserting
+ a hierarchy delimiter, while others do insert a hierarchy delimiter
+ if one is not already present. A client that puts the delimiter in
+ will work with both varieties of server.
+
+ Client implementations that implement a breakout facility should
+ allow the user to choose whether or not to use a leading hierarchy
+ delimiter on the mailbox argument. This is because the handling of a
+ leading mailbox hierarchy delimiter also varies from server to
+ server, and even between different mailstores on the same server. In
+ some cases, a leading hierarchy delimiter means "discard the
+
+
+
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+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ reference argument" (implementing the intended breakout facility),
+ thus:
+
+ C: A001 LIST ABC/ /DEF
+ S: * LIST () "/" /DEF
+ S: A001 OK done
+
+ In other cases, however, the two are catenated and the extra
+ hierarchy delimiter is discarded, thus:
+
+ C: A001 LIST ABC/ /DEF
+ S: * LIST () "/" ABC/DEF
+ S: A001 OK done
+
+ Client implementations must not assume that the server supports a
+ breakout facility, but may provide a way for the user to use one if
+ it is available. Any breakout facility should be exported to the
+ user interface. Note that there may be other "breakout" characters
+ besides the hierarchy delimiter (for instance, UNIX filesystem
+ servers are likely to use a leading "~" as well), and that their
+ interpretation is server-dependent.
+
+3.4.10. Mailbox Hierarchy Delimiters
+
+ The server's selection of what to use as a mailbox hierarchy
+ delimiter is a difficult one, involving several issues: What
+ characters do users expect to see? What characters can they enter
+ for a hierarchy delimiter if it is desired (or required) that the
+ user enter it? What character can be used for the hierarchy
+ delimiter, noting that the chosen character can not otherwise be used
+ in the mailbox name?
+
+ Because some interfaces show users the hierarchy delimiters or allow
+ users to enter qualified mailbox names containing them, server
+ implementations should use delimiter characters that users generally
+ expect to see as name separators. The most common characters used
+ for this are "/" (as in Unix file names), "\" (as in OS/2 and Windows
+ file names), and "." (as in news groups). There is little to choose
+ among these apart from what users may expect or what is dictated by
+ the underlying file system, if any. One consideration about using
+ "\" is that it's also a special character in the IMAP protocol. While
+ the use of other hierarchy delimiter characters is permissible, A
+ DESIGNER IS WELL ADVISED TO STAY WITH ONE FROM THIS SET unless the
+ server is intended for special purposes only. Implementers might be
+ thinking about using characters such as "-", "_", ";", "&", "#", "@",
+ and "!", but they should be aware of the surprise to the user as well
+ as of the effect on URLs and other external specifications (since
+ some of these characters have special meanings there). Also, a
+
+
+
+Leiba Informational [Page 19]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ server that uses "\" (and clients of such a server) must remember to
+ escape that character in quoted strings or to send literals instead.
+ Literals are recommended over escaped characters in quoted strings in
+ order to maintain compatibility with older IMAP versions that did not
+ allow escaped characters in quoted strings (but check the grammar to
+ see where literals are allowed):
+
+ C: 001 LIST "" {13}
+ S: + send literal
+ C: this\%\%\%\h*
+ S: * LIST () "\\" {27}
+ S: this\is\a\mailbox\hierarchy
+ S: 001 OK LIST complete
+
+ In any case, a server should not use normal alpha-numeric characters
+ (such as "X" or "0") as delimiters; a user would be very surprised to
+ find that "EXPENDITURES" actually represented a two-level hierarchy.
+ And a server should not use characters that are non-printable or
+ difficult or impossible to enter on a standard US keyboard. Control
+ characters, box-drawing characters, and characters from non-US
+ alphabets fit into this category. Their use presents
+ interoperability problems that are best avoided.
+
+ The UTF-7 encoding of mailbox names also raises questions about what
+ to do with the hierarchy delimiters in encoded names: do we encode
+ each hierarchy level and separate them with delimiters, or do we
+ encode the fully qualified name, delimiters and all? The answer for
+ IMAP is the former: encode each hierarchy level separately, and
+ insert delimiters between. This makes it particularly important not
+ to use as a hierarchy delimiter a character that might cause
+ confusion with IMAP's modified UTF-7 [UTF-7 and RFC-2060] encoding.
+
+ To repeat: a server should use "/", "\", or "." as its hierarchy
+ delimiter. The use of any other character is likely to cause
+ problems and is STRONGLY DISCOURAGED.
+
+3.4.11. ALERT Response Codes
+
+ The protocol spec is very clear on the matter of what to do with
+ ALERT response codes, and yet there are many clients that violate it
+ so it needs to be said anyway: "The human-readable text contains a
+ special alert that must be presented to the user in a fashion that
+ calls the user's attention to the message." That should be clear
+ enough, but I'll repeat it here: Clients must present ALERT text
+ clearly to the user.
+
+
+
+
+
+
+Leiba Informational [Page 20]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+3.4.12. Deleting Mailboxes
+
+ The protocol does not guarantee that a client may delete a mailbox
+ that is not empty, though on some servers it is permissible and is,
+ in fact, much faster than the alternative or deleting all the
+ messages from the client. If the client chooses to try to take
+ advantage of this possibility it must be prepared to use the other
+ method in the even that the more convenient one fails. Further, a
+ client should not try to delete the mailbox that it has selected, but
+ should first close that mailbox; some servers do not permit the
+ deletion of the selected mailbox.
+
+ That said, a server should permit the deletion of a non-empty
+ mailbox; there's little reason to pass this work on to the client.
+ Moreover, forbidding this prevents the deletion of a mailbox that for
+ some reason can not be opened or expunged, leading to possible
+ denial-of-service problems.
+
+ Example:
+
+ [User tells the client to delete mailbox BANANA, which is
+ currently selected...]
+ C: 008 CLOSE
+ S: 008 OK done
+ C: 009 DELETE BANANA
+ S: 009 NO Delete failed; mailbox is not empty.
+ C: 010 SELECT BANANA
+ S: * ... untagged SELECT responses
+ S: 010 OK done
+ C: 011 STORE 1:* +FLAGS.SILENT \DELETED
+ S: 011 OK done
+ C: 012 CLOSE
+ S: 012 OK done
+ C: 013 DELETE BANANA
+ S: 013 OK done
+
+3.5. A Word About Testing
+
+ Since the whole point of IMAP is interoperability, and since
+ interoperability can not be tested in a vacuum, the final
+ recommendation of this treatise is, "Test against EVERYTHING." Test
+ your client against every server you can get an account on. Test
+ your server with every client you can get your hands on. Many
+ clients make limited test versions available on the Web for the
+ downloading. Many server owners will give serious client developers
+ guest accounts for testing. Contact them and ask. NEVER assume that
+ because your client works with one or two servers, or because your
+ server does fine with one or two clients, you will interoperate well
+
+
+
+Leiba Informational [Page 21]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+ in general.
+
+ In particular, in addition to everything else, be sure to test
+ against the reference implementations: the PINE client, the
+ University of Washington server, and the Cyrus server.
+
+ See the following URLs on the web for more information here:
+
+ IMAP Products and Sources: http://www.imap.org/products.html
+ IMC MailConnect: http://www.imc.org/imc-mailconnect
+
+4. Security Considerations
+
+ This document describes behaviour of clients and servers that use the
+ IMAP4 protocol, and as such, has the same security considerations as
+ described in [RFC-2060].
+
+5. References
+
+ [RFC-2060] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+ [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC-2180] Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", RFC
+ 2180, July 1997.
+
+ [UTF-8] Yergeau, F., " UTF-8, a transformation format of Unicode
+ and ISO 10646", RFC 2044, October 1996.
+
+ [UTF-7] Goldsmith, D. and M. Davis, "UTF-7, a Mail-Safe
+ Transformation Format of Unicode", RFC 2152, May 1997.
+
+ [NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", Work in
+ Progress.
+
+6. Author's Address
+
+ Barry Leiba
+ IBM T.J. Watson Research Center
+ 30 Saw Mill River Road
+ Hawthorne, NY 10532
+
+ Phone: 1-914-784-7941
+ EMail: leiba@watson.ibm.com
+
+
+
+
+
+Leiba Informational [Page 22]
+
+RFC 2683 IMAP4 Implementation Recommendations September 1999
+
+
+7. Full Copyright Statement
+
+ Copyright (C) The Internet Society (1999). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Leiba Informational [Page 23]
+
diff --git a/imap/docs/rfc/rfc2971.txt b/imap/docs/rfc/rfc2971.txt
new file mode 100644
index 00000000..9e7264dc
--- /dev/null
+++ b/imap/docs/rfc/rfc2971.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group T. Showalter
+Request for Comments: 2971 Mirapoint, Inc.
+Category: Standards Track October 2000
+
+
+ IMAP4 ID extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2000). All Rights Reserved.
+
+Abstract
+
+ The ID extension to the Internet Message Access Protocol - Version
+ 4rev1 (IMAP4rev1) protocol allows the server and client to exchange
+ identification information on their implementation in order to make
+ bug reports and usage statistics more complete.
+
+1. Introduction
+
+ The IMAP4rev1 protocol described in [IMAP4rev1] provides a method for
+ accessing remote mail stores, but it provides no facility to
+ advertise what program a client or server uses to provide service.
+ This makes it difficult for implementors to get complete bug reports
+ from users, as it is frequently difficult to know what client or
+ server is in use.
+
+ Additionally, some sites may wish to assemble usage statistics based
+ on what clients are used, but in an an environment where users are
+ permitted to obtain and maintain their own clients this is difficult
+ to accomplish.
+
+ The ID command provides a facility to advertise information on what
+ programs are being used along with contact information (should bugs
+ ever occur).
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 1]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+2. Conventions Used in this Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [KEYWORDS].
+
+ The conventions used in this document are the same as specified in
+ [IMAP4rev1]. In examples, "C:" and "S:" indicate lines sent by the
+ client and server respectively. Line breaks have been inserted for
+ readability.
+
+3. Specification
+
+ The sole purpose of the ID extension is to enable clients and servers
+ to exchange information on their implementations for the purposes of
+ statistical analysis and problem determination.
+
+ This information is be submitted to a server by any client wishing to
+ provide information for statistical purposes, provided the server
+ advertises its willingness to take the information with the atom "ID"
+ included in the list of capabilities returned by the CAPABILITY
+ command.
+
+ Implementations MUST NOT make operational changes based on the data
+ sent as part of the ID command or response. The ID command is for
+ human consumption only, and is not to be used in improving the
+ performance of clients or servers.
+
+ This includes, but is not limited to, the following:
+
+ Servers MUST NOT attempt to work around client bugs by using
+ information from the ID command. Clients MUST NOT attempt to work
+ around server bugs based on the ID response.
+
+ Servers MUST NOT provide features to a client or otherwise
+ optimize for a particular client by using information from the ID
+ command. Clients MUST NOT provide features to a server or
+ otherwise optimize for a particular server based on the ID
+ response.
+
+ Servers MUST NOT deny access to or refuse service for a client
+ based on information from the ID command. Clients MUST NOT refuse
+ to operate or limit their operation with a server based on the ID
+ response.
+
+
+
+
+
+
+
+Showalter Standards Track [Page 2]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+ Rationale: It is imperative that this extension not supplant IMAP's
+ CAPABILITY mechanism with a ad-hoc approach where implementations
+ guess each other's features based on who they claim to be.
+
+ Implementations MUST NOT send false information in an ID command.
+
+ Implementations MAY send less information than they have available or
+ no information at all. Such behavior may be useful to preserve user
+ privacy. See Security Considerations, section 7.
+
+3.1. ID Command
+
+ Arguments: client parameter list or NIL
+
+ Responses: OPTIONAL untagged response: ID
+
+ Result: OK identification information accepted
+ BAD command unknown or arguments invalid
+
+ Implementation identification information is sent by the client with
+ the ID command.
+
+ This command is valid in any state.
+
+ The information sent is in the form of a list of field/value pairs.
+ Fields are permitted to be any IMAP4 string, and values are permitted
+ to be any IMAP4 string or NIL. A value of NIL indicates that the
+ client can not or will not specify this information. The client may
+ also send NIL instead of the list, indicating that it wants to send
+ no information, but would still accept a server response.
+
+ The available fields are defined in section 3.3.
+
+ Example: C: a023 ID ("name" "sodr" "version" "19.34" "vendor"
+ "Pink Floyd Music Limited")
+ S: * ID NIL
+ S: a023 OK ID completed
+
+3.2. ID Response
+
+ Contents: server parameter list
+
+ In response to an ID command issued by the client, the server replies
+ with a tagged response containing information on its implementation.
+ The format is the same as the client list.
+
+
+
+
+
+
+Showalter Standards Track [Page 3]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+ Example: C: a042 ID NIL
+ S: * ID ("name" "Cyrus" "version" "1.5" "os" "sunos"
+ "os-version" "5.5" "support-url"
+ "mailto:cyrus-bugs+@andrew.cmu.edu")
+ S: a042 OK ID command completed
+
+ A server MUST send a tagged ID response to an ID command. However, a
+ server MAY send NIL in place of the list.
+
+3.3. Defined Field Values
+
+ Any string may be sent as a field, but the following are defined to
+ describe certain values that might be sent. Implementations are free
+ to send none, any, or all of these. Strings are not case-sensitive.
+ Field strings MUST NOT be longer than 30 octets. Value strings MUST
+ NOT be longer than 1024 octets. Implementations MUST NOT send more
+ than 30 field-value pairs.
+
+ name Name of the program
+ version Version number of the program
+ os Name of the operating system
+ os-version Version of the operating system
+ vendor Vendor of the client/server
+ support-url URL to contact for support
+ address Postal address of contact/vendor
+ date Date program was released, specified as a date-time
+ in IMAP4rev1
+ command Command used to start the program
+ arguments Arguments supplied on the command line, if any
+ if any
+ environment Description of environment, i.e., UNIX environment
+ variables or Windows registry settings
+
+ Implementations MUST NOT use contact information to submit automatic
+ bug reports. Implementations may include information from an ID
+ response in a report automatically prepared, but are prohibited from
+ sending the report without user authorization.
+
+ It is preferable to find the name and version of the underlying
+ operating system at runtime in cases where this is possible.
+
+ Information sent via an ID response may violate user privacy. See
+ Security Considerations, section 7.
+
+ Implementations MUST NOT send the same field name more than once.
+
+
+
+
+
+
+Showalter Standards Track [Page 4]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+4. Formal Syntax
+
+ This syntax is intended to augment the grammar specified in
+ [IMAP4rev1] in order to provide for the ID command. This
+ specification uses the augmented Backus-Naur Form (BNF) notation as
+ used in [IMAP4rev1].
+
+ command_any ::= "CAPABILITY" / "LOGOUT" / "NOOP" / x_command / id
+ ;; adds id command to command_any in [IMAP4rev1]
+
+ id ::= "ID" SPACE id_params_list
+
+ id_response ::= "ID" SPACE id_params_list
+
+ id_params_list ::= "(" #(string SPACE nstring) ")" / nil
+ ;; list of field value pairs
+
+ response_data ::= "*" SPACE (resp_cond_state / resp_cond_bye /
+ mailbox_data / message_data / capability_data / id_response)
+
+5. Use of the ID extension with Firewalls and Other Intermediaries
+
+ There exist proxies, firewalls, and other intermediary systems that
+ can intercept an IMAP session and make changes to the data exchanged
+ in the session. Such intermediaries are not anticipated by the IMAP4
+ protocol design and are not within the scope of the IMAP4 standard.
+ However, in order for the ID command to be useful in the presence of
+ such intermediaries, those intermediaries need to take special note
+ of the ID command and response. In particular, if an intermediary
+ changes any part of the IMAP session it must also change the ID
+ command to advertise its presence.
+
+ A firewall MAY act to block transmission of specific information
+ fields in the ID command and response that it believes reveal
+ information that could expose a security vulnerability. However, a
+ firewall SHOULD NOT disable the extension, when present, entirely,
+ and SHOULD NOT unconditionally remove either the client or server
+ list.
+
+ Finally, it should be noted that a firewall, when handling a
+ CAPABILITY response, MUST NOT allow the names of extensions to be
+ returned to the client that the firewall has no knowledge of.
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 5]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+6. References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, March 1997.
+
+ [IMAP4rev1] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, October 1996.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
+ Text Messages", STD 11, RFC 822, August 1982.
+
+7. Security Considerations
+
+ This extension has the danger of violating the privacy of users if
+ misused. Clients and servers should notify users that they implement
+ and enable the ID command.
+
+ It is highly desirable that implementations provide a method of
+ disabling ID support, perhaps by not sending ID at all, or by sending
+ NIL as the argument to the ID command or response.
+
+ Implementors must exercise extreme care in adding fields sent as part
+ of an ID command or response. Some fields, including a processor ID
+ number, Ethernet address, or other unique (or mostly unique)
+ identifier allow tracking of users in ways that violate user privacy
+ expectations.
+
+ Having implementation information of a given client or server may
+ make it easier for an attacker to gain unauthorized access due to
+ security holes.
+
+ Since this command includes arbitrary data and does not require the
+ user to authenticate, server implementations are cautioned to guard
+ against an attacker sending arbitrary garbage data in order to fill
+ up the ID log. In particular, if a server naively logs each ID
+ command to disk without inspecting it, an attacker can simply fire up
+ thousands of connections and send a few kilobytes of random data.
+ Servers have to guard against this. Methods include truncating
+ abnormally large responses; collating responses by storing only a
+ single copy, then keeping a counter of the number of times that
+ response has been seen; keeping only particularly interesting parts
+ of responses; and only logging responses of users who actually log
+ in.
+
+ Security is affected by firewalls which modify the IMAP protocol
+ stream; see section 5, Use of the ID Extension with Firewalls and
+ Other Intermediaries, for more information.
+
+
+
+
+Showalter Standards Track [Page 6]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+8. Author's Address
+
+ Tim Showalter
+ Mirapoint, Inc.
+ 909 Hermosa Ct.
+ Sunnyvale, CA 94095
+
+ EMail: tjs@mirapoint.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 7]
+
+RFC 2971 IMAP4 ID extension October 2000
+
+
+9. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2000). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Showalter Standards Track [Page 8]
+
diff --git a/imap/docs/rfc/rfc3348.txt b/imap/docs/rfc/rfc3348.txt
new file mode 100644
index 00000000..500871cc
--- /dev/null
+++ b/imap/docs/rfc/rfc3348.txt
@@ -0,0 +1,339 @@
+
+
+
+
+
+
+Network Working Group M. Gahrns
+Request for Comments: 3348 R. Cheng
+Category: Informational Microsoft
+ July 2002
+
+
+ The Internet Message Action Protocol (IMAP4)
+ Child Mailbox Extension
+
+Status of this Memo
+
+ This memo provides information for the Internet community. It does
+ not specify an Internet standard of any kind. Distribution of this
+ memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+Abstract
+
+ The Internet Message Action Protocol (IMAP4) CHILDREN extension
+ provides a mechanism for a client to efficiently determine if a
+ particular mailbox has children, without issuing a LIST "" * or a
+ LIST "" % for each mailbox.
+
+1. Conventions used in this document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. If such lines are wrapped without a new "C:" or
+ "S:" label, then the wrapping is for editorial clarity and is not
+ part of the command.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC-2119].
+
+2. Introduction and Overview
+
+ Many IMAP4 [RFC-2060] clients present to the user a hierarchical view
+ of the mailboxes that a user has access to. Rather than initially
+ presenting to the user the entire mailbox hierarchy, it is often
+ preferable to show to the user a collapsed outline list of the
+ mailbox hierarchy (particularly if there is a large number of
+ mailboxes). The user can then expand the collapsed outline hierarchy
+ as needed. It is common to include within the collapsed hierarchy a
+
+
+
+
+
+Gahrns, et al. Informational [Page 1]
+
+RFC 3348 IMAP4 Child Mailbox Extension July 2002
+
+
+ visual clue (such as a "+") to indicate that there are child
+ mailboxes under a particular mailbox. When the visual clue is
+ clicked the hierarchy list is expanded to show the child mailboxes.
+
+ Several IMAP vendors implemented this proposal, and it is proposed to
+ document this behavior and functionality as an Informational RFC.
+
+ There is interest in addressing the general extensibility of the IMAP
+ LIST command through an IMAP LIST Extension draft. Similar
+ functionality to the \HasChildren and \HasNoChildren flags could be
+ incorporated into this new LIST Extension. It is proposed that the
+ more general LIST Extension draft proceed on the standards track with
+ this proposal being relegated to informational status only.
+
+ If the functionality of the \HasChildren and \HasNoChildren flags
+ were incorporated into a more general LIST extension, this would have
+ the advantage that a client could then have the opportunity to
+ request whether or not the server should return this information.
+ This would be an advantage over the current draft for servers where
+ this information is expensive to compute, since the server would only
+ need to compute the information when it knew that the client
+ requesting the information was able to consume it.
+
+3. Requirements
+
+ IMAP4 servers that support this extension MUST list the keyword
+ CHILDREN in their CAPABILITY response.
+
+ The CHILDREN extension defines two new attributes that MAY be
+ returned within a LIST response.
+
+ \HasChildren - The presence of this attribute indicates that the
+ mailbox has child mailboxes.
+
+ Servers SHOULD NOT return \HasChildren if child mailboxes exist, but
+ none will be displayed to the current user in a LIST response (as
+ should be the case where child mailboxes exist, but a client does not
+ have permissions to access them.) In this case, \HasNoChildren
+ SHOULD be used.
+
+ In many cases, however, a server may not be able to efficiently
+ compute whether a user has access to all child mailboxes, or multiple
+ users may be accessing the same account and simultaneously changing
+ the mailbox hierarchy. As such a client MUST be prepared to accept
+ the \HasChildren attribute as a hint. That is, a mailbox MAY be
+ flagged with the \HasChildren attribute, but no child mailboxes will
+ appear in a subsequent LIST response.
+
+
+
+
+Gahrns, et al. Informational [Page 2]
+
+RFC 3348 IMAP4 Child Mailbox Extension July 2002
+
+
+ Example 3.1:
+ ============
+
+ /*** Consider a server that has the following mailbox hierarchy:
+
+ INBOX
+ ITEM_1
+ ITEM_1A
+ ITEM_2
+ TOP_SECRET
+
+ Where INBOX, ITEM_1 and ITEM_2 are top level mailboxes. ITEM_1A is a
+ child mailbox of ITEM_1 and TOP_SECRET is a child mailbox of ITEM_2
+ that the currently logged on user does NOT have access to.
+
+ Note that in this case, the server is not able to efficiently compute
+ access rights to child mailboxes and responds with a \HasChildren
+ attribute for mailbox ITEM_2, even though ITEM_2/TOP_SECRET does not
+ appear in the list response. ***/
+
+ C: A001 LIST "" *
+ S: * LIST (\HasNoChildren) "/" INBOX
+ S: * LIST (\HasChildren) "/" ITEM_1
+ S: * LIST (\HasNoChildren) "/" ITEM_1/ITEM_1A
+ S: * LIST (\HasChildren) "/" ITEM_2
+ S: A001 OK LIST Completed
+
+ \HasNoChildren - The presence of this attribute indicates that the
+ mailbox has NO child mailboxes that are accessible to the currently
+ authenticated user. If a mailbox has the \Noinferiors attribute, the
+ \HasNoChildren attribute is redundant and SHOULD be omitted in the
+ LIST response.
+
+ In some instances a server that supports the CHILDREN extension MAY
+ NOT be able to determine whether a mailbox has children. For example
+ it may have difficulty determining whether there are child mailboxes
+ when LISTing mailboxes while operating in a particular namespace.
+
+ In these cases, a server MAY exclude both the \HasChildren and
+ \HasNoChildren attributes in the LIST response. As such, a client
+ can not make any assumptions about whether a mailbox has children
+ based upon the absence of a single attribute.
+
+ It is an error for the server to return both a \HasChildren and a
+ \HasNoChildren attribute in a LIST response.
+
+
+
+
+
+
+Gahrns, et al. Informational [Page 3]
+
+RFC 3348 IMAP4 Child Mailbox Extension July 2002
+
+
+ It is an error for the server to return both a \HasChildren and a
+ \NoInferiors attribute in a LIST response.
+
+ Note: the \HasNoChildren attribute should not be confused with the
+ IMAP4 [RFC-2060] defined attribute \Noinferiors which indicates that
+ no child mailboxes exist now and none can be created in the future.
+
+ The \HasChildren and \HasNoChildren attributes might not be returned
+ in response to a LSUB response. Many servers maintain a simple
+ mailbox subscription list that is not updated when the underlying
+ mailbox structure is changed. A client MUST NOT assume that
+ hierarchy information will be maintained in the subscription list.
+
+ RLIST is a command defined in [RFC-2193] that includes in a LIST
+ response mailboxes that are accessible only via referral. That is, a
+ client must explicitly issue an RLIST command to see a list of these
+ mailboxes. Thus in the case where a mailbox has child mailboxes that
+ are available only via referral, the mailboxes would appear as
+ \HasNoChildren in response to the LIST command, and \HasChildren in
+ response to the RLIST command.
+
+5. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) as described in [ABNF].
+
+ Two new mailbox attributes are defined as flag_extensions to the
+ IMAP4 mailbox_list response:
+
+ HasChildren = "\HasChildren"
+
+ HasNoChildren = "\HasNoChildren"
+
+6. Security Considerations
+
+ This extension provides a client a more efficient means of
+ determining whether a particular mailbox has children. If a mailbox
+ has children, but the currently authenticated user does not have
+ access to any of them, the server SHOULD respond with a
+ \HasNoChildren attribute. In many cases, however, a server may not
+ be able to efficiently compute whether a user has access to all child
+ mailboxes. If such a server responds with a \HasChildren attribute,
+ when in fact the currently authenticated user does not have access to
+ any child mailboxes, potentially more information is conveyed about
+ the mailbox than intended. A server designed with such levels of
+ security in mind SHOULD NOT attach the \HasChildren attribute to a
+ mailbox unless the server is certain that the user has access to at
+ least one of the child mailboxes.
+
+
+
+Gahrns, et al. Informational [Page 4]
+
+RFC 3348 IMAP4 Child Mailbox Extension July 2002
+
+
+7. References
+
+ [RFC-2060] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 2060, December 1996.
+
+ [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC-2234] Crocker, D. and P. Overell, Editors, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+ [RFC-2193] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193, September
+ 1997.
+
+8. Acknowledgments
+
+ The authors would like to thank the participants of several IMC Mail
+ Connect events for their input when this idea was originally
+ presented and refined.
+
+9. Author's Address
+
+ Mike Gahrns
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98052
+ Phone: (425) 936-9833
+ EMail: mikega@microsoft.com
+
+ Raymond Cheng
+ Microsoft
+ One Microsoft Way
+ Redmond, WA, 98052
+ Phone: (425) 703-4913
+ EMail: raych@microsoft.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns, et al. Informational [Page 5]
+
+RFC 3348 IMAP4 Child Mailbox Extension July 2002
+
+
+10. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2002). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gahrns, et al. Informational [Page 6]
+
diff --git a/imap/docs/rfc/rfc3501.txt b/imap/docs/rfc/rfc3501.txt
new file mode 100644
index 00000000..6f470dd1
--- /dev/null
+++ b/imap/docs/rfc/rfc3501.txt
@@ -0,0 +1,6052 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 3501 University of Washington
+Obsoletes: 2060 March 2003
+Category: Standards Track
+
+
+ INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1)
+ allows a client to access and manipulate electronic mail messages on
+ a server. IMAP4rev1 permits manipulation of mailboxes (remote
+ message folders) in a way that is functionally equivalent to local
+ folders. IMAP4rev1 also provides the capability for an offline
+ client to resynchronize with the server.
+
+ IMAP4rev1 includes operations for creating, deleting, and renaming
+ mailboxes, checking for new messages, permanently removing messages,
+ setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching,
+ and selective fetching of message attributes, texts, and portions
+ thereof. Messages in IMAP4rev1 are accessed by the use of numbers.
+ These numbers are either message sequence numbers or unique
+ identifiers.
+
+ IMAP4rev1 supports a single server. A mechanism for accessing
+ configuration information to support multiple IMAP4rev1 servers is
+ discussed in RFC 2244.
+
+ IMAP4rev1 does not specify a means of posting mail; this function is
+ handled by a mail transfer protocol such as RFC 2821.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Table of Contents
+
+ IMAP4rev1 Protocol Specification ................................ 4
+ 1. How to Read This Document ............................... 4
+ 1.1. Organization of This Document ........................... 4
+ 1.2. Conventions Used in This Document ....................... 4
+ 1.3. Special Notes to Implementors ........................... 5
+ 2. Protocol Overview ....................................... 6
+ 2.1. Link Level .............................................. 6
+ 2.2. Commands and Responses .................................. 6
+ 2.2.1. Client Protocol Sender and Server Protocol Receiver ..... 6
+ 2.2.2. Server Protocol Sender and Client Protocol Receiver ..... 7
+ 2.3. Message Attributes ...................................... 8
+ 2.3.1. Message Numbers ......................................... 8
+ 2.3.1.1. Unique Identifier (UID) Message Attribute ....... 8
+ 2.3.1.2. Message Sequence Number Message Attribute ....... 10
+ 2.3.2. Flags Message Attribute ................................. 11
+ 2.3.3. Internal Date Message Attribute ......................... 12
+ 2.3.4. [RFC-2822] Size Message Attribute ....................... 12
+ 2.3.5. Envelope Structure Message Attribute .................... 12
+ 2.3.6. Body Structure Message Attribute ........................ 12
+ 2.4. Message Texts ........................................... 13
+ 3. State and Flow Diagram .................................. 13
+ 3.1. Not Authenticated State ................................. 13
+ 3.2. Authenticated State ..................................... 13
+ 3.3. Selected State .......................................... 13
+ 3.4. Logout State ............................................ 14
+ 4. Data Formats ............................................ 16
+ 4.1. Atom .................................................... 16
+ 4.2. Number .................................................. 16
+ 4.3. String .................................................. 16
+ 4.3.1. 8-bit and Binary Strings ................................ 17
+ 4.4. Parenthesized List ...................................... 17
+ 4.5. NIL ..................................................... 17
+ 5. Operational Considerations .............................. 18
+ 5.1. Mailbox Naming .......................................... 18
+ 5.1.1. Mailbox Hierarchy Naming ................................ 19
+ 5.1.2. Mailbox Namespace Naming Convention ..................... 19
+ 5.1.3. Mailbox International Naming Convention ................. 19
+ 5.2. Mailbox Size and Message Status Updates ................. 21
+ 5.3. Response when no Command in Progress .................... 21
+ 5.4. Autologout Timer ........................................ 22
+ 5.5. Multiple Commands in Progress ........................... 22
+ 6. Client Commands ........................................ 23
+ 6.1. Client Commands - Any State ............................ 24
+ 6.1.1. CAPABILITY Command ..................................... 24
+ 6.1.2. NOOP Command ........................................... 25
+ 6.1.3. LOGOUT Command ......................................... 26
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 6.2. Client Commands - Not Authenticated State .............. 26
+ 6.2.1. STARTTLS Command ....................................... 27
+ 6.2.2. AUTHENTICATE Command ................................... 28
+ 6.2.3. LOGIN Command .......................................... 30
+ 6.3. Client Commands - Authenticated State .................. 31
+ 6.3.1. SELECT Command ......................................... 32
+ 6.3.2. EXAMINE Command ........................................ 34
+ 6.3.3. CREATE Command ......................................... 34
+ 6.3.4. DELETE Command ......................................... 35
+ 6.3.5. RENAME Command ......................................... 37
+ 6.3.6. SUBSCRIBE Command ...................................... 39
+ 6.3.7. UNSUBSCRIBE Command .................................... 39
+ 6.3.8. LIST Command ........................................... 40
+ 6.3.9. LSUB Command ........................................... 43
+ 6.3.10. STATUS Command ......................................... 44
+ 6.3.11. APPEND Command ......................................... 46
+ 6.4. Client Commands - Selected State ....................... 47
+ 6.4.1. CHECK Command .......................................... 47
+ 6.4.2. CLOSE Command .......................................... 48
+ 6.4.3. EXPUNGE Command ........................................ 49
+ 6.4.4. SEARCH Command ......................................... 49
+ 6.4.5. FETCH Command .......................................... 54
+ 6.4.6. STORE Command .......................................... 58
+ 6.4.7. COPY Command ........................................... 59
+ 6.4.8. UID Command ............................................ 60
+ 6.5. Client Commands - Experimental/Expansion ............... 62
+ 6.5.1. X<atom> Command ........................................ 62
+ 7. Server Responses ....................................... 62
+ 7.1. Server Responses - Status Responses .................... 63
+ 7.1.1. OK Response ............................................ 65
+ 7.1.2. NO Response ............................................ 66
+ 7.1.3. BAD Response ........................................... 66
+ 7.1.4. PREAUTH Response ....................................... 67
+ 7.1.5. BYE Response ........................................... 67
+ 7.2. Server Responses - Server and Mailbox Status ........... 68
+ 7.2.1. CAPABILITY Response .................................... 68
+ 7.2.2. LIST Response .......................................... 69
+ 7.2.3. LSUB Response .......................................... 70
+ 7.2.4 STATUS Response ........................................ 70
+ 7.2.5. SEARCH Response ........................................ 71
+ 7.2.6. FLAGS Response ......................................... 71
+ 7.3. Server Responses - Mailbox Size ........................ 71
+ 7.3.1. EXISTS Response ........................................ 71
+ 7.3.2. RECENT Response ........................................ 72
+ 7.4. Server Responses - Message Status ...................... 72
+ 7.4.1. EXPUNGE Response ....................................... 72
+ 7.4.2. FETCH Response ......................................... 73
+ 7.5. Server Responses - Command Continuation Request ........ 79
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 8. Sample IMAP4rev1 connection ............................ 80
+ 9. Formal Syntax .......................................... 81
+ 10. Author's Note .......................................... 92
+ 11. Security Considerations ................................ 92
+ 11.1. STARTTLS Security Considerations ....................... 92
+ 11.2. Other Security Considerations .......................... 93
+ 12. IANA Considerations .................................... 94
+ Appendices ..................................................... 95
+ A. References ............................................. 95
+ B. Changes from RFC 2060 .................................. 97
+ C. Key Word Index ......................................... 103
+ Author's Address ............................................... 107
+ Full Copyright Statement ....................................... 108
+
+IMAP4rev1 Protocol Specification
+
+1. How to Read This Document
+
+1.1. Organization of This Document
+
+ This document is written from the point of view of the implementor of
+ an IMAP4rev1 client or server. Beyond the protocol overview in
+ section 2, it is not optimized for someone trying to understand the
+ operation of the protocol. The material in sections 3 through 5
+ provides the general context and definitions with which IMAP4rev1
+ operates.
+
+ Sections 6, 7, and 9 describe the IMAP commands, responses, and
+ syntax, respectively. The relationships among these are such that it
+ is almost impossible to understand any of them separately. In
+ particular, do not attempt to deduce command syntax from the command
+ section alone; instead refer to the Formal Syntax section.
+
+1.2. Conventions Used in This Document
+
+ "Conventions" are basic principles or procedures. Document
+ conventions are noted in this section.
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+ be interpreted as described in [KEYWORDS].
+
+ The word "can" (not "may") is used to refer to a possible
+ circumstance or situation, as opposed to an optional facility of the
+ protocol.
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ "User" is used to refer to a human user, whereas "client" refers to
+ the software being run by the user.
+
+ "Connection" refers to the entire sequence of client/server
+ interaction from the initial establishment of the network connection
+ until its termination.
+
+ "Session" refers to the sequence of client/server interaction from
+ the time that a mailbox is selected (SELECT or EXAMINE command) until
+ the time that selection ends (SELECT or EXAMINE of another mailbox,
+ CLOSE command, or connection termination).
+
+ Characters are 7-bit US-ASCII unless otherwise specified. Other
+ character sets are indicated using a "CHARSET", as described in
+ [MIME-IMT] and defined in [CHARSET]. CHARSETs have important
+ additional semantics in addition to defining character set; refer to
+ these documents for more detail.
+
+ There are several protocol conventions in IMAP. These refer to
+ aspects of the specification which are not strictly part of the IMAP
+ protocol, but reflect generally-accepted practice. Implementations
+ need to be aware of these conventions, and avoid conflicts whether or
+ not they implement the convention. For example, "&" may not be used
+ as a hierarchy delimiter since it conflicts with the Mailbox
+ International Naming Convention, and other uses of "&" in mailbox
+ names are impacted as well.
+
+1.3. Special Notes to Implementors
+
+ Implementors of the IMAP protocol are strongly encouraged to read the
+ IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
+ conjunction with this document, to help understand the intricacies of
+ this protocol and how best to build an interoperable product.
+
+ IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
+ unpublished IMAP2bis protocols. IMAP4rev1 is largely compatible with
+ the IMAP4 protocol described in RFC 1730; the exception being in
+ certain facilities added in RFC 1730 that proved problematic and were
+ subsequently removed. In the course of the evolution of IMAP4rev1,
+ some aspects in the earlier protocols have become obsolete. Obsolete
+ commands, responses, and data formats which an IMAP4rev1
+ implementation can encounter when used with an earlier implementation
+ are described in [IMAP-OBSOLETE].
+
+ Other compatibility issues with IMAP2bis, the most common variant of
+ the earlier protocol, are discussed in [IMAP-COMPAT]. A full
+ discussion of compatibility issues with rare (and presumed extinct)
+
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
+ primarily of historical interest.
+
+ IMAP was originally developed for the older [RFC-822] standard, and
+ as a consequence several fetch items in IMAP incorporate "RFC822" in
+ their name. With the exception of RFC822.SIZE, there are more modern
+ replacements; for example, the modern version of RFC822.HEADER is
+ BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a
+ reference to the updated [RFC-2822] standard.
+
+2. Protocol Overview
+
+2.1. Link Level
+
+ The IMAP4rev1 protocol assumes a reliable data stream such as that
+ provided by TCP. When TCP is used, an IMAP4rev1 server listens on
+ port 143.
+
+2.2. Commands and Responses
+
+ An IMAP4rev1 connection consists of the establishment of a
+ client/server network connection, an initial greeting from the
+ server, and client/server interactions. These client/server
+ interactions consist of a client command, server data, and a server
+ completion result response.
+
+ All interactions transmitted by client and server are in the form of
+ lines, that is, strings that end with a CRLF. The protocol receiver
+ of an IMAP4rev1 client or server is either reading a line, or is
+ reading a sequence of octets with a known count followed by a line.
+
+2.2.1. Client Protocol Sender and Server Protocol Receiver
+
+ The client command begins an operation. Each client command is
+ prefixed with an identifier (typically a short alphanumeric string,
+ e.g., A0001, A0002, etc.) called a "tag". A different tag is
+ generated by the client for each command.
+
+ Clients MUST follow the syntax outlined in this specification
+ strictly. It is a syntax error to send a command with missing or
+ extraneous spaces or arguments.
+
+ There are two cases in which a line from the client does not
+ represent a complete command. In one case, a command argument is
+ quoted with an octet count (see the description of literal in String
+ under Data Formats); in the other case, the command arguments require
+ server feedback (see the AUTHENTICATE command). In either case, the
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ server sends a command continuation request response if it is ready
+ for the octets (if appropriate) and the remainder of the command.
+ This response is prefixed with the token "+".
+
+ Note: If instead, the server detected an error in the
+ command, it sends a BAD completion response with a tag
+ matching the command (as described below) to reject the
+ command and prevent the client from sending any more of the
+ command.
+
+ It is also possible for the server to send a completion
+ response for some other command (if multiple commands are
+ in progress), or untagged data. In either case, the
+ command continuation request is still pending; the client
+ takes the appropriate action for the response, and reads
+ another response from the server. In all cases, the client
+ MUST send a complete command (including receiving all
+ command continuation request responses and command
+ continuations for the command) before initiating a new
+ command.
+
+ The protocol receiver of an IMAP4rev1 server reads a command line
+ from the client, parses the command and its arguments, and transmits
+ server data and a server command completion result response.
+
+2.2.2. Server Protocol Sender and Client Protocol Receiver
+
+ Data transmitted by the server to the client and status responses
+ that do not indicate command completion are prefixed with the token
+ "*", and are called untagged responses.
+
+ Server data MAY be sent as a result of a client command, or MAY be
+ sent unilaterally by the server. There is no syntactic difference
+ between server data that resulted from a specific command and server
+ data that were sent unilaterally.
+
+ The server completion result response indicates the success or
+ failure of the operation. It is tagged with the same tag as the
+ client command which began the operation. Thus, if more than one
+ command is in progress, the tag in a server completion response
+ identifies the command to which the response applies. There are
+ three possible server completion responses: OK (indicating success),
+ NO (indicating failure), or BAD (indicating a protocol error such as
+ unrecognized command or command syntax error).
+
+ Servers SHOULD enforce the syntax outlined in this specification
+ strictly. Any client command with a protocol syntax error, including
+ (but not limited to) missing or extraneous spaces or arguments,
+
+
+
+Crispin Standards Track [Page 7]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SHOULD be rejected, and the client given a BAD server completion
+ response.
+
+ The protocol receiver of an IMAP4rev1 client reads a response line
+ from the server. It then takes action on the response based upon the
+ first token of the response, which can be a tag, a "*", or a "+".
+
+ A client MUST be prepared to accept any server response at all times.
+ This includes server data that was not requested. Server data SHOULD
+ be recorded, so that the client can reference its recorded copy
+ rather than sending a command to the server to request the data. In
+ the case of certain server data, the data MUST be recorded.
+
+ This topic is discussed in greater detail in the Server Responses
+ section.
+
+2.3. Message Attributes
+
+ In addition to message text, each message has several attributes
+ associated with it. These attributes can be retrieved individually
+ or in conjunction with other attributes or message texts.
+
+2.3.1. Message Numbers
+
+ Messages in IMAP4rev1 are accessed by one of two numbers; the unique
+ identifier or the message sequence number.
+
+
+2.3.1.1. Unique Identifier (UID) Message Attribute
+
+ A 32-bit value assigned to each message, which when used with the
+ unique identifier validity value (see below) forms a 64-bit value
+ that MUST NOT refer to any other message in the mailbox or any
+ subsequent mailbox with the same name forever. Unique identifiers
+ are assigned in a strictly ascending fashion in the mailbox; as each
+ message is added to the mailbox it is assigned a higher UID than the
+ message(s) which were added previously. Unlike message sequence
+ numbers, unique identifiers are not necessarily contiguous.
+
+ The unique identifier of a message MUST NOT change during the
+ session, and SHOULD NOT change between sessions. Any change of
+ unique identifiers between sessions MUST be detectable using the
+ UIDVALIDITY mechanism discussed below. Persistent unique identifiers
+ are required for a client to resynchronize its state from a previous
+ session with the server (e.g., disconnected or offline access
+ clients); this is discussed further in [IMAP-DISC].
+
+
+
+
+
+Crispin Standards Track [Page 8]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Associated with every mailbox are two values which aid in unique
+ identifier handling: the next unique identifier value and the unique
+ identifier validity value.
+
+ The next unique identifier value is the predicted value that will be
+ assigned to a new message in the mailbox. Unless the unique
+ identifier validity also changes (see below), the next unique
+ identifier value MUST have the following two characteristics. First,
+ the next unique identifier value MUST NOT change unless new messages
+ are added to the mailbox; and second, the next unique identifier
+ value MUST change whenever new messages are added to the mailbox,
+ even if those new messages are subsequently expunged.
+
+ Note: The next unique identifier value is intended to
+ provide a means for a client to determine whether any
+ messages have been delivered to the mailbox since the
+ previous time it checked this value. It is not intended to
+ provide any guarantee that any message will have this
+ unique identifier. A client can only assume, at the time
+ that it obtains the next unique identifier value, that
+ messages arriving after that time will have a UID greater
+ than or equal to that value.
+
+ The unique identifier validity value is sent in a UIDVALIDITY
+ response code in an OK untagged response at mailbox selection time.
+ If unique identifiers from an earlier session fail to persist in this
+ session, the unique identifier validity value MUST be greater than
+ the one used in the earlier session.
+
+ Note: Ideally, unique identifiers SHOULD persist at all
+ times. Although this specification recognizes that failure
+ to persist can be unavoidable in certain server
+ environments, it STRONGLY ENCOURAGES message store
+ implementation techniques that avoid this problem. For
+ example:
+
+ 1) Unique identifiers MUST be strictly ascending in the
+ mailbox at all times. If the physical message store is
+ re-ordered by a non-IMAP agent, this requires that the
+ unique identifiers in the mailbox be regenerated, since
+ the former unique identifiers are no longer strictly
+ ascending as a result of the re-ordering.
+
+ 2) If the message store has no mechanism to store unique
+ identifiers, it must regenerate unique identifiers at
+ each session, and each session must have a unique
+ UIDVALIDITY value.
+
+
+
+
+Crispin Standards Track [Page 9]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 3) If the mailbox is deleted and a new mailbox with the
+ same name is created at a later date, the server must
+ either keep track of unique identifiers from the
+ previous instance of the mailbox, or it must assign a
+ new UIDVALIDITY value to the new instance of the
+ mailbox. A good UIDVALIDITY value to use in this case
+ is a 32-bit representation of the creation date/time of
+ the mailbox. It is alright to use a constant such as
+ 1, but only if it guaranteed that unique identifiers
+ will never be reused, even in the case of a mailbox
+ being deleted (or renamed) and a new mailbox by the
+ same name created at some future time.
+
+ 4) The combination of mailbox name, UIDVALIDITY, and UID
+ must refer to a single immutable message on that server
+ forever. In particular, the internal date, [RFC-2822]
+ size, envelope, body structure, and message texts
+ (RFC822, RFC822.HEADER, RFC822.TEXT, and all BODY[...]
+ fetch data items) must never change. This does not
+ include message numbers, nor does it include attributes
+ that can be set by a STORE command (e.g., FLAGS).
+
+
+2.3.1.2. Message Sequence Number Message Attribute
+
+ A relative position from 1 to the number of messages in the mailbox.
+ This position MUST be ordered by ascending unique identifier. As
+ each new message is added, it is assigned a message sequence number
+ that is 1 higher than the number of messages in the mailbox before
+ that new message was added.
+
+ Message sequence numbers can be reassigned during the session. For
+ example, when a message is permanently removed (expunged) from the
+ mailbox, the message sequence number for all subsequent messages is
+ decremented. The number of messages in the mailbox is also
+ decremented. Similarly, a new message can be assigned a message
+ sequence number that was once held by some other message prior to an
+ expunge.
+
+ In addition to accessing messages by relative position in the
+ mailbox, message sequence numbers can be used in mathematical
+ calculations. For example, if an untagged "11 EXISTS" is received,
+ and previously an untagged "8 EXISTS" was received, three new
+ messages have arrived with message sequence numbers of 9, 10, and 11.
+ Another example, if message 287 in a 523 message mailbox has UID
+ 12345, there are exactly 286 messages which have lesser UIDs and 236
+ messages which have greater UIDs.
+
+
+
+
+Crispin Standards Track [Page 10]
+
+RFC 3501 IMAPv4 March 2003
+
+
+2.3.2. Flags Message Attribute
+
+ A list of zero or more named tokens associated with the message. A
+ flag is set by its addition to this list, and is cleared by its
+ removal. There are two types of flags in IMAP4rev1. A flag of
+ either type can be permanent or session-only.
+
+ A system flag is a flag name that is pre-defined in this
+ specification. All system flags begin with "\". Certain system
+ flags (\Deleted and \Seen) have special semantics described
+ elsewhere. The currently-defined system flags are:
+
+ \Seen
+ Message has been read
+
+ \Answered
+ Message has been answered
+
+ \Flagged
+ Message is "flagged" for urgent/special attention
+
+ \Deleted
+ Message is "deleted" for removal by later EXPUNGE
+
+ \Draft
+ Message has not completed composition (marked as a draft).
+
+ \Recent
+ Message is "recently" arrived in this mailbox. This session
+ is the first session to have been notified about this
+ message; if the session is read-write, subsequent sessions
+ will not see \Recent set for this message. This flag can not
+ be altered by the client.
+
+ If it is not possible to determine whether or not this
+ session is the first session to be notified about a message,
+ then that message SHOULD be considered recent.
+
+ If multiple connections have the same mailbox selected
+ simultaneously, it is undefined which of these connections
+ will see newly-arrived messages with \Recent set and which
+ will see it without \Recent set.
+
+ A keyword is defined by the server implementation. Keywords do not
+ begin with "\". Servers MAY permit the client to define new keywords
+ in the mailbox (see the description of the PERMANENTFLAGS response
+ code for more information).
+
+
+
+
+Crispin Standards Track [Page 11]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A flag can be permanent or session-only on a per-flag basis.
+ Permanent flags are those which the client can add or remove from the
+ message flags permanently; that is, concurrent and subsequent
+ sessions will see any change in permanent flags. Changes to session
+ flags are valid only in that session.
+
+ Note: The \Recent system flag is a special case of a
+ session flag. \Recent can not be used as an argument in a
+ STORE or APPEND command, and thus can not be changed at
+ all.
+
+2.3.3. Internal Date Message Attribute
+
+ The internal date and time of the message on the server. This
+ is not the date and time in the [RFC-2822] header, but rather a
+ date and time which reflects when the message was received. In
+ the case of messages delivered via [SMTP], this SHOULD be the
+ date and time of final delivery of the message as defined by
+ [SMTP]. In the case of messages delivered by the IMAP4rev1 COPY
+ command, this SHOULD be the internal date and time of the source
+ message. In the case of messages delivered by the IMAP4rev1
+ APPEND command, this SHOULD be the date and time as specified in
+ the APPEND command description. All other cases are
+ implementation defined.
+
+2.3.4. [RFC-2822] Size Message Attribute
+
+ The number of octets in the message, as expressed in [RFC-2822]
+ format.
+
+2.3.5. Envelope Structure Message Attribute
+
+ A parsed representation of the [RFC-2822] header of the message.
+ Note that the IMAP Envelope structure is not the same as an
+ [SMTP] envelope.
+
+2.3.6. Body Structure Message Attribute
+
+ A parsed representation of the [MIME-IMB] body structure
+ information of the message.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 12]
+
+RFC 3501 IMAPv4 March 2003
+
+
+2.4. Message Texts
+
+ In addition to being able to fetch the full [RFC-2822] text of a
+ message, IMAP4rev1 permits the fetching of portions of the full
+ message text. Specifically, it is possible to fetch the
+ [RFC-2822] message header, [RFC-2822] message body, a [MIME-IMB]
+ body part, or a [MIME-IMB] header.
+
+3. State and Flow Diagram
+
+ Once the connection between client and server is established, an
+ IMAP4rev1 connection is in one of four states. The initial
+ state is identified in the server greeting. Most commands are
+ only valid in certain states. It is a protocol error for the
+ client to attempt a command while the connection is in an
+ inappropriate state, and the server will respond with a BAD or
+ NO (depending upon server implementation) command completion
+ result.
+
+3.1. Not Authenticated State
+
+ In the not authenticated state, the client MUST supply
+ authentication credentials before most commands will be
+ permitted. This state is entered when a connection starts
+ unless the connection has been pre-authenticated.
+
+3.2. Authenticated State
+
+ In the authenticated state, the client is authenticated and MUST
+ select a mailbox to access before commands that affect messages
+ will be permitted. This state is entered when a
+ pre-authenticated connection starts, when acceptable
+ authentication credentials have been provided, after an error in
+ selecting a mailbox, or after a successful CLOSE command.
+
+3.3. Selected State
+
+ In a selected state, a mailbox has been selected to access.
+ This state is entered when a mailbox has been successfully
+ selected.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 13]
+
+RFC 3501 IMAPv4 March 2003
+
+
+3.4. Logout State
+
+ In the logout state, the connection is being terminated. This
+ state can be entered as a result of a client request (via the
+ LOGOUT command) or by unilateral action on the part of either
+ the client or server.
+
+ If the client requests the logout state, the server MUST send an
+ untagged BYE response and a tagged OK response to the LOGOUT
+ command before the server closes the connection; and the client
+ MUST read the tagged OK response to the LOGOUT command before
+ the client closes the connection.
+
+ A server MUST NOT unilaterally close the connection without
+ sending an untagged BYE response that contains the reason for
+ having done so. A client SHOULD NOT unilaterally close the
+ connection, and instead SHOULD issue a LOGOUT command. If the
+ server detects that the client has unilaterally closed the
+ connection, the server MAY omit the untagged BYE response and
+ simply close its connection.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 14]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ +----------------------+
+ |connection established|
+ +----------------------+
+ ||
+ \/
+ +--------------------------------------+
+ | server greeting |
+ +--------------------------------------+
+ || (1) || (2) || (3)
+ \/ || ||
+ +-----------------+ || ||
+ |Not Authenticated| || ||
+ +-----------------+ || ||
+ || (7) || (4) || ||
+ || \/ \/ ||
+ || +----------------+ ||
+ || | Authenticated |<=++ ||
+ || +----------------+ || ||
+ || || (7) || (5) || (6) ||
+ || || \/ || ||
+ || || +--------+ || ||
+ || || |Selected|==++ ||
+ || || +--------+ ||
+ || || || (7) ||
+ \/ \/ \/ \/
+ +--------------------------------------+
+ | Logout |
+ +--------------------------------------+
+ ||
+ \/
+ +-------------------------------+
+ |both sides close the connection|
+ +-------------------------------+
+
+ (1) connection without pre-authentication (OK greeting)
+ (2) pre-authenticated connection (PREAUTH greeting)
+ (3) rejected connection (BYE greeting)
+ (4) successful LOGIN or AUTHENTICATE command
+ (5) successful SELECT or EXAMINE command
+ (6) CLOSE command, or failed SELECT or EXAMINE command
+ (7) LOGOUT command, server shutdown, or connection closed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 15]
+
+RFC 3501 IMAPv4 March 2003
+
+
+4. Data Formats
+
+ IMAP4rev1 uses textual commands and responses. Data in
+ IMAP4rev1 can be in one of several forms: atom, number, string,
+ parenthesized list, or NIL. Note that a particular data item
+ may take more than one form; for example, a data item defined as
+ using "astring" syntax may be either an atom or a string.
+
+4.1. Atom
+
+ An atom consists of one or more non-special characters.
+
+4.2. Number
+
+ A number consists of one or more digit characters, and
+ represents a numeric value.
+
+4.3. String
+
+ A string is in one of two forms: either literal or quoted
+ string. The literal form is the general form of string. The
+ quoted string form is an alternative that avoids the overhead of
+ processing a literal at the cost of limitations of characters
+ which may be used.
+
+ A literal is a sequence of zero or more octets (including CR and
+ LF), prefix-quoted with an octet count in the form of an open
+ brace ("{"), the number of octets, close brace ("}"), and CRLF.
+ In the case of literals transmitted from server to client, the
+ CRLF is immediately followed by the octet data. In the case of
+ literals transmitted from client to server, the client MUST wait
+ to receive a command continuation request (described later in
+ this document) before sending the octet data (and the remainder
+ of the command).
+
+ A quoted string is a sequence of zero or more 7-bit characters,
+ excluding CR and LF, with double quote (<">) characters at each
+ end.
+
+ The empty string is represented as either "" (a quoted string
+ with zero characters between double quotes) or as {0} followed
+ by CRLF (a literal with an octet count of 0).
+
+ Note: Even if the octet count is 0, a client transmitting a
+ literal MUST wait to receive a command continuation request.
+
+
+
+
+
+
+Crispin Standards Track [Page 16]
+
+RFC 3501 IMAPv4 March 2003
+
+
+4.3.1. 8-bit and Binary Strings
+
+ 8-bit textual and binary mail is supported through the use of a
+ [MIME-IMB] content transfer encoding. IMAP4rev1 implementations MAY
+ transmit 8-bit or multi-octet characters in literals, but SHOULD do
+ so only when the [CHARSET] is identified.
+
+ Although a BINARY body encoding is defined, unencoded binary strings
+ are not permitted. A "binary string" is any string with NUL
+ characters. Implementations MUST encode binary data into a textual
+ form, such as BASE64, before transmitting the data. A string with an
+ excessive amount of CTL characters MAY also be considered to be
+ binary.
+
+4.4. Parenthesized List
+
+ Data structures are represented as a "parenthesized list"; a sequence
+ of data items, delimited by space, and bounded at each end by
+ parentheses. A parenthesized list can contain other parenthesized
+ lists, using multiple levels of parentheses to indicate nesting.
+
+ The empty list is represented as () -- a parenthesized list with no
+ members.
+
+4.5. NIL
+
+ The special form "NIL" represents the non-existence of a particular
+ data item that is represented as a string or parenthesized list, as
+ distinct from the empty string "" or the empty parenthesized list ().
+
+ Note: NIL is never used for any data item which takes the
+ form of an atom. For example, a mailbox name of "NIL" is a
+ mailbox named NIL as opposed to a non-existent mailbox
+ name. This is because mailbox uses "astring" syntax which
+ is an atom or a string. Conversely, an addr-name of NIL is
+ a non-existent personal name, because addr-name uses
+ "nstring" syntax which is NIL or a string, but never an
+ atom.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 17]
+
+RFC 3501 IMAPv4 March 2003
+
+
+5. Operational Considerations
+
+ The following rules are listed here to ensure that all IMAP4rev1
+ implementations interoperate properly.
+
+5.1. Mailbox Naming
+
+ Mailbox names are 7-bit. Client implementations MUST NOT attempt to
+ create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
+ names returned by LIST or LSUB as UTF-8. Server implementations
+ SHOULD prohibit the creation of 8-bit mailbox names, and SHOULD NOT
+ return 8-bit mailbox names in LIST or LSUB. See section 5.1.3 for
+ more information on how to represent non-ASCII mailbox names.
+
+ Note: 8-bit mailbox names were undefined in earlier
+ versions of this protocol. Some sites used a local 8-bit
+ character set to represent non-ASCII mailbox names. Such
+ usage is not interoperable, and is now formally deprecated.
+
+ The case-insensitive mailbox name INBOX is a special name reserved to
+ mean "the primary mailbox for this user on this server". The
+ interpretation of all other names is implementation-dependent.
+
+ In particular, this specification takes no position on case
+ sensitivity in non-INBOX mailbox names. Some server implementations
+ are fully case-sensitive; others preserve case of a newly-created
+ name but otherwise are case-insensitive; and yet others coerce names
+ to a particular case. Client implementations MUST interact with any
+ of these. If a server implementation interprets non-INBOX mailbox
+ names as case-insensitive, it MUST treat names using the
+ international naming convention specially as described in section
+ 5.1.3.
+
+ There are certain client considerations when creating a new mailbox
+ name:
+
+ 1) Any character which is one of the atom-specials (see the Formal
+ Syntax) will require that the mailbox name be represented as a
+ quoted string or literal.
+
+ 2) CTL and other non-graphic characters are difficult to represent
+ in a user interface and are best avoided.
+
+ 3) Although the list-wildcard characters ("%" and "*") are valid
+ in a mailbox name, it is difficult to use such mailbox names
+ with the LIST and LSUB commands due to the conflict with
+ wildcard interpretation.
+
+
+
+
+Crispin Standards Track [Page 18]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 4) Usually, a character (determined by the server implementation)
+ is reserved to delimit levels of hierarchy.
+
+ 5) Two characters, "#" and "&", have meanings by convention, and
+ should be avoided except when used in that convention.
+
+5.1.1. Mailbox Hierarchy Naming
+
+ If it is desired to export hierarchical mailbox names, mailbox names
+ MUST be left-to-right hierarchical using a single character to
+ separate levels of hierarchy. The same hierarchy separator character
+ is used for all levels of hierarchy within a single name.
+
+5.1.2. Mailbox Namespace Naming Convention
+
+ By convention, the first hierarchical element of any mailbox name
+ which begins with "#" identifies the "namespace" of the remainder of
+ the name. This makes it possible to disambiguate between different
+ types of mailbox stores, each of which have their own namespaces.
+
+ For example, implementations which offer access to USENET
+ newsgroups MAY use the "#news" namespace to partition the
+ USENET newsgroup namespace from that of other mailboxes.
+ Thus, the comp.mail.misc newsgroup would have a mailbox
+ name of "#news.comp.mail.misc", and the name
+ "comp.mail.misc" can refer to a different object (e.g., a
+ user's private mailbox).
+
+5.1.3. Mailbox International Naming Convention
+
+ By convention, international mailbox names in IMAP4rev1 are specified
+ using a modified version of the UTF-7 encoding described in [UTF-7].
+ Modified UTF-7 may also be usable in servers that implement an
+ earlier version of this protocol.
+
+ In modified UTF-7, printable US-ASCII characters, except for "&",
+ represent themselves; that is, characters with octet values 0x20-0x25
+ and 0x27-0x7e. The character "&" (0x26) is represented by the
+ two-octet sequence "&-".
+
+ All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
+ represented in modified BASE64, with a further modification from
+ [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be
+ used to represent any printing US-ASCII character which can represent
+ itself.
+
+
+
+
+
+
+Crispin Standards Track [Page 19]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ "&" is used to shift to modified BASE64 and "-" to shift back to
+ US-ASCII. There is no implicit shift from BASE64 to US-ASCII, and
+ null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
+ means "&") are not permitted. However, all names start in US-ASCII,
+ and MUST end in US-ASCII; that is, a name that ends with a non-ASCII
+ ISO-10646 character MUST end with a "-").
+
+ The purpose of these modifications is to correct the following
+ problems with UTF-7:
+
+ 1) UTF-7 uses the "+" character for shifting; this conflicts with
+ the common use of "+" in mailbox names, in particular USENET
+ newsgroup names.
+
+ 2) UTF-7's encoding is BASE64 which uses the "/" character; this
+ conflicts with the use of "/" as a popular hierarchy delimiter.
+
+ 3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
+ the use of "\" as a popular hierarchy delimiter.
+
+ 4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
+ the use of "~" in some servers as a home directory indicator.
+
+ 5) UTF-7 permits multiple alternate forms to represent the same
+ string; in particular, printable US-ASCII characters can be
+ represented in encoded form.
+
+ Although modified UTF-7 is a convention, it establishes certain
+ requirements on server handling of any mailbox name with an
+ embedded "&" character. In particular, server implementations
+ MUST preserve the exact form of the modified BASE64 portion of a
+ modified UTF-7 name and treat that text as case-sensitive, even if
+ names are otherwise case-insensitive or case-folded.
+
+ Server implementations SHOULD verify that any mailbox name with an
+ embedded "&" character, used as an argument to CREATE, is: in the
+ correctly modified UTF-7 syntax, has no superfluous shifts, and
+ has no encoding in modified BASE64 of any printing US-ASCII
+ character which can represent itself. However, client
+ implementations MUST NOT depend upon the server doing this, and
+ SHOULD NOT attempt to create a mailbox name with an embedded "&"
+ character unless it complies with the modified UTF-7 syntax.
+
+ Server implementations which export a mail store that does not
+ follow the modified UTF-7 convention MUST convert to modified
+ UTF-7 any mailbox name that contains either non-ASCII characters
+ or the "&" character.
+
+
+
+
+Crispin Standards Track [Page 20]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, here is a mailbox name which mixes English,
+ Chinese, and Japanese text:
+ ~peter/mail/&U,BTFw-/&ZeVnLIqe-
+
+ For example, the string "&Jjo!" is not a valid mailbox
+ name because it does not contain a shift to US-ASCII
+ before the "!". The correct form is "&Jjo-!". The
+ string "&U,BTFw-&ZeVnLIqe-" is not permitted because it
+ contains a superfluous shift. The correct form is
+ "&U,BTF2XlZyyKng-".
+
+5.2. Mailbox Size and Message Status Updates
+
+ At any time, a server can send data that the client did not request.
+ Sometimes, such behavior is REQUIRED. For example, agents other than
+ the server MAY add messages to the mailbox (e.g., new message
+ delivery), change the flags of the messages in the mailbox (e.g.,
+ simultaneous access to the same mailbox by multiple agents), or even
+ remove messages from the mailbox. A server MUST send mailbox size
+ updates automatically if a mailbox size change is observed during the
+ processing of a command. A server SHOULD send message flag updates
+ automatically, without requiring the client to request such updates
+ explicitly.
+
+ Special rules exist for server notification of a client about the
+ removal of messages to prevent synchronization errors; see the
+ description of the EXPUNGE response for more detail. In particular,
+ it is NOT permitted to send an EXISTS response that would reduce the
+ number of messages in the mailbox; only the EXPUNGE response can do
+ this.
+
+ Regardless of what implementation decisions a client makes on
+ remembering data from the server, a client implementation MUST record
+ mailbox size updates. It MUST NOT assume that any command after the
+ initial mailbox selection will return the size of the mailbox.
+
+5.3. Response when no Command in Progress
+
+ Server implementations are permitted to send an untagged response
+ (except for EXPUNGE) while there is no command in progress. Server
+ implementations that send such responses MUST deal with flow control
+ considerations. Specifically, they MUST either (1) verify that the
+ size of the data does not exceed the underlying transport's available
+ window size, or (2) use non-blocking writes.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 21]
+
+RFC 3501 IMAPv4 March 2003
+
+
+5.4. Autologout Timer
+
+ If a server has an inactivity autologout timer, the duration of that
+ timer MUST be at least 30 minutes. The receipt of ANY command from
+ the client during that interval SHOULD suffice to reset the
+ autologout timer.
+
+5.5. Multiple Commands in Progress
+
+ The client MAY send another command without waiting for the
+ completion result response of a command, subject to ambiguity rules
+ (see below) and flow control constraints on the underlying data
+ stream. Similarly, a server MAY begin processing another command
+ before processing the current command to completion, subject to
+ ambiguity rules. However, any command continuation request responses
+ and command continuations MUST be negotiated before any subsequent
+ command is initiated.
+
+ The exception is if an ambiguity would result because of a command
+ that would affect the results of other commands. Clients MUST NOT
+ send multiple commands without waiting if an ambiguity would result.
+ If the server detects a possible ambiguity, it MUST execute commands
+ to completion in the order given by the client.
+
+ The most obvious example of ambiguity is when a command would affect
+ the results of another command, e.g., a FETCH of a message's flags
+ and a STORE of that same message's flags.
+
+ A non-obvious ambiguity occurs with commands that permit an untagged
+ EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
+ since an untagged EXPUNGE response can invalidate sequence numbers in
+ a subsequent command. This is not a problem for FETCH, STORE, or
+ SEARCH commands because servers are prohibited from sending EXPUNGE
+ responses while any of those commands are in progress. Therefore, if
+ the client sends any command other than FETCH, STORE, or SEARCH, it
+ MUST wait for the completion result response before sending a command
+ with message sequence numbers.
+
+ Note: UID FETCH, UID STORE, and UID SEARCH are different
+ commands from FETCH, STORE, and SEARCH. If the client
+ sends a UID command, it must wait for a completion result
+ response before sending a command with message sequence
+ numbers.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 22]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, the following non-waiting command sequences are invalid:
+
+ FETCH + NOOP + STORE
+ STORE + COPY + FETCH
+ COPY + COPY
+ CHECK + FETCH
+
+ The following are examples of valid non-waiting command sequences:
+
+ FETCH + STORE + SEARCH + CHECK
+ STORE + COPY + EXPUNGE
+
+ UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting
+ command sequence, depending upon whether or not the second UID
+ SEARCH contains message sequence numbers.
+
+6. Client Commands
+
+ IMAP4rev1 commands are described in this section. Commands are
+ organized by the state in which the command is permitted. Commands
+ which are permitted in multiple states are listed in the minimum
+ permitted state (for example, commands valid in authenticated and
+ selected state are listed in the authenticated state commands).
+
+ Command arguments, identified by "Arguments:" in the command
+ descriptions below, are described by function, not by syntax. The
+ precise syntax of command arguments is described in the Formal Syntax
+ section.
+
+ Some commands cause specific server responses to be returned; these
+ are identified by "Responses:" in the command descriptions below.
+ See the response descriptions in the Responses section for
+ information on these responses, and the Formal Syntax section for the
+ precise syntax of these responses. It is possible for server data to
+ be transmitted as a result of any command. Thus, commands that do
+ not specifically require server data specify "no specific responses
+ for this command" instead of "none".
+
+ The "Result:" in the command description refers to the possible
+ tagged status responses to a command, and any special interpretation
+ of these status responses.
+
+ The state of a connection is only changed by successful commands
+ which are documented as changing state. A rejected command (BAD
+ response) never changes the state of the connection or of the
+ selected mailbox. A failed command (NO response) generally does not
+ change the state of the connection or of the selected mailbox; the
+ exception being the SELECT and EXAMINE commands.
+
+
+
+Crispin Standards Track [Page 23]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.1. Client Commands - Any State
+
+ The following commands are valid in any state: CAPABILITY, NOOP, and
+ LOGOUT.
+
+6.1.1. CAPABILITY Command
+
+ Arguments: none
+
+ Responses: REQUIRED untagged response: CAPABILITY
+
+ Result: OK - capability completed
+ BAD - command unknown or arguments invalid
+
+ The CAPABILITY command requests a listing of capabilities that the
+ server supports. The server MUST send a single untagged
+ CAPABILITY response with "IMAP4rev1" as one of the listed
+ capabilities before the (tagged) OK response.
+
+ A capability name which begins with "AUTH=" indicates that the
+ server supports that particular authentication mechanism. All
+ such names are, by definition, part of this specification. For
+ example, the authorization capability for an experimental
+ "blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
+ "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
+
+ Other capability names refer to extensions, revisions, or
+ amendments to this specification. See the documentation of the
+ CAPABILITY response for additional information. No capabilities,
+ beyond the base IMAP4rev1 set defined in this specification, are
+ enabled without explicit client action to invoke the capability.
+
+ Client and server implementations MUST implement the STARTTLS,
+ LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+ capabilities. See the Security Considerations section for
+ important information.
+
+ See the section entitled "Client Commands -
+ Experimental/Expansion" for information about the form of site or
+ implementation-specific capabilities.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 24]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: abcd CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
+ LOGINDISABLED
+ S: abcd OK CAPABILITY completed
+ C: efgh STARTTLS
+ S: efgh OK STARTLS completed
+ <TLS negotiation, further commands are under [TLS] layer>
+ C: ijkl CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
+ S: ijkl OK CAPABILITY completed
+
+
+6.1.2. NOOP Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command (but see below)
+
+ Result: OK - noop completed
+ BAD - command unknown or arguments invalid
+
+ The NOOP command always succeeds. It does nothing.
+
+ Since any command can return a status update as untagged data, the
+ NOOP command can be used as a periodic poll for new messages or
+ message status updates during a period of inactivity (this is the
+ preferred method to do this). The NOOP command can also be used
+ to reset any inactivity autologout timer on the server.
+
+ Example: C: a002 NOOP
+ S: a002 OK NOOP completed
+ . . .
+ C: a047 NOOP
+ S: * 22 EXPUNGE
+ S: * 23 EXISTS
+ S: * 3 RECENT
+ S: * 14 FETCH (FLAGS (\Seen \Deleted))
+ S: a047 OK NOOP completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 25]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.1.3. LOGOUT Command
+
+ Arguments: none
+
+ Responses: REQUIRED untagged response: BYE
+
+ Result: OK - logout completed
+ BAD - command unknown or arguments invalid
+
+ The LOGOUT command informs the server that the client is done with
+ the connection. The server MUST send a BYE untagged response
+ before the (tagged) OK response, and then close the network
+ connection.
+
+ Example: C: A023 LOGOUT
+ S: * BYE IMAP4rev1 Server logging out
+ S: A023 OK LOGOUT completed
+ (Server and client then close the connection)
+
+6.2. Client Commands - Not Authenticated State
+
+ In the not authenticated state, the AUTHENTICATE or LOGIN command
+ establishes authentication and enters the authenticated state. The
+ AUTHENTICATE command provides a general mechanism for a variety of
+ authentication techniques, privacy protection, and integrity
+ checking; whereas the LOGIN command uses a traditional user name and
+ plaintext password pair and has no means of establishing privacy
+ protection or integrity checking.
+
+ The STARTTLS command is an alternate form of establishing session
+ privacy protection and integrity checking, but does not establish
+ authentication or enter the authenticated state.
+
+ Server implementations MAY allow access to certain mailboxes without
+ establishing authentication. This can be done by means of the
+ ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older
+ convention is a LOGIN command using the userid "anonymous"; in this
+ case, a password is required although the server may choose to accept
+ any password. The restrictions placed on anonymous users are
+ implementation-dependent.
+
+ Once authenticated (including as anonymous), it is not possible to
+ re-enter not authenticated state.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 26]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ the following commands are valid in the not authenticated state:
+ STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations
+ section for important information about these commands.
+
+6.2.1. STARTTLS Command
+
+ Arguments: none
+
+ Responses: no specific response for this command
+
+ Result: OK - starttls completed, begin TLS negotiation
+ BAD - command unknown or arguments invalid
+
+ A [TLS] negotiation begins immediately after the CRLF at the end
+ of the tagged OK response from the server. Once a client issues a
+ STARTTLS command, it MUST NOT issue further commands until a
+ server response is seen and the [TLS] negotiation is complete.
+
+ The server remains in the non-authenticated state, even if client
+ credentials are supplied during the [TLS] negotiation. This does
+ not preclude an authentication mechanism such as EXTERNAL (defined
+ in [SASL]) from using client identity determined by the [TLS]
+ negotiation.
+
+ Once [TLS] has been started, the client MUST discard cached
+ information about server capabilities and SHOULD re-issue the
+ CAPABILITY command. This is necessary to protect against man-in-
+ the-middle attacks which alter the capabilities list prior to
+ STARTTLS. The server MAY advertise different capabilities after
+ STARTTLS.
+
+ Example: C: a001 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
+ S: a001 OK CAPABILITY completed
+ C: a002 STARTTLS
+ S: a002 OK Begin TLS negotiation now
+ <TLS negotiation, further commands are under [TLS] layer>
+ C: a003 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
+ S: a003 OK CAPABILITY completed
+ C: a004 LOGIN joe password
+ S: a004 OK LOGIN completed
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 27]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.2.2. AUTHENTICATE Command
+
+ Arguments: authentication mechanism name
+
+ Responses: continuation data can be requested
+
+ Result: OK - authenticate completed, now in authenticated state
+ NO - authenticate failure: unsupported authentication
+ mechanism, credentials rejected
+ BAD - command unknown or arguments invalid,
+ authentication exchange cancelled
+
+ The AUTHENTICATE command indicates a [SASL] authentication
+ mechanism to the server. If the server supports the requested
+ authentication mechanism, it performs an authentication protocol
+ exchange to authenticate and identify the client. It MAY also
+ negotiate an OPTIONAL security layer for subsequent protocol
+ interactions. If the requested authentication mechanism is not
+ supported, the server SHOULD reject the AUTHENTICATE command by
+ sending a tagged NO response.
+
+ The AUTHENTICATE command does not support the optional "initial
+ response" feature of [SASL]. Section 5.1 of [SASL] specifies how
+ to handle an authentication mechanism which uses an initial
+ response.
+
+ The service name specified by this protocol's profile of [SASL] is
+ "imap".
+
+ The authentication protocol exchange consists of a series of
+ server challenges and client responses that are specific to the
+ authentication mechanism. A server challenge consists of a
+ command continuation request response with the "+" token followed
+ by a BASE64 encoded string. The client response consists of a
+ single line consisting of a BASE64 encoded string. If the client
+ wishes to cancel an authentication exchange, it issues a line
+ consisting of a single "*". If the server receives such a
+ response, it MUST reject the AUTHENTICATE command by sending a
+ tagged BAD response.
+
+ If a security layer is negotiated through the [SASL]
+ authentication exchange, it takes effect immediately following the
+ CRLF that concludes the authentication exchange for the client,
+ and the CRLF of the tagged OK response for the server.
+
+ While client and server implementations MUST implement the
+ AUTHENTICATE command itself, it is not required to implement any
+ authentication mechanisms other than the PLAIN mechanism described
+
+
+
+Crispin Standards Track [Page 28]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ in [IMAP-TLS]. Also, an authentication mechanism is not required
+ to support any security layers.
+
+ Note: a server implementation MUST implement a
+ configuration in which it does NOT permit any plaintext
+ password mechanisms, unless either the STARTTLS command
+ has been negotiated or some other mechanism that
+ protects the session from password snooping has been
+ provided. Server sites SHOULD NOT use any configuration
+ which permits a plaintext password mechanism without
+ such a protection mechanism against password snooping.
+ Client and server implementations SHOULD implement
+ additional [SASL] mechanisms that do not use plaintext
+ passwords, such the GSSAPI mechanism described in [SASL]
+ and/or the [DIGEST-MD5] mechanism.
+
+ Servers and clients can support multiple authentication
+ mechanisms. The server SHOULD list its supported authentication
+ mechanisms in the response to the CAPABILITY command so that the
+ client knows which authentication mechanisms to use.
+
+ A server MAY include a CAPABILITY response code in the tagged OK
+ response of a successful AUTHENTICATE command in order to send
+ capabilities automatically. It is unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes these
+ automatic capabilities. This should only be done if a security
+ layer was not negotiated by the AUTHENTICATE command, because the
+ tagged OK response as part of an AUTHENTICATE command is not
+ protected by encryption/integrity checking. [SASL] requires the
+ client to re-issue a CAPABILITY command in this case.
+
+ If an AUTHENTICATE command fails with a NO response, the client
+ MAY try another authentication mechanism by issuing another
+ AUTHENTICATE command. It MAY also attempt to authenticate by
+ using the LOGIN command (see section 6.2.3 for more detail). In
+ other words, the client MAY request authentication types in
+ decreasing order of preference, with the LOGIN command as a last
+ resort.
+
+ The authorization identity passed from the client to the server
+ during the authentication exchange is interpreted by the server as
+ the user name whose privileges the client is requesting.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 29]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: S: * OK IMAP4rev1 Server
+ C: A001 AUTHENTICATE GSSAPI
+ S: +
+ C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
+ MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
+ b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
+ Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
+ cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
+ AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
+ C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
+ I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
+ vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
+ pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
+ FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
+ NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
+ O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
+ vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
+ S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
+ AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
+ uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
+ C:
+ S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
+ ceP2CWY0SR0fAQAgAAQEBAQ=
+ C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
+ wkhbfa2QteAQAgAG1yYwE=
+ S: A001 OK GSSAPI authentication successful
+
+ Note: The line breaks within server challenges and client
+ responses are for editorial clarity and are not in real
+ authenticators.
+
+
+6.2.3. LOGIN Command
+
+ Arguments: user name
+ password
+
+ Responses: no specific responses for this command
+
+ Result: OK - login completed, now in authenticated state
+ NO - login failure: user name or password rejected
+ BAD - command unknown or arguments invalid
+
+ The LOGIN command identifies the client to the server and carries
+ the plaintext password authenticating this user.
+
+
+
+
+
+
+Crispin Standards Track [Page 30]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A server MAY include a CAPABILITY response code in the tagged OK
+ response to a successful LOGIN command in order to send
+ capabilities automatically. It is unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes these
+ automatic capabilities.
+
+ Example: C: a001 LOGIN SMITH SESAME
+ S: a001 OK LOGIN completed
+
+ Note: Use of the LOGIN command over an insecure network
+ (such as the Internet) is a security risk, because anyone
+ monitoring network traffic can obtain plaintext passwords.
+ The LOGIN command SHOULD NOT be used except as a last
+ resort, and it is recommended that client implementations
+ have a means to disable any automatic use of the LOGIN
+ command.
+
+ Unless either the STARTTLS command has been negotiated or
+ some other mechanism that protects the session from
+ password snooping has been provided, a server
+ implementation MUST implement a configuration in which it
+ advertises the LOGINDISABLED capability and does NOT permit
+ the LOGIN command. Server sites SHOULD NOT use any
+ configuration which permits the LOGIN command without such
+ a protection mechanism against password snooping. A client
+ implementation MUST NOT send a LOGIN command if the
+ LOGINDISABLED capability is advertised.
+
+6.3. Client Commands - Authenticated State
+
+ In the authenticated state, commands that manipulate mailboxes as
+ atomic entities are permitted. Of these commands, the SELECT and
+ EXAMINE commands will select a mailbox for access and enter the
+ selected state.
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ the following commands are valid in the authenticated state: SELECT,
+ EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
+ STATUS, and APPEND.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 31]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.1. SELECT Command
+
+ Arguments: mailbox name
+
+ Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+ REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
+ UIDNEXT, UIDVALIDITY
+
+ Result: OK - select completed, now in selected state
+ NO - select failure, now in authenticated state: no
+ such mailbox, can't access mailbox
+ BAD - command unknown or arguments invalid
+
+ The SELECT command selects a mailbox so that messages in the
+ mailbox can be accessed. Before returning an OK to the client,
+ the server MUST send the following untagged data to the client.
+ Note that earlier versions of this protocol only required the
+ FLAGS, EXISTS, and RECENT untagged data; consequently, client
+ implementations SHOULD implement default behavior for missing data
+ as discussed with the individual item.
+
+ FLAGS Defined flags in the mailbox. See the description
+ of the FLAGS response for more detail.
+
+ <n> EXISTS The number of messages in the mailbox. See the
+ description of the EXISTS response for more detail.
+
+ <n> RECENT The number of messages with the \Recent flag set.
+ See the description of the RECENT response for more
+ detail.
+
+ OK [UNSEEN <n>]
+ The message sequence number of the first unseen
+ message in the mailbox. If this is missing, the
+ client can not make any assumptions about the first
+ unseen message in the mailbox, and needs to issue a
+ SEARCH command if it wants to find it.
+
+ OK [PERMANENTFLAGS (<list of flags>)]
+ A list of message flags that the client can change
+ permanently. If this is missing, the client should
+ assume that all flags can be changed permanently.
+
+ OK [UIDNEXT <n>]
+ The next unique identifier value. Refer to section
+ 2.3.1.1 for more information. If this is missing,
+ the client can not make any assumptions about the
+ next unique identifier value.
+
+
+
+Crispin Standards Track [Page 32]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ OK [UIDVALIDITY <n>]
+ The unique identifier validity value. Refer to
+ section 2.3.1.1 for more information. If this is
+ missing, the server does not support unique
+ identifiers.
+
+ Only one mailbox can be selected at a time in a connection;
+ simultaneous access to multiple mailboxes requires multiple
+ connections. The SELECT command automatically deselects any
+ currently selected mailbox before attempting the new selection.
+ Consequently, if a mailbox is selected and a SELECT command that
+ fails is attempted, no mailbox is selected.
+
+ If the client is permitted to modify the mailbox, the server
+ SHOULD prefix the text of the tagged OK response with the
+ "[READ-WRITE]" response code.
+
+ If the client is not permitted to modify the mailbox but is
+ permitted read access, the mailbox is selected as read-only, and
+ the server MUST prefix the text of the tagged OK response to
+ SELECT with the "[READ-ONLY]" response code. Read-only access
+ through SELECT differs from the EXAMINE command in that certain
+ read-only mailboxes MAY permit the change of permanent state on a
+ per-user (as opposed to global) basis. Netnews messages marked in
+ a server-based .newsrc file are an example of such per-user
+ permanent state that can be modified with read-only mailboxes.
+
+ Example: C: A142 SELECT INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: A142 OK [READ-WRITE] SELECT completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 33]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.2. EXAMINE Command
+
+ Arguments: mailbox name
+
+ Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
+ REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
+ UIDNEXT, UIDVALIDITY
+
+ Result: OK - examine completed, now in selected state
+ NO - examine failure, now in authenticated state: no
+ such mailbox, can't access mailbox
+ BAD - command unknown or arguments invalid
+
+ The EXAMINE command is identical to SELECT and returns the same
+ output; however, the selected mailbox is identified as read-only.
+ No changes to the permanent state of the mailbox, including
+ per-user state, are permitted; in particular, EXAMINE MUST NOT
+ cause messages to lose the \Recent flag.
+
+ The text of the tagged OK response to the EXAMINE command MUST
+ begin with the "[READ-ONLY]" response code.
+
+ Example: C: A932 EXAMINE blurdybloop
+ S: * 17 EXISTS
+ S: * 2 RECENT
+ S: * OK [UNSEEN 8] Message 8 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
+ S: A932 OK [READ-ONLY] EXAMINE completed
+
+
+6.3.3. CREATE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - create completed
+ NO - create failure: can't create mailbox with that name
+ BAD - command unknown or arguments invalid
+
+ The CREATE command creates a mailbox with the given name. An OK
+ response is returned only if a new mailbox with that name has been
+ created. It is an error to attempt to create INBOX or a mailbox
+ with a name that refers to an extant mailbox. Any error in
+ creation will return a tagged NO response.
+
+
+
+Crispin Standards Track [Page 34]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If the mailbox name is suffixed with the server's hierarchy
+ separator character (as returned from the server by a LIST
+ command), this is a declaration that the client intends to create
+ mailbox names under this name in the hierarchy. Server
+ implementations that do not require this declaration MUST ignore
+ the declaration. In any case, the name created is without the
+ trailing hierarchy delimiter.
+
+ If the server's hierarchy separator character appears elsewhere in
+ the name, the server SHOULD create any superior hierarchical names
+ that are needed for the CREATE command to be successfully
+ completed. In other words, an attempt to create "foo/bar/zap" on
+ a server in which "/" is the hierarchy separator character SHOULD
+ create foo/ and foo/bar/ if they do not already exist.
+
+ If a new mailbox is created with the same name as a mailbox which
+ was deleted, its unique identifiers MUST be greater than any
+ unique identifiers used in the previous incarnation of the mailbox
+ UNLESS the new incarnation has a different unique identifier
+ validity value. See the description of the UID command for more
+ detail.
+
+ Example: C: A003 CREATE owatagusiam/
+ S: A003 OK CREATE completed
+ C: A004 CREATE owatagusiam/blurdybloop
+ S: A004 OK CREATE completed
+
+ Note: The interpretation of this example depends on whether
+ "/" was returned as the hierarchy separator from LIST. If
+ "/" is the hierarchy separator, a new level of hierarchy
+ named "owatagusiam" with a member called "blurdybloop" is
+ created. Otherwise, two mailboxes at the same hierarchy
+ level are created.
+
+
+6.3.4. DELETE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - delete completed
+ NO - delete failure: can't delete mailbox with that name
+ BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin Standards Track [Page 35]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The DELETE command permanently removes the mailbox with the given
+ name. A tagged OK response is returned only if the mailbox has
+ been deleted. It is an error to attempt to delete INBOX or a
+ mailbox name that does not exist.
+
+ The DELETE command MUST NOT remove inferior hierarchical names.
+ For example, if a mailbox "foo" has an inferior "foo.bar"
+ (assuming "." is the hierarchy delimiter character), removing
+ "foo" MUST NOT remove "foo.bar". It is an error to attempt to
+ delete a name that has inferior hierarchical names and also has
+ the \Noselect mailbox name attribute (see the description of the
+ LIST response for more details).
+
+ It is permitted to delete a name that has inferior hierarchical
+ names and does not have the \Noselect mailbox name attribute. In
+ this case, all messages in that mailbox are removed, and the name
+ will acquire the \Noselect mailbox name attribute.
+
+ The value of the highest-used unique identifier of the deleted
+ mailbox MUST be preserved so that a new mailbox created with the
+ same name will not reuse the identifiers of the former
+ incarnation, UNLESS the new incarnation has a different unique
+ identifier validity value. See the description of the UID command
+ for more detail.
+
+ Examples: C: A682 LIST "" *
+ S: * LIST () "/" blurdybloop
+ S: * LIST (\Noselect) "/" foo
+ S: * LIST () "/" foo/bar
+ S: A682 OK LIST completed
+ C: A683 DELETE blurdybloop
+ S: A683 OK DELETE completed
+ C: A684 DELETE foo
+ S: A684 NO Name "foo" has inferior hierarchical names
+ C: A685 DELETE foo/bar
+ S: A685 OK DELETE Completed
+ C: A686 LIST "" *
+ S: * LIST (\Noselect) "/" foo
+ S: A686 OK LIST completed
+ C: A687 DELETE foo
+ S: A687 OK DELETE Completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 36]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ C: A82 LIST "" *
+ S: * LIST () "." blurdybloop
+ S: * LIST () "." foo
+ S: * LIST () "." foo.bar
+ S: A82 OK LIST completed
+ C: A83 DELETE blurdybloop
+ S: A83 OK DELETE completed
+ C: A84 DELETE foo
+ S: A84 OK DELETE Completed
+ C: A85 LIST "" *
+ S: * LIST () "." foo.bar
+ S: A85 OK LIST completed
+ C: A86 LIST "" %
+ S: * LIST (\Noselect) "." foo
+ S: A86 OK LIST completed
+
+
+6.3.5. RENAME Command
+
+ Arguments: existing mailbox name
+ new mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - rename completed
+ NO - rename failure: can't rename mailbox with that name,
+ can't rename to mailbox with that name
+ BAD - command unknown or arguments invalid
+
+ The RENAME command changes the name of a mailbox. A tagged OK
+ response is returned only if the mailbox has been renamed. It is
+ an error to attempt to rename from a mailbox name that does not
+ exist or to a mailbox name that already exists. Any error in
+ renaming will return a tagged NO response.
+
+ If the name has inferior hierarchical names, then the inferior
+ hierarchical names MUST also be renamed. For example, a rename of
+ "foo" to "zap" will rename "foo/bar" (assuming "/" is the
+ hierarchy delimiter character) to "zap/bar".
+
+ If the server's hierarchy separator character appears in the name,
+ the server SHOULD create any superior hierarchical names that are
+ needed for the RENAME command to complete successfully. In other
+ words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
+ server in which "/" is the hierarchy separator character SHOULD
+ create baz/ and baz/rag/ if they do not already exist.
+
+
+
+
+
+Crispin Standards Track [Page 37]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The value of the highest-used unique identifier of the old mailbox
+ name MUST be preserved so that a new mailbox created with the same
+ name will not reuse the identifiers of the former incarnation,
+ UNLESS the new incarnation has a different unique identifier
+ validity value. See the description of the UID command for more
+ detail.
+
+ Renaming INBOX is permitted, and has special behavior. It moves
+ all messages in INBOX to a new mailbox with the given name,
+ leaving INBOX empty. If the server implementation supports
+ inferior hierarchical names of INBOX, these are unaffected by a
+ rename of INBOX.
+
+ Examples: C: A682 LIST "" *
+ S: * LIST () "/" blurdybloop
+ S: * LIST (\Noselect) "/" foo
+ S: * LIST () "/" foo/bar
+ S: A682 OK LIST completed
+ C: A683 RENAME blurdybloop sarasoop
+ S: A683 OK RENAME completed
+ C: A684 RENAME foo zowie
+ S: A684 OK RENAME Completed
+ C: A685 LIST "" *
+ S: * LIST () "/" sarasoop
+ S: * LIST (\Noselect) "/" zowie
+ S: * LIST () "/" zowie/bar
+ S: A685 OK LIST completed
+
+ C: Z432 LIST "" *
+ S: * LIST () "." INBOX
+ S: * LIST () "." INBOX.bar
+ S: Z432 OK LIST completed
+ C: Z433 RENAME INBOX old-mail
+ S: Z433 OK RENAME completed
+ C: Z434 LIST "" *
+ S: * LIST () "." INBOX
+ S: * LIST () "." INBOX.bar
+ S: * LIST () "." old-mail
+ S: Z434 OK LIST completed
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 38]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.6. SUBSCRIBE Command
+
+ Arguments: mailbox
+
+ Responses: no specific responses for this command
+
+ Result: OK - subscribe completed
+ NO - subscribe failure: can't subscribe to that name
+ BAD - command unknown or arguments invalid
+
+ The SUBSCRIBE command adds the specified mailbox name to the
+ server's set of "active" or "subscribed" mailboxes as returned by
+ the LSUB command. This command returns a tagged OK response only
+ if the subscription is successful.
+
+ A server MAY validate the mailbox argument to SUBSCRIBE to verify
+ that it exists. However, it MUST NOT unilaterally remove an
+ existing mailbox name from the subscription list even if a mailbox
+ by that name no longer exists.
+
+ Note: This requirement is because a server site can
+ choose to routinely remove a mailbox with a well-known
+ name (e.g., "system-alerts") after its contents expire,
+ with the intention of recreating it when new contents
+ are appropriate.
+
+
+ Example: C: A002 SUBSCRIBE #news.comp.mail.mime
+ S: A002 OK SUBSCRIBE completed
+
+
+6.3.7. UNSUBSCRIBE Command
+
+ Arguments: mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - unsubscribe completed
+ NO - unsubscribe failure: can't unsubscribe that name
+ BAD - command unknown or arguments invalid
+
+ The UNSUBSCRIBE command removes the specified mailbox name from
+ the server's set of "active" or "subscribed" mailboxes as returned
+ by the LSUB command. This command returns a tagged OK response
+ only if the unsubscription is successful.
+
+ Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime
+ S: A002 OK UNSUBSCRIBE completed
+
+
+
+Crispin Standards Track [Page 39]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.8. LIST Command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LIST
+
+ Result: OK - list completed
+ NO - list failure: can't list that reference or name
+ BAD - command unknown or arguments invalid
+
+ The LIST command returns a subset of names from the complete set
+ of all names available to the client. Zero or more untagged LIST
+ replies are returned, containing the name attributes, hierarchy
+ delimiter, and name; see the description of the LIST reply for
+ more detail.
+
+ The LIST command SHOULD return its data quickly, without undue
+ delay. For example, it SHOULD NOT go to excess trouble to
+ calculate the \Marked or \Unmarked status or perform other
+ processing; if each name requires 1 second of processing, then a
+ list of 1200 names would take 20 minutes!
+
+ An empty ("" string) reference name argument indicates that the
+ mailbox name is interpreted as by SELECT. The returned mailbox
+ names MUST match the supplied mailbox name pattern. A non-empty
+ reference name argument is the name of a mailbox or a level of
+ mailbox hierarchy, and indicates the context in which the mailbox
+ name is interpreted.
+
+ An empty ("" string) mailbox name argument is a special request to
+ return the hierarchy delimiter and the root name of the name given
+ in the reference. The value returned as the root MAY be the empty
+ string if the reference is non-rooted or is an empty string. In
+ all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
+ is returned. This permits a client to get the hierarchy delimiter
+ (or find out that the mailbox names are flat) even when no
+ mailboxes by that name currently exist.
+
+ The reference and mailbox name arguments are interpreted into a
+ canonical form that represents an unambiguous left-to-right
+ hierarchy. The returned mailbox names will be in the interpreted
+ form.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 40]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Note: The interpretation of the reference argument is
+ implementation-defined. It depends upon whether the
+ server implementation has a concept of the "current
+ working directory" and leading "break out characters",
+ which override the current working directory.
+
+ For example, on a server which exports a UNIX or NT
+ filesystem, the reference argument contains the current
+ working directory, and the mailbox name argument would
+ contain the name as interpreted in the current working
+ directory.
+
+ If a server implementation has no concept of break out
+ characters, the canonical form is normally the reference
+ name appended with the mailbox name. Note that if the
+ server implements the namespace convention (section
+ 5.1.2), "#" is a break out character and must be treated
+ as such.
+
+ If the reference argument is not a level of mailbox
+ hierarchy (that is, it is a \NoInferiors name), and/or
+ the reference argument does not end with the hierarchy
+ delimiter, it is implementation-dependent how this is
+ interpreted. For example, a reference of "foo/bar" and
+ mailbox name of "rag/baz" could be interpreted as
+ "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
+ A client SHOULD NOT use such a reference argument except
+ at the explicit request of the user. A hierarchical
+ browser MUST NOT make any assumptions about server
+ interpretation of the reference unless the reference is
+ a level of mailbox hierarchy AND ends with the hierarchy
+ delimiter.
+
+ Any part of the reference argument that is included in the
+ interpreted form SHOULD prefix the interpreted form. It SHOULD
+ also be in the same form as the reference name argument. This
+ rule permits the client to determine if the returned mailbox name
+ is in the context of the reference argument, or if something about
+ the mailbox argument overrode the reference argument. Without
+ this rule, the client would have to have knowledge of the server's
+ naming semantics including what characters are "breakouts" that
+ override a naming context.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 41]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, here are some examples of how references
+ and mailbox names might be interpreted on a UNIX-based
+ server:
+
+ Reference Mailbox Name Interpretation
+ ------------ ------------ --------------
+ ~smith/Mail/ foo.* ~smith/Mail/foo.*
+ archive/ % archive/%
+ #news. comp.mail.* #news.comp.mail.*
+ ~smith/Mail/ /usr/doc/foo /usr/doc/foo
+ archive/ ~fred/Mail/* ~fred/Mail/*
+
+ The first three examples demonstrate interpretations in
+ the context of the reference argument. Note that
+ "~smith/Mail" SHOULD NOT be transformed into something
+ like "/u2/users/smith/Mail", or it would be impossible
+ for the client to determine that the interpretation was
+ in the context of the reference.
+
+ The character "*" is a wildcard, and matches zero or more
+ characters at this position. The character "%" is similar to "*",
+ but it does not match a hierarchy delimiter. If the "%" wildcard
+ is the last character of a mailbox name argument, matching levels
+ of hierarchy are also returned. If these levels of hierarchy are
+ not also selectable mailboxes, they are returned with the
+ \Noselect mailbox name attribute (see the description of the LIST
+ response for more details).
+
+ Server implementations are permitted to "hide" otherwise
+ accessible mailboxes from the wildcard characters, by preventing
+ certain characters or names from matching a wildcard in certain
+ situations. For example, a UNIX-based server might restrict the
+ interpretation of "*" so that an initial "/" character does not
+ match.
+
+ The special name INBOX is included in the output from LIST, if
+ INBOX is supported by this server for this user and if the
+ uppercase string "INBOX" matches the interpreted reference and
+ mailbox name arguments with wildcards as described above. The
+ criteria for omitting INBOX is whether SELECT INBOX will return
+ failure; it is not relevant whether the user's real INBOX resides
+ on this or some other server.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 42]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A101 LIST "" ""
+ S: * LIST (\Noselect) "/" ""
+ S: A101 OK LIST Completed
+ C: A102 LIST #news.comp.mail.misc ""
+ S: * LIST (\Noselect) "." #news.
+ S: A102 OK LIST Completed
+ C: A103 LIST /usr/staff/jones ""
+ S: * LIST (\Noselect) "/" /
+ S: A103 OK LIST Completed
+ C: A202 LIST ~/Mail/ %
+ S: * LIST (\Noselect) "/" ~/Mail/foo
+ S: * LIST () "/" ~/Mail/meetings
+ S: A202 OK LIST completed
+
+
+6.3.9. LSUB Command
+
+ Arguments: reference name
+ mailbox name with possible wildcards
+
+ Responses: untagged responses: LSUB
+
+ Result: OK - lsub completed
+ NO - lsub failure: can't list that reference or name
+ BAD - command unknown or arguments invalid
+
+ The LSUB command returns a subset of names from the set of names
+ that the user has declared as being "active" or "subscribed".
+ Zero or more untagged LSUB replies are returned. The arguments to
+ LSUB are in the same form as those for LIST.
+
+ The returned untagged LSUB response MAY contain different mailbox
+ flags from a LIST untagged response. If this should happen, the
+ flags in the untagged LIST are considered more authoritative.
+
+ A special situation occurs when using LSUB with the % wildcard.
+ Consider what happens if "foo/bar" (with a hierarchy delimiter of
+ "/") is subscribed but "foo" is not. A "%" wildcard to LSUB must
+ return foo, not foo/bar, in the LSUB response, and it MUST be
+ flagged with the \Noselect attribute.
+
+ The server MUST NOT unilaterally remove an existing mailbox name
+ from the subscription list even if a mailbox by that name no
+ longer exists.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 43]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A002 LSUB "#news." "comp.mail.*"
+ S: * LSUB () "." #news.comp.mail.mime
+ S: * LSUB () "." #news.comp.mail.misc
+ S: A002 OK LSUB completed
+ C: A003 LSUB "#news." "comp.%"
+ S: * LSUB (\NoSelect) "." #news.comp.mail
+ S: A003 OK LSUB completed
+
+
+6.3.10. STATUS Command
+
+ Arguments: mailbox name
+ status data item names
+
+ Responses: untagged responses: STATUS
+
+ Result: OK - status completed
+ NO - status failure: no status for that name
+ BAD - command unknown or arguments invalid
+
+ The STATUS command requests the status of the indicated mailbox.
+ It does not change the currently selected mailbox, nor does it
+ affect the state of any messages in the queried mailbox (in
+ particular, STATUS MUST NOT cause messages to lose the \Recent
+ flag).
+
+ The STATUS command provides an alternative to opening a second
+ IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
+ query that mailbox's status without deselecting the current
+ mailbox in the first IMAP4rev1 connection.
+
+ Unlike the LIST command, the STATUS command is not guaranteed to
+ be fast in its response. Under certain circumstances, it can be
+ quite slow. In some implementations, the server is obliged to
+ open the mailbox read-only internally to obtain certain status
+ information. Also unlike the LIST command, the STATUS command
+ does not accept wildcards.
+
+ Note: The STATUS command is intended to access the
+ status of mailboxes other than the currently selected
+ mailbox. Because the STATUS command can cause the
+ mailbox to be opened internally, and because this
+ information is available by other means on the selected
+ mailbox, the STATUS command SHOULD NOT be used on the
+ currently selected mailbox.
+
+
+
+
+
+
+Crispin Standards Track [Page 44]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The STATUS command MUST NOT be used as a "check for new
+ messages in the selected mailbox" operation (refer to
+ sections 7, 7.3.1, and 7.3.2 for more information about
+ the proper method for new message checking).
+
+ Because the STATUS command is not guaranteed to be fast
+ in its results, clients SHOULD NOT expect to be able to
+ issue many consecutive STATUS commands and obtain
+ reasonable performance.
+
+ The currently defined status data items that can be requested are:
+
+ MESSAGES
+ The number of messages in the mailbox.
+
+ RECENT
+ The number of messages with the \Recent flag set.
+
+ UIDNEXT
+ The next unique identifier value of the mailbox. Refer to
+ section 2.3.1.1 for more information.
+
+ UIDVALIDITY
+ The unique identifier validity value of the mailbox. Refer to
+ section 2.3.1.1 for more information.
+
+ UNSEEN
+ The number of messages which do not have the \Seen flag set.
+
+
+ Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
+ S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+ S: A042 OK STATUS completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 45]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.3.11. APPEND Command
+
+ Arguments: mailbox name
+ OPTIONAL flag parenthesized list
+ OPTIONAL date/time string
+ message literal
+
+ Responses: no specific responses for this command
+
+ Result: OK - append completed
+ NO - append error: can't append to that mailbox, error
+ in flags or date/time or message text
+ BAD - command unknown or arguments invalid
+
+ The APPEND command appends the literal argument as a new message
+ to the end of the specified destination mailbox. This argument
+ SHOULD be in the format of an [RFC-2822] message. 8-bit
+ characters are permitted in the message. A server implementation
+ that is unable to preserve 8-bit data properly MUST be able to
+ reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
+ content transfer encoding.
+
+ Note: There MAY be exceptions, e.g., draft messages, in
+ which required [RFC-2822] header lines are omitted in
+ the message literal argument to APPEND. The full
+ implications of doing so MUST be understood and
+ carefully weighed.
+
+ If a flag parenthesized list is specified, the flags SHOULD be set
+ in the resulting message; otherwise, the flag list of the
+ resulting message is set to empty by default. In either case, the
+ Recent flag is also set.
+
+ If a date-time is specified, the internal date SHOULD be set in
+ the resulting message; otherwise, the internal date of the
+ resulting message is set to the current date and time by default.
+
+ If the append is unsuccessful for any reason, the mailbox MUST be
+ restored to its state before the APPEND attempt; no partial
+ appending is permitted.
+
+ If the destination mailbox does not exist, a server MUST return an
+ error, and MUST NOT automatically create the mailbox. Unless it
+ is certain that the destination mailbox can not be created, the
+ server MUST send the response code "[TRYCREATE]" as the prefix of
+ the text of the tagged NO response. This gives a hint to the
+ client that it can attempt a CREATE command and retry the APPEND
+ if the CREATE is successful.
+
+
+
+Crispin Standards Track [Page 46]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If the mailbox is currently selected, the normal new message
+ actions SHOULD occur. Specifically, the server SHOULD notify the
+ client immediately via an untagged EXISTS response. If the server
+ does not do so, the client MAY issue a NOOP command (or failing
+ that, a CHECK command) after one or more APPEND commands.
+
+ Example: C: A003 APPEND saved-messages (\Seen) {310}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@Blurdybloop.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@Blurdybloop.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK APPEND completed
+
+ Note: The APPEND command is not used for message delivery,
+ because it does not provide a mechanism to transfer [SMTP]
+ envelope information.
+
+6.4. Client Commands - Selected State
+
+ In the selected state, commands that manipulate messages in a mailbox
+ are permitted.
+
+ In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
+ and the authenticated state commands (SELECT, EXAMINE, CREATE,
+ DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
+ APPEND), the following commands are valid in the selected state:
+ CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
+
+6.4.1. CHECK Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - check completed
+ BAD - command unknown or arguments invalid
+
+ The CHECK command requests a checkpoint of the currently selected
+ mailbox. A checkpoint refers to any implementation-dependent
+ housekeeping associated with the mailbox (e.g., resolving the
+ server's in-memory state of the mailbox with the state on its
+
+
+
+Crispin Standards Track [Page 47]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ disk) that is not normally executed as part of each command. A
+ checkpoint MAY take a non-instantaneous amount of real time to
+ complete. If a server implementation has no such housekeeping
+ considerations, CHECK is equivalent to NOOP.
+
+ There is no guarantee that an EXISTS untagged response will happen
+ as a result of CHECK. NOOP, not CHECK, SHOULD be used for new
+ message polling.
+
+ Example: C: FXXZ CHECK
+ S: FXXZ OK CHECK Completed
+
+
+6.4.2. CLOSE Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - close completed, now in authenticated state
+ BAD - command unknown or arguments invalid
+
+ The CLOSE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox, and returns
+ to the authenticated state from the selected state. No untagged
+ EXPUNGE responses are sent.
+
+ No messages are removed, and no error is given, if the mailbox is
+ selected by an EXAMINE command or is otherwise selected read-only.
+
+ Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT
+ command MAY be issued without previously issuing a CLOSE command.
+ The SELECT, EXAMINE, and LOGOUT commands implicitly close the
+ currently selected mailbox without doing an expunge. However,
+ when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
+ sequence is considerably faster than an EXPUNGE-LOGOUT or
+ EXPUNGE-SELECT because no untagged EXPUNGE responses (which the
+ client would probably ignore) are sent.
+
+ Example: C: A341 CLOSE
+ S: A341 OK CLOSE completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 48]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.4.3. EXPUNGE Command
+
+ Arguments: none
+
+ Responses: untagged responses: EXPUNGE
+
+ Result: OK - expunge completed
+ NO - expunge failure: can't expunge (e.g., permission
+ denied)
+ BAD - command unknown or arguments invalid
+
+ The EXPUNGE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox. Before
+ returning an OK to the client, an untagged EXPUNGE response is
+ sent for each message that is removed.
+
+ Example: C: A202 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 5 EXPUNGE
+ S: * 8 EXPUNGE
+ S: A202 OK EXPUNGE completed
+
+ Note: In this example, messages 3, 4, 7, and 11 had the
+ \Deleted flag set. See the description of the EXPUNGE
+ response for further explanation.
+
+
+6.4.4. SEARCH Command
+
+ Arguments: OPTIONAL [CHARSET] specification
+ searching criteria (one or more)
+
+ Responses: REQUIRED untagged response: SEARCH
+
+ Result: OK - search completed
+ NO - search error: can't search that [CHARSET] or
+ criteria
+ BAD - command unknown or arguments invalid
+
+ The SEARCH command searches the mailbox for messages that match
+ the given searching criteria. Searching criteria consist of one
+ or more search keys. The untagged SEARCH response from the server
+ contains a listing of message sequence numbers corresponding to
+ those messages that match the searching criteria.
+
+
+
+
+
+
+Crispin Standards Track [Page 49]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ When multiple keys are specified, the result is the intersection
+ (AND function) of all the messages that match those keys. For
+ example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
+ to all deleted messages from Smith that were placed in the mailbox
+ since February 1, 1994. A search key can also be a parenthesized
+ list of one or more search keys (e.g., for use with the OR and NOT
+ keys).
+
+ Server implementations MAY exclude [MIME-IMB] body parts with
+ terminal content media types other than TEXT and MESSAGE from
+ consideration in SEARCH matching.
+
+ The OPTIONAL [CHARSET] specification consists of the word
+ "CHARSET" followed by a registered [CHARSET]. It indicates the
+ [CHARSET] of the strings that appear in the search criteria.
+ [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
+ [RFC-2822]/[MIME-IMB] headers, MUST be decoded before comparing
+ text in a [CHARSET] other than US-ASCII. US-ASCII MUST be
+ supported; other [CHARSET]s MAY be supported.
+
+ If the server does not support the specified [CHARSET], it MUST
+ return a tagged NO response (not a BAD). This response SHOULD
+ contain the BADCHARSET response code, which MAY list the
+ [CHARSET]s supported by the server.
+
+ In all search keys that use strings, a message matches the key if
+ the string is a substring of the field. The matching is
+ case-insensitive.
+
+ The defined search keys are as follows. Refer to the Formal
+ Syntax section for the precise syntactic definitions of the
+ arguments.
+
+ <sequence set>
+ Messages with message sequence numbers corresponding to the
+ specified message sequence number set.
+
+ ALL
+ All messages in the mailbox; the default initial key for
+ ANDing.
+
+ ANSWERED
+ Messages with the \Answered flag set.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 50]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BCC <string>
+ Messages that contain the specified string in the envelope
+ structure's BCC field.
+
+ BEFORE <date>
+ Messages whose internal date (disregarding time and timezone)
+ is earlier than the specified date.
+
+ BODY <string>
+ Messages that contain the specified string in the body of the
+ message.
+
+ CC <string>
+ Messages that contain the specified string in the envelope
+ structure's CC field.
+
+ DELETED
+ Messages with the \Deleted flag set.
+
+ DRAFT
+ Messages with the \Draft flag set.
+
+ FLAGGED
+ Messages with the \Flagged flag set.
+
+ FROM <string>
+ Messages that contain the specified string in the envelope
+ structure's FROM field.
+
+ HEADER <field-name> <string>
+ Messages that have a header with the specified field-name (as
+ defined in [RFC-2822]) and that contains the specified string
+ in the text of the header (what comes after the colon). If the
+ string to search is zero-length, this matches all messages that
+ have a header line with the specified field-name regardless of
+ the contents.
+
+ KEYWORD <flag>
+ Messages with the specified keyword flag set.
+
+ LARGER <n>
+ Messages with an [RFC-2822] size larger than the specified
+ number of octets.
+
+ NEW
+ Messages that have the \Recent flag set but not the \Seen flag.
+ This is functionally equivalent to "(RECENT UNSEEN)".
+
+
+
+
+Crispin Standards Track [Page 51]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ NOT <search-key>
+ Messages that do not match the specified search key.
+
+ OLD
+ Messages that do not have the \Recent flag set. This is
+ functionally equivalent to "NOT RECENT" (as opposed to "NOT
+ NEW").
+
+ ON <date>
+ Messages whose internal date (disregarding time and timezone)
+ is within the specified date.
+
+ OR <search-key1> <search-key2>
+ Messages that match either search key.
+
+ RECENT
+ Messages that have the \Recent flag set.
+
+ SEEN
+ Messages that have the \Seen flag set.
+
+ SENTBEFORE <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is earlier than the specified date.
+
+ SENTON <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is within the specified date.
+
+ SENTSINCE <date>
+ Messages whose [RFC-2822] Date: header (disregarding time and
+ timezone) is within or later than the specified date.
+
+ SINCE <date>
+ Messages whose internal date (disregarding time and timezone)
+ is within or later than the specified date.
+
+ SMALLER <n>
+ Messages with an [RFC-2822] size smaller than the specified
+ number of octets.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 52]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SUBJECT <string>
+ Messages that contain the specified string in the envelope
+ structure's SUBJECT field.
+
+ TEXT <string>
+ Messages that contain the specified string in the header or
+ body of the message.
+
+ TO <string>
+ Messages that contain the specified string in the envelope
+ structure's TO field.
+
+ UID <sequence set>
+ Messages with unique identifiers corresponding to the specified
+ unique identifier set. Sequence set ranges are permitted.
+
+ UNANSWERED
+ Messages that do not have the \Answered flag set.
+
+ UNDELETED
+ Messages that do not have the \Deleted flag set.
+
+ UNDRAFT
+ Messages that do not have the \Draft flag set.
+
+ UNFLAGGED
+ Messages that do not have the \Flagged flag set.
+
+ UNKEYWORD <flag>
+ Messages that do not have the specified keyword flag set.
+
+ UNSEEN
+ Messages that do not have the \Seen flag set.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 53]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
+ S: * SEARCH 2 84 882
+ S: A282 OK SEARCH completed
+ C: A283 SEARCH TEXT "string not in mailbox"
+ S: * SEARCH
+ S: A283 OK SEARCH completed
+ C: A284 SEARCH CHARSET UTF-8 TEXT {6}
+ C: XXXXXX
+ S: * SEARCH 43
+ S: A284 OK SEARCH completed
+
+ Note: Since this document is restricted to 7-bit ASCII
+ text, it is not possible to show actual UTF-8 data. The
+ "XXXXXX" is a placeholder for what would be 6 octets of
+ 8-bit data in an actual transaction.
+
+
+6.4.5. FETCH Command
+
+ Arguments: sequence set
+ message data item names or macro
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - fetch completed
+ NO - fetch error: can't fetch that data
+ BAD - command unknown or arguments invalid
+
+ The FETCH command retrieves data associated with a message in the
+ mailbox. The data items to be fetched can be either a single atom
+ or a parenthesized list.
+
+ Most data items, identified in the formal syntax under the
+ msg-att-static rule, are static and MUST NOT change for any
+ particular message. Other data items, identified in the formal
+ syntax under the msg-att-dynamic rule, MAY change, either as a
+ result of a STORE command or due to external events.
+
+ For example, if a client receives an ENVELOPE for a
+ message when it already knows the envelope, it can
+ safely ignore the newly transmitted envelope.
+
+ There are three macros which specify commonly-used sets of data
+ items, and can be used instead of data items. A macro must be
+ used by itself, and not in conjunction with other macros or data
+ items.
+
+
+
+
+
+Crispin Standards Track [Page 54]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ ALL
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)
+
+ FAST
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)
+
+ FULL
+ Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
+ BODY)
+
+ The currently defined data items that can be fetched are:
+
+ BODY
+ Non-extensible form of BODYSTRUCTURE.
+
+ BODY[<section>]<<partial>>
+ The text of a particular body section. The section
+ specification is a set of zero or more part specifiers
+ delimited by periods. A part specifier is either a part number
+ or one of the following: HEADER, HEADER.FIELDS,
+ HEADER.FIELDS.NOT, MIME, and TEXT. An empty section
+ specification refers to the entire message, including the
+ header.
+
+ Every message has at least one part number. Non-[MIME-IMB]
+ messages, and non-multipart [MIME-IMB] messages with no
+ encapsulated message, only have a part 1.
+
+ Multipart messages are assigned consecutive part numbers, as
+ they occur in the message. If a particular part is of type
+ message or multipart, its parts MUST be indicated by a period
+ followed by the part number within that nested multipart part.
+
+ A part of type MESSAGE/RFC822 also has nested part numbers,
+ referring to parts of the MESSAGE part's body.
+
+ The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part
+ specifiers can be the sole part specifier or can be prefixed by
+ one or more numeric part specifiers, provided that the numeric
+ part specifier refers to a part of type MESSAGE/RFC822. The
+ MIME part specifier MUST be prefixed by one or more numeric
+ part specifiers.
+
+ The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
+ specifiers refer to the [RFC-2822] header of the message or of
+ an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
+ HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
+ field-name (as defined in [RFC-2822]) names, and return a
+
+
+
+Crispin Standards Track [Page 55]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ subset of the header. The subset returned by HEADER.FIELDS
+ contains only those header fields with a field-name that
+ matches one of the names in the list; similarly, the subset
+ returned by HEADER.FIELDS.NOT contains only the header fields
+ with a non-matching field-name. The field-matching is
+ case-insensitive but otherwise exact. Subsetting does not
+ exclude the [RFC-2822] delimiting blank line between the header
+ and the body; the blank line is included in all header fetches,
+ except in the case of a message which has no body and no blank
+ line.
+
+ The MIME part specifier refers to the [MIME-IMB] header for
+ this part.
+
+ The TEXT part specifier refers to the text body of the message,
+ omitting the [RFC-2822] header.
+
+ Here is an example of a complex message with some of its
+ part specifiers:
+
+ HEADER ([RFC-2822] header of the message)
+ TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 1 TEXT/PLAIN
+ 2 APPLICATION/OCTET-STREAM
+ 3 MESSAGE/RFC822
+ 3.HEADER ([RFC-2822] header of the message)
+ 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 3.1 TEXT/PLAIN
+ 3.2 APPLICATION/OCTET-STREAM
+ 4 MULTIPART/MIXED
+ 4.1 IMAGE/GIF
+ 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
+ 4.2 MESSAGE/RFC822
+ 4.2.HEADER ([RFC-2822] header of the message)
+ 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
+ 4.2.1 TEXT/PLAIN
+ 4.2.2 MULTIPART/ALTERNATIVE
+ 4.2.2.1 TEXT/PLAIN
+ 4.2.2.2 TEXT/RICHTEXT
+
+
+ It is possible to fetch a substring of the designated text.
+ This is done by appending an open angle bracket ("<"), the
+ octet position of the first desired octet, a period, the
+ maximum number of octets desired, and a close angle bracket
+ (">") to the part specifier. If the starting octet is beyond
+ the end of the text, an empty string is returned.
+
+
+
+
+Crispin Standards Track [Page 56]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Any partial fetch that attempts to read beyond the end of the
+ text is truncated as appropriate. A partial fetch that starts
+ at octet 0 is returned as a partial fetch, even if this
+ truncation happened.
+
+ Note: This means that BODY[]<0.2048> of a 1500-octet message
+ will return BODY[]<0> with a literal of size 1500, not
+ BODY[].
+
+ Note: A substring fetch of a HEADER.FIELDS or
+ HEADER.FIELDS.NOT part specifier is calculated after
+ subsetting the header.
+
+ The \Seen flag is implicitly set; if this causes the flags to
+ change, they SHOULD be included as part of the FETCH responses.
+
+ BODY.PEEK[<section>]<<partial>>
+ An alternate form of BODY[<section>] that does not implicitly
+ set the \Seen flag.
+
+ BODYSTRUCTURE
+ The [MIME-IMB] body structure of the message. This is computed
+ by the server by parsing the [MIME-IMB] header fields in the
+ [RFC-2822] header and [MIME-IMB] headers.
+
+ ENVELOPE
+ The envelope structure of the message. This is computed by the
+ server by parsing the [RFC-2822] header into the component
+ parts, defaulting various fields as necessary.
+
+ FLAGS
+ The flags that are set for this message.
+
+ INTERNALDATE
+ The internal date of the message.
+
+ RFC822
+ Functionally equivalent to BODY[], differing in the syntax of
+ the resulting untagged FETCH data (RFC822 is returned).
+
+ RFC822.HEADER
+ Functionally equivalent to BODY.PEEK[HEADER], differing in the
+ syntax of the resulting untagged FETCH data (RFC822.HEADER is
+ returned).
+
+ RFC822.SIZE
+ The [RFC-2822] size of the message.
+
+
+
+
+Crispin Standards Track [Page 57]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ RFC822.TEXT
+ Functionally equivalent to BODY[TEXT], differing in the syntax
+ of the resulting untagged FETCH data (RFC822.TEXT is returned).
+
+ UID
+ The unique identifier for the message.
+
+
+ Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
+ S: * 2 FETCH ....
+ S: * 3 FETCH ....
+ S: * 4 FETCH ....
+ S: A654 OK FETCH completed
+
+
+6.4.6. STORE Command
+
+ Arguments: sequence set
+ message data item name
+ value for message data item
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - store completed
+ NO - store error: can't store that data
+ BAD - command unknown or arguments invalid
+
+ The STORE command alters data associated with a message in the
+ mailbox. Normally, STORE will return the updated value of the
+ data with an untagged FETCH response. A suffix of ".SILENT" in
+ the data item name prevents the untagged FETCH, and the server
+ SHOULD assume that the client has determined the updated value
+ itself or does not care about the updated value.
+
+ Note: Regardless of whether or not the ".SILENT" suffix
+ was used, the server SHOULD send an untagged FETCH
+ response if a change to a message's flags from an
+ external source is observed. The intent is that the
+ status of the flags is determinate without a race
+ condition.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 58]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The currently defined data items that can be stored are:
+
+ FLAGS <flag list>
+ Replace the flags for the message (other than \Recent) with the
+ argument. The new value of the flags is returned as if a FETCH
+ of those flags was done.
+
+ FLAGS.SILENT <flag list>
+ Equivalent to FLAGS, but without returning a new value.
+
+ +FLAGS <flag list>
+ Add the argument to the flags for the message. The new value
+ of the flags is returned as if a FETCH of those flags was done.
+
+ +FLAGS.SILENT <flag list>
+ Equivalent to +FLAGS, but without returning a new value.
+
+ -FLAGS <flag list>
+ Remove the argument from the flags for the message. The new
+ value of the flags is returned as if a FETCH of those flags was
+ done.
+
+ -FLAGS.SILENT <flag list>
+ Equivalent to -FLAGS, but without returning a new value.
+
+
+ Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
+ S: * 2 FETCH (FLAGS (\Deleted \Seen))
+ S: * 3 FETCH (FLAGS (\Deleted))
+ S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
+ S: A003 OK STORE completed
+
+
+6.4.7. COPY Command
+
+ Arguments: sequence set
+ mailbox name
+
+ Responses: no specific responses for this command
+
+ Result: OK - copy completed
+ NO - copy error: can't copy those messages or to that
+ name
+ BAD - command unknown or arguments invalid
+
+
+
+
+
+
+
+Crispin Standards Track [Page 59]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The COPY command copies the specified message(s) to the end of the
+ specified destination mailbox. The flags and internal date of the
+ message(s) SHOULD be preserved, and the Recent flag SHOULD be set,
+ in the copy.
+
+ If the destination mailbox does not exist, a server SHOULD return
+ an error. It SHOULD NOT automatically create the mailbox. Unless
+ it is certain that the destination mailbox can not be created, the
+ server MUST send the response code "[TRYCREATE]" as the prefix of
+ the text of the tagged NO response. This gives a hint to the
+ client that it can attempt a CREATE command and retry the COPY if
+ the CREATE is successful.
+
+ If the COPY command is unsuccessful for any reason, server
+ implementations MUST restore the destination mailbox to its state
+ before the COPY attempt.
+
+ Example: C: A003 COPY 2:4 MEETING
+ S: A003 OK COPY completed
+
+
+6.4.8. UID Command
+
+ Arguments: command name
+ command arguments
+
+ Responses: untagged responses: FETCH, SEARCH
+
+ Result: OK - UID command completed
+ NO - UID command error
+ BAD - command unknown or arguments invalid
+
+ The UID command has two forms. In the first form, it takes as its
+ arguments a COPY, FETCH, or STORE command with arguments
+ appropriate for the associated command. However, the numbers in
+ the sequence set argument are unique identifiers instead of
+ message sequence numbers. Sequence set ranges are permitted, but
+ there is no guarantee that unique identifiers will be contiguous.
+
+ A non-existent unique identifier is ignored without any error
+ message generated. Thus, it is possible for a UID FETCH command
+ to return an OK without any data or a UID COPY or UID STORE to
+ return an OK without performing any operations.
+
+ In the second form, the UID command takes a SEARCH command with
+ SEARCH command arguments. The interpretation of the arguments is
+ the same as with SEARCH; however, the numbers returned in a SEARCH
+ response for a UID SEARCH command are unique identifiers instead
+
+
+
+Crispin Standards Track [Page 60]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ of message sequence numbers. For example, the command UID SEARCH
+ 1:100 UID 443:557 returns the unique identifiers corresponding to
+ the intersection of two sequence sets, the message sequence number
+ range 1:100 and the UID range 443:557.
+
+ Note: in the above example, the UID range 443:557
+ appears. The same comment about a non-existent unique
+ identifier being ignored without any error message also
+ applies here. Hence, even if neither UID 443 or 557
+ exist, this range is valid and would include an existing
+ UID 495.
+
+ Also note that a UID range of 559:* always includes the
+ UID of the last message in the mailbox, even if 559 is
+ higher than any assigned UID value. This is because the
+ contents of a range are independent of the order of the
+ range endpoints. Thus, any UID range with * as one of
+ the endpoints indicates at least one message (the
+ message with the highest numbered UID), unless the
+ mailbox is empty.
+
+ The number after the "*" in an untagged FETCH response is always a
+ message sequence number, not a unique identifier, even for a UID
+ command response. However, server implementations MUST implicitly
+ include the UID message data item as part of any FETCH response
+ caused by a UID command, regardless of whether a UID was specified
+ as a message data item to the FETCH.
+
+
+ Note: The rule about including the UID message data item as part
+ of a FETCH response primarily applies to the UID FETCH and UID
+ STORE commands, including a UID FETCH command that does not
+ include UID as a message data item. Although it is unlikely that
+ the other UID commands will cause an untagged FETCH, this rule
+ applies to these commands as well.
+
+ Example: C: A999 UID FETCH 4827313:4828442 FLAGS
+ S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
+ S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
+ S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
+ S: A999 OK UID FETCH completed
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 61]
+
+RFC 3501 IMAPv4 March 2003
+
+
+6.5. Client Commands - Experimental/Expansion
+
+
+6.5.1. X<atom> Command
+
+ Arguments: implementation defined
+
+ Responses: implementation defined
+
+ Result: OK - command completed
+ NO - failure
+ BAD - command unknown or arguments invalid
+
+ Any command prefixed with an X is an experimental command.
+ Commands which are not part of this specification, a standard or
+ standards-track revision of this specification, or an
+ IESG-approved experimental protocol, MUST use the X prefix.
+
+ Any added untagged responses issued by an experimental command
+ MUST also be prefixed with an X. Server implementations MUST NOT
+ send any such untagged responses, unless the client requested it
+ by issuing the associated experimental command.
+
+ Example: C: a441 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 XPIG-LATIN
+ S: a441 OK CAPABILITY completed
+ C: A442 XPIG-LATIN
+ S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
+ S: A442 OK XPIG-LATIN ompleted-cay
+
+7. Server Responses
+
+ Server responses are in three forms: status responses, server data,
+ and command continuation request. The information contained in a
+ server response, identified by "Contents:" in the response
+ descriptions below, is described by function, not by syntax. The
+ precise syntax of server responses is described in the Formal Syntax
+ section.
+
+ The client MUST be prepared to accept any response at all times.
+
+ Status responses can be tagged or untagged. Tagged status responses
+ indicate the completion result (OK, NO, or BAD status) of a client
+ command, and have a tag matching the command.
+
+ Some status responses, and all server data, are untagged. An
+ untagged response is indicated by the token "*" instead of a tag.
+ Untagged status responses indicate server greeting, or server status
+
+
+
+Crispin Standards Track [Page 62]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ that does not indicate the completion of a command (for example, an
+ impending system shutdown alert). For historical reasons, untagged
+ server data responses are also called "unsolicited data", although
+ strictly speaking, only unilateral server data is truly
+ "unsolicited".
+
+ Certain server data MUST be recorded by the client when it is
+ received; this is noted in the description of that data. Such data
+ conveys critical information which affects the interpretation of all
+ subsequent commands and responses (e.g., updates reflecting the
+ creation or destruction of messages).
+
+ Other server data SHOULD be recorded for later reference; if the
+ client does not need to record the data, or if recording the data has
+ no obvious purpose (e.g., a SEARCH response when no SEARCH command is
+ in progress), the data SHOULD be ignored.
+
+ An example of unilateral untagged server data occurs when the IMAP
+ connection is in the selected state. In the selected state, the
+ server checks the mailbox for new messages as part of command
+ execution. Normally, this is part of the execution of every command;
+ hence, a NOOP command suffices to check for new messages. If new
+ messages are found, the server sends untagged EXISTS and RECENT
+ responses reflecting the new size of the mailbox. Server
+ implementations that offer multiple simultaneous access to the same
+ mailbox SHOULD also send appropriate unilateral untagged FETCH and
+ EXPUNGE responses if another agent changes the state of any message
+ flags or expunges any messages.
+
+ Command continuation request responses use the token "+" instead of a
+ tag. These responses are sent by the server to indicate acceptance
+ of an incomplete client command and readiness for the remainder of
+ the command.
+
+7.1. Server Responses - Status Responses
+
+ Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD
+ can be tagged or untagged. PREAUTH and BYE are always untagged.
+
+ Status responses MAY include an OPTIONAL "response code". A response
+ code consists of data inside square brackets in the form of an atom,
+ possibly followed by a space and arguments. The response code
+ contains additional information or status codes for client software
+ beyond the OK/NO/BAD condition, and are defined when there is a
+ specific action that a client can take based upon the additional
+ information.
+
+
+
+
+
+Crispin Standards Track [Page 63]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The currently defined response codes are:
+
+ ALERT
+
+ The human-readable text contains a special alert that MUST be
+ presented to the user in a fashion that calls the user's
+ attention to the message.
+
+ BADCHARSET
+
+ Optionally followed by a parenthesized list of charsets. A
+ SEARCH failed because the given charset is not supported by
+ this implementation. If the optional list of charsets is
+ given, this lists the charsets that are supported by this
+ implementation.
+
+ CAPABILITY
+
+ Followed by a list of capabilities. This can appear in the
+ initial OK or PREAUTH response to transmit an initial
+ capabilities list. This makes it unnecessary for a client to
+ send a separate CAPABILITY command if it recognizes this
+ response.
+
+ PARSE
+
+ The human-readable text represents an error in parsing the
+ [RFC-2822] header or [MIME-IMB] headers of a message in the
+ mailbox.
+
+ PERMANENTFLAGS
+
+ Followed by a parenthesized list of flags, indicates which of
+ the known flags the client can change permanently. Any flags
+ that are in the FLAGS untagged response, but not the
+ PERMANENTFLAGS list, can not be set permanently. If the client
+ attempts to STORE a flag that is not in the PERMANENTFLAGS
+ list, the server will either ignore the change or store the
+ state change for the remainder of the current session only.
+ The PERMANENTFLAGS list can also include the special flag \*,
+ which indicates that it is possible to create new keywords by
+ attempting to store those flags in the mailbox.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 64]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ READ-ONLY
+
+ The mailbox is selected read-only, or its access while selected
+ has changed from read-write to read-only.
+
+ READ-WRITE
+
+ The mailbox is selected read-write, or its access while
+ selected has changed from read-only to read-write.
+
+ TRYCREATE
+
+ An APPEND or COPY attempt is failing because the target mailbox
+ does not exist (as opposed to some other reason). This is a
+ hint to the client that the operation can succeed if the
+ mailbox is first created by the CREATE command.
+
+ UIDNEXT
+
+ Followed by a decimal number, indicates the next unique
+ identifier value. Refer to section 2.3.1.1 for more
+ information.
+
+ UIDVALIDITY
+
+ Followed by a decimal number, indicates the unique identifier
+ validity value. Refer to section 2.3.1.1 for more information.
+
+ UNSEEN
+
+ Followed by a decimal number, indicates the number of the first
+ message without the \Seen flag set.
+
+ Additional response codes defined by particular client or server
+ implementations SHOULD be prefixed with an "X" until they are
+ added to a revision of this protocol. Client implementations
+ SHOULD ignore response codes that they do not recognize.
+
+7.1.1. OK Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The OK response indicates an information message from the server.
+ When tagged, it indicates successful completion of the associated
+ command. The human-readable text MAY be presented to the user as
+ an information message. The untagged form indicates an
+
+
+
+
+Crispin Standards Track [Page 65]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ information-only message; the nature of the information MAY be
+ indicated by a response code.
+
+ The untagged form is also used as one of three possible greetings
+ at connection startup. It indicates that the connection is not
+ yet authenticated and that a LOGIN command is needed.
+
+ Example: S: * OK IMAP4rev1 server ready
+ C: A001 LOGIN fred blurdybloop
+ S: * OK [ALERT] System shutdown in 10 minutes
+ S: A001 OK LOGIN Completed
+
+
+7.1.2. NO Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The NO response indicates an operational error message from the
+ server. When tagged, it indicates unsuccessful completion of the
+ associated command. The untagged form indicates a warning; the
+ command can still complete successfully. The human-readable text
+ describes the condition.
+
+ Example: C: A222 COPY 1:2 owatagusiam
+ S: * NO Disk is 98% full, please delete unnecessary data
+ S: A222 OK COPY completed
+ C: A223 COPY 3:200 blurdybloop
+ S: * NO Disk is 98% full, please delete unnecessary data
+ S: * NO Disk is 99% full, please delete unnecessary data
+ S: A223 NO COPY failed: disk is full
+
+
+7.1.3. BAD Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The BAD response indicates an error message from the server. When
+ tagged, it reports a protocol-level error in the client's command;
+ the tag indicates the command that caused the error. The untagged
+ form indicates a protocol-level error for which the associated
+ command can not be determined; it can also indicate an internal
+ server failure. The human-readable text describes the condition.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 66]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Example: C: ...very long command line...
+ S: * BAD Command line too long
+ C: ...empty line...
+ S: * BAD Empty command line
+ C: A443 EXPUNGE
+ S: * BAD Disk crash, attempting salvage to a new disk!
+ S: * OK Salvage successful, no data lost
+ S: A443 OK Expunge completed
+
+
+7.1.4. PREAUTH Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The PREAUTH response is always untagged, and is one of three
+ possible greetings at connection startup. It indicates that the
+ connection has already been authenticated by external means; thus
+ no LOGIN command is needed.
+
+ Example: S: * PREAUTH IMAP4rev1 server logged in as Smith
+
+
+7.1.5. BYE Response
+
+ Contents: OPTIONAL response code
+ human-readable text
+
+ The BYE response is always untagged, and indicates that the server
+ is about to close the connection. The human-readable text MAY be
+ displayed to the user in a status report by the client. The BYE
+ response is sent under one of four conditions:
+
+ 1) as part of a normal logout sequence. The server will close
+ the connection after sending the tagged OK response to the
+ LOGOUT command.
+
+ 2) as a panic shutdown announcement. The server closes the
+ connection immediately.
+
+ 3) as an announcement of an inactivity autologout. The server
+ closes the connection immediately.
+
+ 4) as one of three possible greetings at connection startup,
+ indicating that the server is not willing to accept a
+ connection from this client. The server closes the
+ connection immediately.
+
+
+
+
+Crispin Standards Track [Page 67]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The difference between a BYE that occurs as part of a normal
+ LOGOUT sequence (the first case) and a BYE that occurs because of
+ a failure (the other three cases) is that the connection closes
+ immediately in the failure case. In all cases the client SHOULD
+ continue to read response data from the server until the
+ connection is closed; this will ensure that any pending untagged
+ or completion responses are read and processed.
+
+ Example: S: * BYE Autologout; idle for too long
+
+7.2. Server Responses - Server and Mailbox Status
+
+ These responses are always untagged. This is how server and mailbox
+ status data are transmitted from the server to the client. Many of
+ these responses typically result from a command with the same name.
+
+7.2.1. CAPABILITY Response
+
+ Contents: capability listing
+
+ The CAPABILITY response occurs as a result of a CAPABILITY
+ command. The capability listing contains a space-separated
+ listing of capability names that the server supports. The
+ capability listing MUST include the atom "IMAP4rev1".
+
+ In addition, client and server implementations MUST implement the
+ STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
+ capabilities. See the Security Considerations section for
+ important information.
+
+ A capability name which begins with "AUTH=" indicates that the
+ server supports that particular authentication mechanism.
+
+ The LOGINDISABLED capability indicates that the LOGIN command is
+ disabled, and that the server will respond with a tagged NO
+ response to any attempt to use the LOGIN command even if the user
+ name and password are valid. An IMAP client MUST NOT issue the
+ LOGIN command if the server advertises the LOGINDISABLED
+ capability.
+
+ Other capability names indicate that the server supports an
+ extension, revision, or amendment to the IMAP4rev1 protocol.
+ Server responses MUST conform to this document until the client
+ issues a command that uses the associated capability.
+
+ Capability names MUST either begin with "X" or be standard or
+ standards-track IMAP4rev1 extensions, revisions, or amendments
+ registered with IANA. A server MUST NOT offer unregistered or
+
+
+
+Crispin Standards Track [Page 68]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ non-standard capability names, unless such names are prefixed with
+ an "X".
+
+ Client implementations SHOULD NOT require any capability name
+ other than "IMAP4rev1", and MUST ignore any unknown capability
+ names.
+
+ A server MAY send capabilities automatically, by using the
+ CAPABILITY response code in the initial PREAUTH or OK responses,
+ and by sending an updated CAPABILITY response code in the tagged
+ OK response as part of a successful authentication. It is
+ unnecessary for a client to send a separate CAPABILITY command if
+ it recognizes these automatic capabilities.
+
+ Example: S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI XPIG-LATIN
+
+
+7.2.2. LIST Response
+
+ Contents: name attributes
+ hierarchy delimiter
+ name
+
+ The LIST response occurs as a result of a LIST command. It
+ returns a single name that matches the LIST specification. There
+ can be multiple LIST responses for a single LIST command.
+
+ Four name attributes are defined:
+
+ \Noinferiors
+ It is not possible for any child levels of hierarchy to exist
+ under this name; no child levels exist now and none can be
+ created in the future.
+
+ \Noselect
+ It is not possible to use this name as a selectable mailbox.
+
+ \Marked
+ The mailbox has been marked "interesting" by the server; the
+ mailbox probably contains messages that have been added since
+ the last time the mailbox was selected.
+
+ \Unmarked
+ The mailbox does not contain any additional messages since the
+ last time the mailbox was selected.
+
+
+
+
+
+
+Crispin Standards Track [Page 69]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ If it is not feasible for the server to determine whether or not
+ the mailbox is "interesting", or if the name is a \Noselect name,
+ the server SHOULD NOT send either \Marked or \Unmarked.
+
+ The hierarchy delimiter is a character used to delimit levels of
+ hierarchy in a mailbox name. A client can use it to create child
+ mailboxes, and to search higher or lower levels of naming
+ hierarchy. All children of a top-level hierarchy node MUST use
+ the same separator character. A NIL hierarchy delimiter means
+ that no hierarchy exists; the name is a "flat" name.
+
+ The name represents an unambiguous left-to-right hierarchy, and
+ MUST be valid for use as a reference in LIST and LSUB commands.
+ Unless \Noselect is indicated, the name MUST also be valid as an
+ argument for commands, such as SELECT, that accept mailbox names.
+
+ Example: S: * LIST (\Noselect) "/" ~/Mail/foo
+
+
+7.2.3. LSUB Response
+
+ Contents: name attributes
+ hierarchy delimiter
+ name
+
+ The LSUB response occurs as a result of an LSUB command. It
+ returns a single name that matches the LSUB specification. There
+ can be multiple LSUB responses for a single LSUB command. The
+ data is identical in format to the LIST response.
+
+ Example: S: * LSUB () "." #news.comp.mail.misc
+
+
+7.2.4 STATUS Response
+
+ Contents: name
+ status parenthesized list
+
+ The STATUS response occurs as a result of an STATUS command. It
+ returns the mailbox name that matches the STATUS specification and
+ the requested mailbox status information.
+
+ Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 70]
+
+RFC 3501 IMAPv4 March 2003
+
+
+7.2.5. SEARCH Response
+
+ Contents: zero or more numbers
+
+ The SEARCH response occurs as a result of a SEARCH or UID SEARCH
+ command. The number(s) refer to those messages that match the
+ search criteria. For SEARCH, these are message sequence numbers;
+ for UID SEARCH, these are unique identifiers. Each number is
+ delimited by a space.
+
+ Example: S: * SEARCH 2 3 6
+
+
+7.2.6. FLAGS Response
+
+ Contents: flag parenthesized list
+
+ The FLAGS response occurs as a result of a SELECT or EXAMINE
+ command. The flag parenthesized list identifies the flags (at a
+ minimum, the system-defined flags) that are applicable for this
+ mailbox. Flags other than the system flags can also exist,
+ depending on server implementation.
+
+ The update from the FLAGS response MUST be recorded by the client.
+
+ Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+
+
+7.3. Server Responses - Mailbox Size
+
+ These responses are always untagged. This is how changes in the size
+ of the mailbox are transmitted from the server to the client.
+ Immediately following the "*" token is a number that represents a
+ message count.
+
+7.3.1. EXISTS Response
+
+ Contents: none
+
+ The EXISTS response reports the number of messages in the mailbox.
+ This response occurs as a result of a SELECT or EXAMINE command,
+ and if the size of the mailbox changes (e.g., new messages).
+
+ The update from the EXISTS response MUST be recorded by the
+ client.
+
+ Example: S: * 23 EXISTS
+
+
+
+
+Crispin Standards Track [Page 71]
+
+RFC 3501 IMAPv4 March 2003
+
+
+7.3.2. RECENT Response
+
+ Contents: none
+
+ The RECENT response reports the number of messages with the
+ \Recent flag set. This response occurs as a result of a SELECT or
+ EXAMINE command, and if the size of the mailbox changes (e.g., new
+ messages).
+
+ Note: It is not guaranteed that the message sequence
+ numbers of recent messages will be a contiguous range of
+ the highest n messages in the mailbox (where n is the
+ value reported by the RECENT response). Examples of
+ situations in which this is not the case are: multiple
+ clients having the same mailbox open (the first session
+ to be notified will see it as recent, others will
+ probably see it as non-recent), and when the mailbox is
+ re-ordered by a non-IMAP agent.
+
+ The only reliable way to identify recent messages is to
+ look at message flags to see which have the \Recent flag
+ set, or to do a SEARCH RECENT.
+
+ The update from the RECENT response MUST be recorded by the
+ client.
+
+ Example: S: * 5 RECENT
+
+
+7.4. Server Responses - Message Status
+
+ These responses are always untagged. This is how message data are
+ transmitted from the server to the client, often as a result of a
+ command with the same name. Immediately following the "*" token is a
+ number that represents a message sequence number.
+
+7.4.1. EXPUNGE Response
+
+ Contents: none
+
+ The EXPUNGE response reports that the specified message sequence
+ number has been permanently removed from the mailbox. The message
+ sequence number for each successive message in the mailbox is
+ immediately decremented by 1, and this decrement is reflected in
+ message sequence numbers in subsequent responses (including other
+ untagged EXPUNGE responses).
+
+
+
+
+
+Crispin Standards Track [Page 72]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ The EXPUNGE response also decrements the number of messages in the
+ mailbox; it is not necessary to send an EXISTS response with the
+ new value.
+
+ As a result of the immediate decrement rule, message sequence
+ numbers that appear in a set of successive EXPUNGE responses
+ depend upon whether the messages are removed starting from lower
+ numbers to higher numbers, or from higher numbers to lower
+ numbers. For example, if the last 5 messages in a 9-message
+ mailbox are expunged, a "lower to higher" server will send five
+ untagged EXPUNGE responses for message sequence number 5, whereas
+ a "higher to lower server" will send successive untagged EXPUNGE
+ responses for message sequence numbers 9, 8, 7, 6, and 5.
+
+ An EXPUNGE response MUST NOT be sent when no command is in
+ progress, nor while responding to a FETCH, STORE, or SEARCH
+ command. This rule is necessary to prevent a loss of
+ synchronization of message sequence numbers between client and
+ server. A command is not "in progress" until the complete command
+ has been received; in particular, a command is not "in progress"
+ during the negotiation of command continuation.
+
+ Note: UID FETCH, UID STORE, and UID SEARCH are different
+ commands from FETCH, STORE, and SEARCH. An EXPUNGE
+ response MAY be sent during a UID command.
+
+ The update from the EXPUNGE response MUST be recorded by the
+ client.
+
+ Example: S: * 44 EXPUNGE
+
+
+7.4.2. FETCH Response
+
+ Contents: message data
+
+ The FETCH response returns data about a message to the client.
+ The data are pairs of data item names and their values in
+ parentheses. This response occurs as the result of a FETCH or
+ STORE command, as well as by unilateral server decision (e.g.,
+ flag updates).
+
+ The current data items are:
+
+ BODY
+ A form of BODYSTRUCTURE without extension data.
+
+
+
+
+
+Crispin Standards Track [Page 73]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BODY[<section>]<<origin octet>>
+ A string expressing the body contents of the specified section.
+ The string SHOULD be interpreted by the client according to the
+ content transfer encoding, body type, and subtype.
+
+ If the origin octet is specified, this string is a substring of
+ the entire body contents, starting at that origin octet. This
+ means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
+ truncated.
+
+ Note: The origin octet facility MUST NOT be used by a server
+ in a FETCH response unless the client specifically requested
+ it by means of a FETCH of a BODY[<section>]<<partial>> data
+ item.
+
+ 8-bit textual data is permitted if a [CHARSET] identifier is
+ part of the body parameter parenthesized list for this section.
+ Note that headers (part specifiers HEADER or MIME, or the
+ header portion of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
+ characters are not permitted in headers. Note also that the
+ [RFC-2822] delimiting blank line between the header and the
+ body is not affected by header line subsetting; the blank line
+ is always included as part of header data, except in the case
+ of a message which has no body and no blank line.
+
+ Non-textual data such as binary data MUST be transfer encoded
+ into a textual form, such as BASE64, prior to being sent to the
+ client. To derive the original binary data, the client MUST
+ decode the transfer encoded string.
+
+ BODYSTRUCTURE
+ A parenthesized list that describes the [MIME-IMB] body
+ structure of a message. This is computed by the server by
+ parsing the [MIME-IMB] header fields, defaulting various fields
+ as necessary.
+
+ For example, a simple text message of 48 lines and 2279 octets
+ can have a body structure of: ("TEXT" "PLAIN" ("CHARSET"
+ "US-ASCII") NIL NIL "7BIT" 2279 48)
+
+ Multiple parts are indicated by parenthesis nesting. Instead
+ of a body type as the first element of the parenthesized list,
+ there is a sequence of one or more nested body structures. The
+ second element of the parenthesized list is the multipart
+ subtype (mixed, digest, parallel, alternative, etc.).
+
+
+
+
+
+
+Crispin Standards Track [Page 74]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ For example, a two part message consisting of a text and a
+ BASE64-encoded text attachment can have a body structure of:
+ (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
+ 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
+ "<960723163407.20117h@cac.washington.edu>" "Compiler diff"
+ "BASE64" 4554 73) "MIXED")
+
+ Extension data follows the multipart subtype. Extension data
+ is never returned with the BODY fetch, but can be returned with
+ a BODYSTRUCTURE fetch. Extension data, if present, MUST be in
+ the defined order. The extension data of a multipart body part
+ are in the following order:
+
+ body parameter parenthesized list
+ A parenthesized list of attribute/value pairs [e.g., ("foo"
+ "bar" "baz" "rag") where "bar" is the value of "foo", and
+ "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+ body disposition
+ A parenthesized list, consisting of a disposition type
+ string, followed by a parenthesized list of disposition
+ attribute/value pairs as defined in [DISPOSITION].
+
+ body language
+ A string or parenthesized list giving the body language
+ value as defined in [LANGUAGE-TAGS].
+
+ body location
+ A string list giving the body content URI as defined in
+ [LOCATION].
+
+ Any following extension data are not yet defined in this
+ version of the protocol. Such extension data can consist of
+ zero or more NILs, strings, numbers, or potentially nested
+ parenthesized lists of such data. Client implementations that
+ do a BODYSTRUCTURE fetch MUST be prepared to accept such
+ extension data. Server implementations MUST NOT send such
+ extension data until it has been defined by a revision of this
+ protocol.
+
+ The basic fields of a non-multipart body part are in the
+ following order:
+
+ body type
+ A string giving the content media type name as defined in
+ [MIME-IMB].
+
+
+
+
+
+Crispin Standards Track [Page 75]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ body subtype
+ A string giving the content subtype name as defined in
+ [MIME-IMB].
+
+ body parameter parenthesized list
+ A parenthesized list of attribute/value pairs [e.g., ("foo"
+ "bar" "baz" "rag") where "bar" is the value of "foo" and
+ "rag" is the value of "baz"] as defined in [MIME-IMB].
+
+ body id
+ A string giving the content id as defined in [MIME-IMB].
+
+ body description
+ A string giving the content description as defined in
+ [MIME-IMB].
+
+ body encoding
+ A string giving the content transfer encoding as defined in
+ [MIME-IMB].
+
+ body size
+ A number giving the size of the body in octets. Note that
+ this size is the size in its transfer encoding and not the
+ resulting size after any decoding.
+
+ A body type of type MESSAGE and subtype RFC822 contains,
+ immediately after the basic fields, the envelope structure,
+ body structure, and size in text lines of the encapsulated
+ message.
+
+ A body type of type TEXT contains, immediately after the basic
+ fields, the size of the body in text lines. Note that this
+ size is the size in its content transfer encoding and not the
+ resulting size after any decoding.
+
+ Extension data follows the basic fields and the type-specific
+ fields listed above. Extension data is never returned with the
+ BODY fetch, but can be returned with a BODYSTRUCTURE fetch.
+ Extension data, if present, MUST be in the defined order.
+
+ The extension data of a non-multipart body part are in the
+ following order:
+
+ body MD5
+ A string giving the body MD5 value as defined in [MD5].
+
+
+
+
+
+
+Crispin Standards Track [Page 76]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ body disposition
+ A parenthesized list with the same content and function as
+ the body disposition for a multipart body part.
+
+ body language
+ A string or parenthesized list giving the body language
+ value as defined in [LANGUAGE-TAGS].
+
+ body location
+ A string list giving the body content URI as defined in
+ [LOCATION].
+
+ Any following extension data are not yet defined in this
+ version of the protocol, and would be as described above under
+ multipart extension data.
+
+ ENVELOPE
+ A parenthesized list that describes the envelope structure of a
+ message. This is computed by the server by parsing the
+ [RFC-2822] header into the component parts, defaulting various
+ fields as necessary.
+
+ The fields of the envelope structure are in the following
+ order: date, subject, from, sender, reply-to, to, cc, bcc,
+ in-reply-to, and message-id. The date, subject, in-reply-to,
+ and message-id fields are strings. The from, sender, reply-to,
+ to, cc, and bcc fields are parenthesized lists of address
+ structures.
+
+ An address structure is a parenthesized list that describes an
+ electronic mail address. The fields of an address structure
+ are in the following order: personal name, [SMTP]
+ at-domain-list (source route), mailbox name, and host name.
+
+ [RFC-2822] group syntax is indicated by a special form of
+ address structure in which the host name field is NIL. If the
+ mailbox name field is also NIL, this is an end of group marker
+ (semi-colon in RFC 822 syntax). If the mailbox name field is
+ non-NIL, this is a start of group marker, and the mailbox name
+ field holds the group name phrase.
+
+ If the Date, Subject, In-Reply-To, and Message-ID header lines
+ are absent in the [RFC-2822] header, the corresponding member
+ of the envelope is NIL; if these header lines are present but
+ empty the corresponding member of the envelope is the empty
+ string.
+
+
+
+
+
+Crispin Standards Track [Page 77]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Note: some servers may return a NIL envelope member in the
+ "present but empty" case. Clients SHOULD treat NIL and
+ empty string as identical.
+
+ Note: [RFC-2822] requires that all messages have a valid
+ Date header. Therefore, the date member in the envelope can
+ not be NIL or the empty string.
+
+ Note: [RFC-2822] requires that the In-Reply-To and
+ Message-ID headers, if present, have non-empty content.
+ Therefore, the in-reply-to and message-id members in the
+ envelope can not be the empty string.
+
+ If the From, To, cc, and bcc header lines are absent in the
+ [RFC-2822] header, or are present but empty, the corresponding
+ member of the envelope is NIL.
+
+ If the Sender or Reply-To lines are absent in the [RFC-2822]
+ header, or are present but empty, the server sets the
+ corresponding member of the envelope to be the same value as
+ the from member (the client is not expected to know to do
+ this).
+
+ Note: [RFC-2822] requires that all messages have a valid
+ From header. Therefore, the from, sender, and reply-to
+ members in the envelope can not be NIL.
+
+ FLAGS
+ A parenthesized list of flags that are set for this message.
+
+ INTERNALDATE
+ A string representing the internal date of the message.
+
+ RFC822
+ Equivalent to BODY[].
+
+ RFC822.HEADER
+ Equivalent to BODY[HEADER]. Note that this did not result in
+ \Seen being set, because RFC822.HEADER response data occurs as
+ a result of a FETCH of RFC822.HEADER. BODY[HEADER] response
+ data occurs as a result of a FETCH of BODY[HEADER] (which sets
+ \Seen) or BODY.PEEK[HEADER] (which does not set \Seen).
+
+ RFC822.SIZE
+ A number expressing the [RFC-2822] size of the message.
+
+
+
+
+
+
+Crispin Standards Track [Page 78]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ RFC822.TEXT
+ Equivalent to BODY[TEXT].
+
+ UID
+ A number expressing the unique identifier of the message.
+
+
+ Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
+
+
+7.5. Server Responses - Command Continuation Request
+
+ The command continuation request response is indicated by a "+" token
+ instead of a tag. This form of response indicates that the server is
+ ready to accept the continuation of a command from the client. The
+ remainder of this response is a line of text.
+
+ This response is used in the AUTHENTICATE command to transmit server
+ data to the client, and request additional client data. This
+ response is also used if an argument to any command is a literal.
+
+ The client is not permitted to send the octets of the literal unless
+ the server indicates that it is expected. This permits the server to
+ process commands and reject errors on a line-by-line basis. The
+ remainder of the command, including the CRLF that terminates a
+ command, follows the octets of the literal. If there are any
+ additional command arguments, the literal octets are followed by a
+ space and those arguments.
+
+ Example: C: A001 LOGIN {11}
+ S: + Ready for additional command text
+ C: FRED FOOBAR {7}
+ S: + Ready for additional command text
+ C: fat man
+ S: A001 OK LOGIN completed
+ C: A044 BLURDYBLOOP {102856}
+ S: A044 BAD No such command as "BLURDYBLOOP"
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 79]
+
+RFC 3501 IMAPv4 March 2003
+
+
+8. Sample IMAP4rev1 connection
+
+ The following is a transcript of an IMAP4rev1 connection. A long
+ line in this sample is broken for editorial clarity.
+
+S: * OK IMAP4rev1 Service Ready
+C: a001 login mrc secret
+S: a001 OK LOGIN completed
+C: a002 select inbox
+S: * 18 EXISTS
+S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+S: * 2 RECENT
+S: * OK [UNSEEN 17] Message 17 is the first unseen message
+S: * OK [UIDVALIDITY 3857529045] UIDs valid
+S: a002 OK [READ-WRITE] SELECT completed
+C: a003 fetch 12 full
+S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
+ RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
+ "IMAP4rev1 WG mtg summary and minutes"
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ (("Terry Gray" NIL "gray" "cac.washington.edu"))
+ ((NIL NIL "imap" "cac.washington.edu"))
+ ((NIL NIL "minutes" "CNRI.Reston.VA.US")
+ ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL
+ "<B27397-0100000@cac.washington.edu>")
+ BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028
+ 92))
+S: a003 OK FETCH completed
+C: a004 fetch 12 body[header]
+S: * 12 FETCH (BODY[HEADER] {342}
+S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
+S: From: Terry Gray <gray@cac.washington.edu>
+S: Subject: IMAP4rev1 WG mtg summary and minutes
+S: To: imap@cac.washington.edu
+S: cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@MIT.EDU>
+S: Message-Id: <B27397-0100000@cac.washington.edu>
+S: MIME-Version: 1.0
+S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+S:
+S: )
+S: a004 OK FETCH completed
+C: a005 store 12 +flags \deleted
+S: * 12 FETCH (FLAGS (\Seen \Deleted))
+S: a005 OK +FLAGS completed
+C: a006 logout
+S: * BYE IMAP4rev1 server terminating connection
+S: a006 OK LOGOUT completed
+
+
+
+Crispin Standards Track [Page 80]
+
+RFC 3501 IMAPv4 March 2003
+
+
+9. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ In the case of alternative or optional rules in which a later rule
+ overlaps an earlier rule, the rule which is listed earlier MUST take
+ priority. For example, "\Seen" when parsed as a flag is the \Seen
+ flag name and not a flag-extension, even though "\Seen" can be parsed
+ as a flag-extension. Some, but not all, instances of this rule are
+ noted below.
+
+ Note: [ABNF] rules MUST be followed strictly; in
+ particular:
+
+ (1) Except as noted otherwise, all alphabetic characters
+ are case-insensitive. The use of upper or lower case
+ characters to define token strings is for editorial clarity
+ only. Implementations MUST accept these strings in a
+ case-insensitive fashion.
+
+ (2) In all cases, SP refers to exactly one space. It is
+ NOT permitted to substitute TAB, insert additional spaces,
+ or otherwise treat SP as being equivalent to LWSP.
+
+ (3) The ASCII NUL character, %x00, MUST NOT be used at any
+ time.
+
+address = "(" addr-name SP addr-adl SP addr-mailbox SP
+ addr-host ")"
+
+addr-adl = nstring
+ ; Holds route from [RFC-2822] route-addr if
+ ; non-NIL
+
+addr-host = nstring
+ ; NIL indicates [RFC-2822] group syntax.
+ ; Otherwise, holds [RFC-2822] domain name
+
+addr-mailbox = nstring
+ ; NIL indicates end of [RFC-2822] group; if
+ ; non-NIL and addr-host is NIL, holds
+ ; [RFC-2822] group name.
+ ; Otherwise, holds [RFC-2822] local-part
+ ; after removing [RFC-2822] quoting
+
+
+
+
+
+
+Crispin Standards Track [Page 81]
+
+RFC 3501 IMAPv4 March 2003
+
+
+addr-name = nstring
+ ; If non-NIL, holds phrase from [RFC-2822]
+ ; mailbox after removing [RFC-2822] quoting
+
+append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
+ literal
+
+astring = 1*ASTRING-CHAR / string
+
+ASTRING-CHAR = ATOM-CHAR / resp-specials
+
+atom = 1*ATOM-CHAR
+
+ATOM-CHAR = <any CHAR except atom-specials>
+
+atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards /
+ quoted-specials / resp-specials
+
+authenticate = "AUTHENTICATE" SP auth-type *(CRLF base64)
+
+auth-type = atom
+ ; Defined by [SASL]
+
+base64 = *(4base64-char) [base64-terminal]
+
+base64-char = ALPHA / DIGIT / "+" / "/"
+ ; Case-sensitive
+
+base64-terminal = (2base64-char "==") / (3base64-char "=")
+
+body = "(" (body-type-1part / body-type-mpart) ")"
+
+body-extension = nstring / number /
+ "(" body-extension *(SP body-extension) ")"
+ ; Future expansion. Client implementations
+ ; MUST accept body-extension fields. Server
+ ; implementations MUST NOT generate
+ ; body-extension fields except as defined by
+ ; future standard or standards-track
+ ; revisions of this specification.
+
+body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
+ [SP body-fld-loc *(SP body-extension)]]]
+ ; MUST NOT be returned on non-extensible
+ ; "BODY" fetch
+
+
+
+
+
+
+Crispin Standards Track [Page 82]
+
+RFC 3501 IMAPv4 March 2003
+
+
+body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang
+ [SP body-fld-loc *(SP body-extension)]]]
+ ; MUST NOT be returned on non-extensible
+ ; "BODY" fetch
+
+body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP
+ body-fld-enc SP body-fld-octets
+
+body-fld-desc = nstring
+
+body-fld-dsp = "(" string SP body-fld-param ")" / nil
+
+body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
+ "QUOTED-PRINTABLE") DQUOTE) / string
+
+body-fld-id = nstring
+
+body-fld-lang = nstring / "(" string *(SP string) ")"
+
+body-fld-loc = nstring
+
+body-fld-lines = number
+
+body-fld-md5 = nstring
+
+body-fld-octets = number
+
+body-fld-param = "(" string SP string *(SP string SP string) ")" / nil
+
+body-type-1part = (body-type-basic / body-type-msg / body-type-text)
+ [SP body-ext-1part]
+
+body-type-basic = media-basic SP body-fields
+ ; MESSAGE subtype MUST NOT be "RFC822"
+
+body-type-mpart = 1*body SP media-subtype
+ [SP body-ext-mpart]
+
+body-type-msg = media-message SP body-fields SP envelope
+ SP body SP body-fld-lines
+
+body-type-text = media-text SP body-fields SP body-fld-lines
+
+capability = ("AUTH=" auth-type) / atom
+ ; New capabilities MUST begin with "X" or be
+ ; registered with IANA as standard or
+ ; standards-track
+
+
+
+
+Crispin Standards Track [Page 83]
+
+RFC 3501 IMAPv4 March 2003
+
+
+capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev1"
+ *(SP capability)
+ ; Servers MUST implement the STARTTLS, AUTH=PLAIN,
+ ; and LOGINDISABLED capabilities
+ ; Servers which offer RFC 1730 compatibility MUST
+ ; list "IMAP4" as the first capability.
+
+CHAR8 = %x01-ff
+ ; any OCTET except NUL, %x00
+
+command = tag SP (command-any / command-auth / command-nonauth /
+ command-select) CRLF
+ ; Modal based on state
+
+command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command
+ ; Valid in all states
+
+command-auth = append / create / delete / examine / list / lsub /
+ rename / select / status / subscribe / unsubscribe
+ ; Valid only in Authenticated or Selected state
+
+command-nonauth = login / authenticate / "STARTTLS"
+ ; Valid only when in Not Authenticated state
+
+command-select = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
+ uid / search
+ ; Valid only when in Selected state
+
+continue-req = "+" SP (resp-text / base64) CRLF
+
+copy = "COPY" SP sequence-set SP mailbox
+
+create = "CREATE" SP mailbox
+ ; Use of INBOX gives a NO error
+
+date = date-text / DQUOTE date-text DQUOTE
+
+date-day = 1*2DIGIT
+ ; Day of month
+
+date-day-fixed = (SP DIGIT) / 2DIGIT
+ ; Fixed-format version of date-day
+
+date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
+ "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
+
+date-text = date-day "-" date-month "-" date-year
+
+
+
+
+Crispin Standards Track [Page 84]
+
+RFC 3501 IMAPv4 March 2003
+
+
+date-year = 4DIGIT
+
+date-time = DQUOTE date-day-fixed "-" date-month "-" date-year
+ SP time SP zone DQUOTE
+
+delete = "DELETE" SP mailbox
+ ; Use of INBOX gives a NO error
+
+digit-nz = %x31-39
+ ; 1-9
+
+envelope = "(" env-date SP env-subject SP env-from SP
+ env-sender SP env-reply-to SP env-to SP env-cc SP
+ env-bcc SP env-in-reply-to SP env-message-id ")"
+
+env-bcc = "(" 1*address ")" / nil
+
+env-cc = "(" 1*address ")" / nil
+
+env-date = nstring
+
+env-from = "(" 1*address ")" / nil
+
+env-in-reply-to = nstring
+
+env-message-id = nstring
+
+env-reply-to = "(" 1*address ")" / nil
+
+env-sender = "(" 1*address ")" / nil
+
+env-subject = nstring
+
+env-to = "(" 1*address ")" / nil
+
+examine = "EXAMINE" SP mailbox
+
+fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
+ fetch-att / "(" fetch-att *(SP fetch-att) ")")
+
+fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
+ "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
+ "BODY" ["STRUCTURE"] / "UID" /
+ "BODY" section ["<" number "." nz-number ">"] /
+ "BODY.PEEK" section ["<" number "." nz-number ">"]
+
+
+
+
+
+
+Crispin Standards Track [Page 85]
+
+RFC 3501 IMAPv4 March 2003
+
+
+flag = "\Answered" / "\Flagged" / "\Deleted" /
+ "\Seen" / "\Draft" / flag-keyword / flag-extension
+ ; Does not include "\Recent"
+
+flag-extension = "\" atom
+ ; Future expansion. Client implementations
+ ; MUST accept flag-extension flags. Server
+ ; implementations MUST NOT generate
+ ; flag-extension flags except as defined by
+ ; future standard or standards-track
+ ; revisions of this specification.
+
+flag-fetch = flag / "\Recent"
+
+flag-keyword = atom
+
+flag-list = "(" [flag *(SP flag)] ")"
+
+flag-perm = flag / "\*"
+
+greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF
+
+header-fld-name = astring
+
+header-list = "(" header-fld-name *(SP header-fld-name) ")"
+
+list = "LIST" SP mailbox SP list-mailbox
+
+list-mailbox = 1*list-char / string
+
+list-char = ATOM-CHAR / list-wildcards / resp-specials
+
+list-wildcards = "%" / "*"
+
+literal = "{" number "}" CRLF *CHAR8
+ ; Number represents the number of CHAR8s
+
+login = "LOGIN" SP userid SP password
+
+lsub = "LSUB" SP mailbox SP list-mailbox
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 86]
+
+RFC 3501 IMAPv4 March 2003
+
+
+mailbox = "INBOX" / astring
+ ; INBOX is case-insensitive. All case variants of
+ ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX
+ ; not as an astring. An astring which consists of
+ ; the case-insensitive sequence "I" "N" "B" "O" "X"
+ ; is considered to be INBOX and not an astring.
+ ; Refer to section 5.1 for further
+ ; semantic details of mailbox names.
+
+mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list /
+ "LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
+ "STATUS" SP mailbox SP "(" [status-att-list] ")" /
+ number SP "EXISTS" / number SP "RECENT"
+
+mailbox-list = "(" [mbx-list-flags] ")" SP
+ (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
+
+mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag
+ *(SP mbx-list-oflag) /
+ mbx-list-oflag *(SP mbx-list-oflag)
+
+mbx-list-oflag = "\Noinferiors" / flag-extension
+ ; Other flags; multiple possible per LIST response
+
+mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked"
+ ; Selectability flags; only one per LIST response
+
+media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" /
+ "MESSAGE" / "VIDEO") DQUOTE) / string) SP
+ media-subtype
+ ; Defined in [MIME-IMT]
+
+media-message = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
+ ; Defined in [MIME-IMT]
+
+media-subtype = string
+ ; Defined in [MIME-IMT]
+
+media-text = DQUOTE "TEXT" DQUOTE SP media-subtype
+ ; Defined in [MIME-IMT]
+
+message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))
+
+msg-att = "(" (msg-att-dynamic / msg-att-static)
+ *(SP (msg-att-dynamic / msg-att-static)) ")"
+
+msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
+ ; MAY change for a message
+
+
+
+Crispin Standards Track [Page 87]
+
+RFC 3501 IMAPv4 March 2003
+
+
+msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
+ "RFC822" [".HEADER" / ".TEXT"] SP nstring /
+ "RFC822.SIZE" SP number /
+ "BODY" ["STRUCTURE"] SP body /
+ "BODY" section ["<" number ">"] SP nstring /
+ "UID" SP uniqueid
+ ; MUST NOT change for a message
+
+nil = "NIL"
+
+nstring = string / nil
+
+number = 1*DIGIT
+ ; Unsigned 32-bit integer
+ ; (0 <= n < 4,294,967,296)
+
+nz-number = digit-nz *DIGIT
+ ; Non-zero unsigned 32-bit integer
+ ; (0 < n < 4,294,967,296)
+
+password = astring
+
+quoted = DQUOTE *QUOTED-CHAR DQUOTE
+
+QUOTED-CHAR = <any TEXT-CHAR except quoted-specials> /
+ "\" quoted-specials
+
+quoted-specials = DQUOTE / "\"
+
+rename = "RENAME" SP mailbox SP mailbox
+ ; Use of INBOX as a destination gives a NO error
+
+response = *(continue-req / response-data) response-done
+
+response-data = "*" SP (resp-cond-state / resp-cond-bye /
+ mailbox-data / message-data / capability-data) CRLF
+
+response-done = response-tagged / response-fatal
+
+response-fatal = "*" SP resp-cond-bye CRLF
+ ; Server closes connection immediately
+
+response-tagged = tag SP resp-cond-state CRLF
+
+resp-cond-auth = ("OK" / "PREAUTH") SP resp-text
+ ; Authentication condition
+
+
+
+
+
+Crispin Standards Track [Page 88]
+
+RFC 3501 IMAPv4 March 2003
+
+
+resp-cond-bye = "BYE" SP resp-text
+
+resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
+ ; Status condition
+
+resp-specials = "]"
+
+resp-text = ["[" resp-text-code "]" SP] text
+
+resp-text-code = "ALERT" /
+ "BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
+ capability-data / "PARSE" /
+ "PERMANENTFLAGS" SP "("
+ [flag-perm *(SP flag-perm)] ")" /
+ "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
+ "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
+ "UNSEEN" SP nz-number /
+ atom [SP 1*<any TEXT-CHAR except "]">]
+
+search = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
+ ; CHARSET argument to MUST be registered with IANA
+
+search-key = "ALL" / "ANSWERED" / "BCC" SP astring /
+ "BEFORE" SP date / "BODY" SP astring /
+ "CC" SP astring / "DELETED" / "FLAGGED" /
+ "FROM" SP astring / "KEYWORD" SP flag-keyword /
+ "NEW" / "OLD" / "ON" SP date / "RECENT" / "SEEN" /
+ "SINCE" SP date / "SUBJECT" SP astring /
+ "TEXT" SP astring / "TO" SP astring /
+ "UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
+ "UNKEYWORD" SP flag-keyword / "UNSEEN" /
+ ; Above this line were in [IMAP2]
+ "DRAFT" / "HEADER" SP header-fld-name SP astring /
+ "LARGER" SP number / "NOT" SP search-key /
+ "OR" SP search-key SP search-key /
+ "SENTBEFORE" SP date / "SENTON" SP date /
+ "SENTSINCE" SP date / "SMALLER" SP number /
+ "UID" SP sequence-set / "UNDRAFT" / sequence-set /
+ "(" search-key *(SP search-key) ")"
+
+section = "[" [section-spec] "]"
+
+section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
+ "TEXT"
+ ; top-level or MESSAGE/RFC822 part
+
+section-part = nz-number *("." nz-number)
+ ; body part nesting
+
+
+
+Crispin Standards Track [Page 89]
+
+RFC 3501 IMAPv4 March 2003
+
+
+section-spec = section-msgtext / (section-part ["." section-text])
+
+section-text = section-msgtext / "MIME"
+ ; text other than actual body part (headers, etc.)
+
+select = "SELECT" SP mailbox
+
+seq-number = nz-number / "*"
+ ; message sequence number (COPY, FETCH, STORE
+ ; commands) or unique identifier (UID COPY,
+ ; UID FETCH, UID STORE commands).
+ ; * represents the largest number in use. In
+ ; the case of message sequence numbers, it is
+ ; the number of messages in a non-empty mailbox.
+ ; In the case of unique identifiers, it is the
+ ; unique identifier of the last message in the
+ ; mailbox or, if the mailbox is empty, the
+ ; mailbox's current UIDNEXT value.
+ ; The server should respond with a tagged BAD
+ ; response to a command that uses a message
+ ; sequence number greater than the number of
+ ; messages in the selected mailbox. This
+ ; includes "*" if the selected mailbox is empty.
+
+seq-range = seq-number ":" seq-number
+ ; two seq-number values and all values between
+ ; these two regardless of order.
+ ; Example: 2:4 and 4:2 are equivalent and indicate
+ ; values 2, 3, and 4.
+ ; Example: a unique identifer sequence range of
+ ; 3291:* includes the UID of the last message in
+ ; the mailbox, even if that value is less than 3291.
+
+sequence-set = (seq-number / seq-range) *("," sequence-set)
+ ; set of seq-number values, regardless of order.
+ ; Servers MAY coalesce overlaps and/or execute the
+ ; sequence in any order.
+ ; Example: a message sequence number set of
+ ; 2,4:7,9,12:* for a mailbox with 15 messages is
+ ; equivalent to 2,4,5,6,7,9,12,13,14,15
+ ; Example: a message sequence number set of *:4,5:7
+ ; for a mailbox with 10 messages is equivalent to
+ ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
+ ; overlap coalesced to be 4,5,6,7,8,9,10.
+
+status = "STATUS" SP mailbox SP
+ "(" status-att *(SP status-att) ")"
+
+
+
+
+Crispin Standards Track [Page 90]
+
+RFC 3501 IMAPv4 March 2003
+
+
+status-att = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
+ "UNSEEN"
+
+status-att-list = status-att SP number *(SP status-att SP number)
+
+store = "STORE" SP sequence-set SP store-att-flags
+
+store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
+ (flag-list / (flag *(SP flag)))
+
+string = quoted / literal
+
+subscribe = "SUBSCRIBE" SP mailbox
+
+tag = 1*<any ASTRING-CHAR except "+">
+
+text = 1*TEXT-CHAR
+
+TEXT-CHAR = <any CHAR except CR and LF>
+
+time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
+ ; Hours minutes seconds
+
+uid = "UID" SP (copy / fetch / search / store)
+ ; Unique identifiers used instead of message
+ ; sequence numbers
+
+uniqueid = nz-number
+ ; Strictly ascending
+
+unsubscribe = "UNSUBSCRIBE" SP mailbox
+
+userid = astring
+
+x-command = "X" atom <experimental command arguments>
+
+zone = ("+" / "-") 4DIGIT
+ ; Signed four-digit value of hhmm representing
+ ; hours and minutes east of Greenwich (that is,
+ ; the amount that the given time differs from
+ ; Universal Time). Subtracting the timezone
+ ; from the given time will give the UT form.
+ ; The Universal Time zone is "+0000".
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 91]
+
+RFC 3501 IMAPv4 March 2003
+
+
+10. Author's Note
+
+ This document is a revision or rewrite of earlier documents, and
+ supercedes the protocol specification in those documents: RFC 2060,
+ RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.
+
+11. Security Considerations
+
+ IMAP4rev1 protocol transactions, including electronic mail data, are
+ sent in the clear over the network unless protection from snooping is
+ negotiated. This can be accomplished either by the use of STARTTLS,
+ negotiated privacy protection in the AUTHENTICATE command, or some
+ other protection mechanism.
+
+11.1. STARTTLS Security Considerations
+
+ The specification of the STARTTLS command and LOGINDISABLED
+ capability in this document replaces that in [IMAP-TLS]. [IMAP-TLS]
+ remains normative for the PLAIN [SASL] authenticator.
+
+ IMAP client and server implementations MUST implement the
+ TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite, and SHOULD implement the
+ TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
+ important as it assures that any two compliant implementations can be
+ configured to interoperate. All other cipher suites are OPTIONAL.
+ Note that this is a change from section 2.1 of [IMAP-TLS].
+
+ During the [TLS] negotiation, the client MUST check its understanding
+ of the server hostname against the server's identity as presented in
+ the server Certificate message, in order to prevent man-in-the-middle
+ attacks. If the match fails, the client SHOULD either ask for
+ explicit user confirmation, or terminate the connection and indicate
+ that the server's identity is suspect. Matching is performed
+ according to these rules:
+
+ The client MUST use the server hostname it used to open the
+ connection as the value to compare against the server name
+ as expressed in the server certificate. The client MUST
+ NOT use any form of the server hostname derived from an
+ insecure remote source (e.g., insecure DNS lookup). CNAME
+ canonicalization is not done.
+
+ If a subjectAltName extension of type dNSName is present in
+ the certificate, it SHOULD be used as the source of the
+ server's identity.
+
+ Matching is case-insensitive.
+
+
+
+
+Crispin Standards Track [Page 92]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ A "*" wildcard character MAY be used as the left-most name
+ component in the certificate. For example, *.example.com
+ would match a.example.com, foo.example.com, etc. but would
+ not match example.com.
+
+ If the certificate contains multiple names (e.g., more than
+ one dNSName field), then a match with any one of the fields
+ is considered acceptable.
+
+ Both the client and server MUST check the result of the STARTTLS
+ command and subsequent [TLS] negotiation to see whether acceptable
+ authentication or privacy was achieved.
+
+11.2. Other Security Considerations
+
+ A server error message for an AUTHENTICATE command which fails due to
+ invalid credentials SHOULD NOT detail why the credentials are
+ invalid.
+
+ Use of the LOGIN command sends passwords in the clear. This can be
+ avoided by using the AUTHENTICATE command with a [SASL] mechanism
+ that does not use plaintext passwords, by first negotiating
+ encryption via STARTTLS or some other protection mechanism.
+
+ A server implementation MUST implement a configuration that, at the
+ time of authentication, requires:
+ (1) The STARTTLS command has been negotiated.
+ OR
+ (2) Some other mechanism that protects the session from password
+ snooping has been provided.
+ OR
+ (3) The following measures are in place:
+ (a) The LOGINDISABLED capability is advertised, and [SASL]
+ mechanisms (such as PLAIN) using plaintext passwords are NOT
+ advertised in the CAPABILITY list.
+ AND
+ (b) The LOGIN command returns an error even if the password is
+ correct.
+ AND
+ (c) The AUTHENTICATE command returns an error with all [SASL]
+ mechanisms that use plaintext passwords, even if the password
+ is correct.
+
+ A server error message for a failing LOGIN command SHOULD NOT specify
+ that the user name, as opposed to the password, is invalid.
+
+ A server SHOULD have mechanisms in place to limit or delay failed
+ AUTHENTICATE/LOGIN attempts.
+
+
+
+Crispin Standards Track [Page 93]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ Additional security considerations are discussed in the section
+ discussing the AUTHENTICATE and LOGIN commands.
+
+12. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ As this specification revises the STARTTLS and LOGINDISABLED
+ extensions previously defined in [IMAP-TLS], the registry will be
+ updated accordingly.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 94]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Appendices
+
+A. Normative References
+
+ The following documents contain definitions or specifications that
+ are necessary to understand this document properly:
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234,
+ November 1997.
+
+ [ANONYMOUS] Newman, C., "Anonymous SASL Mechanism", RFC
+ 2245, November 1997.
+
+ [CHARSET] Freed, N. and J. Postel, "IANA Character Set
+ Registration Procedures", RFC 2978, October
+ 2000.
+
+ [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest
+ Authentication as a SASL Mechanism", RFC 2831,
+ May 2000.
+
+ [DISPOSITION] Troost, R., Dorner, S. and K. Moore,
+ "Communicating Presentation Information in
+ Internet Messages: The Content-Disposition
+ Header", RFC 2183, August 1997.
+
+ [IMAP-TLS] Newman, C., "Using TLS with IMAP, POP3 and
+ ACAP", RFC 2595, June 1999.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to
+ Indicate Requirement Levels", BCP 14, RFC 2119,
+ March 1997.
+
+ [LANGUAGE-TAGS] Alvestrand, H., "Tags for the Identification of
+ Languages", BCP 47, RFC 3066, January 2001.
+
+ [LOCATION] Palme, J., Hopmann, A. and N. Shelness, "MIME
+ Encapsulation of Aggregate Documents, such as
+ HTML (MHTML)", RFC 2557, March 1999.
+
+ [MD5] Myers, J. and M. Rose, "The Content-MD5 Header
+ Field", RFC 1864, October 1995.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 95]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ [MIME-HDRS] Moore, K., "MIME (Multipurpose Internet Mail
+ Extensions) Part Three: Message Header
+ Extensions for Non-ASCII Text", RFC 2047,
+ November 1996.
+
+ [MIME-IMB] Freed, N. and N. Borenstein, "MIME
+ (Multipurpose Internet Mail Extensions) Part
+ One: Format of Internet Message Bodies", RFC
+ 2045, November 1996.
+
+ [MIME-IMT] Freed, N. and N. Borenstein, "MIME
+ (Multipurpose Internet Mail Extensions) Part
+ Two: Media Types", RFC 2046, November 1996.
+
+ [RFC-2822] Resnick, P., "Internet Message Format", RFC
+ 2822, April 2001.
+
+ [SASL] Myers, J., "Simple Authentication and Security
+ Layer (SASL)", RFC 2222, October 1997.
+
+ [TLS] Dierks, T. and C. Allen, "The TLS Protocol
+ Version 1.0", RFC 2246, January 1999.
+
+ [UTF-7] Goldsmith, D. and M. Davis, "UTF-7: A Mail-Safe
+ Transformation Format of Unicode", RFC 2152,
+ May 1997.
+
+ The following documents describe quality-of-implementation issues
+ that should be carefully considered when implementing this protocol:
+
+ [IMAP-IMPLEMENTATION] Leiba, B., "IMAP Implementation
+ Recommendations", RFC 2683, September 1999.
+
+ [IMAP-MULTIACCESS] Gahrns, M., "IMAP4 Multi-Accessed Mailbox
+ Practice", RFC 2180, July 1997.
+
+A.1 Informative References
+
+ The following documents describe related protocols:
+
+ [IMAP-DISC] Austein, R., "Synchronization Operations for
+ Disconnected IMAP4 Clients", Work in Progress.
+
+ [IMAP-MODEL] Crispin, M., "Distributed Electronic Mail
+ Models in IMAP4", RFC 1733, December 1994.
+
+
+
+
+
+
+Crispin Standards Track [Page 96]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244,
+ November 1997.
+
+ [SMTP] Klensin, J., "Simple Mail Transfer Protocol",
+ STD 10, RFC 2821, April 2001.
+
+ The following documents are historical or describe historical aspects
+ of this protocol:
+
+ [IMAP-COMPAT] Crispin, M., "IMAP4 Compatibility with
+ IMAP2bis", RFC 2061, December 1996.
+
+ [IMAP-HISTORICAL] Crispin, M., "IMAP4 Compatibility with IMAP2
+ and IMAP2bis", RFC 1732, December 1994.
+
+ [IMAP-OBSOLETE] Crispin, M., "Internet Message Access Protocol
+ - Obsolete Syntax", RFC 2062, December 1996.
+
+ [IMAP2] Crispin, M., "Interactive Mail Access Protocol
+ - Version 2", RFC 1176, August 1990.
+
+ [RFC-822] Crocker, D., "Standard for the Format of ARPA
+ Internet Text Messages", STD 11, RFC 822,
+ August 1982.
+
+ [RFC-821] Postel, J., "Simple Mail Transfer Protocol",
+ STD 10, RFC 821, August 1982.
+
+B. Changes from RFC 2060
+
+ 1) Clarify description of unique identifiers and their semantics.
+
+ 2) Fix the SELECT description to clarify that UIDVALIDITY is required
+ in the SELECT and EXAMINE responses.
+
+ 3) Added an example of a failing search.
+
+ 4) Correct store-att-flags: "#flag" should be "1#flag".
+
+ 5) Made search and section rules clearer.
+
+ 6) Correct the STORE example.
+
+ 7) Correct "BASE645" misspelling.
+
+ 8) Remove extraneous close parenthesis in example of two-part message
+ with text and BASE64 attachment.
+
+
+
+Crispin Standards Track [Page 97]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 9) Remove obsolete "MAILBOX" response from mailbox-data.
+
+ 10) A spurious "<" in the rule for mailbox-data was removed.
+
+ 11) Add CRLF to continue-req.
+
+ 12) Specifically exclude "]" from the atom in resp-text-code.
+
+ 13) Clarify that clients and servers should adhere strictly to the
+ protocol syntax.
+
+ 14) Emphasize in 5.2 that EXISTS can not be used to shrink a mailbox.
+
+ 15) Add NEWNAME to resp-text-code.
+
+ 16) Clarify that the empty string, not NIL, is used as arguments to
+ LIST.
+
+ 17) Clarify that NIL can be returned as a hierarchy delimiter for the
+ empty string mailbox name argument if the mailbox namespace is flat.
+
+ 18) Clarify that addr-mailbox and addr-name have RFC-2822 quoting
+ removed.
+
+ 19) Update UTF-7 reference.
+
+ 20) Fix example in 6.3.11.
+
+ 21) Clarify that non-existent UIDs are ignored.
+
+ 22) Update DISPOSITION reference.
+
+ 23) Expand state diagram.
+
+ 24) Clarify that partial fetch responses are only returned in
+ response to a partial fetch command.
+
+ 25) Add UIDNEXT response code. Correct UIDVALIDITY definition
+ reference.
+
+ 26) Further clarification of "can" vs. "MAY".
+
+ 27) Reference RFC-2119.
+
+ 28) Clarify that superfluous shifts are not permitted in modified
+ UTF-7.
+
+ 29) Clarify that there are no implicit shifts in modified UTF-7.
+
+
+
+Crispin Standards Track [Page 98]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 30) Clarify that "INBOX" in a mailbox name is always INBOX, even if
+ it is given as a string.
+
+ 31) Add missing open parenthesis in media-basic grammar rule.
+
+ 32) Correct attribute syntax in mailbox-data.
+
+ 33) Add UIDNEXT to EXAMINE responses.
+
+ 34) Clarify UNSEEN, PERMANENTFLAGS, UIDVALIDITY, and UIDNEXT
+ responses in SELECT and EXAMINE. They are required now, but weren't
+ in older versions.
+
+ 35) Update references with RFC numbers.
+
+ 36) Flush text-mime2.
+
+ 37) Clarify that modified UTF-7 names must be case-sensitive and that
+ violating the convention should be avoided.
+
+ 38) Correct UID FETCH example.
+
+ 39) Clarify UID FETCH, UID STORE, and UID SEARCH vs. untagged EXPUNGE
+ responses.
+
+ 40) Clarify the use of the word "convention".
+
+ 41) Clarify that a command is not "in progress" until it has been
+ fully received (specifically, that a command is not "in progress"
+ during command continuation negotiation).
+
+ 42) Clarify envelope defaulting.
+
+ 43) Clarify that SP means one and only one space character.
+
+ 44) Forbid silly states in LIST response.
+
+ 45) Clarify that the ENVELOPE, INTERNALDATE, RFC822*, BODY*, and UID
+ for a message is static.
+
+ 46) Add BADCHARSET response code.
+
+ 47) Update formal syntax to [ABNF] conventions.
+
+ 48) Clarify trailing hierarchy delimiter in CREATE semantics.
+
+ 49) Clarify that the "blank line" is the [RFC-2822] delimiting blank
+ line.
+
+
+
+Crispin Standards Track [Page 99]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 50) Clarify that RENAME should also create hierarchy as needed for
+ the command to complete.
+
+ 51) Fix body-ext-mpart to not require language if disposition
+ present.
+
+ 52) Clarify the RFC822.HEADER response.
+
+ 53) Correct missing space after charset astring in search.
+
+ 54) Correct missing quote for BADCHARSET in resp-text-code.
+
+ 55) Clarify that ALL, FAST, and FULL preclude any other data items
+ appearing.
+
+ 56) Clarify semantics of reference argument in LIST.
+
+ 57) Clarify that a null string for SEARCH HEADER X-FOO means any
+ message with a header line with a field-name of X-FOO regardless of
+ the text of the header.
+
+ 58) Specifically reserve 8-bit mailbox names for future use as UTF-8.
+
+ 59) It is not an error for the client to store a flag that is not in
+ the PERMANENTFLAGS list; however, the server will either ignore the
+ change or make the change in the session only.
+
+ 60) Correct/clarify the text regarding superfluous shifts.
+
+ 61) Correct typographic errors in the "Changes" section.
+
+ 62) Clarify that STATUS must not be used to check for new messages in
+ the selected mailbox
+
+ 63) Clarify LSUB behavior with "%" wildcard.
+
+ 64) Change AUTHORIZATION to AUTHENTICATE in section 7.5.
+
+ 65) Clarify description of multipart body type.
+
+ 66) Clarify that STORE FLAGS does not affect \Recent.
+
+ 67) Change "west" to "east" in description of timezone.
+
+ 68) Clarify that commands which break command pipelining must wait
+ for a completion result response.
+
+ 69) Clarify that EXAMINE does not affect \Recent.
+
+
+
+Crispin Standards Track [Page 100]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 70) Make description of MIME structure consistent.
+
+ 71) Clarify that date searches disregard the time and timezone of the
+ INTERNALDATE or Date: header. In other words, "ON 13-APR-2000" means
+ messages with an INTERNALDATE text which starts with "13-APR-2000",
+ even if timezone differential from the local timezone is sufficient
+ to move that INTERNALDATE into the previous or next day.
+
+ 72) Clarify that the header fetches don't add a blank line if one
+ isn't in the [RFC-2822] message.
+
+ 73) Clarify (in discussion of UIDs) that messages are immutable.
+
+ 74) Add an example of CHARSET searching.
+
+ 75) Clarify in SEARCH that keywords are a type of flag.
+
+ 76) Clarify the mandatory nature of the SELECT data responses.
+
+ 77) Add optional CAPABILITY response code in the initial OK or
+ PREAUTH.
+
+ 78) Add note that server can send an untagged CAPABILITY command as
+ part of the responses to AUTHENTICATE and LOGIN.
+
+ 79) Remove statement about it being unnecessary to issue a CAPABILITY
+ command more than once in a connection. That statement is no longer
+ true.
+
+ 80) Clarify that untagged EXPUNGE decrements the number of messages
+ in the mailbox.
+
+ 81) Fix definition of "body" (concatenation has tighter binding than
+ alternation).
+
+ 82) Add a new "Special Notes to Implementors" section with reference
+ to [IMAP-IMPLEMENTATION].
+
+ 83) Clarify that an untagged CAPABILITY response to an AUTHENTICATE
+ command should only be done if a security layer was not negotiated.
+
+ 84) Change the definition of atom to exclude "]". Update astring to
+ include "]" for compatiblity with the past. Remove resp-text-atom.
+
+ 85) Remove NEWNAME. It can't work because mailbox names can be
+ literals and can include "]". Functionality can be addressed via
+ referrals.
+
+
+
+
+Crispin Standards Track [Page 101]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 86) Move modified UTF-7 rationale in order to have more logical
+ paragraph flow.
+
+ 87) Clarify UID uniqueness guarantees with the use of MUST.
+
+ 88) Note that clients should read response data until the connection
+ is closed instead of immediately closing on a BYE.
+
+ 89) Change RFC-822 references to RFC-2822.
+
+ 90) Clarify that RFC-2822 should be followed instead of RFC-822.
+
+ 91) Change recommendation of optional automatic capabilities in LOGIN
+ and AUTHENTICATE to use the CAPABILITY response code in the tagged
+ OK. This is more interoperable than an unsolicited untagged
+ CAPABILITY response.
+
+ 92) STARTTLS and AUTH=PLAIN are mandatory to implement; add
+ recommendations for other [SASL] mechanisms.
+
+ 93) Clarify that a "connection" (as opposed to "server" or "command")
+ is in one of the four states.
+
+ 94) Clarify that a failed or rejected command does not change state.
+
+ 95) Split references between normative and informative.
+
+ 96) Discuss authentication failure issues in security section.
+
+ 97) Clarify that a data item is not necessarily of only one data
+ type.
+
+ 98) Clarify that sequence ranges are independent of order.
+
+ 99) Change an example to clarify that superfluous shifts in
+ Modified-UTF7 can not be fixed just by omitting the shift. The
+ entire string must be recalculated.
+
+ 100) Change Envelope Structure definition since [RFC-2822] uses
+ "envelope" to refer to the [SMTP] envelope and not the envelope data
+ that appears in the [RFC-2822] header.
+
+ 101) Expand on RFC822.HEADER response data vs. BODY[HEADER].
+
+ 102) Clarify Logout state semantics, change ASCII art.
+
+ 103) Security changes to comply with IESG requirements.
+
+
+
+
+Crispin Standards Track [Page 102]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ 104) Add definition for body URI.
+
+ 105) Break sequence range definition into three rules, with rewritten
+ descriptions for each.
+
+ 106) Move STARTTLS and LOGINDISABLED here from [IMAP-TLS].
+
+ 107) Add IANA Considerations section.
+
+ 108) Clarify valid client assumptions for new message UIDs vs.
+ UIDNEXT.
+
+ 109) Clarify that changes to permanentflags affect concurrent
+ sessions as well as subsequent sessions.
+
+ 110) Clarify that authenticated state can be entered by the CLOSE
+ command.
+
+ 111) Emphasize that SELECT and EXAMINE are the exceptions to the rule
+ that a failing command does not change state.
+
+ 112) Clarify that newly-appended messages have the Recent flag set.
+
+ 113) Clarify that newly-copied messages SHOULD have the Recent flag
+ set.
+
+ 114) Clarify that UID commands always return the UID in FETCH
+ responses.
+
+C. Key Word Index
+
+ +FLAGS <flag list> (store command data item) ............... 59
+ +FLAGS.SILENT <flag list> (store command data item) ........ 59
+ -FLAGS <flag list> (store command data item) ............... 59
+ -FLAGS.SILENT <flag list> (store command data item) ........ 59
+ ALERT (response code) ...................................... 64
+ ALL (fetch item) ........................................... 55
+ ALL (search key) ........................................... 50
+ ANSWERED (search key) ...................................... 50
+ APPEND (command) ........................................... 45
+ AUTHENTICATE (command) ..................................... 27
+ BAD (response) ............................................. 66
+ BADCHARSET (response code) ................................. 64
+ BCC <string> (search key) .................................. 51
+ BEFORE <date> (search key) ................................. 51
+ BODY (fetch item) .......................................... 55
+ BODY (fetch result) ........................................ 73
+ BODY <string> (search key) ................................. 51
+
+
+
+Crispin Standards Track [Page 103]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ BODY.PEEK[<section>]<<partial>> (fetch item) ............... 57
+ BODYSTRUCTURE (fetch item) ................................. 57
+ BODYSTRUCTURE (fetch result) ............................... 74
+ BODY[<section>]<<origin octet>> (fetch result) ............. 74
+ BODY[<section>]<<partial>> (fetch item) .................... 55
+ BYE (response) ............................................. 67
+ Body Structure (message attribute) ......................... 12
+ CAPABILITY (command) ....................................... 24
+ CAPABILITY (response code) ................................. 64
+ CAPABILITY (response) ...................................... 68
+ CC <string> (search key) ................................... 51
+ CHECK (command) ............................................ 47
+ CLOSE (command) ............................................ 48
+ COPY (command) ............................................. 59
+ CREATE (command) ........................................... 34
+ DELETE (command) ........................................... 35
+ DELETED (search key) ....................................... 51
+ DRAFT (search key) ......................................... 51
+ ENVELOPE (fetch item) ...................................... 57
+ ENVELOPE (fetch result) .................................... 77
+ EXAMINE (command) .......................................... 33
+ EXISTS (response) .......................................... 71
+ EXPUNGE (command) .......................................... 48
+ EXPUNGE (response) ......................................... 72
+ Envelope Structure (message attribute) ..................... 12
+ FAST (fetch item) .......................................... 55
+ FETCH (command) ............................................ 54
+ FETCH (response) ........................................... 73
+ FLAGGED (search key) ....................................... 51
+ FLAGS (fetch item) ......................................... 57
+ FLAGS (fetch result) ....................................... 78
+ FLAGS (response) ........................................... 71
+ FLAGS <flag list> (store command data item) ................ 59
+ FLAGS.SILENT <flag list> (store command data item) ......... 59
+ FROM <string> (search key) ................................. 51
+ FULL (fetch item) .......................................... 55
+ Flags (message attribute) .................................. 11
+ HEADER (part specifier) .................................... 55
+ HEADER <field-name> <string> (search key) .................. 51
+ HEADER.FIELDS <header-list> (part specifier) ............... 55
+ HEADER.FIELDS.NOT <header-list> (part specifier) ........... 55
+ INTERNALDATE (fetch item) .................................. 57
+ INTERNALDATE (fetch result) ................................ 78
+ Internal Date (message attribute) .......................... 12
+ KEYWORD <flag> (search key) ................................ 51
+ Keyword (type of flag) ..................................... 11
+ LARGER <n> (search key) .................................... 51
+ LIST (command) ............................................. 40
+
+
+
+Crispin Standards Track [Page 104]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ LIST (response) ............................................ 69
+ LOGIN (command) ............................................ 30
+ LOGOUT (command) ........................................... 25
+ LSUB (command) ............................................. 43
+ LSUB (response) ............................................ 70
+ MAY (specification requirement term) ....................... 4
+ MESSAGES (status item) ..................................... 45
+ MIME (part specifier) ...................................... 56
+ MUST (specification requirement term) ...................... 4
+ MUST NOT (specification requirement term) .................. 4
+ Message Sequence Number (message attribute) ................ 10
+ NEW (search key) ........................................... 51
+ NO (response) .............................................. 66
+ NOOP (command) ............................................. 25
+ NOT <search-key> (search key) .............................. 52
+ OK (response) .............................................. 65
+ OLD (search key) ........................................... 52
+ ON <date> (search key) ..................................... 52
+ OPTIONAL (specification requirement term) .................. 4
+ OR <search-key1> <search-key2> (search key) ................ 52
+ PARSE (response code) ...................................... 64
+ PERMANENTFLAGS (response code) ............................. 64
+ PREAUTH (response) ......................................... 67
+ Permanent Flag (class of flag) ............................. 12
+ READ-ONLY (response code) .................................. 65
+ READ-WRITE (response code) ................................. 65
+ RECENT (response) .......................................... 72
+ RECENT (search key) ........................................ 52
+ RECENT (status item) ....................................... 45
+ RENAME (command) ........................................... 37
+ REQUIRED (specification requirement term) .................. 4
+ RFC822 (fetch item) ........................................ 57
+ RFC822 (fetch result) ...................................... 78
+ RFC822.HEADER (fetch item) ................................. 57
+ RFC822.HEADER (fetch result) ............................... 78
+ RFC822.SIZE (fetch item) ................................... 57
+ RFC822.SIZE (fetch result) ................................. 78
+ RFC822.TEXT (fetch item) ................................... 58
+ RFC822.TEXT (fetch result) ................................. 79
+ SEARCH (command) ........................................... 49
+ SEARCH (response) .......................................... 71
+ SEEN (search key) .......................................... 52
+ SELECT (command) ........................................... 31
+ SENTBEFORE <date> (search key) ............................. 52
+ SENTON <date> (search key) ................................. 52
+ SENTSINCE <date> (search key) .............................. 52
+ SHOULD (specification requirement term) .................... 4
+ SHOULD NOT (specification requirement term) ................ 4
+
+
+
+Crispin Standards Track [Page 105]
+
+RFC 3501 IMAPv4 March 2003
+
+
+ SINCE <date> (search key) .................................. 52
+ SMALLER <n> (search key) ................................... 52
+ STARTTLS (command) ......................................... 27
+ STATUS (command) ........................................... 44
+ STATUS (response) .......................................... 70
+ STORE (command) ............................................ 58
+ SUBJECT <string> (search key) .............................. 53
+ SUBSCRIBE (command) ........................................ 38
+ Session Flag (class of flag) ............................... 12
+ System Flag (type of flag) ................................. 11
+ TEXT (part specifier) ...................................... 56
+ TEXT <string> (search key) ................................. 53
+ TO <string> (search key) ................................... 53
+ TRYCREATE (response code) .................................. 65
+ UID (command) .............................................. 60
+ UID (fetch item) ........................................... 58
+ UID (fetch result) ......................................... 79
+ UID <sequence set> (search key) ............................ 53
+ UIDNEXT (response code) .................................... 65
+ UIDNEXT (status item) ...................................... 45
+ UIDVALIDITY (response code) ................................ 65
+ UIDVALIDITY (status item) .................................. 45
+ UNANSWERED (search key) .................................... 53
+ UNDELETED (search key) ..................................... 53
+ UNDRAFT (search key) ....................................... 53
+ UNFLAGGED (search key) ..................................... 53
+ UNKEYWORD <flag> (search key) .............................. 53
+ UNSEEN (response code) ..................................... 65
+ UNSEEN (search key) ........................................ 53
+ UNSEEN (status item) ....................................... 45
+ UNSUBSCRIBE (command) ...................................... 39
+ Unique Identifier (UID) (message attribute) ................ 8
+ X<atom> (command) .......................................... 62
+ [RFC-2822] Size (message attribute) ........................ 12
+ \Answered (system flag) .................................... 11
+ \Deleted (system flag) ..................................... 11
+ \Draft (system flag) ....................................... 11
+ \Flagged (system flag) ..................................... 11
+ \Marked (mailbox name attribute) ........................... 69
+ \Noinferiors (mailbox name attribute) ...................... 69
+ \Noselect (mailbox name attribute) ......................... 69
+ \Recent (system flag) ...................................... 11
+ \Seen (system flag) ........................................ 11
+ \Unmarked (mailbox name attribute) ......................... 69
+
+
+
+
+
+
+
+Crispin Standards Track [Page 106]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 107]
+
+RFC 3501 IMAPv4 March 2003
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns. v This
+ document and the information contained herein is provided on an "AS
+ IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
+ FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+ LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
+ NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
+ OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 108]
+
+
diff --git a/imap/docs/rfc/rfc3502.txt b/imap/docs/rfc/rfc3502.txt
new file mode 100644
index 00000000..f6b61a44
--- /dev/null
+++ b/imap/docs/rfc/rfc3502.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 3502 University of Washington
+Category: Standards Track March 2003
+
+
+ Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ This document describes the multiappending extension to the Internet
+ Message Access Protocol (IMAP) (RFC 3501). This extension provides
+ substantial performance improvements for IMAP clients which upload
+ multiple messages at a time to a mailbox on the server.
+
+ A server which supports this extension indicates this with a
+ capability name of "MULTIAPPEND".
+
+Terminology
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+ be interpreted as described in [KEYWORDS].
+
+Introduction
+
+ The MULTIAPPEND extension permits uploading of multiple messages with
+ a single command. When used in conjunction with the [LITERAL+]
+ extension, the entire upload is accomplished in a single
+ command/response round trip.
+
+ A MULTIAPPEND APPEND operation is atomic; either all messages are
+ successfully appended, or no messages are appended.
+
+ In the base IMAP specification, each message must be appended in a
+ separate command, and there is no mechanism to "unappend" messages if
+ an error occurs while appending. Also, some mail stores may require
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+ an expensive "open/lock + sync/unlock/close" operation as part of
+ appending; this can be quite expensive if it must be done on a
+ per-message basis.
+
+ If the server supports both LITERAL+ and pipelining but not
+ MULTIAPPEND, it may be possible to get some of the performance
+ advantages of MULTIAPPEND by doing a pipelined "batch" append.
+ However, it will not work as well as MULTIAPPEND for the following
+ reasons:
+
+ 1) Multiple APPEND commands, even as part of a pipelined batch,
+ are non-atomic by definition. There is no way to revert the
+ mailbox to the state before the batch append in the event of an
+ error.
+
+ 2) It may not be feasible for the server to coalesce pipelined
+ APPEND operations so as to avoid the "open/lock +
+ sync/unlock/close" overhead described above. In any case, such
+ coalescing would be timing dependent and thus potentially
+ unreliable. In particular, with traditional UNIX mailbox files,
+ it is assumed that a lock is held only for a single atomic
+ operation, and many applications disregard any lock that is
+ older than 5 minutes.
+
+ 3) If an error occurs, depending upon the nature of the error,
+ it is possible for additional messages to be appended after the
+ error. For example, the user wants to append 5 messages, but a
+ disk quota error occurs with the third message because of its
+ size. However, the fourth and fifth messages have already been
+ sent in the pipeline, so the mailbox ends up with the first,
+ second, fourth, and fifth messages of the batch appended.
+
+6.3.11. APPEND Command
+
+ Arguments: mailbox name
+ one or more messages to upload, specified as:
+ OPTIONAL flag parenthesized list
+ OPTIONAL date/time string
+ message literal
+
+ Data: no specific responses for this command
+
+ Result: OK - append completed
+ NO - append error: can't append to that mailbox, error
+ in flags or date/time or message text,
+ append cancelled
+ BAD - command unknown or arguments invalid
+
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+ The APPEND command appends the literal arguments as new messages
+ to the end of the specified destination mailbox. This argument
+ SHOULD be in the format of an [RFC-2822] message. 8-bit
+ characters are permitted in the message. A server implementation
+ that is unable to preserve 8-bit data properly MUST be able to
+ reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
+ content transfer encoding.
+
+ Note: There MAY be exceptions, e.g., draft messages, in
+ which required [RFC-2822] header lines are omitted in the
+ message literal argument to APPEND. The full implications
+ of doing so MUST be understood and carefully weighed.
+
+ If a flag parenthesized list is specified, the flags SHOULD be set
+ in the resulting message; otherwise, the flag list of the
+ resulting message is set empty by default.
+
+ If a date-time is specified, the internal date SHOULD be set in
+ the resulting message; otherwise, the internal date of the
+ resulting message is set to the current date and time by default.
+
+ A zero-length message literal argument is an error, and MUST
+ return a NO. This can be used to cancel the append.
+
+ If the append is unsuccessful for any reason (including being
+ cancelled), the mailbox MUST be restored to its state before the
+ APPEND attempt; no partial appending is permitted. The server MAY
+ return an error before processing all the message arguments.
+
+ If the destination mailbox does not exist, a server MUST return an
+ error, and MUST NOT automatically create the mailbox. Unless it
+ is certain that the destination mailbox can not be created, the
+ server MUST send the response code "[TRYCREATE]" as the prefix of
+ the text of the tagged NO response. This gives a hint to the
+ client that it can attempt a CREATE command and retry the APPEND
+ if the CREATE is successful.
+
+ If the mailbox is currently selected, the normal new message
+ actions SHOULD occur. Specifically, the server SHOULD notify the
+ client immediately via an untagged EXISTS response. If the server
+ does not do so, the client MAY issue a NOOP command (or failing
+ that, a CHECK command) after one or more APPEND commands.
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+ Example: C: A003 APPEND saved-messages (\Seen) {329}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@Blurdybloop.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.example.net
+ C: Message-Id: <B27397-0100000@Blurdybloop.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C: (\Seen) " 7-Feb-1994 22:43:04 -0800" {295}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+ C: From: Joe Mooch <mooch@OWaTaGu.example.net>
+ C: Subject: Re: afternoon meeting
+ C: To: foobar@blurdybloop.example.com
+ C: Message-Id: <a0434793874930@OWaTaGu.example.net>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: 3:30 is fine with me.
+ C:
+ S: A003 OK APPEND completed
+ C: A004 APPEND bogusname (\Flagged) {1023}
+ S: A004 NO [TRYCREATE] No such mailbox as bogusname
+ C: A005 APPEND test (\Flagged) {99}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 2000 22:43:04 -0800 (PST)
+ C: From: Fred Foobar <fred@example.com>
+ C: Subject: hmm...
+ C: {35403}
+ S: A005 NO APPEND failed: Disk quota exceeded
+
+ Note: The APPEND command is not used for message delivery,
+ because it does not provide a mechanism to transfer [SMTP]
+ envelope information.
+
+Modification to IMAP4rev1 Base Protocol Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ append = "APPEND" SP mailbox 1*append-message
+
+ append-message = [SP flag-list] [SP date-time] SP literal
+
+
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+MULTIAPPEND Interaction with UIDPLUS Extension
+
+ Servers which support both MULTIAPPEND and [UIDPLUS] will have the
+ "resp-code-apnd" rule modified as follows:
+
+ resp-code-apnd = "APPENDUID" SP nz-number SP set
+
+ That is, the APPENDUID response code returns as many UIDs as there
+ were messages appended in the multiple append. The UIDs returned
+ should be in the order the articles where appended. The message set
+ may not contain extraneous UIDs or the symbol "*".
+
+Security Considerations
+
+ The MULTIAPPEND extension does not raise any security considerations
+ that are not present in the base [IMAP] protocol, and these issues
+ are discussed in [IMAP]. Nevertheless, it is important to remember
+ that IMAP4rev1 protocol transactions, including electronic mail data,
+ are sent in the clear over the network unless protection from
+ snooping is negotiated, either by the use of STARTTLS, privacy
+ protection is negotiated in the AUTHENTICATE command, or some other
+ protection mechanism is in effect.
+
+Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [MIME-IMB] Freed, N. and N. Borenstein, "MIME (Multipurpose Internet
+ Mail Extensions) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [RFC-2822] Resnick, P., "Internet Message Format", RFC 2822, April
+ 2001.
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+Informative References
+
+ [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
+ January 1997.
+
+ [UIDPLUS] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1988.
+
+ [SMTP] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC
+ 2821, April 2001.
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 3502 IMAP MULTIAPPEND March 2003
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 7]
+
diff --git a/imap/docs/rfc/rfc3503.txt b/imap/docs/rfc/rfc3503.txt
new file mode 100644
index 00000000..5b82fb08
--- /dev/null
+++ b/imap/docs/rfc/rfc3503.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 3503 ACI Worldwide/MessagingDirect
+Category: Standards Track March 2003
+
+
+ Message Disposition Notification (MDN) profile for
+ Internet Message Access Protocol (IMAP)
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ The Message Disposition Notification (MDN) facility defined in RFC
+ 2298 provides a means by which a message can request that message
+ processing by the recipient be acknowledged as well as a format to be
+ used for such acknowledgements. However, it doesn't describe how
+ multiple Mail User Agents (MUAs) should handle the generation of MDNs
+ in an Internet Message Access Protocol (IMAP4) environment.
+
+ This document describes how to handle MDNs in such an environment and
+ provides guidelines for implementers of IMAP4 that want to add MDN
+ support to their products.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 1]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+Table of Contents
+
+ 1. Conventions Used in this Document............................. 2
+ 2. Introduction and Overview..................................... 2
+ 3. Client behavior............................................... 3
+ 3.1. Client behavior when receiving a message................. 5
+ 3.2. Client behavior when copying a message................... 5
+ 3.3. Client behavior when sending a message................... 5
+ 3.4. Client behavior when saving a temporary message.......... 5
+ 4. Server behavior............................................... 5
+ 4.1. Server that supports arbitrary keywords.................. 5
+ 4.2. Server that supports only $MDNSent keyword............... 5
+ 4.3. Interaction with IMAP ACL extension...................... 6
+ 5. Examples...................................................... 6
+ 6. Security Considerations....................................... 7
+ 7. Formal Syntax................................................. 7
+ 8. Acknowledgments............................................... 7
+ 9. Normative References.......................................... 8
+ 10. Author's Address.............................................. 8
+ 11. Full Copyright Statement...................................... 9
+
+1. Conventions Used in this Document
+
+ "C:" and "S:" in examples show lines sent by the client and server
+ respectively.
+
+ The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
+ this document when typed in uppercase are to be interpreted as
+ defined in "Key words for use in RFCs to Indicate Requirement Levels"
+ [KEYWORDS].
+
+2. Introduction and Overview
+
+ This memo defines an additional [IMAP4] mailbox keyword that allows
+ multiple Mail User Agents (MUAs) to know if a requested receipt
+ notification was sent.
+
+ Message Disposition Notification [MDN] does not require any special
+ support of IMAP in the case where a user has access to the mailstore
+ from only one computer and is using a single MUA. In this case, the
+ MUA behaves as described in [MDN], i.e., the MUA performs automatic
+ processing and generates corresponding MDNs, it performs requested
+ action and, with the user's permission, sends appropriate MDNs. The
+ MUA will not send MDN twice because the MUA keeps track of sent
+ notifications in a local configuration. However, that does not work
+ when IMAP is used to access the same mailstore from different
+ locations or is using different MUAs.
+
+
+
+
+Melnikov Standards Track [Page 2]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+ This document defines a new special purpose mailbox keyword $MDNSent
+ that must be used by MUAs. It does not define any new command or
+ response for IMAP, but describes a technique that MUAs should use to
+ achieve interoperability.
+
+ When a client opens a mailbox for the first time, it verifies that
+ the server is capable of storing the $MDNSent keyword by examining
+ the PERMANENTFLAGS response code. In order to support MDN in IMAP, a
+ server MUST support either the $MDNSent keyword, or arbitrary message
+ keywords.
+
+3. Client behavior
+
+ The use of IMAP requires few additional steps in mail processing on
+ the client side. The following timeline modifies the timeline found
+ in Section 4 of [MDN].
+
+ -- User composes message.
+
+ -- User tells MUA to send message.
+
+ -- MUA passes message to MSA (original recipient information passed
+ along). MUA [optionally] saves message to a folder for sent mail
+ with $MDNSent flag set.
+
+ -- MSA sends message to MTA.
+
+ -- Final MTA receives message.
+
+ -- Final MTA delivers message to MUA (possibly generating DSN).
+
+ -- MUA logs into IMAP server, opens mailbox, verifies if mailbox can
+ store $MDNSent keyword by examining PERMANENTFLAGS response.
+
+ -- MUA performs automatic processing and generates corresponding MDNs
+ ("dispatched", "processed", "deleted", "denied" or "failed"
+ disposition type with "automatic-action" and "MDN-sent-
+ automatically" disposition modes) for messages that do not have
+ $MDNSent keyword, or \Draft flag set. (*)
+
+ -- MUA sets the $MDNSent keyword for every message that required an
+ automatic MDN to be sent, whether or not the MDN was sent.
+
+ -- MUA displays a list of messages to user.
+
+ -- User selects a message and requests that some action be performed
+ on it.
+
+
+
+
+Melnikov Standards Track [Page 3]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+ -- MUA performs requested action and, with user's permission, sends
+ appropriate MDN ("displayed", "dispatched", "processed",
+ "deleted", "denied" or "failed" disposition type with "manual-
+ action" and "MDN-sent-manually" or "MDN-sent-automatically"
+ disposition mode). If the generated MDN is saved to a mailbox
+ with the APPEND command, the client MUST specify the $MDNSent
+ keyword in the APPEND.
+
+ -- MUA sets the $MDNSent keyword for all messages for which the user
+ confirmed the dispatching of disposition (or was explicitly
+ prohibited to do so).
+
+ -- User possibly performs other actions on message, but no further
+ MDNs are generated.
+
+ (*) Note: MUA MUST NOT use \Recent flag as an indicator that it
+ should send MDN, because according to [IMAP4], "If multiple
+ connections have the same mailbox selected simultaneously, it is
+ undefined which of these connections will see newly-arrived
+ messages with \Recent set and which will see it without \Recent
+ set". Thus, using \Recent as an indicator will cause
+ unpredictable client behavior with different IMAP4 servers.
+ However, the client MAY use \Seen flag as one of the indicators
+ that MDN must not be sent. The client MUST NOT use any other
+ standard flags, like \Draft or \Answered, to indicate that MDN
+ was previously sent, because they have different well known
+ meaning. In any case, in the presence of the $MDNSent keyword,
+ the client MUST ignore all other flags or keywords for the
+ purpose of generating an MDN and MUST NOT send the MDN.
+
+ When the client opens a mailbox for the first time, it must verify
+ that the server supports the $MDNSent keyword, or arbitrary message
+ keywords by examining PERMANENTFLAGS response code.
+
+ The client MUST NOT try to set the $MDNSent keyword if the server is
+ incapable of storing it permanently.
+
+ The client MUST be prepared to receive NO from the server as the
+ result of STORE $MDNSent when the server advertises the support of
+ storing arbitrary keywords, because the server may limit the number
+ of message keywords it can store in a particular mailbox. A client
+ SHOULD NOT send MDN if it fails to store the $MDNSent keyword.
+
+ Once the $MDNSent keyword is set, it MUST NOT be unset by a client.
+ The client MAY set the $MDNSent keyword when a user denies sending
+ the notification. This prohibits all other MUAs from sending MDN for
+ this message.
+
+
+
+
+Melnikov Standards Track [Page 4]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+3.1. Client behavior when receiving a message
+
+ The client MUST NOT send MDN if a message has the $MDNSent keyword
+ set. It also MUST NOT send MDN if a message has \Draft flag, because
+ some clients use this flag to mark a message as incomplete.
+
+ See the timeline in section 3 for details on client behavior when
+ receiving a message.
+
+3.2. Client behavior when copying a message
+
+ The client SHOULD verify that $MDNSent is preserved on a COPY
+ operation. Furthermore, when a message is copied between servers
+ with the APPEND command, the client MUST set the $MDNSent keyword
+ correctly.
+
+3.3. Client behavior when sending a message
+
+ When saving a sent message to any folder, the client MUST set the
+ $MDNSent keyword to prevent another client from sending MDN for the
+ message.
+
+3.4. Client behavior when saving a temporary message
+
+ When saving an unfinished message to any folder client MUST set
+ $MDNSent keyword to prevent another client from sending MDN for the
+ message.
+
+4. Server behavior
+
+ Server implementors that want to follow this specification must
+ insure that their server complies with either section 4.1 or section
+ 4.2. If the server also supports the IMAP [ACL] extension, it MUST
+ also comply with the section 4.3.
+
+4.1. Server that supports arbitrary keywords
+
+ No changes are required from the server to make it compatible with
+ the extension described in this document if it supports arbitrary
+ keywords.
+
+4.2. Server that supports only $MDNSent keyword
+
+ Servers that support only the $MDNSent keyword MUST preserve it on
+ the COPY operation. It is also expected that a server that supports
+ SEARCH <flag> will also support the SEARCH KEYWORD $MDNSent.
+
+
+
+
+
+Melnikov Standards Track [Page 5]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+4.3. Interaction with IMAP ACL extension
+
+ Any server that conforms to either 4.1 or 4.2 and also supports the
+ IMAP [ACL] extension, SHOULD preserve the $MDNSent keyword on COPY
+ even if the client does not have 'w' right. This will prevent the
+ generation of a duplicated MDN for the same message. Note that the
+ server MUST still check if the client has rights to perform the COPY
+ operation on a message according to [ACL].
+
+5. Examples
+
+ 1) MUA opens mailbox for the first time.
+
+ a) The server supports storing of arbitrary keywords
+
+ C: a100 select INBOX
+ S: * FLAGS (\Flagged \Draft \Deleted \Seen)
+ S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen \*)]
+ S: * 5 EXISTS
+ S: * 3 RECENT
+ S: * OK [UIDVALIDITY 894294713]
+ S: a100 OK [READ-WRITE] Completed
+
+ b) The server supports storing of the $MDNSent keyword
+
+ C: a100 select INBOX
+ S: * FLAGS (\Flagged \Draft \Deleted \Seen $MDNSent)
+ S: * OK [PERMANENTFLAGS (\Flagged \Draft \Deleted \Seen $MDNSent)]
+ S: * 5 EXISTS
+ S: * 3 RECENT
+ S: * OK [UIDVALIDITY 894294713]
+ S: a100 OK [READ-WRITE] Completed
+
+ 2) The MUA successfully sets the $MDNSent keyword
+
+ C: a200 STORE 4 +FLAGS ($MDNSent)
+ S: * 4 FETCH (FLAGS (\Flagged \Seen $MDNSent))
+ S: * FLAGS ($MDNSent \Flagged \Deleted \Draft \Seen)
+ S: * OK [PERMANENTFLAGS ($MDNSent \Flagged \Deleted \Draft \Seen \*)]
+ S: a200 OK STORE completed
+
+ 3) The server refuses to store the $MDNSent keyword
+
+ C: a200 STORE 4 +FLAGS ($MDNSent)
+ S: a200 NO STORE failed : no space left to store $MDNSent keyword
+
+
+
+
+
+
+Melnikov Standards Track [Page 6]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+ 4) All clients and servers MUST treat the $MDNSent keyword as case
+ insensitive in all operations, as stated in [IMAP].
+
+ C: a300 FETCH 1:* FLAGS
+ S: * 1 FETCH (FLAGS (\Seen))
+ S: * 2 FETCH (FLAGS (\Answered \Seen $MdnSENt))
+ S: * 3 FETCH (FLAGS ())
+ S: * 4 FETCH (FLAGS (\Flagged \Seen $MdnSENT))
+ S: * 5 FETCH (FLAGS ($MDNSent))
+ S: * 6 FETCH (FLAGS (\Recent))
+ S: a300 OK FETCH completed
+ C: a400 SEARCH KEYWORDS $mdnsent
+ S: * SEARCH 2 4 5
+ S: a400 OK SEARCH completed
+
+6. Security Considerations
+
+ There are no known security issues with this extension, not found in
+ [MDN] and/or [IMAP4].
+
+ Section 4.3 changes ACL checking requirements on an IMAP server that
+ implements IMAP [ACL] extension.
+
+7. Formal Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (BNF) notation as specified in [RFC-822], as modified by
+ [IMAP4]. Non-terminals referenced, but not defined below, are as
+ defined by [IMAP4].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ flag_keyword ::= "$MDNSent" / other_keywords
+
+ other_keywords ::= atom
+
+8. Acknowledgments
+
+ This document is the product of discussions that took place on the
+ IMAP mailing list. Special gratitude to Cyrus Daboo and Randall
+ Gellens for reviewing the document.
+
+ Thank you to my father who as he has helped to make me what I am. I
+ miss you terribly.
+
+
+
+
+Melnikov Standards Track [Page 7]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+9. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [MDN] Fajman, R., "An Extensible Message Format for Message
+ Disposition Notifications", RFC 2298, March 1998.
+
+ [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [ACL] Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.
+
+10. Author's Address
+
+ Alexey Melnikov
+ ACI Worldwide/MessagingDirect
+ 59 Clarendon Road
+ Watford, Hertfordshire
+ United Kingdom, WD17 1FQ
+
+ Phone: +44 1923 81 2877
+ EMail: mel@messagingdirect.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 8]
+
+RFC 3503 MDN profile for IMAP March 2003
+
+
+11. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 9]
+
diff --git a/imap/docs/rfc/rfc3516.txt b/imap/docs/rfc/rfc3516.txt
new file mode 100644
index 00000000..4d021975
--- /dev/null
+++ b/imap/docs/rfc/rfc3516.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group L. Nerenberg
+Request for Comments: 3516 Orthanc Systems
+Category: Standards Track April 2003
+
+
+ IMAP4 Binary Content Extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ This memo defines the Binary extension to the Internet Message Access
+ Protocol (IMAP4). It provides a mechanism for IMAP4 clients and
+ servers to exchange message body data without using a MIME content-
+ transfer-encoding.
+
+1. Conventions Used in this Document
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as described in [KEYWORD].
+
+ The abbreviation "CTE" means content-transfer-encoding.
+
+2. Introduction
+
+ The MIME extensions to Internet messaging allow for the transmission
+ of non-textual (binary) message content [MIME-IMB]. Since the
+ traditional transports for messaging are not always capable of
+ passing binary data transparently, MIME provides encoding schemes
+ that allow binary content to be transmitted over transports that are
+ not otherwise able to do so.
+
+ The overhead of MIME-encoding this content can be considerable in
+ some contexts (e.g., slow radio links, streaming multimedia).
+ Reducing the overhead associated with CTE schemes such as base64
+
+
+
+
+
+
+Nerenberg Standards Track [Page 1]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+ can give a noticeable reduction in resource consumption. The Binary
+ extension lets the server perform CTE decoding prior to transmitting
+ message data to the client.
+
+3. Content-Transfer-Encoding Considerations
+
+ Every IMAP4 body section has a MIME content-transfer-encoding.
+ (Those without an explicit Content-Transfer-Encoding header are
+ implicitly labeled as "7bit" content.) In the terminology of [MIME-
+ IMB], the CTE specifies both a decoding algorithm and the domain of
+ the decoded data. In this memo, "decoding" refers to the CTE
+ decoding step described in [MIME-IMB].
+
+ Certain CTEs use an identity encoding transformation. For these CTEs
+ there is no decoding required, however the domain of the underlying
+ data may not be expressible in the IMAP4 protocol (e.g., MIME
+ "binary" content containing NUL octets). To accommodate these cases
+ the Binary extension introduces a new type of literal protocol
+ element that is fully eight bit transparent.
+
+ Thus, server processing of the FETCH BINARY command involves two
+ logical steps:
+
+ 1) perform any CTE-related decoding
+
+ 2) determine the domain of the decoded data
+
+ Step 2 is necessary to determine which protocol element should be
+ used to transmit the decoded data. (See FETCH Response Extensions
+ for further details.)
+
+4. Framework for the IMAP4 Binary Extension
+
+ This memo defines the following extensions to [IMAP4rev1].
+
+4.1. CAPABILITY Identification
+
+ IMAP4 servers that support this extension MUST include "BINARY" in
+ the response list to the CAPABILITY command.
+
+4.2. FETCH Command Extensions
+
+ This extension defines three new FETCH command data items.
+
+ BINARY<section-binary>[<partial>]
+
+ Requests that the specified section be transmitted after
+ performing CTE-related decoding.
+
+
+
+Nerenberg Standards Track [Page 2]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+ The <partial> argument, if present, requests that a subset of
+ the data be returned. The semantics of a partial FETCH BINARY
+ command are the same as for a partial FETCH BODY command, with
+ the exception that the <partial> arguments refer to the DECODED
+ section data.
+
+ BINARY.PEEK<section-binary>[<partial>]
+
+ An alternate form of FETCH BINARY that does not implicitly set
+ the \Seen flag.
+
+ BINARY.SIZE<section-binary>
+
+ Requests the decoded size of the section (i.e., the size to
+ expect in response to the corresponding FETCH BINARY request).
+
+ Note: client authors are cautioned that this might be an
+ expensive operation for some server implementations.
+ Needlessly issuing this request could result in degraded
+ performance due to servers having to calculate the value every
+ time the request is issued.
+
+4.3. FETCH Response Extensions
+
+ This extension defines two new FETCH response data items.
+
+ BINARY<section-binary>[<<number>>]
+
+ An <nstring> or <literal8> expressing the content of the
+ specified section after removing any CTE-related encoding. If
+ <number> is present it refers to the offset within the DECODED
+ section data.
+
+ If the domain of the decoded data is "8bit" and the data does
+ not contain the NUL octet, the server SHOULD return the data in
+ a <string> instead of a <literal8>; this allows the client to
+ determine if the "8bit" data contains the NUL octet without
+ having to explicitly scan the data stream for for NULs.
+
+ If the server does not know how to decode the section's CTE, it
+ MUST fail the request and issue a "NO" response that contains
+ the "UNKNOWN-CTE" extended response code.
+
+
+
+
+
+
+
+
+
+Nerenberg Standards Track [Page 3]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+ BINARY.SIZE<section-binary>
+
+ The size of the section after removing any CTE-related
+ encoding. The value returned MUST match the size of the
+ <nstring> or <literal8> that will be returned by the
+ corresponding FETCH BINARY request.
+
+ If the server does not know how to decode the section's CTE, it
+ MUST fail the request and issue a "NO" response that contains
+ the "UNKNOWN-CTE" extended response code.
+
+4.4. APPEND Command Extensions
+
+ The APPEND command is extended to allow the client to append data
+ containing NULs by using the <literal8> syntax. The server MAY
+ modify the CTE of the appended data, however any such transformation
+ MUST NOT result in a loss of data.
+
+ If the destination mailbox does not support the storage of binary
+ content, the server MUST fail the request and issue a "NO" response
+ that contains the "UNKNOWN-CTE" extended response code.
+
+5. MIME Encoded Headers
+
+ [MIME-MHE] defines an encoding that allows for non-US-ASCII text in
+ message headers. This encoding is not the same as the content-
+ transfer-encoding applied to message bodies, and the decoding
+ transformations described in this memo do not apply to [MIME-MHE]
+ encoded header text. A server MUST NOT perform any conversion of
+ [MIME-MHE] encoded header text in response to any binary FETCH or
+ APPEND request.
+
+6. Implementation Considerations
+
+ Messaging clients and servers have been notoriously lax in their
+ adherence to the Internet CRLF convention for terminating lines of
+ textual data in Internet protocols. When sending data using the
+ Binary extension, servers MUST ensure that textual line-oriented
+ sections are always transmitted using the IMAP4 CRLF line termination
+ syntax, regardless of the underlying storage representation of the
+ data on the server.
+
+ A server may choose to store message body binary content in a non-
+ encoded format. Regardless of the internal storage representation
+ used, the server MUST issue BODYSTRUCTURE responses that describe the
+ message as though the binary-encoded sections are encoded in a CTE
+
+
+
+
+
+Nerenberg Standards Track [Page 4]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+ acceptable to the IMAP4 base specification. Furthermore, the results
+ of a FETCH BODY MUST return the message body content in the format
+ described by the corresponding FETCH BODYSTRUCTURE response.
+
+ While the server is allowed to modify the CTE of APPENDed <literal8>
+ data, this should only be done when it is absolutely necessary.
+ Gratuitous encoding changes will render useless most cryptographic
+ operations that have been performed on the message.
+
+ This extension provides an optimization that is useful in certain
+ specific situations. It does not absolve clients from providing
+ basic functionality (content transfer decoding) that should be
+ available in all messaging clients. Clients supporting this
+ extension SHOULD be prepared to perform their own CTE decoding
+ operations.
+
+7. Formal Protocol Syntax
+
+ The following syntax specification uses the augmented Backus-Naur
+ Form (ABNF) notation as used in [ABNF], and incorporates by reference
+ the Core Rules defined in that document.
+
+ This syntax augments the grammar specified in [IMAP4rev1].
+
+ append =/ "APPEND" SP mailbox [SP flag-list]
+ [SP date-time] SP literal8
+
+ fetch-att =/ "BINARY" [".PEEK"] section-binary [partial]
+ / "BINARY.SIZE" section-binary
+
+ literal8 = "~{" number "}" CRLF *OCTET
+ ; <number> represents the number of OCTETs
+ ; in the response string.
+
+ msg-att-static =/ "BINARY" section-binary SP (nstring / literal8)
+ / "BINARY.SIZE" section-binary SP number
+
+ partial = "<" number "." nz-number ">"
+
+ resp-text-code =/ "UNKNOWN-CTE"
+
+ section-binary = "[" [section-part] "]"
+
+
+
+
+
+
+
+
+
+Nerenberg Standards Track [Page 5]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+8. Normative References
+
+ [ABNF] Crocker, D., Editor, and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+ [IMAP4rev1] Crispin, M., "Internet Message Access Protocol Version
+ 4rev1", RFC 3501, March 2003.
+
+ [KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [MIME-IMB] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [MIME-MHE] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
+ Part Three: Message Header Extensions for Non-ASCII
+ Text", RFC 2047, November 1996.
+
+9. Security Considerations
+
+ There are no known additional security issues with this extension
+ beyond those described in the base protocol described in [IMAP4rev1].
+
+10. Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ intellectual property or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; neither does it represent that it
+ has made any effort to identify any such rights. Information on the
+ IETF's procedures with respect to rights in standards-track and
+ standards-related documentation can be found in BCP-11. Copies of
+ claims of rights made available for publication and any assurances of
+ licenses to be made available, or the result of an attempt made to
+ obtain a general license or permission for the use of such
+ proprietary rights by implementors or users of this specification can
+ be obtained from the IETF Secretariat.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights which may cover technology that may be required to practice
+ this standard. Please address the information to the IETF Executive
+ Director.
+
+
+
+
+
+
+Nerenberg Standards Track [Page 6]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+11. Author's Address
+
+ Lyndon Nerenberg
+ Orthanc Systems
+ 1606 - 10770 Winterburn Road
+ Edmonton, Alberta
+ Canada T5S 1T6
+
+ EMail: lyndon@orthanc.ab.ca
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Nerenberg Standards Track [Page 7]
+
+RFC 3516 IMAP4 Binary Content Extension April 2003
+
+
+12. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Nerenberg Standards Track [Page 8]
+
diff --git a/imap/docs/rfc/rfc3656.txt b/imap/docs/rfc/rfc3656.txt
new file mode 100644
index 00000000..6c0ab5b1
--- /dev/null
+++ b/imap/docs/rfc/rfc3656.txt
@@ -0,0 +1,1067 @@
+
+
+
+
+
+
+Network Working Group R. Siemborski
+Request for Comments: 3656 Carnegie Mellon University
+Category: Experimental December 2003
+
+
+ The Mailbox Update (MUPDATE)
+ Distributed Mailbox Database Protocol
+
+Status of this Memo
+
+ This memo defines an Experimental Protocol for the Internet
+ community. It does not specify an Internet standard of any kind.
+ Discussion and suggestions for improvement are requested.
+ Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ As the demand for high-performance mail delivery agents increases, it
+ becomes apparent that single-machine solutions are inadequate to the
+ task, both because of capacity limits and that the failure of the
+ single machine means a loss of mail delivery for all users. It is
+ preferable to allow many machines to share the responsibility of mail
+ delivery.
+
+ The Mailbox Update (MUPDATE) protocol allows a group of Internet
+ Message Access Protocol (IMAP) or Post Office Protocol - Version 3
+ (POP3) servers to function with a unified mailbox namespace. This
+ document is intended to serve as a reference guide to that protocol.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 1]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
+ 2.1. Atoms . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.2. Strings . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 3. Server Responses . . . . . . . . . . . . . . . . . . . . . . 4
+ 3.1. Response: OK . . . . . . . . . . . . . . . . . . . . . 5
+ 3.2. Response: NO . . . . . . . . . . . . . . . . . . . . . 5
+ 3.3. Response: BAD . . . . . . . . . . . . . . . . . . . . . 5
+ 3.4. Response: BYE . . . . . . . . . . . . . . . . . . . . . 6
+ 3.5. Response: RESERVE . . . . . . . . . . . . . . . . . . . 6
+ 3.6. Response: MAILBOX . . . . . . . . . . . . . . . . . . . 6
+ 3.7. Response: DELETE . . . . . . . . . . . . . . . . . . . 7
+ 3.8. Server Capability Response. . . . . . . . . . . . . . . 7
+ 4. Client Commands . . . . . . . . . . . . . . . . . . . . . . . 8
+ 4.1. Command: ACTIVATE . . . . . . . . . . . . . . . . . . . 8
+ 4.2. Command: AUTHENTICATE . . . . . . . . . . . . . . . . . 8
+ 4.3. Command: DEACTIVATE . . . . . . . . . . . . . . . . . . 9
+ 4.4. Command: DELETE . . . . . . . . . . . . . . . . . . . . 9
+ 4.5. Command: FIND . . . . . . . . . . . . . . . . . . . . . 9
+ 4.6. Command: LIST . . . . . . . . . . . . . . . . . . . . . 10
+ 4.7. Command: LOGOUT . . . . . . . . . . . . . . . . . . . . 10
+ 4.8. Command: NOOP . . . . . . . . . . . . . . . . . . . . . 10
+ 4.9. Command: RESERVE. . . . . . . . . . . . . . . . . . . . 10
+ 4.10. Command: STARTTLS . . . . . . . . . . . . . . . . . . . 11
+ 4.11. Command: UPDATE . . . . . . . . . . . . . . . . . . . . 12
+ 5. MUPDATE Formal Syntax . . . . . . . . . . . . . . . . . . . . 12
+ 6. MUPDATE URL Scheme. . . . . . . . . . . . . . . . . . . . . . 14
+ 6.1. MUPDATE URL Scheme Registration Form. . . . . . . . . . 14
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
+ 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
+ 9. Intellectual Property Rights. . . . . . . . . . . . . . . . . 16
+ 10. References. . . . . . . . . . . . . . . . . . . . . . . . . . 17
+ 10.1. Normative References. . . . . . . . . . . . . . . . . . 17
+ 10.2. Informative References. . . . . . . . . . . . . . . . . 17
+ 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
+ 12. Author's Address. . . . . . . . . . . . . . . . . . . . . . . 18
+ 13. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 19
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 2]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+1. Introduction
+
+ In order to support an architecture where there are multiple [IMAP,
+ POP3] servers sharing a common mailbox database, it is necessary to
+ be able to provide atomic mailbox operations, as well as offer
+ sufficient guarantees about database consistency.
+
+ The primary goal of the MUPDATE protocol is to be simple to implement
+ yet allow for database consistency between participants.
+
+ The key words "MUST, "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
+ "RECOMMENDED", and "MAY" in this document are to be interpreted as
+ defined in BCP 14, RFC 2119 [KEYWORDS].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+2. Protocol Overview
+
+ The MUPDATE protocol assumes a reliable data stream such as a TCP
+ network connection. IANA has registered port 3905 with a short name
+ of "mupdate" for this purpose.
+
+ In the current implementation of the MUPDATE protocol there are three
+ types of participants: a single master server, slave (or replica)
+ servers, and clients. The master server maintains an authoritative
+ copy of the mailbox database. Slave servers connect to the MUPDATE
+ master server as clients, and function as replicas from the point of
+ view of end clients. End clients may connect to either the master or
+ any slave and perform searches against the database, however
+ operations that change the database can only be performed against the
+ master. For the purposes of protocol discussion we will consider a
+ slave's connection to the master identical to that of any other
+ client.
+
+ After connection, all commands from a client to server must have an
+ associated unique tag which is an alphanumeric string. Commands MAY
+ be pipelined from the client to the server (that is, the client need
+ not wait for the response before sending the next command). The
+ server MUST execute the commands in the order they were received,
+ however.
+
+ If the server supports an inactivity login timeout, it MUST be at
+ least 15 minutes.
+
+
+
+
+
+
+
+Siemborski Experimental [Page 3]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ MUPDATE uses data formats similar to those used in [ACAP]. That is,
+ atoms and strings. All commands and tags in the protocol are
+ transmitted as atoms. All other data is considered to a string, and
+ must be quoted or transmitted as a literal.
+
+ Outside of a literal, both clients and servers MUST support line
+ lengths of at least 1024 octets (including the trailing CR and LF
+ characters). If a line of a longer length must be transmitted,
+ implementations MUST make use of literals to do so.
+
+2.1. Atoms
+
+ An atom consists of one or more alphanumeric characters. Atoms MUST
+ be less than 15 octets in length.
+
+2.2. Strings
+
+ As in [ACAP], a string may be either literal or a quoted string. A
+ literal is a sequence of zero or more octets (including CR and LF),
+ prefix-quoted with an octet count in the form of an open brace ("{"),
+ the number of octets, an optional plus sign to indicate that the data
+ follows immediately (a non-synchronized literal), a close brace
+ ("}"), and a CRLF sequence. If the plus sign is omitted (a
+ synchronized literal), then the receiving side MUST send a "+ go
+ ahead" response, and the sending side MUST wait for this response.
+ Servers MUST support literals of atleast 4096 octets.
+
+ Strings that are sent from server to client SHOULD NOT be in the
+ synchronized literal format.
+
+ A quoted string is a sequence of zero or more 7-bit characters,
+ excluding CR, LF, and the double quote (<">), with double quote
+ characters at each end.
+
+ The empty string is represented as either "" (a quoted string with
+ zero characters between double quotes) or as {0} followed by CRLF (a
+ literal with an octet count of 0).
+
+3. Server Responses
+
+ Every client command in the MUPDATE protocol may receive one or more
+ tagged responses from the server. Each response is preceded by the
+ same tag as the command that elicited the response from the server.
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 4]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.1. Response: OK
+
+ A tagged OK response indicates that the operation completed
+ successfully. There is a mandatory implementation-defined string
+ after the OK response. This response also indicates the beginning of
+ the streaming update mode when given in response to an UPDATE
+ command.
+
+ Example:
+
+C: N01 NOOP
+S: N01 OK "NOOP Complete"
+
+3.2. Response: NO
+
+ A tagged NO response indicates that the operation was explicitly
+ denied by the server or otherwise failed. There is a mandatory
+ implementation-defined string after the NO response that SHOULD
+ explain the reason for denial.
+
+ Example:
+
+C: A01 AUTHENTICATE "PLAIN"
+S: A01 NO "PLAIN is not a supported SASL mechanism"
+
+3.3. Response: BAD
+
+ A tagged BAD response indicates that the command from the client
+ could not be parsed or understood. There is a mandatory
+ implementation-defined string after the BAD response to provide
+ additional information about the error. Note that untagged BAD
+ responses are allowed if it is unclear what the tag for a given
+ command is (for example, if a blank line is received by the mupdate
+ server, it can generate an untagged BAD response). In the case of an
+ untagged response, the tag should be replaced with a "*".
+
+ Example:
+
+C: C01 SELECT "INBOX"
+S: C01 BAD "This is not an IMAP server"
+C:
+S: * BAD "Need Command"
+
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 5]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.4. Response: BYE
+
+ A tagged BYE response indicates that the server has decided to close
+ the connection. There is a mandatory implementation-defined string
+ after the BYE response that SHOULD explain the reason for closing the
+ connection. The server MUST close the connection immediately after
+ transmitting the BYE response.
+
+ Example:
+
+C: L01 LOGOUT
+S: L01 BYE "User Logged Out"
+
+3.5. Response: RESERVE
+
+ A tagged RESERVE response may only be given in response to a FIND,
+ LIST, or UPDATE command. It includes two parameters: the name of the
+ mailbox that is being reserved (in mUTF-7 encoding, as specified in
+ [IMAP]) and a location string whose contents is defined by the
+ clients that are using the database, though it is RECOMMENDED that
+ the format of this string be the hostname of the server which is
+ storing the mailbox.
+
+ This response indicates that the given name is no longer available in
+ the namespace, though it does not indicate that the given mailbox is
+ available to clients at the current time.
+
+ Example:
+
+S: U01 RESERVE "internet.bugtraq" "mail2.example.org"
+
+3.6. Response: MAILBOX
+
+ A tagged MAILBOX response may only be given in response to a FIND,
+ LIST, or UPDATE command. It includes three parameters: the name of
+ the mailbox, a location string (as with RESERVE), and a client-
+ defined string that specifies the IMAP ACL [IMAP-ACL] of the mailbox.
+ This message indicates that the given mailbox is ready to be accessed
+ by clients.
+
+ Example:
+
+S: U01 MAILBOX "internet.bugtraq" "mail2.example.org" "anyone rls"
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 6]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+3.7. Response: DELETE
+
+ A tagged DELETE response may only be given in response to an UPDATE
+ command, and MUST NOT be given before the OK response to the UPDATE
+ command is given. It contains a single parameter, that of the
+ mailbox that should be deleted from the slave's database. This
+ response indicates that the given mailbox no longer exists in the
+ namespace of the database, and may be given for any mailbox name,
+ active, reserved, or nonexistent. (Though implementations SHOULD NOT
+ issue DELETE responses for nonexistent mailboxes).
+
+ Example:
+
+S: U01 DELETE "user.rjs3.sent-mail-jan-2002"
+
+3.8. Server Capability Response
+
+ Upon connection of the client to the server, and directly following a
+ successful STARTTLS command, the server MUST issue a capabilities
+ banner, of the following format:
+
+ The banner MUST contain a line that begins with "* AUTH" and contain
+ a space-separated list of SASL mechanisms that the server will accept
+ for authentication. The mechanism names are transmitted as atoms.
+ Servers MAY advertise no available mechanisms (to indicate that
+ STARTTLS must be completed before authentication may occur). If
+ STARTTLS is not supported by the server, then the line MUST contain
+ at least one mechanism.
+
+ If the banner is being issued without a TLS layer, and the server
+ supports the STARTTLS command, the banner MUST contain the line "*
+ STARTTLS". If the banner is being issued under a TLS layer (or the
+ server does not support STARTTLS), the banner MUST NOT contain this
+ line.
+
+ The last line of the banner MUST start with "* OK MUPDATE" and be
+ followed by four strings: the server's hostname, an implementation-
+ defined string giving the name of the implementation, an
+ implementation-defined string giving the version of the
+ implementation, and a string that indicates if the server is a master
+ or a slave. The master/slave indication MUST be either "(master)" or
+ an MUPDATE URL that defines where the master can be contacted.
+
+ Any unrecognized responses before the "* OK MUPDATE" response MUST be
+ ignored by the client.
+
+
+
+
+
+
+Siemborski Experimental [Page 7]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ Example:
+
+S: * AUTH KERBEROS_V4 GSSAPI
+S: * STARTTLS
+S: * OK MUPDATE "mupdate.example.org" "Cyrus" "v2.1.2" "(master)"
+
+4. Client Commands
+
+ The following are valid commands that a client may send to the
+ MUPDATE server: AUTHENTICATE, ACTIVATE, DEACTIVATE, DELETE, FIND,
+ LIST, LOGOUT, NOOP, RESERVE, STARTTLS, and UPDATE.
+
+ Before a successful AUTHENTICATE command has occurred, the server
+ MUST NOT accept any commands except for AUTHENTICATE, STARTTLS, and
+ LOGOUT (and SHOULD reply with a NO response for all other commands).
+
+4.1. Command: ACTIVATE
+
+ The ACTIVATE command has 3 parameters: the mailbox name, its
+ location, and its ACL. This command MUST NOT not be issued to a
+ slave server.
+
+ This command can also be used to update the ACL or location
+ information of a mailbox. Note that it is not a requirement for a
+ mailbox to be reserved (or even exist in the database) for an
+ ACTIVATE command to succeed, implementations MUST allow this behavior
+ as it facilitates synchronization of the database with the current
+ state of the mailboxes.
+
+4.2. Command: AUTHENTICATE
+
+ The AUTHENTICATE command initiates a [SASL] negotiation session
+ between the client and the server. It has two parameters. The first
+ parameter is mandatory, and is a string indicating the desired [SASL]
+ mechanism. The second is a string containing an optional BASE64
+ encoded (as defined in section 6.8 of [MIME]) client first send.
+
+ All of the remaining SASL blobs that are sent MUST be sent across the
+ wire must be in BASE64 encoded format, and followed by a CR and LF
+ combination. They MUST NOT be encoded as strings.
+
+ Clients may cancel authentication by sending a * followed by a CR and
+ LF.
+
+ The [SASL] service name for the MUPDATE protocol is "mupdate".
+ Implementations are REQUIRED to implement the GSSAPI [SASL]
+ mechanism, though they SHOULD implement as many mechanisms as
+ possible.
+
+
+
+Siemborski Experimental [Page 8]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ If a security layer is negotiated, it should be used directly
+ following the CR and LF combination at the end of the server's OK
+ response (i.e., beginning with the client's next command) Only one
+ successful AUTHENTICATE command may be issued per session.
+
+4.3. Command: DEACTIVATE
+
+ The DEACTIVATE command takes two parameters, the mailbox name and
+ location data. The mailbox MUST already exist and be activated on
+ the MUPDATE server. If the server responds OK, then the mailbox name
+ has been moved to the RESERVE state. If the server responds NO, then
+ the mailbox name has not been moved (for example, the mailbox was not
+ already active). Any ACL information that is known about the mailbox
+ MAY be lost when a DEACTIVATE succeeds. This command MUST NOT be
+ issued to a slave.
+
+ Example:
+
+C: A01 DEACTIVATE "user.rjs3.new" "mail3.example.org!u4"
+S: A01 OK "Mailbox Reserved."
+
+4.4. Command: DELETE
+
+ The DELETE command takes only a single parameter, the mailbox name to
+ be removed from the database's namespace. The server SHOULD give a
+ NO response if the mailbox does not exist. This command MUST NOT be
+ issued to a slave server.
+
+4.5. Command: FIND
+
+ The FIND command takes a single parameter, a mailbox name. The
+ server then responds with the current record for the given mailbox,
+ if any, and an OK response.
+
+ Example (mailbox does not exist):
+
+C: F01 FIND "user.rjs3.xyzzy"
+S: F01 OK "Search Complete"
+
+ Example (mailbox is reserved):
+
+C: F01 FIND "user.rjs3"
+S: F01 RESERVE "user.rjs3" "mail4.example.org"
+S: F01 OK "Search Complete"
+
+
+
+
+
+
+
+Siemborski Experimental [Page 9]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+4.6. Command: LIST
+
+ The LIST command is similar to running FIND across the entire
+ database. The LIST command takes a single optional parameter, which
+ is a prefix to try to match against the location field of the
+ records. Without the parameter, LIST returns every record in the
+ database.
+
+ For each mailbox that matches, either a MAILBOX or a RESERVE response
+ (as applicable) is sent to the client. When all responses are
+ complete, an OK response is issued.
+
+ Example:
+
+C: L01 LIST
+S: L01 RESERVE "user.rjs3" "mail4.example.org!u2"
+S: L01 MAILBOX "user.leg" "mail2.example.org!u1" "leg lrswipcda"
+S: L01 OK "List Complete"
+C: L02 LIST "mail4.example.org!"
+S: L02 RESERVE "user.rjs3" "mail4.example.org!u2"
+S: L02 OK "List Complete"
+
+4.7. Command: LOGOUT
+
+ The LOGOUT command tells the server to close the connection. Its
+ only valid response is the BYE response. The LOGOUT command takes no
+ parameters.
+
+4.8. Command: NOOP
+
+ The NOOP command takes no parameters. Provided the client is
+ authenticated, its only acceptable response is an OK. Any idle
+ timeouts that the server may have on the connection SHOULD be reset
+ upon receipt of this command.
+
+ If this command is issued after an UPDATE command has been issued,
+ then the OK response also indicates that all pending database updates
+ have been sent to the client. That is, the slave can guarantee that
+ its local database is up to date as of a certain time by issuing a
+ NOOP and waiting for the OK. The OK MUST NOT return until all
+ updates that were pending at the time of the NOOP have been sent.
+
+4.9. Command: RESERVE
+
+ The RESERVE command takes two parameters (just like the RESERVE
+ response), the mailbox name to reserve and location data. If the
+ server responds OK, then the mailbox name has been reserved. If the
+ server responds NO, then the mailbox name has not been reserved (for
+
+
+
+Siemborski Experimental [Page 10]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ example, another server has reserved it already). This command MUST
+ NOT be issued to a slave.
+
+ The typical sequence for mailbox creation is:
+
+C: R01 RESERVE "user.rjs3.new" "mail3.example.org!u4"
+S: R01 OK "Mailbox Reserved."
+<client does local mailbox create operations>
+C: A01 ACTIVATE "user.rjs3.new" "mail3.example.org!u4" "rjs3 lrswipcda"
+S: A01 OK "Mailbox Activated."
+
+4.10. Command: STARTTLS
+
+ The STARTTLS command requests the commencement of a [TLS]
+ negotiation. The negotiation begins immediately after the CRLF in
+ the OK response. After a client issues a STARTTLS command, it MUST
+ NOT issue further commands until a server response is seen and the
+ [TLS] negotiation is complete.
+
+ The STARTTLS command is only valid in non-authenticated state. The
+ server remains in non-authenticated state, even if client credentials
+ are supplied during the [TLS] negotiation. The [SASL] EXTERNAL
+ mechanism MAY be used to authenticate once [TLS] client credentials
+ are successfully exchanged. Note that servers are not required to
+ support the EXTERNAL mechanism.
+
+ After the [TLS] layer is established, the server MUST re-issue the
+ initial response banner (see Section 3.8). This is necessary to
+ protect against man-in-the-middle attacks which alter the
+ capabilities list prior to STARTTLS, as well as to advertise any new
+ SASL mechanisms (or other capabilities) that may be available under
+ the layer. The client MUST discard cached capability information and
+ replace it with the new information.
+
+ After the a successful STARTTLS command, the server SHOULD return a
+ NO response to additional STARTTLS commands.
+
+ Servers MAY choose to not implement STARTTLS. In this case, they
+ MUST NOT advertise STARTTLS in their capabilities banner, and SHOULD
+ return a BAD response to the STARTTLS command, if it is issued.
+
+ Example:
+
+C: S01 STARTTLS
+S: S01 OK "Begin TLS negotiation now"
+<TLS negotiation, further commands are under TLS layer>
+S: * AUTH KERBEROS_V4 GSSAPI PLAIN
+S: * OK MUPDATE "mupdate.example.org" "Cyrus" "v2.1.2" "(master)"
+
+
+
+Siemborski Experimental [Page 11]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+4.11. Command: UPDATE
+
+ The UPDATE command is how a slave initializes an update stream from
+ the master (though it is also valid to issue this command to a
+ slave). In response to the command, the server returns a list of all
+ mailboxes in its database (the same results as a parameterless LIST
+ command) followed by an OK response. From this point forward,
+ whenever an update occurs to the master database, it MUST stream the
+ update to the slave within 30 seconds. That is, it will send
+ RESERVE, MAILBOX, or DELETE responses as they are applicable.
+
+ After a client has issued an UPDATE command, it may only issue NOOP
+ and LOGOUT commands for the remainder of the session.
+
+ Example:
+
+C: U01 UPDATE
+S: U01 MAILBOX "user.leg" "mail2.example.org!u1" "leg lrswipcda"
+S: U01 MAILBOX "user.rjs3" "mail3.example.org!u4" "rjs3 lrswipcda"
+S: U01 RESERVE "internet.bugtraq" "mail1.example.org!u5" "anyone lrs"
+S: U01 OK "Streaming Begins"
+<some time goes by, and another client creates a new mailbox>
+S: U01 RESERVE "user.leg.new" "mail2.example.org!u1"
+<some more time passes, and the create succeeds>
+S: U01 MAILBOX "user.leg.new" "mail2.example.org!u1" "leg lrswipcda"
+<much more time passes, and the slave decides to send a NOOP to reset
+its inactivity timer>
+C: N01 NOOP
+S: U01 DELETE "user.leg.new"
+S: N01 OK "NOOP Complete"
+
+5. MUPDATE Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF]. This uses the ABNF core
+ rules as specified in Appendix A of [ABNF].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ Note that this specification also uses some terminals from section 8
+ of [ACAP].
+
+ cmd-activate = "ACTIVATE" SP string SP string SP string
+
+ cmd-authenticate = "AUTHENTICATE" SP sasl-mech [ SP string ]
+
+
+
+Siemborski Experimental [Page 12]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ cmd-delete = "DELETE" SP string
+
+ cmd-find = "FIND" SP string
+
+ cmd-list = "LIST" [ SP string ]
+
+ cmd-logout = "LOGOUT"
+
+ cmd-noop = "NOOP"
+
+ cmd-reserve = "RESERVE" SP string SP string
+
+ cmd-starttls = "STARTTLS"
+
+ cmd-update = "UPDATE"
+
+ command = tag SP command-type CRLF
+
+ command-type = cmd-activate / cmd-authenticate / cmd-delete /
+ cmd-find / cmd-list / cmd-logout / cmd-noop /
+ cmd-reserve / cmd-starttls / cmd-update
+
+ response = tag SP response-type CRLF
+
+ response-type = rsp-ok / rsp-no / rsp-bad / rsp-bye / rsp-mailbox /
+ rsp-reserve / rsp-delete
+
+ rsp-bad = "BAD" SP string
+
+ rsp-bye = "BYE" SP string
+
+ rsp-mailbox = "MAILBOX" SP string SP string SP string
+
+ rsp-no = "NO" SP string
+
+ rsp-ok = "OK" SP string
+
+ rsp-reserve = "RESERVE" SP string SP string
+
+ rsp-delete = "DELETE" SP string
+
+ sasl-mech = 1*ATOM-CHAR
+ ; ATOM-CHAR is defined in [ACAP]
+
+ string = quoted / literal
+ ; quoted and literal are defined in [ACAP]
+
+
+
+
+
+Siemborski Experimental [Page 13]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ tag = 1*ATOM-CHAR
+ ; ATOM-CHAR is defined in [ACAP]
+
+6. MUPDATE URL Scheme
+
+ This document defines the a URL scheme for the purposes of
+ referencing MUPDATE resources, according to the requirements in
+ [RFC2717]. This includes both MUPDATE servers as a whole, along with
+ individual mailbox entries on a given MUPDATE server.
+
+ There is no MIME type associated with these resources. It is
+ intended that a URL consumer would either retrieve the MUPDATE record
+ in question, or simply connect to the MUPDATE server running on the
+ specified host. Note that the consumer will need to have
+ authentication credentials for the specified host.
+
+ The MUPDATE URL scheme is similar to the IMAP URL scheme [IMAP-URL].
+ However, it only takes one of two possible forms:
+
+ mupdate://<iserver>/
+ mupdate://<iserver>/<mailbox>
+
+ The first form refers to a MUPDATE server as a whole, the second form
+ indicates both the server and a mailbox to run a FIND against once
+ authenticated to the server. Note that part of <iserver> may include
+ username and authentication information along with a hostname and
+ port.
+
+6.1. MUPDATE URL Scheme Registration Form
+
+ URL scheme name: "mupdate"
+
+ URL scheme syntax:
+
+ This defines the MUPDATE URL Scheme in [ABNF]. Terminals from the
+ BNF of IMAP URLs [IMAP-URL] are also used.
+
+ mupdateurl = "mupdate://" iserver "/" [ enc_mailbox ]
+ ; iserver and enc_mailbox are as defined in [IMAP-URL]
+
+ Character encoding considerations:
+
+ Identical to those described in [IMAP-URL] for the appropriate
+ terminals.
+
+
+
+
+
+
+
+Siemborski Experimental [Page 14]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ Intended Usage:
+
+ The form of the URL without an associated mailbox is intended to
+ designate a MUPDATE server only. If a mailbox name is included in
+ the URL, then the consumer is expected to execute a FIND command
+ for that mailbox on the specified server.
+
+ Applications and/or protocols which use this URL scheme name:
+
+ The protocol described in this document.
+
+ Interoperability Considerations:
+
+ None.
+
+ Security Considerations:
+
+ Users of the MUPDATE URL Scheme should review the security
+ considerations that are discussed in [IMAP-URL]. In particular,
+ the consequences of including authentication mechanism information
+ in a URL should be reviewed.
+
+ Relevant Publications:
+
+ This document and [IMAP-URL].
+
+ Author, Change Controller, and Contact for Further Information:
+
+ Author of this document.
+
+7. Security Considerations
+
+ While no unauthenticated users may make modifications or even perform
+ searches on the database, it is important to note that this
+ specification assumes no protections of any type for authenticated
+ users.
+
+ All authenticated users have complete access to the database. For
+ this reason it is important to ensure that accounts that are making
+ use of the database are well secured.
+
+ A more secure deployment might have all read only access go through a
+ slave, and only have accounts which need write access use the master.
+ This has the disadvantage of a marginally longer time for updates to
+ reach the clients.
+
+
+
+
+
+
+Siemborski Experimental [Page 15]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+ The protocol assumes that all authenticated users are cooperating to
+ maintain atomic operations. Therefore, all new mailboxes SHOULD be
+ RESERVEd before they are ACTIVATEd, despite the fact that the
+ protocol does not require this, and it is therefore possible for a
+ set of participants which do not obey the provided locking to create
+ an inconsistent database. RESERVEing the mailbox first is not
+ required to perform an activate because this behavior simplifies
+ synchronization with the actual location of the mailboxes.
+
+8. IANA Considerations
+
+ The IANA has assigned TCP port number 3905 to "mupdate".
+
+ The IANA has registered a URL scheme for the MUPDATE protocol, as
+ defined in section 6.1 of this document.
+
+ IANA has registered a GSSAPI service name of "mupdate" for the
+ MUPDATE protocol in the registry maintained at:
+
+ http://www.iana.org/assignments/gssapi-service-names
+
+9. Intellectual Property Rights
+
+ The IETF takes no position regarding the validity or scope of any
+ intellectual property or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; neither does it represent that it
+ has made any effort to identify any such rights. Information on the
+ IETF's procedures with respect to rights in standards-track and
+ standards-related documentation can be found in BCP-11. Copies of
+ claims of rights made available for publication and any assurances of
+ licenses to be made available, or the result of an attempt made to
+ obtain a general license or permission for the use of such
+ proprietary rights by implementors or users of this specification can
+ be obtained from the IETF Secretariat.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights which may cover technology that may be required to practice
+ this standard. Please address the information to the IETF Executive
+ Director.
+
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 16]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+10. References
+
+10.1. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+ 4", RFC 3501, March 2003.
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November 1997.
+
+ [MIME] Freed, N. and N. Bornstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [IMAP-ACL] Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.
+
+ [SASL] Myers, J., "Simple Authentication and Security Layer
+ (SASL)", RFC 2222, October 1997.
+
+ [IMAP-URL] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November 1997.
+
+ [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
+ RFC 2246, January 1999.
+
+10.2. Informative References
+
+ [POP3] Myers, J. and M. Rose, "Post Office Protocol - Version
+ 3", STD 53, RFC 1939, May 1996.
+
+ [RFC2717] Petke, R. and I. King, "Registration Procedures for URL
+ Scheme Names", BCP 35, RFC 2717, November 1999.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski Experimental [Page 17]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+11. Acknowledgments
+
+ Lawrence Greenfield and Ken Murchison, for a great deal of input on
+ both the protocol and the text of the documents.
+
+12. Author's Address
+
+ Robert Siemborski
+ Carnegie Mellon, Andrew Systems Group
+ Cyert Hall 207
+ 5000 Forbes Avenue
+ Pittsburgh, PA 15213
+
+ Phone: (412) 268-7456
+ EMail: rjs3+@andrew.cmu.edu
+
+
+
+
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+Siemborski Experimental [Page 18]
+
+RFC 3656 MUPDATE Distributed Mailbox Database Protocol December 2003
+
+
+13. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+ This document and translations of it may be copied and furnished to
+ others, and derivative works that comment on or otherwise explain it
+ or assist in its implementation may be prepared, copied, published
+ and distributed, in whole or in part, without restriction of any
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assignees.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
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+Siemborski Experimental [Page 19]
+
diff --git a/imap/docs/rfc/rfc3691.txt b/imap/docs/rfc/rfc3691.txt
new file mode 100644
index 00000000..2f4e9b44
--- /dev/null
+++ b/imap/docs/rfc/rfc3691.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 3691 Isode Ltd.
+Category: Standards Track February 2004
+
+
+ Internet Message Access Protocol (IMAP) UNSELECT command
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2004). All Rights Reserved.
+
+Abstract
+
+ This document defines an UNSELECT command that can be used to close
+ the current mailbox in an Internet Message Access Protocol - version
+ 4 (IMAP4) session without expunging it. Certain types of IMAP
+ clients need to release resources associated with the selected
+ mailbox without selecting a different mailbox. While IMAP4 provides
+ this functionality (via a SELECT command with a nonexistent mailbox
+ name or reselecting the same mailbox with EXAMINE command), a more
+ clean solution is desirable.
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. UNSELECT command . . . . . . . . . . . . . . . . . . . . . . . 2
+ 3. Security Considerations. . . . . . . . . . . . . . . . . . . . 3
+ 4. Formal Syntax. . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 5. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 3
+ 6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 3
+ 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4
+ 8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 4
+ 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 5
+
+
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+
+
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+
+Melnikov Standards Track [Page 1]
+
+RFC 3691 IMAP UNSELECT command February 2004
+
+
+1. Introduction
+
+ Certain types of IMAP clients need to release resources associated
+ with the selected mailbox without selecting a different mailbox.
+ While [IMAP4] provides this functionality (via a SELECT command with
+ a nonexistent mailbox name or reselecting the same mailbox with
+ EXAMINE command), a more clean solution is desirable.
+
+ [IMAP4] defines the CLOSE command that closes the selected mailbox as
+ well as permanently removes all messages with the \Deleted flag set.
+
+ However [IMAP4] lacks a command that simply closes the mailbox
+ without expunging it. This document defines the UNSELECT command for
+ this purpose.
+
+ A server which supports this extension indicates this with a
+ capability name of "UNSELECT".
+
+ "C:" and "S:" in examples show lines sent by the client and server
+ respectively.
+
+ The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
+ this document when typed in uppercase are to be interpreted as
+ defined in "Key words for use in RFCs to Indicate Requirement Levels"
+ [KEYWORDS].
+
+2. UNSELECT Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - unselect completed, now in authenticated state
+ BAD - no mailbox selected, or argument supplied but
+ none permitted
+
+ The UNSELECT command frees server's resources associated with the
+ selected mailbox and returns the server to the authenticated
+ state. This command performs the same actions as CLOSE, except
+ that no messages are permanently removed from the currently
+ selected mailbox.
+
+ Example: C: A341 UNSELECT
+ S: A341 OK Unselect completed
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 2]
+
+RFC 3691 IMAP UNSELECT command February 2004
+
+
+3. Security Considerations
+
+ It is believed that this extension doesn't raise any additional
+ security concerns not already discussed in [IMAP4].
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF]. Non-terminals
+ referenced but not defined below are as defined by [IMAP4].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ command-select /= "UNSELECT"
+
+5. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ This document defines the UNSELECT IMAP capabilities. IANA has added
+ this capability to the registry.
+
+6. Acknowledgments
+
+ UNSELECT command was originally implemented by Tim Showalter in Cyrus
+ IMAP server.
+
+ Also, the author of the document would like to thank Vladimir Butenko
+ and Mark Crispin for reminding that UNSELECT has to be documented.
+ Also thanks to Simon Josefsson for pointing out that there are
+ multiple ways to implement UNSELECT.
+
+
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+Melnikov Standards Track [Page 3]
+
+RFC 3691 IMAP UNSELECT command February 2004
+
+
+7. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 2234, November 1997.
+
+8. Author's Address
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ Hampton, Middlesex TW12 2BX
+
+ EMail: Alexey.Melnikov@isode.com
+ URI: http://www.melnikov.ca/
+
+
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+Melnikov Standards Track [Page 4]
+
+RFC 3691 IMAP UNSELECT command February 2004
+
+
+9. Full Copyright Statement
+
+ Copyright (C) The Internet Society (2004). This document is subject
+ to the rights, licenses and restrictions contained in BCP 78 and
+ except as set forth therein, the authors retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
+ REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
+ INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed
+ to pertain to the implementation or use of the technology
+ described in this document or the extent to which any license
+ under such rights might or might not be available; nor does it
+ represent that it has made any independent effort to identify any
+ such rights. Information on the procedures with respect to
+ rights in RFC documents can be found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use
+ of such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository
+ at http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention
+ any copyrights, patents or patent applications, or other
+ proprietary rights that may cover technology that may be required
+ to implement this standard. Please address the information to the
+ IETF at ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 5]
+
diff --git a/imap/docs/rfc/rfc4314.txt b/imap/docs/rfc/rfc4314.txt
new file mode 100644
index 00000000..e73a56f2
--- /dev/null
+++ b/imap/docs/rfc/rfc4314.txt
@@ -0,0 +1,1515 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 4314 Isode Ltd.
+Obsoletes: 2086 December 2005
+Category: Standards Track
+
+
+ IMAP4 Access Control List (ACL) Extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2005).
+
+Abstract
+
+ The Access Control List (ACL) extension (RFC 2086) of the Internet
+ Message Access Protocol (IMAP) permits mailbox access control lists
+ to be retrieved and manipulated through the IMAP protocol.
+
+ This document is a revision of RFC 2086. It defines several new
+ access control rights and clarifies which rights are required for
+ different IMAP commands.
+
+
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+
+Melnikov Standards Track [Page 1]
+
+RFC 4314 IMAP ACL December 2005
+
+
+Table of Contents
+
+ 1. Introduction and Overview .......................................3
+ 1.1. Conventions Used in This Document ..........................3
+ 2. Access Control ..................................................3
+ 2.1. Standard Rights ............................................5
+ 2.1.1. Obsolete Rights .....................................5
+ 2.2. Rights Defined in RFC 2086 .................................8
+ 3. Access control management commands and responses ................8
+ 3.1. SETACL Command .............................................8
+ 3.2. DELETEACL Command ..........................................9
+ 3.3. GETACL Command ............................................10
+ 3.4. LISTRIGHTS Command ........................................10
+ 3.5. MYRIGHTS Command ..........................................11
+ 3.6. ACL Response ..............................................11
+ 3.7. LISTRIGHTS Response .......................................12
+ 3.8. MYRIGHTS Response .........................................12
+ 4. Rights Required to Perform Different IMAP4rev1 Commands ........12
+ 5. Other Considerations ...........................................17
+ 5.1. Additional Requirements and Implementation Notes ..........17
+ 5.1.1. Servers ............................................17
+ 5.1.2. Clients ............................................18
+ 5.2. Mapping of ACL Rights to READ-WRITE and READ-ONLY
+ Response Codes ............................................19
+ 6. Security Considerations ........................................20
+ 7. Formal Syntax ..................................................21
+ 8. IANA Considerations ............................................22
+ 9. Internationalization Considerations ............................22
+ Appendix A. Changes since RFC 2086 ................................23
+ Appendix B. Compatibility with RFC 2086 ...........................24
+ Appendix C. Known Deficiencies ....................................24
+ Appendix D. Acknowledgements ......................................25
+ Normative References ..............................................25
+ Informative References ............................................25
+
+
+
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+Melnikov Standards Track [Page 2]
+
+RFC 4314 IMAP ACL December 2005
+
+
+1. Introduction and Overview
+
+ The ACL (Access Control List) extension of the Internet Message
+ Access Protocol [IMAP4] permits mailbox access control lists to be
+ retrieved and manipulated through the IMAP protocol.
+
+ This document is a revision of RFC 2086 [RFC2086]. It tries to
+ clarify different ambiguities in RFC 2086, in particular, the use of
+ UTF-8 [UTF-8] in access identifiers, which rights are required for
+ different IMAP4 commands, and how READ-WRITE/READ-ONLY response codes
+ are related to ACL.
+
+1.1. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively.
+
+ In all examples "/" character is used as hierarchy separator.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+ The phrase "ACL server" is just a shortcut for saying "IMAP server
+ that supports ACL extension as defined in this document".
+
+2. Access Control
+
+ The ACL extension is present in any IMAP4 implementation that returns
+ "ACL" as one of the supported capabilities to the CAPABILITY command.
+
+ A server implementation conformant to this document MUST also return
+ rights (see below) not defined in Section 2.2 in the "RIGHTS="
+ capability.
+
+ An access control list is a set of <access identifier,rights> pairs.
+ An ACL applies to a mailbox name.
+
+ Access identifier (or just "identifier") is a UTF-8 [UTF-8] string.
+ The identifier "anyone" is reserved to refer to the universal
+ identity (all authentications, including anonymous). All user name
+ strings accepted by the LOGIN or AUTHENTICATE commands to
+ authenticate to the IMAP server are reserved as identifiers for the
+ corresponding users. Identifiers starting with a dash ("-") are
+ reserved for "negative rights", described below. All other
+ identifier strings are interpreted in an implementation-defined
+ manner.
+
+
+
+
+Melnikov Standards Track [Page 3]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ Rights is a string listing a (possibly empty) set of alphanumeric
+ characters, each character listing a set of operations that is being
+ controlled. Lowercase letters are reserved for "standard" rights,
+ listed in Section 2.1. (Note that for compatibility with deployed
+ clients and servers uppercase rights are not allowed.) The set of
+ standard rights can only be extended by a standards-track document.
+ Digits are reserved for implementation- or site-defined rights.
+
+ An implementation MAY tie rights together or MAY force rights to
+ always or never be granted to particular identifiers. For example,
+ in an implementation that uses UNIX mode bits, the rights "swite" are
+ tied, the "a" right is always granted to the owner of a mailbox and
+ is never granted to another user. If rights are tied in an
+ implementation, the implementation must be conservative in granting
+ rights in response to SETACL commands--unless all rights in a tied
+ set are specified, none of that set should be included in the ACL
+ entry for that identifier. A client can discover the set of rights
+ that may be granted to a given identifier in the ACL for a given
+ mailbox name by using the LISTRIGHTS command.
+
+ It is possible for multiple identifiers in an access control list to
+ apply to a given user. For example, an ACL may include rights to be
+ granted to the identifier matching the user, one or more
+ implementation-defined identifiers matching groups that include the
+ user, and/or the identifier "anyone". How these rights are combined
+ to determine the user's access is implementation defined. An
+ implementation may choose, for example, to use the union of the
+ rights granted to the applicable identifiers. An implementation may
+ instead choose, for example, to use only those rights granted to the
+ most specific identifier present in the ACL. A client can determine
+ the set of rights granted to the logged-in user for a given mailbox
+ name by using the MYRIGHTS command.
+
+ When an identifier in an ACL starts with a dash ("-"), that indicates
+ that associated rights are to be removed from the identifier prefixed
+ by the dash. This is referred to as a "negative right". This
+ differs from DELETEACL in that a negative right is added to the ACL
+ and is a part of the calculation of the rights.
+
+ Let's assume that an identifier "fred" refers to a user with login
+ "fred". If the identifier "-fred" is granted the "w" right, that
+ indicates that the "w" right is to be removed from users matching the
+ identifier "fred", even though the user "fred" might have the "w"
+ right as a consequence of some other identifier in the ACL. A
+ DELETEACL of "fred" simply deletes the identifier "fred" from the
+ ACL; it does not affect any rights that the user "fred" may get from
+ another entry in the ACL, in particular it doesn't affect rights
+ granted to the identifier "-fred".
+
+
+
+Melnikov Standards Track [Page 4]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ Server implementations are not required to support "negative right"
+ identifiers.
+
+2.1. Standard Rights
+
+ The currently defined standard rights are (note that the list below
+ doesn't list all commands that use a particular right):
+
+ l - lookup (mailbox is visible to LIST/LSUB commands, SUBSCRIBE
+ mailbox)
+ r - read (SELECT the mailbox, perform STATUS)
+ s - keep seen/unseen information across sessions (set or clear
+ \SEEN flag via STORE, also set \SEEN during APPEND/COPY/
+ FETCH BODY[...])
+ w - write (set or clear flags other than \SEEN and \DELETED via
+ STORE, also set them during APPEND/COPY)
+ i - insert (perform APPEND, COPY into mailbox)
+ p - post (send mail to submission address for mailbox,
+ not enforced by IMAP4 itself)
+ k - create mailboxes (CREATE new sub-mailboxes in any
+ implementation-defined hierarchy, parent mailbox for the new
+ mailbox name in RENAME)
+ x - delete mailbox (DELETE mailbox, old mailbox name in RENAME)
+ t - delete messages (set or clear \DELETED flag via STORE, set
+ \DELETED flag during APPEND/COPY)
+ e - perform EXPUNGE and expunge as a part of CLOSE
+ a - administer (perform SETACL/DELETEACL/GETACL/LISTRIGHTS)
+
+2.1.1. Obsolete Rights
+
+ Due to ambiguity in RFC 2086, some existing RFC 2086 server
+ implementations use the "c" right to control the DELETE command.
+ Others chose to use the "d" right to control the DELETE command. For
+ the former group, let's define the "create" right as union of the "k"
+ and "x" rights, and the "delete" right as union of the "e" and "t"
+ rights. For the latter group, let's define the "create" rights as a
+ synonym to the "k" right, and the "delete" right as union of the "e",
+ "t", and "x" rights.
+
+ For compatibility with RFC 2086, this section defines two virtual
+ rights "d" and "c".
+
+ If a client includes the "d" right in a rights list, then it MUST be
+ treated as if the client had included every member of the "delete"
+ right. (It is not an error for a client to specify both the "d"
+ right and one or more members of the "delete" right, but the effect
+ is no different than if just the "d" right or all members of the
+ "delete" right had been specified.)
+
+
+
+Melnikov Standards Track [Page 5]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ When any of the "delete" member rights is set in a list of rights,
+ the server MUST also include the "d" right when returning the list in
+ a MYRIGHTS or ACL response. This is to enable older clients
+ conforming to RFC 2086 to work with newer servers. (*)
+
+ Example: C: A001 SeTacl INBOX/Drafts David lrswida
+ S: A001 OK Setacl complete
+
+ The client has specified the "d" right in the SETACL command above
+ and it expands to "et" on the server:
+
+ C: A002 getacl INBOX/Drafts
+ S: * ACL INBOX Fred rwipslxcetda David lrswideta
+ S: A002 OK Getacl complete
+
+ If the identifier specified in the LISTRIGHTS command can be granted
+ any of the "delete" member rights on a mailbox, then the server MUST
+ include the "d" right in the corresponding LISTRIGHTS response. (*)
+ If the member rights aren't tied to non-member rights, then the "d"
+ right is returned by itself in the LISTRIGHTS response. If any of
+ the member rights needs to be tied to one (or more) non-member right,
+ then the "d" right and all of the member rights need to be tied to
+ the same non-member right(s) (**).
+
+ If a client includes the "c" right in a rights list, then it MUST be
+ treated as if the client had included every member of the "create"
+ right. (It is not an error for a client to specify both the "c"
+ right and one or more members of the "create" right, but the effect
+ is no different than if just the "c" right or all members of the
+ "create" right had been specified.)
+
+ When any of the "create" member rights is set in a list of rights,
+ the server MUST also include the "c" right when returning the list in
+ a MYRIGHTS or ACL response. This is to enable older clients
+ conforming to RFC 2086 to work with newer servers. (*)
+
+ Example: C: A003 Setacl INBOX/Drafts Byron lrswikda
+ S: A001 OK Setacl complete
+ C: A002 getAcl INBOX/Drafts
+ S: * ACL INBOX Fred rwipslxcetda Byron lrswikcdeta
+ S: A002 OK Getacl complete
+
+ The client has specified the "d" right in the SETACL command above
+ and it expands to "et" on the server: As the client has specified the
+ "k" right (which is a member of the "c" right), the server also
+ returns the "c" right.
+
+
+
+
+
+Melnikov Standards Track [Page 6]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ If the identifier specified in the LISTRIGHTS command can be granted
+ any of the "create" member rights on a mailbox, then the server MUST
+ include the "c" right in the corresponding LISTRIGHTS response. (*)
+ If the member rights aren't tied to non-member rights, then the "c"
+ right is returned by itself in the LISTRIGHTS response. If any of
+ the member rights needs to be tied to one (or more) non-member right,
+ then the "c" right and all of the member rights need to be tied to
+ the same non-member right(s) (**).
+
+ Example: The server that ties the rights as follows:
+
+ lr s w i p k x t
+
+ and c=k
+
+ will return:
+
+ S: * LISTRIGHTS archive/imap anyone ""
+ lr s w i p k x t c d
+
+ Example: The server that ties the rights as follows:
+
+ lr s w i p k xte
+
+ and c=k
+
+ will return:
+
+ S: * LISTRIGHTS archive/imap anyone ""
+ lr s w i p k xte c d
+
+ Example: The server that ties the rights as follows:
+
+ lr s w i p k x te
+
+ and c=k
+
+ will return:
+
+ S: * LISTRIGHTS archive/imap anyone ""
+ lr s w i p k c x te d
+
+ Example: The server that ties the rights as follows:
+
+ lr swte i p k x
+
+ and c=kx
+
+
+
+
+Melnikov Standards Track [Page 7]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ will return:
+
+ S: * LISTRIGHTS archive/imap anyone ""
+ lr swted i p k x c
+
+ (*) Clients conforming to this document MUST ignore the virtual "d"
+ and "c" rights in MYRIGHTS, ACL, and LISTRIGHTS responses.
+
+ (**) The IMAPEXT Working Group has debated this issue in great length
+ and after reviewing existing ACL implementations concluded that
+ this is a reasonable restriction.
+
+2.2. Rights Defined in RFC 2086
+
+ The "RIGHTS=" capability MUST NOT include any of the rights defined
+ in RFC 2086: "l", "r", "s", "w", "i", "p", "a", "c", "d", and the
+ digits ("0" .. "9").
+
+3. Access control management commands and responses
+
+ Servers, when processing a command that has an identifier as a
+ parameter (i.e., any of SETACL, DELETEACL, and LISTRIGHTS commands),
+ SHOULD first prepare the received identifier using "SASLprep" profile
+ [SASLprep] of the "stringprep" algorithm [Stringprep]. If the
+ preparation of the identifier fails or results in an empty string,
+ the server MUST refuse to perform the command with a BAD response.
+ Note that Section 6 recommends additional identifier's verification
+ steps.
+
+3.1. SETACL Command
+
+ Arguments: mailbox name
+ identifier
+ access right modification
+
+ Data: no specific data for this command
+
+ Result: OK - setacl completed
+ NO - setacl failure: can't set acl
+ BAD - arguments invalid
+
+ The SETACL command changes the access control list on the specified
+ mailbox so that the specified identifier is granted permissions as
+ specified in the third argument.
+
+ The third argument is a string containing an optional plus ("+") or
+ minus ("-") prefix, followed by zero or more rights characters. If
+ the string starts with a plus, the following rights are added to any
+
+
+
+Melnikov Standards Track [Page 8]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ existing rights for the identifier. If the string starts with a
+ minus, the following rights are removed from any existing rights for
+ the identifier. If the string does not start with a plus or minus,
+ the rights replace any existing rights for the identifier.
+
+ Note that an unrecognized right MUST cause the command to return the
+ BAD response. In particular, the server MUST NOT silently ignore
+ unrecognized rights.
+
+ Example: C: A001 GETACL INBOX/Drafts
+ S: * ACL INBOX/Drafts Fred rwipslxetad Chris lrswi
+ S: A001 OK Getacl complete
+ C: A002 SETACL INBOX/Drafts Chris +cda
+ S: A002 OK Setacl complete
+ C: A003 GETACL INBOX/Drafts
+ S: * ACL INBOX/Drafts Fred rwipslxetad Chris lrswicdakxet
+ S: A003 OK Getacl complete
+
+
+ C: A035 SETACL INBOX/Drafts John lrQswicda
+ S: A035 BAD Uppercase rights are not allowed
+
+
+ C: A036 SETACL INBOX/Drafts John lrqswicda
+ S: A036 BAD The q right is not supported
+
+3.2. DELETEACL Command
+
+ Arguments: mailbox name
+ identifier
+
+ Data: no specific data for this command
+
+ Result: OK - deleteacl completed
+ NO - deleteacl failure: can't delete acl
+ BAD - arguments invalid
+
+ The DELETEACL command removes any <identifier,rights> pair for the
+ specified identifier from the access control list for the specified
+ mailbox.
+
+ Example: C: B001 getacl INBOX
+ S: * ACL INBOX Fred rwipslxetad -Fred wetd $team w
+ S: B001 OK Getacl complete
+ C: B002 DeleteAcl INBOX Fred
+ S: B002 OK Deleteacl complete
+
+
+
+
+
+Melnikov Standards Track [Page 9]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ C: B003 GETACL INBOX
+ S: * ACL INBOX -Fred wetd $team w
+ S: B003 OK Getacl complete
+
+3.3. GETACL Command
+
+ Arguments: mailbox name
+
+ Data: untagged responses: ACL
+
+ Result: OK - getacl completed
+ NO - getacl failure: can't get acl
+ BAD - arguments invalid
+
+ The GETACL command returns the access control list for mailbox in an
+ untagged ACL response.
+
+ Some implementations MAY permit multiple forms of an identifier to
+ reference the same IMAP account. Usually, such implementations will
+ have a canonical form that is stored internally. An ACL response
+ caused by a GETACL command MAY include a canonicalized form of the
+ identifier that might be different from the one used in the
+ corresponding SETACL command.
+
+ Example: C: A002 GETACL INBOX
+ S: * ACL INBOX Fred rwipsldexta
+ S: A002 OK Getacl complete
+
+3.4. LISTRIGHTS Command
+
+ Arguments: mailbox name
+ identifier
+
+ Data: untagged responses: LISTRIGHTS
+
+ Result: OK - listrights completed
+ NO - listrights failure: can't get rights list
+ BAD - arguments invalid
+
+ The LISTRIGHTS command takes a mailbox name and an identifier and
+ returns information about what rights can be granted to the
+ identifier in the ACL for the mailbox.
+
+ Some implementations MAY permit multiple forms of an identifier to
+ reference the same IMAP account. Usually, such implementations will
+ have a canonical form that is stored internally. A LISTRIGHTS
+
+
+
+
+
+Melnikov Standards Track [Page 10]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ response caused by a LISTRIGHTS command MUST always return the same
+ form of an identifier as specified by the client. This is to allow
+ the client to correlate the response with the command.
+
+ Example: C: a001 LISTRIGHTS ~/Mail/saved smith
+ S: * LISTRIGHTS ~/Mail/saved smith la r swicdkxte
+ S: a001 OK Listrights completed
+
+ Example: C: a005 listrights archive/imap anyone
+ S: * LISTRIGHTS archive.imap anyone ""
+ l r s w i p k x t e c d a 0 1 2 3 4 5 6 7 8 9
+ S: a005 Listrights successful
+
+3.5. MYRIGHTS Command
+
+ Arguments: mailbox name
+
+ Data: untagged responses: MYRIGHTS
+
+ Result: OK - myrights completed
+ NO - myrights failure: can't get rights
+ BAD - arguments invalid
+
+ The MYRIGHTS command returns the set of rights that the user has to
+ mailbox in an untagged MYRIGHTS reply.
+
+ Example: C: A003 MYRIGHTS INBOX
+ S: * MYRIGHTS INBOX rwiptsldaex
+ S: A003 OK Myrights complete
+
+3.6. ACL Response
+
+ Data: mailbox name
+ zero or more identifier rights pairs
+
+ The ACL response occurs as a result of a GETACL command. The first
+ string is the mailbox name for which this ACL applies. This is
+ followed by zero or more pairs of strings; each pair contains the
+ identifier for which the entry applies followed by the set of rights
+ that the identifier has.
+
+ Section 2.1.1 details additional server requirements related to
+ handling of the virtual "d" and "c" rights.
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 11]
+
+RFC 4314 IMAP ACL December 2005
+
+
+3.7. LISTRIGHTS Response
+
+ Data: mailbox name
+ identifier
+ required rights
+ list of optional rights
+
+ The LISTRIGHTS response occurs as a result of a LISTRIGHTS command.
+ The first two strings are the mailbox name and identifier for which
+ this rights list applies. Following the identifier is a string
+ containing the (possibly empty) set of rights the identifier will
+ always be granted in the mailbox.
+
+ Following this are zero or more strings each containing a set of
+ rights the identifier can be granted in the mailbox. Rights
+ mentioned in the same string are tied together. The server MUST
+ either grant all tied rights to the identifier in the mailbox or
+ grant none. Section 2.1.1 details additional server requirements
+ related to handling of the virtual "d" and "c" rights.
+
+ The same right MUST NOT be listed more than once in the LISTRIGHTS
+ command.
+
+3.8. MYRIGHTS Response
+
+ Data: mailbox name
+ rights
+
+ The MYRIGHTS response occurs as a result of a MYRIGHTS command. The
+ first string is the mailbox name for which these rights apply. The
+ second string is the set of rights that the client has.
+
+ Section 2.1.1 details additional server requirements related to
+ handling of the virtual "d" and "c" rights.
+
+4. Rights Required to Perform Different IMAP4rev1 Commands
+
+ Before executing a command, an ACL-compliant server MUST check which
+ rights are required to perform it. This section groups command by
+ functions they perform and list the rights required. It also gives
+ the detailed description of any special processing required.
+
+ For the purpose of this section the UID counterpart of a command is
+ considered to be the same command, e.g., both UID COPY and COPY
+ commands require the same set of rights.
+
+
+
+
+
+
+Melnikov Standards Track [Page 12]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ The table below summarizes different rights or their combinations
+ that are required in order to perform different IMAP operations. As
+ it is not always possible to express complex right checking and
+ interactions, the description after the table should be used as the
+ primary reference.
+
+ +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+ |Operations\Rights | l | r | s | w | i | k | x | t | e | a |Any|Non|
+ +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+ | commands in authenticated state |
+ +-------------------------------------------------------------------+
+ | LIST | + | | | | | | | | | | | |
+ | SUBSCRIBE | * | | | | | | | | | | | * |
+ | UNSUBSCRIBE | | | | | | | | | | | | + |
+ | LSUB | * | | | | | | | | | | | * |
+ |CREATE (for parent)| | | | | | + | | | | | | |
+ | DELETE | | ? | | | | | + | ? | ? | | | |
+ | RENAME | | | | | | + | + | | | | | |
+ | SELECT/EXAMINE | | + | | | | | | | | | | |
+ | STATUS | | + | | | | | | | | | | |
+ | SETACL/DELETEACL | | | | | | | | | | + | | |
+ | GETACL/LISTRIGHTS | | | | | | | | | | + | | |
+ | MYRIGHTS | | | | | | | | | | | + | |
+ | APPEND | | | ? | ? | + | | | ? | | | | |
+ +-------------------------------------------------------------------+
+ | commands in selected state |
+ +-------------------------------------------------------------------+
+ | COPY | | | ? | ? | + | | | ? | | | | |
+ | EXPUNGE | | | | | | | | | + | | | |
+ | CLOSE | | | | | | | | | ? | | | |
+ | FETCH | | | ? | | | | | | | | | |
+ | STORE flags | | | ? | ? | | | | ? | | | | |
+ +-------------------+---+---+---+---+---+---+---+---+---+---+---+---+
+
+ Note: for all commands in the selected state, the "r" is implied,
+ because it is required to SELECT/EXAMINE a mailbox. Servers are not
+ required to check presence of the "r" right once a mailbox is
+ successfully selected.
+
+ Legend:
+ + - The right is required
+ * - Only one of the rights marked with * is required
+ (see description below)
+ ? - The right is OPTIONAL (see description below)
+ "Any" - at least one of the "l", "r", "i", "k", "x", "a" rights is
+ required
+ "Non" - No rights required to perform the command
+
+
+
+
+Melnikov Standards Track [Page 13]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ Listing and subscribing/unsubscribing mailboxes:
+ LIST - "l" right is required. However, unlike other commands
+ (e.g., SELECT) the server MUST NOT return a NO response if it
+ can't list a mailbox.
+ Note that if the user has "l" right to a mailbox "A/B", but not to
+ its parent mailbox "A", the LIST command should behave as if the
+ mailbox "A" doesn't exist, for example:
+
+ C: A777 LIST "" *
+ S: * LIST (\NoInferiors) "/" "A/B"
+ S: * LIST () "/" "C"
+ S: * LIST (\NoInferiors) "/" "C/D"
+ S: A777 OK LIST completed
+
+
+ SUBSCRIBE - "l" right is required only if the server checks for
+ mailbox existence when performing SUBSCRIBE.
+
+ UNSUBSCRIBE - no rights required to perform this operation.
+
+ LSUB - "l" right is required only if the server checks for mailbox
+ existence when performing SUBSCRIBE. However, unlike other
+ commands (e.g., SELECT) the server MUST NOT return a NO response
+ if it can't list a subscribed mailbox.
+
+ Mailbox management:
+ CREATE - "k" right on a nearest existing parent mailbox. When a
+ new mailbox is created, it SHOULD inherit the ACL from the parent
+ mailbox (if one exists) in the defined hierarchy.
+
+ DELETE - "x" right on the mailbox. Note that some servers don't
+ allow to delete a non-empty mailbox. If this is the case, the
+ user would also need "r", "e", and "t" rights, in order to open
+ the mailbox and empty it.
+
+ The DELETE command MUST delete the ACL associated with the deleted
+ mailbox.
+
+ RENAME - Moving a mailbox from one parent to another requires the
+ "x" right on the mailbox itself and the "k" right for the new
+ parent. For example, if the user wants to rename the mailbox
+ named "A/B/C" to "D/E", the user must have the "x" right for the
+ mailbox "A/B/C" and the "k" right for the mailbox "D".
+ The RENAME command SHOULD NOT change the ACLs on the renamed
+ mailbox and submailboxes.
+
+
+
+
+
+
+Melnikov Standards Track [Page 14]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ Copying or appending messages:
+ Before performing a COPY/APPEND command, the server MUST check if
+ the user has "i" right for the target mailbox. If the user
+ doesn't have "i" right, the operation fails. Otherwise for each
+ copied/appended message the server MUST check if the user has
+ "t" right - when the message has \Deleted flag set
+ "s" right - when the message has \Seen flag set
+ "w" right - for all other message flags.
+ Only when the user has a particular right are the corresponding
+ flags stored for the newly created message. The server MUST NOT
+ fail a COPY/APPEND if the user has no rights to set a particular
+ flag.
+
+ Example: C: A003 MYRIGHTS TargetMailbox
+ S: * MYRIGHTS TargetMailbox rwis
+ S: A003 OK Myrights complete
+
+ C: A004 FETCH 1:3 (FLAGS)
+ S: * 1 FETCH (FLAGS (\Draft \Deleted)
+ S: * 2 FETCH (FLAGS (\Answered)
+ S: * 3 FETCH (FLAGS ($Forwarded \Seen)
+ S: A004 OK Fetch Completed
+
+ C: A005 COPY 1:3 TargetMailbox
+ S: A005 OK Copy completed
+
+ C: A006 SELECT TargetMailbox
+ ...
+ S: A006 Select Completed
+
+ Let's assume that the copied messages received message numbers
+ 77:79.
+
+ C: A007 FETCH 77:79 (FLAGS)
+ S: * 77 FETCH (FLAGS (\Draft))
+ S: * 78 FETCH (FLAGS (\Answered))
+ S: * 79 FETCH (FLAGS ($Forwarded \Seen))
+ S: A007 OK Fetch Completed
+
+ \Deleted flag was lost on COPY, as the user has no "t" right in
+ the target mailbox.
+ If the MYRIGHTS command with the tag A003 would have returned:
+
+ S: * MYRIGHTS TargetMailbox rsti
+
+ the response from the FETCH with the tag A007 would have been:
+
+ C: A007 FETCH 77:79 (FLAGS)
+
+
+
+Melnikov Standards Track [Page 15]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ S: * 77 FETCH (FLAGS (\Deleted))
+ S: * 78 FETCH (FLAGS ())
+ S: * 79 FETCH (FLAGS (\Seen))
+ S: A007 OK Fetch Completed
+
+ In the latter case, \Answered, $Forwarded, and \Draft flags were
+ lost on COPY, as the user has no "w" right in the target mailbox.
+
+ Expunging the selected mailbox:
+ EXPUNGE - "e" right on the selected mailbox.
+
+ CLOSE - "e" right on the selected mailbox. If the server is
+ unable to expunge the mailbox because the user doesn't have the
+ "e" right, the server MUST ignore the expunge request, close the
+ mailbox, and return the tagged OK response.
+
+ Fetch information about a mailbox and its messages:
+ SELECT/EXAMINE/STATUS - "r" right on the mailbox.
+
+ FETCH - A FETCH request that implies setting \Seen flag MUST NOT
+ set it, if the current user doesn't have "s" right.
+
+ Changing flags:
+ STORE - the server MUST check if the user has
+ "t" right - when the user modifies \Deleted flag
+ "s" right - when the user modifies \Seen flag
+ "w" right - for all other message flags.
+ STORE operation SHOULD NOT fail if the user has rights to modify
+ at least one flag specified in the STORE, as the tagged NO
+ response to a STORE command is not handled very well by deployed
+ clients.
+
+ Changing ACLs:
+ SETACL/DELETEACL - "a" right on the mailbox.
+
+ Reading ACLs:
+ GETACL - "a" right on the mailbox.
+
+ MYRIGHTS - any of the following rights is required to perform the
+ operation: "l", "r", "i", "k", "x", "a".
+
+ LISTRIGHTS - "a" right on the mailbox.
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 16]
+
+RFC 4314 IMAP ACL December 2005
+
+
+5. Other Considerations
+
+5.1. Additional Requirements and Implementation Notes
+
+5.1.1. Servers
+
+ This document defines an additional capability that is used to
+ announce the list of extra rights (excluding the ones defined in RFC
+ 2086) supported by the server. The set of rights MUST include "t",
+ "e", "x", and "k". Note that the extra rights can appear in any
+ order.
+
+ Example: C: 1 capability
+ S: * CAPABILITY IMAP4REV1 STARTTLS LITERAL+
+ ACL RIGHTS=texk
+ S: 1 OK completed
+
+ Any server implementing an ACL extension MUST accurately reflect the
+ current user's rights in FLAGS and PERMANENTFLAGS responses.
+
+ Example: C: A142 SELECT INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Seen \Answered \Flagged \*)] L
+ S: A142 OK [READ-WRITE] SELECT completed
+ C: A143 MYRIGHTS INBOX
+ S: * MYRIGHTS INBOX lrwis
+ S: A143 OK completed
+
+ Note that in order to get better performance the client MAY pipeline
+ SELECT and MYRIGHTS commands:
+
+ C: A142 SELECT INBOX
+ C: A143 MYRIGHTS INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Seen \Answered \Flagged \*)] L
+ S: A142 OK [READ-WRITE] SELECT completed
+ S: * MYRIGHTS INBOX lrwis
+ S: A143 OK completed
+
+
+
+Melnikov Standards Track [Page 17]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ Servers MAY cache the rights a user has on a mailbox when the mailbox
+ is selected, so that if a client's rights on a mailbox are changed
+ with SETACL or DELETEACL, commands specific to the selected state
+ (e.g., STORE, EXPUNGE) might not reflect the changed rights until the
+ mailbox is re-selected. If the server checks the rights on each
+ command, then it SHOULD send FLAGS and PERMANENTFLAGS responses if
+ they have changed. If such server detects that the user no longer
+ has read access to the mailbox, it MAY send an untagged BYE response
+ and close connection. It MAY also refuse to execute all commands
+ specific to the selected state until the mailbox is closed; however,
+ server implementors should note that most clients don't handle NO
+ responses very well.
+
+ An ACL server MAY modify one or more ACLs for one or more identifiers
+ as a side effect of modifying the ACL specified in a
+ SETACL/DELETEACL. If the server does that, it MUST send untagged ACL
+ response(s) to notify the client about the changes made.
+
+ An ACL server implementation MUST treat received ACL modification
+ commands as a possible ambiguity with respect to subsequent commands
+ affected by the ACL, as described in Section 5.5 of [IMAP4]. Hence a
+ pipeline SETACL + MYRIGHTS is an ambiguity with respect to the
+ server, meaning that the server must execute the SETACL command to
+ completion before the MYRIGHTS. However, clients are permitted to
+ send such a pipeline.
+
+5.1.2. Clients
+
+ The following requirement is put on clients in order to allow for
+ future extensibility. A client implementation that allows a user to
+ read and update ACLs MUST preserve unrecognized rights that it
+ doesn't allow the user to change. That is, if the client
+
+ 1) can read ACLs
+ and
+ 2) can update ACLs
+ but
+ 3) doesn't allow the user to change the rights the client doesn't
+ recognize, then it MUST preserve unrecognized rights.
+
+ Otherwise the client could risk unintentionally removing permissions
+ it doesn't understand.
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 18]
+
+RFC 4314 IMAP ACL December 2005
+
+
+5.2. Mapping of ACL Rights to READ-WRITE and READ-ONLY Response Codes
+
+ A particular ACL server implementation MAY allow "shared multiuser
+ access" to some mailboxes. "Shared multiuser access" to a mailbox
+ means that multiple different users are able to access the same
+ mailbox, if they have proper access rights. "Shared multiuser
+ access" to the mailbox doesn't mean that the ACL for the mailbox is
+ currently set to allow access by multiple users. Let's denote a
+ "shared multiuser write access" as a "shared multiuser access" when a
+ user can be granted flag modification rights (any of "w", "s", or
+ "t").
+
+ Section 4 describes which rights are required for modifying different
+ flags.
+
+ If the ACL server implements some flags as shared for a mailbox
+ (i.e., the ACL for the mailbox MAY be set up so that changes to those
+ flags are visible to another user), let's call the set of rights
+ associated with these flags (as described in Section 4) for that
+ mailbox collectively as "shared flag rights". Note that the "shared
+ flag rights" set MAY be different for different mailboxes.
+
+ If the server doesn't support "shared multiuser write access" to a
+ mailbox or doesn't implement shared flags on the mailbox, "shared
+ flag rights" for the mailbox is defined to be the empty set.
+
+ Example 1: Mailbox "banan" allows "shared multiuser write access" and
+ implements flags \Deleted, \Answered, and $MDNSent as
+ shared flags. "Shared flag rights" for the mailbox "banan"
+ is a set containing flags "t" (because system flag
+ \Deleted requires "t" right) and "w" (because both
+ \Answered and $MDNSent require "w" right).
+
+ Example 2: Mailbox "apple" allows "shared multiuser write access" and
+ implements \Seen system flag as shared flag. "Shared flag
+ rights" for the mailbox "apple" contains "s" right
+ because system flag \Seen requires "s" right.
+
+ Example 3: Mailbox "pear" allows "shared multiuser write access" and
+ implements flags \Seen, \Draft as shared flags. "Shared
+ flag rights" for the mailbox "apple" is a set containing
+ flags "s" (because system flag \Seen requires "s" right)
+ and "w" (because system flag \Draft requires "w" right).
+
+ The server MUST include a READ-ONLY response code in the tagged OK
+ response to a SELECT command if none of the following rights is
+ granted to the current user:
+
+
+
+
+Melnikov Standards Track [Page 19]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ "i", "e", and "shared flag rights"(***).
+
+ The server SHOULD include a READ-WRITE response code in the tagged OK
+ response if at least one of the "i", "e", or "shared flag
+ rights"(***) is granted to the current user.
+
+ (***) Note that a future extension to this document can extend the
+ list of rights that causes the server to return the READ-WRITE
+ response code.
+
+ Example 1 (continued): The user that has "lrs" rights for the mailbox
+ "banan". The server returns READ-ONLY
+ response code on SELECT, as none of "iewt"
+ rights is granted to the user.
+
+ Example 2 (continued): The user that has "rit" rights for the mailbox
+ "apple". The server returns READ-WRITE
+ response code on SELECT, as the user has "i"
+ right.
+
+ Example 3 (continued): The user that has "rset" rights for the
+ mailbox "pear". The server returns READ-WRITE
+ response code on SELECT, as the user has "e"
+ and "s" rights.
+
+6. Security Considerations
+
+ An implementation MUST make sure the ACL commands themselves do not
+ give information about mailboxes with appropriately restricted ACLs.
+ For example, when a user agent executes a GETACL command on a mailbox
+ that the user has no permission to LIST, the server would respond to
+ that request with the same error that would be used if the mailbox
+ did not exist, thus revealing no existence information, much less the
+ mailbox's ACL.
+
+ IMAP clients implementing ACL that are able to modify ACLs SHOULD
+ warn a user that wants to give full access (or even just the "a"
+ right) to the special identifier "anyone".
+
+ This document relies on [SASLprep] to describe steps required to
+ perform identifier canonicalization (preparation). The preparation
+ algorithm in SASLprep was specifically designed such that its output
+ is canonical, and it is well-formed. However, due to an anomaly
+ [PR29] in the specification of Unicode normalization, canonical
+ equivalence is not guaranteed for a select few character sequences.
+ Identifiers prepared with SASLprep can be stored and returned by an
+ ACL server. The anomaly affects ACL manipulation and evaluation of
+ identifiers containing the selected character sequences. These
+
+
+
+Melnikov Standards Track [Page 20]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ sequences, however, do not appear in well-formed text. In order to
+ address this problem, an ACL server MAY reject identifiers containing
+ sequences described in [PR29] by sending the tagged BAD response.
+ This is in addition to the requirement to reject identifiers that
+ fail SASLprep preparation as described in Section 3.
+
+ Other security considerations described in [IMAP4] are relevant to
+ this document. In particular, ACL information is sent in the clear
+ over the network unless confidentiality protection is negotiated.
+
+ This can be accomplished either by the use of STARTTLS, negotiated
+ privacy protection in the AUTHENTICATE command, or some other
+ protection mechanism.
+
+7. Formal Syntax
+
+ Formal syntax is defined using ABNF [ABNF], extending the ABNF rules
+ in Section 9 of [IMAP4]. Elements not defined here can be found in
+ [ABNF] and [IMAP4].
+
+ Except as noted otherwise, all alphabetic characters are case
+ insensitive. The use of uppercase or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ LOWER-ALPHA = %x61-7A ;; a-z
+
+ acl-data = "ACL" SP mailbox *(SP identifier SP
+ rights)
+
+ capability =/ rights-capa
+ ;;capability is defined in [IMAP4]
+
+ command-auth =/ setacl / deleteacl / getacl /
+ listrights / myrights
+ ;;command-auth is defined in [IMAP4]
+
+ deleteacl = "DELETEACL" SP mailbox SP identifier
+
+ getacl = "GETACL" SP mailbox
+
+ identifier = astring
+
+ listrights = "LISTRIGHTS" SP mailbox SP identifier
+
+ listrights-data = "LISTRIGHTS" SP mailbox SP identifier
+ SP rights *(SP rights)
+
+
+
+
+Melnikov Standards Track [Page 21]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ mailbox-data =/ acl-data / listrights-data / myrights-data
+ ;;mailbox-data is defined in [IMAP4]
+
+ mod-rights = astring
+ ;; +rights to add, -rights to remove
+ ;; rights to replace
+
+ myrights = "MYRIGHTS" SP mailbox
+
+ myrights-data = "MYRIGHTS" SP mailbox SP rights
+
+ new-rights = 1*LOWER-ALPHA
+ ;; MUST include "t", "e", "x", and "k".
+ ;; MUST NOT include standard rights listed
+ ;; in section 2.2
+
+ rights = astring
+ ;; only lowercase ASCII letters and digits
+ ;; are allowed.
+
+ rights-capa = "RIGHTS=" new-rights
+ ;; RIGHTS=... capability
+
+ setacl = "SETACL" SP mailbox SP identifier
+ SP mod-rights
+
+8. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards-track or
+ IESG-approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ This document defines the RIGHTS= IMAP capability. IANA has added
+ this capability to the registry.
+
+9. Internationalization Considerations
+
+ Section 3 states requirements on servers regarding
+ internationalization of identifiers.
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 22]
+
+RFC 4314 IMAP ACL December 2005
+
+
+Appendix A. Changes since RFC 2086
+
+ 1. Changed the charset of "identifier" from US-ASCII to UTF-8.
+ 2. Specified that mailbox deletion is controlled by the "x" right
+ and EXPUNGE is controlled by the "e" right.
+ 3. Added the "t" right that controls STORE \Deleted. Redefined the
+ "d" right to be a macro for "e", "t", and possibly "x".
+ 4. Added the "k" right that controls CREATE. Redefined the "c"
+ right to be a macro for "k" and possibly "x".
+ 5. Specified that the "a" right also controls DELETEACL.
+ 6. Specified that the "r" right also controls STATUS.
+ 7. Removed the requirement to check the "r" right for CHECK, SEARCH
+ and FETCH, as this is required for SELECT/EXAMINE to be
+ successful.
+ 8. LISTRIGHTS requires the "a" right on the mailbox (same as
+ SETACL).
+ 9. Deleted "PARTIAL", this is a deprecated feature of RFC 1730.
+ 10. Specified that the "w" right controls setting flags other than
+ \Seen and \Deleted on APPEND. Also specified that the "s" right
+ controls the \Seen flag and that the "t" right controls the
+ \Deleted flag.
+ 11. Specified that SUBSCRIBE is NOT allowed with the "r" right.
+ 12. Specified that the "l" right controls SUBSCRIBE.
+ 13. GETACL is NOT allowed with the "r" right, even though there are
+ several implementations that allows that. If a user only has
+ "r" right, GETACL can disclose information about identifiers
+ existing on the mail system.
+ 14. Clarified that RENAME requires the "k" right for the new parent
+ and the "x" right for the old name.
+ 15. Added new section that describes which rights are required
+ and/or checked when performing various IMAP commands.
+ 16. Added mail client security considerations when dealing with
+ special identifier "anyone".
+ 17. Clarified that negative rights are not the same as DELETEACL.
+ 18. Added "Compatibility with RFC 2086" section.
+ 19. Added section about mapping of ACL rights to READ-WRITE and
+ READ-ONLY response codes.
+ 20. Changed BNF to ABNF.
+ 21. Added "Implementation Notes" section.
+ 22. Updated "References" section.
+ 23. Added more examples.
+ 24. Clarified when the virtual "c" and "d" rights are returned in
+ ACL, MYRIGHTS, and LISTRIGHTS responses.
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 23]
+
+RFC 4314 IMAP ACL December 2005
+
+
+Appendix B. Compatibility with RFC 2086
+
+ This non-normative section gives guidelines as to how an existing RFC
+ 2086 server implementation may be updated to comply with this
+ document.
+
+ This document splits the "d" right into several new different rights:
+ "t", "e", and possibly "x" (see Section 2.1.1 for more details). The
+ "d" right remains for backward-compatibility, but it is a virtual
+ right. There are two approaches for RFC 2086 server implementors to
+ handle the "d" right and the new rights that have replaced it:
+
+ a. Tie "t", "e" (and possibly "x) together - almost no changes.
+ b. Implement separate "x", "t" and "e". Return the "d" right in a
+ MYRIGHTS response or an ACL response containing ACL information
+ when any of the "t", "e" (and "x") is granted.
+
+ In a similar manner this document splits the "c" right into several
+ new different rights: "k" and possibly "x" (see Section 2.1.1 for
+ more details). The "c" right remains for backwards-compatibility but
+ it is a virtual right. Again, RFC 2086 server implementors can
+ choose to tie rights or to implement separate rights, as described
+ above.
+
+ Also check Sections 5.1.1 and 5.1.2, as well as Appendix A, to see
+ other changes required. Server implementors should check which
+ rights are required to invoke different IMAP4 commands as described
+ in Section 4.
+
+Appendix C. Known Deficiencies
+
+ This specification has some known deficiencies including:
+
+ 1. This is inadequate to provide complete read-write access to
+ mailboxes protected by Unix-style rights bits because there is no
+ equivalent to "chown" and "chgrp" commands nor is there a good
+ way to discover such limitations are present.
+ 2. Because this extension leaves the specific semantics of how
+ rights are combined by the server as implementation defined, the
+ ability to build a user-friendly interface is limited.
+ 3. Users, groups, and special identifiers (e.g., anyone) exist in
+ the same namespace.
+
+ The work-in-progress "ACL2" extension is intended to redesign this
+ extension to address these deficiencies without the constraint of
+ backward-compatibility and may eventually supercede this facility.
+
+
+
+
+
+Melnikov Standards Track [Page 24]
+
+RFC 4314 IMAP ACL December 2005
+
+
+ However, RFC 2086 is deployed in multiple implementations so this
+ intermediate step, which fixes the straightforward deficiencies in a
+ backward-compatible fashion, is considered worthwhile.
+
+Appendix D. Acknowledgements
+
+ This document is a revision of RFC 2086 written by John G. Myers.
+
+ Editor appreciates comments received from Mark Crispin, Chris Newman,
+ Cyrus Daboo, John G. Myers, Dave Cridland, Ken Murchison, Steve Hole,
+ Vladimir Butenko, Larry Greenfield, Robert Siemborski, Harrie
+ Hazewinkel, Philip Guenther, Brian Candler, Curtis King, Lyndon
+ Nerenberg, Lisa Dusseault, Arnt Gulbrandsen, and other participants
+ of the IMAPEXT working group.
+
+Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [Stringprep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [SASLprep] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+Informative References
+
+ [RFC2086] Myers, J., "IMAP4 ACL extension", RFC 2086,
+ January 1997.
+
+ [PR29] "Public Review Issue #29: Normalization Issue",
+ February 2004,
+ <http://www.unicode.org/review/pr-29.html>.
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 25]
+
+RFC 4314 IMAP ACL December 2005
+
+
+Author's Address
+
+ Alexey Melnikov
+ Isode Ltd.
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ GB
+
+ EMail: alexey.melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 26]
+
+RFC 4314 IMAP ACL December 2005
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2005).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at ietf-
+ ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 27]
+
diff --git a/imap/docs/rfc/rfc4315.txt b/imap/docs/rfc/rfc4315.txt
new file mode 100644
index 00000000..c026f422
--- /dev/null
+++ b/imap/docs/rfc/rfc4315.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 4315 December 2005
+Obsoletes: 2359
+Category: Standards Track
+
+
+ Internet Message Access Protocol (IMAP) - UIDPLUS extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2005).
+
+Abstract
+
+ The UIDPLUS extension of the Internet Message Access Protocol (IMAP)
+ provides a set of features intended to reduce the amount of time and
+ resources used by some client operations. The features in UIDPLUS
+ are primarily intended for disconnected-use clients.
+
+1. Introduction and Overview
+
+ The UIDPLUS extension is present in any IMAP server implementation
+ that returns "UIDPLUS" as one of the supported capabilities to the
+ CAPABILITY command.
+
+ The UIDPLUS extension defines an additional command. In addition,
+ this document recommends new status response codes in IMAP that
+ SHOULD be returned by all server implementations, regardless of
+ whether or not the UIDPLUS extension is implemented.
+
+ The added facilities of the features in UIDPLUS are optimizations;
+ clients can provide equivalent functionality, albeit less
+ efficiently, by using facilities in the base protocol.
+
+1.1. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
+ be interpreted as described in [KEYWORDS].
+
+ A "UID set" is similar to the [IMAP] sequence set; however, the "*"
+ value for a sequence number is not permitted.
+
+2. Additional Commands
+
+ The following command definition is an extension to [IMAP] section
+ 6.4.
+
+2.1. UID EXPUNGE Command
+
+ Arguments: sequence set
+
+ Data: untagged responses: EXPUNGE
+
+ Result: OK - expunge completed
+ NO - expunge failure (e.g., permission denied)
+ BAD - command unknown or arguments invalid
+
+ The UID EXPUNGE command permanently removes all messages that both
+ have the \Deleted flag set and have a UID that is included in the
+ specified sequence set from the currently selected mailbox. If a
+ message either does not have the \Deleted flag set or has a UID
+ that is not included in the specified sequence set, it is not
+ affected.
+
+ This command is particularly useful for disconnected use clients.
+ By using UID EXPUNGE instead of EXPUNGE when resynchronizing with
+ the server, the client can ensure that it does not inadvertantly
+ remove any messages that have been marked as \Deleted by other
+ clients between the time that the client was last connected and
+ the time the client resynchronizes.
+
+ If the server does not support the UIDPLUS capability, the client
+ should fall back to using the STORE command to temporarily remove
+ the \Deleted flag from messages it does not want to remove, then
+ issuing the EXPUNGE command. Finally, the client should use the
+ STORE command to restore the \Deleted flag on the messages in
+ which it was temporarily removed.
+
+ Alternatively, the client may fall back to using just the EXPUNGE
+ command, risking the unintended removal of some messages.
+
+
+
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ Example: C: A003 UID EXPUNGE 3000:3002
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: A003 OK UID EXPUNGE completed
+
+3. Additional Response Codes
+
+ The following response codes are extensions to the response codes
+ defined in [IMAP] section 7.1. With limited exceptions, discussed
+ below, server implementations that advertise the UIDPLUS extension
+ SHOULD return these response codes.
+
+ In the case of a mailbox that has permissions set so that the client
+ can COPY or APPEND to the mailbox, but not SELECT or EXAMINE it, the
+ server SHOULD NOT send an APPENDUID or COPYUID response code as it
+ would disclose information about the mailbox.
+
+ In the case of a mailbox that has UIDNOTSTICKY status (as defined
+ below), the server MAY omit the APPENDUID or COPYUID response code as
+ it is not meaningful.
+
+ If the server does not return the APPENDUID or COPYUID response
+ codes, the client can discover this information by selecting the
+ destination mailbox. The location of messages placed in the
+ destination mailbox by COPY or APPEND can be determined by using
+ FETCH and/or SEARCH commands (e.g., for Message-ID or some unique
+ marker placed in the message in an APPEND).
+
+ APPENDUID
+
+ Followed by the UIDVALIDITY of the destination mailbox and the UID
+ assigned to the appended message in the destination mailbox,
+ indicates that the message has been appended to the destination
+ mailbox with that UID.
+
+ If the server also supports the [MULTIAPPEND] extension, and if
+ multiple messages were appended in the APPEND command, then the
+ second value is a UID set containing the UIDs assigned to the
+ appended messages, in the order they were transmitted in the
+ APPEND command. This UID set may not contain extraneous UIDs or
+ the symbol "*".
+
+ Note: the UID set form of the APPENDUID response code MUST NOT
+ be used if only a single message was appended. In particular,
+ a server MUST NOT send a range such as 123:123. This is
+ because a client that does not support [MULTIAPPEND] expects
+ only a single UID and not a UID set.
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ UIDs are assigned in strictly ascending order in the mailbox
+ (refer to [IMAP], section 2.3.1.1) and UID ranges are as in
+ [IMAP]; in particular, note that a range of 12:10 is exactly
+ equivalent to 10:12 and refers to the sequence 10,11,12.
+
+ This response code is returned in a tagged OK response to the
+ APPEND command.
+
+ COPYUID
+
+ Followed by the UIDVALIDITY of the destination mailbox, a UID set
+ containing the UIDs of the message(s) in the source mailbox that
+ were copied to the destination mailbox and containing the UIDs
+ assigned to the copied message(s) in the destination mailbox,
+ indicates that the message(s) have been copied to the destination
+ mailbox with the stated UID(s).
+
+ The source UID set is in the order the message(s) were copied; the
+ destination UID set corresponds to the source UID set and is in
+ the same order. Neither of the UID sets may contain extraneous
+ UIDs or the symbol "*".
+
+ UIDs are assigned in strictly ascending order in the mailbox
+ (refer to [IMAP], section 2.3.1.1) and UID ranges are as in
+ [IMAP]; in particular, note that a range of 12:10 is exactly
+ equivalent to 10:12 and refers to the sequence 10,11,12.
+
+ This response code is returned in a tagged OK response to the COPY
+ command.
+
+ UIDNOTSTICKY
+
+ The selected mailbox is supported by a mail store that does not
+ support persistent UIDs; that is, UIDVALIDITY will be different
+ each time the mailbox is selected. Consequently, APPEND or COPY
+ to this mailbox will not return an APPENDUID or COPYUID response
+ code.
+
+ This response code is returned in an untagged NO response to the
+ SELECT command.
+
+ Note: servers SHOULD NOT have any UIDNOTSTICKY mail stores.
+ This facility exists to support legacy mail stores in which it
+ is technically infeasible to support persistent UIDs. This
+ should be avoided when designing new mail stores.
+
+
+
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ Example: C: A003 APPEND saved-messages (\Seen) {297}
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@example.com>
+ C: Subject: afternoon meeting
+ C: To: mooch@example.com
+ C: Message-Id: <B27397-0100000@example.com>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK [APPENDUID 38505 3955] APPEND completed
+ C: A004 COPY 2:4 meeting
+ S: A004 OK [COPYUID 38505 304,319:320 3956:3958] Done
+ C: A005 UID COPY 305:310 meeting
+ S: A005 OK No matching messages, so nothing copied
+ C: A006 COPY 2 funny
+ S: A006 OK Done
+ C: A007 SELECT funny
+ S: * 1 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 1] Message 1 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] Validity session-only
+ S: * OK [UIDNEXT 2] Predicted next UID
+ S: * NO [UIDNOTSTICKY] Non-persistent UIDs
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen)] Limited
+ S: A007 OK [READ-WRITE] SELECT completed
+
+ In this example, A003 and A004 demonstrate successful appending and
+ copying to a mailbox that returns the UIDs assigned to the messages.
+ A005 is an example in which no messages were copied; this is because
+ in A003, we see that message 2 had UID 304, and message 3 had UID
+ 319; therefore, UIDs 305 through 310 do not exist (refer to section
+ 2.3.1.1 of [IMAP] for further explanation). A006 is an example of a
+ message being copied that did not return a COPYUID; and, as expected,
+ A007 shows that the mail store containing that mailbox does not
+ support persistent UIDs.
+
+4. Formal Syntax
+
+ Formal syntax is defined using ABNF [ABNF], which extends the ABNF
+ rules defined in [IMAP]. The IMAP4 ABNF should be imported before
+ attempting to validate these rules.
+
+ append-uid = uniqueid
+
+ capability =/ "UIDPLUS"
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ command-select =/ uid-expunge
+
+ resp-code-apnd = "APPENDUID" SP nz-number SP append-uid
+
+ resp-code-copy = "COPYUID" SP nz-number SP uid-set SP uid-set
+
+ resp-text-code =/ resp-code-apnd / resp-code-copy / "UIDNOTSTICKY"
+ ; incorporated before the expansion rule of
+ ; atom [SP 1*<any TEXT-CHAR except "]">]
+ ; that appears in [IMAP]
+
+ uid-expunge = "UID" SP "EXPUNGE" SP sequence-set
+
+ uid-set = (uniqueid / uid-range) *("," uid-set)
+
+ uid-range = (uniqueid ":" uniqueid)
+ ; two uniqueid values and all values
+ ; between these two regards of order.
+ ; Example: 2:4 and 4:2 are equivalent.
+
+ Servers that support [MULTIAPPEND] will have the following extension
+ to the above rules:
+
+ append-uid =/ uid-set
+ ; only permitted if client uses [MULTIAPPEND]
+ ; to append multiple messages.
+
+5. Security Considerations
+
+ The COPYUID and APPENDUID response codes return information about the
+ mailbox, which may be considered sensitive if the mailbox has
+ permissions set that permit the client to COPY or APPEND to the
+ mailbox, but not SELECT or EXAMINE it.
+
+ Consequently, these response codes SHOULD NOT be issued if the client
+ does not have access to SELECT or EXAMINE the mailbox.
+
+6. IANA Considerations
+
+ This document constitutes registration of the UIDPLUS capability in
+ the imap4-capabilities registry, replacing [RFC2359].
+
+7. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+ [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ MULTIAPPEND Extension", RFC 3502, March 2003.
+
+8. Informative References
+
+ [RFC2359] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June
+ 1998.
+
+9. Changes from RFC 2359
+
+ This document obsoletes [RFC2359]. However, it is based upon that
+ document, and takes substantial text from it (albeit with numerous
+ clarifications in wording).
+
+ [RFC2359] implied that a server must always return COPYUID/APPENDUID
+ data; thus suggesting that in such cases the server should return
+ arbitrary data if the destination mailbox did not support persistent
+ UIDs. This document adds the UIDNOTSTICKY response code to indicate
+ that a mailbox does not support persistent UIDs, and stipulates that
+ a UIDPLUS server does not return COPYUID/APPENDUID data when the COPY
+ (or APPEND) destination mailbox has UIDNOTSTICKY status.
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 7]
+
+RFC 4315 IMAP - UIDPLUS Extension December 2005
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2005).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at ietf-
+ ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+Crispin Standards Track [Page 8]
+
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+
+
+
+
+
+
+Network Working Group A. Melnikov, Ed.
+Request for Comments: 4422 Isode Limited
+Obsoletes: 2222 K. Zeilenga, Ed.
+Category: Standards Track OpenLDAP Foundation
+ June 2006
+
+
+ Simple Authentication and Security Layer (SASL)
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ The Simple Authentication and Security Layer (SASL) is a framework
+ for providing authentication and data security services in
+ connection-oriented protocols via replaceable mechanisms. It
+ provides a structured interface between protocols and mechanisms.
+ The resulting framework allows new protocols to reuse existing
+ mechanisms and allows old protocols to make use of new mechanisms.
+ The framework also provides a protocol for securing subsequent
+ protocol exchanges within a data security layer.
+
+ This document describes how a SASL mechanism is structured, describes
+ how protocols include support for SASL, and defines the protocol for
+ carrying a data security layer over a connection. In addition, this
+ document defines one SASL mechanism, the EXTERNAL mechanism.
+
+ This document obsoletes RFC 2222.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 1]
+
+RFC 4422 SASL June 2006
+
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Document Audiences .........................................4
+ 1.2. Relationship to Other Documents ............................4
+ 1.3. Conventions ................................................5
+ 2. Identity Concepts ...............................................5
+ 3. The Authentication Exchange .....................................6
+ 3.1. Mechanism Naming ...........................................8
+ 3.2. Mechanism Negotiation ......................................9
+ 3.3. Request Authentication Exchange ............................9
+ 3.4. Challenges and Responses ...................................9
+ 3.4.1. Authorization Identity String ......................10
+ 3.5. Aborting Authentication Exchanges .........................10
+ 3.6. Authentication Outcome ....................................11
+ 3.7. Security Layers ...........................................12
+ 3.8. Multiple Authentications ..................................12
+ 4. Protocol Requirements ..........................................13
+ 5. Mechanism Requirements .........................................16
+ 6. Security Considerations ........................................18
+ 6.1. Active Attacks ............................................19
+ 6.1.1. Hijack Attacks .....................................19
+ 6.1.2. Downgrade Attacks ..................................19
+ 6.1.3. Replay Attacks .....................................20
+ 6.1.4. Truncation Attacks .................................20
+ 6.1.5. Other Active Attacks ...............................20
+ 6.2. Passive Attacks ...........................................20
+ 6.3. Re-keying .................................................21
+ 6.4. Other Considerations ......................................21
+ 7. IANA Considerations ............................................22
+ 7.1. SASL Mechanism Registry ...................................22
+ 7.2. Registration Changes ......................................26
+ 8. References .....................................................26
+ 8.1. Normative References ......................................26
+ 8.2. Informative References ....................................27
+ 9. Acknowledgements ...............................................28
+ Appendix A. The SASL EXTERNAL Mechanism ..........................29
+ A.1. EXTERNAL Technical Specification ..........................29
+ A.2. SASL EXTERNAL Examples ....................................30
+ A.3. Security Considerations ...................................31
+ Appendix B. Changes since RFC 2222 ...............................31
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 2]
+
+RFC 4422 SASL June 2006
+
+
+1. Introduction
+
+ The Simple Authentication and Security Layer (SASL) is a framework
+ for providing authentication and data security services in
+ connection-oriented protocols via replaceable mechanisms. SASL
+ provides a structured interface between protocols and mechanisms.
+ SASL also provides a protocol for securing subsequent protocol
+ exchanges within a data security layer. The data security layer can
+ provide data integrity, data confidentiality, and other services.
+
+ SASL's design is intended to allow new protocols to reuse existing
+ mechanisms without requiring redesign of the mechanisms and allows
+ existing protocols to make use of new mechanisms without redesign of
+ protocols.
+
+ SASL is conceptually a framework that provides an abstraction layer
+ between protocols and mechanisms as illustrated in the following
+ diagram.
+
+ SMTP LDAP XMPP Other protocols ...
+ \ | | /
+ \ | | /
+ SASL abstraction layer
+ / | | \
+ / | | \
+ EXTERNAL GSSAPI PLAIN Other mechanisms ...
+
+ It is through the interfaces of this abstraction layer that the
+ framework allows any protocol to utilize any mechanism. While this
+ layer does generally hide the particulars of protocols from
+ mechanisms and the particulars of mechanisms from protocols, this
+ layer does not generally hide the particulars of mechanisms from
+ protocol implementations. For example, different mechanisms require
+ different information to operate, some of them use password-based
+ authentication, some of then require realm information, others make
+ use of Kerberos tickets, certificates, etc. Also, in order to
+ perform authorization, server implementations generally have to
+ implement identity mapping between authentication identities, whose
+ form is mechanism specific, and authorization identities, whose form
+ is application protocol specific. Section 2 discusses identity
+ concepts.
+
+ It is possible to design and implement this framework in ways that do
+ abstract away particulars of similar mechanisms. Such a framework
+ implementation, as well as mechanisms implementations, could be
+ designed not only to be shared by multiple implementations of a
+ particular protocol but to be shared by implementations of multiple
+ protocols.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 3]
+
+RFC 4422 SASL June 2006
+
+
+ The framework incorporates interfaces with both protocols and
+ mechanisms in which authentication exchanges are carried out.
+ Section 3 discusses SASL authentication exchanges.
+
+ To use SASL, each protocol (amongst other items) provides a method
+ for identifying which mechanism is to be used, a method for exchange
+ of mechanism-specific server-challenges and client-responses, and a
+ method for communicating the outcome of the authentication exchange.
+ Section 4 discusses SASL protocol requirements.
+
+ Each SASL mechanism defines (amongst other items) a series of
+ server-challenges and client-responses that provide authentication
+ services and negotiate data security services. Section 5 discusses
+ SASL mechanism requirements.
+
+ Section 6 discusses security considerations. Section 7 discusses
+ IANA considerations. Appendix A defines the SASL EXTERNAL mechanism.
+
+1.1. Document Audiences
+
+ This document is written to serve several different audiences:
+
+ - protocol designers using this specification to support
+ authentication in their protocol,
+
+ - mechanism designers that define new SASL mechanisms, and
+
+ - implementors of clients or servers for those protocols that
+ support SASL.
+
+ While the document organization is intended to allow readers to focus
+ on details relevant to their engineering, readers are encouraged to
+ read and understand all aspects of this document.
+
+1.2. Relationship to Other Documents
+
+ This document obsoletes RFC 2222. It replaces all portions of RFC
+ 2222 excepting sections 7.1 (the KERBEROS_IV mechanism), 7.2 (the
+ GSSAPI mechanism), 7.3 (the SKEY mechanism). The KERBEROS_IV and
+ SKEY mechanisms are now viewed as obsolete and their specifications
+ provided in RFC 2222 are Historic. The GSSAPI mechanism is now
+ separately specified [SASL-GSSAPI].
+
+ Appendix B provides a summary of changes since RFC 2222.
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 4]
+
+RFC 4422 SASL June 2006
+
+
+1.3. Conventions
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in BCP 14 [RFC2119].
+
+ Character names in this document use the notation for code points and
+ names from the Unicode Standard [Unicode]. For example, the letter
+ "a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.
+
+ Note: a glossary of terms used in Unicode can be found in [Glossary].
+ Information on the Unicode character encoding model can be found in
+ [CharModel].
+
+ In examples, "C:" and "S:" indicate lines of data to be sent by the
+ client and server, respectively. Lines have been wrapped for
+ improved readability.
+
+2. Identity Concepts
+
+ In practice, authentication and authorization may involve multiple
+ identities, possibly in different forms (simple username, Kerberos
+ principal, X.500 Distinguished Name, etc.), possibly with different
+ representations (e.g., ABNF-described UTF-8 encoded Unicode character
+ string, BER-encoded Distinguished Name). While technical
+ specifications often prescribe both the identity form and
+ representation used on the network, different identity forms and/or
+ representations may be (and often are) used within implementations.
+ How identities of different forms relate to each other is, generally,
+ a local matter. In addition, the forms and representations used
+ within an implementation are a local matter.
+
+ However, conceptually, the SASL framework involves two identities:
+
+ 1) an identity associated with the authentication credentials
+ (termed the authentication identity), and
+
+ 2) an identity to act as (termed the authorization identity).
+
+ SASL mechanism specifications describe the credential form(s) (e.g.,
+ X.509 certificates, Kerberos tickets, simple username/password) used
+ to authenticate the client, including (where appropriate) the syntax
+ and semantics of authentication identities carried in the
+ credentials. SASL protocol specifications describe the identity
+ form(s) used in authorization and, in particular, prescribe the
+ syntax and semantics of the authorization identity character string
+ to be transferred by mechanisms.
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 5]
+
+RFC 4422 SASL June 2006
+
+
+ The client provides its credentials (which include or imply an
+ authentication identity) and, optionally, a character string
+ representing the requested authorization identity as part of the SASL
+ exchange. When this character string is omitted or empty, the client
+ is requesting to act as the identity associated with the credentials
+ (e.g., the user is requesting to act as the authentication identity).
+
+ The server is responsible for verifying the client's credentials and
+ verifying that the identity it associates with the client's
+ credentials (e.g., the authentication identity) is allowed to act as
+ the authorization identity. A SASL exchange fails if either (or
+ both) of these verifications fails. (The SASL exchange may fail for
+ other reasons, such as service authorization failure.)
+
+ However, the precise form(s) of the authentication identities (used
+ within the server in its verifications, or otherwise) and the precise
+ form(s) of the authorization identities (used in making authorization
+ decisions, or otherwise) are beyond the scope of SASL and this
+ specification. In some circumstances, the precise identity forms
+ used in some context outside of the SASL exchange may be dictated by
+ other specifications. For instance, an identity assumption
+ authorization (proxy authorization) policy specification may dictate
+ how authentication and authorization identities are represented in
+ policy statements.
+
+3. The Authentication Exchange
+
+ Each authentication exchange consists of a message from the client to
+ the server requesting authentication via a particular mechanism,
+ followed by one or more pairs of challenges from the server and
+ responses from the client, followed by a message from the server
+ indicating the outcome of the authentication exchange. (Note:
+ exchanges may also be aborted as discussed in Section 3.5.)
+
+ The following illustration provides a high-level overview of an
+ authentication exchange.
+
+ C: Request authentication exchange
+ S: Initial challenge
+ C: Initial response
+ <additional challenge/response messages>
+ S: Outcome of authentication exchange
+
+ If the outcome is successful and a security layer was negotiated,
+ this layer is then installed (see Section 3.7). This also applies to
+ the following illustrations.
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 6]
+
+RFC 4422 SASL June 2006
+
+
+ Some mechanisms specify that the first data sent in the
+ authentication exchange is from the client to the server. Protocols
+ may provide an optional initial response field in the request message
+ to carry this data. Where the mechanism specifies that the first
+ data sent in the exchange is from the client to the server, the
+ protocol provides an optional initial response field, and the client
+ uses this field, the exchange is shortened by one round-trip:
+
+ C: Request authentication exchange + Initial response
+ <additional challenge/response messages>
+ S: Outcome of authentication exchange
+
+ Where the mechanism specifies that the first data sent in the
+ exchange is from the client to the server and this field is
+ unavailable or unused, the client request is followed by an empty
+ challenge.
+
+ C: Request authentication exchange
+ S: Empty Challenge
+ C: Initial Response
+ <additional challenge/response messages>
+ S: Outcome of authentication exchange
+
+ Should a client include an initial response in its request where the
+ mechanism does not allow the client to send data first, the
+ authentication exchange fails.
+
+ Some mechanisms specify that the server is to send additional data to
+ the client when indicating a successful outcome. Protocols may
+ provide an optional additional data field in the outcome message to
+ carry this data. Where the mechanism specifies that the server is to
+ return additional data with the successful outcome, the protocol
+ provides an optional additional data field in the outcome message,
+ and the server uses this field, the exchange is shortened by one
+ round-trip:
+
+ C: Request authentication exchange
+ S: Initial challenge
+ C: Initial response
+ <additional challenge/response messages>
+ S: Outcome of authentication exchange with
+ additional data with success
+
+ Where the mechanism specifies that the server is to return additional
+ data to the client with a successful outcome and this field is
+ unavailable or unused, the additional data is sent as a challenge
+ whose response is empty. After receiving this response, the server
+ then indicates the successful outcome.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 7]
+
+RFC 4422 SASL June 2006
+
+
+ C: Request authentication exchange
+ S: Initial challenge
+ C: Initial response
+ <additional challenge/response messages>
+ S: Additional data challenge
+ C: Empty Response
+ S: Outcome of authentication exchange
+
+ Where mechanisms specify that the first data sent in the exchange is
+ from the client to the server and additional data is sent to the
+ client along with indicating a successful outcome, and the protocol
+ provides fields supporting both, then the exchange takes two fewer
+ round-trips:
+
+ C: Request authentication exchange + Initial response
+ <additional challenge/response messages>
+ S: Outcome of authentication exchange
+ with additional data with success
+
+ instead of:
+
+ C: Request authentication exchange
+ S: Empty Challenge
+ C: Initial Response
+ <additional challenge/response messages>
+ S: Additional data challenge
+ C: Empty Response
+ S: Outcome of authentication exchange
+
+3.1. Mechanism Naming
+
+ SASL mechanisms are named by character strings, from 1 to 20
+ characters in length, consisting of ASCII [ASCII] uppercase letters,
+ digits, hyphens, and/or underscores. In the following Augmented
+ Backus-Naur Form (ABNF) [RFC4234] grammar, the <sasl-mech> production
+ defines the syntax of a SASL mechanism name.
+
+ sasl-mech = 1*20mech-char
+ mech-char = UPPER-ALPHA / DIGIT / HYPHEN / UNDERSCORE
+ ; mech-char is restricted to A-Z (uppercase only), 0-9, -, and _
+ ; from ASCII character set.
+
+ UPPER-ALPHA = %x41-5A ; A-Z (uppercase only)
+ DIGIT = %x30-39 ; 0-9
+ HYPHEN = %x2D ; hyphen (-)
+ UNDERSCORE = %x5F ; underscore (_)
+
+ SASL mechanism names are registered as discussed in Section 7.1.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 8]
+
+RFC 4422 SASL June 2006
+
+
+3.2. Mechanism Negotiation
+
+ Mechanism negotiation is protocol specific.
+
+ Commonly, a protocol will specify that the server advertises
+ supported and available mechanisms to the client via some facility
+ provided by the protocol, and the client will then select the "best"
+ mechanism from this list that it supports and finds suitable.
+
+ Note that the mechanism negotiation is not protected by the
+ subsequent authentication exchange and hence is subject to downgrade
+ attacks if not protected by other means.
+
+ To detect downgrade attacks, a protocol can allow the client to
+ discover available mechanisms subsequent to the authentication
+ exchange and installation of data security layers with at least data
+ integrity protection. This allows the client to detect changes to
+ the list of mechanisms supported by the server.
+
+3.3. Request Authentication Exchange
+
+ The authentication exchange is initiated by the client by requesting
+ authentication via a mechanism it specifies. The client sends a
+ message that contains the name of the mechanism to the server. The
+ particulars of the message are protocol specific.
+
+ Note that the name of the mechanism is not protected by the
+ mechanism, and hence is subject to alteration by an attacker if not
+ integrity protected by other means.
+
+ Where the mechanism is defined to allow the client to send data
+ first, and the protocol's request message includes an optional
+ initial response field, the client may include the response to the
+ initial challenge in the authentication request message.
+
+3.4. Challenges and Responses
+
+ The authentication exchange involves one or more pairs of server-
+ challenges and client-responses, the particulars of which are
+ mechanism specific. These challenges and responses are enclosed in
+ protocol messages, the particulars of which are protocol specific.
+
+ Through these challenges and responses, the mechanism may:
+
+ - authenticate the client to the server,
+
+ - authenticate the server to the client,
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 9]
+
+RFC 4422 SASL June 2006
+
+
+ - transfer an authorization identity string,
+
+ - negotiate a security layer, and
+
+ - provide other services.
+
+ The negotiation of the security layer may involve negotiation of the
+ security services to be provided in the layer, how these services
+ will be provided, and negotiation of a maximum cipher-text buffer
+ size each side is able to receive in the layer (see Section 3.6).
+
+ After receiving an authentication request or any client response, the
+ server may issue a challenge, abort the exchange, or indicate the
+ outcome of an exchange. After receiving a challenge, a client
+ mechanism may issue a response or abort the exchange.
+
+3.4.1. Authorization Identity String
+
+ The authorization identity string is a sequence of zero or more
+ Unicode [Unicode] characters, excluding the NUL (U+0000) character,
+ representing the identity to act as.
+
+ If the authorization identity string is absent, the client is
+ requesting to act as the identity the server associates with the
+ client's credentials. An empty string is equivalent to an absent
+ authorization identity.
+
+ A non-empty authorization identity string indicates that the client
+ wishes to act as the identity represented by the string. In this
+ case, the form of identity represented by the string, as well as the
+ precise syntax and semantics of the string, is protocol specific.
+
+ While the character encoding schema used to transfer the
+ authorization identity string in the authentication exchange is
+ mechanism specific, mechanisms are expected to be capable of carrying
+ the entire Unicode repertoire (with the exception of the NUL
+ character).
+
+3.5. Aborting Authentication Exchanges
+
+ A client or server may desire to abort an authentication exchange if
+ it is unwilling or unable to continue (or enter into).
+
+ A client may abort the authentication exchange by sending a message,
+ the particulars of which are protocol specific, to the server,
+ indicating that the exchange is aborted. The server may be required
+ by the protocol to return a message in response to the client's abort
+ message.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 10]
+
+RFC 4422 SASL June 2006
+
+
+ Likewise, a server may abort the authentication exchange by sending a
+ message, the particulars of which are protocol specific, to the
+ client, indicating that the exchange is aborted.
+
+3.6. Authentication Outcome
+
+ At the conclusion of the authentication exchange, the server sends a
+ message, the particulars of which are protocol specific, to the
+ client indicating the outcome of the exchange.
+
+ The outcome is not successful if
+
+ - the authentication exchange failed for any reason,
+
+ - the client's credentials could not be verified,
+
+ - the server cannot associate an identity with the client's
+ credentials,
+
+ - the client-provided authorization identity string is malformed,
+
+ - the identity associated with the client's credentials is not
+ authorized to act as the requested authorization identity,
+
+ - the negotiated security layer (or lack thereof) is not
+ suitable, or
+
+ - the server is not willing to provide service to the client for
+ any reason.
+
+ The protocol may include an optional additional data field in this
+ outcome message. This field can only include additional data when
+ the outcome is successful.
+
+ If the outcome is successful and a security layer was negotiated,
+ this layer is then installed. If the outcome is unsuccessful, or a
+ security layer was not negotiated, any existing security is left in
+ place.
+
+ The outcome message provided by the server can provide a way for the
+ client to distinguish between errors that are best dealt with by re-
+ prompting the user for her credentials, errors that are best dealt
+ with by telling the user to try again later, and errors where the
+ user must contact a system administrator for resolution (see the SYS
+ and AUTH POP Response Codes [RFC3206] specification for an example).
+ This distinction is particularly useful during scheduled server
+ maintenance periods as it reduces support costs. It is also
+ important that the server can be configured such that the outcome
+
+
+
+Melnikov & Zeilenga Standards Track [Page 11]
+
+RFC 4422 SASL June 2006
+
+
+ message will not distinguish between a valid user with invalid
+ credentials and an invalid user.
+
+3.7. Security Layers
+
+ SASL mechanisms may offer a wide range of services in security
+ layers. Typical services include data integrity and data
+ confidentiality. SASL mechanisms that do not provide a security
+ layer are treated as negotiating no security layer.
+
+ If use of a security layer is negotiated in the authentication
+ protocol exchange, the layer is installed by the server after
+ indicating the outcome of the authentication exchange and installed
+ by the client upon receipt of the outcome indication. In both cases,
+ the layer is installed before transfer of further protocol data. The
+ precise position upon which the layer takes effect in the protocol
+ data stream is protocol specific.
+
+ Once the security layer is in effect in the protocol data stream, it
+ remains in effect until either a subsequently negotiated security
+ layer is installed or the underlying transport connection is closed.
+
+ When in effect, the security layer processes protocol data into
+ buffers of protected data. If at any time the security layer is
+ unable or unwilling to continue producing buffers protecting protocol
+ data, the underlying transport connection MUST be closed. If the
+ security layer is not able to decode a received buffer, the
+ underlying connection MUST be closed. In both cases, the underlying
+ transport connection SHOULD be closed gracefully.
+
+ Each buffer of protected data is transferred over the underlying
+ transport connection as a sequence of octets prepended with a four-
+ octet field in network byte order that represents the length of the
+ buffer. The length of the protected data buffer MUST be no larger
+ than the maximum size that the other side expects. Upon the receipt
+ of a length field whose value is greater than the maximum size, the
+ receiver SHOULD close the connection, as this might be a sign of an
+ attack.
+
+ The maximum size that each side expects is fixed by the mechanism,
+ either through negotiation or by its specification.
+
+3.8. Multiple Authentications
+
+ Unless explicitly permitted in the protocol (as stated in the
+ protocol's technical specification), only one successful SASL
+ authentication exchange may occur in a protocol session. In this
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 12]
+
+RFC 4422 SASL June 2006
+
+
+ case, once an authentication exchange has successfully completed,
+ further attempts to initiate an authentication exchange fail.
+
+ Where multiple successful SASL authentication exchanges are permitted
+ in the protocol, then in no case may multiple SASL security layers be
+ simultaneously in effect. If a security layer is in effect and a
+ subsequent SASL negotiation selects a second security layer, then the
+ second security layer replaces the first. If a security layer is in
+ effect and a subsequent SASL negotiation selects no security layer,
+ the original security layer remains in effect.
+
+ Where multiple successful SASL negotiations are permitted in the
+ protocol, the effect of a failed SASL authentication exchange upon
+ the previously established authentication and authorization state is
+ protocol specific. The protocol's technical specification should be
+ consulted to determine whether the previous authentication and
+ authorization state remains in force, or changed to an anonymous
+ state, or otherwise was affected. Regardless of the protocol-
+ specific effect upon previously established authentication and
+ authorization state, the previously negotiated security layer remains
+ in effect.
+
+4. Protocol Requirements
+
+ In order for a protocol to offer SASL services, its specification
+ MUST supply the following information:
+
+ 1) A service name, to be selected from registry of "service" elements
+ for the Generic Security Service Application Program Interface
+ (GSSAPI) host-based service name form, as described in Section 4.1
+ of [RFC2743]. Note that this registry is shared by all GSSAPI and
+ SASL mechanisms.
+
+ 2) Detail any mechanism negotiation facility that the protocol
+ provides (see Section 3.2).
+
+ A protocol SHOULD specify a facility through which the client may
+ discover, both before initiation of the SASL exchange and after
+ installing security layers negotiated by the exchange, the names
+ of the SASL mechanisms that the server makes available to the
+ client. The latter is important to allow the client to detect
+ downgrade attacks. This facility is typically provided through
+ the protocol's extensions or capabilities discovery facility.
+
+ 3) Definition of the messages necessary for authentication exchange,
+ including the following:
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 13]
+
+RFC 4422 SASL June 2006
+
+
+ a) A message to initiate the authentication exchange (see Section
+ 3.3).
+
+ This message MUST contain a field for carrying the name of the
+ mechanism selected by the client.
+
+ This message SHOULD contain an optional field for carrying an
+ initial response. If the message is defined with this field,
+ the specification MUST describe how messages with an empty
+ initial response are distinguished from messages with no
+ initial response. This field MUST be capable of carrying
+ arbitrary sequences of octets (including zero-length sequences
+ and sequences containing zero-valued octets).
+
+ b) Messages to transfer server challenges and client responses
+ (see Section 3.4).
+
+ Each of these messages MUST be capable of carrying arbitrary
+ sequences of octets (including zero-length sequences and
+ sequences containing zero-valued octets).
+
+ c) A message to indicate the outcome of the authentication
+ exchange (see Section 3.6).
+
+ This message SHOULD contain an optional field for carrying
+ additional data with a successful outcome. If the message is
+ defined with this field, the specification MUST describe how
+ messages with an empty additional data are distinguished from
+ messages with no additional data. This field MUST be capable
+ of carrying arbitrary sequences of octets (including zero-
+ length sequences and sequences containing zero-valued octets).
+
+ 4) Prescribe the syntax and semantics of non-empty authorization
+ identity strings (see Section 3.4.1).
+
+ In order to avoid interoperability problems due to differing
+ normalizations, the protocol specification MUST detail precisely
+ how and where (client or server) non-empty authorization identity
+ strings are prepared, including all normalizations, for comparison
+ and other applicable functions to ensure proper function.
+
+ Specifications are encouraged to prescribe use of existing
+ authorization identity forms as well as existing string
+ representations, such as simple user names [RFC4013].
+
+ Where the specification does not precisely prescribe how
+ identities in SASL relate to identities used elsewhere in the
+ protocol, for instance, in access control policy statements, it
+
+
+
+Melnikov & Zeilenga Standards Track [Page 14]
+
+RFC 4422 SASL June 2006
+
+
+ may be appropriate for the protocol to provide a facility by which
+ the client can discover information (such as the representation of
+ the identity used in making access control decisions) about
+ established identities for these uses.
+
+ 5) Detail any facility the protocol provides that allows the client
+ and/or server to abort authentication exchange (see Section 3.5).
+
+ Protocols that support multiple authentications typically allow a
+ client to abort an ongoing authentication exchange by initiating a
+ new authentication exchange. Protocols that do not support
+ multiple authentications may require the client to close the
+ connection and start over to abort an ongoing authentication
+ exchange.
+
+ Protocols typically allow the server to abort ongoing
+ authentication exchanges by returning a non-successful outcome
+ message.
+
+ 6) Identify precisely where newly negotiated security layers start to
+ take effect, in both directions (see Section 3.7).
+
+ Typically, specifications require security layers to start taking
+ effect on the first octet following the outcome message in data
+ being sent by the server and on the first octet sent after receipt
+ of the outcome message in data being sent by the client.
+
+ 7) If the protocol supports other layered security services, such as
+ Transport Layer Security (TLS) [RFC4346], the specification MUST
+ prescribe the order in which security layers are applied to
+ protocol data.
+
+ For instance, where a protocol supports both TLS and SASL security
+ layers, the specification could prescribe any of the following:
+
+ a) SASL security layer is always applied first to data being sent
+ and, hence, applied last to received data,
+
+ b) SASL security layer is always applied last to data being sent
+ and, hence, applied first to received data,
+
+ c) Layers are applied in the order in which they were installed,
+
+ d) Layers are applied in the reverse order in which they were
+ installed, or
+
+ e) Both TLS and SASL security layers cannot be installed.
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 15]
+
+RFC 4422 SASL June 2006
+
+
+ 8) Indicate whether the protocol supports multiple authentications
+ (see Section 3.8). If so, the protocol MUST detail the effect a
+ failed SASL authentication exchange will have upon a previously
+ established authentication and authorization state.
+
+ Protocol specifications SHOULD avoid stating implementation
+ requirements that would hinder replacement of applicable mechanisms.
+ In general, protocol specifications SHOULD be mechanism neutral.
+ There are a number of reasonable exceptions to this recommendation,
+ including
+
+ - detailing how credentials (which are mechanism specific) are
+ managed in the protocol,
+
+ - detailing how authentication identities (which are mechanism
+ specific) and authorization identities (which are protocol
+ specific) relate to each other, and
+
+ - detailing which mechanisms are applicable to the protocol.
+
+5. Mechanism Requirements
+
+ SASL mechanism specifications MUST supply the following information:
+
+ 1) The name of the mechanism (see Section 3.1). This name MUST be
+ registered as discussed in Section 7.1.
+
+ 2) A definition of the server-challenges and client-responses of the
+ authentication exchange, as well as the following:
+
+ a) An indication of whether the mechanism is client-first,
+ variable, or server-first. If a SASL mechanism is defined as
+ client-first and the client does not send an initial response
+ in the authentication request, then the first server challenge
+ MUST be empty (the EXTERNAL mechanism is an example of this
+ case). If a SASL mechanism is defined as variable, then the
+ specification needs to state how the server behaves when the
+ initial client response in the authentication request is
+ omitted (the DIGEST-MD5 mechanism [DIGEST-MD5] is an example of
+ this case). If a SASL mechanism is defined as server-first,
+ then the client MUST NOT send an initial client response in the
+ authentication request (the CRAM-MD5 mechanism [CRAM-MD5] is an
+ example of this case).
+
+ b) An indication of whether the server is expected to provide
+ additional data when indicating a successful outcome. If so,
+ if the server sends the additional data as a challenge, the
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 16]
+
+RFC 4422 SASL June 2006
+
+
+ specification MUST indicate that the response to this challenge
+ is an empty response.
+
+ SASL mechanisms SHOULD be designed to minimize the number of
+ challenges and responses necessary to complete the exchange.
+
+ 3) An indication of whether the mechanism is capable of transferring
+ authorization identity strings (see Section 3.4.1). While some
+ legacy mechanisms are incapable of transmitting an authorization
+ identity (which means that for these mechanisms, the authorization
+ identity is always the empty string), newly defined mechanisms
+ SHOULD be capable of transferring authorization identity strings.
+ The mechanism SHOULD NOT be capable of transferring both no
+ authorization identity string and an empty authorization identity.
+
+ Mechanisms that are capable of transferring an authorization
+ identity string MUST be capable of transferring arbitrary non-
+ empty sequences of Unicode characters, excluding those that
+ contain the NUL (U+0000) character. Mechanisms SHOULD use the
+ UTF-8 [RFC3629] transformation format. The specification MUST
+ detail how any Unicode code points special to the mechanism that
+ might appear in the authorization identity string are escaped to
+ avoid ambiguity during decoding of the authorization identity
+ string. Typically, mechanisms that have special characters
+ require these special characters to be escaped or encoded in the
+ character string (after encoding it in a particular Unicode
+ transformation format) using a data encoding scheme such as Base64
+ [RFC3548].
+
+ 4) The specification MUST detail whether the mechanism offers a
+ security layer. If the mechanism does, the specification MUST
+ detail the security and other services offered in the layer as
+ well as how these services are to be implemented.
+
+ 5) If the underlying cryptographic technology used by a mechanism
+ supports data integrity, then the mechanism specification MUST
+ integrity protect the transmission of an authorization identity
+ and the negotiation of the security layer.
+
+ SASL mechanisms SHOULD be protocol neutral.
+
+ SASL mechanisms SHOULD reuse existing credential and identity forms,
+ as well as associated syntaxes and semantics.
+
+ SASL mechanisms SHOULD use the UTF-8 transformation format [RFC3629]
+ for encoding Unicode [Unicode] code points for transfer.
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 17]
+
+RFC 4422 SASL June 2006
+
+
+ In order to avoid interoperability problems due to differing
+ normalizations, when a mechanism calls for character data (other than
+ the authorization identity string) to be used as input to a
+ cryptographic and/or comparison function, the specification MUST
+ detail precisely how and where (client or server) the character data
+ is to be prepared, including all normalizations, for input into the
+ function to ensure proper operation.
+
+ For simple user names and/or passwords in authentication credentials,
+ SASLprep [RFC4013] (a profile of the StringPrep [RFC3454] preparation
+ algorithm), SHOULD be specified as the preparation algorithm.
+
+ The mechanism SHOULD NOT use the authorization identity string in
+ generation of any long-term cryptographic keys or hashes as there is
+ no requirement that the authorization identity string be canonical.
+ Long-term, here, means a term longer than the duration of the
+ authentication exchange in which they were generated. That is, as
+ different clients (of the same or different protocol) may provide
+ different authorization identity strings that are semantically
+ equivalent, use of authorization identity strings in generation of
+ cryptographic keys and hashes will likely lead to interoperability
+ and other problems.
+
+6. Security Considerations
+
+ Security issues are discussed throughout this memo.
+
+ Many existing SASL mechanisms do not provide adequate protection
+ against passive attacks, let alone active attacks, in the
+ authentication exchange. Many existing SASL mechanisms do not offer
+ security layers. It is hoped that future SASL mechanisms will
+ provide strong protection against passive and active attacks in the
+ authentication exchange, as well as security layers with strong basic
+ data security features (e.g., data integrity and data
+ confidentiality) services. It is also hoped that future mechanisms
+ will provide more advanced data security services like re-keying (see
+ Section 6.3).
+
+ Regardless, the SASL framework is susceptible to downgrade attacks.
+ Section 6.1.2 offers a variety of approaches for preventing or
+ detecting these attacks. In some cases, it is appropriate to use
+ data integrity protective services external to SASL (e.g., TLS) to
+ protect against downgrade attacks in SASL. Use of external
+ protective security services is also important when the mechanisms
+ available do not themselves offer adequate integrity and/or
+ confidentiality protection of the authentication exchange and/or
+ protocol data.
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 18]
+
+RFC 4422 SASL June 2006
+
+
+6.1. Active Attacks
+
+6.1.1. Hijack Attacks
+
+ When the client selects a SASL security layer with at least integrity
+ protection, this protection serves as a counter-measure against an
+ active attacker hijacking the connection and modifying protocol data
+ sent after establishment of the security layer. Implementations
+ SHOULD close the connection when the security services in a SASL
+ security layer report protocol data report lack of data integrity.
+
+6.1.2. Downgrade Attacks
+
+ It is important that any security-sensitive protocol negotiations be
+ performed after installation of a security layer with data integrity
+ protection. Protocols should be designed such that negotiations
+ performed prior to this installation should be revalidated after
+ installation is complete. Negotiation of the SASL mechanism is
+ security sensitive.
+
+ When a client negotiates the authentication mechanism with the server
+ and/or other security features, it is possible for an active attacker
+ to cause a party to use the least secure security services available.
+ For instance, an attacker can modify the server-advertised mechanism
+ list or can modify the client-advertised security feature list within
+ a mechanism response. To protect against this sort of attack,
+ implementations SHOULD NOT advertise mechanisms and/or features that
+ cannot meet their minimum security requirements, SHOULD NOT enter
+ into or continue authentication exchanges that cannot meet their
+ minimum security requirements, and SHOULD verify that completed
+ authentication exchanges result in security services that meet their
+ minimum security requirements. Note that each endpoint needs to
+ independently verify that its security requirements are met.
+
+ In order to detect downgrade attacks to the least (or less) secure
+ mechanism supported, the client can discover the SASL mechanisms that
+ the server makes available both before the SASL authentication
+ exchange and after the negotiated SASL security layer (with at least
+ data integrity protection) has been installed through the protocol's
+ mechanism discovery facility. If the client finds that the
+ integrity-protected list (the list obtained after the security layer
+ was installed) contains a stronger mechanism than those in the
+ previously obtained list, the client should assume that the
+ previously obtained list was modified by an attacker and SHOULD close
+ the underlying transport connection.
+
+ The client's initiation of the SASL exchange, including the selection
+ of a SASL mechanism, is done in the clear and may be modified by an
+
+
+
+Melnikov & Zeilenga Standards Track [Page 19]
+
+RFC 4422 SASL June 2006
+
+
+ active attacker. It is important for any new SASL mechanisms to be
+ designed such that an active attacker cannot obtain an authentication
+ with weaker security properties by modifying the SASL mechanism name
+ and/or the challenges and responses.
+
+ Multi-level negotiation of security features is prone to downgrade
+ attack. Protocol designers should avoid offering higher-level
+ negotiation of security features in protocols (e.g., above SASL
+ mechanism negotiation) and mechanism designers should avoid lower-
+ level negotiation of security features in mechanisms (e.g., below
+ SASL mechanism negotiation).
+
+6.1.3. Replay Attacks
+
+ Some mechanisms may be subject to replay attacks unless protected by
+ external data security services (e.g., TLS).
+
+6.1.4. Truncation Attacks
+
+ Most existing SASL security layers do not themselves offer protection
+ against truncation attack. In a truncation attack, the active
+ attacker causes the protocol session to be closed, causing a
+ truncation of the possibly integrity-protected data stream that leads
+ to behavior of one or both the protocol peers that inappropriately
+ benefits the attacker. Truncation attacks are fairly easy to defend
+ against in connection-oriented application-level protocols. A
+ protocol can defend against these attacks by ensuring that each
+ information exchange has a clear final result and that each protocol
+ session has a graceful closure mechanism, and that these are
+ integrity protected.
+
+6.1.5. Other Active Attacks
+
+ When use of a security layer is negotiated by the authentication
+ protocol exchange, the receiver SHOULD handle gracefully any
+ protected data buffer larger than the defined/negotiated maximal
+ size. In particular, it MUST NOT blindly allocate the amount of
+ memory specified in the buffer size field, as this might cause the
+ "out of memory" condition. If the receiver detects a large block, it
+ SHOULD close the connection.
+
+6.2. Passive Attacks
+
+ Many mechanisms are subject to various passive attacks, including
+ simple eavesdropping of unprotected credential information as well as
+ online and offline dictionary attacks of protected credential
+ information.
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 20]
+
+RFC 4422 SASL June 2006
+
+
+6.3. Re-keying
+
+ The secure or administratively permitted lifetimes of SASL
+ mechanisms' security layers are finite. Cryptographic keys weaken as
+ they are used and as time passes; the more time and/or cipher-text
+ that a cryptanalyst has after the first use of the a key, the easier
+ it is for the cryptanalyst to mount attacks on the key.
+
+ Administrative limits on a security layer's lifetime may take the
+ form of time limits expressed in X.509 certificates, in Kerberos V
+ tickets, or in directories, and are often desired. In practice, one
+ likely effect of administrative lifetime limits is that applications
+ may find that security layers stop working in the middle of
+ application protocol operation, such as, perhaps, during large data
+ transfers. As the result of this, the connection will be closed (see
+ Section 3.7), which will result in an unpleasant user experience.
+
+ Re-keying (key renegotiation process) is a way of addressing the
+ weakening of cryptographic keys. The SASL framework does not itself
+ provide for re-keying; SASL mechanisms may. Designers of future SASL
+ mechanisms should consider providing re-keying services.
+
+ Implementations that wish to re-key SASL security layers where the
+ mechanism does not provide for re-keying SHOULD reauthenticate the
+ same IDs and replace the expired or soon-to-expire security layers.
+ This approach requires support for reauthentication in the
+ application protocols (see Section 3.8).
+
+6.4. Other Considerations
+
+ Protocol designers and implementors should understand the security
+ considerations of mechanisms so they may select mechanisms that are
+ applicable to their needs.
+
+ Distributed server implementations need to be careful in how they
+ trust other parties. In particular, authentication secrets should
+ only be disclosed to other parties that are trusted to manage and use
+ those secrets in a manner acceptable to the disclosing party.
+ Applications using SASL assume that SASL security layers providing
+ data confidentiality are secure even when an attacker chooses the
+ text to be protected by the security layer. Similarly, applications
+ assume that the SASL security layer is secure even if the attacker
+ can manipulate the cipher-text output of the security layer. New
+ SASL mechanisms are expected to meet these assumptions.
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 21]
+
+RFC 4422 SASL June 2006
+
+
+ Unicode security considerations [UTR36] apply to authorization
+ identity strings, as well as UTF-8 [RFC3629] security considerations
+ where UTF-8 is used. SASLprep [RFC4013] and StringPrep [RFC3454]
+ security considerations also apply where used.
+
+7. IANA Considerations
+
+7.1. SASL Mechanism Registry
+
+ The SASL mechanism registry is maintained by IANA. The registry is
+ currently available at <http://www.iana.org/assignments/sasl-
+ mechanisms>.
+
+ The purpose of this registry is not only to ensure uniqueness of
+ values used to name SASL mechanisms, but also to provide a definitive
+ reference to technical specifications detailing each SASL mechanism
+ available for use on the Internet.
+
+ There is no naming convention for SASL mechanisms; any name that
+ conforms to the syntax of a SASL mechanism name can be registered.
+
+ The procedure detailed in Section 7.1.1 is to be used for
+ registration of a value naming a specific individual mechanism.
+
+ The procedure detailed in Section 7.1.2 is to be used for
+ registration of a value naming a family of related mechanisms.
+
+ Comments may be included in the registry as discussed in Section
+ 7.1.3 and may be changed as discussed in Section 7.1.4.
+
+ The SASL mechanism registry has been updated to reflect that this
+ document provides the definitive technical specification for SASL and
+ that this section provides the registration procedures for this
+ registry.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 22]
+
+RFC 4422 SASL June 2006
+
+
+7.1.1. Mechanism Name Registration Procedure
+
+ IANA will register new SASL mechanism names on a First Come First
+ Served basis, as defined in BCP 26 [RFC2434]. IANA has the right to
+ reject obviously bogus registration requests, but will perform no
+ review of claims made in the registration form.
+
+ Registration of a SASL mechanism is requested by filling in the
+ following template:
+
+ Subject: Registration of SASL mechanism X
+
+ SASL mechanism name (or prefix for the family):
+
+ Security considerations:
+
+ Published specification (recommended):
+
+ Person & email address to contact for further information:
+
+ Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE)
+
+ Owner/Change controller:
+
+ Note: (Any other information that the author deems relevant may be
+ added here.)
+
+ and sending it via electronic mail to IANA at <iana@iana.org>.
+
+ While this registration procedure does not require expert review,
+ authors of SASL mechanisms are encouraged to seek community review
+ and comment whenever that is feasible. Authors may seek community
+ review by posting a specification of their proposed mechanism as an
+ Internet-Draft. SASL mechanisms intended for widespread use should
+ be standardized through the normal IETF process, when appropriate.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 23]
+
+RFC 4422 SASL June 2006
+
+
+7.1.2. Family Name Registration Procedure
+
+ As noted above, there is no general naming convention for SASL
+ mechanisms. However, specifications may reserve a portion of the
+ SASL mechanism namespace for a set of related SASL mechanisms, a
+ "family" of SASL mechanisms. Each family of SASL mechanisms is
+ identified by a unique prefix, such as X-. Registration of new SASL
+ mechanism family names requires expert review as defined in BCP 26
+ [RFC2434].
+
+ Registration of a SASL family name is requested by filling in the
+ following template:
+
+ Subject: Registration of SASL mechanism family X
+
+ SASL family name (or prefix for the family):
+
+ Security considerations:
+
+ Published specification (recommended):
+
+ Person & email address to contact for further information:
+
+ Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE)
+
+ Owner/Change controller:
+
+ Note: (Any other information that the author deems relevant may be
+ added here.)
+
+ and sending it via electronic mail to the IETF SASL mailing list at
+ <ietf-sasl@imc.org> and carbon copying IANA at <iana@iana.org>.
+ After allowing two weeks for community input on the IETF SASL mailing
+ list, the expert will determine the appropriateness of the
+ registration request and either approve or disapprove the request
+ with notice to the requestor, the mailing list, and IANA.
+
+ The review should focus on the appropriateness of the requested
+ family name for the proposed use and the appropriateness of the
+ proposed naming and registration plan for existing and future
+ mechanism names in the family. The scope of this request review may
+ entail consideration of relevant aspects of any provided technical
+ specification, such as their IANA Considerations section. However,
+ this review is narrowly focused on the appropriateness of the
+ requested registration and not on the overall soundness of any
+ provided technical specification.
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 24]
+
+RFC 4422 SASL June 2006
+
+
+ Authors are encouraged to pursue community review by posting the
+ technical specification as an Internet-Draft and soliciting comment
+ by posting to appropriate IETF mailing lists.
+
+7.1.3. Comments on SASL Mechanism Registrations
+
+ Comments on a registered SASL mechanism/family should first be sent
+ to the "owner" of the mechanism/family and/or to the <ietf-
+ sasl@imc.org> mailing list.
+
+ Submitters of comments may, after a reasonable attempt to contact the
+ owner, request IANA to attach their comment to the SASL mechanism
+ registration itself by sending mail to <iana@iana.org>. At IANA's
+ sole discretion, IANA may attach the comment to the SASL mechanism's
+ registration.
+
+7.1.4. Change Control
+
+ Once a SASL mechanism registration has been published by IANA, the
+ author may request a change to its definition. The change request
+ follows the same procedure as the registration request.
+
+ The owner of a SASL mechanism may pass responsibility for the SASL
+ mechanism to another person or agency by informing IANA; this can be
+ done without discussion or review.
+
+ The IESG may reassign responsibility for a SASL mechanism. The most
+ common case of this will be to enable changes to be made to
+ mechanisms where the author of the registration has died, has moved
+ out of contact, or is otherwise unable to make changes that are
+ important to the community.
+
+ SASL mechanism registrations may not be deleted; mechanisms that are
+ no longer believed appropriate for use can be declared OBSOLETE by a
+ change to their "intended usage" field; such SASL mechanisms will be
+ clearly marked in the lists published by IANA.
+
+ The IESG is considered to be the owner of all SASL mechanisms that
+ are on the IETF standards track.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 25]
+
+RFC 4422 SASL June 2006
+
+
+7.2. Registration Changes
+
+ The IANA has updated the SASL mechanisms registry as follows:
+
+ 1) Changed the "Intended usage" of the KERBEROS_V4 and SKEY mechanism
+ registrations to OBSOLETE.
+
+ 2) Changed the "Published specification" of the EXTERNAL mechanism to
+ this document as indicated below:
+
+ Subject: Updated Registration of SASL mechanism EXTERNAL
+ Family of SASL mechanisms: NO
+ SASL mechanism name: EXTERNAL
+ Security considerations: See A.3 of RFC 4422
+ Published specification (optional, recommended): RFC 4422
+ Person & email address to contact for further information:
+ Alexey Melnikov <Alexey.Melnikov@isode.com>
+ Intended usage: COMMON
+ Owner/Change controller: IESG <iesg@ietf.org>
+ Note: Updates existing entry for EXTERNAL
+
+8. References
+
+8.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2244] Newman, C. and J. G. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November
+ 1997.
+
+ [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing
+ an IANA Considerations Section in RFCs", BCP 26, RFC
+ 2434, October 1998.
+
+ [RFC2743] Linn, J., "Generic Security Service Application Program
+ Interface Version 2, Update 1", RFC 2743, January 2000.
+
+ [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 26]
+
+RFC 4422 SASL June 2006
+
+
+ [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [ASCII] Coded Character Set--7-bit American Standard Code for
+ Information Interchange, ANSI X3.4-1986.
+
+ [Unicode] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0" is defined by "The Unicode Standard, Version
+ 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+ 61633-5), as amended by the "Unicode Standard Annex
+ #27: Unicode 3.1"
+ (http://www.unicode.org/reports/tr27/) and by the
+ "Unicode Standard Annex #28: Unicode 3.2"
+ (http://www.unicode.org/reports/tr28/).
+
+ [CharModel] Whistler, K. and M. Davis, "Unicode Technical Report
+ #17, Character Encoding Model", UTR17,
+ <http://www.unicode.org/unicode/reports/tr17/>, August
+ 2000.
+
+ [Glossary] The Unicode Consortium, "Unicode Glossary",
+ <http://www.unicode.org/glossary/>.
+
+8.2. Informative References
+
+ [RFC3206] Gellens, R., "The SYS and AUTH POP Response Codes", RFC
+ 3206, February 2002.
+
+ [RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
+ Encodings", RFC 3548, July 2003.
+
+ [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
+ Internet Protocol", RFC 4301, December 2005.
+
+ [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer
+ Security (TLS) Protocol Version 1.1", RFC 4346, April
+ 2006.
+
+ [SASL-GSSAPI] Melnikov, A. (Editor), "The Kerberos V5 ("GSSAPI") SASL
+ Mechanism", Work in Progress, May 2006.
+
+ [UTR36] Davis, M., "(Draft) Unicode Technical Report #36,
+ Character Encoding Model", UTR17,
+ <http://www.unicode.org/unicode/reports/tr36/>,
+ February 2005.
+
+ [CRAM-MD5] Nerenberg, L., "The CRAM-MD5 SASL Mechanism", Work in
+ Progress.
+
+
+
+Melnikov & Zeilenga Standards Track [Page 27]
+
+RFC 4422 SASL June 2006
+
+
+ [DIGEST-MD5] Leach, P., C. Newman, and A. Melnikov, "Using Digest
+ Authentication as a SASL Mechanism", Work in Progress,
+ March 2006.
+
+9. Acknowledgements
+
+ This document is a revision of RFC 2222 written by John Myers.
+
+ This revision is a product of the IETF Simple Authentication and
+ Security Layer (SASL) Working Group.
+
+ The following individuals contributed significantly to this revision:
+ Abhijit Menon-Sen, Hallvard Furuseth, Jeffrey Hutzelman, John Myers,
+ Luke Howard, Magnus Nystrom, Nicolas Williams, Peter Saint-Andre, RL
+ 'Bob' Morgan, Rob Siemborski, Sam Hartman, Simon Josefsson, Tim
+ Alsop, and Tony Hansen.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 28]
+
+RFC 4422 SASL June 2006
+
+
+Appendix A. The SASL EXTERNAL Mechanism
+
+ This appendix is normative.
+
+ The EXTERNAL mechanism allows a client to request the server to use
+ credentials established by means external to the mechanism to
+ authenticate the client. The external means may be, for instance, IP
+ Security [RFC4301] or TLS [RFC4346] services. In absence of some a
+ priori agreement between the client and the server, the client cannot
+ make any assumption as to what external means the server has used to
+ obtain the client's credentials, nor make an assumption as to the
+ form of credentials. For example, the client cannot assume that the
+ server will use the credentials the client has established via TLS.
+
+A.1. EXTERNAL Technical Specification
+
+ The name of this mechanism is "EXTERNAL".
+
+ The mechanism does not provide a security layer.
+
+ The mechanism is capable of transferring an authorization identity
+ string. If empty, the client is requesting to act as the identity
+ the server has associated with the client's credentials. If non-
+ empty, the client is requesting to act as the identity represented by
+ the string.
+
+ The client is expected to send data first in the authentication
+ exchange. Where the client does not provide an initial response data
+ in its request to initiate the authentication exchange, the server is
+ to respond to the request with an empty initial challenge and then
+ the client is to provide its initial response.
+
+ The client sends the initial response containing the UTF-8 [RFC3629]
+ encoding of the requested authorization identity string. This
+ response is non-empty when the client is requesting to act as the
+ identity represented by the (non-empty) string. This response is
+ empty when the client is requesting to act as the identity the server
+ associated with its authentication credentials.
+
+ The syntax of the initial response is specified as a value of the
+ <extern-initial-resp> production detailed below using the Augmented
+ Backus-Naur Form (ABNF) [RFC4234] notation.
+
+ external-initial-resp = authz-id-string
+ authz-id-string = *( UTF8-char-no-nul )
+ UTF8-char-no-nul = UTF8-1-no-nul / UTF8-2 / UTF8-3 / UTF8-4
+ UTF8-1-no-nul = %x01-7F
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 29]
+
+RFC 4422 SASL June 2006
+
+
+ where the <UTF8-2>, <UTF8-3>, and <UTF8-4> productions are as defined
+ in [RFC3629].
+
+ There are no additional challenges and responses.
+
+ Hence, the server is to return the outcome of the authentication
+ exchange.
+
+ The exchange fails if
+
+ - the client has not established its credentials via external means,
+
+ - the client's credentials are inadequate,
+
+ - the client provided an empty authorization identity string and the
+ server is unwilling or unable to associate an authorization
+ identity with the client's credentials,
+
+ - the client provided a non-empty authorization identity string that
+ is invalid per the syntax requirements of the applicable
+ application protocol specification,
+
+ - the client provided a non-empty authorization identity string
+ representing an identity that the client is not allowed to act as,
+ or
+
+ - the server is unwilling or unable to provide service to the client
+ for any other reason.
+
+ Otherwise the exchange is successful. When indicating a successful
+ outcome, additional data is not provided.
+
+A.2. SASL EXTERNAL Examples
+
+ This section provides examples of EXTERNAL authentication exchanges.
+ The examples are intended to help the readers understand the above
+ text. The examples are not definitive. The Application
+ Configuration Access Protocol (ACAP) [RFC2244] is used in the
+ examples.
+
+ The first example shows use of EXTERNAL with an empty authorization
+ identity. In this example, the initial response is not sent in the
+ client's request to initiate the authentication exchange.
+
+ S: * ACAP (SASL "DIGEST-MD5")
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+
+
+
+Melnikov & Zeilenga Standards Track [Page 30]
+
+RFC 4422 SASL June 2006
+
+
+ S: * ACAP (SASL "DIGEST-MD5" "EXTERNAL")
+ C: a002 AUTHENTICATE "EXTERNAL"
+ S: + ""
+ C: + ""
+ S: a002 OK "Authenticated"
+
+ The second example shows use of EXTERNAL with an authorization
+ identity of "fred@example.com". In this example, the initial
+ response is sent with the client's request to initiate the
+ authentication exchange. This saves a round-trip.
+
+ S: * ACAP (SASL "DIGEST-MD5")
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "DIGEST-MD5" "EXTERNAL")
+ C: a002 AUTHENTICATE "EXTERNAL" {16+}
+ C: fred@example.com
+ S: a002 NO "Cannot assume requested authorization identity"
+
+A.3. Security Considerations
+
+ The EXTERNAL mechanism provides no security protection; it is
+ vulnerable to spoofing by either client or server, active attack, and
+ eavesdropping. It should only be used when adequate security
+ services have been established.
+
+Appendix B. Changes since RFC 2222
+
+ This appendix is non-normative.
+
+ The material in RFC 2222 was significantly rewritten in the
+ production of this document.
+
+ RFC 2222, by not stating that the authorization identity string was a
+ string of Unicode characters, let alone character data, implied that
+ the authorization identity string was a string of octets.
+
+ - The authorization identity string is now defined as a string of
+ Unicode characters. The NUL (U+0000) character is prohibited.
+ While protocol specifications are responsible for defining the
+ authorization identity form, as well as the Unicode string syntax
+ and related semantics, mechanism specifications are responsible
+ for defining how the Unicode string is carried in the
+ authentication exchange.
+
+ - Deleted "If so, when the client does not send data first, the
+ initial challenge MUST be specified as being an empty challenge."
+
+
+
+Melnikov & Zeilenga Standards Track [Page 31]
+
+RFC 4422 SASL June 2006
+
+
+ The following technical change was made to the EXTERNAL mechanism:
+
+ - The authorization identity string is to be UTF-8 encoded.
+
+ Note that protocol and mechanism specification requirements have
+ been significantly tightened. Existing protocol and mechanism
+ specifications will need to be updated to meet these requirements.
+
+Editors' Addresses
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex,
+ TW12 2BX, United Kingdom
+
+ EMail: Alexey.Melnikov@isode.com
+ URI: http://www.melnikov.ca/
+
+
+ Kurt D. Zeilenga
+ OpenLDAP Foundation
+
+ EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 32]
+
+RFC 4422 SASL June 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Zeilenga Standards Track [Page 33]
+
diff --git a/imap/docs/rfc/rfc4466.txt b/imap/docs/rfc/rfc4466.txt
new file mode 100644
index 00000000..dfde1685
--- /dev/null
+++ b/imap/docs/rfc/rfc4466.txt
@@ -0,0 +1,955 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 4466 Isode Ltd.
+Updates: 2088, 2342, 3501, 3502, 3516 C. Daboo
+Category: Standards Track April 2006
+
+
+ Collected Extensions to IMAP4 ABNF
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ Over the years, many documents from IMAPEXT and LEMONADE working
+ groups, as well as many individual documents, have added syntactic
+ extensions to many base IMAP commands described in RFC 3501. For
+ ease of reference, this document collects most of such ABNF changes
+ in one place.
+
+ This document also suggests a set of standard patterns for adding
+ options and extensions to several existing IMAP commands defined in
+ RFC 3501. The patterns provide for compatibility between existing
+ and future extensions.
+
+ This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+ It also includes part of the errata to RFC 3501. This document
+ doesn't specify any semantic changes to the listed RFCs.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 1]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 1.1. Purpose of This Document ...................................2
+ 1.2. Conventions Used in This Document ..........................3
+ 2. IMAP ABNF Extensions ............................................3
+ 2.1. Optional Parameters with the SELECT/EXAMINE Commands .......3
+ 2.2. Extended CREATE Command ....................................4
+ 2.3. Extended RENAME Command ....................................5
+ 2.4. Extensions to FETCH and UID FETCH Commands .................6
+ 2.5. Extensions to STORE and UID STORE Commands .................6
+ 2.6. Extensions to SEARCH Command ...............................7
+ 2.6.1. Extended SEARCH Command .............................7
+ 2.6.2. ESEARCH untagged response ...........................8
+ 2.7. Extensions to APPEND Command ...............................8
+ 3. Formal Syntax ...................................................9
+ 4. Security Considerations ........................................14
+ 5. Normative References ...........................................15
+ 6. Acknowledgements ...............................................15
+
+1. Introduction
+
+1.1. Purpose of This Document
+
+ This document serves several purposes:
+
+ 1. rationalize and generalize ABNF for some existing IMAP
+ extensions;
+ 2. collect the ABNF in one place in order to minimize cross
+ references between documents;
+ 3. define building blocks for future extensions so that they can
+ be used together in a compatible way.
+
+ It is expected that a future revision of this document will be
+ incorporated into a revision of RFC 3501.
+
+ This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+ It also includes part of the errata to RFC 3501. This document
+ doesn't specify any semantic changes to the listed RFCs.
+
+ The ABNF in section 6 of RFC 2342 got rewritten to conform to the
+ ABNF syntax as defined in RFC 4234 and to reference new non-terminals
+ from RFC 3501. It was also restructured to allow for better
+ readability. There were no changes "on the wire".
+
+ Section 2 extends ABNF for SELECT, EXAMINE, CREATE, RENAME, FETCH/UID
+ FETCH, STORE/UID STORE, SEARCH, and APPEND commands in a consistent
+ manner. Extensions to all the commands but APPEND have the same
+
+
+
+Melnikov & Daboo Standards Track [Page 2]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ structure. Extensibility for the APPEND command was done slightly
+ differently in order to preserve backward compatibility with existing
+ extensions.
+
+ Section 2 also defines a new ESEARCH response, whose purpose is to
+ define a better version of the SEARCH response defined in RFC 3501.
+
+ Section 3 defines the collected ABNF that replaces pieces of ABNF in
+ the aforementioned RFCs. The collected ABNF got generalized to allow
+ for easier future extensibility.
+
+1.2. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as defined in "Key words for
+ use in RFCs to Indicate Requirement Levels" [KEYWORDS].
+
+2. IMAP ABNF Extensions
+
+ This section is not normative. It provides some background on the
+ intended use of different extensions and it gives some guidance about
+ how future extensions should extend the described commands.
+
+2.1. Optional Parameters with the SELECT/EXAMINE Commands
+
+ This document adds the ability to include one or more parameters with
+ the IMAP SELECT (section 6.3.1 of [IMAP4]) or EXAMINE (section 6.3.2
+ of [IMAP4]) commands, to turn on or off certain standard behaviors,
+ or to add new optional behaviors required for a particular extension.
+
+ There are two possible modes of operation:
+
+ o A global state change where a single use of the optional parameter
+ will affect the session state from that time on, irrespective of
+ subsequent SELECT/EXAMINE commands.
+
+ o A per-mailbox state change that will affect the session only for
+ the duration of the new selected state. A subsequent
+ SELECT/EXAMINE without the optional parameter will cancel its
+ effect for the newly selected mailbox.
+
+ Optional parameters to the SELECT or EXAMINE commands are added as a
+ parenthesized list of attribute/value pairs, and appear after the
+ mailbox name in the standard SELECT or EXAMINE command. The order of
+ individual parameters is arbitrary. A parameter value is optional
+
+
+
+Melnikov & Daboo Standards Track [Page 3]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ and may consist of atoms, strings, or lists in a specific order. If
+ the parameter value is present, it always appears in parentheses (*).
+ Any parameter not defined by extensions that the server supports must
+ be rejected with a BAD response.
+
+ Example:
+
+ C: a SELECT INBOX (ANNOTATE)
+ S: ...
+ S: a OK SELECT complete
+
+ In the above example, a single parameter is used with the SELECT
+ command.
+
+ Example:
+
+ C: a EXAMINE INBOX (ANNOTATE RESPONSES ("UID Responses")
+ CONDSTORE)
+ S: ...
+ S: a OK EXAMINE complete
+
+ In the above example, three parameters are used with the EXAMINE
+ command. The second parameter consists of two items: an atom
+ "RESPONSES" followed by a quoted string.
+
+ Example:
+
+ C: a SELECT INBOX (BLURDYBLOOP)
+ S: a BAD Unknown parameter in SELECT command
+
+ In the above example, a parameter not supported by the server is
+ used. This results in the BAD response from the server.
+
+ (*) - if a parameter has a mandatory value, which can always be
+ represented as a number or a sequence-set, the parameter value does
+ not need the enclosing (). See ABNF for more details.
+
+2.2. Extended CREATE Command
+
+ Arguments: mailbox name
+ OPTIONAL list of CREATE parameters
+
+ Responses: no specific responses for this command
+
+ Result: OK - create completed
+ NO - create failure: cannot create mailbox with
+ that name
+ BAD - argument(s) invalid
+
+
+
+Melnikov & Daboo Standards Track [Page 4]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ This document adds the ability to include one or more parameters with
+ the IMAP CREATE command (see section 6.3.3 of [IMAP4]), to turn on or
+ off certain standard behaviors, or to add new optional behaviors
+ required for a particular extension. No CREATE parameters are
+ defined in this document.
+
+ Optional parameters to the CREATE command are added as a
+ parenthesized list of attribute/value pairs after the mailbox name.
+ The order of individual parameters is arbitrary. A parameter value
+ is optional and may consist of atoms, strings, or lists in a specific
+ order. If the parameter value is present, it always appears in
+ parentheses (*). Any parameter not defined by extensions that the
+ server supports must be rejected with a BAD response.
+
+ (*) - if a parameter has a mandatory value, which can always be
+ represented as a number or a sequence-set, the parameter value does
+ not need the enclosing (). See ABNF for more details.
+
+2.3. Extended RENAME Command
+
+ Arguments: existing mailbox name
+ new mailbox name
+ OPTIONAL list of RENAME parameters
+
+ Responses: no specific responses for this command
+
+ Result: OK - rename completed
+ NO - rename failure: cannot rename mailbox with
+ that name, cannot rename to mailbox with
+ that name, etc.
+ BAD - argument(s) invalid
+
+ This document adds the ability to include one or more parameters with
+ the IMAP RENAME command (see section 6.3.5 of [IMAP4]), to turn on or
+ off certain standard behaviors, or to add new optional behaviors
+ required for a particular extension. No RENAME parameters are
+ defined in this document.
+
+ Optional parameters to the RENAME command are added as a
+ parenthesized list of attribute/value pairs after the new mailbox
+ name. The order of individual parameters is arbitrary. A parameter
+ value is optional and may consist of atoms, strings, or lists in a
+ specific order. If the parameter value is present, it always appears
+ in parentheses (*). Any parameter not defined by extensions that the
+ server supports must be rejected with a BAD response.
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 5]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ (*) - if a parameter has a mandatory value, which can always be
+ represented as a number or a sequence-set, the parameter value does
+ not need the enclosing (). See ABNF for more details.
+
+2.4. Extensions to FETCH and UID FETCH Commands
+
+ Arguments: sequence set
+ message data item names or macro
+ OPTIONAL fetch modifiers
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - fetch completed
+ NO - fetch error: cannot fetch that data
+ BAD - command unknown or arguments invalid
+
+ This document extends the syntax of the FETCH and UID FETCH commands
+ (see section 6.4.5 of [IMAP4]) to include optional FETCH modifiers.
+ No fetch modifiers are defined in this document.
+
+ The order of individual modifiers is arbitrary. Each modifier is an
+ attribute/value pair. A modifier value is optional and may consist
+ of atoms and/or strings and/or lists in a specific order. If the
+ modifier value is present, it always appears in parentheses (*). Any
+ modifiers not defined by extensions that the server supports must be
+ rejected with a BAD response.
+
+ (*) - if a modifier has a mandatory value, which can always be
+ represented as a number or a sequence-set, the modifier value does
+ not need the enclosing (). See ABNF for more details.
+
+2.5. Extensions to STORE and UID STORE Commands
+
+ Arguments: message set
+ OPTIONAL store modifiers
+ message data item name
+ value for message data item
+
+ Responses: untagged responses: FETCH
+
+ Result: OK - store completed
+ NO - store error: cannot store that data
+ BAD - command unknown or arguments invalid
+
+ This document extends the syntax of the STORE and UID STORE commands
+ (see section 6.4.6 of [IMAP4]) to include optional STORE modifiers.
+ No store modifiers are defined in this document.
+
+
+
+
+Melnikov & Daboo Standards Track [Page 6]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ The order of individual modifiers is arbitrary. Each modifier is an
+ attribute/value pair. A modifier value is optional and may consist
+ of atoms and/or strings and/or lists in a specific order. If the
+ modifier value is present, it always appears in parentheses (*). Any
+ modifiers not defined by extensions that the server supports must be
+ rejected with a BAD response.
+
+ (*) - if a modifier has a mandatory value, which can always be
+ represented as a number or a sequence-set, the modifier value does
+ not need the enclosing (). See ABNF for more details.
+
+2.6. Extensions to SEARCH Command
+
+2.6.1. Extended SEARCH Command
+
+ Arguments: OPTIONAL result specifier
+ OPTIONAL [CHARSET] specification
+ searching criteria (one or more)
+
+ Responses: REQUIRED untagged response: SEARCH (*)
+
+ Result: OK - search completed
+ NO - search error: cannot search that [CHARSET] or
+ criteria
+ BAD - command unknown or arguments invalid
+
+ This section updates definition of the SEARCH command described in
+ section 6.4.4 of [IMAP4].
+
+ The SEARCH command is extended to allow for result options. This
+ document does not define any result options.
+
+ The order of individual options is arbitrary. Individual options may
+ contain parameters enclosed in parentheses (**). If an option has
+ parameters, they consist of atoms and/or strings and/or lists in a
+ specific order. Any options not defined by extensions that the
+ server supports must be rejected with a BAD response.
+
+ (*) - An extension to the SEARCH command may require another untagged
+ response, or no untagged response to be returned. Section 2.6.2
+ defines a new ESEARCH untagged response that replaces the SEARCH
+ untagged response. Note that for a given extended SEARCH command the
+ SEARCH and ESEARCH responses SHOULD be mutually exclusive, i.e., only
+ one of them should be returned.
+
+ (**) - if an option has a mandatory parameter, which can always be
+ represented as a number or a sequence-set, the option parameter does
+ not need the enclosing (). See ABNF for more details.
+
+
+
+Melnikov & Daboo Standards Track [Page 7]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+2.6.2. ESEARCH untagged response
+
+ Contents: one or more search-return-data pairs
+
+ The ESEARCH response SHOULD be sent as a result of an extended SEARCH
+ or UID SEARCH command specified in section 2.6.1.
+
+ The ESEARCH response starts with an optional search correlator. If
+ it is missing, then the response was not caused by a particular IMAP
+ command, whereas if it is present, it contains the tag of the command
+ that caused the response to be returned.
+
+ The search correlator is followed by an optional UID indicator. If
+ this indicator is present, all data in the ESEARCH response refers to
+ UIDs, otherwise all returned data refers to message numbers.
+
+ The rest of the ESEARCH response contains one or more search data
+ pairs. Each pair starts with unique return item name, followed by a
+ space and the corresponding data. Search data pairs may be returned
+ in any order. Unless specified otherwise by an extension, any return
+ item name SHOULD appear only once in an ESEARCH response.
+
+ Example: S: * ESEARCH UID COUNT 5 ALL 4:19,21,28
+
+ Example: S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28
+
+ Example: S: * ESEARCH COUNT 5 ALL 1:17,21
+
+2.7. Extensions to APPEND Command
+
+ The IMAP BINARY extension [BINARY] extends the APPEND command to
+ allow a client to append data containing NULs by using the <literal8>
+ syntax. The ABNF was rewritten to allow for easier extensibility by
+ IMAP extensions. This document hasn't specified any semantical
+ changes to the [BINARY] extension.
+
+ In addition, the non-terminal "literal8" defined in [BINARY] got
+ extended to allow for non-synchronizing literals if both [BINARY] and
+ [LITERAL+] extensions are supported by the server.
+
+ The IMAP MULTIAPPEND extension [MULTIAPPEND] extends the APPEND
+ command to allow a client to append multiple messages atomically.
+ This document defines a common syntax for the APPEND command that
+ takes into consideration syntactic extensions defined by both
+ [BINARY] and [MULTIAPPEND] extensions.
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 8]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+3. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ Non-terminals referenced but not defined below are as defined by
+ [IMAP4].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of uppercase or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ append = "APPEND" SP mailbox 1*append-message
+ ;; only a single append-message may appear
+ ;; if MULTIAPPEND [MULTIAPPEND] capability
+ ;; is not present
+
+ append-message = append-opts SP append-data
+
+ append-ext = append-ext-name SP append-ext-value
+ ;; This non-terminal define extensions to
+ ;; to message metadata.
+
+ append-ext-name = tagged-ext-label
+
+ append-ext-value= tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+
+ append-data = literal / literal8 / append-data-ext
+
+ append-data-ext = tagged-ext
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions,
+ ;; i.e., a mandatory label followed
+ ;; by parameters.
+
+ append-opts = [SP flag-list] [SP date-time] *(SP append-ext)
+ ;; message metadata
+
+ charset = atom / quoted
+ ;; Exact syntax is defined in [CHARSET].
+
+ create = "CREATE" SP mailbox
+ [create-params]
+ ;; Use of INBOX gives a NO error.
+
+
+
+Melnikov & Daboo Standards Track [Page 9]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ create-params = SP "(" create-param *( SP create-param) ")"
+
+ create-param-name = tagged-ext-label
+
+ create-param = create-param-name [SP create-param-value]
+
+ create-param-value= tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+
+ esearch-response = "ESEARCH" [search-correlator] [SP "UID"]
+ *(SP search-return-data)
+ ;; Note that SEARCH and ESEARCH responses
+ ;; SHOULD be mutually exclusive,
+ ;; i.e., only one of the response types
+ ;; should be
+ ;; returned as a result of a command.
+
+
+ examine = "EXAMINE" SP mailbox [select-params]
+ ;; modifies the original IMAP EXAMINE command
+ ;; to accept optional parameters
+
+ fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" /
+ "FAST" / fetch-att /
+ "(" fetch-att *(SP fetch-att) ")")
+ [fetch-modifiers]
+ ;; modifies the original IMAP4 FETCH command to
+ ;; accept optional modifiers
+
+ fetch-modifiers = SP "(" fetch-modifier *(SP fetch-modifier) ")"
+
+ fetch-modifier = fetch-modifier-name [ SP fetch-modif-params ]
+
+ fetch-modif-params = tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+ fetch-modifier-name = tagged-ext-label
+
+ literal8 = "~{" number ["+"] "}" CRLF *OCTET
+ ;; A string that might contain NULs.
+ ;; <number> represents the number of OCTETs
+ ;; in the response string.
+ ;; The "+" is only allowed when both LITERAL+ and
+ ;; BINARY extensions are supported by the server.
+
+
+
+
+Melnikov & Daboo Standards Track [Page 10]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ mailbox-data =/ Namespace-Response /
+ esearch-response
+
+ Namespace = nil / "(" 1*Namespace-Descr ")"
+
+ Namespace-Command = "NAMESPACE"
+
+ Namespace-Descr = "(" string SP
+ (DQUOTE QUOTED-CHAR DQUOTE / nil)
+ *(Namespace-Response-Extension) ")"
+
+ Namespace-Response-Extension = SP string SP
+ "(" string *(SP string) ")"
+
+ Namespace-Response = "NAMESPACE" SP Namespace
+ SP Namespace SP Namespace
+ ;; This response is currently only allowed
+ ;; if the IMAP server supports [NAMESPACE].
+ ;; The first Namespace is the Personal Namespace(s)
+ ;; The second Namespace is the Other Users' Namespace(s)
+ ;; The third Namespace is the Shared Namespace(s)
+
+ rename = "RENAME" SP mailbox SP mailbox
+ [rename-params]
+ ;; Use of INBOX as a destination gives
+ ;; a NO error, unless rename-params
+ ;; is not empty.
+
+ rename-params = SP "(" rename-param *( SP rename-param) ")"
+
+ rename-param = rename-param-name [SP rename-param-value]
+
+ rename-param-name = tagged-ext-label
+
+ rename-param-value= tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+
+ response-data = "*" SP response-payload CRLF
+
+ response-payload= resp-cond-state / resp-cond-bye /
+ mailbox-data / message-data / capability-data
+
+ search = "SEARCH" [search-return-opts]
+ SP search-program
+
+ search-correlator = SP "(" "TAG" SP tag-string ")"
+
+
+
+Melnikov & Daboo Standards Track [Page 11]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ search-program = ["CHARSET" SP charset SP]
+ search-key *(SP search-key)
+ ;; CHARSET argument to SEARCH MUST be
+ ;; registered with IANA.
+
+ search-return-data = search-modifier-name SP search-return-value
+ ;; Note that not every SEARCH return option
+ ;; is required to have the corresponding
+ ;; ESEARCH return data.
+
+ search-return-opts = SP "RETURN" SP "(" [search-return-opt
+ *(SP search-return-opt)] ")"
+
+ search-return-opt = search-modifier-name [SP search-mod-params]
+
+ search-return-value = tagged-ext-val
+ ;; Data for the returned search option.
+ ;; A single "nz-number"/"number" value
+ ;; can be returned as an atom (i.e., without
+ ;; quoting). A sequence-set can be returned
+ ;; as an atom as well.
+
+ search-modifier-name = tagged-ext-label
+
+ search-mod-params = tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+
+ select = "SELECT" SP mailbox [select-params]
+ ;; modifies the original IMAP SELECT command to
+ ;; accept optional parameters
+
+ select-params = SP "(" select-param *(SP select-param) ")"
+
+ select-param = select-param-name [SP select-param-value]
+ ;; a parameter to SELECT may contain one or
+ ;; more atoms and/or strings and/or lists.
+
+ select-param-name= tagged-ext-label
+
+ select-param-value= tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+
+ status-att-list = status-att-val *(SP status-att-val)
+ ;; Redefines status-att-list from RFC 3501.
+
+
+
+Melnikov & Daboo Standards Track [Page 12]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ ;; status-att-val is defined in RFC 3501 errata
+
+ status-att-val = ("MESSAGES" SP number) /
+ ("RECENT" SP number) /
+ ("UIDNEXT" SP nz-number) /
+ ("UIDVALIDITY" SP nz-number) /
+ ("UNSEEN" SP number)
+ ;; Extensions to the STATUS responses
+ ;; should extend this production.
+ ;; Extensions should use the generic
+ ;; syntax defined by tagged-ext.
+
+ store = "STORE" SP sequence-set [store-modifiers]
+ SP store-att-flags
+ ;; extend [IMAP4] STORE command syntax
+ ;; to allow for optional store-modifiers
+
+ store-modifiers = SP "(" store-modifier *(SP store-modifier)
+ ")"
+
+ store-modifier = store-modifier-name [SP store-modif-params]
+
+ store-modif-params = tagged-ext-val
+ ;; This non-terminal shows recommended syntax
+ ;; for future extensions.
+
+ store-modifier-name = tagged-ext-label
+
+ tag-string = string
+ ;; tag of the command that caused
+ ;; the ESEARCH response, sent as
+ ;; a string.
+
+ tagged-ext = tagged-ext-label SP tagged-ext-val
+ ;; recommended overarching syntax for
+ ;; extensions
+
+ tagged-ext-label = tagged-label-fchar *tagged-label-char
+ ;; Is a valid RFC 3501 "atom".
+
+ tagged-label-fchar = ALPHA / "-" / "_" / "."
+
+ tagged-label-char = tagged-label-fchar / DIGIT / ":"
+
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 13]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+ tagged-ext-comp = astring /
+ tagged-ext-comp *(SP tagged-ext-comp) /
+ "(" tagged-ext-comp ")"
+ ;; Extensions that follow this general
+ ;; syntax should use nstring instead of
+ ;; astring when appropriate in the context
+ ;; of the extension.
+ ;; Note that a message set or a "number"
+ ;; can always be represented as an "atom".
+ ;; An URL should be represented as
+ ;; a "quoted" string.
+
+ tagged-ext-simple = sequence-set / number
+
+ tagged-ext-val = tagged-ext-simple /
+ "(" [tagged-ext-comp] ")"
+
+4. Security Considerations
+
+ This document updates ABNF in RFCs 2088, 2342, 3501, 3502, and 3516.
+ The updated documents must be consulted for security considerations
+ for the extensions that they define.
+
+ As a protocol gets more complex, parser bugs become more common
+ including buffer overflow, denial of service, and other common
+ security coding errors. To the extent that this document makes the
+ parser more complex, it makes this situation worse. To the extent
+ that this document makes the parser more consistent and thus simpler,
+ the situation is improved. The impact will depend on how many
+ deployed IMAP extensions are consistent with this document.
+ Implementers are encouraged to take care of these issues when
+ extending existing implementations. Future IMAP extensions should
+ strive for consistency and simplicity to the greatest extent
+ possible.
+
+ Extensions to IMAP commands that are permitted in NOT AUTHENTICATED
+ state are more sensitive to these security issues due to the larger
+ possible attacker community prior to authentication, and the fact
+ that some IMAP servers run with elevated privileges in that state.
+ This document does not extend any commands permitted in NOT
+ AUTHENTICATED state. Future IMAP extensions to commands permitted in
+ NOT AUTHENTICATED state should favor simplicity over consistency or
+ extensibility.
+
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 14]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+5. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [ABNF] Crocker, D., Ed., and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+ [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration
+ Procedures", BCP 19, RFC 2978, October 2000.
+
+ [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ MULTIAPPEND Extension", RFC 3502, March 2003.
+
+ [NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
+ May 1998.
+
+ [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC
+ 2088, January 1997.
+
+ [BINARY] Nerenberg, L., "IMAP4 Binary Content Extension", RFC
+ 3516, April 2003.
+
+6. Acknowledgements
+
+ This documents is based on ideas proposed by Pete Resnick, Mark
+ Crispin, Ken Murchison, Philip Guenther, Randall Gellens, and Lyndon
+ Nerenberg.
+
+ However, all errors and omissions must be attributed to the authors
+ of the document.
+
+ Thanks to Philip Guenther, Dave Cridland, Mark Crispin, Chris Newman,
+ Elwyn Davies, and Barry Leiba for comments and corrections.
+
+ literal8 syntax was taken from RFC 3516.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 15]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+Authors' Addresses
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex, TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Cyrus Daboo
+
+ EMail: cyrus@daboo.name
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 16]
+
+RFC 4466 Collected Extensions to IMAP4 ABNF April 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Daboo Standards Track [Page 17]
+
diff --git a/imap/docs/rfc/rfc4467.txt b/imap/docs/rfc/rfc4467.txt
new file mode 100644
index 00000000..83b6516a
--- /dev/null
+++ b/imap/docs/rfc/rfc4467.txt
@@ -0,0 +1,1011 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 4467 University of Washington
+Updates: 3501 May 2006
+Category: Standards Track
+
+
+ Internet Message Access Protocol (IMAP) - URLAUTH Extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ This document describes the URLAUTH extension to the Internet Message
+ Access Protocol (IMAP) (RFC 3501) and the IMAP URL Scheme (IMAPURL)
+ (RFC 2192). This extension provides a means by which an IMAP client
+ can use URLs carrying authorization to access limited message data on
+ the IMAP server.
+
+ An IMAP server that supports this extension indicates this with a
+ capability name of "URLAUTH".
+
+1. Introduction
+
+ In [IMAPURL], a URL of the form imap://fred@example.com/INBOX/;uid=20
+ requires authorization as userid "fred". However, [IMAPURL] implies
+ that it only supports authentication and confuses the concepts of
+ authentication and authorization.
+
+ The URLAUTH extension defines an authorization mechanism for IMAP
+ URLs to replace [IMAPURL]'s authentication-only mechanism. URLAUTH
+ conveys authorization in the URL string itself and reuses a portion
+ of the syntax of the [IMAPURL] authentication mechanism to convey the
+ authorization identity (which also defines the default namespace in
+ [IMAP]).
+
+ The URLAUTH extension provides a means by which an authorized user of
+ an IMAP server can create URLAUTH-authorized IMAP URLs. A URLAUTH-
+ authorized URL conveys authorization (not authentication) to the data
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ addressed by that URL. This URL can be used in another IMAP session
+ to access specific content on the IMAP server, without otherwise
+ providing authorization to any other data (such as other data in the
+ mailbox specified in the URL) owned by the authorizing user.
+
+ Conceptually, a URLAUTH-authorized URL can be thought of as a "pawn
+ ticket" that carries no authentication information and can be
+ redeemed by whomever presents it. However, unlike a pawn ticket,
+ URLAUTH has optional mechanisms to restrict the usage of a URLAUTH-
+ authorized URL. Using these mechanisms, URLAUTH-authorized URLs can
+ be usable by:
+
+ . anonymous (the "pawn ticket" model)
+ . authenticated users only
+ . a specific authenticated user only
+ . message submission acting on behalf of a specific user only
+
+ There is also a mechanism for expiration.
+
+ A URLAUTH-authorized URL can be used in the argument to the BURL
+ command in message composition, as described in [BURL], for such
+ purposes as allowing a client (with limited memory or other
+ resources) to submit a message forward or to resend from an IMAP
+ mailbox without requiring the client to fetch that message data.
+
+ The URLAUTH is generated using an authorization mechanism name and an
+ authorization token, which is generated using a secret mailbox access
+ key. An IMAP client can request that the server generate and assign
+ a new mailbox access key (thus effectively revoking all current URLs
+ using URLAUTH with the old mailbox access key) but cannot set the
+ mailbox access key to a key of its own choosing.
+
+1.1. Conventions Used in this Document
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as defined in [KEYWORDS].
+
+ The formal syntax uses the Augmented Backus-Naur Form (ABNF) notation
+ including the core rules defined in Appendix A of [ABNF].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively. If a single "C:" or "S:" label applies to
+ multiple lines, then the line breaks between those lines are for
+ editorial clarity only and are not part of the actual protocol
+ exchange.
+
+
+
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+2. Concepts
+
+2.1. URLAUTH
+
+ The URLAUTH is a component, appended at the end of a URL, that
+ conveys authorization to access the data addressed by that URL. It
+ contains an authorized access identifier, an authorization mechanism
+ name, and an authorization token. The authorization token is
+ generated from the URL, the authorized access identifier, the
+ authorization mechanism name, and a mailbox access key.
+
+2.2. Mailbox Access Key
+
+ The mailbox access key is a random string with at least 128 bits of
+ entropy. It is generated by software (not by the human user) and
+ MUST be unpredictable.
+
+ Each user has a table of mailboxes and an associated mailbox access
+ key for each mailbox. Consequently, the mailbox access key is per-
+ user and per-mailbox. In other words, two users sharing the same
+ mailbox each have a different mailbox access key for that mailbox,
+ and each mailbox accessed by a single user also has a different
+ mailbox access key.
+
+2.3. Authorized Access Identifier
+
+ The authorized access identifier restricts use of the URLAUTH
+ authorized URL to certain users authorized on the server, as
+ described in section 3.
+
+2.4. Authorization Mechanism
+
+ The authorization mechanism is the algorithm by which the URLAUTH is
+ generated and subsequently verified, using the mailbox access key.
+
+2.4.1. INTERNAL Authorization Mechanism
+
+ This specification defines the INTERNAL mechanism, which uses a token
+ generation algorithm of the server's choosing and does not involve
+ disclosure of the mailbox access key to the client.
+
+ Note: The token generation algorithm chosen by the server
+ implementation should be modern and reasonably secure. At the
+ time of the writing of this document, an [HMAC] such as HMAC-SHA1
+ is recommended.
+
+
+
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ If it becomes necessary to change the token generation algorithm
+ of the INTERNAL mechanism (e.g., because an attack against the
+ current algorithm has been discovered), all currently existing
+ URLAUTH-authorized URLs are invalidated by the change in
+ algorithm. Since this would be an unpleasant surprise to
+ applications that depend upon the validity of a URLAUTH-authorized
+ URL, and there is no good way to do a bulk update of existing
+ deployed URLs, it is best to avoid this situation by using a
+ secure algorithm as opposed to one that is "good enough".
+
+ Server implementations SHOULD consider the possibility of changing
+ the algorithm. In some cases, it may be desirable to implement
+ the change of algorithm in a way that newly-generated tokens use
+ the new algorithm, but that for a limited period of time tokens
+ using either the new or old algorithm can be validated.
+ Consequently, the server SHOULD incorporate some means of
+ identifying the token generation algorithm within the token.
+
+ Although this specification is extensible for other mechanisms, none
+ are defined in this document. In addition to the mechanism name
+ itself, other mechanisms may have mechanism-specific data, which is
+ to be interpreted according to the definition of that mechanism.
+
+2.5. Authorization Token
+
+ The authorization token is a deterministic string of at least 128
+ bits that an entity with knowledge of the secret mailbox access key
+ and URL authorization mechanism can use to verify the URL.
+
+3. IMAP URL Extensions
+
+ [IMAPURL] is extended by allowing the addition of
+ ";EXPIRE=<datetime>" and ";URLAUTH=<access>:<mech>:<token>" to IMAP
+ URLs that refer to a specific message or message parts.
+
+ The URLAUTH is comprised of ";URLAUTH=<access>:<mech>:<token>" and
+ MUST be at the end of the URL.
+
+ URLAUTH does not apply to, and MUST NOT be used with, any IMAP URL
+ that refers to an entire IMAP server, a list of mailboxes, an entire
+ IMAP mailbox, or IMAP search results.
+
+ When ";EXPIRE=<datetime>" is used, this indicates the latest date and
+ time that the URL is valid. After that date and time, the URL has
+ expired, and server implementations MUST reject the URL. If
+ ";EXPIRE=<datetime>" is not used, the URL has no expiration, but
+ still can be revoked as discussed below.
+
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ The URLAUTH takes the form ";URLAUTH=<access>:<mech>:<token>". It is
+ composed of three parts. The <access> portion provides the
+ authorized access identifiers, which may constrain the operations and
+ users that are permitted to use this URL. The <mech> portion
+ provides the authorization mechanism used by the IMAP server to
+ generate the authorization token that follows. The <token> portion
+ provides the authorization token.
+
+ The "submit+" access identifier prefix, followed by a userid,
+ indicates that only a userid authorized as a message submission
+ entity on behalf of the specified userid is permitted to use this
+ URL. The IMAP server does not validate the specified userid but does
+ validate that the IMAP session has an authorization identity that is
+ authorized as a message submission entity. The authorized message
+ submission entity MUST validate the userid prior to contacting the
+ IMAP server.
+
+ The "user+" access identifier prefix, followed by a userid, indicates
+ that use of this URL is limited to IMAP sessions that are logged in
+ as the specified userid (that is, have authorization identity as that
+ userid).
+
+ Note: If a SASL mechanism that provides both authorization and
+ authentication identifiers is used to authenticate to the IMAP
+ server, the "user+" access identifier MUST match the authorization
+ identifier.
+
+ The "authuser" access identifier indicates that use of this URL is
+ limited to IMAP sessions that are logged in as an authorized user
+ (that is, have authorization identity as an authorized user) of that
+ IMAP server. Use of this URL is prohibited to anonymous IMAP
+ sessions.
+
+ The "anonymous" access identifier indicates that use of this URL is
+ not restricted by session authorization identity; that is, any IMAP
+ session in authenticated or selected state (as defined in [IMAP]),
+ including anonymous sessions, may issue a URLFETCH using this URL.
+
+ The authorization token is represented as an ASCII-encoded
+ hexadecimal string, which is used to authorize the URL. The length
+ and the calculation of the authorization token depends upon the
+ mechanism used; but, in all cases, the authorization token is at
+ least 128 bits (and therefore at least 32 hexadecimal digits).
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+4. Discussion of URLAUTH Authorization Issues
+
+ In [IMAPURL], the userid before the "@" in the URL has two purposes:
+
+ 1) It provides context for user-specific mailbox paths such as
+ "INBOX".
+
+ 2) It specifies that resolution of the URL requires logging in as
+ that user and limits use of that URL to only that user.
+
+ An obvious limitation of using the same field for both purposes is
+ that the URL can only be resolved by the mailbox owner.
+
+ URLAUTH overrides the second purpose of the userid in the IMAP URL
+ and by default permits the URL to be resolved by any user permitted
+ by the access identifier.
+
+ The "user+<userid>" access identifier limits resolution of that URL
+ to a particular userid, whereas the "submit+<userid>" access
+ identifier is more general and simply requires that the session be
+ authorized by a user that has been granted a "submit" role within the
+ authentication system. Use of either of these access identifiers
+ makes it impossible for an attacker, spying on the session, to use
+ the same URL, either directly or by submission to a message
+ submission entity.
+
+ The "authuser" and "anonymous" access identifiers do not have this
+ level of protection and should be used with caution. These access
+ identifiers are primarily useful for public export of data from an
+ IMAP server, without requiring that it be copied to a web or
+ anonymous FTP server. Refer to the Security Considerations for more
+ details.
+
+5. Generation of URLAUTH-Authorized URLs
+
+ A URLAUTH-authorized URL is generated from an initial URL as follows:
+
+ An initial URL is built, ending with ";URLAUTH=<access>" but without
+ the ":<mech>:<token>" components. An authorization mechanism is
+ selected and used to calculate the authorization token, with the
+ initial URL as the data and a secret known to the IMAP server as the
+ key. The URLAUTH-authorized URL is generated by taking the initial
+ URL and appending ":", the URL authorization mechanism name, ":", and
+ the ASCII-encoded hexadecimal representation of the authorization
+ token.
+
+
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ Note: ASCII-encoded hexadecimal is used instead of BASE64 because
+ a BASE64 representation may have "=" padding characters, which
+ would be problematic in a URL.
+
+ In the INTERNAL mechanism, the mailbox access key for that mailbox is
+ the secret known to the IMAP server, and a server-selected algorithm
+ is used as described in section 2.4.1.
+
+6. Validation of URLAUTH-authorized URLs
+
+ A URLAUTH-authorized URL is validated as follows:
+
+ The URL is split at the ":" that separates "<access>" from
+ "<mech>:<token>" in the ";URLAUTH=<access>:<mech>:<token>" portion of
+ the URL. The "<mech>:<token>" portion is first parsed and saved as
+ the authorization mechanism and the authorization token. The URL is
+ truncated, discarding the ":" described above, to create a "rump URL"
+ (the URL minus the ":" and the "<mech>:<token>" portion). The rump
+ URL is then analyzed to identify the mailbox.
+
+ If the mailbox cannot be identified, an authorization token is
+ calculated on the rump URL, using random "plausible" keys (selected
+ by the server) as needed, before returning a validation failure.
+ This prevents timing attacks aimed at identifying mailbox names.
+
+ If the mailbox can be identified, the authorization token is
+ calculated on the rump URL and a secret known to the IMAP server
+ using the given URL authorization mechanism. Validation is
+ successful if, and only if, the calculated authorization token for
+ that mechanism matches the authorization token supplied in
+ ";URLAUTH=<access>:<mech>:<token>".
+
+ Removal of the ":<mech>:<token>" portion of the URL MUST be the only
+ operation applied to the URLAUTH-authorized URL to get the rump URL.
+ In particular, URL percent escape decoding and case-folding
+ (including to the domain part of the URL) MUST NOT occur.
+
+ In the INTERNAL mechanism, the mailbox access key for that mailbox is
+ used as the secret known to the IMAP server, and the same server-
+ selected algorithm used for generating URLs is used to calculate the
+ authorization token for verification.
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 7]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+7. Additional Commands
+
+ These commands are extensions to the [IMAP] base protocol.
+
+ The section headings of these commands are intended to correspond
+ with where they would be located in the base protocol document if
+ they were part of that document.
+
+BASE.6.3.RESETKEY. RESETKEY Command
+
+ Arguments: optional mailbox name
+ optional mechanism name(s)
+
+ Responses: none other than in result
+
+ Result: OK - RESETKEY completed, URLMECH containing new data
+ NO - RESETKEY error: can't change key of that mailbox
+ BAD - command unknown or arguments invalid
+
+ The RESETKEY command has two forms.
+
+ The first form accepts a mailbox name as an argument and generates a
+ new mailbox access key for the given mailbox in the user's mailbox
+ access key table, replacing any previous mailbox access key (and
+ revoking any URLs that were authorized with a URLAUTH using that key)
+ in that table. By default, the mailbox access key is generated for
+ the INTERNAL mechanism; other mechanisms can be specified with the
+ optional mechanism argument.
+
+ The second form, with no arguments, removes all mailbox access keys
+ in the user's mailbox access key table, revoking all URLs currently
+ authorized using URLAUTH by the user.
+
+ Any current IMAP session logged in as the user that has the mailbox
+ selected will receive an untagged OK response with the URLMECH status
+ response code (see section BASE.7.1.URLMECH for more details about
+ the URLMECH status response code).
+
+ Example:
+
+ C: a31 RESETKEY
+ S: a31 OK All keys removed
+ C: a32 RESETKEY INBOX
+ S: a32 OK [URLMECH INTERNAL] mechs
+ C: a33 RESETKEY INBOX XSAMPLE
+ S: a33 OK [URLMECH INTERNAL XSAMPLE=P34OKhO7VEkCbsiYY8rGEg==] done
+
+
+
+
+
+Crispin Standards Track [Page 8]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+BASE.6.3.GENURLAUTH. GENURLAUTH Command
+
+ Argument: one or more URL/mechanism pairs
+
+ Response: untagged response: GENURLAUTH
+
+ Result: OK - GENURLAUTH completed
+ NO - GENURLAUTH error: can't generate a URLAUTH
+ BAD - command unknown or arguments invalid
+
+ The GENURLAUTH command requests that the server generate a URLAUTH-
+ authorized URL for each of the given URLs using the given URL
+ authorization mechanism.
+
+ The server MUST validate each supplied URL as follows:
+
+ (1) The mailbox component of the URL MUST refer to an existing
+ mailbox.
+
+ (2) The server component of the URL MUST contain a valid userid
+ that identifies the owner of the mailbox access key table that
+ will be used to generate the URLAUTH-authorized URL. As a
+ consequence, the iserver rule of [IMAPURL] is modified so that
+ iuserauth is mandatory.
+
+ Note: the server component of the URL is generally the
+ logged in userid and server. If not, then the logged in
+ userid and server MUST have owner-type access to the
+ mailbox access key table owned by the userid and server
+ indicated by the server component of the URL.
+
+ (3) There is a valid access identifier that, in the case of
+ "submit+" and "user+", will contain a valid userid. This
+ userid is not necessarily the same as the owner userid
+ described in (2).
+
+ (4) The server MAY also verify that the iuid and/or isection
+ components (if present) are valid.
+
+ If any of the above checks fail, the server MUST return a tagged BAD
+ response with the following exception. If an invalid userid is
+ supplied as the mailbox access key owner and/or as part of the access
+ identifier, the server MAY issue a tagged OK response with a
+ generated mailbox key that always fails validation when used with a
+ URLFETCH command. This exception prevents an attacker from
+ validating userids.
+
+
+
+
+
+Crispin Standards Track [Page 9]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ If there is currently no mailbox access key for the given mailbox in
+ the owner's mailbox access key table, one is automatically generated.
+ That is, it is not necessary to use RESETKEY prior to first-time use
+ of GENURLAUTH.
+
+ If the command is successful, a GENURLAUTH response code is returned
+ listing the requested URLs as URLAUTH-authorized URLs.
+
+ Examples:
+
+ C: a775 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+ ;section=1.2" INTERNAL
+ S: a775 BAD missing access identifier in supplied URL
+ C: a776 GENURLAUTH "imap://example.com/Shared/;uid=20/
+ ;section=1.2;urlauth=submit+fred" INTERNAL
+ S: a776 BAD missing owner username in supplied URL
+ C: a777 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+ ;section=1.2;urlauth=submit+fred" INTERNAL
+ S: * GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+ ;urlauth=submit+fred:internal:91354a473744909de610943775f92038"
+ S: a777 OK GENURLAUTH completed
+
+BASE.6.3.URLFETCH. URLFETCH Command
+
+ Argument: one or more URLs
+
+ Response: untagged response: URLFETCH
+
+ Result: OK - urlfetch completed
+ NO - urlfetch failed due to server internal error
+ BAD - command unknown or arguments invalid
+
+ The URLFETCH command requests that the server return the text data
+ associated with the specified IMAP URLs, as described in [IMAPURL]
+ and extended by this document. The data is returned for all
+ validated URLs, regardless of whether or not the session would
+ otherwise be able to access the mailbox containing that data via
+ SELECT or EXAMINE.
+
+ Note: This command does not require that the URL refer to the
+ selected mailbox; nor does it require that any mailbox be
+ selected. It also does not in any way interfere with any selected
+ mailbox.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 10]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ The URLFETCH command effectively executes with the access of the
+ userid in the server component of the URL (which is generally the
+ userid that issued the GENURLAUTH). By itself, the URLAUTH does NOT
+ grant access to the data; once validated, it grants whatever access
+ to the data is held by the userid in the server component of the URL.
+ That access may have changed since the GENURLAUTH was done.
+
+ The URLFETCH command MUST return an untagged URLFETCH response and a
+ tagged OK response to any URLFETCH command that is syntactically
+ valid. A NO response indicates a server internal failure that may be
+ resolved on later retry.
+
+ Note: The possibility of a NO response is to accommodate
+ implementations that would otherwise have to issue an untagged BYE
+ with a fatal error due to an inability to respond to a valid
+ request. In an ideal world, a server SHOULD NOT issue a NO
+ response.
+
+ The server MUST return NIL for any IMAP URL that references an entire
+ IMAP server, a list of mailboxes, an entire IMAP mailbox, or IMAP
+ search results.
+
+ Example:
+
+ Note: For clarity, this example uses the LOGIN command, which
+ SHOULD NOT be used over a non-encrypted communication path.
+
+ This example is of a submit server, obtaining a message segment
+ for a message that it has already validated was submitted by
+ "fred".
+
+ S: * OK [CAPABILITY IMAP4REV1 URLAUTH] example.com IMAP server
+ C: a001 LOGIN submitserver secret
+ S: a001 OK submitserver logged in
+ C: a002 URLFETCH "imap://joe@example.com/INBOX/;uid=20/
+ ;section=1.2;urlauth=submit+fred:internal
+ :91354a473744909de610943775f92038"
+ S: * URLFETCH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+ ;urlauth=submit+fred:internal
+ :91354a473744909de610943775f92038" {28}
+ S: Si vis pacem, para bellum.
+ S:
+ S: a002 OK URLFETCH completed
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 11]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+8. Additional Responses
+
+ These responses are extensions to the [IMAP] base protocol.
+
+ The section headings of these responses are intended to correspond
+ with where they would be located in the base protocol document if
+ they were part of that document.
+
+BASE.7.1.URLMECH. URLMECH Status Response Code
+
+ The URLMECH status response code is followed by a list of URL
+ authorization mechanism names. Mechanism names other than INTERNAL
+ may be appended with an "=" and BASE64-encoded form of mechanism-
+ specific data.
+
+ This status response code is returned in an untagged OK response in
+ response to a RESETKEY, SELECT, or EXAMINE command. In the case of
+ the RESETKEY command, this status response code can be sent in the
+ tagged OK response instead of requiring a separate untagged OK
+ response.
+
+ Example:
+
+ C: a33 RESETKEY INBOX XSAMPLE
+ S: a33 OK [URLMECH INTERNAL XSAMPLE=P34OKhO7VEkCbsiYY8rGEg==] done
+
+ In this example, the server supports the INTERNAL mechanism and an
+ experimental mechanism called XSAMPLE, which also holds some
+ mechanism-specific data (the name "XSAMPLE" is for illustrative
+ purposes only).
+
+BASE.7.4.GENURLAUTH. GENURLAUTH Response
+
+ Contents: One or more URLs
+
+ The GENURLAUTH response returns the URLAUTH-authorized URL(s)
+ requested by a GENURLAUTH command.
+
+ Example:
+
+ C: a777 GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/
+ ;section=1.2;urlauth=submit+fred" INTERNAL
+ S: * GENURLAUTH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+ ;urlauth=submit+fred:internal:91354a473744909de610943775f92038"
+ S: a777 OK GENURLAUTH completed
+
+
+
+
+
+
+Crispin Standards Track [Page 12]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+BASE.7.4.URLFETCH. URLFETCH Response
+
+ Contents: One or more URL/nstring pairs
+
+ The URLFETCH response returns the message text data associated with
+ one or more IMAP URLs, as described in [IMAPURL] and extended by this
+ document. This response occurs as the result of a URLFETCH command.
+
+ The returned data string is NIL if the URL is invalid for any reason
+ (including validation failure). If the URL is valid, but the IMAP
+ fetch of the body part returned NIL (this should not happen), the
+ returned data string should be the empty string ("") and not NIL.
+
+ Note: This command does not require that the URL refer to the
+ selected mailbox; nor does it require that any mailbox be
+ selected. It also does not in any way interfere with any selected
+ mailbox.
+
+ Example:
+
+ C: a002 URLFETCH "imap://joe@example.com/INBOX/;uid=20/
+ ;section=1.2;urlauth=submit+fred:internal
+ :91354a473744909de610943775f92038"
+ S: * URLFETCH "imap://joe@example.com/INBOX/;uid=20/;section=1.2
+ ;urlauth=submit+fred:internal
+ :91354a473744909de610943775f92038" {28}
+ S: Si vis pacem, para bellum.
+ S:
+ S: a002 OK URLFETCH completed
+
+9. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ The following modifications are made to the Formal Syntax in [IMAP]:
+
+resetkey = "RESETKEY" [SP mailbox *(SP mechanism)]
+
+capability =/ "URLAUTH"
+
+command-auth =/ resetkey / genurlauth / urlfetch
+
+resp-text-code =/ "URLMECH" SP "INTERNAL" *(SP mechanism ["=" base64])
+
+genurlauth = "GENURLAUTH" 1*(SP url-rump SP mechanism)
+
+genurlauth-data = "*" SP "GENURLAUTH" 1*(SP url-full)
+
+
+
+Crispin Standards Track [Page 13]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+url-full = astring
+ ; contains authimapurlfull as defined below
+
+url-rump = astring
+ ; contains authimapurlrump as defined below
+
+urlfetch = "URLFETCH" 1*(SP url-full)
+
+urlfetch-data = "*" SP "URLFETCH" 1*(SP url-full SP nstring)
+
+ The following extensions are made to the Formal Syntax in [IMAPURL]:
+
+authimapurl = "imap://" enc-user [iauth] "@" hostport "/"
+ imessagepart
+ ; replaces "imapurl" and "iserver" rules for
+ ; URLAUTH authorized URLs
+
+authimapurlfull = authimapurl iurlauth
+
+authimapurlrump = authimapurl iurlauth-rump
+
+enc-urlauth = 32*HEXDIG
+
+enc-user = 1*achar
+ ; same as "enc_user" in RFC 2192
+
+iurlauth = iurlauth-rump ":" mechanism ":" enc-urlauth
+
+iurlauth-rump = [expire] ";URLAUTH=" access
+
+access = ("submit+" enc-user) / ("user+" enc-user) /
+ "authuser" / "anonymous"
+
+expire = ";EXPIRE=" date-time
+ ; date-time defined in [DATETIME]
+
+mechanism = "INTERNAL" / 1*(ALPHA / DIGIT / "-" / ".")
+ ; case-insensitive
+ ; new mechanisms MUST be registered with IANA
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 14]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+10. Security Considerations
+
+ Security considerations are discussed throughout this memo.
+
+ The mailbox access key SHOULD have at least 128 bits of entropy
+ (refer to [RANDOM] for more details) and MUST be unpredictable.
+
+ The server implementation of the INTERNAL mechanism SHOULD consider
+ the possibility of needing to change the token generation algorithm,
+ and SHOULD incorporate some means of identifying the token generation
+ algorithm within the token.
+
+ The URLMECH status response code may expose sensitive data in the
+ mechanism-specific data for mechanisms other than INTERNAL. A server
+ implementation MUST implement a configuration that will not return a
+ URLMECH status response code unless some mechanism is provided that
+ protects the session from snooping, such as a TLS or SASL security
+ layer that provides confidentiality protection.
+
+ The calculation of an authorization token with a "plausible" key if
+ the mailbox can not be identified is necessary to avoid attacks in
+ which the server is probed to see if a particular mailbox exists on
+ the server by measuring the amount of time taken to reject a known
+ bad name versus some other name.
+
+ To protect against a computational denial-of-service attack, a server
+ MAY impose progressively longer delays on multiple URL requests that
+ fail validation.
+
+ The decision to use the "authuser" access identifier should be made
+ with caution. An "authuser" access identifier can be used by any
+ authorized user of the IMAP server; therefore, use of this access
+ identifier should be limited to content that may be disclosed to any
+ authorized user of the IMAP server.
+
+ The decision to use the "anonymous" access identifier should be made
+ with extreme caution. An "anonymous" access identifier can be used
+ by anyone; therefore, use of this access identifier should be limited
+ to content that may be disclosed to anyone. Many IMAP servers do not
+ permit anonymous access; in this case, the "anonymous" access
+ identifier is equivalent to "authuser", but this MUST NOT be relied
+ upon.
+
+ Although this specification does not prohibit the theoretical
+ capability to generate a URL with a server component other than the
+ logged in userid and server, this capability should only be provided
+
+
+
+
+
+Crispin Standards Track [Page 15]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+ when the logged in userid/server has been authorized as equivalent to
+ the server component userid/server, or otherwise has access to that
+ userid/server mailbox access key table.
+
+11. IANA Considerations
+
+ This document constitutes registration of the URLAUTH capability in
+ the imap4-capabilities registry.
+
+ URLAUTH authorization mechanisms are registered by publishing a
+ standards track or IESG-approved experimental RFC. The registry is
+ currently located at:
+
+http://www.iana.org/assignments/urlauth-authorization-mechanism-registry
+
+ This registry is case-insensitive.
+
+ This document constitutes registration of the INTERNAL URLAUTH
+ authorization mechanism.
+
+ IMAP URLAUTH Authorization Mechanism Registry
+
+ Mechanism Name Reference
+ -------------- ---------
+ INTERNAL [RFC4467]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 16]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+12. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [BURL] Newman, C., "Message Submission BURL Extension", RFC 4468,
+ May 2006.
+
+ [DATETIME] Klyne, G. and C. Newman, "Date and Time on the Internet:
+ Timestamps", RFC 3339, July 2002.
+
+ [IMAP] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [IMAPURL] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+13. Informative References
+
+ [HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
+ Hashing for Message Authentication", RFC 2104, February
+ 1997.
+
+ [RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
+ "Randomness Requirements for Security", BCP 106, RFC 4086,
+ June 2005.
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 17]
+
+RFC 4467 IMAP - URLAUTH Extension May 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Crispin Standards Track [Page 18]
+
diff --git a/imap/docs/rfc/rfc4468.txt b/imap/docs/rfc/rfc4468.txt
new file mode 100644
index 00000000..b16dcb4e
--- /dev/null
+++ b/imap/docs/rfc/rfc4468.txt
@@ -0,0 +1,787 @@
+
+
+
+
+
+
+Network Working Group C. Newman
+Request for Comments: 4468 Sun Microsystems
+Updates: 3463 May 2006
+Category: Standards Track
+
+
+ Message Submission BURL Extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ The submission profile of Simple Mail Transfer Protocol (SMTP)
+ provides a standard way for an email client to submit a complete
+ message for delivery. This specification extends the submission
+ profile by adding a new BURL command that can be used to fetch
+ submission data from an Internet Message Access Protocol (IMAP)
+ server. This permits a mail client to inject content from an IMAP
+ server into the SMTP infrastructure without downloading it to the
+ client and uploading it back to the server.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 1]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 2. Conventions Used in This Document ...............................2
+ 3. BURL Submission Extension .......................................3
+ 3.1. SMTP Submission Extension Registration .....................3
+ 3.2. BURL Transaction ...........................................3
+ 3.3. The BURL IMAP Options ......................................4
+ 3.4. Examples ...................................................5
+ 3.5. Formal Syntax ..............................................6
+ 4. 8-Bit and Binary ................................................7
+ 5. Updates to RFC 3463 .............................................7
+ 6. Response Codes ..................................................7
+ 7. IANA Considerations .............................................9
+ 8. Security Considerations .........................................9
+ 9. References .....................................................11
+ 9.1. Normative References ......................................11
+ 9.2. Informative References ....................................12
+ Appendix A. Acknowledgements .....................................13
+
+1. Introduction
+
+ This specification defines an extension to the standard Message
+ Submission [RFC4409] protocol to permit data to be fetched from an
+ IMAP server at message submission time. This MAY be used in
+ conjunction with the CHUNKING [RFC3030] mechanism so that chunks of
+ the message can come from an external IMAP server. This provides the
+ ability to forward an email message without first downloading it to
+ the client.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as defined in "Key words for
+ use in RFCs to Indicate Requirement Levels" [RFC2119].
+
+ The formal syntax uses the Augmented Backus-Naur Form (ABNF)
+ [RFC4234] notation including the core rules defined in Appendix B of
+ RFC 4234.
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 2]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+3. BURL Submission Extension
+
+ This section defines the BURL submission extension.
+
+3.1. SMTP Submission Extension Registration
+
+ 1. The name of this submission extension is "BURL". This extends
+ the Message Submission protocol on port 587 and MUST NOT be
+ advertised by a regular SMTP [RFC2821] server on port 25 that
+ acts as a relay for incoming mail from other SMTP relays.
+
+ 2. The EHLO keyword value associated with the extension is "BURL".
+
+ 3. The BURL EHLO keyword will have zero or more arguments. The only
+ argument defined at this time is the "imap" argument, which MUST
+ be present in order to use IMAP URLs with BURL. Clients MUST
+ ignore other arguments after the BURL EHLO keyword unless they
+ are defined by a subsequent IETF standards track specification.
+ The arguments that appear after the BURL EHLO keyword may change
+ subsequent to the use of SMTP AUTH [RFC2554], so a server that
+ advertises BURL with no arguments prior to authentication
+ indicates that BURL is supported but authentication is required
+ to use it.
+
+ 4. This extension adds the BURL SMTP verb. This verb is used as a
+ replacement for the DATA command and is only permitted during a
+ mail transaction after at least one successful RCPT TO.
+
+3.2. BURL Transaction
+
+ A simple BURL transaction will consist of MAIL FROM, one or more RCPT
+ TO headers, and a BURL command with the "LAST" tag. The BURL command
+ will include an IMAP URL pointing to a fully formed message ready for
+ injection into the SMTP infrastructure. If PIPELINING [RFC2920] is
+ advertised, the client MAY send the entire transaction in one round
+ trip. If no valid RCPT TO address is supplied, the BURL command will
+ simply fail, and no resolution of the BURL URL argument will be
+ performed. If at least one valid RCPT TO address is supplied, then
+ the BURL URL argument will be resolved before the server responds to
+ the command.
+
+ A more sophisticated BURL transaction MAY occur when the server also
+ advertises CHUNKING [RFC3030]. In this case, the BURL and BDAT
+ commands may be interleaved until one of them terminates the
+ transaction with the "LAST" argument. If PIPELINING [RFC2920] is
+ also advertised, then the client may pipeline the entire transaction
+ in one round-trip. However, it MUST wait for the results of the
+ "LAST" BDAT or BURL command prior to initiating a new transaction.
+
+
+
+Newman Standards Track [Page 3]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ The BURL command directs the server to fetch the data object to which
+ the URL refers and include it in the message. If the URL fetch
+ fails, the server will fail the entire transaction.
+
+3.3. The BURL IMAP Options
+
+ When "imap" is present in the space-separated list of arguments
+ following the BURL EHLO keyword, it indicates that the BURL command
+ supports the URLAUTH [RFC4467] extended form of IMAP URLs [RFC2192]
+ and that the submit server is configured with the necessary
+ credentials to resolve "urlauth=submit+" IMAP URLs for the submit
+ server's domain.
+
+ Subsequent to a successful SMTP AUTH command, the submission server
+ MAY indicate a prearranged trust relationship with a specific IMAP
+ server by including a BURL EHLO keyword argument of the form
+ "imap://imap.example.com". In this case, the submission server will
+ permit a regular IMAP URL referring to messages or parts of messages
+ on imap.example.com that the user who authenticated to the submit
+ server can access. Note that this form does not imply that the
+ submit server supports URLAUTH URLs; the submit server must advertise
+ both "imap" and "imap://imap.example.com" to indicate support for
+ both extended and non-extended URL forms.
+
+ When the submit server connects to the IMAP server, it acts as an
+ IMAP client and thus is subject to both the mandatory-to-implement
+ IMAP capabilities in Section 6.1.1 of RFC 3501, and the security
+ considerations in Section 11 of RFC 3501. Specifically, this
+ requires that the submit server implement a configuration that uses
+ STARTTLS followed by SASL PLAIN [SASL-PLAIN] to authenticate to the
+ IMAP server.
+
+ When the submit server resolves a URLAUTH IMAP URL, it uses submit
+ server credentials when authenticating to the IMAP server. The
+ authentication identity and password used for submit credentials MUST
+ be configurable. The string "submit" is suggested as a default value
+ for the authentication identity, with no default for the password.
+ Typically, the authorization identity is empty in this case; thus the
+ IMAP server will derive the authorization identity from the
+ authentication identity. If the IMAP URL uses the "submit+" access
+ identifier prefix, the submit server MUST refuse the BURL command
+ unless the userid in the URL's <access> token matches the submit
+ client's authorization identity.
+
+ When the submit server resolves a regular IMAP URL, it uses the
+ submit client's authorization identity when authenticating to the
+ IMAP server. If both the submit client and the submit server's
+ embedded IMAP client use SASL PLAIN (or the equivalent), the submit
+
+
+
+Newman Standards Track [Page 4]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ server SHOULD forward the client's credentials if and only if the
+ submit server knows that the IMAP server is in the same
+ administrative domain. If the submit server supports SASL mechanisms
+ other than PLAIN, it MUST implement a configuration in which the
+ submit server's embedded IMAP client uses STARTTLS and SASL PLAIN
+ with the submit server's authentication identity and password (for
+ the respective IMAP server) and the submit client's authorization
+ identity.
+
+3.4. Examples
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively. If a single "C:" or "S:" label applies to
+ multiple lines, then the line breaks between those lines are for
+ editorial clarity only and are not part of the actual protocol
+ exchange.
+
+ Two successful submissions (without and with pipelining) follow:
+
+ <SSL/TLS encryption layer negotiated>
+ C: EHLO potter.example.com
+ S: 250-owlry.example.com
+ S: 250-8BITMIME
+ S: 250-BURL imap
+ S: 250-AUTH PLAIN
+ S: 250-DSN
+ S: 250 ENHANCEDSTATUSCODES
+ C: AUTH PLAIN aGFycnkAaGFycnkAYWNjaW8=
+ S: 235 2.7.0 PLAIN authentication successful.
+ C: MAIL FROM:<harry@gryffindor.example.com>
+ S: 250 2.5.0 Address Ok.
+ C: RCPT TO:<ron@gryffindor.example.com>
+ S: 250 2.1.5 ron@gryffindor.example.com OK.
+ C: BURL imap://harry@gryffindor.example.com/outbox
+ ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+ :internal:91354a473744909de610943775f92038 LAST
+ S: 250 2.5.0 Ok.
+
+ <SSL/TLS encryption layer negotiated>
+ C: EHLO potter.example.com
+ S: 250-owlry.example.com
+ S: 250-8BITMIME
+ S: 250-PIPELINING
+ S: 250-BURL imap
+ S: 250-AUTH PLAIN
+ S: 250-DSN
+ S: 250 ENHANCEDSTATUSCODES
+ C: AUTH PLAIN aGFycnkAaGFycnkAYWNjaW8=
+
+
+
+Newman Standards Track [Page 5]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ C: MAIL FROM:<harry@gryffindor.example.com>
+ C: RCPT TO:<ron@gryffindor.example.com>
+ C: BURL imap://harry@gryffindor.example.com/outbox
+ ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+ :internal:91354a473744909de610943775f92038 LAST
+ S: 235 2.7.0 PLAIN authentication successful.
+ S: 250 2.5.0 Address Ok.
+ S: 250 2.1.5 ron@gryffindor.example.com OK.
+ S: 250 2.5.0 Ok.
+
+ Note that PIPELINING of the AUTH command is only permitted if the
+ selected mechanism can be completed in one round trip, a client
+ initial response is provided, and no SASL security layer is
+ negotiated. This is possible for PLAIN and EXTERNAL, but not for
+ most other SASL mechanisms.
+
+ Some examples of failure cases:
+
+ C: MAIL FROM:<harry@gryffindor.example.com>
+ C: RCPT TO:<malfoy@slitherin.example.com>
+ C: BURL imap://harry@gryffindor.example.com/outbox
+ ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+ :internal:91354a473744909de610943775f92038 LAST
+ S: 250 2.5.0 Address Ok.
+ S: 550 5.7.1 Relaying not allowed: malfoy@slitherin.example.com
+ S: 554 5.5.0 No recipients have been specified.
+
+ C: MAIL FROM:<harry@gryffindor.example.com>
+ C: RCPT TO:<ron@gryffindor.example.com>
+ C: BURL imap://harry@gryffindor.example.com/outbox
+ ;uidvalidity=1078863300/;uid=25;urlauth=submit+harry
+ :internal:71354a473744909de610943775f92038 LAST
+ S: 250 2.5.0 Address Ok.
+ S: 250 2.1.5 ron@gryffindor.example.com OK.
+ S: 554 5.7.0 IMAP URL authorization failed
+
+3.5. Formal Syntax
+
+ The following syntax specification inherits ABNF [RFC4234] and
+ Uniform Resource Identifiers [RFC3986].
+
+ burl-param = "imap" / ("imap://" authority)
+ ; parameter to BURL EHLO keyword
+
+ burl-cmd = "BURL" SP absolute-URI [SP end-marker] CRLF
+
+ end-marker = "LAST"
+
+
+
+
+Newman Standards Track [Page 6]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+4. 8-Bit and Binary
+
+ A submit server that advertises BURL MUST also advertise 8BITMIME
+ [RFC1652] and perform the down conversion described in that
+ specification on the resulting complete message if 8-bit data is
+ received with the BURL command and passed to a 7-bit server. If the
+ URL argument to BURL refers to binary data, then the submit server
+ MAY refuse the command or down convert as described in Binary SMTP
+ [RFC3030].
+
+ The Submit server MAY refuse to accept a BURL command or combination
+ of BURL and BDAT commands that result in un-encoded 8-bit data in
+ mail or MIME [RFC2045] headers. Alternatively, the server MAY accept
+ such data and down convert to MIME header encoding [RFC2047].
+
+5. Updates to RFC 3463
+
+ SMTP or Submit servers that advertise ENHANCEDSTATUSCODES [RFC2034]
+ use enhanced status codes defined in RFC 3463 [RFC3463]. The BURL
+ extension introduces new error cases that that RFC did not consider.
+ The following additional enhanced status codes are defined by this
+ specification:
+
+ X.6.6 Message content not available
+
+ The message content could not be fetched from a remote system.
+ This may be useful as a permanent or persistent temporary
+ notification.
+
+ X.7.8 Trust relationship required
+
+ The submission server requires a configured trust relationship
+ with a third-party server in order to access the message content.
+
+6. Response Codes
+
+ This section includes example response codes to the BURL command.
+ Other text may be used with the same response codes. This list is
+ not exhaustive, and BURL clients MUST tolerate any valid SMTP
+ response code. Most of these examples include the appropriate
+ enhanced status code [RFC3463].
+
+ 554 5.5.0 No recipients have been specified
+
+ This response code occurs when BURL is used (for example, with
+ PIPELINING) and all RCPT TOs failed.
+
+
+
+
+
+Newman Standards Track [Page 7]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ 503 5.5.0 Valid RCPT TO required before BURL
+
+ This response code is an alternative to the previous one when BURL
+ is used (for example, with PIPELINING) and all RCPT TOs failed.
+
+ 554 5.6.3 Conversion required but not supported
+
+ This response code occurs when the URL points to binary data and
+ the implementation does not support down conversion to base64.
+ This can also be used if the URL points to message data with 8-bit
+ content in headers and the server does not down convert such
+ content.
+
+ 554 5.3.4 Message too big for system
+
+ The message (subsequent to URL resolution) is larger than the
+ per-message size limit for this server.
+
+ 554 5.7.8 URL resolution requires trust relationship
+
+ The submit server does not have a trust relationship with the IMAP
+ server specified in the URL argument to BURL.
+
+ 552 5.2.2 Mailbox full
+
+ The recipient is local, the submit server supports direct
+ delivery, and the recipient has exceeded his quota and any grace
+ period for delivery attempts.
+
+ 554 5.6.6 IMAP URL resolution failed
+
+ The IMAP URLFETCH command returned an error or no data.
+
+ 250 2.5.0 Waiting for additional BURL or BDAT commands
+
+ A BURL command without the "LAST" modifier was sent. The URL for
+ this BURL command was successfully resolved, but the content will
+ not necessarily be committed to persistent storage until the rest
+ of the message content is collected. For example, a Unix server
+ may have written the content to a queue file buffer, but may not
+ yet have performed an fsync() operation. If the server loses
+ power, the content can still be lost.
+
+ 451 4.4.1 IMAP server unavailable
+
+ The connection to the IMAP server to resolve the URL failed.
+
+
+
+
+
+Newman Standards Track [Page 8]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ 250 2.5.0 Ok.
+
+ The URL was successfully resolved, and the complete message data
+ has been committed to persistent storage.
+
+ 250 2.6.4 MIME header conversion with loss performed
+
+ The URL pointed to message data that included mail or MIME headers
+ with 8-bit data. This data was converted to MIME header encoding
+ [RFC2047], but the submit server may not have correctly guessed
+ the unlabeled character set.
+
+7. IANA Considerations
+
+ The "BURL" SMTP extension as described in Section 3 has been
+ registered. This registration has been marked for use by message
+ submission [RFC4409] only in the registry.
+
+8. Security Considerations
+
+ Modern SMTP submission servers often include content-based security
+ and denial-of-service defense mechanisms such as virus filtering,
+ size limits, server-generated signatures, spam filtering, etc.
+ Implementations of BURL should fetch the URL content prior to
+ application of such content-based mechanisms in order to preserve
+ their function.
+
+ Clients that generate unsolicited bulk email or email with viruses
+ could use this mechanism to compensate for a slow link between the
+ client and submit server. In particular, this mechanism would make
+ it feasible for a programmable cell phone or other device on a slow
+ link to become a significant source of unsolicited bulk email and/or
+ viruses. This makes it more important for submit server vendors
+ implementing BURL to have auditing and/or defenses against such
+ denial-of-service attacks including mandatory authentication, logging
+ that associates unique client identifiers with mail transactions,
+ limits on reuse of the same IMAP URL, rate limits, recipient count
+ limits, and content filters.
+
+ Transfer of the URLAUTH [RFC4467] form of IMAP URLs in the clear can
+ expose the authorization token to network eavesdroppers.
+ Implementations that support such URLs can address this issue by
+ using a strong confidentiality protection mechanism. For example,
+ the SMTP STARTTLS [RFC3207] and the IMAP STARTTLS [RFC3501]
+ extensions, in combination with a configuration setting that requires
+ their use with such IMAP URLs, would address this concern.
+
+
+
+
+
+Newman Standards Track [Page 9]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+ Use of a prearranged trust relationship between a submit server and a
+ specific IMAP server introduces security considerations. A
+ compromise of the submit server should not automatically compromise
+ all accounts on the IMAP server, so trust relationships involving
+ super-user proxy credentials are strongly discouraged. A system that
+ requires the submit server to authenticate to the IMAP server with
+ submit credentials and subsequently requires a URLAUTH URL to fetch
+ any content addresses this concern. A trusted third party model for
+ proxy credentials (such as that provided by Kerberos 5 [RFC4120])
+ would also suffice.
+
+ When a client uses SMTP STARTTLS to send a BURL command that
+ references non-public information, there is a user expectation that
+ the entire message content will be treated confidentially. To
+ address this expectation, the message submission server SHOULD use
+ STARTTLS or a mechanism providing equivalent data confidentiality
+ when fetching the content referenced by that URL.
+
+ A legitimate user of a submit server may try to compromise other
+ accounts on the server by providing an IMAP URLAUTH URL that points
+ to a server under that user's control that is designed to undermine
+ the security of the submit server. For this reason, the IMAP client
+ code that the submit server uses must be robust with respect to
+ arbitrary input sizes (including large IMAP literals) and arbitrary
+ delays from the IMAP server. Requiring a prearranged trust
+ relationship between a submit server and the IMAP server also
+ addresses this concern.
+
+ An authorized user of the submit server could set up a fraudulent
+ IMAP server and pass a URL for that server to the submit server. The
+ submit server might then contact the fraudulent IMAP server to
+ authenticate with submit credentials and fetch content. There are
+ several ways to mitigate this potential attack. A submit server that
+ only uses submit credentials with a fixed set of trusted IMAP servers
+ will not be vulnerable to exposure of those credentials. A submit
+ server can treat the IMAP server as untrusted and include defenses
+ for buffer overflows, denial-of-service slowdowns, and other
+ potential attacks. Finally, because authentication is required to
+ use BURL, it is possible to keep a secure audit trail and use that to
+ detect and punish the offending party.
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 10]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+9. References
+
+9.1. Normative References
+
+ [RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
+ Crocker, "SMTP Service Extension for
+ 8bit-MIMEtransport", RFC 1652, July 1994.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2192] Newman, C., "IMAP URL Scheme", RFC 2192,
+ September 1997.
+
+ [RFC2554] Myers, J., "SMTP Service Extension for Authentication",
+ RFC 2554, March 1999.
+
+ [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
+ April 2001.
+
+ [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP
+ over Transport Layer Security", RFC 3207,
+ February 2002.
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
+ "Uniform Resource Identifier (URI): Generic Syntax",
+ STD 66, RFC 3986, January 2005.
+
+ [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [RFC4409] Gellens, R. and J. Klensin, "Message Submission for
+ Mail", RFC 4409, April 2006.
+
+ [RFC4467] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ URLAUTH Extension", RFC 4467, May 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 11]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+9.2. Informative References
+
+ [RFC2034] Freed, N., "SMTP Service Extension for Returning
+ Enhanced Error Codes", RFC 2034, October 1996.
+
+ [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
+ Mail Extensions (MIME) Part One: Format of Internet
+ Message Bodies", RFC 2045, November 1996.
+
+ [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
+ Extensions) Part Three: Message Header Extensions for
+ Non-ASCII Text", RFC 2047, November 1996.
+
+ [RFC2920] Freed, N., "SMTP Service Extension for Command
+ Pipelining", STD 60, RFC 2920, September 2000.
+
+ [RFC3030] Vaudreuil, G., "SMTP Service Extensions for
+ Transmission of Large and Binary MIME Messages",
+ RFC 3030, December 2000.
+
+ [RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes",
+ RFC 3463, January 2003.
+
+ [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
+ Kerberos Network Authentication Service (V5)", RFC
+ 4120, July 2005.
+
+ [SASL-PLAIN] Zeilenga, K., "The Plain SASL Mechanism", Work in
+ Progress, March 2005.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 12]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+Appendix A. Acknowledgements
+
+ This document is a product of the lemonade WG. Many thanks are due
+ to all the participants of that working group for their input. Mark
+ Crispin was instrumental in the conception of this mechanism. Thanks
+ to Randall Gellens, Alexey Melnikov, Sam Hartman, Ned Freed, Dave
+ Cridland, Peter Coates, and Mark Crispin for review comments on the
+ document. Thanks to the RFC Editor for correcting the author's
+ grammar mistakes. Thanks to Ted Hardie, Randall Gellens, Mark
+ Crispin, Pete Resnick, and Greg Vaudreuil for extremely interesting
+ debates comparing this proposal and alternatives. Thanks to the
+ lemonade WG chairs Eric Burger and Glenn Parsons for concluding the
+ debate at the correct time and making sure this document got
+ completed.
+
+Author's Address
+
+ Chris Newman
+ Sun Microsystems
+ 3401 Centrelake Dr., Suite 410
+ Ontario, CA 91761
+ US
+
+ EMail: chris.newman@sun.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman Standards Track [Page 13]
+
+RFC 4468 Message Submission BURL Extension May 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Newman Standards Track [Page 14]
+
diff --git a/imap/docs/rfc/rfc4469.txt b/imap/docs/rfc/rfc4469.txt
new file mode 100644
index 00000000..da365514
--- /dev/null
+++ b/imap/docs/rfc/rfc4469.txt
@@ -0,0 +1,731 @@
+
+
+
+
+
+
+Network Working Group P. Resnick
+Request for Comments: 4469 QUALCOMM Incorporated
+Updates: 3501, 3502 April 2006
+Category: Standards Track
+
+
+ Internet Message Access Protocol (IMAP) CATENATE Extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ The CATENATE extension to the Internet Message Access Protocol (IMAP)
+ extends the APPEND command to allow clients to create messages on the
+ IMAP server that may contain a combination of new data along with
+ parts of (or entire) messages already on the server. Using this
+ extension, the client can catenate parts of an already existing
+ message onto a new message without having to first download the data
+ and then upload it back to the server.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 1]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+1. Introduction
+
+ The CATENATE extension to the Internet Message Access Protocol (IMAP)
+ [1] allows the client to create a message on the server that can
+ include the text of messages (or parts of messages) that already
+ exist on the server without having to FETCH them and APPEND them back
+ to the server. The CATENATE extension extends the APPEND command so
+ that, instead of a single message literal, the command can take as
+ arguments any combination of message literals (as described in IMAP
+ [1]) and message URLs (as described in the IMAP URL Scheme [2]
+ specification). The server takes all the pieces and catenates them
+ into the output message. The CATENATE extension can also coexist
+ with the MULTIAPPEND extension [3] to APPEND multiple messages in a
+ single command.
+
+ There are some obvious uses for the CATENATE extension. The
+ motivating use case was to provide a way for a resource-constrained
+ client to compose a message for subsequent submission that contains
+ data that already exists in that client's IMAP store. Because the
+ client does not have to download and re-upload potentially large
+ message parts, bandwidth and processing limitations do not have as
+ much impact. In addition, since the client can create a message in
+ its own IMAP store, the command also addresses the desire of the
+ client to archive a copy of a sent message without having to upload
+ the message twice. (Mechanisms for sending the message are outside
+ the scope of this document.)
+
+ The extended APPEND command can also be used to copy parts of a
+ message to another mailbox for archival purposes while getting rid of
+ undesired parts. In environments where server storage is limited, a
+ client could get rid of large message parts by copying over only the
+ necessary parts and then deleting the original message. The
+ mechanism could also be used to add data to a message (such as
+ prepending message header fields) or to include other data by making
+ a copy of the original and catenating the new data.
+
+2. The CATENATE Capability
+
+ A server that supports this extension returns "CATENATE" as one of
+ the responses to the CAPABILITY command.
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 2]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+3. The APPEND Command
+
+ Arguments: mailbox name
+ (The following can be repeated in the presence of the
+ MULTIAPPEND extension [3])
+ OPTIONAL flag parenthesized list
+ OPTIONAL date/time string
+ a single message literal or one or more message parts to
+ catenate, specified as:
+ message literal
+ or
+ message (or message part) URL
+
+ Responses: OPTIONAL NO responses: BADURL, TOOBIG
+
+ Result: OK - append completed
+ NO - append error: can't append to that mailbox, error
+ in flags or date/time or message text, or can't
+ fetch that data
+ BAD - command unknown or arguments invalid
+
+ The APPEND command concatenates all the message parts and appends
+ them as a new message to the end of the specified mailbox. The
+ parenthesized flag list and date/time string set the flags and the
+ internal date, respectively, as described in IMAP [1]. The
+ subsequent command parameters specify the message parts that are
+ appended sequentially to the output message.
+
+ If the original form of APPEND is used, a message literal follows the
+ optional flag list and date/time string, which is appended as
+ described in IMAP [1]. If the extended form is used, "CATENATE" and
+ a parenthesized list of message literals and message URLs follows,
+ each of which is appended to the new message. If a message literal
+ is specified (indicated by "TEXT"), the octets following the count
+ are appended. If a message URL is specified (indicated by "URL"),
+ the octets of the body part pointed to by that URL are appended, as
+ if the literal returned in a FETCH BODY response were put in place of
+ the message part specifier. The APPEND command does not cause the
+ \Seen flag to be set for any catenated body part. The APPEND command
+ does not change the selected mailbox.
+
+ In the extended APPEND command, the string following "URL" is an IMAP
+ URL [2] and is interpreted according to the rules of [2]. The
+ present document only describes the behavior of the command using
+ IMAP URLs that refer to specific messages or message parts on the
+ current IMAP server from the current authenticated IMAP session.
+ Because of that, only relative IMAP message or message part URLs
+ (i.e., those having no scheme or <iserver>) are used. The base URL
+
+
+
+Resnick Standards Track [Page 3]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+ for evaluating the relative URL is considered "imap://user@server/",
+ where "user" is the user name of the currently authenticated user and
+ "server" is the domain name of the current server. When in the
+ selected state, the base URL is considered
+ "imap://user@server/mailbox", where "mailbox" is the encoded name of
+ the currently selected mailbox. Additionally, since the APPEND
+ command is valid in the authenticated state of an IMAP session, no
+ further LOGIN or AUTHENTICATE command is performed for URLs specified
+ in the extended APPEND command.
+
+ Note: Use of an absolute IMAP URL or any URL that refers to
+ anything other than a message or message part from the current
+ authenticated IMAP session is outside the scope of this document
+ and would require an extension to this specification, and a server
+ implementing only this specification would return NO to such a
+ request.
+
+ The client is responsible for making sure that the catenated message
+ is in the format of an Internet Message Format (RFC 2822) [4] or
+ Multipurpose Internet Mail Extension (MIME) [5] message. In
+ particular, when a URL is catenated, the server copies octets,
+ unchanged, from the indicated message or message part to the
+ catenated message. It does no data conversion (e.g., MIME transfer
+ encodings) nor any verification that the data is appropriate for the
+ MIME part of the message into which it is inserted. The client is
+ also responsible for inserting appropriate MIME boundaries between
+ body parts, and writing MIME Content-Type and Content-Transfer-
+ Encoding lines as needed in the appropriate places.
+
+ Responses behave just as the original APPEND command described in
+ IMAP [1]. If the server implements the IMAP UIDPLUS extension [6],
+ it will also return an APPENDUID response code in the tagged OK
+ response. Two response codes are provided in Section 4 that can be
+ used in the tagged NO response if the APPEND command fails.
+
+4. Response Codes
+
+ When a APPEND command fails, it may return a response code that
+ describes a reason for the failure.
+
+4.1. BADURL Response
+
+ The BADURL response code is returned if the APPEND fails to process
+ one of the specified URLs. Possible reasons for this are bad URL
+ syntax, unrecognized URL schema, invalid message UID, or invalid body
+ part. The BADURL response code contains the first URL specified as a
+ parameter to the APPEND command that has caused the operation to
+ fail.
+
+
+
+Resnick Standards Track [Page 4]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+4.2. TOOBIG Response
+
+ The TOOBIG response code is returned if the resulting message will
+ exceed the 4-GB IMAP message limit. This might happen, for example,
+ if the client specifies 3 URLs for 2-GB messages. Note that even if
+ the server doesn't return TOOBIG, it still has to be defensive
+ against misbehaving or malicious clients that try to construct a
+ message over the 4-GB limit. The server may also wish to return the
+ TOOBIG response code if the resulting message exceeds a server-
+ specific message size limit.
+
+5. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) [7] notation. Elements not defined here can be found in
+ the formal syntax of the ABNF [7], IMAP [1], and IMAP ABNF extensions
+ [8] specifications. Note that capability and resp-text-code are
+ extended from the IMAP [1] specification and append-data is extended
+ from the IMAP ABNF extensions [8] specification.
+
+ append-data =/ "CATENATE" SP "(" cat-part *(SP cat-part) ")"
+
+ cat-part = text-literal / url
+
+ text-literal = "TEXT" SP literal
+
+ url = "URL" SP astring
+
+ resp-text-code =/ toobig-response-code / badurl-response-code
+
+ toobig-response-code = "TOOBIG"
+
+ badurl-response-code = "BADURL" SP url-resp-text
+
+ url-resp-text = 1*(%x01-09 /
+ %x0B-0C /
+ %x0E-5B /
+ %x5D-FE) ; Any TEXT-CHAR except "]"
+
+ capability =/ "CATENATE"
+
+ The astring in the definition of url and the url-resp-text in the
+ definition of badurl-response-code each contain an imapurl as defined
+ by [2].
+
+
+
+
+
+
+
+Resnick Standards Track [Page 5]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+6. Acknowledgements
+
+ Thanks to the members of the LEMONADE working group for their input.
+ Special thanks to Alexey Melnikov for the examples.
+
+7. Security Considerations
+
+ The CATENATE extension does not raise any security considerations
+ that are not present for the base protocol or in the use of IMAP
+ URLs, and these issues are discussed in the IMAP [1] and IMAP URL [2]
+ documents.
+
+8. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located at
+ <http://www.iana.org/assignments/imap4-capabilities>. This document
+ defines the CATENATE IMAP capability. The IANA has added this
+ capability to the registry.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
+Resnick Standards Track [Page 6]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+Appendix A. Examples
+
+ Lines not starting with "C: " or "S: " are continuations of the
+ previous lines.
+
+ The original message in examples 1 and 2 below (UID = 20) has the
+ following structure:
+
+
+ multipart/mixed MIME message with two body parts:
+
+ 1. text/plain
+
+ 2. application/x-zip-compressed
+
+ Example 1: The following example demonstrates how a CATENATE client
+ can replace an attachment in a draft message, without the need to
+ download it to the client and upload it back.
+
+ C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE
+ (URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=HEADER"
+ TEXT {42}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050907
+ C: URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=1.MIME"
+ URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;section=1" TEXT {42}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050907
+ C: URL "/Drafts;UIDVALIDITY=385759045/;UID=30" TEXT {44}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050907--
+ C: )
+ S: A003 OK catenate append completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 7]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+ Example 2: The following example demonstrates how the CATENATE
+ extension can be used to replace edited text in a draft message, as
+ well as header fields for the top level message part (e.g., Subject
+ has changed). The previous version of the draft is marked as
+ \Deleted. Note that the server also supports the UIDPLUS extension,
+ so the APPENDUID response code is returned in the successful OK
+ response to the APPEND command.
+
+ C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE (TEXT {738}
+ S: + Ready for literal data
+ C: Return-Path: <bar@example.org>
+ C: Received: from [127.0.0.2]
+ C: by rufus.example.org via TCP (internal) with ESMTPA;
+ C: Thu, 11 Nov 2004 16:57:07 +0000
+ C: Message-ID: <419399E1.6000505@example.org>
+ C: Date: Thu, 12 Nov 2004 16:57:05 +0000
+ C: From: Bob Ar <bar@example.org>
+ C: X-Accept-Language: en-us, en
+ C: MIME-Version: 1.0
+ C: To: foo@example.net
+ C: Subject: About our holiday trip
+ C: Content-Type: multipart/mixed;
+ C: boundary="------------030308070208000400050907"
+ C:
+ C: --------------030308070208000400050907
+ C: Content-Type: text/plain; charset=us-ascii; format=flowed
+ C: Content-Transfer-Encoding: 7bit
+ C:
+ C: Our travel agent has sent the updated schedule.
+ C:
+ C: Cheers,
+ C: Bob
+ C: --------------030308070208000400050907
+ C: URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;Section=2.MIME"
+ URL "/Drafts;UIDVALIDITY=385759045/;UID=20/;Section=2" TEXT {44}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050907--
+ C: )
+ S: A003 OK [APPENDUID 385759045 45] append Completed
+ C: A004 UID STORE 20 +FLAGS.SILENT (\Deleted)
+ S: A004 OK STORE completed
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 8]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+ Example 3: The following example demonstrates how the CATENATE
+ extension can be used to strip attachments. Below, a PowerPoint
+ attachment was replaced by a small text part explaining that the
+ attachment was stripped.
+
+ C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE
+ (URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=HEADER"
+ TEXT {42}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050903
+ C: URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=1.MIME"
+ URL "/Drafts;UIDVALIDITY=385759045/;UID=21/;section=1" TEXT {255}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050903
+ C: Content-type: text/plain; charset="us-ascii"
+ C: Content-transfer-encoding: 7bit
+ C:
+ C: This body part contained a Power Point presentation that was
+ C: deleted upon your request.
+ C: --------------030308070208000400050903--
+ C: )
+ S: A003 OK append Completed
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Resnick Standards Track [Page 9]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+ Example 4: The following example demonstrates a failed APPEND
+ command. The server returns the BADURL response code to indicate
+ that one of the provided URLs is invalid. This example also
+ demonstrates how the CATENATE extension can be used to construct a
+ digest of several messages.
+
+ C: A003 APPEND Sent (\Seen $MDNSent) CATENATE (TEXT {541}
+ S: + Ready for literal data
+ C: Return-Path: <foo@example.org>
+ C: Received: from [127.0.0.2]
+ C: by rufus.example.org via TCP (internal) with ESMTPA;
+ C: Thu, 11 Nov 2004 16:57:07 +0000
+ C: Message-ID: <419399E1.6000505@example.org>
+ C: Date: Thu, 21 Nov 2004 16:57:05 +0000
+ C: From: Farren Oo <foo@example.org>
+ C: X-Accept-Language: en-us, en
+ C: MIME-Version: 1.0
+ C: To: bar@example.org
+ C: Subject: Digest of the mailing list for today
+ C: Content-Type: multipart/digest;
+ C: boundary="------------030308070208000400050904"
+ C:
+ C: --------------030308070208000400050904
+ C: URL "/INBOX;UIDVALIDITY=785799047/;UID=11467" TEXT {42}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050904
+ C: URL "/INBOX;UIDVALIDITY=785799047/;UID=113330/;section=1.5.9"
+ TEXT {42}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050904
+ C: URL "/INBOX;UIDVALIDITY=785799047/;UID=11916" TEXT {44}
+ S: + Ready for literal data
+ C:
+ C: --------------030308070208000400050904--
+ C: )
+ S: A003 NO [BADURL "/INBOX;UIDVALIDITY=785799047/;UID=113330;
+ section=1.5.9"] CATENATE append has failed, one message expunged
+
+ Note that the server could have validated the URLs as they were
+ received and therefore could have returned the tagged NO response
+ with BADURL response-code in place of any continuation request after
+ the URL was received.
+
+
+
+
+
+
+
+Resnick Standards Track [Page 10]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+9. Normative References
+
+ [1] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1",
+ RFC 3501, March 2003.
+
+ [2] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
+
+ [3] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ MULTIAPPEND Extension", RFC 3502, March 2003.
+
+ [4] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
+
+ [5] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message Bodies",
+ RFC 2045, November 1996.
+
+ [6] Crispin, M., "Internet Message Access Protocol (IMAP) - UIDPLUS
+ extension", RFC 4315, December 2005.
+
+ [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [8] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 ABNF",
+ RFC 4466, April 2006.
+
+
+
+
+
+
+
+
+
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+Resnick Standards Track [Page 11]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+Author's Address
+
+ Peter W. Resnick
+ QUALCOMM Incorporated
+ 5775 Morehouse Drive
+ San Diego, CA 92121-1714
+ US
+
+ Phone: +1 858 651 4478
+ EMail: presnick@qualcomm.com
+ URI: http://www.qualcomm.com/~presnick/
+
+
+
+
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+Resnick Standards Track [Page 12]
+
+RFC 4469 IMAP CATENATE Extension April 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Resnick Standards Track [Page 13]
+
diff --git a/imap/docs/rfc/rfc4505.txt b/imap/docs/rfc/rfc4505.txt
new file mode 100644
index 00000000..6b8a4a11
--- /dev/null
+++ b/imap/docs/rfc/rfc4505.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group K. Zeilenga, Ed.
+Request for Comments: 4505 OpenLDAP Foundation
+Obsoletes: 2245 June 2006
+Category: Standards Track
+
+
+ Anonymous Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ On the Internet, it is common practice to permit anonymous access to
+ various services. Traditionally, this has been done with a plain-
+ text password mechanism using "anonymous" as the user name and using
+ optional trace information, such as an email address, as the
+ password. As plain-text login commands are not permitted in new IETF
+ protocols, a new way to provide anonymous login is needed within the
+ context of the Simple Authentication and Security Layer (SASL)
+ framework.
+
+1. Introduction
+
+ This document defines an anonymous mechanism for the Simple
+ Authentication and Security Layer ([SASL]) framework. The name
+ associated with this mechanism is "ANONYMOUS".
+
+ Unlike many other SASL mechanisms, whose purpose is to authenticate
+ and identify the user to a server, the purpose of this SASL mechanism
+ is to allow the user to gain access to services or resources without
+ requiring the user to establish or otherwise disclose their identity
+ to the server. That is, this mechanism provides an anonymous login
+ method.
+
+ This mechanism does not provide a security layer.
+
+ This document replaces RFC 2245. Changes since RFC 2245 are detailed
+ in Appendix A.
+
+
+
+Zeilenga Standards Track [Page 1]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+2. The Anonymous Mechanism
+
+ The mechanism consists of a single message from the client to the
+ server. The client may include in this message trace information in
+ the form of a string of [UTF-8]-encoded [Unicode] characters prepared
+ in accordance with [StringPrep] and the "trace" stringprep profile
+ defined in Section 3 of this document. The trace information, which
+ has no semantical value, should take one of two forms: an Internet
+ email address, or an opaque string that does not contain the '@'
+ (U+0040) character and that can be interpreted by the system
+ administrator of the client's domain. For privacy reasons, an
+ Internet email address or other information identifying the user
+ should only be used with permission from the user.
+
+ A server that permits anonymous access will announce support for the
+ ANONYMOUS mechanism and allow anyone to log in using that mechanism,
+ usually with restricted access.
+
+ A formal grammar for the client message using Augmented BNF [ABNF] is
+ provided below as a tool for understanding this technical
+ specification.
+
+ message = [ email / token ]
+ ;; to be prepared in accordance with Section 3
+
+ UTF1 = %x00-3F / %x41-7F ;; less '@' (U+0040)
+ UTF2 = %xC2-DF UTF0
+ UTF3 = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
+ %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
+ UTF4 = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
+ %xF4 %x80-8F 2(UTF0)
+ UTF0 = %x80-BF
+
+ TCHAR = UTF1 / UTF2 / UTF3 / UTF4
+ ;; any UTF-8 encoded Unicode character
+ ;; except '@' (U+0040)
+
+ email = addr-spec
+ ;; as defined in [IMAIL]
+
+ token = 1*255TCHAR
+
+ Note to implementors:
+ The <token> production is restricted to 255 UTF-8-encoded Unicode
+ characters. As the encoding of a characters uses a sequence of 1
+ to 4 octets, a token may be as long as 1020 octets.
+
+
+
+
+
+Zeilenga Standards Track [Page 2]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+3. The "trace" Profile of "Stringprep"
+
+ This section defines the "trace" profile of [StringPrep]. This
+ profile is designed for use with the SASL ANONYMOUS Mechanism.
+ Specifically, the client is to prepare the <message> production in
+ accordance with this profile.
+
+ The character repertoire of this profile is Unicode 3.2 [Unicode].
+
+ No mapping is required by this profile.
+
+ No Unicode normalization is required by this profile.
+
+ The list of unassigned code points for this profile is that provided
+ in Appendix A of [StringPrep]. Unassigned code points are not
+ prohibited.
+
+ Characters from the following tables of [StringPrep] are prohibited:
+
+ - C.2.1 (ASCII control characters)
+ - C.2.2 (Non-ASCII control characters)
+ - C.3 (Private use characters)
+ - C.4 (Non-character code points)
+ - C.5 (Surrogate codes)
+ - C.6 (Inappropriate for plain text)
+ - C.8 (Change display properties are deprecated)
+ - C.9 (Tagging characters)
+
+ No additional characters are prohibited.
+
+ This profile requires bidirectional character checking per Section 6
+ of [StringPrep].
+
+4. Example
+
+ Here is a sample ANONYMOUS login between an IMAP client and server.
+ In this example, "C:" and "S:" indicate lines sent by the client and
+ server, respectively. If such lines are wrapped without a new "C:"
+ or "S:" label, then the wrapping is for editorial clarity and is not
+ part of the command.
+
+ Note that this example uses the IMAP profile [IMAP4] of SASL. The
+ base64 encoding of challenges and responses as well as the "+ "
+ preceding the responses are part of the IMAP4 profile, not part of
+ SASL itself. Additionally, protocols with SASL profiles permitting
+ an initial client response will be able to avoid the extra round trip
+ below (the server response with an empty "+ ").
+
+
+
+
+Zeilenga Standards Track [Page 3]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+ In this example, the trace information is "sirhc".
+
+ S: * OK IMAP4 server ready
+ C: A001 CAPABILITY
+ S: * CAPABILITY IMAP4 IMAP4rev1 AUTH=DIGEST-MD5 AUTH=ANONYMOUS
+ S: A001 OK done
+ C: A002 AUTHENTICATE ANONYMOUS
+ S: +
+ C: c2lyaGM=
+ S: A003 OK Welcome, trace information has been logged.
+
+5. Security Considerations
+
+ The ANONYMOUS mechanism grants access to services and/or resources by
+ anyone. For this reason, it should be disabled by default so that
+ the administrator can make an explicit decision to enable it.
+
+ If the anonymous user has any write privileges, a denial-of-service
+ attack is possible by filling up all available space. This can be
+ prevented by disabling all write access by anonymous users.
+
+ If anonymous users have read and write access to the same area, the
+ server can be used as a communication mechanism to exchange
+ information anonymously. Servers that accept anonymous submissions
+ should implement the common "drop box" model, which forbids anonymous
+ read access to the area where anonymous submissions are accepted.
+
+ If the anonymous user can run many expensive operations (e.g., an
+ IMAP SEARCH BODY command), this could enable a denial-of-service
+ attack. Servers are encouraged to reduce the priority of anonymous
+ users or limit their resource usage.
+
+ While servers may impose a limit on the number of anonymous users,
+ note that such limits enable denial-of-service attacks and should be
+ used with caution.
+
+ The trace information is not authenticated, so it can be falsified.
+ This can be used as an attempt to get someone else in trouble for
+ access to questionable information. Administrators investigating
+ abuse need to realize that this trace information may be falsified.
+
+ A client that uses the user's correct email address as trace
+ information without explicit permission may violate that user's
+ privacy. Anyone who accesses an anonymous archive on a sensitive
+ subject (e.g., sexual abuse) likely has strong privacy needs.
+ Clients should not send the email address without the explicit
+ permission of the user and should offer the option of supplying no
+ trace information, thus only exposing the source IP address and time.
+
+
+
+Zeilenga Standards Track [Page 4]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+ Anonymous proxy servers could enhance this privacy but would have to
+ consider the resulting potential denial-of-service attacks.
+
+ Anonymous connections are susceptible to man-in-the-middle attacks
+ that view or alter the data transferred. Clients and servers are
+ encouraged to support external data security services.
+
+ Protocols that fail to require an explicit anonymous login are more
+ susceptible to break-ins given certain common implementation
+ techniques. Specifically, Unix servers that offer user login may
+ initially start up as root and switch to the appropriate user id
+ after an explicit login command. Normally, such servers refuse all
+ data access commands prior to explicit login and may enter a
+ restricted security environment (e.g., the Unix chroot(2) function)
+ for anonymous users. If anonymous access is not explicitly
+ requested, the entire data access machinery is exposed to external
+ security attacks without the chance for explicit protective measures.
+ Protocols that offer restricted data access should not allow
+ anonymous data access without an explicit login step.
+
+ General [SASL] security considerations apply to this mechanism.
+
+ [StringPrep] security considerations and [Unicode] security
+ considerations discussed in [StringPrep] apply to this mechanism.
+ [UTF-8] security considerations also apply.
+
+6. IANA Considerations
+
+ The SASL Mechanism registry [IANA-SASL] entry for the ANONYMOUS
+ mechanism has been updated by the IANA to reflect that this document
+ now provides its technical specification.
+
+ To: iana@iana.org
+ Subject: Updated Registration of SASL mechanism ANONYMOUS
+
+ SASL mechanism name: ANONYMOUS
+ Security considerations: See RFC 4505.
+ Published specification (optional, recommended): RFC 4505
+ Person & email address to contact for further information:
+ Kurt Zeilenga <Kurt@OpenLDAP.org>
+ Chris Newman <Chris.Newman@sun.com>
+ Intended usage: COMMON
+ Author/Change controller: IESG <iesg@ietf.org>
+ Note: Updates existing entry for ANONYMOUS
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 5]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+ The [StringPrep] profile "trace", first defined in this RFC, has been
+ registered:
+
+ To: iana@iana.org
+ Subject: Initial Registration of Stringprep "trace" profile
+
+ Stringprep profile: trace
+ Published specification: RFC 4505
+ Person & email address to contact for further information:
+ Kurt Zeilenga <kurt@openldap.org>
+
+7. Acknowledgement
+
+ This document is a revision of RFC 2245 by Chris Newman. Portions of
+ the grammar defined in Section 1 were borrowed from RFC 3629 by
+ Francois Yergeau.
+
+ This document is a product of the IETF SASL WG.
+
+8. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [IMAIL] Resnick, P., "Internet Message Format", RFC 2822, April
+ 2001.
+
+ [SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
+ Authentication and Security Layer (SASL)", RFC 4422,
+ June 2006.
+
+ [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ('stringprep')", RFC 3454,
+ December 2002.
+
+ [Unicode] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0" is defined by "The Unicode Standard, Version 3.0"
+ (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5),
+ as amended by the "Unicode Standard Annex #27: Unicode
+ 3.1" (http://www.unicode.org/reports/tr27/) and by the
+ "Unicode Standard Annex #28: Unicode 3.2"
+ (http://www.unicode.org/reports/tr28/).
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 3629 (also STD 63), November 2003.
+
+
+
+
+
+
+Zeilenga Standards Track [Page 6]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+9. Informative References
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [IANA-SASL] IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
+ MECHANISMS", <http://www.iana.org/assignments/sasl-
+ mechanisms>.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 7]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+Appendix A. Changes since RFC 2245
+
+ This appendix is non-normative.
+
+ RFC 2245 allows the client to include optional trace information in
+ the form of a human readable string. RFC 2245 restricted this string
+ to US-ASCII. As the Internet is international, this document uses a
+ string restricted to UTF-8 encoded Unicode characters. A
+ "stringprep" profile is defined to precisely define which Unicode
+ characters are allowed in this string. While the string remains
+ restricted to 255 characters, the encoded length of each character
+ may now range from 1 to 4 octets.
+
+ Additionally, a number of editorial changes were made.
+
+Editor's Address
+
+ Kurt D. Zeilenga
+ OpenLDAP Foundation
+
+ EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 8]
+
+RFC 4505 Anonymous SASL Mechanism June 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 9]
+
diff --git a/imap/docs/rfc/rfc4549.txt b/imap/docs/rfc/rfc4549.txt
new file mode 100644
index 00000000..8430ee10
--- /dev/null
+++ b/imap/docs/rfc/rfc4549.txt
@@ -0,0 +1,1963 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov, Ed.
+Request for Comments: 4549 Isode Ltd.
+Category: Informational June 2006
+
+
+ Synchronization Operations for Disconnected IMAP4 Clients
+
+Status of This Memo
+
+ This memo provides information for the Internet community. It does
+ not specify an Internet standard of any kind. Distribution of this
+ memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ This document attempts to address some of the issues involved in
+ building a disconnected IMAP4 client. In particular, it deals with
+ the issues of what might be called the "driver" portion of the
+ synchronization tool: the portion of the code responsible for issuing
+ the correct set of IMAP4 commands to synchronize the disconnected
+ client in the way that is most likely to make the human who uses the
+ disconnected client happy.
+
+ This note describes different strategies that can be used by
+ disconnected clients and shows how to use IMAP protocol in order to
+ minimize the time of the synchronization process.
+
+ This note also lists IMAP extensions that a server should implement
+ in order to provide better synchronization facilities to disconnected
+ clients.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Informational [Page 1]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+Table of Contents
+
+ 1. Introduction ....................................................3
+ 1.1. Conventions Used in This Document ..........................3
+ 2. Design Principles ...............................................3
+ 3. Overall Picture of Synchronization ..............................4
+ 4. Mailbox Synchronization Steps and Strategies ....................7
+ 4.1. Checking UID Validity ......................................7
+ 4.2. Synchronizing Local Changes with the Server ................8
+ 4.2.1. Uploading Messages to the Mailbox ...................8
+ 4.2.2. Optimizing "move" and "copy" Operations .............9
+ 4.2.3. Replaying Local Flag Changes .......................14
+ 4.2.4. Processing Mailbox Compression (EXPUNGE) Requests ..15
+ 4.2.5. Closing a Mailbox ..................................17
+ 4.3. Details of "Normal" Synchronization of a Single Mailbox ...18
+ 4.3.1. Discovering New Messages and Changes to Old
+ Messages ...........................................18
+ 4.3.2. Searching for "Interesting" Messages. ..............20
+ 4.3.3. Populating Cache with "Interesting" Messages. ......21
+ 4.3.4. User-Initiated Synchronization .....................22
+ 4.4. Special Case: Descriptor-Only Synchronization .............22
+ 4.5. Special Case: Fast New-Only Synchronization ...............23
+ 4.6. Special Case: Blind FETCH .................................23
+ 5. Implementation Considerations ..................................24
+ 5.1. Error Recovery during Playback ............................26
+ 5.2. Quality of Implementation Issues ..........................28
+ 5.3. Optimizations .............................................28
+ 6. IMAP Extensions That May Help ..................................30
+ 6.1. CONDSTORE Extension .......................................30
+ 7. Security Considerations ........................................33
+ 8. References .....................................................33
+ 8.1. Normative References ......................................33
+ 8.2. Informative References ....................................34
+ 9. Acknowledgements ...............................................34
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Informational [Page 2]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+1. Introduction
+
+ Several recommendations presented in this document are generally
+ applicable to all types of IMAP clients. However, this document
+ tries to concentrate on disconnected mail clients [IMAP-MODEL]. It
+ also suggests some IMAP extensions* that should be implemented by
+ IMAP servers in order to make the life of disconnected clients
+ easier. In particular, the [UIDPLUS] extension was specifically
+ designed to streamline certain disconnected operations, like
+ expunging, uploading, and copying messages (see Sections 4.2.1,
+ 4.2.2.1, and 4.2.4).
+
+ Readers of this document are also strongly advised to read RFC 2683
+ [RFC2683].
+
+ * Note that the functionality provided by the base IMAP protocol
+ [IMAP4] is sufficient to perform basic synchronization.
+
+1.1. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively. Long lines in examples are broken for
+ editorial clarity.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+ Let's call an IMAP command idempotent if the result of executing the
+ command twice sequentially is the same as the result of executing the
+ command just once.
+
+2. Design Principles
+
+ All mailbox state or content information stored on the disconnected
+ client should be viewed strictly as a cache of the state of the
+ server. The "master" state remains on the server, just as it would
+ with an interactive IMAP4 client. The one exception to this rule is
+ that information about the state of the disconnected client's cache
+ (the state includes flag changes while offline and during scheduled
+ message uploads) remains on the disconnected client: that is, the
+ IMAP4 server is not responsible for remembering the state of the
+ disconnected IMAP4 client.
+
+ We assume that a disconnected client is a client that, for whatever
+ reason, wants to minimize the length of time that it is "on the
+ phone" to the IMAP4 server. Often this will be because the client is
+ using a dialup connection, possibly with very low bandwidth, but
+
+
+
+Melnikov Informational [Page 3]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ sometimes it might just be that the human is in a hurry to catch an
+ airplane, or some other event beyond our control. Whatever the
+ reason, we assume that we must make efficient use of the network
+ connection, both in the usual sense (not generating spurious traffic)
+ and in the sense that we would prefer not to have the connection
+ sitting idle while the client and/or the server is performing
+ strictly local computation or I/O. Another, perhaps simpler way of
+ stating this is that we assume that network connections are
+ "expensive".
+
+ Practical experience with disconnected mail systems has shown that
+ there is no single synchronization strategy that is appropriate for
+ all cases. Different humans have different preferences, and the same
+ human's preference will vary depending both on external circumstance
+ (how much of a hurry the human is in today) and on the value that the
+ human places on the messages being transferred. The point here is
+ that there is no way that the synchronization program can guess
+ exactly what the human wants to do, so the human will have to provide
+ some guidance.
+
+ Taken together, the preceding two principles lead to the conclusion
+ that the synchronization program must make its decisions based on
+ some kind of guidance provided by the human, by selecting the
+ appropriate options in the user interface or through some sort of
+ configuration file. Almost certainly, it should not pause for I/O
+ with the human in the middle of the synchronization process. The
+ human will almost certainly have several different configurations for
+ the synchronization program, for different circumstances.
+
+ Since a disconnected client has no way of knowing what changes might
+ have occurred to the mailbox while it was disconnected, message
+ numbers are not useful to a disconnected client. All disconnected
+ client operations should be performed using UIDs, so that the client
+ can be sure that it and the server are talking about the same
+ messages during the synchronization process.
+
+3. Overall Picture of Synchronization
+
+ The basic strategy for synchronization is outlined below. Note that
+ the real strategy may vary from one application to another or may
+ depend on a synchronization mode.
+
+ a) Process any "actions" that were pending on the client that were
+ not associated with any mailbox. (In particular sending messages
+ composed offline with SMTP. This is not part of IMAP
+ synchronization, but it is mentioned here for completeness.)
+
+
+
+
+
+Melnikov Informational [Page 4]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ b) Fetch the current list of "interesting" mailboxes. (The
+ disconnected client should allow the user to skip this step
+ completely.)
+
+ c) "Client-to-server synchronization": for each IMAP "action" that
+ was pending on the client, do the following:
+
+ 1) If the action implies opening a new mailbox (any operation that
+ operates on messages), open the mailbox. Check its UID
+ validity value (see Section 4.1 for more details) returned in
+ the UIDVALIDITY response code. If the UIDVALIDITY value
+ returned by the server differs, the client MUST empty the local
+ cache of the mailbox and remove any pending "actions" that
+ refer to UIDs in that mailbox (and consider them failed). Note
+ that this doesn't affect actions performed on client-generated
+ fake UIDs (see Section 5).
+
+ 2) Perform the action. If the action is to delete a mailbox
+ (DELETE), make sure that the mailbox is closed first (see also
+ Section 3.4.12 of [RFC2683]).
+
+ d) "Server-to-client synchronization": for each mailbox that requires
+ synchronization, do the following:
+
+ 1) Check the mailbox UIDVALIDITY (see Section 4.1 for more
+ details) with SELECT/EXAMINE/STATUS.
+
+ If UIDVALIDITY value returned by the server differs, the client
+ MUST
+
+ * empty the local cache of that mailbox;
+ * remove any pending "actions" that refer to UIDs in that
+ mailbox and consider them failed; and
+ * skip step 2-II.
+
+ 2) Fetch the current "descriptors";
+
+ I) Discover new messages.
+
+ II) Discover changes to old messages.
+
+ 3) Fetch the bodies of any "interesting" messages that the client
+ doesn't already have.
+
+ e) Close all open mailboxes not required for further operations (if
+ staying online) or disconnect all open connections (if going
+ offline).
+
+
+
+
+Melnikov Informational [Page 5]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ Terms used:
+
+ "Actions" are queued requests that were made by the human to the
+ client's Mail User Agent (MUA) software while the client was
+ disconnected.
+
+ We define "descriptors" as a set of IMAP4 FETCH data items.
+ Conceptually, a message's descriptor is that set of information that
+ allows the synchronization program to decide what protocol actions
+ are necessary to bring the local cache to the desired state for this
+ message; since this decision is really up to the human, this
+ information probably includes at least a few header fields intended
+ for human consumption. Exactly what will constitute a descriptor
+ depends on the client implementation. At a minimum, the descriptor
+ contains the message's UID and FLAGS. Other likely candidates are
+ the RFC822.SIZE, RFC822.HEADER, BODYSTRUCTURE, or ENVELOPE data
+ items.
+
+ Comments:
+
+ 1) The list of actions should be ordered. For example, if the human
+ deletes message A1 in mailbox A, then expunges mailbox A, and then
+ deletes message A2 in mailbox A, the human will expect that
+ message A1 is gone and that message A2 is still present but is now
+ deleted.
+
+ By processing all the actions before proceeding with
+ synchronization, we avoid having to compensate for the local MUA's
+ changes to the server's state. That is, once we have processed
+ all the pending actions, the steps that the client must take to
+ synchronize itself will be the same no matter where the changes to
+ the server's state originated.
+
+ 2) Steps a and b can be performed in parallel. Alternatively, step a
+ can be performed after d.
+
+ 3) On step b, the set of "interesting" mailboxes pretty much has to
+ be determined by the human. What mailboxes belong to this set may
+ vary between different IMAP4 sessions with the same server,
+ client, and human. An interesting mailbox can be a mailbox
+ returned by LSUB command (see Section 6.3.9 of [IMAP4]). The
+ special mailbox "INBOX" SHOULD be in the default set of mailboxes
+ that the client considers interesting. However, providing the
+ ability to ignore INBOX for a particular session or client may be
+ valuable for some mail filtering strategies.
+
+
+
+
+
+
+Melnikov Informational [Page 6]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ 4) On step d-2-II, the client also finds out about changes to the
+ flags of messages that the client already has in its local cache,
+ and about messages in the local cache that no longer exist on the
+ server (i.e., messages that have been expunged).
+
+ 5) "Interesting" messages are those messages that the synchronization
+ program thinks the human wants to have cached locally, based on
+ the configuration and the data retrieved in step b.
+
+ 6) A disconnected IMAP client is a special case of an IMAP client, so
+ it MUST be able to handle any "unexpected" unsolicited responses,
+ like EXISTS and EXPUNGE, at any time. The disconnected client MAY
+ ignore EXPUNGE response during "client-to-server" synchronization
+ phase (step c).
+
+ The rest of this discussion will focus primarily on the
+ synchronization issues for a single mailbox.
+
+4. Mailbox Synchronization Steps and Strategies
+
+4.1. Checking UID Validity
+
+ The "UID validity" of a mailbox is a number returned in an
+ UIDVALIDITY response code in an OK untagged response at mailbox
+ selection time. The UID validity value changes between sessions when
+ UIDs fail to persist between sessions.
+
+ Whenever the client selects a mailbox, the client must compare the
+ returned UID validity value with the value stored in the local cache.
+ If the UID validity values differ, the UIDs in the client's cache are
+ no longer valid. The client MUST then empty the local cache of that
+ mailbox and remove any pending "actions" that refer to UIDs in that
+ mailbox. The client MAY also issue a warning to the human. The
+ client MUST NOT cancel any scheduled uploads (i.e., APPENDs) for the
+ mailbox.
+
+ Note that UIDVALIDITY is not only returned on a mailbox selection.
+ The COPYUID and APPENDUID response codes defined in the [UIDPLUS]
+ extension (see also 4.2.2) and the UIDVALIDITY STATUS response data
+ item also contain a UIDVALIDITY value for some other mailbox. The
+ client SHOULD behave as described in the previous paragraph (but it
+ should act on the other mailbox's cache), no matter how it obtained
+ the UIDVALIDITY value.
+
+
+
+
+
+
+
+
+Melnikov Informational [Page 7]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+4.2. Synchronizing Local Changes with the Server
+
+4.2.1. Uploading Messages to the Mailbox
+
+ Two of the most common examples of operations resulting in message
+ uploads are:
+
+ 1) Saving a draft message
+
+ 2) Copying a message between remote mailboxes on two different IMAP
+ servers or a local mailbox and a remote mailbox.
+
+ Message upload is performed with the APPEND command. A message
+ scheduled to be uploaded has no UID associated with it, as all UIDs
+ are assigned by the server. The APPEND command will effectively
+ associate a UID with the uploaded message that can be stored in the
+ local cache for future reference. However, [IMAP4] doesn't describe
+ a simple mechanism to discover the message UID by just performing the
+ APPEND command. In order to discover the UID, the client can do one
+ of the following:
+
+ 1) Remove the uploaded message from cache. Then, use the mechanism
+ described in 4.3 to fetch the information about the uploaded
+ message as if it had been uploaded by some other client.
+
+ 2) Try to fetch header information as described in 4.2.2 in order to
+ find a message that corresponds to the uploaded message. One
+ strategy for doing this is described in 4.2.2.
+
+ Case 1 describes a not particularly smart client.
+
+ C: A003 APPEND Drafts (\Seen $MDNSent) {310}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK APPEND Completed
+
+ Fortunately, there is a simpler way to discover the message UID in
+ the presence of the [UIDPLUS] extension:
+
+
+
+
+Melnikov Informational [Page 8]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ C: A003 APPEND Drafts (\Seen $MDNSent) {310}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK [APPENDUID 1022843275 77712] APPEND completed
+
+ The UID of the appended message is the second parameter of APPENDUID
+ response code.
+
+4.2.2. Optimizing "move" and "copy" Operations
+
+ Practical experience with IMAP and other mailbox access protocols
+ that support multiple mailboxes suggests that moving a message from
+ one mailbox to another is an extremely common operation.
+
+4.2.2.1. Moving a Message between Two Mailboxes on the Same Server
+
+ In IMAP4, a "move" operation between two mailboxes on the same server
+ is really a combination of a COPY operation and a STORE +FLAGS
+ (\Deleted) operation. This makes good protocol sense for IMAP, but
+ it leaves a simple-minded disconnected client in the silly position
+ of deleting and possibly expunging its cached copy of a message, then
+ fetching an identical copy via the network.
+
+ However, the presence of the UIDPLUS extension in the server can
+ help:
+
+ C: A001 UID COPY 567,414 "Interesting Messages"
+ S: A001 OK [COPYUID 1022843275 414,567 5:6] Completed
+
+ This tells the client that the message with UID 414 in the current
+ mailbox was successfully copied to the mailbox "Interesting Messages"
+ and was given the UID 5, and that the message with UID 567 was given
+ the UID 6.
+
+ In the absence of UIDPLUS extension support in the server, the
+ following trick can be used. By including the Message-ID: header and
+ the INTERNALDATE data item as part of the descriptor, the client can
+ check the descriptor of a "new" message against messages that are
+ already in its cache and avoid fetching the extra copy. Of course,
+
+
+
+Melnikov Informational [Page 9]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ it's possible that the cost of checking to see if the message is
+ already in the local cache may exceed the cost of just fetching it,
+ so this technique should not be used blindly. If the MUA implements
+ a "move" command, it makes special provisions to use this technique
+ when it knows that a copy/delete sequence is the result of a "move"
+ command.
+
+ Note that servers are not required (although they are strongly
+ encouraged with "SHOULD language") to preserve INTERNALDATE when
+ copying messages.
+
+ Also note that since it's theoretically possible for this algorithm
+ to find the wrong message (given sufficiently malignant Message-ID
+ headers), implementers should provide a way to disable this
+ optimization, both permanently and on a message-by-message basis.
+
+ Example 1: Copying a message in the absence of UIDPLUS extension.
+
+ At some point in time the client has fetched the source message and
+ some information was cached:
+
+ C: C021 UID FETCH <uids> (BODY.PEEK[] INTERNALDATE FLAGS)
+ ...
+ S: * 27 FETCH (UID 123 INTERNALDATE "31-May-2002 05:26:59 -0600"
+ FLAGS (\Draft $MDNSent) BODY[] {1036}
+ S: ...
+ S: Message-Id: <20040903110856.22a127cd@chardonnay>
+ S: ...
+ S: ...message body...
+ S: )
+ ...
+ S: C021 OK fetch completed
+
+ Later on, the client decides to copy the message:
+
+ C: C035 UID COPY 123 "Interesting Messages"
+ S: C035 OK Completed
+
+ As the server hasn't provided the COPYUID response code, the client
+ tries the optimization described above:
+
+ C: C036 SELECT "Interesting Messages"
+ ...
+ C: C037 UID SEARCH ON 31-May-2002 HEADER
+ "Message-Id" "20040903110856.22a127cd@chardonnay"
+ S: SEARCH 12368
+ S: C037 OK completed
+
+
+
+
+Melnikov Informational [Page 10]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ Note that if the server has returned multiple UIDs in the SEARCH
+ response, the client MUST NOT use any of the returned UID.
+
+4.2.2.2. Moving a Message from a Remote Mailbox to a Local
+
+ Moving a message from a remote mailbox to a local is done with FETCH
+ (that includes FLAGS and INTERNALDATE) followed by UID STORE <uid>
+ +FLAGS.SILENT (\Deleted):
+
+ C: A003 UID FETCH 123 (BODY.PEEK[] INTERNALDATE FLAGS)
+ S: * 27 FETCH (UID 123 INTERNALDATE "31-May-2002 05:26:59 -0600"
+ FLAGS (\Seen $MDNSent) BODY[]
+ S: ...message body...
+ S: )
+ S: A003 OK UID FETCH completed
+ C: A004 UID STORE <uid> +FLAGS.SILENT (\Deleted)
+ S: A004 STORE completed
+
+ Note that there is no reason to fetch the message during
+ synchronization if it's already in the client's cache. Also, the
+ client SHOULD preserve delivery date in the local cache.
+
+4.2.2.3. Moving a Message from a Local Mailbox to a Remote
+
+ Moving a message from a local mailbox to a remote is done with
+ APPEND:
+
+ C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+ {310}
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK [APPENDUID 1022843275 77712] completed
+
+ The client SHOULD specify the delivery date from the local cache in
+ the APPEND.
+
+ If the [LITERAL+] extension is available, the client can save a
+ round-trip*:
+
+
+
+
+Melnikov Informational [Page 11]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+ {310+}
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C:
+ S: A003 OK [APPENDUID 1022843275 77712] completed
+
+ * Note that there is a risk that the server will reject the message
+ due to its size. If this happens, the client will waste bandwidth
+ transferring the whole message. If the client wouldn't have used
+ the LITERAL+, this could have been avoided:
+
+ C: A003 APPEND Drafts (\Seen $MDNSent) "31-May-2004 05:26:59 -0600"
+ {16777215}
+ S: A003 NO Sorry, message is too big
+
+4.2.2.4. Moving a Message between Two Mailboxes on Different Servers
+
+ Moving a message between two mailbox on two different servers is a
+ combination of the operations described in 4.2.2.2 followed by the
+ operations described in 4.2.2.3.
+
+4.2.2.5. Uploading Multiple Messages to a Remote Mailbox with
+ MULTIAPPEND
+
+ When there is a need to upload multiple messages to a remote mailbox
+ (e.g., as per 4.2.2.3), the presence of certain IMAP extensions may
+ significantly improve performance. One of them is [MULTIAPPEND].
+
+ For some mail stores, opening a mailbox for appending might be
+ expensive. [MULTIAPPEND] tells the server to open the mailbox once
+ (instead of opening and closing it "n" times per "n" messages to be
+ uploaded) and to keep it open while a group of messages is being
+ uploaded to the server.
+
+ Also, if the server supports both [MULTIAPPEND] and [LITERAL+]
+ extensions, the entire upload is accomplished in a single
+ command/response round-trip.
+
+
+
+
+
+
+Melnikov Informational [Page 12]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ Note: Client implementers should be aware that [MULTIAPPEND] performs
+ append of multiple messages atomically. This means, for example, if
+ there is not enough space to save "n"-th message (or the message has
+ invalid structure and is rejected by the server) after successful
+ upload of "n-1" messages, the whole upload operation fails, and no
+ message will be saved in the mailbox. Although this behavior might
+ be desirable in certain situations, it might not be what you want.
+ Otherwise, the client should use the regular APPEND command (Section
+ 4.2.2.3), possibly utilizing the [LITERAL+] extension. See also
+ Section 5.1 for discussions about error recovery.
+
+ Note: MULTIAPPEND can be used together with the UIDPLUS extension in
+ a way similar to what was described in Section 4.2.1. [MULTIAPPEND]
+ extends the syntax of the APPENDUID response code to allow for
+ multiple message UIDs in the second parameter.
+
+ Example 2:
+
+ This example demonstrates the use of MULTIAPPEND together with
+ UIDPLUS (synchronization points where the client waits for
+ confirmations from the server are marked with "<--->"):
+
+ C: A003 APPEND Jan-2002 (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+ {310}
+ <--->
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C: (\Seen) " 1-Jun-2002 22:43:04 -0800" {286}
+ <--->
+ S: + Ready for literal data
+ C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+ C: From: Joe Mooch <mooch@OWaTaGu.siam.EDU>
+ C: Subject: Re: afternoon meeting
+ C: To: foobar@blt.example.com
+ C: Message-Id: <a0434793874930@OWaTaGu.siam.EDU>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: 3:30 is fine with me.
+ C:
+
+
+
+Melnikov Informational [Page 13]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ S: A003 OK [APPENDUID 1022843275 77712,77713] completed
+
+ The upload takes 3 round-trips.
+
+ Example 3:
+
+ In this example, Example 2 was modified for the case when the server
+ supports MULTIAPPEND, LITERAL+, and UIDPLUS. The upload takes only 1
+ round-trip.
+
+ C: A003 APPEND Jan-2002 (\Seen $MDNSent) "31-May-2002 05:26:59 -0600"
+ {310+}
+ C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
+ C: From: Fred Foobar <foobar@blt.example.COM>
+ C: Subject: afternoon meeting
+ C: To: mooch@owatagu.siam.edu
+ C: Message-Id: <B27397-0100000@blt.example.COM>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: Hello Joe, do you think we can meet at 3:30 tomorrow?
+ C: (\Seen) " 1-Jun-2002 22:43:04 -0800" {286+}
+ C: Date: Mon, 7 Feb 1994 22:43:04 -0800 (PST)
+ C: From: Joe Mooch <mooch@OWaTaGu.siam.EDU>
+ C: Subject: Re: afternoon meeting
+ C: To: foobar@blt.example.com
+ C: Message-Id: <a0434793874930@OWaTaGu.siam.EDU>
+ C: MIME-Version: 1.0
+ C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
+ C:
+ C: 3:30 is fine with me.
+ C:
+ S: A003 OK [APPENDUID 1022843275 77712,77713] completed
+
+4.2.3. Replaying Local Flag Changes
+
+ The disconnected client uses the STORE command to synchronize local
+ flag state with the server. The disconnected client SHOULD use
+ +FLAGS.SILENT or -FLAGS.SILENT in order to set or unset flags
+ modified by the user while offline. The FLAGS form MUST NOT be used,
+ as there is a risk that this will overwrite flags on the server that
+ have been changed by some other client.
+
+ Example 4:
+
+ For the message with UID 15, the disconnected client stores the
+ following flags \Seen and $Highest. The flags were modified on the
+ server by some other client: \Seen, \Answered, and $Highest. While
+
+
+
+Melnikov Informational [Page 14]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ offline, the user requested that the $Highest flags be removed and
+ that the \Deleted flag be added. The flag synchronization sequence
+ for the message should look like:
+
+ C: A001 UID STORE 15 +FLAGS.SILENT (\Deleted)
+ S: A001 STORE completed
+ C: A002 UID STORE 15 -FLAGS.SILENT ($Highest)
+ S: A002 STORE completed
+
+ If the disconnected client is able to store an additional binary
+ state information (or a piece of information that can take a value
+ from a predefined set of values) in the local cache of an IMAP
+ mailbox or in a local mailbox (e.g., message priority), and if the
+ server supports storing of arbitrary keywords, the client MUST use
+ keywords to store this state on the server.
+
+ Example 5:
+
+ Imagine a speculative mail client that can mark a message as one of
+ work-related ($Work), personal ($Personal), or spam ($Spam). In
+ order to mark a message as personal, the client issues:
+
+ C: A001 UID STORE 15 +FLAGS.SILENT ($Personal)
+ S: A001 STORE completed
+ C: A002 UID STORE 15 -FLAGS.SILENT ($Work $Spam)
+ S: A002 STORE completed
+
+ In order to mark the message as not work, not personal and not spam,
+ the client issues:
+
+ C: A003 UID STORE 15 -FLAGS.SILENT ($Personal $Work $Spam)
+ S: A003 STORE completed
+
+4.2.4. Processing Mailbox Compression (EXPUNGE) Requests
+
+ A naive disconnected client implementation that supports compressing
+ a mailbox while offline may decide to issue an EXPUNGE command to the
+ server in order to expunge messages marked \Deleted. The problem
+ with this command during synchronization is that it permanently
+ erases all messages with the \Deleted flag set, i.e., even those
+ messages that were marked as \Deleted on the server while the user
+ was offline. Doing this might result in an unpleasant surprise for
+ the user.
+
+ Fortunately the [UIDPLUS] extension can help in this case as well.
+ The extension introduces UID EXPUNGE command, that, unlike EXPUNGE,
+ takes a UID set parameter, that lists UIDs of all messages that can
+ be expunged. When processing this command the server erases only
+
+
+
+Melnikov Informational [Page 15]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ messages with \Deleted flag listed in the UID list. Thus, messages
+ not listed in the UID set will not be expunged even if they have the
+ \Deleted flag set.
+
+ Example 6:
+
+ While the user was offline, 3 messages with UIDs 7, 27, and 65 were
+ marked \Deleted when the user requested to compress the open mailbox.
+ Another client marked a message \Deleted on the server (UID 34).
+ During synchronization, the disconnected client issues:
+
+ C: A001 UID EXPUNGE 7,27,65
+ S: * ... EXPUNGE
+ S: * ... EXPUNGE
+ S: * ... EXPUNGE
+ S: A001 UID EXPUNGE completed
+
+ If another client issues UID SEARCH DELETED command (to find all
+ messages with the \Deleted flag) before and after the UID EXPUNGE, it
+ will get:
+
+ Before:
+
+ C: B001 UID SEARCH DELETED
+ S: * SEARCH 65 34 27 7
+ S: B001 UID SEARCH completed
+
+ After:
+
+ C: B002 UID SEARCH DELETED
+ S: * SEARCH 34
+ S: B002 UID SEARCH completed
+
+ In the absence of the [UIDPLUS] extension, the following sequence of
+ commands can be used as an approximation. Note: It's possible for
+ another client to mark additional messages as deleted while this
+ sequence is being performed. In this case, these additional messages
+ will be expunged as well.
+
+ 1) Find all messages marked \Deleted on the server.
+
+ C: A001 UID SEARCH DELETED
+ S: * SEARCH 65 34 27 7
+ S: A001 UID SEARCH completed
+
+ 2) Find all messages that must not be erased (for the previous
+ example the list will consist of the message with UID 34).
+
+
+
+
+Melnikov Informational [Page 16]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ 3) Temporarily remove \Deleted flag on all messages found in step 2.
+
+ C: A002 UID STORE 34 -FLAGS.SILENT (\Deleted)
+ S: A002 UID STORE completed
+
+ 4) Expunge the mailbox.
+
+ C: A003 EXPUNGE
+ S: * 20 EXPUNGE
+ S: * 7 EXPUNGE
+ S: * 1 EXPUNGE
+ S: A003 EXPUNGE completed
+
+ Here, the message with UID 7 has message number 1, with UID 27 has
+ message number 7, and with UID 65 has message number 20.
+
+ 5) Restore \Deleted flag on all messages found when performing step
+ 2.
+
+ C: A004 UID STORE 34 +FLAGS.SILENT (\Deleted)
+ S: A004 UID STORE completed
+
+4.2.5. Closing a Mailbox
+
+ When the disconnected client has to close a mailbox, it should not
+ use the CLOSE command, because CLOSE does a silent EXPUNGE. (Section
+ 4.2.4 explains why EXPUNGE should not be used by a disconnected
+ client.) It is safe to use CLOSE only if the mailbox was opened with
+ EXAMINE.
+
+ If the mailbox was opened with SELECT, the client can use one of the
+ following commands to implicitly close the mailbox and prevent the
+ silent expunge:
+
+ 1) UNSELECT - This is a command described in [UNSELECT] that works as
+ CLOSE, but doesn't cause the silent EXPUNGE. This command is
+ supported by the server if it reports UNSELECT in its CAPABILITY
+ list.
+
+ 2) SELECT <another_mailbox> - SELECT causes implicit CLOSE without
+ EXPUNGE.
+
+ 3) If the client intends to issue LOGOUT after closing the mailbox,
+ it may just issue LOGOUT, because LOGOUT causes implicit CLOSE
+ without EXPUNGE as well.
+
+ 4) SELECT <non_existing_mailbox> - If the client knows a mailbox that
+ doesn't exist or can't be selected, it MAY SELECT it.
+
+
+
+Melnikov Informational [Page 17]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ If the client opened the mailbox with SELECT and just wants to avoid
+ implicit EXPUNGE without closing the mailbox, it may also use the
+ following:
+
+ 5) EXAMINE <mailbox> - Reselect the same mailbox in read-only mode.
+
+4.3. Details of "Normal" Synchronization of a Single Mailbox
+
+ The most common form of synchronization is where the human trusts the
+ integrity of the client's copy of the state of a particular mailbox
+ and simply wants to bring the client's cache up to date so that it
+ accurately reflects the mailbox's current state on the server.
+
+4.3.1. Discovering New Messages and Changes to Old Messages
+
+ Let <lastseenuid> represent the highest UID that the client knows
+ about in this mailbox. Since UIDs are allocated in strictly
+ ascending order, this is simply the UID of the last message in the
+ mailbox that the client knows about. Let <lastseenuid+1> represent
+ <lastseenuid>'s UID plus one. Let <descriptors> represent a list
+ consisting of all the FETCH data item items that the implementation
+ considers part of the descriptor; at a minimum this is just the FLAGS
+ data item, but it usually also includes BODYSTRUCTURE and
+ RFC822.SIZE. At this step, <descriptors> SHOULD NOT include RFC822.
+
+ With no further information, the client can issue the following two
+ commands:
+
+ tag1 UID FETCH <lastseenuid+1>:* <descriptors>
+ tag2 UID FETCH 1:<lastseenuid> FLAGS
+
+ The first command will request some information about "new" messages
+ (i.e., messages received by the server since the last
+ synchronization). It will also allow the client to build a message
+ number to UID map (only for new messages). The second command allows
+ the client to
+
+ 1) update cached flags for old messages;
+
+ 2) find out which old messages got expunged; and
+
+ 3) build a mapping between message numbers and UIDs (for old
+ messages).
+
+ The order here is significant. We want the server to start returning
+ the list of new message descriptors as fast as it can, so that the
+ client can start issuing more FETCH commands, so we start out by
+ asking for the descriptors of all the messages we know the client
+
+
+
+Melnikov Informational [Page 18]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ cannot possibly have cached yet. The second command fetches the
+ information we need to determine what changes may have occurred to
+ messages that the client already has cached. Note that the former
+ command should only be issued if the UIDNEXT value cached by the
+ client differs from the one returned by the server. Once the client
+ has issued these two commands, there's nothing more the client can do
+ with this mailbox until the responses to the first command start
+ arriving. A clever synchronization program might use this time to
+ fetch its local cache state from disk or to start the process of
+ synchronizing another mailbox.
+
+ The following is an example of the first FETCH:
+
+ C: A011 UID fetch 131:* (FLAGS BODYSTRUCTURE INTERNALDATE
+ RFC822.SIZE)
+
+ Note 1: The first FETCH may result in the server's sending a huge
+ volume of data. A smart disconnected client should use message
+ ranges (see also Section 3.2.1.2 of [RFC2683]), so that the user is
+ able to execute a different operation between fetching information
+ for a group of new messages.
+
+ Example 7:
+
+ Knowing the new UIDNEXT returned by the server on SELECT or EXAMINE
+ (<uidnext>), the client can split the UID range
+ <lastseenuid+1>:<uidnext> into groups, e.g., 100 messages. After
+ that, the client can issue:
+
+ C: A011 UID fetch <lastseenuid+1>:<lastseenuid+100>
+ (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+ ...
+ C: A012 UID fetch <lastseenuid+101>:<lastseenuid+200>
+ (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+ ...
+ ...
+ C: A0FF UID fetch <lastseenuid+901>:<uidnext>
+ (FLAGS BODYSTRUCTURE INTERNALDATE RFC822.SIZE)
+
+ Note that unless a SEARCH command is issued, it is impossible to
+ determine how many messages will fall into a subrange, as UIDs are
+ not necessarily contiguous.
+
+ Note 2: The client SHOULD ignore any unsolicited EXPUNGE responses
+ received during the first FETCH command. EXPUNGE responses contain
+ message numbers that are useless to a client that doesn't have the
+ message-number-to-UID translation table.
+
+
+
+
+Melnikov Informational [Page 19]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ The second FETCH command will result in zero or more untagged fetch
+ responses. Each response will have a corresponding UID FETCH data
+ item. All messages that didn't have a matching untagged FETCH
+ response MUST be removed from the local cache.
+
+ For example, if the <lastseenuid> had a value 15000 and the local
+ cache contained 3 messages with the UIDs 12, 777, and 14999,
+ respectively, then after receiving the following responses from the
+ server, the client must remove the message with UID 14999 from its
+ local cache.
+
+ S: * 1 FETCH (UID 12 FLAGS (\Seen))
+ S: * 2 FETCH (UID 777 FLAGS (\Answered \Deleted))
+
+ Note 3: If the client is not interested in flag changes (i.e., the
+ client only wants to know which old messages are still on the
+ server), the second FETCH command can be substituted with:
+
+ tag2 UID SEARCH UID 1:<lastseenuid>
+
+ This command will generate less traffic. However, an implementor
+ should be aware that in order to build the mapping table from message
+ numbers to UIDs, the output of the SEARCH command MUST be sorted
+ first, because there is no requirement for a server to return UIDs in
+ SEARCH response in any particular order.
+
+4.3.2. Searching for "Interesting" Messages.
+
+ This step is performed entirely on the client (from the information
+ received in the step described in 4.3.1), entirely on the server, or
+ on some combination of both. The decision on what is an
+ "interesting" message is up to the client software and the human.
+ One easy criterion that should probably be implemented in any client
+ is whether the message is "too big" for automatic retrieval, where
+ "too big" is a parameter defined in the client's configuration.
+
+ Another commonly used criterion is the age of a message. For
+ example, the client may choose to download only messages received in
+ the last week (in this case, <date> would be today's date minus 7
+ days):
+
+ tag3 UID SEARCH UID <uidset> SINCE <date>
+
+ Keep in mind that a date search disregards time and time zone. The
+ client can avoid doing this search if it specified INTERNALDATE in
+ <descriptors> on the step described in 4.3.1. If the client did, it
+ can perform the local search on its message cache.
+
+
+
+
+Melnikov Informational [Page 20]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ At this step, the client also decides what kind of information about
+ a particular message to fetch from the server. In particular, even
+ for a message that is considered "too big", the client MAY choose to
+ fetch some part(s) of it. For example, if the message is a
+ multipart/mixed containing a text part and a MPEG attachment, there
+ is no reason for the client not to fetch the text part. The decision
+ of which part should or should not be fetched can be based on the
+ information received in the BODYSTRUCTURE FETCH response data item
+ (i.e., if BODYSTRUCTURE was included in <descriptors> on the step
+ described in 4.3.1).
+
+4.3.3. Populating Cache with "Interesting" Messages.
+
+ Once the client has found out which messages are "interesting", it
+ can start issuing appropriate FETCH commands for "interesting"
+ messages or parts thereof.
+
+ Note that fetching a message into the disconnected client's local
+ cache does NOT imply that the human has (or even will) read the
+ message. Thus, the synchronization program for a disconnected client
+ should always be careful to use the .PEEK variants of the FETCH data
+ items that implicitly set the \Seen flag.
+
+ Once the last descriptor has arrived and the last FETCH command has
+ been issued, the client simply needs to process the incoming fetch
+ items and use them to update the local message cache.
+
+ In order to avoid deadlock problems, the client must give processing
+ of received messages priority over issuing new FETCH commands during
+ this synchronization process. This may necessitate temporary local
+ queuing of FETCH requests that cannot be issued without causing a
+ deadlock. In order to achieve the best use of the "expensive"
+ network connection, the client will almost certainly need to pay
+ careful attention to any flow-control information that it can obtain
+ from the underlying transport connection (usually a TCP connection).
+
+ Note: The requirement stated in the previous paragraph might result
+ in an unpleasant user experience, if followed blindly. For example,
+ the user might be unwilling to wait for the client to finish
+ synchronization before starting to process the user's requests. A
+ smart disconnected client should allow the user to perform requested
+ operations in between IMAP commands that are part of the
+ synchronization process. See also Note 1 in Section 4.3.1.
+
+
+
+
+
+
+
+
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+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ Example 8:
+
+ After fetching a message BODYSTRUCTURE, the client discovers a
+ complex MIME message. Then, it decides to fetch MIME headers of the
+ nested MIME messages and some body parts.
+
+ C: A011 UID fetch 11 (BODYSTRUCTURE)
+ S: ...
+ C: A012 UID fetch 11 (BODY[HEADER] BODY[1.MIME] BODY[1.1.MIME]
+ BODY[1.2.MIME] BODY[2.MIME] BODY[3.MIME] BODY[4.MIME]
+ BODY[5.MIME] BODY[6.MIME] BODY[7.MIME] BODY[8.MIME] BODY[9.MIME]
+ BODY[10.MIME] BODY[11.MIME] BODY[12.MIME] BODY[13.MIME]
+ BODY[14.MIME] BODY[15.MIME] BODY[16.MIME] BODY[17.MIME]
+ BODY[18.MIME] BODY[19.MIME] BODY[20.MIME] BODY[21.MIME])
+ S: ...
+ C: A013 UID fetch 11 (BODY[1.1] BODY[1.2])
+ S: ...
+ C: A014 UID fetch 11 (BODY[3] BODY[4] BODY[5] BODY[6] BODY[7] BODY[8]
+ BODY[9] BODY[10] BODY[11] BODY[13] BODY[14] BODY[15] BODY[16]
+ BODY[21])
+ S: ...
+
+4.3.4. User-Initiated Synchronization
+
+ After the client has finished the main synchronization process as
+ described in Sections 4.3.1-4.3.3, the user may optionally request
+ additional synchronization steps while the client is still online.
+ This is not any different from the process described in Sections
+ 4.3.2 and 4.3.3.
+
+ Typical examples are:
+
+ 1) fetch all messages selected in UI.
+ 2) fetch all messages marked as \Flagged on the server.
+
+4.4. Special Case: Descriptor-Only Synchronization
+
+ For some mailboxes, fetching the descriptors might be the entire
+ synchronization step. Practical experience with IMAP has shown that
+ a certain class of mailboxes (e.g., "archival" mailboxes) are used
+ primarily for long-term storage of important messages that the human
+ wants to have instantly available on demand but does not want
+ cluttering up the disconnected client's cache at any other time.
+ Messages in this kind of mailbox would be fetched exclusively by
+ explicit actions queued by the local MUA. Thus, the only
+ synchronization desirable on this kind of mailbox is fetching enough
+ descriptor information for the user to be able to identify messages
+ for subsequent download.
+
+
+
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+
+
+ Special mailboxes that receive messages from a high volume, low
+ priority mailing list might also be in this category, at least when
+ the human is in a hurry.
+
+4.5. Special Case: Fast New-Only Synchronization
+
+ In some cases, the human might be in such a hurry that he or she
+ doesn't care about changes to old messages, just about new messages.
+ In this case, the client can skip the UID FETCH command that obtains
+ the flags and UIDs for old messages (1:<lastseenuid>).
+
+4.6. Special Case: Blind FETCH
+
+ In some cases, the human may know (for whatever reason) that he or
+ she always wants to fetch any new messages in a particular mailbox,
+ unconditionally. In this case, the client can just fetch the
+ messages themselves, rather than just the descriptors, by using a
+ command like:
+
+ tag1 UID FETCH <lastseenuid+1>:* (FLAGS BODY.PEEK[])
+
+ Note that this example ignores the fact that the messages can be
+ arbitrary long. The disconnected client MUST always check for
+ message size before downloading, unless explicitly told otherwise. A
+ well-behaved client should instead use something like the following:
+
+ 1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS RFC822.SIZE)".
+
+ 2) From the message sizes returned in step 1, construct UID set
+ <required_messages>.
+
+ 3) Issue "tag2 UID FETCH <required_messages> (BODY.PEEK[])".
+
+ or
+
+ 1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS)".
+
+ 2) Construct UID set <old_uids> from the responses of step 1.
+
+ 3) Issue "tag2 SEARCH UID <old_uids> SMALLER <message_limit>".
+ Construct UID set <required_messages> from the result of the
+ SEARCH command.
+
+ 4) Issue "tag3 UID FETCH <required_messages> (BODY.PEEK[])".
+
+
+
+
+
+
+
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+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ or
+
+ 1) Issue "tag1 UID FETCH <lastseenuid+1>:* (FLAGS
+ BODY.PEEK[]<0.<length>>)", where <length> should be replaced with
+ the maximal message size the client is willing to download.
+
+ Note: In response to such a command, the server will only return
+ partial data if the message is longer than <length>. It will
+ return the full message data for any message whose size is smaller
+ than or equal to <length>. In the former case, the client will
+ not be able to extract the full MIME structure of the message from
+ the truncated data, so the client should include BODYSTRUCTURE in
+ the UID FETCH command as well.
+
+5. Implementation Considerations
+
+ Below are listed some common implementation pitfalls that should be
+ considered when implementing a disconnected client.
+
+ 1) Implementing fake UIDs on the client.
+
+ A message scheduled to be uploaded has no UID, as UIDs are
+ selected by the server. The client may implement fake UIDs
+ internally in order to reference not-yet-uploaded messages in
+ further operations. (For example, a message could be scheduled to
+ be uploaded, but subsequently marked as deleted or copied to
+ another mailbox). Here, the client MUST NOT under any
+ circumstances send these fake UIDs to the server. Also, client
+ implementers should be reminded that according to [IMAP4] a UID is
+ a 32-bit unsigned integer excluding 0. So, both 4294967295 and
+ 2147483648 are valid UIDs, and 0 and -1 are both invalid. Some
+ disconnected mail clients have been known to send negative numbers
+ (e.g., "-1") as message UIDs to servers during synchronization.
+
+ Situation 1: The user starts composing a new message, edits it,
+ saves it, continues to edit it, and saves it again.
+
+ A disconnected client may record in its replay log (log of
+ operations to be replayed on the server during synchronization)
+ the sequence of operations as shown below. For the purpose of
+ this situation, we assume that all draft messages are stored in
+ the mailbox called Drafts on an IMAP server. We will also use the
+ following conventions: <old_uid> is the UID of the intermediate
+ version of the draft when it was saved for the first time. This
+ is a fake UID generated on the client. <new_uid> is the UID of
+ the final version of the draft. This is another fake UID
+ generated on the client.
+
+
+
+
+Melnikov Informational [Page 24]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ 1) APPEND Drafts (\Seen $MDNSent \Drafts) {<nnn>}
+ ...first version of the message follows...
+
+ 2) APPEND Drafts (\Seen $MDNSent \Drafts) {<mmm>}
+ ...final version of the message follows...
+
+ 3) STORE <old_uid> +FLAGS (\Deleted)
+
+ Step 1 corresponds to the first attempt to save the draft message,
+ step 2 corresponds to the second attempt to save the draft
+ message, and step 3 deletes the first version of the draft message
+ saved in step 1.
+
+ A naive disconnected client may send the command in step 3 without
+ replacing the fake client generated <old_uid> with the value
+ returned by the server in step 1. A server will probably reject
+ this command, which will make the client believe that the
+ synchronization sequence has failed.
+
+ 2) Section 5.1 discusses common implementation errors related to
+ error recovery during playback.
+
+ 3) Don't assume that the disconnected client is the only client used
+ by the user.
+
+ Situation 2: Some clients may use the \Deleted flag as an
+ indicator that the message should not appear in the user's view.
+ Usage of the \Deleted flag for this purpose is not safe, as other
+ clients (e.g., online clients) might EXPUNGE the mailbox at any
+ time.
+
+ 4) Beware of data dependencies between synchronization operations.
+
+ It might be very tempting for a client writer to perform some
+ optimizations on the playback log. Such optimizations might
+ include removing redundant operations (for example, see
+ optimization 2 in Section 5.3), or their reordering.
+
+ It is not always safe to reorder or remove redundant operations
+ during synchronization because some operations may have
+ dependencies (as Situation 3 demonstrates). So, if in doubt,
+ don't do this.
+
+ Situation 3: The user copies a message out of a mailbox and then
+ deletes the mailbox.
+
+
+
+
+
+
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+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ C: A001 SELECT Old-Mail
+ S: ...
+ C: A002 UID COPY 111 ToDo
+ S: A002 OK [COPYUID 1022843345 111 94] Copy completed
+ ...
+ C: A015 CLOSE
+ S: A015 OK Completed
+ C: A016 DELETE Old-Mail
+ S: A016 OK Mailbox deletion completed successfully
+
+ If the client performs DELETE (tag A016) first and COPY (tag A002)
+ second, then the COPY fails. Also, the message that the user so
+ carefully copied into another mailbox has been lost.
+
+5.1. Error Recovery during Playback
+
+ Error recovery during synchronization is one of the trickiest parts
+ to get right. Below, we will discuss certain error conditions and
+ suggest possible choices for handling them.
+
+ 1) Lost connection to the server.
+
+ The client MUST remember the current position in the playback
+ (replay) log and replay it starting from the interrupted operation
+ (the last command issued by the client, but not acknowledged by
+ the server) the next time it successfully connects to the same
+ server. If the connection was lost while executing a non-
+ idempotent IMAP command (see the definition in Section 1), then
+ when the client is reconnected, it MUST make sure that the
+ interrupted command was indeed not executed. If it wasn't
+ executed, the client must restart playback from the interrupted
+ command, otherwise from the following command.
+
+ Upon reconnect, care must be taken in order to properly reapply
+ logical operations that are represented by multiple IMAP commands,
+ e.g., UID EXPUNGE emulation when UID EXPUNGE is not supported by
+ the server (see Section 4.2.4).
+
+ Once the client detects that the connection to the server was
+ lost, it MUST stop replaying its log. There are existing
+ disconnected clients that, to the great annoyance of users, pop up
+ an error dialog for each and every playback operation that fails.
+
+ 2) Copying/appending messages to a mailbox that doesn't exist. (The
+ server advertises this condition by sending the TRYCREATE response
+ code in the tagged NO response to the APPEND or COPY command.)
+
+
+
+
+
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+
+
+ The user should be advised about the situation and be given one of
+ the following choices:
+
+ a) Try to recreate a mailbox.
+ b) Copy/upload messages to another mailbox.
+ c) Skip copy/upload.
+ d) Abort replay.
+
+ 3) Copying messages from a mailbox that doesn't exist, or renaming or
+ getting/changing ACLs [ACL] on a mailbox that doesn't exist:
+
+ a) Skip operation.
+ b) Abort replay.
+
+ 4) Deleting mailboxes or deleting/expunging messages that no longer
+ exist.
+
+ This is actually is not an error and should be ignored by the
+ client.
+
+ 5) Performing operations on messages that no longer exist.
+
+ a) Skip operation.
+ b) Abort replay.
+
+ In the case of changing flags on an expunged message, the client
+ should silently ignore the error.
+
+ Note 1: Several synchronization operations map to multiple IMAP
+ commands (for example, "move" described in 4.2.2). The client must
+ guarantee atomicity of each such multistep operation. For example,
+ when performing a "move" between two mailboxes on the same server, if
+ the server is unable to copy messages, the client MUST NOT attempt to
+ set the \Deleted flag on the messages being copied, let alone expunge
+ them. However, the client MAY consider that move operation to have
+ succeeded even if the server was unable to set the \Deleted flag on
+ copied messages.
+
+ Note 2: Many synchronization operations have data dependencies. A
+ failed operation must cause all dependent operations to fail as well.
+ The client should check this and MUST NOT try to perform all
+ dependent operations blindly (unless the user corrected the original
+ problem). For example, a message may be scheduled to be appended to
+ a mailbox on the server and later on the appended message may be
+ copied to another mailbox. If the APPEND operation fails, the client
+ must not attempt to COPY the failed message later on. (See also
+ Section 5, Situation 3).
+
+
+
+
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+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+5.2. Quality of Implementation Issues
+
+ Below, some quality of implementation issues are listed for
+ disconnected clients. They will help to write a disconnected client
+ that works correctly, performs synchronization as quickly as possible
+ (and thus can make the user happier as well as save her some money),
+ and minimizes the server load:
+
+ 1) Don't lose information.
+
+ No matter how smart your client is in other areas, if it loses
+ information, users will get very upset.
+
+ 2) Don't do work unless explicitly asked. Be flexible. Ask all
+ questions BEFORE starting synchronization, if possible.
+
+ 3) Minimize traffic.
+
+ The client MUST NOT issue a command if the client already received
+ the required information from the server.
+
+ The client MUST make use of UIDPLUS extension if it is supported
+ by the server.
+
+ See also optimization 1 in Section 5.3.
+
+ 4) Minimize the number of round-trips.
+
+ Round-trips kill performance, especially on links with high
+ latency. Sections 4.2.2.5 and 5.2 give some advice on how to
+ minimize the number of round-trips.
+
+ See also optimization 1 in Section 5.3.
+
+5.3. Optimizations
+
+ Some useful optimizations are described in this section. A
+ disconnected client that supports the recommendations listed below
+ will give the user a more pleasant experience.
+
+ 1) The initial OK or PREAUTH responses may contain the CAPABILITY
+ response code as described in Section 7.1 of [IMAP4]. This
+ response code gives the same information as returned by the
+ CAPABILITY command*. A disconnected client that pays attention to
+ this response code can avoid sending CAPABILITY command and will
+ save a round-trip.
+
+
+
+
+
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+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ * Note: Some servers report in the CAPABILITY response code
+ extensions that are only relevant in unauthenticated state or in
+ all states. Such servers usually send another CAPABILITY
+ response code upon successful authentication using LOGIN or
+ AUTHENTICATE command (that negotiates no security layer; see
+ Section 6.2.2 of [IMAP4]). The CAPABILITY response code sent
+ upon successful LOGIN/AUTHENTICATE might be different from the
+ CAPABILITY response code in the initial OK response, as
+ extensions only relevant for unauthenticated state will not be
+ advertised, and some additional extensions available only in
+ authenticated and/or selected state will be.
+
+ Example 9:
+
+ S: * OK [CAPABILITY IMAP4REV1 LOGIN-REFERRALS STARTTLS
+ AUTH=DIGEST-MD5 AUTH=SRP] imap.example.com ready
+ C: 2 authenticate DIGEST-MD5
+ S: 2 OK [CAPABILITY IMAP4REV1 IDLE NAMESPACE MAILBOX-REFERRALS SCAN
+ SORT THREAD=REFERENCES THREAD=ORDEREDSUBJECT MULTIAPPEND]
+ User authenticated (no layer)
+
+ 2) An advanced disconnected client may choose to optimize its replay
+ log. For example, there might be some operations that are
+ redundant (the list is not complete):
+
+ a) an EXPUNGE followed by another EXPUNGE or CLOSE;
+ b) changing flags (other than the \Deleted flag) on a message that
+ gets immediately expunged;
+ c) opening and closing the same mailbox.
+
+ When optimizing, be careful about data dependencies between commands.
+ For example, if the client is wishing to optimize (see case b, above)
+
+ tag1 UID STORE <uid1> +FLAGS (\Deleted)
+ ...
+ tag2 UID STORE <uid1> +FLAGS (\Flagged)
+ ...
+ tag3 UID COPY <uid1> "Backup"
+ ...
+ tag4 UID EXPUNGE <uid1>
+
+ it can't remove the second UID STORE command because the message is
+ being copied before it gets expunged.
+
+ In general, it might be a good idea to keep mailboxes open during
+ synchronization (see case c above), if possible. This can be more
+ easily achieved in conjunction with optimization 3 described below.
+
+
+
+
+Melnikov Informational [Page 29]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ 3) Perform some synchronization steps in parallel, if possible.
+
+ Several synchronization steps don't depend on each other and thus
+ can be performed in parallel. Because the server machine is
+ usually more powerful than the client machine and can perform some
+ operations in parallel, this may speed up the total time of
+ synchronization.
+
+ In order to achieve such parallelization, the client will have to
+ open more than one connection to the same server. Client writers
+ should not forget about non-trivial cost associated with
+ establishing a TCP connection and performing an authentication.
+ The disconnected client MUST NOT use one connection per mailbox.
+ In most cases, it is sufficient to have two connections. The
+ disconnected client SHOULD avoid selecting the same mailbox in
+ more than one connection; see Section 3.1.1 of [RFC2683] for more
+ details.
+
+ Any mailbox synchronization MUST start with checking the
+ UIDVALIDITY as described in Section 4.1 of this document. The
+ client MAY use STATUS command to check UID Validity of a non-
+ selected mailbox. This is preferable to opening many connections
+ to the same server to perform synchronization of multiple
+ mailboxes simultaneously. As described in Section 5.3.10 of
+ [IMAP4], this SHOULD NOT be used on the selected mailbox.
+
+6. IMAP Extensions That May Help
+
+ The following extensions can save traffic and/or the number of
+ round-trips:
+
+ 1) The use of [UIDPLUS] is discussed in Sections 4.1, 4.2.1, 4.2.2.1
+ and 4.2.4.
+
+ 2) The use of the MULTIAPPEND and LITERAL+ extensions for uploading
+ messages is discussed in Section 4.2.2.5.
+
+ 3) Use the CONDSTORE extension (see Section 6.1) for quick flag
+ resynchronization.
+
+6.1. CONDSTORE Extension
+
+ An advanced disconnected mail client should use the [CONDSTORE]
+ extension when it is supported by the server. The client must cache
+ the value from HIGHESTMODSEQ OK response code received on mailbox
+ opening and update it whenever the server sends MODSEQ FETCH data
+ items.
+
+
+
+
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+
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+
+
+ If the client receives NOMODSEQ OK untagged response instead of
+ HIGHESTMODSEQ, it MUST remove the last known HIGHESTMODSEQ value from
+ its cache and follow the more general instructions in Section 3.
+
+ When the client opens the mailbox for synchronization, it first
+ compares UIDVALIDITY as described in step d-1 in Section 3. If the
+ cached UIDVALIDITY value matches the one returned by the server, the
+ client MUST compare the cached value of HIGHESTMODSEQ with the one
+ returned by the server. If the cached HIGHESTMODSEQ value also
+ matches the one returned by the server, then the client MUST NOT
+ fetch flags for cached messages, as they hasn't changed. If the
+ value on the server is higher than the cached one, the client MAY use
+ "SEARCH MODSEQ <cached-value>" to find all messages with flags
+ changed since the last time the client was online and had the mailbox
+ opened. Alternatively, the client MAY use "FETCH 1:* (FLAGS)
+ (CHANGEDSINCE <cached-value>)". The latter operation combines
+ searching for changed messages and fetching new information.
+
+ In all cases, the client still needs to fetch information about new
+ messages (if requested by the user) as well as discover which
+ messages have been expunged.
+
+ Step d ("Server-to-client synchronization") in Section 4 in the
+ presence of the CONDSTORE extension is amended as follows:
+
+ d) "Server-to-client synchronization" - For each mailbox that
+ requires synchronization, do the following:
+
+ 1a) Check the mailbox UIDVALIDITY (see section 4.1 for more
+ details) with SELECT/EXAMINE/STATUS.
+
+ If the UIDVALIDITY value returned by the server differs, the
+ client MUST
+
+ * empty the local cache of that mailbox;
+ * "forget" the cached HIGHESTMODSEQ value for the mailbox;
+ * remove any pending "actions" that refer to UIDs in that
+ mailbox (note that this doesn't affect actions performed on
+ client-generated fake UIDs; see Section 5); and
+ * skip steps 1b and 2-II;
+
+ 1b) Check the mailbox HIGHESTMODSEQ. If the cached value is the
+ same as the one returned by the server, skip fetching message
+ flags on step 2-II, i.e., the client only has to find out
+ which messages got expunged.
+
+
+
+
+
+
+Melnikov Informational [Page 31]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ 2) Fetch the current "descriptors".
+
+ I) Discover new messages.
+
+ II) Discover changes to old messages and flags for new messages
+ using
+ "FETCH 1:* (FLAGS) (CHANGEDSINCE <cached-value>)" or
+ "SEARCH MODSEQ <cached-value>".
+
+ Discover expunged messages; for example, using
+ "UID SEARCH 1:<lastseenuid>". (All messages not returned
+ in this command are expunged.)
+
+ 3) Fetch the bodies of any "interesting" messages that the client
+ doesn't already have.
+
+ Example 10:
+
+ The UIDVALIDITY value is the same, but the HIGHESTMODSEQ value
+ has changed on the server while the client was offline.
+
+ C: A142 SELECT INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 201] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: * OK [HIGHESTMODSEQ 20010715194045007]
+ S: A142 OK [READ-WRITE] SELECT completed
+
+ After that, either:
+
+ C: A143 UID FETCH 1:* (FLAGS) (CHANGEDSINCE 20010715194032001)
+ S: * 2 FETCH (UID 6 MODSEQ (20010715205008000) FLAGS (\Deleted))
+ S: * 5 FETCH (UID 9 MODSEQ (20010715195517000) FLAGS ($NoJunk
+ $AutoJunk $MDNSent))
+ ...
+ S: A143 OK FETCH completed
+
+ or:
+
+
+
+
+
+
+
+
+
+Melnikov Informational [Page 32]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+ C: A143 UID SEARCH MODSEQ 20010715194032001 UID 1:20
+ S: * SEARCH 6 9 11 12 18 19 20 23 (MODSEQ 20010917162500)
+ S: A143 OK Search complete
+ C: A144 UID SEARCH 1:20
+ S: * SEARCH 6 9 ...
+ S: A144 OK FETCH completed
+
+7. Security Considerations
+
+ It is believed that this document does not raise any new security
+ concerns that are not already present in the base [IMAP4] protocol,
+ and these issues are discussed in [IMAP4]. Additional security
+ considerations may be found in different extensions mentioned in this
+ document; in particular, in [UIDPLUS], [LITERAL+], [CONDSTORE],
+ [MULTIAPPEND], and [UNSELECT].
+
+ Implementers are also reminded about the importance of thorough
+ testing.
+
+8. References
+
+8.1. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
+ VERSION 4rev1", RFC 3501, March 2003.
+
+ [UIDPLUS] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ UIDPLUS extension", RFC 4315, December 2005.
+
+ [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC
+ 2088, January 1997.
+
+ [CONDSTORE] Melnikov, A. and S. Hole, "IMAP Extension for
+ Conditional STORE Operation or Quick Flag Changes
+ Resynchronization", RFC 4551, June 2006.
+
+ [MULTIAPPEND] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ MULTIAPPEND Extension", RFC 3502, March 2003.
+
+ [UNSELECT] Melnikov, A., "Internet Message Access Protocol (IMAP)
+ UNSELECT command", RFC 3691, February 2004.
+
+ [RFC2683] Leiba, B., "IMAP4 Implementation Recommendations", RFC
+ 2683, September 1999.
+
+
+
+
+Melnikov Informational [Page 33]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+8.2. Informative References
+
+ [ACL] Melnikov, A., "IMAP4 Access Control List (ACL)
+ Extension", RFC 4314, December 2005.
+
+ [IMAP-MODEL] Crispin, M., "Distributed Electronic Mail Models in
+ IMAP4", RFC 1733, December 1994.
+
+9. Acknowledgements
+
+ This document is based on version 01 of the text written by Rob
+ Austein in November 1994.
+
+ The editor appreciates comments posted by Mark Crispin to the IMAP
+ mailing list and the comments/corrections/ideas received from Grant
+ Baillie, Cyrus Daboo, John G. Myers, Chris Newman, and Timo Sirainen.
+
+ The editor would also like to thank the developers of Netscape
+ Messenger and Mozilla mail clients for providing examples of
+ disconnected mail clients that served as a base for many
+ recommendations in this document.
+
+Editor's Address
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex
+ TW12 2BX
+ United Kingdom
+
+ Phone: +44 77 53759732
+ EMail: alexey.melnikov@isode.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Informational [Page 34]
+
+RFC 4549 Synch Ops for Disconnected IMAP4 Clients June 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov Informational [Page 35]
+
diff --git a/imap/docs/rfc/rfc4551.txt b/imap/docs/rfc/rfc4551.txt
new file mode 100644
index 00000000..894b5109
--- /dev/null
+++ b/imap/docs/rfc/rfc4551.txt
@@ -0,0 +1,1403 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 4551 Isode Ltd.
+Updates: 3501 S. Hole
+Category: Standards Track ACI WorldWide/MessagingDirect
+ June 2006
+
+
+ IMAP Extension for Conditional STORE Operation
+ or Quick Flag Changes Resynchronization
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ Often, multiple IMAP (RFC 3501) clients need to coordinate changes to
+ a common IMAP mailbox. Examples include different clients working on
+ behalf of the same user, and multiple users accessing shared
+ mailboxes. These clients need a mechanism to synchronize state
+ changes for messages within the mailbox. They must be able to
+ guarantee that only one client can change message state (e.g.,
+ message flags) at any time. An example of such an application is use
+ of an IMAP mailbox as a message queue with multiple dequeueing
+ clients.
+
+ The Conditional Store facility provides a protected update mechanism
+ for message state information that can detect and resolve conflicts
+ between multiple writing mail clients.
+
+ The Conditional Store facility also allows a client to quickly
+ resynchronize mailbox flag changes.
+
+ This document defines an extension to IMAP (RFC 3501).
+
+
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 1]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+Table of Contents
+
+ 1. Introduction and Overview ................................. 3
+ 2. Conventions Used in This Document ......................... 5
+ 3. IMAP Protocol Changes ..................................... 6
+ 3.1. New OK untagged responses for SELECT and EXAMINE ......... 6
+ 3.1.1. HIGHESTMODSEQ response code ............................ 6
+ 3.1.2. NOMODSEQ response code ................................. 7
+ 3.2. STORE and UID STORE Commands ............................. 7
+ 3.3 FETCH and UID FETCH Commands ..............................13
+ 3.3.1. CHANGEDSINCE FETCH modifier ............................13
+ 3.3.2. MODSEQ message data item in FETCH Command ..............14
+ 3.4. MODSEQ search criterion in SEARCH ........................16
+ 3.5. Modified SEARCH untagged response ........................17
+ 3.6. HIGHESTMODSEQ status data items ..........................17
+ 3.7. CONDSTORE parameter to SELECT and EXAMINE ................18
+ 3.8. Additional quality of implementation issues ..............18
+ 4. Formal Syntax .............................................19
+ 5. Server implementation considerations ......................21
+ 6. Security Considerations ...................................22
+ 7. IANA Considerations .......................................22
+ 8. References ................................................23
+ 8.1. Normative References .....................................23
+ 8.2. Informative References ...................................23
+ 9. Acknowledgements ..........................................23
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 2]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+1. Introduction and Overview
+
+ The Conditional STORE extension is present in any IMAP4
+ implementation that returns "CONDSTORE" as one of the supported
+ capabilities in the CAPABILITY command response.
+
+ An IMAP server that supports this extension MUST associate a positive
+ unsigned 64-bit value called a modification sequence (mod-sequence)
+ with every IMAP message. This is an opaque value updated by the
+ server whenever a metadata item is modified. The server MUST
+ guarantee that each STORE command performed on the same mailbox
+ (including simultaneous stores to different metadata items from
+ different connections) will get a different mod-sequence value.
+ Also, for any two successful STORE operations performed in the same
+ session on the same mailbox, the mod-sequence of the second completed
+ operation MUST be greater than the mod-sequence of the first
+ completed. Note that the latter rule disallows the use of the system
+ clock as a mod-sequence, because if system time changes (e.g., an NTP
+ [NTP] client adjusting the time), the next generated value might be
+ less than the previous one.
+
+ Mod-sequences allow a client that supports the CONDSTORE extension to
+ determine if a message metadata has changed since some known moment.
+ Whenever the state of a flag changes (i.e., the flag is added where
+ previously it wasn't set, or the flag is removed and before it was
+ set) the value of the modification sequence for the message MUST be
+ updated. Adding the flag when it is already present or removing when
+ it is not present SHOULD NOT change the mod-sequence.
+
+ When a message is appended to a mailbox (via the IMAP APPEND command,
+ COPY to the mailbox, or using an external mechanism) the server
+ generates a new modification sequence that is higher than the highest
+ modification sequence of all messages in the mailbox and assigns it
+ to the appended message.
+
+ The server MAY store separate (per-message) modification sequence
+ values for different metadata items. If the server does so, per-
+ message mod-sequence is the highest mod-sequence of all metadata
+ items for the specified message.
+
+ The server that supports this extension is not required to be able to
+ store mod-sequences for every available mailbox. Section 3.1.2
+ describes how the server may act if a particular mailbox doesn't
+ support the persistent storage of mod-sequences.
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 3]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ This extension makes the following changes to the IMAP4 protocol:
+
+ a) adds UNCHANGEDSINCE STORE modifier.
+
+ b) adds the MODIFIED response code which should be used with an OK
+ response to the STORE command. (It can also be used in a NO
+ response.)
+
+ c) adds a new MODSEQ message data item for use with the FETCH
+ command.
+
+ d) adds CHANGEDSINCE FETCH modifier.
+
+ e) adds a new MODSEQ search criterion.
+
+ f) extends the syntax of untagged SEARCH responses to include
+ mod-sequence.
+
+ g) adds new OK untagged responses for the SELECT and EXAMINE
+ commands.
+
+ h) defines an additional parameter to SELECT/EXAMINE commands.
+
+ i) adds the HIGHESTMODSEQ status data item to the STATUS command.
+
+ A client supporting CONDSTORE extension indicates its willingness to
+ receive mod-sequence updates in all untagged FETCH responses by
+ issuing:
+
+ - a SELECT or EXAMINE command with the CONDSTORE parameter,
+ - a STATUS (HIGHESTMODSEQ) command,
+ - a FETCH or SEARCH command that includes the MODSEQ message data
+ item,
+ - a FETCH command with the CHANGEDSINCE modifier, or
+ - a STORE command with the UNCHANGEDSINCE modifier.
+
+ The server MUST include mod-sequence data in all subsequent untagged
+ FETCH responses (until the connection is closed), whether they were
+ caused by a regular STORE, a STORE with UNCHANGEDSINCE modifier, or
+ an external agent.
+
+ This document uses the term "CONDSTORE-aware client" to refer to a
+ client that announces its willingness to receive mod-sequence updates
+ as described above. The term "CONDSTORE enabling command" will refer
+ any of the commands listed above. A future extension to this
+ document may extend the list of CONDSTORE enabling commands. A first
+ CONDSTORE enabling command executed in the session MUST cause the
+
+
+
+
+Melnikov & Hole Standards Track [Page 4]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ server to return HIGHESTMODSEQ (Section 3.1.1) unless the server has
+ sent NOMODSEQ (Section 3.1.2) response code when the currently
+ selected mailbox was selected.
+
+ The rest of this document describes the protocol changes more
+ rigorously.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+ In examples, lines beginning with "S:" are sent by the IMAP server,
+ and lines beginning with "C:" are sent by the client. Line breaks
+ may appear in example commands solely for editorial clarity; when
+ present in the actual message, they are represented by "CRLF".
+
+ Formal syntax is defined using ABNF [ABNF].
+
+ The term "metadata" or "metadata item" is used throughout this
+ document. It refers to any system or user-defined keyword. Future
+ documents may extend "metadata" to include other dynamic message
+ data.
+
+ Some IMAP mailboxes are private, accessible only to the owning user.
+ Other mailboxes are not, either because the owner has set an Access
+ Control List [ACL] that permits access by other users, or because it
+ is a shared mailbox. Let's call a metadata item "shared" for the
+ mailbox if any changes to the metadata items are persistent and
+ visible to all other users accessing the mailbox. Otherwise, the
+ metadata item is called "private". Note that private metadata items
+ are still visible to all sessions accessing the mailbox as the same
+ user. Also note that different mailboxes may have different metadata
+ items as shared.
+
+ See Section 1 for the definition of a "CONDSTORE-aware client" and a
+ "CONDSTORE enabling command".
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 5]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+3. IMAP Protocol Changes
+
+3.1. New OK Untagged Responses for SELECT and EXAMINE
+
+ This document adds two new response codes, HIGHESTMODSEQ and
+ NOMODSEQ. One of those response codes MUST be returned in the OK
+ untagged response for a successful SELECT/EXAMINE command.
+
+ When opening a mailbox, the server must check if the mailbox supports
+ the persistent storage of mod-sequences. If the mailbox supports the
+ persistent storage of mod-sequences and the mailbox open operation
+ succeeds, the server MUST send the OK untagged response including
+ HIGHESTMODSEQ response code. If the persistent storage for the
+ mailbox is not supported, the server MUST send the OK untagged
+ response including NOMODSEQ response code instead.
+
+3.1.1. HIGHESTMODSEQ Response Code
+
+ This document adds a new response code that is returned in the OK
+ untagged response for the SELECT and EXAMINE commands. A server
+ supporting the persistent storage of mod-sequences for the mailbox
+ MUST send the OK untagged response including HIGHESTMODSEQ response
+ code with every successful SELECT or EXAMINE command:
+
+ OK [HIGHESTMODSEQ <mod-sequence-value>]
+
+ where <mod-sequence-value> is the highest mod-sequence value of
+ all messages in the mailbox. When the server changes UIDVALIDITY
+ for a mailbox, it doesn't have to keep the same HIGHESTMODSEQ for
+ the mailbox.
+
+ A disconnected client can use the value of HIGHESTMODSEQ to check if
+ it has to refetch metadata from the server. If the UIDVALIDITY value
+ has changed for the selected mailbox, the client MUST delete the
+ cached value of HIGHESTMODSEQ. If UIDVALIDITY for the mailbox is the
+ same, and if the HIGHESTMODSEQ value stored in the client's cache is
+ less than the value returned by the server, then some metadata items
+ on the server have changed since the last synchronization, and the
+ client needs to update its cache. The client MAY use SEARCH MODSEQ
+ (Section 3.4) to find out exactly which metadata items have changed.
+ Alternatively, the client MAY issue FETCH with the CHANGEDSINCE
+ modifier (Section 3.3.1) in order to fetch data for all messages that
+ have metadata items changed since some known modification sequence.
+
+ Example 1:
+
+ C: A142 SELECT INBOX
+ S: * 172 EXISTS
+
+
+
+Melnikov & Hole Standards Track [Page 6]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: * OK [HIGHESTMODSEQ 715194045007]
+ S: A142 OK [READ-WRITE] SELECT completed
+
+3.1.2. NOMODSEQ Response Code
+
+ A server that doesn't support the persistent storage of mod-sequences
+ for the mailbox MUST send the OK untagged response including NOMODSEQ
+ response code with every successful SELECT or EXAMINE command. A
+ server that returned NOMODSEQ response code for a mailbox, which
+ subsequently receives one of the following commands while the mailbox
+ is selected:
+
+ - a FETCH command with the CHANGEDSINCE modifier,
+ - a FETCH or SEARCH command that includes the MODSEQ message data
+ item, or
+ - a STORE command with the UNCHANGEDSINCE modifier
+
+ MUST reject any such command with the tagged BAD response.
+
+ Example 2:
+
+ C: A142 SELECT INBOX
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: * OK [NOMODSEQ] Sorry, this mailbox format doesn't support
+ modsequences
+ S: A142 OK [READ-WRITE] SELECT completed
+
+3.2. STORE and UID STORE Commands
+
+ This document defines the following STORE modifier (see Section 2.5
+ of [IMAPABNF]):
+
+ UNCHANGEDSINCE <mod-sequence>
+
+ For each message specified in the message set, the server performs
+ the following. If the mod-sequence of any metadata item of the
+
+
+
+Melnikov & Hole Standards Track [Page 7]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ message is equal or less than the specified UNCHANGEDSINCE value,
+ then the requested operation (as described by the message data
+ item) is performed. If the operation is successful, the server
+ MUST update the mod-sequence attribute of the message. An
+ untagged FETCH response MUST be sent, even if the .SILENT suffix
+ is specified, and the response MUST include the MODSEQ message
+ data item. This is required to update the client's cache with the
+ correct mod-sequence values. See Section 3.3.2 for more details.
+
+ However, if the mod-sequence of any metadata item of the message
+ is greater than the specified UNCHANGEDSINCE value, then the
+ requested operation MUST NOT be performed. In this case, the
+ mod-sequence attribute of the message is not updated, and the
+ message number (or unique identifier in the case of the UID STORE
+ command) is added to the list of messages that failed the
+ UNCHANGESINCE test.
+
+ When the server finished performing the operation on all the
+ messages in the message set, it checks for a non-empty list of
+ messages that failed the UNCHANGESINCE test. If this list is
+ non-empty, the server MUST return in the tagged response a
+ MODIFIED response code. The MODIFIED response code includes the
+ message set (for STORE) or set of UIDs (for UID STORE) of all
+ messages that failed the UNCHANGESINCE test.
+
+ Example 3:
+
+ All messages pass the UNCHANGESINCE test.
+
+ C: a103 UID STORE 6,4,8 (UNCHANGEDSINCE 12121230045)
+ +FLAGS.SILENT (\Deleted)
+ S: * 1 FETCH (UID 4 MODSEQ (12121231000))
+ S: * 2 FETCH (UID 6 MODSEQ (12121230852))
+ S: * 4 FETCH (UID 8 MODSEQ (12121130956))
+ S: a103 OK Conditional Store completed
+
+ Example 4:
+
+ C: a104 STORE * (UNCHANGEDSINCE 12121230045) +FLAGS.SILENT
+ (\Deleted $Processed)
+ S: * 50 FETCH (MODSEQ (12111230047))
+ S: a104 OK Store (conditional) completed
+
+ Example 5:
+
+ C: c101 STORE 1 (UNCHANGEDSINCE 12121230045) -FLAGS.SILENT
+ (\Deleted)
+ S: * OK [HIGHESTMODSEQ 12111230047]
+
+
+
+Melnikov & Hole Standards Track [Page 8]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ S: * 50 FETCH (MODSEQ (12111230048))
+ S: c101 OK Store (conditional) completed
+
+ HIGHESTMODSEQ response code was sent by the server presumably
+ because this was the first CONDSTORE enabling command.
+
+ Example 6:
+
+ In spite of the failure of the conditional STORE operation for
+ message 7, the server continues to process the conditional STORE
+ in order to find all messages that fail the test.
+
+ C: d105 STORE 7,5,9 (UNCHANGEDSINCE 320162338)
+ +FLAGS.SILENT (\Deleted)
+ S: * 5 FETCH (MODSEQ (320162350))
+ S: d105 OK [MODIFIED 7,9] Conditional STORE failed
+
+ Example 7:
+
+ Same as above, but the server follows the SHOULD recommendation in
+ Section 6.4.6 of [IMAP4].
+
+ C: d105 STORE 7,5,9 (UNCHANGEDSINCE 320162338)
+ +FLAGS.SILENT (\Deleted)
+ S: * 7 FETCH (MODSEQ (320162342) FLAGS (\Seen \Deleted))
+ S: * 5 FETCH (MODSEQ (320162350))
+ S: * 9 FETCH (MODSEQ (320162349) FLAGS (\Answered))
+ S: d105 OK [MODIFIED 7,9] Conditional STORE failed
+
+ Use of UNCHANGEDSINCE with a modification sequence of 0 always
+ fails if the metadata item exists. A system flag MUST always be
+ considered existent, whether it was set or not.
+
+ Example 8:
+
+ C: a102 STORE 12 (UNCHANGEDSINCE 0)
+ +FLAGS.SILENT ($MDNSent)
+ S: a102 OK [MODIFIED 12] Conditional STORE failed
+
+ The client has tested the presence of the $MDNSent user-defined
+ keyword.
+
+ Note: A client trying to make an atomic change to the state of a
+ particular metadata item (or a set of metadata items) should be
+ prepared to deal with the case when the server returns the MODIFIED
+ response code if the state of the metadata item being watched hasn't
+ changed (but the state of some other metadata item has). This is
+ necessary, because some servers don't store separate mod-sequences
+
+
+
+Melnikov & Hole Standards Track [Page 9]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ for different metadata items. However, a server implementation
+ SHOULD avoid generating spurious MODIFIED responses for +FLAGS/-FLAGS
+ STORE operations, even when the server stores a single mod-sequence
+ per message. Section 5 describes how this can be achieved.
+
+ Unless the server has included an unsolicited FETCH to update
+ client's knowledge about messages that have failed the UNCHANGEDSINCE
+ test, upon receipt of the MODIFIED response code, the client SHOULD
+ try to figure out if the required metadata items have indeed changed
+ by issuing FETCH or NOOP command. It is RECOMMENDED that the server
+ avoids the need for the client to do that by sending an unsolicited
+ FETCH response (Examples 9 and 10).
+
+ If the required metadata items haven't changed, the client SHOULD
+ retry the command with the new mod-sequence. The client SHOULD allow
+ for a configurable but reasonable number of retries (at least 2).
+
+ Example 9:
+
+ In the example below, the server returns the MODIFIED response
+ code without sending information describing why the STORE
+ UNCHANGEDSINCE operation has failed.
+
+ C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+ +FLAGS.SILENT ($Processed)
+ S: * 100 FETCH (MODSEQ (303181230852))
+ S: * 102 FETCH (MODSEQ (303181230852))
+ ...
+ S: * 150 FETCH (MODSEQ (303181230852))
+ S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+ The flag $Processed was set on the message 101...
+
+ C: a107 NOOP
+ S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed))
+ S: a107 OK
+
+ Or the flag hasn't changed, but another has (note that this server
+ behaviour is discouraged. Server implementers should also see
+ Section 5)...
+
+ C: b107 NOOP
+ S: * 101 FETCH (MODSEQ (303011130956) FLAGS (\Deleted \Answered))
+ S: b107 OK
+
+ ...and the client retries the operation for the message 101 with
+ the updated UNCHANGEDSINCE value
+
+
+
+
+Melnikov & Hole Standards Track [Page 10]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ C: b108 STORE 101 (UNCHANGEDSINCE 303011130956)
+ +FLAGS.SILENT ($Processed)
+ S: * 101 FETCH (MODSEQ (303181230852))
+ S: b108 OK Conditional Store completed
+
+ Example 10:
+
+ Same as above, but the server avoids the need for the client to
+ poll for changes.
+
+ The flag $Processed was set on the message 101 by another
+ client...
+
+ C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+ +FLAGS.SILENT ($Processed)
+ S: * 100 FETCH (MODSEQ (303181230852))
+ S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed))
+ S: * 102 FETCH (MODSEQ (303181230852))
+ ...
+ S: * 150 FETCH (MODSEQ (303181230852))
+ S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+ Or the flag hasn't changed, but another has (note that this server
+ behaviour is discouraged. Server implementers should also see
+ Section 5)...
+
+ C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+ +FLAGS.SILENT ($Processed)
+ S: * 100 FETCH (MODSEQ (303181230852))
+ S: * 101 FETCH (MODSEQ (303011130956) FLAGS (\Deleted \Answered))
+ S: * 102 FETCH (MODSEQ (303181230852))
+ ...
+ S: * 150 FETCH (MODSEQ (303181230852))
+ S: a106 OK [MODIFIED 101] Conditional STORE failed
+
+ ...and the client retries the operation for the message 101 with
+ the updated UNCHANGEDSINCE value
+
+ C: b108 STORE 101 (UNCHANGEDSINCE 303011130956)
+ +FLAGS.SILENT ($Processed)
+ S: * 101 FETCH (MODSEQ (303181230852))
+ S: b108 OK Conditional Store completed
+
+ Or the flag hasn't changed, but another has (nice server
+ behaviour. Server implementers should also see Section 5)...
+
+ C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+ +FLAGS.SILENT ($Processed)
+
+
+
+Melnikov & Hole Standards Track [Page 11]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ S: * 100 FETCH (MODSEQ (303181230852))
+ S: * 101 FETCH (MODSEQ (303011130956) FLAGS ($Processed \Deleted
+ \Answered))
+ S: * 102 FETCH (MODSEQ (303181230852))
+ ...
+ S: * 150 FETCH (MODSEQ (303181230852))
+ S: a106 OK Conditional STORE completed
+
+ Example 11:
+
+ The following example is based on the example from the Section
+ 4.2.3 of [RFC-2180] and demonstrates that the MODIFIED response
+ code may be also returned in the tagged NO response.
+
+ Client tries to conditionally STORE flags on a mixture of expunged
+ and non-expunged messages; one message fails the UNCHANGEDSINCE
+ test.
+
+ C: B001 STORE 1:7 (UNCHANGEDSINCE 320172338) +FLAGS (\SEEN)
+ S: * 1 FETCH (MODSEQ (320172342) FLAGS (\SEEN))
+ S: * 3 FETCH (MODSEQ (320172342) FLAGS (\SEEN))
+ S: B001 NO [MODIFIED 2] Some of the messages no longer exist.
+
+ C: B002 NOOP
+ S: * 4 EXPUNGE
+ S: * 4 EXPUNGE
+ S: * 4 EXPUNGE
+ S: * 4 EXPUNGE
+ S: * 2 FETCH (MODSEQ (320172340) FLAGS (\Deleted \Answered))
+ S: B002 OK NOOP Completed.
+
+ By receiving FETCH responses for messages 1 and 3, and EXPUNGE
+ responses that indicate that messages 4 through 7 have been
+ expunged, the client retries the operation only for the message 2.
+ The updated UNCHANGEDSINCE value is used.
+
+ C: b003 STORE 2 (UNCHANGEDSINCE 320172340) +FLAGS (\Seen)
+ S: * 2 FETCH (MODSEQ (320180050))
+ S: b003 OK Conditional Store completed
+
+ Note: If a message is specified multiple times in the message set,
+ and the server doesn't internally eliminate duplicates from the
+ message set, it MUST NOT fail the conditional STORE operation for the
+ second (or subsequent) occurrence of the message if the operation
+ completed successfully for the first occurrence. For example, if the
+ client specifies:
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 12]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ e105 STORE 7,3:9 (UNCHANGEDSINCE 12121230045)
+ +FLAGS.SILENT (\Deleted)
+
+ the server must not fail the operation for message 7 as part of
+ processing "3:9" if it succeeded when message 7 was processed the
+ first time.
+
+ Once the client specified the UNCHANGEDSINCE modifier in a STORE
+ command, the server MUST include the MODSEQ fetch response data items
+ in all subsequent unsolicited FETCH responses.
+
+ This document also changes the behaviour of the server when it has
+ performed a STORE or UID STORE command and the UNCHANGEDSINCE
+ modifier is not specified. If the operation is successful for a
+ message, the server MUST update the mod-sequence attribute of the
+ message. The server is REQUIRED to include the mod-sequence value
+ whenever it decides to send the unsolicited FETCH response to all
+ CONDSTORE-aware clients that have opened the mailbox containing the
+ message.
+
+ Server implementers should also see Section 3.8 for additional
+ quality of implementation issues related to the STORE command.
+
+3.3. FETCH and UID FETCH Commands
+
+3.3.1. CHANGEDSINCE FETCH Modifier
+
+ This document defines the following FETCH modifier (see Section 2.4
+ of [IMAPABNF]):
+
+ CHANGEDSINCE <mod-sequence>
+
+ CHANGEDSINCE FETCH modifier allows to create a further subset of
+ the list of messages described by sequence set. The information
+ described by message data items is only returned for messages that
+ have mod-sequence bigger than <mod-sequence>.
+
+ When CHANGEDSINCE FETCH modifier is specified, it implicitly adds
+ MODSEQ FETCH message data item (Section 3.3.2).
+
+ Example 12:
+
+ C: s100 UID FETCH 1:* (FLAGS) (CHANGEDSINCE 12345)
+ S: * 1 FETCH (UID 4 MODSEQ (65402) FLAGS (\Seen))
+ S: * 2 FETCH (UID 6 MODSEQ (75403) FLAGS (\Deleted))
+ S: * 4 FETCH (UID 8 MODSEQ (29738) FLAGS ($NoJunk $AutoJunk
+ $MDNSent))
+ S: s100 OK FETCH completed
+
+
+
+Melnikov & Hole Standards Track [Page 13]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+3.3.2. MODSEQ Message Data Item in FETCH Command
+
+ This extension adds a MODSEQ message data item to the FETCH command.
+ The MODSEQ message data item allows clients to retrieve mod-sequence
+ values for a range of messages in the currently selected mailbox.
+
+ Once the client specified the MODSEQ message data item in a FETCH
+ request, the server MUST include the MODSEQ fetch response data items
+ in all subsequent unsolicited FETCH responses.
+
+ Syntax: MODSEQ
+
+ The MODSEQ message data item causes the server to return MODSEQ
+ fetch response data items.
+
+ Syntax: MODSEQ ( <permsg-modsequence> )
+
+ MODSEQ response data items contain per-message mod-sequences.
+
+ The MODSEQ response data item is returned if the client issued
+ FETCH with MODSEQ message data item. It also allows the server to
+ notify the client about mod-sequence changes caused by conditional
+ STOREs (Section 3.2) and/or changes caused by external sources.
+
+ Example 13:
+
+ C: a FETCH 1:3 (MODSEQ)
+ S: * 1 FETCH (MODSEQ (624140003))
+ S: * 2 FETCH (MODSEQ (624140007))
+ S: * 3 FETCH (MODSEQ (624140005))
+ S: a OK Fetch complete
+
+ In this example, the client requests per-message mod-sequences for
+ a set of messages.
+
+ When a flag for a message is modified in a different session, the
+ server sends an unsolicited FETCH response containing the mod-
+ sequence for the message.
+
+ Example 14:
+
+ (Session 1, authenticated as a user "alex"). The user adds a
+ shared flag \Deleted:
+
+ C: A142 SELECT INBOX
+ ...
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Answered \Deleted \Seen \*)] Limited
+
+
+
+Melnikov & Hole Standards Track [Page 14]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ ...
+
+ C: A160 STORE 7 +FLAGS.SILENT (\Deleted)
+ S: * 7 FETCH (MODSEQ (2121231000))
+ S: A160 OK Store completed
+
+ (Session 2, also authenticated as the user "alex"). Any changes
+ to flags are always reported to all sessions authenticated as the
+ same user as in the session 1.
+
+ C: C180 NOOP
+ S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (12121231000))
+ S: C180 OK Noop completed
+
+ (Session 3, authenticated as a user "andrew"). As \Deleted is a
+ shared flag, changes in session 1 are also reported in session 3:
+
+ C: D210 NOOP
+ S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (12121231000))
+ S: D210 OK Noop completed
+
+ The user modifies a private flag \Seen in session 1...
+
+ C: A240 STORE 7 +FLAGS.SILENT (\Seen)
+ S: * 7 FETCH (MODSEQ (12121231777))
+ S: A240 OK Store completed
+
+ ...which is only reported in session 2...
+
+ C: C270 NOOP
+ S: * 7 FETCH (FLAGS (\Deleted \Answered \Seen) MODSEQ
+ (12121231777))
+ S: C270 OK Noop completed
+
+ ...but not in session 3.
+
+ C: D300 NOOP
+ S: D300 OK Noop completed
+
+ And finally, the user removes flags \Answered (shared) and \Seen
+ (private) in session 1.
+
+ C: A330 STORE 7 -FLAGS.SILENT (\Answered \Seen)
+ S: * 7 FETCH (MODSEQ (12121245160))
+ S: A330 OK Store completed
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 15]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ Both changes are reported in the session 2...
+
+ C: C360 NOOP
+ S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (12121245160))
+ S: C360 OK Noop completed
+
+ ...and only changes to shared flags are reported in session 3.
+
+ C: D390 NOOP
+ S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (12121245160))
+ S: D390 OK Noop completed
+
+ Server implementers should also see Section 3.8 for additional
+ quality of implementation issues related to the FETCH command.
+
+3.4. MODSEQ Search Criterion in SEARCH
+
+ The MODSEQ criterion for the SEARCH command allows a client to search
+ for the metadata items that were modified since a specified moment.
+
+ Syntax: MODSEQ [<entry-name> <entry-type-req>] <mod-sequence-valzer>
+
+ Messages that have modification values that are equal to or
+ greater than <mod-sequence-valzer>. This allows a client, for
+ example, to find out which messages contain metadata items that
+ have changed since the last time it updated its disconnected
+ cache. The client may also specify <entry-name> (name of metadata
+ item) and <entry-type-req> (type of metadata item) before
+ <mod-sequence-valzer>. <entry-type-req> can be one of "shared",
+ "priv" (private), or "all". The latter means that the server
+ should use the biggest value among "priv" and "shared" mod-
+ sequences for the metadata item. If the server doesn't store
+ internally separate mod-sequences for different metadata items, it
+ MUST ignore <entry-name> and <entry-type-req>. Otherwise, the
+ server should use them to narrow down the search.
+
+ For a flag <flagname>, the corresponding <entry-name> has a form
+ "/flags/<flagname>" as defined in [IMAPABNF]. Note that the
+ leading "\" character that denotes a system flag has to be escaped
+ as per Section 4.3 of [IMAP4], as the <entry-name> uses syntax for
+ quoted strings.
+
+ If client specifies a MODSEQ criterion in a SEARCH command and the
+ server returns a non-empty SEARCH result, the server MUST also append
+ (to the end of the untagged SEARCH response) the highest mod-sequence
+ for all messages being returned. See also Section 3.5.
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 16]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ Example 15:
+
+ C: a SEARCH MODSEQ "/flags/\\draft" all 620162338
+ S: * SEARCH 2 5 6 7 11 12 18 19 20 23 (MODSEQ 917162500)
+ S: a OK Search complete
+
+ In the above example, the message numbers of any messages
+ containing the string "IMAP4" in the "value" attribute of the
+ "/comment" entry and having a mod-sequence equal to or greater
+ than 620162338 for the "\Draft" flag are returned in the search
+ results.
+
+ Example 16:
+
+ C: t SEARCH OR NOT MODSEQ 720162338 LARGER 50000
+ S: * SEARCH
+ S: t OK Search complete, nothing found
+
+3.5. Modified SEARCH Untagged Response
+
+ Data: zero or more numbers
+ mod-sequence value (omitted if no match)
+
+ This document extends syntax of the untagged SEARCH response to
+ include the highest mod-sequence for all messages being returned.
+
+ If a client specifies a MODSEQ criterion in a SEARCH (or UID SEARCH)
+ command and the server returns a non-empty SEARCH result, the server
+ MUST also append (to the end of the untagged SEARCH response) the
+ highest mod-sequence for all messages being returned. See Section
+ 3.4 for examples.
+
+3.6. HIGHESTMODSEQ Status Data Items
+
+ This document defines a new status data item:
+
+ HIGHESTMODSEQ
+
+ The highest mod-sequence value of all messages in the mailbox.
+ This is the same value that is returned by the server in the
+ HIGHESTMODSEQ response code in an OK untagged response (see
+ Section 3.1.1). If the server doesn't support the persistent
+ storage of mod-sequences for the mailbox (see Section 3.1.2), the
+ server MUST return 0 as the value of HIGHESTMODSEQ status data
+ item.
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 17]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ Example 17:
+
+ C: A042 STATUS blurdybloop (UIDNEXT MESSAGES HIGHESTMODSEQ)
+ S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292
+ HIGHESTMODSEQ 7011231777)
+ S: A042 OK STATUS completed
+
+3.7. CONDSTORE Parameter to SELECT and EXAMINE
+
+ The CONDSTORE extension defines a single optional select parameter,
+ "CONDSTORE", which tells the server that it MUST include the MODSEQ
+ fetch response data items in all subsequent unsolicited FETCH
+ responses.
+
+ The CONDSTORE parameter to SELECT/EXAMINE helps avoid a race
+ condition that might arise when one or more metadata items are
+ modified in another session after the server has sent the
+ HIGHESTMODSEQ response code and before the client was able to issue a
+ CONDSTORE enabling command.
+
+ Example 18:
+
+ C: A142 SELECT INBOX (CONDSTORE)
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 4392] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: * OK [HIGHESTMODSEQ 715194045007]
+ S: A142 OK [READ-WRITE] SELECT completed, CONDSTORE is now enabled
+
+3.8. Additional Quality-of-Implementation Issues
+
+ Server implementations should follow the following rule, which
+ applies to any successfully completed STORE/UID STORE (with and
+ without UNCHANGEDSINCE modifier), as well as to a FETCH command that
+ implicitly sets \Seen flag:
+
+ Adding the flag when it is already present or removing when it is
+ not present SHOULD NOT change the mod-sequence.
+
+ This will prevent spurious client synchronization requests.
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 18]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ However, note that client implementers MUST NOT rely on this server
+ behavior. A client can't distinguish between the case when a server
+ has violated the SHOULD mentioned above, and that when one or more
+ clients set and unset (or unset and set) the flag in another session.
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) [ABNF] notation. Elements not defined here can be found
+ in the formal syntax of the ABNF [ABNF], IMAP [IMAP4], and IMAP ABNF
+ extensions [IMAPABNF] specifications.
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper- or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ capability =/ "CONDSTORE"
+
+ status-att =/ "HIGHESTMODSEQ"
+ ;; extends non-terminal defined in RFC 3501.
+
+ status-att-val =/ "HIGHESTMODSEQ" SP mod-sequence-valzer
+ ;; extends non-terminal defined in [IMAPABNF].
+ ;; Value 0 denotes that the mailbox doesn't
+ ;; support persistent mod-sequences
+ ;; as described in Section 3.1.2
+
+ store-modifier =/ "UNCHANGEDSINCE" SP mod-sequence-valzer
+ ;; Only a single "UNCHANGEDSINCE" may be
+ ;; specified in a STORE operation
+
+ fetch-modifier =/ chgsince-fetch-mod
+ ;; conforms to the generic "fetch-modifier"
+ ;; syntax defined in [IMAPABNF].
+
+ chgsince-fetch-mod = "CHANGEDSINCE" SP mod-sequence-value
+ ;; CHANGEDSINCE FETCH modifier conforms to
+ ;; the fetch-modifier syntax
+
+ fetch-att =/ fetch-mod-sequence
+ ;; modifies original IMAP4 fetch-att
+
+ fetch-mod-sequence = "MODSEQ"
+
+ fetch-mod-resp = "MODSEQ" SP "(" permsg-modsequence ")"
+
+ msg-att-dynamic =/ fetch-mod-resp
+
+
+
+Melnikov & Hole Standards Track [Page 19]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ search-key =/ search-modsequence
+ ;; modifies original IMAP4 search-key
+ ;;
+ ;; This change applies to all commands
+ ;; referencing this non-terminal, in
+ ;; particular SEARCH.
+
+ search-modsequence = "MODSEQ" [search-modseq-ext] SP
+ mod-sequence-valzer
+
+ search-modseq-ext = SP entry-name SP entry-type-req
+
+ resp-text-code =/ "HIGHESTMODSEQ" SP mod-sequence-value /
+ "NOMODSEQ" /
+ "MODIFIED" SP set
+
+ entry-name = entry-flag-name
+
+ entry-flag-name = DQUOTE "/flags/" attr-flag DQUOTE
+ ;; each system or user defined flag <flag>
+ ;; is mapped to "/flags/<flag>".
+ ;;
+ ;; <entry-flag-name> follows the escape rules
+ ;; used by "quoted" string as described in
+ ;; Section 4.3 of [IMAP4], e.g., for the flag
+ ;; \Seen the corresponding <entry-name> is
+ ;; "/flags/\\seen", and for the flag
+ ;; $MDNSent, the corresponding <entry-name>
+ ;; is "/flags/$mdnsent".
+
+ entry-type-resp = "priv" / "shared"
+ ;; metadata item type
+
+ entry-type-req = entry-type-resp / "all"
+ ;; perform SEARCH operation on private
+ ;; metadata item, shared metadata item or both
+
+ permsg-modsequence = mod-sequence-value
+ ;; per message mod-sequence
+
+ mod-sequence-value = 1*DIGIT
+ ;; Positive unsigned 64-bit integer
+ ;; (mod-sequence)
+ ;; (1 <= n < 18,446,744,073,709,551,615)
+
+ mod-sequence-valzer = "0" / mod-sequence-value
+
+ search-sort-mod-seq = "(" "MODSEQ" SP mod-sequence-value ")"
+
+
+
+Melnikov & Hole Standards Track [Page 20]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ select-param =/ condstore-param
+ ;; conforms to the generic "select-param"
+ ;; non-terminal syntax defined in [IMAPABNF].
+
+ condstore-param = "CONDSTORE"
+
+ mailbox-data =/ "SEARCH" [1*(SP nz-number) SP
+ search-sort-mod-seq]
+
+ attr-flag = "\\Answered" / "\\Flagged" / "\\Deleted" /
+ "\\Seen" / "\\Draft" / attr-flag-keyword /
+ attr-flag-extension
+ ;; Does not include "\\Recent"
+
+ attr-flag-extension = "\\" atom
+ ;; Future expansion. Client implementations
+ ;; MUST accept flag-extension flags. Server
+ ;; implementations MUST NOT generate
+ ;; flag-extension flags except as defined by
+ ;; future standard or standards-track
+ ;; revisions of [IMAP4].
+
+ attr-flag-keyword = atom
+
+5. Server Implementation Considerations
+
+ This section describes how a server implementation that doesn't store
+ separate per-metadata mod-sequences for different metadata items can
+ avoid sending the MODIFIED response to any of the following
+ conditional STORE operations:
+
+ +FLAGS
+ -FLAGS
+ +FLAGS.SILENT
+ -FLAGS.SILENT
+
+ Note that the optimization described in this section can't be
+ performed in case of a conditional STORE FLAGS operation.
+
+ Let's use the following example. The client has issued
+
+ C: a106 STORE 100:150 (UNCHANGEDSINCE 212030000000)
+ +FLAGS.SILENT ($Processed)
+
+ When the server receives the command and parses it successfully, it
+ iterates through the message set and tries to execute the conditional
+ STORE command for each message.
+
+
+
+
+Melnikov & Hole Standards Track [Page 21]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+ Each server internally works as a client, i.e., it has to cache the
+ current state of all IMAP flags as it is known to the client. In
+ order to report flag changes to the client, the server compares the
+ cached values with the values in its database for IMAP flags.
+
+ Imagine that another client has changed the state of a flag \Deleted
+ on the message 101 and that the change updated the mod-sequence for
+ the message. The server knows that the mod-sequence for the mailbox
+ has changed; however, it also knows that:
+
+ a) the client is not interested in \Deleted flag, as it hasn't
+ included it in +FLAGS.SILENT operation; and
+
+ b) the state of the flag $Processed hasn't changed (the server can
+ determine this by comparing cached flag state with the state of
+ the flag in the database).
+
+ Therefore, the server doesn't have to report MODIFIED to the client.
+ Instead, the server may set $Processed flag, update the mod-sequence
+ for the message 101 once again and send an untagged FETCH response
+ with new mod-sequence and flags:
+
+ S: * 101 FETCH (MODSEQ (303011130956)
+ FLAGS ($Processed \Deleted \Answered))
+
+ See also Section 3.8 for additional quality-of-implementation issues.
+
+6. Security Considerations
+
+ It is believed that the Conditional STORE extension doesn't raise any
+ new security concerns that are not already discussed in [IMAP4].
+ However, the availability of this extension may make it possible for
+ IMAP4 to be used in critical applications it could not be used for
+ previously, making correct IMAP server implementation and operation
+ even more important.
+
+7. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ This document defines the CONDSTORE IMAP capability. IANA has added
+ it to the registry accordingly.
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 22]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+8. References
+
+8.1. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
+ ABNF", RFC 4466, April 2006.
+
+8.2. Informative References
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November 1997.
+
+ [ACL] Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
+ RFC 4314, December 2005.
+
+ [ANN] Daboo, C. and R. Gellens, "IMAP ANNOTATE Extension", Work
+ in Progress, March 2006.
+
+ [NTP] Mills, D., "Network Time Protocol (Version 3)
+ Specification, Implementation and Analysis", RFC 1305,
+ March 1992.
+
+ [RFC-2180] Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", RFC
+ 2180, July 1997.
+
+9. Acknowledgements
+
+ Some text was borrowed from "IMAP ANNOTATE Extension" [ANN] by
+ Randall Gellens and Cyrus Daboo and from "ACAP -- Application
+ Configuration Access Protocol" [ACAP] by Chris Newman and John Myers.
+
+ Many thanks to Randall Gellens for his thorough review of the
+ document.
+
+ The authors also acknowledge the feedback provided by Cyrus Daboo,
+ Larry Greenfield, Chris Newman, Harrie Hazewinkel, Arnt Gulbrandsen,
+ Timo Sirainen, Mark Crispin, Ned Freed, Ken Murchison, and Dave
+ Cridland.
+
+
+
+
+Melnikov & Hole Standards Track [Page 23]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+Authors' Addresses
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex
+ TW12 2BX,
+ United Kingdom
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Steve Hole
+ ACI WorldWide/MessagingDirect
+ #1807, 10088 102 Ave
+ Edmonton, AB
+ T5J 2Z1
+ Canada
+
+ EMail: Steve.Hole@messagingdirect.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 24]
+
+RFC 4551 IMAP Extension for Conditional STORE June 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Melnikov & Hole Standards Track [Page 25]
+
diff --git a/imap/docs/rfc/rfc4616.txt b/imap/docs/rfc/rfc4616.txt
new file mode 100644
index 00000000..991189d5
--- /dev/null
+++ b/imap/docs/rfc/rfc4616.txt
@@ -0,0 +1,619 @@
+
+
+
+
+
+
+Network Working Group K. Zeilenga, Ed.
+Request for Comments: 4616 OpenLDAP Foundation
+Updates: 2595 August 2006
+Category: Standards Track
+
+
+ The PLAIN Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2006).
+
+Abstract
+
+ This document defines a simple clear-text user/password Simple
+ Authentication and Security Layer (SASL) mechanism called the PLAIN
+ mechanism. The PLAIN mechanism is intended to be used, in
+ combination with data confidentiality services provided by a lower
+ layer, in protocols that lack a simple password authentication
+ command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 1]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+1. Introduction
+
+ Clear-text, multiple-use passwords are simple, interoperate with
+ almost all existing operating system authentication databases, and
+ are useful for a smooth transition to a more secure password-based
+ authentication mechanism. The drawback is that they are unacceptable
+ for use over network connections where data confidentiality is not
+ ensured.
+
+ This document defines the PLAIN Simple Authentication and Security
+ Layer ([SASL]) mechanism for use in protocols with no clear-text
+ login command (e.g., [ACAP] or [SMTP-AUTH]). This document updates
+ RFC 2595, replacing Section 6. Changes since RFC 2595 are detailed
+ in Appendix A.
+
+ The name associated with this mechanism is "PLAIN".
+
+ The PLAIN SASL mechanism does not provide a security layer.
+
+ The PLAIN mechanism should not be used without adequate data security
+ protection as this mechanism affords no integrity or confidentiality
+ protections itself. The mechanism is intended to be used with data
+ security protections provided by application-layer protocol,
+ generally through its use of Transport Layer Security ([TLS])
+ services.
+
+ By default, implementations SHOULD advertise and make use of the
+ PLAIN mechanism only when adequate data security services are in
+ place. Specifications for IETF protocols that indicate that this
+ mechanism is an applicable authentication mechanism MUST mandate that
+ implementations support an strong data security service, such as TLS.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [Keywords].
+
+2. PLAIN SASL Mechanism
+
+ The mechanism consists of a single message, a string of [UTF-8]
+ encoded [Unicode] characters, from the client to the server. The
+ client presents the authorization identity (identity to act as),
+ followed by a NUL (U+0000) character, followed by the authentication
+ identity (identity whose password will be used), followed by a NUL
+ (U+0000) character, followed by the clear-text password. As with
+ other SASL mechanisms, the client does not provide an authorization
+ identity when it wishes the server to derive an identity from the
+ credentials and use that as the authorization identity.
+
+
+
+
+Zeilenga Standards Track [Page 2]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ The formal grammar for the client message using Augmented BNF [ABNF]
+ follows.
+
+ message = [authzid] UTF8NUL authcid UTF8NUL passwd
+ authcid = 1*SAFE ; MUST accept up to 255 octets
+ authzid = 1*SAFE ; MUST accept up to 255 octets
+ passwd = 1*SAFE ; MUST accept up to 255 octets
+ UTF8NUL = %x00 ; UTF-8 encoded NUL character
+
+ SAFE = UTF1 / UTF2 / UTF3 / UTF4
+ ;; any UTF-8 encoded Unicode character except NUL
+
+ UTF1 = %x01-7F ;; except NUL
+ UTF2 = %xC2-DF UTF0
+ UTF3 = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) /
+ %xED %x80-9F UTF0 / %xEE-EF 2(UTF0)
+ UTF4 = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) /
+ %xF4 %x80-8F 2(UTF0)
+ UTF0 = %x80-BF
+
+ The authorization identity (authzid), authentication identity
+ (authcid), password (passwd), and NUL character deliminators SHALL be
+ transferred as [UTF-8] encoded strings of [Unicode] characters. As
+ the NUL (U+0000) character is used as a deliminator, the NUL (U+0000)
+ character MUST NOT appear in authzid, authcid, or passwd productions.
+
+ The form of the authzid production is specific to the application-
+ level protocol's SASL profile [SASL]. The authcid and passwd
+ productions are form-free. Use of non-visible characters or
+ characters that a user may be unable to enter on some keyboards is
+ discouraged.
+
+ Servers MUST be capable of accepting authzid, authcid, and passwd
+ productions up to and including 255 octets. It is noted that the
+ UTF-8 encoding of a Unicode character may be as long as 4 octets.
+
+ Upon receipt of the message, the server will verify the presented (in
+ the message) authentication identity (authcid) and password (passwd)
+ with the system authentication database, and it will verify that the
+ authentication credentials permit the client to act as the (presented
+ or derived) authorization identity (authzid). If both steps succeed,
+ the user is authenticated.
+
+ The presented authentication identity and password strings, as well
+ as the database authentication identity and password strings, are to
+ be prepared before being used in the verification process. The
+ [SASLPrep] profile of the [StringPrep] algorithm is the RECOMMENDED
+ preparation algorithm. The SASLprep preparation algorithm is
+
+
+
+Zeilenga Standards Track [Page 3]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ recommended to improve the likelihood that comparisons behave in an
+ expected manner. The SASLprep preparation algorithm is not mandatory
+ so as to allow the server to employ other preparation algorithms
+ (including none) when appropriate. For instance, use of a different
+ preparation algorithm may be necessary for the server to interoperate
+ with an external system.
+
+ When preparing the presented strings using [SASLPrep], the presented
+ strings are to be treated as "query" strings (Section 7 of
+ [StringPrep]) and hence unassigned code points are allowed to appear
+ in their prepared output. When preparing the database strings using
+ [SASLPrep], the database strings are to be treated as "stored"
+ strings (Section 7 of [StringPrep]) and hence unassigned code points
+ are prohibited from appearing in their prepared output.
+
+ Regardless of the preparation algorithm used, if the output of a
+ non-invertible function (e.g., hash) of the expected string is
+ stored, the string MUST be prepared before input to that function.
+
+ Regardless of the preparation algorithm used, if preparation fails or
+ results in an empty string, verification SHALL fail.
+
+ When no authorization identity is provided, the server derives an
+ authorization identity from the prepared representation of the
+ provided authentication identity string. This ensures that the
+ derivation of different representations of the authentication
+ identity produces the same authorization identity.
+
+ The server MAY use the credentials to initialize any new
+ authentication database, such as one suitable for [CRAM-MD5] or
+ [DIGEST-MD5].
+
+3. Pseudo-Code
+
+ This section provides pseudo-code illustrating the verification
+ process (using hashed passwords and the SASLprep preparation
+ function) discussed above. This section is not definitive.
+
+ boolean Verify(string authzid, string authcid, string passwd) {
+ string pAuthcid = SASLprep(authcid, true); # prepare authcid
+ string pPasswd = SASLprep(passwd, true); # prepare passwd
+ if (pAuthcid == NULL || pPasswd == NULL) {
+ return false; # preparation failed
+ }
+ if (pAuthcid == "" || pPasswd == "") {
+ return false; # empty prepared string
+ }
+
+
+
+
+Zeilenga Standards Track [Page 4]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ storedHash = FetchPasswordHash(pAuthcid);
+ if (storedHash == NULL || storedHash == "") {
+ return false; # error or unknown authcid
+ }
+
+ if (!Compare(storedHash, Hash(pPasswd))) {
+ return false; # incorrect password
+ }
+
+ if (authzid == NULL ) {
+ authzid = DeriveAuthzid(pAuthcid);
+ if (authzid == NULL || authzid == "") {
+ return false; # could not derive authzid
+ }
+ }
+
+ if (!Authorize(pAuthcid, authzid)) {
+ return false; # not authorized
+ }
+
+ return true;
+ }
+
+ The second parameter of the SASLprep function, when true, indicates
+ that unassigned code points are allowed in the input. When the
+ SASLprep function is called to prepare the password prior to
+ computing the stored hash, the second parameter would be false.
+
+ The second parameter provided to the Authorize function is not
+ prepared by this code. The application-level SASL profile should be
+ consulted to determine what, if any, preparation is necessary.
+
+ Note that the DeriveAuthzid and Authorize functions (whether
+ implemented as one function or two, whether designed in a manner in
+ which these functions or whether the mechanism implementation can be
+ reused elsewhere) require knowledge and understanding of mechanism
+ and the application-level protocol specification and/or
+ implementation details to implement.
+
+ Note that the Authorize function outcome is clearly dependent on
+ details of the local authorization model and policy. Both functions
+ may be dependent on other factors as well.
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 5]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+4. Examples
+
+ This section provides examples of PLAIN authentication exchanges.
+ The examples are intended to help the readers understand the above
+ text. The examples are not definitive.
+
+ "C:" and "S:" indicate lines sent by the client and server,
+ respectively. "<NUL>" represents a single NUL (U+0000) character.
+ The Application Configuration Access Protocol ([ACAP]) is used in the
+ examples.
+
+ The first example shows how the PLAIN mechanism might be used for
+ user authentication.
+
+ S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+ C: a002 AUTHENTICATE "PLAIN"
+ S: + ""
+ C: {21}
+ C: <NUL>tim<NUL>tanstaaftanstaaf
+ S: a002 OK "Authenticated"
+
+ The second example shows how the PLAIN mechanism might be used to
+ attempt to assume the identity of another user. In this example, the
+ server rejects the request. Also, this example makes use of the
+ protocol optional initial response capability to eliminate a round-
+ trip.
+
+ S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
+ C: a001 STARTTLS
+ S: a001 OK "Begin TLS negotiation now"
+ <TLS negotiation, further commands are under TLS layer>
+ S: * ACAP (SASL "CRAM-MD5" "PLAIN")
+ C: a002 AUTHENTICATE "PLAIN" {20+}
+ C: Ursel<NUL>Kurt<NUL>xipj3plmq
+ S: a002 NO "Not authorized to requested authorization identity"
+
+5. Security Considerations
+
+ As the PLAIN mechanism itself provided no integrity or
+ confidentiality protections, it should not be used without adequate
+ external data security protection, such as TLS services provided by
+ many application-layer protocols. By default, implementations SHOULD
+ NOT advertise and SHOULD NOT make use of the PLAIN mechanism unless
+ adequate data security services are in place.
+
+
+
+Zeilenga Standards Track [Page 6]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ When the PLAIN mechanism is used, the server gains the ability to
+ impersonate the user to all services with the same password
+ regardless of any encryption provided by TLS or other confidentiality
+ protection mechanisms. Whereas many other authentication mechanisms
+ have similar weaknesses, stronger SASL mechanisms address this issue.
+ Clients are encouraged to have an operational mode where all
+ mechanisms that are likely to reveal the user's password to the
+ server are disabled.
+
+ General [SASL] security considerations apply to this mechanism.
+
+ Unicode, [UTF-8], and [StringPrep] security considerations also
+ apply.
+
+6. IANA Considerations
+
+ The SASL Mechanism registry [IANA-SASL] entry for the PLAIN mechanism
+ has been updated by the IANA to reflect that this document now
+ provides its technical specification.
+
+ To: iana@iana.org
+ Subject: Updated Registration of SASL mechanism PLAIN
+
+ SASL mechanism name: PLAIN
+ Security considerations: See RFC 4616.
+ Published specification (optional, recommended): RFC 4616
+ Person & email address to contact for further information:
+ Kurt Zeilenga <kurt@openldap.org>
+ IETF SASL WG <ietf-sasl@imc.org>
+ Intended usage: COMMON
+ Author/Change controller: IESG <iesg@ietf.org>
+ Note: Updates existing entry for PLAIN
+
+7. Acknowledgements
+
+ This document is a revision of RFC 2595 by Chris Newman. Portions of
+ the grammar defined in Section 2 were borrowed from [UTF-8] by
+ Francois Yergeau.
+
+ This document is a product of the IETF Simple Authentication and
+ Security Layer (SASL) Working Group.
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 7]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+8. Normative References
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+ [Keywords] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [SASL] Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
+ Authentication and Security Layer (SASL)", RFC 4422,
+ June 2006.
+
+ [SASLPrep] Zeilenga, K., "SASLprep: Stringprep Profile for User
+ Names and Passwords", RFC 4013, February 2005.
+
+ [StringPrep] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC 3454,
+ December 2002.
+
+ [Unicode] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0" is defined by "The Unicode Standard, Version
+ 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+ 61633-5), as amended by the "Unicode Standard Annex
+ #27: Unicode 3.1"
+ (http://www.unicode.org/reports/tr27/) and by the
+ "Unicode Standard Annex #28: Unicode 3.2"
+ (http://www.unicode.org/reports/tr28/).
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [TLS] Dierks, T. and E. Rescorla, "The Transport Layer
+ Security (TLS) Protocol Version 1.1", RFC 4346, April
+ 2006.
+
+9. Informative References
+
+ [ACAP] Newman, C. and J. Myers, "ACAP -- Application
+ Configuration Access Protocol", RFC 2244, November
+ 1997.
+
+ [CRAM-MD5] Nerenberg, L., Ed., "The CRAM-MD5 SASL Mechanism", Work
+ in Progress, June 2006.
+
+ [DIGEST-MD5] Melnikov, A., Ed., "Using Digest Authentication as a
+ SASL Mechanism", Work in Progress, June 2006.
+
+
+
+
+
+Zeilenga Standards Track [Page 8]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+ [IANA-SASL] IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
+ MECHANISMS",
+ <http://www.iana.org/assignments/sasl-mechanisms>.
+
+ [SMTP-AUTH] Myers, J., "SMTP Service Extension for Authentication",
+ RFC 2554, March 1999.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 9]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+Appendix A. Changes since RFC 2595
+
+ This appendix is non-normative.
+
+ This document replaces Section 6 of RFC 2595.
+
+ The specification details how the server is to compare client-
+ provided character strings with stored character strings.
+
+ The ABNF grammar was updated. In particular, the grammar now allows
+ LINE FEED (U+000A) and CARRIAGE RETURN (U+000D) characters in the
+ authzid, authcid, passwd productions. However, whether these control
+ characters may be used depends on the string preparation rules
+ applicable to the production. For passwd and authcid productions,
+ control characters are prohibited. For authzid, one must consult the
+ application-level SASL profile. This change allows PLAIN to carry
+ all possible authorization identity strings allowed in SASL.
+
+ Pseudo-code was added.
+
+ The example section was expanded to illustrate more features of the
+ PLAIN mechanism.
+
+Editor's Address
+
+ Kurt D. Zeilenga
+ OpenLDAP Foundation
+
+ EMail: Kurt@OpenLDAP.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 10]
+
+RFC 4616 The PLAIN SASL Mechanism August 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+ ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+ INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+ INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is provided by the IETF
+ Administrative Support Activity (IASA).
+
+
+
+
+
+
+
+Zeilenga Standards Track [Page 11]
+
diff --git a/imap/docs/rfc/rfc4731.txt b/imap/docs/rfc/rfc4731.txt
new file mode 100644
index 00000000..8c4869aa
--- /dev/null
+++ b/imap/docs/rfc/rfc4731.txt
@@ -0,0 +1,451 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 4731 Isode Ltd
+Category: Standards Track D. Cridland
+ Inventure Systems Ltd
+ November 2006
+
+
+ IMAP4 Extension to SEARCH Command for Controlling
+ What Kind of Information Is Returned
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2006).
+
+Abstract
+
+ This document extends IMAP (RFC 3501) SEARCH and UID SEARCH commands
+ with several result options, which can control what kind of
+ information is returned. The following result options are defined:
+ minimal value, maximal value, all found messages, and number of found
+ messages.
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 2. Conventions Used in This Document ...............................2
+ 3. IMAP Protocol Changes ...........................................2
+ 3.1. New SEARCH/UID SEARCH Result Options .......................2
+ 3.2. Interaction with CONDSTORE extension .......................4
+ 4. Formal Syntax ...................................................5
+ 5. Security Considerations .........................................6
+ 6. IANA Considerations .............................................6
+ 7. Normative References ............................................6
+ 8. Acknowledgments .................................................6
+
+
+
+
+
+
+
+
+
+Melnikov & Cridland Standards Track [Page 1]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+1. Introduction
+
+ [IMAPABNF] extended SEARCH and UID SEARCH commands with result
+ specifiers (also known as result options), which can control what
+ kind of information is returned.
+
+ A server advertising the ESEARCH capability supports the following
+ result options: minimal value, maximal value, all found messages,
+ and number of found messages. These result options allow clients to
+ get SEARCH results in more convenient forms, while also saving
+ bandwidth required to transport the results, for example, by finding
+ the first unseen message or returning the number of unseen or deleted
+ messages. Also, when a single MIN or a single MAX result option is
+ specified, servers can optimize execution of SEARCHes.
+
+2. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+3. IMAP Protocol Changes
+
+3.1. New SEARCH/UID SEARCH Result Options
+
+ The SEARCH/UID SEARCH commands are extended to allow for the
+ following result options:
+
+ MIN
+ Return the lowest message number/UID that satisfies the SEARCH
+ criteria.
+
+ If the SEARCH results in no matches, the server MUST NOT
+ include the MIN result option in the ESEARCH response; however,
+ it still MUST send the ESEARCH response.
+
+ MAX
+ Return the highest message number/UID that satisfies the SEARCH
+ criteria.
+
+ If the SEARCH results in no matches, the server MUST NOT
+ include the MAX result option in the ESEARCH response; however,
+ it still MUST send the ESEARCH response.
+
+
+
+
+
+Melnikov & Cridland Standards Track [Page 2]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+ ALL
+ Return all message numbers/UIDs that satisfy the SEARCH
+ criteria. Unlike regular (unextended) SEARCH, the messages are
+ always returned using the sequence-set syntax. A sequence-set
+ representation may be more compact and can be used as is in a
+ subsequent command that accepts sequence-set. Note, the client
+ MUST NOT assume that messages/UIDs will be listed in any
+ particular order.
+
+ If the SEARCH results in no matches, the server MUST NOT
+ include the ALL result option in the ESEARCH response; however,
+ it still MUST send the ESEARCH response.
+
+ COUNT
+ Return number of the messages that satisfy the SEARCH criteria.
+ This result option MUST always be included in the ESEARCH
+ response.
+
+ If one or more result options described above are specified, the
+ extended SEARCH command MUST return a single ESEARCH response
+ [IMAPABNF], instead of the SEARCH response.
+
+ An extended UID SEARCH command MUST cause an ESEARCH response with
+ the UID indicator present.
+
+ Note that future extensions to this document can allow servers to
+ return multiple ESEARCH responses for a single extended SEARCH
+ command. These extensions will have to describe how results from
+ multiple ESEARCH responses are to be amalgamated.
+
+ If the list of result options is empty, that requests the server to
+ return an ESEARCH response instead of the SEARCH response. This is
+ equivalent to "(ALL)".
+
+ Example: C: A282 SEARCH RETURN (MIN COUNT) FLAGGED
+ SINCE 1-Feb-1994 NOT FROM "Smith"
+ S: * ESEARCH (TAG "A282") MIN 2 COUNT 3
+ S: A282 OK SEARCH completed
+
+ Example: C: A283 SEARCH RETURN () FLAGGED
+ SINCE 1-Feb-1994 NOT FROM "Smith"
+ S: * ESEARCH (TAG "A283") ALL 2,10:11
+ S: A283 OK SEARCH completed
+
+ The following example demonstrates finding the first unseen message
+ as returned in the UNSEEN response code on a successful SELECT
+ command:
+
+
+
+
+Melnikov & Cridland Standards Track [Page 3]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+ Example: C: A284 SEARCH RETURN (MIN) UNSEEN
+ S: * ESEARCH (TAG "A284") MIN 4
+ S: A284 OK SEARCH completed
+
+ The following example demonstrates that if the ESEARCH UID indicator
+ is present, all data in the ESEARCH response is referring to UIDs;
+ for example, the MIN result specifier will be followed by a UID.
+
+ Example: C: A285 UID SEARCH RETURN (MIN MAX) 1:5000
+ S: * ESEARCH (TAG "A285") UID MIN 7 MAX 3800
+ S: A285 OK SEARCH completed
+
+ The following example demonstrates returning the number of deleted
+ messages:
+
+ Example: C: A286 SEARCH RETURN (COUNT) DELETED
+ S: * ESEARCH (TAG "A286") COUNT 15
+ S: A286 OK SEARCH completed
+
+3.2. Interaction with CONDSTORE extension
+
+ When the server supports both the ESEARCH and the CONDSTORE
+ [CONDSTORE] extension, and the client requests one or more result
+ option described in section 3.1 together with the MODSEQ search
+ criterion in the same SEARCH/UID SEARCH command, then the server MUST
+ return the ESEARCH response containing the MODSEQ result option
+ (described in the following paragraph) instead of the extended SEARCH
+ response described in section 3.5 of [CONDSTORE].
+
+ If the SEARCH/UID SEARCH command contained a single MIN or MAX result
+ option, the MODSEQ result option contains the mod-sequence for the
+ found message. If the SEARCH/UID SEARCH command contained both MIN
+ and MAX result options and no ALL/COUNT option, the MODSEQ result
+ option contains the highest mod-sequence for the two returned
+ messages. Otherwise the MODSEQ result option contains the highest
+ mod-sequence for all messages being returned.
+
+ Example: The following example demonstrates how Example 15 from
+ [CONDSTORE] would look in the presence of one or more result option:
+
+ C: a1 SEARCH RETURN (MIN) MODSEQ "/flags/\\draft"
+ all 620162338
+ S: * ESEARCH (TAG "a1") MIN 2 MODSEQ 917162488
+ S: a1 OK Search complete
+
+ C: a2 SEARCH RETURN (MAX) MODSEQ "/flags/\\draft"
+ all 620162338
+ S: * ESEARCH (TAG "a2") MAX 23 MODSEQ 907162321
+
+
+
+Melnikov & Cridland Standards Track [Page 4]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+ S: a2 OK Search complete
+
+ C: a3 SEARCH RETURN (MIN MAX) MODSEQ "/flags/\\draft"
+ all 620162338
+ S: * ESEARCH (TAG "a3") MIN 2 MAX 23 MODSEQ 917162488
+ S: a3 OK Search complete
+
+ C: a4 SEARCH RETURN (MIN COUNT) MODSEQ "/flags/\\draft"
+ all 620162338
+ S: * ESEARCH (TAG "a4") MIN 2 COUNT 10 MODSEQ 917162500
+ S: a4 OK Search complete
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ Non-terminals referenced but not defined below are as defined by
+ [IMAP4], [CONDSTORE], or [IMAPABNF].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lowercase characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ capability =/ "ESEARCH"
+
+ search-return-data = "MIN" SP nz-number /
+ "MAX" SP nz-number /
+ "ALL" SP sequence-set /
+ "COUNT" SP number
+ ;; conforms to the generic
+ ;; search-return-data syntax defined
+ ;; in [IMAPABNF]
+
+ search-return-opt = "MIN" / "MAX" / "ALL" / "COUNT"
+ ;; conforms to generic search-return-opt
+ ;; syntax defined in [IMAPABNF]
+
+ When the CONDSTORE [CONDSTORE] IMAP extension is also supported,
+ the ABNF is updated as follows:
+
+ search-return-data =/ "MODSEQ" SP mod-sequence-value
+ ;; mod-sequence-value is defined
+ ;; in [CONDSTORE]
+
+
+
+
+
+
+Melnikov & Cridland Standards Track [Page 5]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+5. Security Considerations
+
+ In the general case, the IMAP SEARCH/UID SEARCH commands can be CPU
+ and/or IO intensive, and are seen by some as a potential attack point
+ for denial of service attacks, so some sites/implementations even
+ disable them entirely. This is quite unfortunate, as SEARCH command
+ is one of the best examples demonstrating IMAP advantage over POP3.
+
+ The ALL and COUNT return options don't change how SEARCH is working
+ internally; they only change how information about found messages is
+ returned. MIN and MAX SEARCH result options described in this
+ document can lighten the load on IMAP servers that choose to optimize
+ SEARCHes containing only one or both of them.
+
+ It is believed that this extension doesn't raise any additional
+ security concerns not already discussed in [IMAP4].
+
+6. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track RFC
+ or an IESG-approved experimental RFC. The registry is currently
+ located at <http://www.iana.org/assignments/imap4-capabilities>.
+
+ This document defines the ESEARCH IMAP capability, which IANA added
+ to the registry.
+
+7. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [ABNF] Crocker, D. (Ed.) and P. Overell , "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+ [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
+ ABNF", RFC 4466, April 2006..
+
+ [CONDSTORE] Melnikov, A. and S. Hole, "IMAP Extension for Conditional
+ STORE", RFC 4551, June 2006.
+
+8. Acknowledgments
+
+ Thanks to Michael Wener, Arnt Gulbrandsen, Cyrus Daboo, Mark Crispin,
+ and Pete Maclean for comments and corrections.
+
+
+
+
+Melnikov & Cridland Standards Track [Page 6]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+Authors' Addresses
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex, TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Dave A. Cridland
+ Inventure Systems Limited
+
+ EMail: dave.cridland@inventuresystems.co.uk
+ URL: http://invsys.co.uk/dave/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+Melnikov & Cridland Standards Track [Page 7]
+
+RFC 4731 IMAP4 Extension to SEARCH November 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
+ AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
+ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
+ THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
+ IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
+ PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+Melnikov & Cridland Standards Track [Page 8]
+
diff --git a/imap/docs/rfc/rfc4752.txt b/imap/docs/rfc/rfc4752.txt
new file mode 100644
index 00000000..bfd8e30b
--- /dev/null
+++ b/imap/docs/rfc/rfc4752.txt
@@ -0,0 +1,563 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov, Ed.
+Request for Comments: 4752 Isode
+Obsoletes: 2222 November 2006
+Category: Standards Track
+
+
+ The Kerberos V5 ("GSSAPI")
+ Simple Authentication and Security Layer (SASL) Mechanism
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2006).
+
+Abstract
+
+ The Simple Authentication and Security Layer (SASL) is a framework
+ for adding authentication support to connection-based protocols.
+ This document describes the method for using the Generic Security
+ Service Application Program Interface (GSS-API) Kerberos V5 in the
+ SASL.
+
+ This document replaces Section 7.2 of RFC 2222, the definition of the
+ "GSSAPI" SASL mechanism. This document, together with RFC 4422,
+ obsoletes RFC 2222.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 1]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 1.1. Relationship to Other Documents ............................2
+ 2. Conventions Used in This Document ...............................2
+ 3. Kerberos V5 GSS-API Mechanism ...................................2
+ 3.1. Client Side of Authentication Protocol Exchange ............3
+ 3.2. Server Side of Authentication Protocol Exchange ............4
+ 3.3. Security Layer .............................................6
+ 4. IANA Considerations .............................................7
+ 5. Security Considerations .........................................7
+ 6. Acknowledgements ................................................8
+ 7. Changes since RFC 2222 ..........................................8
+ 8. References ......................................................8
+ 8.1. Normative References .......................................8
+ 8.2. Informative References .....................................9
+
+1. Introduction
+
+ This specification documents currently deployed Simple Authentication
+ and Security Layer (SASL [SASL]) mechanism supporting the Kerberos V5
+ [KERBEROS] Generic Security Service Application Program Interface
+ ([GSS-API]) mechanism [RFC4121]. The authentication sequence is
+ described in Section 3. Note that the described authentication
+ sequence has known limitations, in particular, it lacks channel
+ bindings and the number of round-trips required to complete
+ authentication exchange is not minimal. SASL WG is working on a
+ separate document that should address these limitations.
+
+1.1. Relationship to Other Documents
+
+ This document, together with RFC 4422, obsoletes RFC 2222 in its
+ entirety. This document replaces Section 7.2 of RFC 2222. The
+ remainder is obsoleted as detailed in Section 1.2 of RFC 4422.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as defined in "Key words for
+ use in RFCs to Indicate Requirement Levels" [KEYWORDS].
+
+3. Kerberos V5 GSS-API Mechanism
+
+ The SASL mechanism name for the Kerberos V5 GSS-API mechanism
+ [RFC4121] is "GSSAPI". Though known as the SASL GSSAPI mechanism,
+ the mechanism is specifically tied to Kerberos V5 and GSS-API's
+ Kerberos V5 mechanism.
+
+
+
+
+Melnikov Standards Track [Page 2]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ The GSSAPI SASL mechanism is a "client goes first" SASL mechanism;
+ i.e., it starts with the client sending a "response" created as
+ described in the following section.
+
+ The implementation MAY set any GSS-API flags or arguments not
+ mentioned in this specification as is necessary for the
+ implementation to enforce its security policy.
+
+ Note that major status codes returned by GSS_Init_sec_context() or
+ GSS_Accept_sec_context() other than GSS_S_COMPLETE or
+ GSS_S_CONTINUE_NEEDED cause authentication failure. Major status
+ codes returned by GSS_Unwrap() other than GSS_S_COMPLETE (without any
+ additional supplementary status codes) cause authentication and/or
+ security layer failure.
+
+3.1. Client Side of Authentication Protocol Exchange
+
+ The client calls GSS_Init_sec_context, passing in
+ input_context_handle of 0 (initially), mech_type of the Kerberos V5
+ GSS-API mechanism [KRB5GSS], chan_binding of NULL, and targ_name
+ equal to output_name from GSS_Import_Name called with input_name_type
+ of GSS_C_NT_HOSTBASED_SERVICE (*) and input_name_string of
+ "service@hostname" where "service" is the service name specified in
+ the protocol's profile, and "hostname" is the fully qualified host
+ name of the server. When calling the GSS_Init_sec_context, the
+ client MUST pass the integ_req_flag of TRUE (**). If the client will
+ be requesting a security layer, it MUST also supply to the
+ GSS_Init_sec_context a mutual_req_flag of TRUE, and a
+ sequence_req_flag of TRUE. If the client will be requesting a
+ security layer providing confidentiality protection, it MUST also
+ supply to the GSS_Init_sec_context a conf_req_flag of TRUE. The
+ client then responds with the resulting output_token. If
+ GSS_Init_sec_context returns GSS_S_CONTINUE_NEEDED, then the client
+ should expect the server to issue a token in a subsequent challenge.
+ The client must pass the token to another call to
+ GSS_Init_sec_context, repeating the actions in this paragraph.
+
+ (*) Clients MAY use name types other than GSS_C_NT_HOSTBASED_SERVICE
+ to import servers' acceptor names, but only when they have a priori
+ knowledge that the servers support alternate name types. Otherwise
+ clients MUST use GSS_C_NT_HOSTBASED_SERVICE for importing acceptor
+ names.
+
+ (**) Note that RFC 2222 [RFC2222] implementations will not work with
+ GSS-API implementations that require integ_req_flag to be true. No
+ implementations of RFC 1964 [KRB5GSS] or RFC 4121 [RFC4121] that
+ require integ_req_flag to be true are believed to exist and it is
+ expected that any future update to [RFC4121] will require that
+
+
+
+Melnikov Standards Track [Page 3]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ integrity be available even in not explicitly requested by the
+ application.
+
+ When GSS_Init_sec_context returns GSS_S_COMPLETE, the client examines
+ the context to ensure that it provides a level of protection
+ permitted by the client's security policy. In particular, if the
+ integ_avail flag is not set in the context, then no security layer
+ can be offered or accepted.
+
+ If the conf_avail flag is not set in the context, then no security
+ layer with confidentiality can be offered or accepted. If the
+ context is acceptable, the client takes the following actions: If the
+ last call to GSS_Init_sec_context returned an output_token, then the
+ client responds with the output_token, otherwise the client responds
+ with no data. The client should then expect the server to issue a
+ token in a subsequent challenge. The client passes this token to
+ GSS_Unwrap and interprets the first octet of resulting cleartext as a
+ bit-mask specifying the security layers supported by the server and
+ the second through fourth octets as the maximum size output_message
+ the server is able to receive (in network byte order). If the
+ resulting cleartext is not 4 octets long, the client fails the
+ negotiation. The client verifies that the server maximum buffer is 0
+ if the server does not advertise support for any security layer.
+
+ The client then constructs data, with the first octet containing the
+ bit-mask specifying the selected security layer, the second through
+ fourth octets containing in network byte order the maximum size
+ output_message the client is able to receive (which MUST be 0 if the
+ client does not support any security layer), and the remaining octets
+ containing the UTF-8 [UTF8] encoded authorization identity.
+ (Implementation note: The authorization identity is not terminated
+ with the zero-valued (%x00) octet (e.g., the UTF-8 encoding of the
+ NUL (U+0000) character)). The client passes the data to GSS_Wrap
+ with conf_flag set to FALSE and responds with the generated
+ output_message. The client can then consider the server
+ authenticated.
+
+3.2. Server Side of Authentication Protocol Exchange
+
+ A server MUST NOT advertise support for the "GSSAPI" SASL mechanism
+ described in this document unless it has acceptor credential for the
+ Kerberos V GSS-API mechanism [KRB5GSS].
+
+ The server passes the initial client response to
+ GSS_Accept_sec_context as input_token, setting input_context_handle
+ to 0 (initially), chan_binding of NULL, and a suitable
+ acceptor_cred_handle (see below). If GSS_Accept_sec_context returns
+ GSS_S_CONTINUE_NEEDED, the server returns the generated output_token
+
+
+
+Melnikov Standards Track [Page 4]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ to the client in challenge and passes the resulting response to
+ another call to GSS_Accept_sec_context, repeating the actions in this
+ paragraph.
+
+ Servers SHOULD use a credential obtained by calling GSS_Acquire_cred
+ or GSS_Add_cred for the GSS_C_NO_NAME desired_name and the Object
+ Identifier (OID) of the Kerberos V5 GSS-API mechanism [KRB5GSS](*).
+ Servers MAY use GSS_C_NO_CREDENTIAL as an acceptor credential handle.
+ Servers MAY use a credential obtained by calling GSS_Acquire_cred or
+ GSS_Add_cred for the server's principal name(s) (**) and the Kerberos
+ V5 GSS-API mechanism [KRB5GSS].
+
+ (*) Unlike GSS_Add_cred the GSS_Acquire_cred uses an OID set of GSS-
+ API mechanism as an input parameter. The OID set can be created by
+ using GSS_Create_empty_OID_set and GSS_Add_OID_set_member. It can be
+ freed by calling the GSS_Release_oid_set.
+
+
+ (**) Use of server's principal names having
+ GSS_C_NT_HOSTBASED_SERVICE name type and "service@hostname" format,
+ where "service" is the service name specified in the protocol's
+ profile, and "hostname" is the fully qualified host name of the
+ server, is RECOMMENDED. The server name is generated by calling
+ GSS_Import_name with input_name_type of GSS_C_NT_HOSTBASED_SERVICE
+ and input_name_string of "service@hostname".
+
+ Upon successful establishment of the security context (i.e.,
+ GSS_Accept_sec_context returns GSS_S_COMPLETE), the server SHOULD
+ verify that the negotiated GSS-API mechanism is indeed Kerberos V5
+ [KRB5GSS]. This is done by examining the value of the mech_type
+ parameter returned from the GSS_Accept_sec_context call. If the
+ value differs, SASL authentication MUST be aborted.
+
+ Upon successful establishment of the security context and if the
+ server used GSS_C_NO_NAME/GSS_C_NO_CREDENTIAL to create acceptor
+ credential handle, the server SHOULD also check using the
+ GSS_Inquire_context that the target_name used by the client matches
+ either
+
+ - the GSS_C_NT_HOSTBASED_SERVICE "service@hostname" name syntax,
+ where "service" is the service name specified in the application
+ protocol's profile,
+
+ or
+
+ - the GSS_KRB5_NT_PRINCIPAL_NAME [KRB5GSS] name syntax for a two-
+ component principal where the first component matches the service
+ name specified in the application protocol's profile.
+
+
+
+Melnikov Standards Track [Page 5]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ When GSS_Accept_sec_context returns GSS_S_COMPLETE, the server
+ examines the context to ensure that it provides a level of protection
+ permitted by the server's security policy. In particular, if the
+ integ_avail flag is not set in the context, then no security layer
+ can be offered or accepted. If the conf_avail flag is not set in the
+ context, then no security layer with confidentiality can be offered
+ or accepted.
+
+ If the context is acceptable, the server takes the following actions:
+ If the last call to GSS_Accept_sec_context returned an output_token,
+ the server returns it to the client in a challenge and expects a
+ reply from the client with no data. Whether or not an output_token
+ was returned (and after receipt of any response from the client to
+ such an output_token), the server then constructs 4 octets of data,
+ with the first octet containing a bit-mask specifying the security
+ layers supported by the server and the second through fourth octets
+ containing in network byte order the maximum size output_token the
+ server is able to receive (which MUST be 0 if the server does not
+ support any security layer). The server must then pass the plaintext
+ to GSS_Wrap with conf_flag set to FALSE and issue the generated
+ output_message to the client in a challenge.
+
+ The server must then pass the resulting response to GSS_Unwrap and
+ interpret the first octet of resulting cleartext as the bit-mask for
+ the selected security layer, the second through fourth octets as the
+ maximum size output_message the client is able to receive (in network
+ byte order), and the remaining octets as the authorization identity.
+ The server verifies that the client has selected a security layer
+ that was offered and that the client maximum buffer is 0 if no
+ security layer was chosen. The server must verify that the src_name
+ is authorized to act as the authorization identity. After these
+ verifications, the authentication process is complete. The server is
+ not expected to return any additional data with the success
+ indicator.
+
+3.3. Security Layer
+
+ The security layers and their corresponding bit-masks are as follows:
+
+ 1 No security layer
+ 2 Integrity protection.
+ Sender calls GSS_Wrap with conf_flag set to FALSE
+ 4 Confidentiality protection.
+ Sender calls GSS_Wrap with conf_flag set to TRUE
+
+ Other bit-masks may be defined in the future; bits that are not
+ understood must be negotiated off.
+
+
+
+
+Melnikov Standards Track [Page 6]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ When decoding any received data with GSS_Unwrap, the major_status
+ other than the GSS_S_COMPLETE MUST be treated as a fatal error.
+
+ Note that SASL negotiates the maximum size of the output_message to
+ send. Implementations can use the GSS_Wrap_size_limit call to
+ determine the corresponding maximum size input_message.
+
+4. IANA Considerations
+
+ IANA modified the existing registration for "GSSAPI" as follows:
+
+ Family of SASL mechanisms: NO
+
+ SASL mechanism name: GSSAPI
+
+ Security considerations: See Section 5 of RFC 4752
+
+ Published specification: RFC 4752
+
+ Person & email address to contact for further information:
+ Alexey Melnikov <Alexey.Melnikov@isode.com>
+
+ Intended usage: COMMON
+
+ Owner/Change controller: iesg@ietf.org
+
+ Additional information: This mechanism is for the Kerberos V5
+ mechanism of GSS-API.
+
+5. Security Considerations
+
+ Security issues are discussed throughout this memo.
+
+ When constructing the input_name_string, the client SHOULD NOT
+ canonicalize the server's fully qualified domain name using an
+ insecure or untrusted directory service.
+
+ For compatibility with deployed software, this document requires that
+ the chan_binding (channel bindings) parameter to GSS_Init_sec_context
+ and GSS_Accept_sec_context be NULL, hence disallowing use of GSS-API
+ support for channel bindings. GSS-API channel bindings in SASL is
+ expected to be supported via a new GSS-API family of SASL mechanisms
+ (to be introduced in a future document).
+
+ Additional security considerations are in the [SASL] and [GSS-API]
+ specifications. Additional security considerations for the GSS-API
+ mechanism can be found in [KRB5GSS] and [KERBEROS].
+
+
+
+
+Melnikov Standards Track [Page 7]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+6. Acknowledgements
+
+ This document replaces Section 7.2 of RFC 2222 [RFC2222] by John G.
+ Myers. He also contributed significantly to this revision.
+
+ Lawrence Greenfield converted text of this document to the XML
+ format.
+
+ Contributions of many members of the SASL mailing list are gratefully
+ acknowledged, in particular comments from Chris Newman, Nicolas
+ Williams, Jeffrey Hutzelman, Sam Hartman, Mark Crispin, and Martin
+ Rex.
+
+7. Changes since RFC 2222
+
+ RFC 2078 [RFC2078] specifies the version of GSS-API used by RFC 2222
+ [RFC2222], which provided the original version of this specification.
+ That version of GSS-API did not provide the integ_integ_avail flag as
+ an input to GSS_Init_sec_context. Instead, integrity was always
+ requested. RFC 4422 [SASL] requires that when possible, the security
+ layer negotiation be integrity protected. To meet this requirement
+ and as part of moving from RFC 2078 [RFC2078] to RFC 2743 [GSS-API],
+ this specification requires that clients request integrity from
+ GSS_Init_sec_context so they can use GSS_Wrap to protect the security
+ layer negotiation. This specification does not require that the
+ mechanism offer the integrity security layer, simply that the
+ security layer negotiation be wrapped.
+
+8. References
+
+8.1. Normative References
+
+ [GSS-API] Linn, J., "Generic Security Service Application Program
+ Interface Version 2, Update 1", RFC 2743, January 2000.
+
+ [KERBEROS] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
+ Kerberos Network Authentication Service (V5)", RFC 4120,
+ July 2005.
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [KRB5GSS] Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC
+ 1964, June 1996.
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 8]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+ [RFC4121] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
+ Version 5 Generic Security Service Application Program
+ Interface (GSS-API) Mechanism: Version 2", RFC 4121, July
+ 2005.
+
+ [SASL] Melnikov, A. and K. Zeilenga, "Simple Authentication and
+ Security Layer (SASL)", RFC 4422, June 2006.
+
+ [UTF8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+8.2. Informative References
+
+ [RFC2078] Linn, J., "Generic Security Service Application Program
+ Interface, Version 2", RFC 2078, January 1997.
+
+ [RFC2222] Myers, J., "Simple Authentication and Security Layer
+ (SASL)", RFC 2222, October 1997.
+
+Editor's Address
+
+ Alexey Melnikov
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+ URI: http://www.melnikov.ca/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov Standards Track [Page 9]
+
+RFC 4752 SASL GSSAPI Mechanism November 2006
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2006).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST,
+ AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
+ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
+ THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
+ IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
+ PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+Melnikov Standards Track [Page 10]
+
diff --git a/imap/docs/rfc/rfc4790.txt b/imap/docs/rfc/rfc4790.txt
new file mode 100644
index 00000000..d58191c0
--- /dev/null
+++ b/imap/docs/rfc/rfc4790.txt
@@ -0,0 +1,1459 @@
+
+
+
+
+
+
+Network Working Group C. Newman
+Request for Comments: 4790 Sun Microsystems
+Category: Standards Track M. Duerst
+ Aoyama Gakuin University
+ A. Gulbrandsen
+ Oryx
+ March 2007
+
+
+ Internet Application Protocol Collation Registry
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2007).
+
+Abstract
+
+ Many Internet application protocols include string-based lookup,
+ searching, or sorting operations. However, the problem space for
+ searching and sorting international strings is large, not fully
+ explored, and is outside the area of expertise for the Internet
+ Engineering Task Force (IETF). Rather than attempt to solve such a
+ large problem, this specification creates an abstraction framework so
+ that application protocols can precisely identify a comparison
+ function, and the repertoire of comparison functions can be extended
+ in the future.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 1]
+
+RFC 4790 Collation Registry March 2007
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.1. Conventions Used in This Document . . . . . . . . . . . . 4
+ 2. Collation Definition and Purpose . . . . . . . . . . . . . . . 4
+ 2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.3. Some Other Terms Used in this Document . . . . . . . . . . 5
+ 2.4. Sort Keys . . . . . . . . . . . . . . . . . . . . . . . . 5
+ 3. Collation Identifier Syntax . . . . . . . . . . . . . . . . . 6
+ 3.1. Basic Syntax . . . . . . . . . . . . . . . . . . . . . . . 6
+ 3.2. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 6
+ 3.3. Ordering Direction . . . . . . . . . . . . . . . . . . . . 7
+ 3.4. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 3.5. Naming Guidelines . . . . . . . . . . . . . . . . . . . . 7
+ 4. Collation Specification Requirements . . . . . . . . . . . . . 8
+ 4.1. Collation/Server Interface . . . . . . . . . . . . . . . . 8
+ 4.2. Operations Supported . . . . . . . . . . . . . . . . . . . 8
+ 4.2.1. Validity . . . . . . . . . . . . . . . . . . . . . . . 9
+ 4.2.2. Equality . . . . . . . . . . . . . . . . . . . . . . . 9
+ 4.2.3. Substring . . . . . . . . . . . . . . . . . . . . . . 9
+ 4.2.4. Ordering . . . . . . . . . . . . . . . . . . . . . . . 10
+ 4.3. Sort Keys . . . . . . . . . . . . . . . . . . . . . . . . 10
+ 4.4. Use of Lookup Tables . . . . . . . . . . . . . . . . . . . 11
+ 5. Application Protocol Requirements . . . . . . . . . . . . . . 11
+ 5.1. Character Encoding . . . . . . . . . . . . . . . . . . . . 11
+ 5.2. Operations . . . . . . . . . . . . . . . . . . . . . . . . 11
+ 5.3. Wildcards . . . . . . . . . . . . . . . . . . . . . . . . 12
+ 5.4. String Comparison . . . . . . . . . . . . . . . . . . . . 12
+ 5.5. Disconnected Clients . . . . . . . . . . . . . . . . . . . 12
+ 5.6. Error Codes . . . . . . . . . . . . . . . . . . . . . . . 13
+ 5.7. Octet Collation . . . . . . . . . . . . . . . . . . . . . 13
+ 6. Use by Existing Protocols . . . . . . . . . . . . . . . . . . 13
+ 7. Collation Registration . . . . . . . . . . . . . . . . . . . . 14
+ 7.1. Collation Registration Procedure . . . . . . . . . . . . . 14
+ 7.2. Collation Registration Format . . . . . . . . . . . . . . 15
+ 7.2.1. Registration Template . . . . . . . . . . . . . . . . 15
+ 7.2.2. The Collation Element . . . . . . . . . . . . . . . . 15
+ 7.2.3. The Identifier Element . . . . . . . . . . . . . . . . 16
+ 7.2.4. The Title Element . . . . . . . . . . . . . . . . . . 16
+ 7.2.5. The Operations Element . . . . . . . . . . . . . . . . 16
+ 7.2.6. The Specification Element . . . . . . . . . . . . . . 16
+ 7.2.7. The Submitter Element . . . . . . . . . . . . . . . . 16
+ 7.2.8. The Owner Element . . . . . . . . . . . . . . . . . . 16
+ 7.2.9. The Version Element . . . . . . . . . . . . . . . . . 17
+ 7.2.10. The Variable Element . . . . . . . . . . . . . . . . . 17
+ 7.3. Structure of Collation Registry . . . . . . . . . . . . . 17
+ 7.4. Example Initial Registry Summary . . . . . . . . . . . . . 18
+
+
+
+Newman, et al. Standards Track [Page 2]
+
+RFC 4790 Collation Registry March 2007
+
+
+ 8. Guidelines for Expert Reviewer . . . . . . . . . . . . . . . . 18
+ 9. Initial Collations . . . . . . . . . . . . . . . . . . . . . . 19
+ 9.1. ASCII Numeric Collation . . . . . . . . . . . . . . . . . 20
+ 9.1.1. ASCII Numeric Collation Description . . . . . . . . . 20
+ 9.1.2. ASCII Numeric Collation Registration . . . . . . . . . 20
+ 9.2. ASCII Casemap Collation . . . . . . . . . . . . . . . . . 21
+ 9.2.1. ASCII Casemap Collation Description . . . . . . . . . 21
+ 9.2.2. ASCII Casemap Collation Registration . . . . . . . . . 22
+ 9.3. Octet Collation . . . . . . . . . . . . . . . . . . . . . 22
+ 9.3.1. Octet Collation Description . . . . . . . . . . . . . 22
+ 9.3.2. Octet Collation Registration . . . . . . . . . . . . . 23
+ 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
+ 11. Security Considerations . . . . . . . . . . . . . . . . . . . 23
+ 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
+ 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
+ 13.1. Normative References . . . . . . . . . . . . . . . . . . . 24
+ 13.2. Informative References . . . . . . . . . . . . . . . . . . 24
+
+
+
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+
+Newman, et al. Standards Track [Page 3]
+
+RFC 4790 Collation Registry March 2007
+
+
+1. Introduction
+
+ The Application Configuration Access Protocol ACAP [11] specification
+ introduced the concept of a comparator (which we call collation in
+ this document), but failed to create an IANA registry. With the
+ introduction of stringprep [6] and the Unicode Collation Algorithm
+ [7], it is now time to create that registry and populate it with some
+ initial values appropriate for an international community. This
+ specification replaces and generalizes the definition of a comparator
+ in ACAP, and creates a collation registry.
+
+1.1. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
+ in this document are to be interpreted as defined in "Key words for
+ use in RFCs to Indicate Requirement Levels" [1].
+
+ The attribute syntax specifications use the Augmented Backus-Naur
+ Form (ABNF) [2] notation, including the core rules defined in
+ Appendix A. The ABNF production "Language-tag" is imported from
+ Language Tags [5] and "reg-name" from URI: Generic Syntax [4].
+
+2. Collation Definition and Purpose
+
+2.1. Definition
+
+ A collation is a named function which takes two arbitrary length
+ strings as input and can be used to perform one or more of three
+ basic comparison operations: equality test, substring match, and
+ ordering test.
+
+2.2. Purpose
+
+ Collations are an abstraction for comparison functions so that these
+ comparison functions can be used in multiple protocols. The details
+ of a particular comparison operation can be specified by someone with
+ appropriate expertise, independent of the application protocols that
+ use that collation. This is similar to the way a charset [13]
+ separates the details of octet to character mapping from a protocol
+ specification, such as MIME [9], or the way SASL [10] separates the
+ details of an authentication mechanism from a protocol specification,
+ such as ACAP [11].
+
+
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 4]
+
+RFC 4790 Collation Registry March 2007
+
+
+ Here is a small diagram to help illustrate the value of this
+ abstraction:
+
+ +-------------------+ +-----------------+
+ | IMAP i18n SEARCH |--+ | Basic |
+ +-------------------+ | +--| Collation Spec |
+ | | +-----------------+
+ +-------------------+ | +-------------+ | +-----------------+
+ | ACAP i18n SEARCH |--+--| Collation |--+--| A stringprep |
+ +-------------------+ | | Registry | | | Collation Spec |
+ | +-------------+ | +-----------------+
+ +-------------------+ | | +-----------------+
+ | ...other protocol |--+ | | locale-specific |
+ +-------------------+ +--| Collation Spec |
+ +-----------------+
+
+ Thus IMAP, ACAP, and future application protocols with international
+ search capability simply specify how to interface to the collation
+ registry instead of each protocol specification having to specify all
+ the collations it supports.
+
+2.3. Some Other Terms Used in this Document
+
+ The terms client, server, and protocol are used in somewhat unusual
+ senses.
+
+ Client means a user, or a program acting directly on behalf of a
+ user. This may be a mail reader acting as an IMAP client, or it may
+ be an interactive shell, where the user can type protocol commands/
+ requests directly, or it may be a script or program written by the
+ user.
+
+ Server means a program that performs services requested by the
+ client. This may be a traditional server such as an HTTP server, or
+ it may be a Sieve [14] interpreter running a Sieve script written by
+ a user. A server needs to use the operations provided by collations
+ in order to fulfill the client's requests.
+
+ The protocol describes how the client tells the server what it wants
+ done, and (if applicable) how the server tells the client about the
+ results. IMAP is a protocol by this definition, and so is the Sieve
+ language.
+
+2.4. Sort Keys
+
+ One component of a collation is a transformation, which turns a
+ string into a sort key, which is then used while sorting.
+
+
+
+
+Newman, et al. Standards Track [Page 5]
+
+RFC 4790 Collation Registry March 2007
+
+
+ The transformation can range from an identity mapping (e.g., the
+ i;octet collation Section 9.3) to a mapping that makes the string
+ unreadable to a human.
+
+ This is an implementation detail of collations or servers. A
+ protocol SHOULD NOT expose it to clients, since some collations leave
+ the sort key's format up to the implementation, and current
+ conformant implementations are known to use different formats.
+
+3. Collation Identifier Syntax
+
+3.1. Basic Syntax
+
+ The collation identifier itself is a single US-ASCII string. The
+ identifier MUST NOT be longer than 254 characters, and obeys the
+ following grammar:
+
+ collation-char = ALPHA / DIGIT / "-" / ";" / "=" / "."
+
+ collation-id = collation-prefix ";" collation-core-name
+ *collation-arg
+
+ collation-scope = Language-tag / "vnd-" reg-name
+
+ collation-core-name = ALPHA *( ALPHA / DIGIT / "-" )
+
+ collation-arg = ";" ALPHA *( ALPHA / DIGIT ) "="
+ 1*( ALPHA / DIGIT / "." )
+
+
+ Note: the ABNF production "Language-tag" is imported from Language
+ Tags [5] and "reg-name" from URI: Generic Syntax [4].
+
+ There is a special identifier called "default". For protocols that
+ have a default collation, "default" refers to that collation. For
+ other protocols, the identifier "default" MUST match no collations,
+ and servers SHOULD treat it in the same way as they treat nonexistent
+ collations.
+
+3.2. Wildcards
+
+ The string a client uses to select a collation MAY contain one or
+ more wildcard ("*") characters that match zero or more collation-
+ chars. Wildcard characters MUST NOT be adjacent. If the wildcard
+ string matches multiple collations, the server SHOULD attempt to
+ select a widely useful collation in preference to a narrowly useful
+ one.
+
+
+
+
+Newman, et al. Standards Track [Page 6]
+
+RFC 4790 Collation Registry March 2007
+
+
+ collation-wild = ("*" / (ALPHA ["*"])) *(collation-char ["*"])
+ ; MUST NOT exceed 254 characters total
+
+3.3. Ordering Direction
+
+ When used as a protocol element for ordering, the collation
+ identifier MAY be prefixed by either "+" or "-" to explicitly specify
+ an ordering direction. "+" has no effect on the ordering operation,
+ while "-" inverts the result of the ordering operation. In general,
+ collation-order is used when a client requests a collation, and
+ collation-selected is used when the server informs the client of the
+ selected collation.
+
+ collation-selected = ["+" / "-"] collation-id
+
+ collation-order = ["+" / "-"] collation-wild
+
+3.4. URIs
+
+ Some protocols are designed to use URIs [4] to refer to collations
+ rather than simple tokens. A special section of the IANA URL space
+ is reserved for such usage. The "collation-uri" form is used to
+ refer to a specific named collation (the collation registration may
+ not actually be present). The "collation-auri" form is an abstract
+ name for an ordering, a collation pattern or a vendor private
+ collator.
+
+ collation-uri = "http://www.iana.org/assignments/collation/"
+ collation-id ".xml"
+
+ collation-auri = ( "http://www.iana.org/assignments/collation/"
+ collation-order ".xml" ) / other-uri
+
+ other-uri = <absoluteURI>
+ ; excluding the IANA collation namespace.
+
+3.5. Naming Guidelines
+
+ While this specification makes no absolute requirements on the
+ structure of collation identifiers, naming consistency is important,
+ so the following initial guidelines are provided.
+
+ Collation identifiers with an international audience typically begin
+ with "i;". Collation identifiers intended for a particular language
+ or locale typically begin with a language tag [5] followed by a ";".
+ After the first ";" is normally the name of the general collation
+ algorithm, followed by a series of algorithm modifications separated
+ by the ";" delimiter. Parameterized modifications will use "=" to
+
+
+
+Newman, et al. Standards Track [Page 7]
+
+RFC 4790 Collation Registry March 2007
+
+
+ delimit the parameter from the value. The version numbers of any
+ lookup tables used by the algorithm SHOULD be present as
+ parameterized modifications.
+
+ Collation identifiers of the form *;vnd-hostname;* are reserved for
+ vendor-specific collations created by the owner of the hostname
+ following the "vnd-" prefix (e.g., vnd-example.com for the vendor
+ example.com). Registration of such collations (or the name space as
+ a whole), with intended use of the "Vendor", is encouraged when a
+ public specification or open-source implementation is available, but
+ is not required.
+
+4. Collation Specification Requirements
+
+4.1. Collation/Server Interface
+
+ The collation itself defines what it operates on. Most collations
+ are expected to operate on character strings. The i;octet
+ (Section 9.3) collation operates on octet strings. The i;ascii-
+ numeric (Section 9.1) operation operates on numbers.
+
+ This specification defines the collation interface in terms of octet
+ strings. However, implementations may choose to use character
+ strings instead. Such implementations may not be able to implement
+ e.g., i;octet. Since i;octet is not currently mandatory to implement
+ for any protocol, this should not be a problem.
+
+4.2. Operations Supported
+
+ A collation specification MUST state which of the three basic
+ operations are supported (equality, substring, ordering) and how to
+ perform each of the supported operations on any two input character
+ strings, including empty strings. Collations must be deterministic,
+ i.e., given a collation with a specific identifier, and any two fixed
+ input strings, the result MUST be the same for the same operation.
+
+ In general, collation operations should behave as their names
+ suggest. While a collation may be new, the operations are not, so
+ the new collation's operations should be similar to those of older
+ collations. For example, a date/time collation should not provide a
+ "substring" operation that would morph IMAP substring SEARCH into
+ e.g., a date-range search.
+
+ A non-obvious consequence of the rules for each collation operation
+ is that, for any single collation, either none or all of the
+ operations can return "undefined". For example, it is not possible
+ to have an equality operation that never returns "undefined", and a
+ substring operation that occasionally does.
+
+
+
+Newman, et al. Standards Track [Page 8]
+
+RFC 4790 Collation Registry March 2007
+
+
+4.2.1. Validity
+
+ The validity test takes one string as argument. It returns valid if
+ its input string is a valid input to the collation's other
+ operations, and invalid if not. (In other words, a string is valid
+ if it is equal to itself according to the collation's equality
+ operation.)
+
+ The validity test is provided by all collations. It MUST NOT be
+ listed separately in the collation registration.
+
+4.2.2. Equality
+
+ The equality test always returns "match" or "no-match" when it is
+ supplied valid input, and MAY return "undefined" if one or both input
+ strings are not valid.
+
+ The equality test MUST be reflexive and symmetric. For valid input,
+ it MUST be transitive.
+
+ If a collation provides either a substring or an ordering test, it
+ MUST also provide an equality test. The substring and/or ordering
+ tests MUST be consistent with the equality test.
+
+ The return values of the equality test are called "match", "no-match"
+ and "undefined" in this document.
+
+4.2.3. Substring
+
+ The substring matching operation determines if the first string is a
+ substring of the second string, i.e., if one or more substrings of
+ the second string is equal to the first, as defined by the
+ collation's equality operation.
+
+ A collation that supports substring matching will automatically
+ support two special cases of substring matching: prefix and suffix
+ matching, if those special cases are supported by the application
+ protocol. It returns "match" or "no-match" when it is supplied valid
+ input and returns "undefined" when supplied invalid input.
+
+ Application protocols MAY return position information for substring
+ matches. If this is done, the position information SHOULD include
+ both the starting offset and the ending offset for each match. This
+ is important because more sophisticated collations can match strings
+ of unequal length (for example, a pre-composed accented character can
+ match a decomposed accented character). In general, overlapping
+ matches SHOULD be reported (as when "ana" occurs twice within
+ "banana"), although there are cases where a collation may decide not
+
+
+
+Newman, et al. Standards Track [Page 9]
+
+RFC 4790 Collation Registry March 2007
+
+
+ to. For example, in a collation which treats all whitespace
+ sequences as identical, the substring operation could be defined such
+ that " 1 " (SP "1" SP) is reported just once within " 1 " (SP SP
+ "1" SP SP), not four times (SP SP "1" SP, SP "1" SP, SP "1" SP SP and
+ SP SP "1" SP SP), since the four matches are, in a sense, the same
+ match.
+
+ A string is a substring of itself. The empty string is a substring
+ of all strings.
+
+ Note that the substring operation of some collations can match
+ strings of unequal length. For example, a pre-composed accented
+ character can match a decomposed accented character. The Unicode
+ Collation Algorithm [7] discusses this in more detail.
+
+ The return values of the substring operation are called "match", "no-
+ match", and "undefined" in this document.
+
+4.2.4. Ordering
+
+ The ordering operation determines how two strings are ordered. It
+ MUST be reflexive. For valid input, it MUST be transitive and
+ trichotomous.
+
+ Ordering returns "less" if the first string is listed before the
+ second string, according to the collation; "greater", if the second
+ string is listed before the first string; and "equal", if the two
+ strings are equal, as defined by the collation's equality operation.
+ If one or both strings are invalid, the result of ordering is
+ "undefined".
+
+ When the collation is used with a "+" prefix, the behavior is the
+ same as when used with no prefix. When the collation is used with a
+ "-" prefix, the result of the ordering operation of the collation
+ MUST be reversed.
+
+ The return values of the ordering operation are called "less",
+ "equal", "greater", and "undefined" in this document.
+
+4.3. Sort Keys
+
+ A collation specification SHOULD describe the internal transformation
+ algorithm to generate sort keys. This algorithm can be applied to
+ individual strings, and the result can be stored to potentially
+ optimize future comparison operations. A collation MAY specify that
+ the sort key is generated by the identity function. The sort key may
+ have no meaning to a human. The sort key may not be valid input to
+ the collation.
+
+
+
+Newman, et al. Standards Track [Page 10]
+
+RFC 4790 Collation Registry March 2007
+
+
+4.4. Use of Lookup Tables
+
+ Some collations use customizable lookup tables, e.g., because the
+ tables depend on locale, and may be modified after shipping the
+ software. Collations that use more than one customizable lookup
+ table in a documented format MUST assign numbers to the tables they
+ use. This permits an application protocol command to access the
+ tables used by a server collation, so that clients and servers use
+ the same tables.
+
+5. Application Protocol Requirements
+
+ This section describes the requirements and issues that an
+ application protocol needs to consider if it offers searching,
+ substring matching and/or sorting, and permits the use of characters
+ outside the US-ASCII charset.
+
+5.1. Character Encoding
+
+ The protocol specification has to make sure that it is clear on which
+ characters (rather than just octets) the collations are used. This
+ can be done by specifying the protocol itself in terms of characters
+ (e.g., in the case of a query language), by specifying a single
+ character encoding for the protocol (e.g., UTF-8 [3]), or by
+ carefully describing the relevant issues of character encoding
+ labeling and conversion. In the later case, details to consider
+ include how to handle unknown charsets, any charsets that are
+ mandatory-to-implement, any issues with byte-order that might apply,
+ and any transfer encodings that need to be supported.
+
+5.2. Operations
+
+ The protocol must specify which of the operations defined in this
+ specification (equality matching, substring matching, and ordering)
+ can be invoked in the protocol, and how they are invoked. There may
+ be more than one way to invoke an operation.
+
+ The protocol MUST provide a mechanism for the client to select the
+ collation to use with equality matching, substring matching, and
+ ordering.
+
+ If a protocol needs a total ordering and the collation chosen does
+ not provide it because the ordering operation returns "undefined" at
+ least once, the recommended fallback is to sort all invalid strings
+ after the valid ones, and use i;octet to order the invalid strings.
+
+ Although the collation's substring function provides a list of
+ matches, a protocol need not provide all that to the client. It may
+
+
+
+Newman, et al. Standards Track [Page 11]
+
+RFC 4790 Collation Registry March 2007
+
+
+ provide only the first matching substring, or even just the
+ information that the substring search matched. In this way,
+ collations can be used with protocols that are defined such that "x
+ is a substring of y" returns true-false.
+
+ If the protocol provides positional information for the results of a
+ substring match, that positional information SHOULD fully specify the
+ substring(s) in the result that matches, independent of the length of
+ the search string. For example, returning both the starting and
+ ending offset of the match would suffice, as would the starting
+ offset and a length. Returning just the starting offset is not
+ acceptable. This rule is necessary because advanced collations can
+ treat strings of different lengths as equal (for example, pre-
+ composed and decomposed accented characters).
+
+5.3. Wildcards
+
+ The protocol MUST specify whether it allows the use of wildcards in
+ collation identifiers. If the protocol allows wildcards, then:
+ The protocol MUST specify how comparisons behave in the absence of
+ explicit collation negotiation, or when a collation of "default"
+ is requested. The protocol MAY specify that the default collation
+ used in such circumstances is sensitive to server configuration.
+
+ The protocol SHOULD provide a way to list available collations
+ matching a given wildcard pattern, or patterns.
+
+5.4. String Comparison
+
+ If a protocol compares strings in any nontrivial way, using a
+ collation may be appropriate. As an example, many protocols use
+ case-independent strings. In many cases, a simple ASCII mapping to
+ upper/lower case works well. In other cases, it may be better to use
+ a specifiable collation; for example, so that a server can treat "i"
+ and "I" as equivalent in Italy, and different in Turkey (Turkish also
+ has a dotted upper-case" I" and a dotless lower-case "i").
+
+ Protocol designers should consider, in each case, whether to use a
+ specifiable collation. Keywords often have other needs than user
+ variables, and search arguments may be different again.
+
+5.5. Disconnected Clients
+
+ If the protocol supports disconnected clients, and a collation is
+ used that can use configurable tables (e.g., to support
+ locale-specific extensions), then the client may not be able to
+ reproduce the server's collation operations while offline.
+
+
+
+
+Newman, et al. Standards Track [Page 12]
+
+RFC 4790 Collation Registry March 2007
+
+
+ A mechanism to download such tables has been discussed. Such a
+ mechanism is not included in the present specification, since the
+ problem is not yet well understood.
+
+5.6. Error Codes
+
+ The protocol specification should consider assigning protocol error
+ codes for the following circumstances:
+
+ o The client requests the use of a collation by identifier or
+ pattern, but no implemented collation matches that pattern.
+
+ o The client attempts to use a collation for an operation that is
+ not supported by that collation -- for example, attempting to use
+ the "i;ascii-numeric" collation for substring matching.
+
+ o The client uses an equality or substring matching collation, and
+ the result is an error. It may be appropriate to distinguish
+ between the two input strings, particularly when one is supplied
+ by the client and the other is stored by the server. It might
+ also be appropriate to distinguish the specific case of an invalid
+ UTF-8 string.
+
+5.7. Octet Collation
+
+ The i;octet (Section 9.3) collation is only usable with protocols
+ based on octet-strings. Clients and servers MUST NOT use i;octet
+ with other protocols.
+
+ If the protocol permits the use of collations with data structures
+ other than strings, the protocol MUST describe the default behavior
+ for a collation with those data structures.
+
+6. Use by Existing Protocols
+
+ This section is informative.
+
+ Both ACAP [11] and Sieve [14] are standards track specifications that
+ used collations prior to the creation of this specification and
+ registry. Those standards do not meet all the application protocol
+ requirements described in Section 5.
+
+ These protocols allow the use of the i;octet (Section 9.3) collation
+ working directly on UTF-8 data, as used in these protocols.
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 13]
+
+RFC 4790 Collation Registry March 2007
+
+
+ In Sieve, all matches are either true or false. Accordingly, Sieve
+ servers must treat "undefined" and "no-match" results of the equality
+ and substring operations as false, and only "match" as true.
+
+ In ACAP and Sieve, there are no invalid strings. In this document's
+ terms, invalid strings sort after valid strings.
+
+ IMAP [15] also collates, although that is explicit only when the
+ COMPARATOR [17] extension is used. The built-in IMAP substring
+ operation and the ordering provided by the SORT [16] extension may
+ not meet the requirements made in this document.
+
+ Other protocols may be in a similar position.
+
+ In IMAP, the default collation is i;ascii-casemap, because its
+ operations are understood to match IMAP's built-in operations.
+
+7. Collation Registration
+
+7.1. Collation Registration Procedure
+
+ The IETF will create a mailing list, collation@ietf.org, which can be
+ used for public discussion of collation proposals prior to
+ registration. Use of the mailing list is strongly encouraged. The
+ IESG will appoint a designated expert who will monitor the
+ collation@ietf.org mailing list and review registrations.
+
+ The registration procedure begins when a completed registration
+ template is sent to iana@iana.org and collation@ietf.org. The
+ designated expert is expected to tell IANA and the submitter of the
+ registration within two weeks whether the registration is approved,
+ approved with minor changes, or rejected with cause. When a
+ registration is rejected with cause, it can be re-submitted if the
+ concerns listed in the cause are addressed. Decisions made by the
+ designated expert can be appealed to the IESG Applications Area
+ Director, then to the IESG. They follow the normal appeals procedure
+ for IESG decisions.
+
+ Collation registrations in a standards track, BCP, or IESG-approved
+ experimental RFC are owned by the IETF, and changes to the
+ registration follow normal procedures for updating such documents.
+ Collation registrations in other RFCs are owned by the RFC author(s).
+ Other collation registrations are owned by the individual(s) listed
+ in the contact field of the registration, and IANA will preserve this
+ information.
+
+ If the registration is a change of an existing collation, it MUST be
+ approved by the owner. In the event the owner cannot be contacted
+
+
+
+Newman, et al. Standards Track [Page 14]
+
+RFC 4790 Collation Registry March 2007
+
+
+ for a period of one month, and the designated expert deems the change
+ necessary, the IESG MAY re-assign ownership to an appropriate party.
+
+7.2. Collation Registration Format
+
+ Registration of a collation is done by sending a well-formed XML
+ document to collation@ietf.org and iana@iana.org.
+
+7.2.1. Registration Template
+
+ Here is a template for the registration:
+
+ <?xml version='1.0'?>
+ <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+ <collation rfc="YYYY" scope="global" intendedUse="common">
+ <identifier>collation identifier</identifier>
+ <title>technical title for collation</title>
+ <operations>equality order substring</operations>
+ <specification>specification reference</specification>
+ <owner>email address of owner or IETF</owner>
+ <submitter>email address of submitter</submitter>
+ <version>1</version>
+ </collation>
+
+7.2.2. The Collation Element
+
+ The root of the registration document MUST be a <collation> element.
+ The collation element contains the other elements in the
+ registration, which are described in the following sub-subsections,
+ in the order given here.
+
+ The <collation> element MAY include an "rfc=" attribute if the
+ specification is in an RFC. The "rfc=" attribute gives only the
+ number of the RFC, without any prefix, such as "RFC", or suffix, such
+ as ".txt".
+
+ The <collation> element MUST include a "scope=" attribute, which MUST
+ have one of the values "global", "local", or "other".
+
+ The <collation> element MUST include an "intendedUse=" attribute,
+ which must have one of the values "common", "limited", "vendor", or
+ "deprecated". Collation specifications intended for "common" use are
+ expected to reference standards from standards bodies with
+ significant experience dealing with the details of international
+ character sets.
+
+ Be aware that future revisions of this specification may add
+ additional function types, as well as additional XML attributes,
+
+
+
+Newman, et al. Standards Track [Page 15]
+
+RFC 4790 Collation Registry March 2007
+
+
+ values, and elements. Any system that automatically parses these XML
+ documents MUST take this into account to preserve future
+ compatibility.
+
+7.2.3. The Identifier Element
+
+ The <identifier> element gives the precise identifier of the
+ collation, e.g., i;ascii-casemap. The <identifier> element is
+ mandatory.
+
+7.2.4. The Title Element
+
+ The <title> element gives the title of the collation. The <title>
+ element is mandatory.
+
+7.2.5. The Operations Element
+
+ The <operations> element lists which of the three operations
+ ("equality", "order" or "substring") the collation provides,
+ separated by single spaces. The <operations> element is mandatory.
+
+7.2.6. The Specification Element
+
+ The <specification> element describes where to find the
+ specification. The <specification> element is mandatory. It MAY
+ have a URI attribute. There may be more than one <specification>
+ element, in which case, they together form the specification.
+
+ If it is discovered that parts of a collation specification conflict,
+ a new revision of the collation is necessary, and the
+ collation@ietf.org mailing list should be notified.
+
+7.2.7. The Submitter Element
+
+ The <submitter> element provides an RFC 2822 [12] email address for
+ the person who submitted the registration. It is optional if the
+ <owner> element contains an email address.
+
+ There may be more than one <submitter> element.
+
+7.2.8. The Owner Element
+
+ The <owner> element contains either the four letters "IETF" or an
+ email address of the owner of the registration. The <owner> element
+ is mandatory. There may be more than one <owner> element. If so,
+ all owners are equal. Each owner can speak for all.
+
+
+
+
+
+Newman, et al. Standards Track [Page 16]
+
+RFC 4790 Collation Registry March 2007
+
+
+7.2.9. The Version Element
+
+ The <version> element MUST be included when the registration is
+ likely to be revised, or has been revised in such a way that the
+ results change for one or more input strings. The <version> element
+ is optional.
+
+7.2.10. The Variable Element
+
+ The <variable> element specifies an optional variable to control the
+ collation's behaviour, for example whether it is case sensitive. The
+ <variable> element is optional. When <variable> is used, it must
+ contain <name> and <default> elements, and it may contain one or more
+ <value> elements.
+
+7.2.10.1. The Name Element
+
+ The <name> element specifies the name value of a variable. The
+ <name> element is mandatory.
+
+7.2.10.2. The Default Element
+
+ The <default> element specifies the default value of a variable. The
+ <default> element is mandatory.
+
+7.2.10.3. The Value Element
+
+ The <value> element specifies a legal value of a variable. The
+ <value> element is optional. If one or more <value> elements are
+ present, only those values are legal. If none are, then the
+ variable's legal values do not form an enumerated set, and the rules
+ MUST be specified in an RFC accompanying the registration.
+
+7.3. Structure of Collation Registry
+
+ Once the registration is approved, IANA will store each XML
+ registration document in a URL of the form
+ http://www.iana.org/assignments/collation/collation-id.xml, where
+ collation-id is the content of the identifier element in the
+ registration. Both the submitter and the designated expert are
+ responsible for verifying that the XML is well-formed. The
+ registration document should avoid using new elements. If any are
+ necessary, it is important to be consistent with other registrations.
+
+ IANA will also maintain a text summary of the registry under the name
+ http://www.iana.org/assignments/collation/collation-index.html. This
+ summary is divided into four sections. The first section is for
+ collations intended for common use. This section is intended for
+
+
+
+Newman, et al. Standards Track [Page 17]
+
+RFC 4790 Collation Registry March 2007
+
+
+ collation registrations published in IESG-approved RFCs, or for
+ locally scoped collations from the primary standards body for that
+ locale. The designated expert is encouraged to reject collation
+ registrations with an intended use of "common" if the expert believes
+ it should be "limited", as it is desirable to keep the number of
+ "common" registrations small and of high quality. The second section
+ is reserved for limited-use collations. The third section is
+ reserved for registered vendor-specific collations. The final
+ section is reserved for deprecated collations.
+
+7.4. Example Initial Registry Summary
+
+ The following is an example of how IANA might structure the initial
+ registry summary.html file:
+
+ Collation Functions Scope Reference
+ --------- --------- ----- ---------
+ Common Use Collations:
+ i;ascii-casemap e, o, s Local [RFC 4790]
+
+ Limited Use Collations:
+ i;octet e, o, s Other [RFC 4790]
+ i;ascii-numeric e, o Other [RFC 4790]
+
+ Vendor Collations:
+
+ Deprecated Collations:
+
+
+ References
+ ----------
+ [RFC 4790] Newman, C., Duerst, M., Gulbrandsen, A., "Internet
+ Application Protocol Collation Registry", RFC 4790,
+ Sun Microsystems, March 2007.
+
+8. Guidelines for Expert Reviewer
+
+ The expert reviewer appointed by the IESG has fairly broad latitude
+ for this registry. While a number of collations are expected
+ (particularly customizations of the UCA for localized use), an
+ explosion of collations (particularly common-use collations) is not
+ desirable for widespread interoperability. However, it is important
+ for the expert reviewer to provide cause when rejecting a
+ registration, and, when possible, to describe corrective action to
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 18]
+
+RFC 4790 Collation Registry March 2007
+
+
+ permit the registration to proceed. The following table includes
+ some example reasons to reject a registration with cause:
+
+ o The registration is not a well-formed XML document.
+
+ o The registration has an intended use of "common", but there is no
+ evidence the collation will be widely deployed, so it should be
+ listed as "limited".
+
+ o The registration has an intended use of "common", but it is
+ redundant with the functionality of a previously registered
+ "common" collation.
+
+ o The registration has an intended use of "common", but the
+ specification is not detailed enough to allow interoperable
+ implementations by others.
+
+ o The collation identifier fails to precisely identify the version
+ numbers of relevant tables to use.
+
+ o The registration fails to meet one of the "MUST" requirements in
+ Section 4.
+
+ o The collation identifier fails to meet the syntax in Section 3.
+
+ o The collation specification referenced in the registration is
+ vague or has optional features without a clear behavior specified.
+
+ o The referenced specification does not adequately address security
+ considerations specific to that collation.
+
+ o The registration's operations are needlessly different from those
+ of traditional operations.
+
+ o The registration's XML is needlessly different from that of
+ already registered collations.
+
+9. Initial Collations
+
+ This section registers the three collations that were originally
+ defined in [11], and are implemented in most [14] engines. Some of
+ the behavior of these collations is perhaps not ideal, such as
+ i;ascii-casemap accepting non-ASCII input. Compatibility with widely
+ deployed code was judged more important than fixing the collations.
+ Some of the aspects of these collations are necessary to maintain
+ compatibility with widely deployed code.
+
+
+
+
+
+Newman, et al. Standards Track [Page 19]
+
+RFC 4790 Collation Registry March 2007
+
+
+9.1. ASCII Numeric Collation
+
+9.1.1. ASCII Numeric Collation Description
+
+ The "i;ascii-numeric" collation is a simple collation intended for
+ use with arbitrarily-sized, unsigned decimal integer numbers stored
+ as octet strings. US-ASCII digits (0x30 to 0x39) represent digits of
+ the numbers. Before converting from string to integer, the input
+ string is truncated at the first non-digit character. All input is
+ valid; strings that do not start with a digit represent positive
+ infinity.
+
+ The collation supports equality and ordering, but does not support
+ the substring operation.
+
+ The equality operation returns "match" if the two strings represent
+ the same number (i.e., leading zeroes and trailing non-digits are
+ disregarded), and "no-match" if the two strings represent different
+ numbers.
+
+ The ordering operation returns "less" if the first string represents
+ a smaller number than the second, "equal" if they represent the same
+ number, and "greater" if the first string represents a larger number
+ than the second.
+
+ Some examples: "0" is less than "1", and "1" is less than
+ "4294967298". "4294967298", "04294967298", and "4294967298b" are all
+ equal. "04294967298" is less than "". "", "x", and "y" are equal.
+
+9.1.2. ASCII Numeric Collation Registration
+
+ <?xml version='1.0'?>
+ <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+ <collation rfc="4790" scope="other" intendedUse="limited">
+ <identifier>i;ascii-numeric</identifier>
+ <title>ASCII Numeric</title>
+ <operations>equality order</operations>
+ <specification>RFC 4790</specification>
+ <owner>IETF</owner>
+ <submitter>chris.newman@sun.com</submitter>
+ </collation>
+
+
+
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 20]
+
+RFC 4790 Collation Registry March 2007
+
+
+9.2. ASCII Casemap Collation
+
+9.2.1. ASCII Casemap Collation Description
+
+ The "i;ascii-casemap" collation is a simple collation that operates
+ on octet strings and treats US-ASCII letters case-insensitively. It
+ provides equality, substring, and ordering operations. All input is
+ valid. Note that letters outside ASCII are not treated case-
+ insensitively.
+
+ Its equality, ordering, and substring operations are as for i;octet,
+ except that at first, the lower-case letters (octet values 97-122) in
+ each input string are changed to upper case (octet values 65-90).
+
+ Care should be taken when using OS-supplied functions to implement
+ this collation, as it is not locale sensitive. Functions, such as
+ strcasecmp and toupper, are sometimes locale sensitive, and may
+ inappropriately map lower-case letters other than a-z to upper case.
+
+ The i;ascii-casemap collation is well-suited for use with many
+ Internet protocols and computer languages. Use with natural language
+ is often inappropriate; even though the collation apparently supports
+ languages such as Swahili and English, in real-world use, it tends to
+ mis-sort a number of types of string:
+
+ o people and place names containing non-ASCII,
+
+ o words such as "naive" (if spelled with an accent, the accented
+ character could push the word to the wrong spot in a sorted list),
+
+ o names such as "Lloyd" (which, in Welsh, sorts after "Lyon", unlike
+ in English),
+
+ o strings containing euro and pound sterling symbols, quotation
+ marks other than '"', dashes/hyphens, etc.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 21]
+
+RFC 4790 Collation Registry March 2007
+
+
+9.2.2. ASCII Casemap Collation Registration
+
+ <?xml version='1.0'?>
+ <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+ <collation rfc="4790" scope="local" intendedUse="common">
+ <identifier>i;ascii-casemap</identifier>
+ <title>ASCII Casemap</title>
+ <operations>equality order substring</operations>
+ <specification>RFC 4790</specification>
+ <owner>IETF</owner>
+ <submitter>chris.newman@sun.com</submitter>
+ </collation>
+
+9.3. Octet Collation
+
+9.3.1. Octet Collation Description
+
+ The "i;octet" collation is a simple and fast collation intended for
+ use on binary octet strings rather than on character data. Protocols
+ that want to make this collation available have to do so by
+ explicitly allowing it. If not explicitly allowed, it MUST NOT be
+ used. It never returns an "undefined" result. It provides equality,
+ substring, and ordering operations.
+
+ The ordering algorithm is as follows:
+
+ 1. If both strings are the empty string, return the result "equal".
+
+ 2. If the first string is empty and the second is not, return the
+ result "less".
+
+ 3. If the second string is empty and the first is not, return the
+ result "greater".
+
+ 4. If both strings begin with the same octet value, remove the first
+ octet from both strings and repeat this algorithm from step 1.
+
+ 5. If the unsigned value (0 to 255) of the first octet of the first
+ string is less than the unsigned value of the first octet of the
+ second string, then return "less".
+
+ 6. If this step is reached, return "greater".
+
+ This algorithm is roughly equivalent to the C library function
+ memcmp, with appropriate length checks added.
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 22]
+
+RFC 4790 Collation Registry March 2007
+
+
+ The matching operation returns "match" if the sorting algorithm would
+ return "equal". Otherwise, the matching operation returns "no-
+ match".
+
+ The substring operation returns "match" if the first string is the
+ empty string, or if there exists a substring of the second string of
+ length equal to the length of the first string, which would result in
+ a "match" result from the equality function. Otherwise, the
+ substring operation returns "no-match".
+
+9.3.2. Octet Collation Registration
+
+ This collation is defined with intendedUse="limited" because it can
+ only be used by protocols that explicitly allow it.
+
+ <?xml version='1.0'?>
+ <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+ <collation rfc="4790" scope="global" intendedUse="limited">
+ <identifier>i;octet</identifier>
+ <title>Octet</title>
+ <operations>equality order substring</operations>
+ <specification>RFC 4790</specification>
+ <owner>IETF</owner>
+ <submitter>chris.newman@sun.com</submitter>
+ </collation>
+
+10. IANA Considerations
+
+ Section 7 defines how to register collations with IANA. Section 9
+ defines a list of predefined collations that have been registered
+ with IANA.
+
+11. Security Considerations
+
+ Collations will normally be used with UTF-8 strings. Thus, the
+ security considerations for UTF-8 [3], stringprep [6], and Unicode
+ TR-36 [8] also apply, and are normative to this specification.
+
+12. Acknowledgements
+
+ The authors want to thank all who have contributed to this document,
+ including Brian Carpenter, John Cowan, Dave Cridland, Mark Davis,
+ Spencer Dawkins, Lisa Dusseault, Lars Eggert, Frank Ellermann, Philip
+ Guenther, Tony Hansen, Ted Hardie, Sam Hartman, Kjetil Torgrim Homme,
+ Michael Kay, John Klensin, Alexey Melnikov, Jim Melton, and Abhijit
+ Menon-Sen.
+
+
+
+
+
+Newman, et al. Standards Track [Page 23]
+
+RFC 4790 Collation Registry March 2007
+
+
+13. References
+
+13.1. Normative References
+
+ [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
+ Levels", BCP 14, RFC 2119, March 1997.
+
+ [2] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [3] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
+ STD 63, RFC 3629, November 2003.
+
+ [4] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+ Resource Identifier (URI): Generic Syntax", RFC 3986,
+ January 2005.
+
+ [5] Phillips, A. and M. Davis, "Tags for Identifying Languages",
+ BCP 47, RFC 4646, September 2006.
+
+ [6] Hoffman, P. and M. Blanchet, "Preparation of Internationalized
+ Strings ("stringprep")", RFC 3454, December 2002.
+
+ [7] Davis, M. and K. Whistler, "Unicode Collation Algorithm version
+ 14", May 2005,
+ <http://www.unicode.org/reports/tr10/tr10-14.html>.
+
+ [8] Davis, M. and M. Suignard, "Unicode Security Considerations",
+ February 2006, <http://www.unicode.org/reports/tr36/>.
+
+13.2. Informative References
+
+ [9] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message Bodies",
+ RFC 2045, November 1996.
+
+ [10] Melnikov, A., "Simple Authentication and Security Layer
+ (SASL)", RFC 4422, June 2006.
+
+ [11] Newman, C. and J. Myers, "ACAP -- Application Configuration
+ Access Protocol", RFC 2244, November 1997.
+
+ [12] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
+
+ [13] Freed, N. and J. Postel, "IANA Charset Registration
+ Procedures", BCP 19, RFC 2978, October 2000.
+
+
+
+
+
+Newman, et al. Standards Track [Page 24]
+
+RFC 4790 Collation Registry March 2007
+
+
+ [14] Showalter, T., "Sieve: A Mail Filtering Language", RFC 3028,
+ January 2001.
+
+ [15] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [16] Crispin, M. and K. Murchison, "Internet Message Access Protocol
+ - Sort and Thread Extensions", Work in Progress, May 2004.
+
+ [17] Newman, C. and A. Gulbrandsen, "Internet Message Access
+ Protocol Internationalization", Work in Progress, January 2006.
+
+Authors' Addresses
+
+ Chris Newman
+ Sun Microsystems
+ 1050 Lakes Drive
+ West Covina, CA 91790
+ USA
+
+ EMail: chris.newman@sun.com
+
+
+ Martin Duerst
+ Aoyama Gakuin University
+ 5-10-1 Fuchinobe
+ Sagamihara, Kanagawa 229-8558
+ Japan
+
+ Phone: +81 42 759 6329
+ Fax: +81 42 759 6495
+ EMail: duerst@it.aoyama.ac.jp
+ URI: http://www.sw.it.aoyama.ac.jp/D%C3%BCrst/
+
+ Note: Please write "Duerst" with u-umlaut wherever possible, for
+ example as "D&#252;rst" in XML and HTML.
+
+
+ Arnt Gulbrandsen
+ Oryx Mail Systems GmbH
+ Schweppermannstr. 8
+ 81671 Munich
+ Germany
+
+ Fax: +49 89 4502 9758
+ EMail: arnt@oryx.com
+ URI: http://www.oryx.com/arnt/
+
+
+
+
+Newman, et al. Standards Track [Page 25]
+
+RFC 4790 Collation Registry March 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+
+
+
+Newman, et al. Standards Track [Page 26]
+
diff --git a/imap/docs/rfc/rfc4959.txt b/imap/docs/rfc/rfc4959.txt
new file mode 100644
index 00000000..3df18354
--- /dev/null
+++ b/imap/docs/rfc/rfc4959.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group R. Siemborski
+Request for Comments: 4959 Google, Inc.
+Category: Standards Track A. Gulbrandsen
+ Oryx Mail Systems GmbH
+ September 2007
+
+
+ IMAP Extension for Simple Authentication and Security Layer (SASL)
+ Initial Client Response
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ To date, the Internet Message Access Protocol (IMAP) has used a
+ Simple Authentication and Security Layer (SASL) profile which always
+ required at least one complete round trip for an authentication, as
+ it did not support an initial client response argument. This
+ additional round trip at the beginning of the session is undesirable,
+ especially when round-trip costs are high.
+
+ This document defines an extension to IMAP which allows clients and
+ servers to avoid this round trip by allowing an initial client
+ response argument to the IMAP AUTHENTICATE command.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 1]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+1. Introduction
+
+ The SASL initial client response extension is present in any IMAP
+ [RFC3501] server implementation which returns "SASL-IR" as one of the
+ supported capabilities in its CAPABILITY response.
+
+ Servers which support this extension will accept an optional initial
+ client response with the AUTHENTICATE command for any SASL [RFC4422]
+ mechanisms which support it.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC2119].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+ Formal syntax is defined by [RFC4234] as extended by [RFC3501].
+
+3. IMAP Changes to the IMAP AUTHENTICATE Command
+
+ This extension adds an optional second argument to the AUTHENTICATE
+ command that is defined in Section 6.2.2 of [RFC3501]. If this
+ second argument is present, it represents the contents of the
+ "initial client response" defined in Section 5.1 of [RFC4422].
+
+ As with any other client response, this initial client response MUST
+ be encoded as defined in Section 4 of [RFC4648]. It also MUST be
+ transmitted outside of a quoted string or literal. To send a zero-
+ length initial response, the client MUST send a single pad character
+ ("="). This indicates that the response is present, but is a zero-
+ length string.
+
+ When decoding the BASE64 [RFC4648] data in the initial client
+ response, decoding errors MUST be treated as IMAP [RFC3501] would
+ handle them in any normal SASL client response. In particular, the
+ server should check for any characters not explicitly allowed by the
+ BASE64 alphabet, as well as any sequence of BASE64 characters that
+ contains the pad character ('=') anywhere other than the end of the
+ string (e.g., "=AAA" and "AAA=BBB" are not allowed).
+
+ If the client uses an initial response with a SASL mechanism that
+ does not support an initial response, the server MUST reject the
+ command with a tagged BAD response.
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 2]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+ Note: support and use of the initial client response is optional for
+ both clients and servers. Servers that implement this extension MUST
+ support clients that omit the initial client response, and clients
+ that implement this extension MUST NOT send an initial client
+ response to servers that do not advertise the SASL-IR capability. In
+ such a situation, clients MUST fall back to an IMAP [RFC3501]
+ compatible mode.
+
+ If either the client or the server do not support the SASL-IR
+ capability, a mechanism which uses an initial client response is
+ negotiated using the challenge/response exchange described in
+ [RFC3501], with an initial zero-length server challenge.
+
+4. Examples
+
+ The following is an example authentication using the PLAIN (see
+ [RFC4616]) SASL mechanism (under a TLS protection layer, see
+ [RFC4346]) and an initial client response:
+
+ ... client connects to server and negotiates a TLS
+ protection layer ...
+ C: C01 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN
+ S: C01 OK Completed
+ C: A01 AUTHENTICATE PLAIN dGVzdAB0ZXN0AHRlc3Q=
+ S: A01 OK Success (tls protection)
+
+ Note that even when a server supports this extension, the following
+ negotiation (which does not use the initial response) is still valid
+ and MUST be supported by the server:
+
+ ... client connects to server and negotiates a TLS
+ protection layer ...
+ C: C01 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN
+ S: C01 OK Completed
+ C: A01 AUTHENTICATE PLAIN
+ (note that there is a space following the "+" in the
+ following line)
+ S: +
+ C: dGVzdAB0ZXN0AHRlc3Q=
+ S: A01 OK Success (tls protection)
+
+ The following is an example authentication using the SASL EXTERNAL
+ mechanism (defined in [RFC4422]) under a TLS protection layer (see
+ [RFC4346]) and an empty initial client response:
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 3]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+ ... client connects to server and negotiates a TLS
+ protection layer ...
+ C: C01 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN AUTH=EXTERNAL
+ S: C01 OK Completed
+ C: A01 AUTHENTICATE EXTERNAL =
+ S: A01 OK Success (tls protection)
+
+ This is in contrast with the handling of such a situation when an
+ initial response is omitted:
+
+ ... client connects to server and negotiates a TLS protection
+ layer ...
+ C: C01 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 SASL-IR AUTH=PLAIN AUTH=EXTERNAL
+ S: C01 OK Completed
+ C: A01 AUTHENTICATE EXTERNAL
+ (note that there is a space following the "+" in the
+ following line)
+ S: +
+ C:
+ S: A01 OK Success (tls protection)
+
+5. IANA Considerations
+
+ The IANA has added SASL-IR to the IMAP4 Capabilities Registry.
+
+6. Security Considerations
+
+ The extension defined in this document is subject to many of the
+ Security Considerations defined in [RFC3501] and [RFC4422].
+
+ Server implementations MUST treat the omission of an initial client
+ response from the AUTHENTICATE command as defined by [RFC3501] (as if
+ this extension did not exist).
+
+ Although [RFC3501] has no express line length limitations, some
+ implementations choose to enforce them anyway. Such implementations
+ MUST be aware that the addition of the initial response parameter to
+ AUTHENTICATE may increase the maximum line length that IMAP parsers
+ may expect to support. Server implementations MUST be able to
+ receive the largest possible initial client response that their
+ supported mechanisms might receive.
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 4]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+7. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form [RFC4234] notation. [RFC3501] defines the non-terminals
+ capability, auth-type, and base64.
+
+ capability =/ "SASL-IR"
+
+ authenticate = "AUTHENTICATE" SP auth-type [SP (base64 / "=")]
+ *(CRLF base64)
+ ;;redefine AUTHENTICATE from [RFC3501]
+
+8. Acknowledgments
+
+ The authors would like to acknowledge the contributions of Ken
+ Murchison and Mark Crispin, along with the rest of the IMAPEXT
+ Working Group for their assistance in reviewing this document.
+
+ Alexey Melnikov and Cyrus Daboo also had some early discussions about
+ this extension.
+
+9. References
+
+9.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+ [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
+ Security Layer (SASL)", RFC 4422, June 2006.
+
+ [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
+ Encodings", RFC 4648, October 2006.
+
+9.2. Informative References
+
+ [RFC4616] Zeilenga, K., "The PLAIN Simple Authentication and
+ Security Layer (SASL) Mechanism", RFC 4616, August 2006.
+
+ [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
+ (TLS) Protocol Version 1.1", RFC 4346, April 2006.
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 5]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+Authors' Addresses
+
+ Robert Siemborski
+ Google, Inc.
+ 1600 Ampitheatre Parkway
+ Mountain View, CA 94043
+
+ Phone: +1 650 623 6925
+ EMail: robsiemb@google.com
+
+
+ Arnt Gulbrandsen
+ Oryx Mail Systems GmbH
+ Schweppermannstr. 8
+ D-81671 Muenchen
+ Germany
+
+ EMail: arnt@oryx.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 6]
+
+RFC 4959 IMAP Ext for SASL Initial Client Response September 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Siemborski & Gulbrandsen Standards Track [Page 7]
+
diff --git a/imap/docs/rfc/rfc4978.txt b/imap/docs/rfc/rfc4978.txt
new file mode 100644
index 00000000..14b56b6e
--- /dev/null
+++ b/imap/docs/rfc/rfc4978.txt
@@ -0,0 +1,507 @@
+
+
+
+
+
+
+Network Working Group A. Gulbrandsen
+Request for Comments: 4978 Oryx Mail Systems GmbH
+Category: Standards Track August 2007
+
+
+ The IMAP COMPRESS Extension
+
+Status of this Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ The COMPRESS extension allows an IMAP connection to be effectively
+ and efficiently compressed.
+
+ Table of Contents
+
+ 1. Introduction and Overview .......................................2
+ 2. Conventions Used in This Document ...............................2
+ 3. The COMPRESS Command ............................................3
+ 4. Compression Efficiency ..........................................4
+ 5. Formal Syntax ...................................................6
+ 6. Security Considerations .........................................6
+ 7. IANA Considerations .............................................6
+ 8. Acknowledgements ................................................7
+ 9. References ......................................................7
+ 9.1. Normative References .......................................7
+ 9.2. Informative References .....................................7
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen Standards Track [Page 1]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+1. Introduction and Overview
+
+ A server which supports the COMPRESS extension indicates this with
+ one or more capability names consisting of "COMPRESS=" followed by a
+ supported compression algorithm name as described in this document.
+
+ The goal of COMPRESS is to reduce the bandwidth usage of IMAP.
+
+ Compared to PPP compression (see [RFC1962]) and modem-based
+ compression (see [MNP] and [V42BIS]), COMPRESS offers much better
+ compression efficiency. COMPRESS can be used together with Transport
+ Security Layer (TLS) [RFC4346], Simple Authentication and Security
+ layer (SASL) encryption, Virtual Private Networks (VPNs), etc.
+ Compared to TLS compression [RFC3749], COMPRESS has the following
+ (dis)advantages:
+
+ - COMPRESS can be implemented easily both by IMAP servers and
+ clients.
+
+ - IMAP COMPRESS benefits from an intimate knowledge of the IMAP
+ protocol's state machine, allowing for dynamic and aggressive
+ optimization of the underlying compression algorithm's parameters.
+
+ - When the TLS layer implements compression, any protocol using that
+ layer can transparently benefit from that compression (e.g., SMTP
+ and IMAP). COMPRESS is specific to IMAP.
+
+ In order to increase interoperation, it is desirable to have as few
+ different compression algorithms as possible, so this document
+ specifies only one. The DEFLATE algorithm (defined in [RFC1951]) is
+ standard, widely available and fairly efficient, so it is the only
+ algorithm defined by this document.
+
+ In order to increase interoperation, IMAP servers that advertise this
+ extension SHOULD also advertise the TLS DEFLATE compression mechanism
+ as defined in [RFC3749]. IMAP clients MAY use either COMPRESS or TLS
+ compression, however, if the client and server support both, it is
+ RECOMMENDED that the client choose TLS compression.
+
+ The extension adds one new command (COMPRESS) and no new responses.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC2119].
+
+ Formal syntax is defined by [RFC4234] as modified by [RFC3501].
+
+
+
+Gulbrandsen Standards Track [Page 2]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+ In the examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. "[...]" denotes elision.
+
+3. The COMPRESS Command
+
+ Arguments: Name of compression mechanism: "DEFLATE".
+
+ Responses: None
+
+ Result: OK The server will compress its responses and expects the
+ client to compress its commands.
+ NO Compression is already active via another layer.
+ BAD Command unknown, invalid or unknown argument, or COMPRESS
+ already active.
+
+ The COMPRESS command instructs the server to use the named
+ compression mechanism ("DEFLATE" is the only one defined) for all
+ commands and/or responses after COMPRESS.
+
+ The client MUST NOT send any further commands until it has seen the
+ result of COMPRESS. If the response was OK, the client MUST compress
+ starting with the first command after COMPRESS. If the server
+ response was BAD or NO, the client MUST NOT turn on compression.
+
+ If the server responds NO because it knows that the same mechanism is
+ active already (e.g., because TLS has negotiated the same mechanism),
+ it MUST send COMPRESSIONACTIVE as resp-text-code (see [RFC3501],
+ Section 7.1), and the resp-text SHOULD say which layer compresses.
+
+ If the server issues an OK response, the server MUST compress
+ starting immediately after the CRLF which ends the tagged OK
+ response. (Responses issued by the server before the OK response
+ will, of course, still be uncompressed.) If the server issues a BAD
+ or NO response, the server MUST NOT turn on compression.
+
+ For DEFLATE (as for many other compression mechanisms), the
+ compressor can trade speed against quality. When decompressing there
+ isn't much of a tradeoff. Consequently, the client and server are
+ both free to pick the best reasonable rate of compression for the
+ data they send.
+
+ When COMPRESS is combined with TLS (see [RFC4346]) or SASL (see
+ [RFC4422]) security layers, the sending order of the three extensions
+ MUST be first COMPRESS, then SASL, and finally TLS. That is, before
+ data is transmitted it is first compressed. Second, if a SASL
+ security layer has been negotiated, the compressed data is then
+ signed and/or encrypted accordingly. Third, if a TLS security layer
+ has been negotiated, the data from the previous step is signed and/or
+
+
+
+Gulbrandsen Standards Track [Page 3]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+ encrypted accordingly. When receiving data, the processing order
+ MUST be reversed. This ensures that before sending, data is
+ compressed before it is encrypted, independent of the order in which
+ the client issues COMPRESS, AUTHENTICATE, and STARTTLS.
+
+ The following example illustrates how commands and responses are
+ compressed during a simple login sequence:
+
+ S: * OK [CAPABILITY IMAP4REV1 STARTTLS COMPRESS=DEFLATE]
+ C: a starttls
+ S: a OK TLS active
+
+ From this point on, everything is encrypted.
+
+ C: b login arnt tnra
+ S: b OK Logged in as arnt
+ C: c compress deflate
+ S: d OK DEFLATE active
+
+ From this point on, everything is compressed before being
+ encrypted.
+
+ The following example demonstrates how a server may refuse to
+ compress twice:
+
+ S: * OK [CAPABILITY IMAP4REV1 STARTTLS COMPRESS=DEFLATE]
+ [...]
+ C: c compress deflate
+ S: c NO [COMPRESSIONACTIVE] DEFLATE active via TLS
+
+4. Compression Efficiency
+
+ This section is informative, not normative.
+
+ IMAP poses some unusual problems for a compression layer.
+
+ Upstream is fairly simple. Most IMAP clients send the same few
+ commands again and again, so any compression algorithm that can
+ exploit repetition works efficiently. The APPEND command is an
+ exception; clients that send many APPEND commands may want to
+ surround large literals with flushes in the same way as is
+ recommended for servers later in this section.
+
+ Downstream has the unusual property that several kinds of data are
+ sent, confusing all dictionary-based compression algorithms.
+
+
+
+
+
+
+Gulbrandsen Standards Track [Page 4]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+ One type is IMAP responses. These are highly compressible; zlib
+ using its least CPU-intensive setting compresses typical responses to
+ 25-40% of their original size.
+
+ Another type is email headers. These are equally compressible, and
+ benefit from using the same dictionary as the IMAP responses.
+
+ A third type is email body text. Text is usually fairly short and
+ includes much ASCII, so the same compression dictionary will do a
+ good job here, too. When multiple messages in the same thread are
+ read at the same time, quoted lines etc. can often be compressed
+ almost to zero.
+
+ Finally, attachments (non-text email bodies) are transmitted, either
+ in binary form or encoded with base-64.
+
+ When attachments are retrieved in binary form, DEFLATE may be able to
+ compress them, but the format of the attachment is usually not IMAP-
+ like, so the dictionary built while compressing IMAP does not help.
+ The compressor has to adapt its dictionary from IMAP to the
+ attachment's format, and then back. A few file formats aren't
+ compressible at all using deflate, e.g., .gz, .zip, and .jpg files.
+
+ When attachments are retrieved in base-64 form, the same problems
+ apply, but the base-64 encoding adds another problem. 8-bit
+ compression algorithms such as deflate work well on 8-bit file
+ formats, however base-64 turns a file into something resembling 6-bit
+ bytes, hiding most of the 8-bit file format from the compressor.
+
+ When using the zlib library (see [RFC1951]), the functions
+ deflateInit2(), deflate(), inflateInit2(), and inflate() suffice to
+ implement this extension. The windowBits value must be in the range
+ -8 to -15, or else deflateInit2() uses the wrong format.
+ deflateParams() can be used to improve compression rate and resource
+ use. The Z_FULL_FLUSH argument to deflate() can be used to clear the
+ dictionary (the receiving peer does not need to do anything).
+
+ A client can improve downstream compression by implementing BINARY
+ (defined in [RFC3516]) and using FETCH BINARY instead of FETCH BODY.
+ In the author's experience, the improvement ranges from 5% to 40%
+ depending on the attachment being downloaded.
+
+ A server can improve downstream compression if it hints to the
+ compressor that the data type is about to change strongly, e.g., by
+ sending a Z_FULL_FLUSH at the start and end of large non-text
+ literals (before and after '*CHAR8' in the definition of literal in
+ RFC 3501, page 86). Small literals are best left alone. A possible
+ boundary is 5k.
+
+
+
+Gulbrandsen Standards Track [Page 5]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+ A server can improve the CPU efficiency both of the server and the
+ client if it adjusts the compression level (e.g., using the
+ deflateParams() function in zlib) at these points, to avoid trying to
+ compress incompressible attachments. A very simple strategy is to
+ change the level to 0 at the start of a literal provided the first
+ two bytes are either 0x1F 0x8B (as in deflate-compressed files) or
+ 0xFF 0xD8 (JPEG), and to keep it at 1-5 the rest of the time. More
+ complex strategies are possible.
+
+5. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [RFC4234]. This syntax augments
+ the grammar specified in [RFC3501]. [RFC4234] defines SP and
+ [RFC3501] defines command-auth, capability, and resp-text-code.
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+ command-auth =/ compress
+
+ compress = "COMPRESS" SP algorithm
+
+ capability =/ "COMPRESS=" algorithm
+ ;; multiple COMPRESS capabilities allowed
+
+ algorithm = "DEFLATE"
+
+ resp-text-code =/ "COMPRESSIONACTIVE"
+
+ Note that due the syntax of capability names, future algorithm names
+ must be atoms.
+
+6. Security Considerations
+
+ As for TLS compression [RFC3749].
+
+7. IANA Considerations
+
+ The IANA has added COMPRESS=DEFLATE to the list of IMAP capabilities.
+
+
+
+
+
+
+
+
+
+Gulbrandsen Standards Track [Page 6]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+8. Acknowledgements
+
+ Eric Burger, Dave Cridland, Tony Finch, Ned Freed, Philip Guenther,
+ Randall Gellens, Tony Hansen, Cullen Jennings, Stephane Maes, Alexey
+ Melnikov, Lyndon Nerenberg, and Zoltan Ordogh have all helped with
+ this document.
+
+ The author would also like to thank various people in the rooms at
+ meetings, whose help is real, but not reflected in the author's
+ mailbox.
+
+9. References
+
+9.1. Normative References
+
+ [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
+ version 1.3", RFC 1951, May 1996.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+9.2. Informative References
+
+ [RFC1962] Rand, D., "The PPP Compression Control Protocol (CCP)",
+ RFC 1962, June 1996.
+
+ [RFC3516] Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516,
+ April 2003.
+
+ [RFC3749] Hollenbeck, S., "Transport Layer Security Protocol
+ Compression Methods", RFC 3749, May 2004.
+
+ [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
+ (TLS) Protocol Version 1.1", RFC 4346, April 2006.
+
+ [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
+ Security Layer (SASL)", RFC 4422, June 2006.
+
+ [V42BIS] ITU, "V.42bis: Data compression procedures for data
+ circuit-terminating equipment (DCE) using error correction
+ procedures", http://www.itu.int/rec/T-REC-V.42bis, January
+ 1990.
+
+
+
+Gulbrandsen Standards Track [Page 7]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+ [MNP] Gilbert Held, "The Complete Modem Reference", Second
+ Edition, Wiley Professional Computing, ISBN 0-471-00852-4,
+ May 1994.
+
+Author's Address
+
+ Arnt Gulbrandsen
+ Oryx Mail Systems GmbH
+ Schweppermannstr. 8
+ D-81671 Muenchen
+ Germany
+
+ Fax: +49 89 4502 9758
+ EMail: arnt@oryx.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen Standards Track [Page 8]
+
+RFC 4978 The IMAP COMPRESS Extension August 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen Standards Track [Page 9]
+
diff --git a/imap/docs/rfc/rfc5032.txt b/imap/docs/rfc/rfc5032.txt
new file mode 100644
index 00000000..f8e48953
--- /dev/null
+++ b/imap/docs/rfc/rfc5032.txt
@@ -0,0 +1,283 @@
+
+
+
+
+
+
+Network Working Group E. Burger, Ed.
+Request for Comments: 5032 BEA Systems, Inc.
+Updates: 3501 September 2007
+Category: Standards Track
+
+
+ WITHIN Search Extension to the IMAP Protocol
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document describes the WITHIN extension to IMAP SEARCH. IMAP
+ SEARCH returns messages whose internal date is within or outside a
+ specified interval. The mechanism described here, OLDER and YOUNGER,
+ differs from BEFORE and SINCE in that the client specifies an
+ interval, rather than a date. WITHIN is useful for persistent
+ searches where either the device does not have the capacity to
+ perform the search at regular intervals or the network is of limited
+ bandwidth and thus there is a desire to reduce network traffic from
+ sending repeated requests and redundant responses.
+
+1. Introduction
+
+ This extension exposes two new search keys, OLDER and YOUNGER, each
+ of which takes a non-zero integer argument corresponding to a time
+ interval in seconds. The server calculates the time of interest by
+ subtracting the time interval the client presents from the current
+ date and time of the server. The server then either returns messages
+ older or younger than the resultant time and date, depending on the
+ search key used.
+
+1.1. Conventions Used in This Document
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server, respectively.
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [RFC2119].
+
+
+
+
+
+Burger Standards Track [Page 1]
+
+RFC 5032 Search Within September 2007
+
+
+ When describing the general syntax, we omit some definitions, as RFC
+ 3501 [RFC3501] defines them.
+
+2. Protocol Operation
+
+ An IMAP4 server that supports the capability described here MUST
+ return "WITHIN" as one of the server supported capabilities in the
+ CAPABILITY command.
+
+ For both the OLDER and YOUNGER search keys, the server calculates a
+ target date and time by subtracting the interval, specified in
+ seconds, from the current date and time of the server. The server
+ then compares the target time with the INTERNALDATE of the message,
+ as specified in IMAP [RFC3501]. For OLDER, messages match if the
+ INTERNALDATE is less recent than or equal to the target time. For
+ YOUNGER, messages match if the INTERNALDATE is more recent than or
+ equal to the target time.
+
+ Both OLDER and YOUNGER searches always result in exact matching, to
+ the resolution of a second. However, if one is doing a dynamic
+ evaluation, for example, in a context [CONTEXT], one needs to be
+ aware that the server might perform the evaluation periodically.
+ Thus, the server may delay the updates. Clients MUST be aware that
+ dynamic search results may not reflect the current state of the
+ mailbox. If the client needs a search result that reflects the
+ current state of the mailbox, we RECOMMEND that the client issue a
+ new search.
+
+3. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation. Elements not defined here can be found in the
+ formal syntax of ABNF [RFC4234] and IMAP [RFC3501].
+
+ This document extends RFC 3501 [RFC3501] with two new search keys:
+ OLDER <interval> and YOUNGER <interval>.
+
+ search-key =/ ( "OLDER" / "YOUNGER" ) SP nz-number
+ ; search-key defined in RFC 3501
+
+4. Example
+
+ C: a1 SEARCH UNSEEN YOUNGER 259200
+ S: a1 * SEARCH 4 8 15 16 23 42
+
+ Search for all unseen messages within the past 3 days, or 259200
+ seconds, according to the server's current time.
+
+
+
+
+Burger Standards Track [Page 2]
+
+RFC 5032 Search Within September 2007
+
+
+5. Security Considerations
+
+ The WITHIN extension does not raise any security considerations that
+ are not present in the base protocol. Considerations are the same as
+ for IMAP [RFC3501].
+
+6. IANA Considerations
+
+ Per the IMAP RFC [RFC3501], registration of a new IMAP capability in
+ the IMAP Capability registry requires the publication of a standards-
+ track RFC or an IESG approved experimental RFC. The registry is
+ currently located at
+ <http://www.iana.org/assignments/imap4-capabilities>. This
+ standards-track document defines the WITHIN IMAP capability. IANA
+ has added this extension to the IANA IMAP Capability registry.
+
+7. References
+
+7.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", RFC 2119, BCP 14, March 1997.
+
+ [RFC3501] Crispin, M., "Internet Message Access Protocol - Version
+ 4rev1", RFC 3501, March 2003.
+
+ [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", RFC 4234, October 2005.
+
+7.2. Informative References
+
+ [CONTEXT] Melnikov, D. and C. King, "Contexts for IMAP4", Work
+ in Progress, May 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Burger Standards Track [Page 3]
+
+RFC 5032 Search Within September 2007
+
+
+Appendix A. Contributors
+
+ Stephane Maes and Ray Cromwell wrote the original version of this
+ document as part of P-IMAP, as well as the first versions for the
+ IETF. From an attribution perspective, they are clearly authors.
+
+Appendix B. Acknowledgements
+
+ The authors want to thank all who have contributed key insight and
+ who have extensively reviewed and discussed the concepts of LPSEARCH.
+ They also thank the authors of its early introduction in P-IMAP.
+
+ We also want to give a special thanks to Arnt Gilbrandsen, Ken
+ Murchison, Zoltan Ordogh, and most especially Dave Cridland for their
+ review and suggestions. A special thank you goes to Alexey Melnikov
+ for his choice submission of text.
+
+Author's Address
+
+ Eric W. Burger (editor)
+ BEA Systems, Inc.
+ USA
+
+ EMail: eric.burger@bea.com
+ URI: http://www.standardstrack.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Burger Standards Track [Page 4]
+
+RFC 5032 Search Within September 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Burger Standards Track [Page 5]
+
diff --git a/imap/docs/rfc/rfc5051.txt b/imap/docs/rfc/rfc5051.txt
new file mode 100644
index 00000000..0a4479ca
--- /dev/null
+++ b/imap/docs/rfc/rfc5051.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group M. Crispin
+Request for Comments: 5051 University of Washington
+Category: Standards Track October 2007
+
+
+ i;unicode-casemap - Simple Unicode Collation Algorithm
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document describes "i;unicode-casemap", a simple case-
+ insensitive collation for Unicode strings. It provides equality,
+ substring, and ordering operations.
+
+1. Introduction
+
+ The "i;ascii-casemap" collation described in [COMPARATOR] is quite
+ simple to implement and provides case-independent comparisons for the
+ 26 Latin alphabetics. It is specified as the default and/or baseline
+ comparator in some application protocols, e.g., [IMAP-SORT].
+
+ However, the "i;ascii-casemap" collation does not produce
+ satisfactory results with non-ASCII characters. It is possible, with
+ a modest extension, to provide a more sophisticated collation with
+ greater multilingual applicability than "i;ascii-casemap". This
+ extension provides case-independent comparisons for a much greater
+ number of characters. It also collates characters with diacriticals
+ with the non-diacritical character forms.
+
+ This collation, "i;unicode-casemap", is intended to be an alternative
+ to, and preferred over, "i;ascii-casemap". It does not replace the
+ "i;basic" collation described in [BASIC].
+
+2. Unicode Casemap Collation Description
+
+ The "i;unicode-casemap" collation is a simple collation which is
+ case-insensitive in its treatment of characters. It provides
+ equality, substring, and ordering operations. The validity test
+ operation returns "valid" for any input.
+
+
+
+
+
+Crispin Standards Track [Page 1]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+ This collation allows strings in arbitrary (and mixed) character
+ sets, as long as the character set for each string is identified and
+ it is possible to convert the string to Unicode. Strings which have
+ an unidentified character set and/or cannot be converted to Unicode
+ are not rejected, but are treated as binary.
+
+ Each input string is prepared by converting it to a "titlecased
+ canonicalized UTF-8" string according to the following steps, using
+ UnicodeData.txt ([UNICODE-DATA]):
+
+ (1) A Unicode codepoint is obtained from the input string.
+
+ (a) If the input string is in a known charset that can be
+ converted to Unicode, a sequence in the string's charset
+ is read and checked for validity according to the rules of
+ that charset. If the sequence is valid, it is converted
+ to a Unicode codepoint. Note that for input strings in
+ UTF-8, the UTF-8 sequence must be valid according to the
+ rules of [UTF-8]; e.g., overlong UTF-8 sequences are
+ invalid.
+
+ (b) If the input string is in an unknown charset, or an
+ invalid sequence occurs in step (1)(a), conversion ceases.
+ No further preparation is performed, and any partial
+ preparation results are discarded. The original string is
+ used unchanged with the i;octet comparator.
+
+ (2) The following steps, using UnicodeData.txt ([UNICODE-DATA]),
+ are performed on the resulting codepoint from step (1)(a).
+
+ (a) If the codepoint has a titlecase property in
+ UnicodeData.txt (this is normally the same as the
+ uppercase property), the codepoint is converted to the
+ codepoints in the titlecase property.
+
+ (b) If the resulting codepoint from (2)(a) has a decomposition
+ property of any type in UnicodeData.txt, the codepoint is
+ converted to the codepoints in the decomposition property.
+ This step is recursively applied to each of the resulting
+ codepoints until no more decomposition is possible
+ (effectively Normalization Form KD).
+
+ Example: codepoint U+01C4 (LATIN CAPITAL LETTER DZ WITH CARON)
+ has a titlecase property of U+01C5 (LATIN CAPITAL LETTER D
+ WITH SMALL LETTER Z WITH CARON). Codepoint U+01C5 has a
+ decomposition property of U+0044 (LATIN CAPITAL LETTER D)
+ U+017E (LATIN SMALL LETTER Z WITH CARON). U+017E has a
+ decomposition property of U+007A (LATIN SMALL LETTER Z) U+030c
+
+
+
+Crispin Standards Track [Page 2]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+ (COMBINING CARON). Neither U+0044, U+007A, nor U+030C have
+ any decomposition properties. Therefore, U+01C4 is converted
+ to U+0044 U+007A U+030C by this step.
+
+ (3) The resulting codepoint(s) from step (2) is/are appended, in
+ UTF-8 format, to the "titlecased canonicalized UTF-8" string.
+
+ (4) Repeat from step (1) until there is no more data in the input
+ string.
+
+ Following the above preparation process on each string, the equality,
+ ordering, and substring operations are as for i;octet.
+
+ It is permitted to use an alternative implementation of the above
+ preparation process if it produces the same results. For example, it
+ may be more convenient for an implementation to convert all input
+ strings to a sequence of UTF-16 or UTF-32 values prior to performing
+ any of the step (2) actions. Similarly, if all input strings are (or
+ are convertible to) Unicode, it may be possible to use UTF-32 as an
+ alternative to UTF-8 in step (3).
+
+ Note: UTF-16 is unsuitable as an alternative to UTF-8 in step (3),
+ because UTF-16 surrogates will cause i;octet to collate codepoints
+ U+E0000 through U+FFFF after non-BMP codepoints.
+
+ This collation is not locale sensitive. Consequently, care should be
+ taken when using OS-supplied functions to implement this collation.
+ Functions such as strcasecmp and toupper are sometimes locale
+ sensitive and may inconsistently casemap letters.
+
+ The i;unicode-casemap collation is well suited to use with many
+ Internet protocols and computer languages. Use with natural language
+ is often inappropriate; even though the collation apparently supports
+ languages such as Swahili and English, in real-world use it tends to
+ mis-sort a number of types of string:
+
+ o people and place names containing scripts that are not collated
+ according to "alphabetical order".
+ o words with characters that have diacriticals. However,
+ i;unicode-casemap generally does a better job than i;ascii-casemap
+ for most (but not all) languages. For example, German umlaut
+ letters will sort correctly, but some Scandinavian letters will
+ not.
+ o names such as "Lloyd" (which in Welsh sorts after "Lyon", unlike
+ in English),
+ o strings containing other non-letter symbols; e.g., euro and pound
+ sterling symbols, quotation marks other than '"', dashes/hyphens,
+ etc.
+
+
+
+Crispin Standards Track [Page 3]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+3. Unicode Casemap Collation Registration
+
+ <?xml version='1.0'?>
+ <!DOCTYPE collation SYSTEM 'collationreg.dtd'>
+ <collation rfc="5051" scope="global" intendedUse="common">
+ <identifier>i;unicode-casemap</identifier>
+ <title>Unicode Casemap</title>
+ <operations>equality order substring</operations>
+ <specification>RFC 5051</specification>
+ <owner>IETF</owner>
+ <submitter>mrc@cac.washington.edu</submitter>
+ </collation>
+
+4. Security Considerations
+
+ The security considerations for [UTF-8], [STRINGPREP], and [UNICODE-
+ SECURITY] apply and are normative to this specification.
+
+ The results from this comparator will vary depending upon the
+ implementation for several reasons. Implementations MUST consider
+ whether these possibilities are a problem for their use case:
+
+ 1) New characters added in Unicode may have decomposition or
+ titlecase properties that will not be known to an implementation
+ based upon an older revision of Unicode. This impacts step (2).
+
+ 2) Step (2)(b) defines a subset of Normalization Form KD (NFKD) that
+ does not require normalization of out-of-order diacriticals.
+ However, an implementation MAY use an NFKD library routine that
+ does such normalization. This impacts step (2)(b) and possibly
+ also step (1)(a), and is an issue only with ill-formed UTF-8
+ input.
+
+ 3) The set of charsets handled in step (1)(a) is open-ended. UTF-8
+ (and, by extension, US-ASCII) are the only mandatory-to-implement
+ charsets. This impacts step (1)(a).
+
+ Implementations SHOULD, as far as feasible, support all the
+ charsets they are likely to encounter in the input data, in order
+ to avoid poor collation caused by the fall through to the (1)(b)
+ rule.
+
+ 4) Other charsets may have revisions which add new characters that
+ are not known to an implementation based upon an older revision.
+ This impacts step (1)(a) and possibly also step (1)(b).
+
+
+
+
+
+
+Crispin Standards Track [Page 4]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+ An attacker may create input that is ill-formed or in an unknown
+ charset, with the intention of impacting the results of this
+ comparator or exploiting other parts of the system which process this
+ input in different ways. Note, however, that even well-formed data
+ in a known charset can impact the result of this comparator in
+ unexpected ways. For example, an attacker can substitute U+0041
+ (LATIN CAPITAL LETTER A) with U+0391 (GREEK CAPITAL LETTER ALPHA) or
+ U+0410 (CYRILLIC CAPITAL LETTER A) in the intention of causing a
+ non-match of strings which visually appear the same and/or causing
+ the string to appear elsewhere in a sort.
+
+5. IANA Considerations
+
+ The i;unicode-casemap collation defined in section 2 has been added
+ to the registry of collations defined in [COMPARATOR].
+
+6. Normative References
+
+ [COMPARATOR] Newman, C., Duerst, M., and A. Gulbrandsen,
+ "Internet Application Protocol Collation
+ Registry", RFC 4790, February 2007.
+
+ [STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of
+ Internationalized Strings ("stringprep")", RFC
+ 3454, December 2002.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of
+ ISO 10646", STD 63, RFC 3629, November 2003.
+
+ [UNICODE-DATA] <http://www.unicode.org/Public/UNIDATA/
+ UnicodeData.txt>
+
+ Although the UnicodeData.txt file referenced
+ here is part of the Unicode standard, it is
+ subject to change as new characters are added
+ to Unicode and errors are corrected in Unicode
+ revisions. As a result, it may be less stable
+ than might otherwise be implied by the
+ standards status of this specification.
+
+ [UNICODE-SECURITY] Davis, M. and M. Suignard, "Unicode Security
+ Considerations", February 2006,
+ <http://www.unicode.org/reports/tr36/>.
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 5]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+7. Informative References
+
+ [BASIC] Newman, C., Duerst, M., and A. Gulbrandsen,
+ "i;basic - the Unicode Collation Algorithm",
+ Work in Progress, March 2007.
+
+ [IMAP-SORT] Crispin, M. and K. Murchison, "Internet Message
+ Access Protocol - SORT and THREAD Extensions",
+ Work in Progress, September 2007.
+
+Author's Address
+
+ Mark R. Crispin
+ Networks and Distributed Computing
+ University of Washington
+ 4545 15th Avenue NE
+ Seattle, WA 98105-4527
+
+ Phone: +1 (206) 543-5762
+ EMail: MRC@CAC.Washington.EDU
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+
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+
+
+
+
+
+
+
+Crispin Standards Track [Page 6]
+
+RFC 5051 i;unicode-casemap October 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Crispin Standards Track [Page 7]
+
diff --git a/imap/docs/rfc/rfc5092.txt b/imap/docs/rfc/rfc5092.txt
new file mode 100644
index 00000000..ab87f350
--- /dev/null
+++ b/imap/docs/rfc/rfc5092.txt
@@ -0,0 +1,1795 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov, Ed.
+Request for Comments: 5092 Isode Ltd.
+Obsoletes: 2192 C. Newman
+Updates: 4467 Sun Microsystems
+Category: Standards Track November 2007
+
+
+ IMAP URL Scheme
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ IMAP (RFC 3501) is a rich protocol for accessing remote message
+ stores. It provides an ideal mechanism for accessing public mailing
+ list archives as well as private and shared message stores. This
+ document defines a URL scheme for referencing objects on an IMAP
+ server.
+
+ This document obsoletes RFC 2192. It also updates RFC 4467.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 1]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 2. Conventions Used in This Document ...............................3
+ 3. IMAP userinfo Component (iuserinfo) .............................4
+ 3.1. IMAP Mailbox Naming Scope ..................................4
+ 3.2. IMAP User Name and Authentication Mechanism ................4
+ 3.3. Limitations of enc-user ....................................6
+ 4. IMAP Server .....................................................7
+ 5. Lists of Messages ...............................................7
+ 6. A Specific Message or Message Part ..............................8
+ 6.1. URLAUTH Authorized URL .....................................9
+ 6.1.1. Concepts ............................................9
+ 6.1.1.1. URLAUTH ....................................9
+ 6.1.1.2. Mailbox Access Key .........................9
+ 6.1.1.3. Authorized Access Identifier ...............9
+ 6.1.1.4. Authorization Mechanism ...................10
+ 6.1.1.5. Authorization Token .......................10
+ 6.1.2. URLAUTH Extensions to IMAP URL .....................10
+ 7. Relative IMAP URLs .............................................11
+ 7.1. absolute-path References ..................................12
+ 7.2. relative-path References ..................................12
+ 8. Internationalization Considerations ............................13
+ 9. Examples .......................................................13
+ 9.1. Examples of Relative URLs .................................16
+ 10. Security Considerations .......................................16
+ 10.1. Security Considerations Specific to URLAUTH Authorized
+ URL ......................................................17
+ 11. ABNF for IMAP URL Scheme ......................................17
+ 12. IANA Considerations ...........................................21
+ 12.1. IANA Registration of imap: URI Scheme ....................21
+ 13. References ....................................................22
+ 13.1. Normative References .....................................22
+ 13.2. Informative References ...................................23
+ Appendix A. Sample Code............................................24
+ Appendix B. List of Changes since RFC 2192.........................30
+ Appendix C. List of Changes since RFC 4467.........................31
+ Appendix D. Acknowledgments........................................31
+
+1. Introduction
+
+ The IMAP URL scheme is used to designate IMAP servers, mailboxes,
+ messages, MIME bodies [MIME], and search programs on Internet hosts
+ accessible using the IMAP protocol over TCP.
+
+ The IMAP URL follows the common Internet scheme syntax as defined in
+ [URI-GEN]. If :<port> is omitted, the port defaults to 143 (as
+ defined in Section 2.1 of [IMAP4]).
+
+
+
+Melnikov & Newman Standards Track [Page 2]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ An absolute IMAP URL takes one of the following forms:
+
+ imap://<iserver>[/]
+
+ imap://<iserver>/<enc-mailbox>[<uidvalidity>][?<enc-search>]
+
+ imap://<iserver>/<enc-mailbox>[<uidvalidity>]<iuid>
+ [<isection>][<ipartial>][<iurlauth>]
+
+ The first form is used to refer to an IMAP server (see Section 4),
+ the second form refers to the contents of a mailbox or a set of
+ messages resulting from a search (see Section 5), and the final form
+ refers to a specific message or message part, and possibly a byte
+ range in that part (see Section 6). If [URLAUTH] extension is
+ supported, then the final form can have the <iurlauth> component (see
+ Section 6.1 for more details).
+
+ The <iserver> component common to all types of absolute IMAP URLs has
+ the following syntax expressed in ABNF [ABNF]:
+
+ [iuserinfo "@"] host [ ":" port ]
+
+ The <iserver> component is the same as "authority" defined in
+ [URI-GEN]. The syntax and uses of the <iuserinfo> ("IMAP userinfo
+ component") are described in detail in Section 3. The syntax of
+ <host> and <port> is described in [URI-GEN].
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [KEYWORDS].
+
+ This document references many productions from [URI-GEN]. When the
+ document needs to emphasize IMAP URI-specific differences from [URI-
+ GEN] (i.e., for parts of IMAP URIs that have more restricted syntax
+ than generic URIs), it uses a non-terminal i<foo> to define an IMAP-
+ specific version of the non-terminal <foo> from [URI-GEN].
+
+ Note that the ABNF syntax shown in Section 11 is normative. Sections
+ 2-6 may use a less formal syntax that does not necessarily match the
+ normative ABNF shown in Section 11. If there are any differences
+ between the syntax shown in Sections 2-6 and Section 11, then the
+ syntax shown in Section 11 must be treated as authoritative. Non-
+ syntax requirements included in Sections 2-6 are, of course,
+ normative.
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 3]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+3. IMAP userinfo Component (iuserinfo)
+
+ The <iuserinfo> component conforms to the generic syntax of
+ <userinfo> defined in [URI-GEN]. It has the following syntax
+ expressed in ABNF [ABNF]:
+
+ enc-user [iauth] / [enc-user] iauth
+
+ The meaning of the different parts is described in subsections of
+ this section.
+
+3.1. IMAP Mailbox Naming Scope
+
+ The "enc-user" part of the "iuserinfo" component, if present, denotes
+ mailbox naming scope. If it is absent, the IMAP URL can only
+ reference mailboxes with globally unique names, i.e., mailboxes with
+ names that don't change depending on the user the client
+ authenticated as to the IMAP server. Note that not all IMAP
+ implementations support globally unique names.
+
+ For example, a personal mailbox described by the following URL
+ <imap://michael@example.org/INBOX> is most likely different from a
+ personal mailbox described by <imap://bester@example.org/INBOX>, even
+ though both URLs use the same mailbox name.
+
+3.2. IMAP User Name and Authentication Mechanism
+
+ The userinfo component (see [URI-GEN]) of an IMAP URI may contain an
+ IMAP user name (a.k.a. authorization identity [SASL], "enc-user")
+ and/or an authentication mechanism. (Note that the "enc-user" also
+ defines a mailbox naming scope as described in Section 3.1). The
+ IMAP user name and the authentication mechanism are used in the
+ "LOGIN" or "AUTHENTICATE" commands after making the connection to the
+ IMAP server.
+
+ If no user name and no authentication mechanism are supplied, the
+ client MUST authenticate as anonymous to the server. If the server
+ advertises AUTH=ANONYMOUS IMAP capability, the client MUST use the
+ AUTHENTICATE command with ANONYMOUS [ANONYMOUS] SASL mechanism. If
+ SASL ANONYMOUS is not available, the (case-insensitive) user name
+ "anonymous" is used with the "LOGIN" command and the Internet email
+ address of the end user accessing the resource is supplied as the
+ password. The latter option is given in order to provide for
+ interoperability with deployed servers.
+
+ Note that, as described in RFC 3501, the "LOGIN" command MUST NOT be
+ used when the IMAP server advertises the LOGINDISABLED capability.
+
+
+
+
+Melnikov & Newman Standards Track [Page 4]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ An authentication mechanism (as used by the IMAP AUTHENTICATE
+ command) can be expressed by adding ";AUTH=<enc-auth-type>" to the
+ end of the user name in an IMAP URL. When such an <enc-auth-type> is
+ indicated, the client SHOULD request appropriate credentials from
+ that mechanism and use the "AUTHENTICATE" command instead of the
+ "LOGIN" command. If no user name is specified, one MUST be obtained
+ from the mechanism or requested from the user/configuration as
+ appropriate.
+
+ The string ";AUTH=*" indicates that the client SHOULD select an
+ appropriate authentication mechanism. (Though the '*' character in
+ this usage is not strictly a delimiter, it is being treated like a
+ sub-delim [URI-GEN] in this instance. It MUST NOT be percent-encoded
+ in this usage, as ";AUTH=%2A" will not match this production.) It
+ MAY use any mechanism listed in the response to the CAPABILITY
+ command (or CAPABILITY response code) or use an out-of-band security
+ service resulting in a PREAUTH connection. If no user name is
+ specified and no appropriate authentication mechanisms are available,
+ the client SHOULD fall back to anonymous login as described above.
+ The behavior prescribed in this section allows a URL that grants
+ read-write access to authorized users and read-only anonymous access
+ to other users.
+
+ If a user name is included with no authentication mechanism, then
+ ";AUTH=*" is assumed.
+
+ Clients must take care when resolving a URL that requires or requests
+ any sort of authentication, since URLs can easily come from untrusted
+ sources. Supplying authentication credentials to the wrong server
+ may compromise the security of the user's account; therefore, the
+ program resolving the URL should meet at least one of the following
+ criteria in this case:
+
+ 1) The URL comes from a trusted source, such as a referral server
+ that the client has validated and trusts according to site policy.
+ Note that user entry of the URL may or may not count as a trusted
+ source, depending on the experience level of the user and site
+ policy.
+
+ 2) Explicit local site policy permits the client to connect to the
+ server in the URL. For example, a company example.com may have a
+ site policy to trust all IMAP server names ending in example.com,
+ whereas such a policy would be unwise for example.edu where random
+ students can set up IMAP servers.
+
+ 3) The user confirms that connecting to that domain name with the
+ specified credentials and/or mechanism is permitted. For example,
+ when using "LOGIN" or SASL PLAIN with Transport Layer Security
+
+
+
+Melnikov & Newman Standards Track [Page 5]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ (TLS), the IMAP URL client presents a dialog box "Is it OK to send
+ your password to server "example.com"? Please be aware the owners
+ of example.com will be able to reuse your password to connect to
+ other servers on your behalf".
+
+ 4) A mechanism is used that validates the server before passing
+ potentially compromising client credentials. For example, a site
+ has a designated TLS certificate used to certify site-trusted IMAP
+ server certificates, and this has been configured explicitly into
+ the IMAP URL client. Another example is use of a Simple
+ Authentication and Security Layer (SASL) mechanism such as
+ DIGEST-MD5 [DIGEST-MD5], which supports mutual authentication.
+
+ 5) An authentication mechanism is used that will not reveal any
+ information to the server that could be used to compromise future
+ connections. Examples are SASL ANONYMOUS [ANONYMOUS] or GSSAPI
+ [GSSAPI].
+
+ URLs that do not include a user name but include an authentication
+ mechanism (";AUTH=<mech>") must be treated with extra care, since for
+ some <mech>s they are more likely to compromise the user's primary
+ account. A URL containing ";AUTH=*" must also be treated with extra
+ care since it might fall back on a weaker security mechanism.
+ Finally, clients are discouraged from using a plaintext password as a
+ fallback with ";AUTH=*" unless the connection has strong encryption.
+
+ A program interpreting IMAP URLs MAY cache open connections to an
+ IMAP server for later reuse. If a URL contains a user name, only
+ connections authenticated as that user may be reused. If a URL does
+ not contain a user name or authentication mechanism, then only an
+ anonymous connection may be reused.
+
+ Note that if unsafe or reserved characters such as " " (space) or ";"
+ are present in the user name or authentication mechanism, they MUST
+ be percent-encoded as described in [URI-GEN].
+
+3.3. Limitations of enc-user
+
+ As per Sections 3.1 and 3.2 of this document, the IMAP URI enc-user
+ has two purposes:
+
+ 1) It provides context for user-specific mailbox paths such as
+ "INBOX" (Section 3.1).
+
+ 2) It specifies that resolution of the URL requires logging in as
+ that user and limits use of that URL to only that user (Section
+ 3.2).
+
+
+
+
+Melnikov & Newman Standards Track [Page 6]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ An obvious limitation of using the same field for both purposes is
+ that the URL can be resolved only by the mailbox owner. In order to
+ avoid this restriction, implementations should use globally unique
+ mailbox names (see Section 3.1) whenever possible.
+
+ Note: There is currently no general way in IMAP of learning a
+ globally unique name for a mailbox. However, by looking at the
+ NAMESPACE [NAMESPACE] command result, it is possible to determine
+ whether or not a mailbox name is globally unique.
+
+ The URLAUTH component overrides the second purpose of the enc-user in
+ the IMAP URI and by default permits the URI to be resolved by any
+ user permitted by the <access> identifier. URLAUTH and <access>
+ identifier are described in Section 6.1.
+
+4. IMAP Server
+
+ An IMAP URL referring to an IMAP server has the following form:
+
+ imap://<iserver>[/]
+
+ This URL type is frequently used to describe a location of an IMAP
+ server, both in referrals and in configuration. It may optionally
+ contain the <iuserinfo> component (see Sections 3 and 11). A program
+ interpreting this URL would issue the standard set of commands it
+ uses to present a view of the content of the IMAP server, as visible
+ to the user described by the "enc-user" part of the <iuserinfo>
+ component, if the "enc-user" part is specified.
+
+5. Lists of Messages
+
+ An IMAP URL referring to a list of messages has the following form:
+
+ imap://<iserver>/<enc-mailbox>[<uidvalidity>][?<enc-search>]
+
+ The <enc-mailbox> field is used as the argument to the IMAP4 "SELECT"
+ or "EXAMINE" command. Note that if unsafe or reserved characters
+ such as " " (space), ";", or "?" are present in <enc-mailbox>, they
+ MUST be percent-encoded as described in [URI-GEN].
+
+ The <uidvalidity> field is optional. If it is present, it MUST be
+ the same as the value of IMAP4 UIDVALIDITY response code at the time
+ the URL was created. This MUST be used by the program interpreting
+ the IMAP URL to determine if the URL is stale. If the IMAP URL is
+ stale, then the program should behave as if the corresponding mailbox
+ doesn't exist.
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 7]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ Note that the <uidvalidity> field is a modifier to the <enc-mailbox>,
+ i.e., it is considered a part of the last "component" (as used in
+ [URI-GEN]) of the <enc-mailbox>. This is significant during relative
+ URI resolution.
+
+ The "?<enc-search>" field is optional. If it is not present, the
+ program interpreting the URL will present the entire content of the
+ mailbox.
+
+ If the "?<enc-search>" field is present, the program interpreting the
+ URL should use the contents of this field as arguments following an
+ IMAP4 SEARCH command. These arguments are likely to contain unsafe
+ characters such as " " (space) (which are likely to be present in the
+ <enc-search>). If unsafe characters are present, they MUST be
+ percent-encoded as described in [URI-GEN].
+
+ Note that quoted strings and non-synchronizing literals [LITERAL+]
+ are allowed in the <enc-search> content; however, synchronizing
+ literals are not allowed, as their presence would effectively mean
+ that the agent interpreting IMAP URLs needs to parse an <enc-search>
+ content, find all synchronizing literals, and perform proper command
+ continuation request handling (see Sections 4.3 and 7 of [IMAP4]).
+
+6. A Specific Message or Message Part
+
+ An IMAP URL referring to a specific message or message part has the
+ following form:
+
+ imap://<iserver>/<enc-mailbox>[<uidvalidity>]<iuid>
+ [<isection>][<ipartial>][<iurlauth>]
+
+ The <enc-mailbox> and [uidvalidity] are as defined in Section 5
+ above.
+
+ If <uidvalidity> is present in this form, it SHOULD be used by the
+ program interpreting the URL to determine if the URL is stale.
+
+ The <iuid> refers to an IMAP4 message Unique Identifier (UID), and it
+ SHOULD be used as the <set> argument to the IMAP4 "UID FETCH"
+ command.
+
+ The <isection> field is optional. If not present, the URL refers to
+ the entire Internet message as returned by the IMAP command "UID
+ FETCH <uid> BODY.PEEK[]". If present, the URL refers to the object
+ returned by a "UID FETCH <uid> BODY.PEEK[<section>]" command. The
+ type of the object may be determined by using a "UID FETCH <uid>
+ BODYSTRUCTURE" command and locating the appropriate part in the
+
+
+
+
+Melnikov & Newman Standards Track [Page 8]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ resulting BODYSTRUCTURE. Note that unsafe characters in [isection]
+ MUST be percent-encoded as described in [URI-GEN].
+
+ The <ipartial> field is optional. If present, it effectively appends
+ "<<partial-range>>" to the end of the UID FETCH BODY.PEEK[<section>]
+ command constructed as described in the previous paragraph. In other
+ words, it allows the client to request a byte range of the
+ message/message part.
+
+ The <iurlauth> field is described in detail in Section 6.1.
+
+6.1. URLAUTH Authorized URL
+
+ URLAUTH authorized URLs are only supported by an IMAP server
+ advertising the URLAUTH IMAP capability [URLAUTH].
+
+6.1.1. Concepts
+
+6.1.1.1. URLAUTH
+
+ URLAUTH is a component, appended at the end of a URL, that conveys
+ authorization to access the data addressed by that URL. It contains
+ an authorized access identifier, an authorization mechanism name, and
+ an authorization token. The authorization token is generated from
+ the URL, the authorized access identifier, authorization mechanism
+ name, and a mailbox access key.
+
+ Note: This specification only allows for the URLAUTH component in
+ IMAP URLs describing a message or its part.
+
+6.1.1.2. Mailbox Access Key
+
+ The mailbox access key is an unpredictable, random string. To ensure
+ unpredictability, the random string with at least 128 bits of entropy
+ is generated by software or hardware (not by the human user).
+
+ Each user has a table of mailboxes and an associated mailbox access
+ key for each mailbox. Consequently, the mailbox access key is per-
+ user and per-mailbox. In other words, two users sharing the same
+ mailbox each have a different mailbox access key for that mailbox,
+ and each mailbox accessed by a single user also has a different
+ mailbox access key.
+
+6.1.1.3. Authorized Access Identifier
+
+ The authorized <access> identifier restricts use of the URLAUTH
+ authorized URL to certain users authorized on the server, as
+ described in Section 6.1.2.
+
+
+
+Melnikov & Newman Standards Track [Page 9]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+6.1.1.4. Authorization Mechanism
+
+ The authorization mechanism is the algorithm by which the URLAUTH is
+ generated and subsequently verified, using the mailbox access key.
+
+6.1.1.5. Authorization Token
+
+ The authorization token is a deterministic string of at least 128
+ bits that an entity with knowledge of the secret mailbox access key
+ and URL authorization mechanism can use to verify the URL.
+
+6.1.2. URLAUTH Extensions to IMAP URL
+
+ A specific message or message part IMAP URL can optionally contain
+ ";EXPIRE=<datetime>" and/or ";URLAUTH=<access>:<mech>:<token>".
+
+ When ";EXPIRE=<datetime>" is used, this indicates the latest date and
+ time that the URL is valid. After that date and time, the URL has
+ expired and server implementations MUST reject the URL. If
+ ";EXPIRE=<datetime>" is not used, the URL has no expiration, but can
+ still be revoked using the RESETKEY command [URLAUTH].
+
+ The URLAUTH takes the form ";URLAUTH=<access>:<mech>:<token>", and it
+ MUST be at the end of the URL. It is composed of three parts. The
+ <access> portion provides the authorized access identifiers that may
+ constrain the operations and users that are permitted to use this
+ URL. The <mech> portion provides the authorization mechanism used by
+ the IMAP server to generate the authorization token that follows.
+ The <token> portion provides the authorization token, which can be
+ generated using the GENURLAUTH command [URLAUTH].
+
+ The "submit+" <access> identifier prefix, followed by a userid,
+ indicates that only a userid authorized as a message submission
+ entity on behalf of the specified userid is permitted to use this
+ URL. The IMAP server does not validate the specified userid but does
+ validate that the IMAP session has an authorization identity that is
+ authorized as a message submission entity. The authorized message
+ submission entity MUST validate the userid prior to contacting the
+ IMAP server.
+
+ The "user+" <access> identifier prefix, followed by a userid,
+ indicates that use of this URL is limited to IMAP sessions that are
+ logged in as the specified userid (that is, have authorization
+ identity as that userid).
+
+ Note: If a SASL mechanism that provides both authorization and
+ authentication identifiers is used to authenticate to the IMAP
+ server, the "user+" <access> identifier MUST match the
+
+
+
+Melnikov & Newman Standards Track [Page 10]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ authorization identifier. If the SASL mechanism can't transport
+ the authorization identifier, the "user+" <access> identifier MUST
+ match the authorization identifier derived from the authentication
+ identifier (see [SASL]).
+
+ The "authuser" <access> identifier indicates that use of this URL is
+ limited to authenticated IMAP sessions that are logged in as any
+ non-anonymous user (that is, have authorization identity as a non-
+ anonymous user) of that IMAP server. To restate this: use of this
+ type of URL is prohibited to anonymous IMAP sessions, i.e., any
+ URLFETCH command containing this type of URL issued in an anonymous
+ session MUST return NIL in the URLFETCH response.
+
+ The "anonymous" <access> identifier indicates that use of this URL is
+ not restricted by session authorization identity; that is, any IMAP
+ session in authenticated or selected state (as defined in [IMAP4]),
+ including anonymous sessions, may issue a URLFETCH [URLAUTH] using
+ this URL.
+
+ The authorization token is represented as an ASCII-encoded
+ hexadecimal string, which is used to authorize the URL. The length
+ and the calculation of the authorization token depend upon the
+ mechanism used, but in all cases, the authorization token is at least
+ 128 bits (and therefore at least 32 hexadecimal digits).
+
+ Example:
+
+ <imap://joe@example.com/INBOX/;uid=20/;section=1.2;urlauth=
+ submit+fred:internal:91354a473744909de610943775f92038>
+
+7. Relative IMAP URLs
+
+ Relative IMAP URLs are permitted and are resolved according to the
+ rules defined in [URI-GEN]. In particular, in IMAP URLs parameters
+ (such as ";uid=" or ";section=") are treated as part of the normal
+ path with respect to relative URL resolution.
+
+ [URI-GEN] defines four forms of relative URLs: <inetwork-path>,
+ <iabsolute-path>, <irelative-path>, and <ipath-empty>. Their syntax
+ is defined in Section 11.
+
+ A relative reference that begins with two slash characters is termed
+ a network-path reference (<inetwork-path>); such references are
+ rarely used, because in most cases they can be replaced with an
+ equivalent absolute URL. A relative reference that begins with a
+ single slash character is termed an absolute-path reference
+ (<iabsolute-path>; see also Section 7.1). A relative reference that
+ does not begin with a slash character is termed a relative-path
+
+
+
+Melnikov & Newman Standards Track [Page 11]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ reference (<irelative-path>; see also Section 7.2). The final form
+ is <ipath-empty>, which is "same-document reference" (see Section 4.4
+ of [URI-GEN]).
+
+ The following observations about relative URLs are important:
+
+ The <iauth> grammar element (which is a part of <iuserinfo>, which
+ is, in turn, a part of <iserver>; see Section 3) is considered part
+ of the user name for purposes of resolving relative IMAP URLs. This
+ means that unless a new user name/server specification is included in
+ the relative URL, the authentication mechanism is inherited from the
+ base IMAP URL.
+
+ URLs always use "/" as the hierarchy delimiter for the purpose of
+ resolving paths in relative URLs. IMAP4 permits the use of any
+ hierarchy delimiter in mailbox names. For this reason, relative
+ mailbox paths will only work if the mailbox uses "/" as the hierarchy
+ delimiter. Relative URLs may be used on mailboxes that use other
+ delimiters, but in that case, the entire mailbox name MUST be
+ specified in the relative URL or inherited as a whole from the base
+ URL.
+
+ If an IMAP server allows for mailbox names starting with "./" or
+ "../", ending with "/." or "/..", or containing sequences "/../" or
+ "/./", then such mailbox names MUST be percent-encoded as described
+ in [URI-GEN]. Otherwise, they would be misinterpreted as dot-
+ segments (see Section 3.3 of [URI-GEN]), which are processed
+ specially during the relative path resolution process.
+
+7.1. absolute-path References
+
+ A relative reference that begins with a single slash character is
+ termed an absolute-path reference (see Section 4.2 of [URI-GEN]). If
+ an IMAP server permits mailbox names with a leading "/", then the
+ leading "/" MUST be percent-encoded as described in [URI-GEN].
+ Otherwise, the produced absolute-path reference URI will be
+ misinterpreted as a network-path reference [URI-GEN] described by the
+ <inetwork-path> non-terminal.
+
+7.2. relative-path References
+
+ A relative reference that does not begin with a slash character is
+ termed a relative-path reference [URI-GEN]. Implementations MUST NOT
+ generate or accept relative-path IMAP references.
+
+ See also Section 4.2 of [URI-GEN] for restrictions on relative-path
+ references.
+
+
+
+
+Melnikov & Newman Standards Track [Page 12]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+8. Internationalization Considerations
+
+ IMAP4, Section 5.1.3 [IMAP4] includes a convention for encoding non-
+ US-ASCII characters in IMAP mailbox names. Because this convention
+ is private to IMAP, it is necessary to convert IMAP's encoding to one
+ that can be more easily interpreted by a URL display program. For
+ this reason, IMAP's modified UTF-7 encoding for mailboxes MUST be
+ converted to UTF-8 [UTF-8]. Since 8-bit octets are not permitted in
+ URLs, the UTF-8 octets are percent-encoded as required by the URL
+ specification [URI-GEN], Section 2.1. Sample code is included in
+ Appendix A to demonstrate this conversion.
+
+ IMAP user names are UTF-8 strings and MUST be percent-encoded as
+ required by the URL specification [URI-GEN], Section 2.1.
+
+ Also note that IMAP SEARCH criteria can contain non-US-ASCII
+ characters. 8-bit octets in those strings MUST be percent-encoded as
+ required by the URL specification [URI-GEN], Section 2.1.
+
+9. Examples
+
+ The following examples demonstrate how an IMAP4 client program might
+ translate various IMAP4 URLs into a series of IMAP4 commands.
+ Commands sent from the client to the server are prefixed with "C:",
+ and responses sent from the server to the client are prefixed with
+ "S:".
+
+ The URL:
+
+ <imap://minbari.example.org/gray-council;UIDVALIDITY=385759045/;
+ UID=20/;PARTIAL=0.1024>
+
+ may result in the following client commands and server responses:
+
+ <connect to minbari.example.org, port 143>
+ S: * OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=ANONYMOUS] Welcome
+ C: A001 AUTHENTICATE ANONYMOUS
+ S: +
+ C: c2hlcmlkYW5AYmFieWxvbjUuZXhhbXBsZS5vcmc=
+ S: A001 OK Welcome sheridan@babylon5.example.org
+ C: A002 SELECT gray-council
+ <client verifies the UIDVALIDITY matches>
+ C: A003 UID FETCH 20 BODY.PEEK[]<0.1024>
+
+ The URL:
+
+ <imap://psicorp.example.org/~peter/%E6%97%A5%E6%9C%AC%E8%AA%9E/
+ %E5%8F%B0%E5%8C%97>
+
+
+
+Melnikov & Newman Standards Track [Page 13]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ may result in the following client commands:
+
+ <connect to psicorp.example.org, port 143>
+ S: * OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=CRAM-MD5] Welcome
+ C: A001 LOGIN ANONYMOUS bester@psycop.psicorp.example.org
+ C: A002 SELECT ~peter/&ZeVnLIqe-/&U,BTFw-
+ <commands the client uses for viewing the contents of
+ the mailbox>
+
+ The URL:
+
+ <imap://;AUTH=GSSAPI@minbari.example.org/gray-council/;uid=20/
+ ;section=1.2>
+
+ may result in the following client commands:
+
+ <connect to minbari.example.org, port 143>
+ S: * OK Greetings
+ C: A000 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
+ S: A000 OK
+ C: A001 AUTHENTICATE GSSAPI
+ <authentication exchange>
+ C: A002 SELECT gray-council
+ C: A003 UID FETCH 20 BODY.PEEK[1.2]
+
+ If the following relative URL is located in that body part:
+
+ <;section=1.4>
+
+ this could result in the following client commands:
+
+ C: A004 UID FETCH 20 (BODY.PEEK[1.2.MIME]
+ BODY.PEEK[1.MIME]
+ BODY.PEEK[HEADER.FIELDS (Content-Location)])
+ <Client looks for Content-Location headers in
+ result. If no such headers, then it does the following>
+ C: A005 UID FETCH 20 BODY.PEEK[1.4]
+
+ The URL:
+
+ <imap://;AUTH=*@minbari.example.org/gray%20council?
+ SUBJECT%20shadows>
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 14]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ could result in the following:
+
+ <connect to minbari.example.org, port 143>
+ S: * OK Welcome
+ C: A001 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 AUTH=DIGEST-MD5
+ S: A001 OK
+ C: A002 AUTHENTICATE DIGEST-MD5
+ <authentication exchange>
+ S: A002 OK user lennier authenticated
+ C: A003 SELECT "gray council"
+ ...
+ C: A004 SEARCH SUBJECT shadows
+ S: * SEARCH 8 10 13 14 15 16
+ S: A004 OK SEARCH completed
+ C: A005 FETCH 8,10,13:16 ALL
+ ...
+
+ In the example above, the client has implementation-dependent
+ choices. The authentication mechanism could be anything, including
+ PREAUTH. The final FETCH command could fetch more or less
+ information about the messages, depending on what it wishes to
+ display to the user.
+
+ The URL:
+
+ <imap://john;AUTH=*@minbari.example.org/babylon5/personel?
+ charset%20UTF-8%20SUBJECT%20%7B14+%7D%0D%0A%D0%98%D0%B2%
+ D0%B0%D0%BD%D0%BE%D0%B2%D0%B0>
+
+ shows that 8-bit data can be sent using non-synchronizing literals
+ [LITERAL+]. This could result in the following:
+
+ <connect to minbari.example.org, port 143>
+ S: * OK Hi there
+ C: A001 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 LITERAL+ AUTH=DIGEST-MD5
+ S: A001 OK
+ C: A002 AUTHENTICATE DIGEST-MD5
+ <authentication exchange>
+ S: A002 OK user john authenticated
+ C: A003 SELECT babylon5/personel
+ ...
+ C: A004 SEARCH CHARSET UTF-8 SUBJECT {14+}
+ C: XXXXXXXXXXXXXX
+ S: * SEARCH 7 10 12
+ S: A004 OK SEARCH completed
+ C: A005 FETCH 7,10,12 ALL
+
+
+
+Melnikov & Newman Standards Track [Page 15]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ ...
+
+ where XXXXXXXXXXXXXX is 14 bytes of UTF-8 encoded data as specified
+ in the URL above.
+
+9.1. Examples of Relative URLs
+
+ The following absolute-path reference
+
+ </foo/;UID=20/..>
+
+ is the same as
+
+ </foo>
+
+ That is, both of them reference the mailbox "foo" located on the IMAP
+ server described by the corresponding Base URI.
+
+ The following relative-path reference
+
+ <;UID=20>
+
+ references a message with UID in the mailbox specified by the Base
+ URI.
+
+ The following edge case example demonstrates that the ;UIDVALIDITY=
+ modifier is a part of the mailbox name as far as relative URI
+ resolution is concerned:
+
+ <..;UIDVALIDITY=385759045/;UID=20>
+
+ In this example, ".." is not a dot-segment [URI-GEN].
+
+10. Security Considerations
+
+ Security considerations discussed in the IMAP specification [IMAP4]
+ and the URI specification [URI-GEN] are relevant. Security
+ considerations related to authenticated URLs are discussed in Section
+ 3.2 of this document.
+
+ Many email clients store the plaintext password for later use after
+ logging into an IMAP server. Such clients MUST NOT use a stored
+ password in response to an IMAP URL without explicit permission from
+ the user to supply that password to the specified host name.
+
+ Clients resolving IMAP URLs that wish to achieve data confidentiality
+ and/or integrity SHOULD use the STARTTLS command (if supported by the
+
+
+
+
+Melnikov & Newman Standards Track [Page 16]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ server) before starting authentication, or use a SASL mechanism, such
+ as GSSAPI, that provides a confidentiality security layer.
+
+10.1. Security Consideration Specific to URLAUTH Authorized URL
+
+ The "user+<userid>" <access> identifier limits resolution of that URL
+ to a particular userid, whereas the "submit+<userid>" <access>
+ identifier is more general and simply requires that the session be
+ authorized by a user that has been granted a "submit" role within the
+ authentication system. Use of either of these mechanisms limits the
+ scope of the URL. An attacker who cannot authenticate using the
+ appropriate credentials cannot make use of the URL.
+
+ The "authuser" and "anonymous" <access> identifiers do not have this
+ level of protection. These access identifiers are primarily useful
+ for public export of data from an IMAP server, without requiring that
+ it be copied to a web or anonymous FTP server.
+
+ The decision to use the "authuser" <access> identifier should be made
+ with caution. An "authuser" <access> identifier can be used by any
+ authorized user of the IMAP server; therefore, use of this access
+ identifier should be limited to content that may be disclosed to any
+ authorized user of the IMAP server.
+
+ The decision to use the "anonymous" <access> identifier should be
+ made with extreme caution. An "anonymous" <access> identifier can be
+ used by anyone; therefore, use of this access identifier should be
+ limited to content that may be disclosed to anyone.
+
+11. ABNF for IMAP URL Scheme
+
+ Formal syntax is defined using ABNF [ABNF], extending the ABNF rules
+ in Section 9 of [IMAP4]. Elements not defined here can be found in
+ [ABNF], [IMAP4], [IMAPABNF], or [URI-GEN]. Strings are not case
+ sensitive, and free insertion of linear white space is not permitted.
+
+ sub-delims-sh = "!" / "$" / "'" / "(" / ")" /
+ "*" / "+" / ","
+ ;; Same as [URI-GEN] sub-delims,
+ ;; but without ";", "&" and "=".
+
+ uchar = unreserved / sub-delims-sh / pct-encoded
+
+ achar = uchar / "&" / "="
+ ;; Same as [URI-GEN] 'unreserved / sub-delims /
+ ;; pct-encoded', but ";" is disallowed.
+
+ bchar = achar / ":" / "@" / "/"
+
+
+
+Melnikov & Newman Standards Track [Page 17]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ enc-auth-type = 1*achar
+ ; %-encoded version of [IMAP4] "auth-type"
+
+ enc-mailbox = 1*bchar
+ ; %-encoded version of [IMAP4] "mailbox"
+
+ enc-search = 1*bchar
+ ; %-encoded version of [IMAPABNF]
+ ; "search-program". Note that IMAP4
+ ; literals may not be used in
+ ; a "search-program", i.e., only
+ ; quoted or non-synchronizing
+ ; literals (if the server supports
+ ; LITERAL+ [LITERAL+]) are allowed.
+
+ enc-section = 1*bchar
+ ; %-encoded version of [IMAP4] "section-spec"
+
+ enc-user = 1*achar
+ ; %-encoded version of [IMAP4] authorization
+ ; identity or "userid".
+
+ imapurl = "imap://" iserver ipath-query
+ ; Defines an absolute IMAP URL
+
+ ipath-query = ["/" [ icommand ]]
+ ; Corresponds to "path-abempty [ "?" query ]"
+ ; in [URI-GEN]
+
+ Generic syntax for relative URLs is defined in Section 4.2 of
+ [URI-GEN]. For ease of implementation, the relative IMAP URL syntax
+ is defined below:
+
+ imapurl-rel = inetwork-path
+
+ / iabsolute-path
+ / irelative-path
+ / ipath-empty
+
+ inetwork-path = "//" iserver ipath-query
+ ; Corresponds to '"//" authority path-abempty
+ ; [ "?" query ]' in [URI-GEN]
+
+ iabsolute-path = "/" [ icommand ]
+ ; icommand, if present, MUST NOT start with '/'.
+ ;
+ ; Corresponds to 'path-absolute [ "?" query ]'
+ ; in [URI-GEN]
+
+
+
+Melnikov & Newman Standards Track [Page 18]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ irelative-path = imessagelist /
+ imsg-or-part
+ ; Corresponds to 'path-noscheme [ "?" query ]'
+ ; in [URI-GEN]
+
+ imsg-or-part = ( imailbox-ref "/" iuid-only ["/" isection-only]
+ ["/" ipartial-only] ) /
+ ( iuid-only ["/" isection-only]
+ ["/" ipartial-only] ) /
+ ( isection-only ["/" ipartial-only] ) /
+ ipartial-only
+
+ ipath-empty = 0<pchar>
+ ; Zero characters.
+ ; The same-document reference.
+
+ The following three rules are only used in the presence of the IMAP
+ [URLAUTH] extension:
+
+ authimapurl = "imap://" iserver "/" imessagepart
+ ; Same as "imapurl" when "[icommand]" is
+ ; "imessagepart"
+
+ authimapurlfull = authimapurl iurlauth
+ ; Same as "imapurl" when "[icommand]" is
+ ; "imessagepart iurlauth"
+
+ authimapurlrump = authimapurl iurlauth-rump
+
+
+ enc-urlauth = 32*HEXDIG
+
+ iurlauth = iurlauth-rump iua-verifier
+
+ iua-verifier = ":" uauth-mechanism ":" enc-urlauth
+
+ iurlauth-rump = [expire] ";URLAUTH=" access
+
+ access = ("submit+" enc-user) / ("user+" enc-user) /
+ "authuser" / "anonymous"
+
+ expire = ";EXPIRE=" date-time
+ ; date-time is defined in [DATETIME]
+
+ uauth-mechanism = "INTERNAL" / 1*(ALPHA / DIGIT / "-" / ".")
+ ; Case-insensitive.
+ ; New mechanisms MUST be registered with IANA.
+
+
+
+
+Melnikov & Newman Standards Track [Page 19]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ iauth = ";AUTH=" ( "*" / enc-auth-type )
+
+ icommand = imessagelist /
+ imessagepart [iurlauth]
+
+ imailbox-ref = enc-mailbox [uidvalidity]
+
+ imessagelist = imailbox-ref [ "?" enc-search ]
+ ; "enc-search" is [URI-GEN] "query".
+
+ imessagepart = imailbox-ref iuid [isection] [ipartial]
+
+ ipartial = "/" ipartial-only
+
+ ipartial-only = ";PARTIAL=" partial-range
+
+ isection = "/" isection-only
+
+ isection-only = ";SECTION=" enc-section
+
+ iserver = [iuserinfo "@"] host [ ":" port ]
+ ; This is the same as "authority" defined
+ ; in [URI-GEN]. See [URI-GEN] for "host"
+ ; and "port" definitions.
+
+ iuid = "/" iuid-only
+
+ iuid-only = ";UID=" nz-number
+ ; See [IMAP4] for "nz-number" definition
+
+ iuserinfo = enc-user [iauth] / [enc-user] iauth
+ ; conforms to the generic syntax of
+ ; "userinfo" as defined in [URI-GEN].
+
+ partial-range = number ["." nz-number]
+ ; partial FETCH. The first number is
+ ; the offset of the first byte,
+ ; the second number is the length of
+ ; the fragment.
+
+ uidvalidity = ";UIDVALIDITY=" nz-number
+ ; See [IMAP4] for "nz-number" definition
+
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 20]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+12. IANA Considerations
+
+ IANA has updated the "imap" definition in the "Uniform Resource
+ Identifier scheme registry" to point to this document.
+
+ The registration template (as per [URI-REG]) is specified in Section
+ 12.1 of this document.
+
+12.1. IANA Registration of imap: URI Scheme
+
+ This section provides the information required to register the imap:
+ URI scheme.
+
+ URI scheme name: imap
+
+ Status: permanent
+
+ URI scheme syntax:
+
+ See Section 11 of [RFC5092].
+
+ URI scheme semantics:
+
+ The imap: URI scheme is used to designate IMAP servers, mailboxes,
+ messages, MIME bodies [MIME] and their parts, and search programs
+ on Internet hosts accessible using the IMAP protocol.
+
+ There is no MIME type associated with this URI.
+
+ Encoding considerations:
+
+ See Section 8 of [RFC5092].
+
+ Applications/protocols that use this URI scheme name:
+
+ The imap: URI is intended to be used by applications that might
+ need access to an IMAP mailstore. Such applications may include
+ (but are not limited to) IMAP-capable web browsers; IMAP clients
+ that wish to access a mailbox, message, or edit a message on the
+ server using [CATENATE]; [SUBMIT] clients and servers that are
+ requested to assemble a complete message on submission using
+ [BURL].
+
+ Interoperability considerations:
+
+ A widely deployed IMAP client Netscape Mail (and possibly
+ Mozilla/Thunderbird/Seamonkey) uses a different imap: scheme
+ internally.
+
+
+
+Melnikov & Newman Standards Track [Page 21]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ Security considerations:
+
+ See Security Considerations (Section 10) of [RFC5092].
+
+ Contact:
+
+ Alexey Melnikov <alexey.melnikov@isode.com>
+
+ Author/Change controller:
+
+ IESG
+
+ References:
+
+ [RFC5092] and [IMAP4].
+
+13. References
+
+13.1. Normative References
+
+ [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [IMAP4] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to
+ IMAP4 ABNF", RFC 4466, April 2006.
+
+ [ABNF] Crocker, D., Ed., and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 4234, October 2005.
+
+ [MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+ Extensions (MIME) Part One: Format of Internet Message
+ Bodies", RFC 2045, November 1996.
+
+ [URI-GEN] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+ Resource Identifier (URI): Generic Syntax", STD 66, RFC
+ 3986, January 2005.
+
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", STD 63, RFC 3629, November 2003.
+
+ [NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
+ May 1998.
+
+ [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
+ January 1997.
+
+
+
+Melnikov & Newman Standards Track [Page 22]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ [ANONYMOUS] Zeilenga, K., "Anonymous Simple Authentication and
+ Security Layer (SASL) Mechanism", RFC 4505, June 2006.
+
+ [DATETIME] Klyne, G. and C. Newman, "Date and Time on the Internet:
+ Timestamps", RFC 3339, July 2002.
+
+ [URLAUTH] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ URLAUTH Extension", RFC 4467, May 2006.
+
+13.2. Informative References
+
+ [SUBMIT] Gellens, R. and J. Klensin, "Message Submission for
+ Mail", RFC 4409, April 2006.
+
+ [BURL] Newman, C., "Message Submission BURL Extension", RFC
+ 4468, May 2006.
+
+ [CATENATE] Resnick, P., "Internet Message Access Protocol (IMAP)
+ CATENATE Extension", RFC 4469, April 2006.
+
+ [SASL] Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
+ Authentication and Security Layer (SASL)", RFC 4422,
+ June 2006.
+
+ [GSSAPI] Melnikov, A., Ed., "The Kerberos V5 ("GSSAPI") Simple
+ Authentication and Security Layer (SASL) Mechanism", RFC
+ 4752, November 2006.
+
+ [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication as
+ a SASL Mechanism", RFC 2831, May 2000.
+
+ [URI-REG] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
+ Registration Procedures for New URI Schemes", BCP 115,
+ RFC 4395, February 2006.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 23]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+Appendix A. Sample Code
+
+ Here is sample C source code to convert between URL paths and IMAP
+ mailbox names, taking into account mapping between IMAP's modified
+ UTF-7 [IMAP4] and hex-encoded UTF-8, which is more appropriate for
+ URLs. This code has not been rigorously tested nor does it
+ necessarily behave reasonably with invalid input, but it should serve
+ as a useful example. This code just converts the mailbox portion of
+ the URL and does not deal with parameters, query, or server
+ components of the URL.
+
+/* Copyright (C) The IETF Trust (2007). This version of
+ sample C code is part of RFC XXXX; see the RFC itself
+ for full legal notices.
+
+ Regarding this sample C code (or any portion of it), the authors
+ make no guarantees and are not responsible for any damage
+ resulting from its use. The authors grant irrevocable permission
+ to anyone to use, modify, and distribute it in any way that does
+ not diminish the rights of anyone else to use, modify, and
+ distribute it, provided that redistributed derivative works do
+ not contain misleading author or version information.
+
+ Derivative works need not be licensed under similar terms.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+/* hexadecimal lookup table */
+static const char hex[] = "0123456789ABCDEF";
+
+#define XX 127
+/*
+ * Table for decoding hexadecimal in %encoding
+ */
+static const char index_hex[256] = {
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,XX,XX, XX,XX,XX,XX,
+ XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,10,11,12, 13,14,15,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+
+
+
+Melnikov & Newman Standards Track [Page 24]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+ XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
+};
+#define HEXCHAR(c) (index_hex[(unsigned char)(c)])
+
+/* "gen-delims" excluding "/" but including "%" */
+#define GENERAL_DELIMS_NO_SLASH ":?#[]@" "%"
+
+/* "gen-delims" (excluding "/", but including "%")
+ plus subset of "sub-delims" */
+#define GENERAL_UNSAFE_NO_SLASH GENERAL_DELIMS_NO_SLASH ";&=+"
+#define OTHER_UNSAFE " \"<>\\^`{|}"
+
+/* URL unsafe printable characters */
+static const char mailbox_url_unsafe[] = GENERAL_UNSAFE_NO_SLASH
+ OTHER_UNSAFE;
+
+/* UTF7 modified base64 alphabet */
+static const char base64chars[] =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
+
+#define UNDEFINED 64
+
+/* UTF16 definitions */
+#define UTF16MASK 0x03FFUL
+#define UTF16SHIFT 10
+#define UTF16BASE 0x10000UL
+#define UTF16HIGHSTART 0xD800UL
+#define UTF16HIGHEND 0xDBFFUL
+#define UTF16LOSTART 0xDC00UL
+#define UTF16LOEND 0xDFFFUL
+
+/* Convert an IMAP mailbox to a URL path
+ * dst needs to have roughly 4 times the storage space of src
+ * Hex encoding can triple the size of the input
+ * UTF-7 can be slightly denser than UTF-8
+ * (worst case: 8 octets UTF-7 becomes 9 octets UTF-8)
+ */
+void MailboxToURL(char *dst, char *src)
+{
+ unsigned char c, i, bitcount;
+ unsigned long ucs4, utf16, bitbuf;
+ unsigned char base64[256], utf8[6];
+
+ /* initialize modified base64 decoding table */
+
+
+
+Melnikov & Newman Standards Track [Page 25]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ memset(base64, UNDEFINED, sizeof (base64));
+ for (i = 0; i < sizeof (base64chars); ++i) {
+ base64[(int) base64chars[i]] = i;
+ }
+
+ /* loop until end of string */
+ while (*src != '\0') {
+ c = *src++;
+ /* deal with literal characters and &- */
+ if (c != '&' || *src == '-') {
+ /* NB: There are no "URL safe" characters after the '~' */
+ if (c < ' ' || c > '~' ||
+ strchr(mailbox_url_unsafe, c) != NULL) {
+ /* hex encode if necessary */
+ dst[0] = '%';
+ dst[1] = hex[c >> 4];
+ dst[2] = hex[c & 0x0f];
+ dst += 3;
+ } else {
+ /* encode literally */
+ *dst++ = c;
+ }
+ /* skip over the '-' if this is an &- sequence */
+ if (c == '&') ++src;
+
+ } else {
+ /* convert modified UTF-7 -> UTF-16 -> UCS-4 -> UTF-8 -> HEX */
+ bitbuf = 0;
+ bitcount = 0;
+ ucs4 = 0;
+ while ((c = base64[(unsigned char) *src]) != UNDEFINED) {
+ ++src;
+ bitbuf = (bitbuf << 6) | c;
+ bitcount += 6;
+ /* enough bits for a UTF-16 character? */
+ if (bitcount >= 16) {
+ bitcount -= 16;
+ utf16 = (bitcount ? bitbuf >> bitcount
+ : bitbuf) & 0xffff;
+ /* convert UTF16 to UCS4 */
+ if
+ (utf16 >= UTF16HIGHSTART && utf16 <= UTF16HIGHEND) {
+ ucs4 = (utf16 - UTF16HIGHSTART) << UTF16SHIFT;
+ continue;
+ } else if
+ (utf16 >= UTF16LOSTART && utf16 <= UTF16LOEND) {
+ ucs4 += utf16 - UTF16LOSTART + UTF16BASE;
+ } else {
+
+
+
+Melnikov & Newman Standards Track [Page 26]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ ucs4 = utf16;
+ }
+ /* convert UTF-16 range of UCS4 to UTF-8 */
+ if (ucs4 <= 0x7fUL) {
+ utf8[0] = (unsigned char) ucs4;
+ i = 1;
+ } else if (ucs4 <= 0x7ffUL) {
+ utf8[0] = 0xc0 | (unsigned char) (ucs4 >> 6);
+ utf8[1] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+ i = 2;
+ } else if (ucs4 <= 0xffffUL) {
+ utf8[0] = 0xe0 | (unsigned char) (ucs4 >> 12);
+ utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
+ utf8[2] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+ i = 3;
+ } else {
+ utf8[0] = 0xf0 | (unsigned char) (ucs4 >> 18);
+ utf8[1] = 0x80 | (unsigned char) ((ucs4 >> 12) & 0x3f);
+ utf8[2] = 0x80 | (unsigned char) ((ucs4 >> 6) & 0x3f);
+ utf8[3] = 0x80 | (unsigned char) (ucs4 & 0x3f);
+ i = 4;
+ }
+ /* convert utf8 to hex */
+ for (c = 0; c < i; ++c) {
+ dst[0] = '%';
+ dst[1] = hex[utf8[c] >> 4];
+ dst[2] = hex[utf8[c] & 0x0f];
+ dst += 3;
+ }
+ }
+ }
+ /* skip over trailing '-' in modified UTF-7 encoding */
+ if (*src == '-') ++src;
+ }
+ }
+ /* terminate destination string */
+ *dst = '\0';
+}
+
+/* Convert hex coded UTF-8 URL path to modified UTF-7 IMAP mailbox
+ * dst should be about twice the length of src to deal with non-hex
+ * coded URLs
+ */
+int URLtoMailbox(char *dst, char *src)
+{
+ unsigned int utf8pos = 0;
+ unsigned int utf8total, i, c, utf7mode, bitstogo, utf16flag;
+ unsigned long ucs4 = 0, bitbuf = 0;
+
+
+
+Melnikov & Newman Standards Track [Page 27]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ utf7mode = 0; /* is the output UTF7 currently in base64 mode? */
+ utf8total = 0; /* how many octets is the current input UTF-8 char;
+ 0 == between characters */
+ bitstogo = 0; /* bits that need to be encoded into base64; if
+ bitstogo != 0 then utf7mode == 1 */
+ while ((c = (unsigned char)*src) != '\0') {
+ ++src;
+ /* undo hex-encoding */
+ if (c == '%' && src[0] != '\0' && src[1] != '\0') {
+ c = HEXCHAR(src[0]);
+ i = HEXCHAR(src[1]);
+ if (c == XX || i == XX) {
+ return 0;
+ } else {
+ c = (char)((c << 4) | i);
+ }
+ src += 2;
+ }
+ /* normal character? */
+ if (c >= ' ' && c <= '~') {
+ /* switch out of UTF-7 mode */
+ if (utf7mode) {
+ if (bitstogo) {
+ *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
+ }
+ *dst++ = '-';
+ utf7mode = 0;
+ bitstogo = bitbuf = 0;
+ }
+ *dst++ = c;
+ /* encode '&' as '&-' */
+ if (c == '&') {
+ *dst++ = '-';
+ }
+ continue;
+ }
+ /* switch to UTF-7 mode */
+ if (!utf7mode) {
+ *dst++ = '&';
+ utf7mode = 1;
+ }
+ /* Encode US-ASCII characters as themselves */
+ if (c < 0x80) {
+ ucs4 = c;
+ utf8total = 1;
+ } else if (utf8total) {
+ /* this is a subsequent octet of a multi-octet character */
+ /* save UTF8 bits into UCS4 */
+
+
+
+Melnikov & Newman Standards Track [Page 28]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ ucs4 = (ucs4 << 6) | (c & 0x3FUL);
+ if (++utf8pos < utf8total) {
+ continue;
+ }
+ } else {
+ /* this is the first octet of a multi-octet character */
+ utf8pos = 1;
+ if (c < 0xE0) {
+ utf8total = 2;
+ ucs4 = c & 0x1F;
+ } else if (c < 0xF0) {
+ utf8total = 3;
+ ucs4 = c & 0x0F;
+ } else {
+ /* NOTE: can't convert UTF8 sequences longer than 4 */
+ utf8total = 4;
+ ucs4 = c & 0x03;
+ }
+ continue;
+ }
+ /* Finished with UTF-8 character. Make sure it isn't an
+ overlong sequence. If it is, return failure. */
+ if ((ucs4 < 0x80 && utf8total > 1) ||
+ (ucs4 < 0x0800 && utf8total > 2) ||
+ (ucs4 < 0x00010000 && utf8total > 3) ||
+ (ucs4 < 0x00200000 && utf8total > 4) ||
+ (ucs4 < 0x04000000 && utf8total > 5) ||
+ (ucs4 < 0x80000000 && utf8total > 6)) {
+ return 0;
+ }
+ /* loop to split ucs4 into two utf16 chars if necessary */
+ utf8total = 0;
+ do {
+ if (ucs4 >= UTF16BASE) {
+ ucs4 -= UTF16BASE;
+ bitbuf = (bitbuf << 16) | ((ucs4 >> UTF16SHIFT)
+ + UTF16HIGHSTART);
+ ucs4 = (ucs4 & UTF16MASK) + UTF16LOSTART;
+ utf16flag = 1;
+ } else {
+ bitbuf = (bitbuf << 16) | ucs4;
+ utf16flag = 0;
+ }
+ bitstogo += 16;
+ /* spew out base64 */
+ while (bitstogo >= 6) {
+ bitstogo -= 6;
+ *dst++ = base64chars[(bitstogo ? (bitbuf >> bitstogo)
+
+
+
+Melnikov & Newman Standards Track [Page 29]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+ : bitbuf)
+ & 0x3F];
+ }
+ } while (utf16flag);
+ }
+ /* if in UTF-7 mode, finish in ASCII */
+ if (utf7mode) {
+ if (bitstogo) {
+ *dst++ = base64chars[(bitbuf << (6 - bitstogo)) & 0x3F];
+ }
+ *dst++ = '-';
+ }
+ /* tie off string */
+ *dst = '\0';
+ return 1;
+}
+
+Appendix B. List of Changes since RFC 2192
+
+ Updated boilerplate, list of editor's, etc.
+ Updated references.
+ Updated ABNF not to use _, to use SP instead of SPACE, etc.
+ Updated example domains to use example.org.
+ Fixed ABNF error in "imessagelist" non-terminal.
+ Updated ABNF, due to changes in RFC 3501, RFC 4466, and RFC 3986.
+ Renamed "iuserauth" non-terminal to <iuserinfo>.
+ Clarified that the userinfo component describes both authorization
+ identity and mailbox naming scope.
+ Allow for non-synchronizing literals in "enc-search".
+ Added "ipartial" specifier that denotes a partial FETCH.
+ Moved URLAUTH text from RFC 4467 to this document.
+ Updated ABNF for the whole server to allow missing trailing "/"
+ (e.g., "imap://imap.example.com" is now valid and is the same as
+ "imap://imap.example.com/").
+ Clarified how relative-path references are constructed.
+ Added more examples demonstrating relative-path references.
+ Added rules for relative URLs and restructured ABNF as the result.
+ Removed text on use of relative URLs in MHTML.
+ Added examples demonstrating security considerations when resolving
+ URLs.
+ Recommend usage of STARTTLS/SASL security layer to protect
+ confidential data.
+ Removed some advices about connection reuse that were incorrect.
+ Removed URLs referencing a list of mailboxes, as this feature
+ hasn't seen any deployments.
+ Clarified that user name "anonymous" is case-insensitive.
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 30]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+Appendix C. List of Changes since RFC 4467
+
+ Renamed <mechanism> to <uauth-mechanism>. Restructured ABNF.
+
+Appendix D. Acknowledgments
+
+ Text describing URLAUTH was lifted from [URLAUTH] by Mark Crispin.
+
+ Stephane H. Maes contributed some ideas to this document; he also
+ co-edited early versions of this document.
+
+ The editors would like to thank Mark Crispin, Ken Murchison, Ted
+ Hardie, Zoltan Ordogh, Dave Cridland, Kjetil Torgrim Homme, Lisa
+ Dusseault, Spencer Dawkins, Filip Navara, Shawn M. Emery, Sam
+ Hartman, Russ Housley, and Lars Eggert for the time they devoted to
+ reviewing this document and/or for the comments received.
+
+Authors' Addresses
+
+ Chris Newman (Author/Editor)
+ Sun Microsystems
+ 3401 Centrelake Dr., Suite 410
+ Ontario, CA 91761
+ EMail: chris.newman@sun.com
+
+ Alexey Melnikov (Editor)
+ Isode Limited
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex
+ TW12 2BX, UK
+ EMail: Alexey.Melnikov@isode.com
+ URI: http://www.melnikov.ca/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 31]
+
+RFC 5092 IMAP URL Scheme November 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov & Newman Standards Track [Page 32]
+
diff --git a/imap/docs/rfc/rfc5161.txt b/imap/docs/rfc/rfc5161.txt
new file mode 100644
index 00000000..13bbbf74
--- /dev/null
+++ b/imap/docs/rfc/rfc5161.txt
@@ -0,0 +1,395 @@
+
+
+
+
+
+
+Network Working Group A. Gulbrandsen, Ed.
+Request for Comments: 5161 Oryx Mail Systems GmbH
+Category: Standards Track A. Melnikov, Ed.
+ Isode Limited
+ March 2008
+
+
+ The IMAP ENABLE Extension
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ Most IMAP extensions are used by the client when it wants to and the
+ server supports it. However, a few extensions require the server to
+ know whether a client supports that extension. The ENABLE extension
+ allows an IMAP client to say which extensions it supports.
+
+1. Overview
+
+ Several IMAP extensions allow the server to return unsolicited
+ responses specific to these extensions in certain circumstances.
+ However, servers cannot send those unsolicited responses until they
+ know that the clients support such extensions and thus won't choke on
+ the extension response data.
+
+ Up until now, extensions have typically stated that a server cannot
+ send the unsolicited responses until after the client has used a
+ command with the extension data (i.e., at that point the server knows
+ the client is aware of the extension). CONDSTORE ([RFC4551]),
+ ANNOTATE ([ANNOTATE]), and some extensions under consideration at the
+ moment use various commands to enable server extensions. For
+ example, CONDSTORE uses a SELECT or FETCH parameter, and ANNOTATE
+ uses a side effect of FETCH.
+
+ The ENABLE extension provides an explicit indication from the client
+ that it supports particular extensions. This is done using a new
+ ENABLE command.
+
+ An IMAP server that supports ENABLE advertises this by including the
+ word ENABLE in its capability list.
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 1]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+ Most IMAP extensions do not require the client to enable the
+ extension in any way.
+
+2. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC2119].
+
+ Formal syntax is defined by [RFC5234] and [RFC3501].
+
+ Example lines prefaced by "C:" are sent by the client and ones
+ prefaced by "S:" by the server. The five characters [...] means that
+ something has been elided.
+
+3. Protocol Changes
+
+3.1. The ENABLE Command
+
+ Arguments: capability names
+
+ Result: OK: Relevant capabilities enabled
+ BAD: No arguments, or syntax error in an argument
+
+ The ENABLE command takes a list of capability names, and requests the
+ server to enable the named extensions. Once enabled using ENABLE,
+ each extension remains active until the IMAP connection is closed.
+ For each argument, the server does the following:
+
+ - If the argument is not an extension known to the server, the server
+ MUST ignore the argument.
+
+ - If the argument is an extension known to the server, and it is not
+ specifically permitted to be enabled using ENABLE, the server MUST
+ ignore the argument. (Note that knowing about an extension doesn't
+ necessarily imply supporting that extension.)
+
+ - If the argument is an extension that is supported by the server and
+ that needs to be enabled, the server MUST enable the extension for
+ the duration of the connection. At present, this applies only to
+ CONDSTORE ([RFC4551]). Note that once an extension is enabled,
+ there is no way to disable it.
+
+ If the ENABLE command is successful, the server MUST send an untagged
+ ENABLED response (see Section 3.2).
+
+
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 2]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+ Clients SHOULD only include extensions that need to be enabled by the
+ server. At the time of publication, CONDSTORE is the only such
+ extension (i.e., ENABLE CONDSTORE is an additional "CONDSTORE
+ enabling command" as defined in [RFC4551]). Future RFCs may add to
+ this list.
+
+ The ENABLE command is only valid in the authenticated state (see
+ [RFC3501]), before any mailbox is selected. Clients MUST NOT issue
+ ENABLE once they SELECT/EXAMINE a mailbox; however, server
+ implementations don't have to check that no mailbox is selected or
+ was previously selected during the duration of a connection.
+
+ The ENABLE command can be issued multiple times in a session. It is
+ additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a
+ single command "ENABLE a b c". When multiple ENABLE commands are
+ issued, each corresponding ENABLED response SHOULD only contain
+ extensions enabled by the corresponding ENABLE command.
+
+ There are no limitations on pipelining ENABLE. For example, it is
+ possible to send ENABLE and then immediately SELECT, or a LOGIN
+ immediately followed by ENABLE.
+
+ The server MUST NOT change the CAPABILITY list as a result of
+ executing ENABLE; i.e., a CAPABILITY command issued right after an
+ ENABLE command MUST list the same capabilities as a CAPABILITY
+ command issued before the ENABLE command. This is demonstrated in
+ the following example:
+
+ C: t1 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA
+ S: t1 OK foo
+ C: t2 ENABLE CONDSTORE X-GOOD-IDEA
+ S: * ENABLED X-GOOD-IDEA
+ S: t2 OK foo
+ C: t3 CAPABILITY
+ S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA
+ S: t3 OK foo again
+
+ In the following example, the client enables CONDSTORE:
+
+ C: a1 ENABLE CONDSTORE
+ S: * ENABLED CONDSTORE
+ S: a1 OK Conditional Store enabled
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 3]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+3.2. The ENABLED Response
+
+ Contents: capability listing
+
+ The ENABLED response occurs as a result of an ENABLE command. The
+ capability listing contains a space-separated listing of capability
+ names that the server supports and that were successfully enabled.
+ The ENABLED response may contain no capabilities, which means that no
+ extensions listed by the client were successfully enabled.
+
+3.3. Note to Designers of Extensions That May Use the ENABLE Command
+
+ Designers of IMAP extensions are discouraged from creating extensions
+ that require ENABLE unless there is no good alternative design.
+ Specifically, extensions that cause potentially incompatible behavior
+ changes to deployed server responses (and thus benefit from ENABLE)
+ have a higher complexity cost than extensions that do not.
+
+4. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [RFC5234] including the core
+ rules in Appendix B.1. [RFC3501] defines the non-terminals
+ "capability" and "command-any".
+
+ Except as noted otherwise, all alphabetic characters are
+ case-insensitive. The use of upper or lower case characters to
+ define token strings is for editorial clarity only. Implementations
+ MUST accept these strings in a case-insensitive fashion.
+
+ capability =/ "ENABLE"
+
+ command-any =/ "ENABLE" 1*(SP capability)
+
+ response-data =/ "*" SP enable-data CRLF
+
+ enable-data = "ENABLED" *(SP capability)
+
+5. Security Considerations
+
+ It is believed that this extension doesn't add any security
+ considerations that are not already present in the base IMAP protocol
+ [RFC3501].
+
+6. IANA Considerations
+
+ The IANA has added ENABLE to the IMAP4 Capabilities Registry.
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 4]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+7. Acknowledgments
+
+ The editors would like to thank Randy Gellens, Chris Newman, Peter
+ Coates, Dave Cridland, Mark Crispin, Ned Freed, Dan Karp, Cyrus
+ Daboo, Ken Murchison, and Eric Burger for comments and corrections.
+ However, this doesn't necessarily mean that they endorse this
+ extension, agree with all details, or are responsible for errors
+ introduced by the editors.
+
+8. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", STD 68, RFC 5234, January
+ 2008.
+
+ [RFC4551] Melnikov, A. and S. Hole, "IMAP Extension for Conditional
+ STORE Operation or Quick Flag Changes Resynchronization",
+ RFC 4551, June 2006.
+
+9. Informative References
+
+ [ANNOTATE] Daboo, C. and R. Gellens, "IMAP ANNOTATE Extension", Work
+ in Progress, August 2006.
+
+
+
+
+
+
+
+
+
+
+
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+
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 5]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+Editors' Addresses
+
+ Arnt Gulbrandsen
+ Oryx Mail Systems GmbH
+ Schweppermannstr. 8
+ D-81671 Muenchen
+ Germany
+
+ Fax: +49 89 4502 9758
+ EMail: arnt@oryx.com
+
+
+ Alexey Melnikov
+ Isode Ltd
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+
+
+
+
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+
+Gulbrandsen & Melnikov Standards Track [Page 6]
+
+RFC 5161 The IMAP ENABLE Extension March 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Gulbrandsen & Melnikov Standards Track [Page 7]
+
diff --git a/imap/docs/rfc/rfc5162.txt b/imap/docs/rfc/rfc5162.txt
new file mode 100644
index 00000000..305c54fb
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+++ b/imap/docs/rfc/rfc5162.txt
@@ -0,0 +1,1291 @@
+
+
+
+
+
+
+Network Working Group A. Melnikov
+Request for Comments: 5162 D. Cridland
+Category: Standards Track Isode Ltd
+ C. Wilson
+ Nokia
+ March 2008
+
+
+ IMAP4 Extensions for Quick Mailbox Resynchronization
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ This document defines an IMAP4 extension, which gives an IMAP client
+ the ability to quickly resynchronize any previously opened mailbox as
+ part of the SELECT command, without the need for server-side state or
+ additional client round-trips. This extension also introduces a new
+ response that allows for a more compact representation of a list of
+ expunged messages (and always includes the Unique Identifiers (UIDs)
+ expunged).
+
+
+
+
+
+
+
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+
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+
+Melnikov, et al. Standards Track [Page 1]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+Table of Contents
+
+ 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 2
+ 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
+ 3. IMAP Protocol Changes . . . . . . . . . . . . . . . . . . . . 4
+ 3.1. QRESYNC Parameter to SELECT/EXAMINE . . . . . . . . . . . 4
+ 3.2. VANISHED UID FETCH Modifier . . . . . . . . . . . . . . . 8
+ 3.3. EXPUNGE Command . . . . . . . . . . . . . . . . . . . . . 10
+ 3.4. CLOSE Command . . . . . . . . . . . . . . . . . . . . . . 11
+ 3.5. UID EXPUNGE Command . . . . . . . . . . . . . . . . . . . 11
+ 3.6. VANISHED Response . . . . . . . . . . . . . . . . . . . . 12
+ 3.7. CLOSED Response Code . . . . . . . . . . . . . . . . . . . 15
+ 4. Server Implementation Considerations . . . . . . . . . . . . . 15
+ 4.1. Server Implementations That Don't Store Extra State . . . 15
+ 4.2. Server Implementations Storing Minimal State . . . . . . . 16
+ 4.3. Additional State Required on the Server . . . . . . . . . 16
+ 5. Updated Synchronization Sequence . . . . . . . . . . . . . . . 17
+ 6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 19
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
+ 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
+ 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
+ 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
+ 10.1. Normative References . . . . . . . . . . . . . . . . . . . 21
+ 10.2. Informative References . . . . . . . . . . . . . . . . . . 22
+
+1. Introduction and Overview
+
+ The [CONDSTORE] extension gives a disconnected client the ability to
+ quickly resynchronize IMAP flag changes for previously seen messages.
+ This can be done using the CHANGEDSINCE FETCH modifier once a mailbox
+ is opened. In order for the client to discover which messages have
+ been expunged, the client still has to issue a UID FETCH or a UID
+ SEARCH command. This document defines an extension to [CONDSTORE]
+ that allows a reconnecting client to perform full resynchronization,
+ including discovery of expunged messages, in a single round-trip.
+ This extension also introduces a new response, VANISHED, that allows
+ for a more compact representation of a list of expunged messages.
+
+ This extension can be useful for mobile clients that can experience
+ frequent disconnects caused by environmental factors (battery life,
+ signal strength, etc.). Such clients need a way to quickly reconnect
+ to the IMAP server, while minimizing delay experienced by the user as
+ well as the amount of traffic (and hence the expense) generated by
+ resynchronization.
+
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 2]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ By extending the SELECT command to perform the additional
+ resynchronization, this also allows clients to reduce concurrent
+ connections to the IMAP server held purely for the sake of avoiding
+ the resynchronization.
+
+ The quick resync IMAP extension is present if an IMAP4 server returns
+ "QRESYNC" as one of the supported capabilities to the CAPABILITY
+ command.
+
+ Servers supporting this extension MUST implement and advertise
+ support for the [ENABLE] IMAP extension. Also, the presence of the
+ "QRESYNC" capability implies support for the [CONDSTORE] IMAP
+ extension even if the CONDSTORE capability isn't advertised. A
+ server compliant with this specification is REQUIREd to support
+ "ENABLE QRESYNC" and "ENABLE QRESYNC CONDSTORE" (which are "CONDSTORE
+ enabling commands", as defined in [CONDSTORE], and have identical
+ results), but there is no requirement for a compliant server to
+ support "ENABLE CONDSTORE" by itself. The "ENABLE QRESYNC"/"ENABLE
+ QRESYNC CONDSTORE" command also tells the server that it SHOULD start
+ sending VANISHED responses (see Section 3.6) instead of EXPUNGE
+ responses. This change remains in effect until the connection is
+ closed.
+
+ For compatibility with clients that only support the [CONDSTORE] IMAP
+ extension, servers SHOULD advertise CONDSTORE in the CAPABILITY
+ response as well.
+
+ A client making use of this extension MUST issue "ENABLE QRESYNC"
+ once it is authenticated. A server MUST respond with a tagged BAD
+ response if the QRESYNC parameter to the SELECT/EXAMINE command or
+ the VANISHED UID FETCH modifier is specified and the client hasn't
+ issued "ENABLE QRESYNC" in the current connection.
+
+ This document puts additional requirements on a server implementing
+ the [CONDSTORE] extension. Each mailbox that supports persistent
+ storage of mod-sequences, i.e., for which the server has sent a
+ HIGHESTMODSEQ untagged OK response code on a successful SELECT/
+ EXAMINE, MUST increment the per-mailbox mod-sequence when one or more
+ messages are expunged due to EXPUNGE, UID EXPUNGE or CLOSE; the
+ server MUST associate the incremented mod-sequence with the UIDs of
+ the expunged messages.
+
+ A client that supports CONDSTORE but not this extension might
+ resynchronize a mailbox and discover that its HIGHESTMODSEQ has
+ increased from the value cached by the client. If the increase is
+ only due to messages having been expunged since the client last
+ synchronized, the client is likely to send a FETCH ... CHANGEDSINCE
+ command that returns no data. Thus, a client that supports CONDSTORE
+
+
+
+Melnikov, et al. Standards Track [Page 3]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ but not this extension might incur a penalty of an unneeded round-
+ trip when resynchronizing some mailboxes (those that have had
+ messages expunged but no flag changes since the last
+ synchronization).
+
+ This extra round-trip is only incurred by clients that support
+ CONDSTORE but not this extension, and only when a mailbox has had
+ messages expunged but no flag changes to non-expunged messages.
+ Since CONDSTORE is a relatively new extension, it is thought likely
+ that clients that support it will also support this extension.
+
+2. Requirements Notation
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in [RFC2119].
+
+ In examples, "C:" and "S:" indicate lines sent by the client and
+ server respectively. If a single "C:" or "S:" label applies to
+ multiple lines, then the line breaks between those lines are for
+ editorial clarity only and are not part of the actual protocol
+ exchange. The five characters [...] means that something has been
+ elided.
+
+ Understanding of the IMAP message sequence numbers and UIDs and the
+ EXPUNGE response [RFC3501] is essential when reading this document.
+
+3. IMAP Protocol Changes
+
+3.1. QRESYNC Parameter to SELECT/EXAMINE
+
+ The Quick Resynchronization parameter to SELECT/EXAMINE commands has
+ four arguments:
+
+ o the last known UIDVALIDITY,
+
+ o the last known modification sequence,
+
+ o the optional set of known UIDs, and
+
+ o an optional parenthesized list of known sequence ranges and their
+ corresponding UIDs.
+
+ A server MUST respond with a tagged BAD response if the Quick
+ Resynchronization parameter to SELECT/EXAMINE command is specified
+ and the client hasn't issued "ENABLE QRESYNC" in the current
+ connection.
+
+
+
+
+Melnikov, et al. Standards Track [Page 4]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Before opening the specified mailbox, the server verifies all
+ arguments for syntactic validity. If any parameter is not
+ syntactically valid, the server returns the tagged BAD response, and
+ the mailbox remains unselected. Once the check is done, the server
+ opens the mailbox as if no SELECT/EXAMINE parameters are specified
+ (this is subject to processing of other parameters as defined in
+ other extensions). In particular this means that the server MUST
+ send all untagged responses as specified in Sections 6.3.1 and 6.3.2
+ of [RFC3501].
+
+ After that, the server checks the UIDVALIDITY value provided by the
+ client. If the provided UIDVALIDITY doesn't match the UIDVALIDITY
+ for the mailbox being opened, then the server MUST ignore the
+ remaining parameters and behave as if no dynamic message data
+ changed. The client can discover this situation by comparing the
+ UIDVALIDITY value returned by the server. This behavior allows the
+ client not to synchronize the mailbox or decide on the best
+ synchronization strategy.
+
+ Example: Attempting to resynchronize INBOX, but the provided
+ UIDVALIDITY parameter doesn't match the current UIDVALIDITY
+ value.
+
+ C: A02 SELECT INBOX (QRESYNC (67890007 20050715194045000
+ 41,43:211,214:541))
+ S: * 464 EXISTS
+ S: * 3 RECENT
+ S: * OK [UIDVALIDITY 3857529045] UIDVALIDITY
+ S: * OK [UIDNEXT 550] Predicted next UID
+ S: * OK [HIGHESTMODSEQ 90060128194045007]
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+ S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+ \Deleted \Seen \*)] Permanent flags
+ S: A02 OK [READ-WRITE] Sorry, UIDVALIDITY mismatch
+
+ Modification Sequence and UID Parameters:
+
+ A server that doesn't support the persistent storage of mod-sequences
+ for the mailbox MUST send the OK untagged response including the
+ NOMODSEQ response code with every successful SELECT or EXAMINE
+ command, as described in [CONDSTORE]. Such a server doesn't need to
+ remember mod-sequences for expunged messages in the mailbox. It MUST
+ ignore the remaining parameters and behave as if no dynamic message
+ data changed.
+
+ If the provided UIDVALIDITY matches that of the selected mailbox, the
+ server then checks the last known modification sequence.
+
+
+
+Melnikov, et al. Standards Track [Page 5]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ The server sends the client any pending flag changes (using FETCH
+ responses that MUST contain UIDs) and expunges those that have
+ occurred in this mailbox since the provided modification sequence.
+
+ If the list of known UIDs was also provided, the server should only
+ report flag changes and expunges for the specified messages. If the
+ client did not provide the list of UIDs, the server acts as if the
+ client has specified "1:<maxuid>", where <maxuid> is the mailbox's
+ UIDNEXT value minus 1. If the mailbox is empty and never had any
+ messages in it, then lack of the list of UIDs is interpreted as an
+ empty set of UIDs.
+
+ Thus, the client can process just these pending events and need not
+ perform a full resynchronization. Without the message sequence
+ number matching information, the result of this step is semantically
+ equivalent to the client issuing:
+ tag1 UID FETCH "known-uids" (FLAGS) (CHANGEDSINCE
+ "mod-sequence-value" VANISHED)
+
+ Example:
+ C: A03 SELECT INBOX (QRESYNC (67890007
+ 90060115194045000 41,43:211,214:541))
+ S: * OK [CLOSED]
+ S: * 314 EXISTS
+ S: * 15 RECENT
+ S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+ S: * OK [UIDNEXT 567] Predicted next UID
+ S: * OK [HIGHESTMODSEQ 90060115205545359]
+ S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+ S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+ S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+ \Deleted \Seen \*)] Permanent flags
+ S: * VANISHED (EARLIER) 41,43:116,118,120:211,214:540
+ S: * 49 FETCH (UID 117 FLAGS (\Seen \Answered) MODSEQ
+ (90060115194045001))
+ S: * 50 FETCH (UID 119 FLAGS (\Draft $MDNSent) MODSEQ
+ (90060115194045308))
+ S: ...
+ S: * 100 FETCH (UID 541 FLAGS (\Seen $Forwarded) MODSEQ
+ (90060115194045001))
+ S: A03 OK [READ-WRITE] mailbox selected
+
+ Message sequence match data:
+
+ A client MAY provide a parenthesized list of a message sequence set
+ and the corresponding UID sets. Both MUST be provided in ascending
+ order. The server uses this data to restrict the range for which it
+ provides expunged message information.
+
+
+
+Melnikov, et al. Standards Track [Page 6]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Conceptually, the client provides a small sample of sequence numbers
+ for which it knows the corresponding UIDs. The server then compares
+ each sequence number and UID pair the client provides with the
+ current state of the mailbox. If a pair matches, then the client
+ knows of any expunges up to, and including, the message, and thus
+ will not include that range in the VANISHED response, even if the
+ "mod-sequence-value" provided by the client is too old for the server
+ to have data of when those messages were expunged.
+
+ Thus, if the Nth message number in the first set in the list is 4,
+ and the Nth UID in the second set in the list is 8, and the mailbox's
+ fourth message has UID 8, then no UIDs equal to or less than 8 are
+ present in the VANISHED response. If the (N+1)th message number is
+ 12, and the (N+1)th UID is 24, and the (N+1)th message in the mailbox
+ has UID 25, then the lowest UID included in the VANISHED response
+ would be 9.
+
+ In the following two examples, the server is unable to remember
+ expunges at all, and only UIDs with messages divisible by three are
+ present in the mailbox. In the first example, the client does not
+ use the fourth parameter; in the second, it provides it. This
+ example is somewhat extreme, but shows that judicious usage of the
+ sequence match data can save a substantial amount of bandwidth.
+
+ Example:
+ C: A04 SELECT INBOX (QRESYNC (67890007
+ 90060115194045000 1:29997))
+ S: * 10003 EXISTS
+ S: * 5 RECENT
+ S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+ S: * OK [UIDNEXT 30013] Predicted next UID
+ S: * OK [HIGHESTMODSEQ 90060115205545359]
+ S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+ S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+ S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+ \Deleted \Seen \*)] Permanent flags
+ S: * VANISHED (EARLIER) 1:2,4:5,7:8,10:11,13:14 [...]
+ 29998:29999,30001:30002,30004:30005,30007:30008
+ S: * 9889 FETCH (UID 29667 FLAGS (\Seen \Answered) MODSEQ
+ (90060115194045027))
+ S: * 9890 FETCH (UID 29670 FLAGS (\Draft $MDNSent) MODSEQ
+ (90060115194045028))
+ S: ...
+ S: * 9999 FETCH (UID 29997 FLAGS (\Seen $Forwarded) MODSEQ
+ (90060115194045031))
+ S: A04 OK [READ-WRITE] mailbox selected
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 7]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Example:
+ C: B04 SELECT INBOX (QRESYNC (67890007
+ 90060115194045000 1:29997 (5000,7500,9000,9990:9999 15000,
+ 22500,27000,29970,29973,29976,29979,29982,29985,29988,29991,
+ 29994,29997)))
+ S: * 10003 EXISTS
+ S: * 5 RECENT
+ S: * OK [UIDVALIDITY 67890007] UIDVALIDITY
+ S: * OK [UIDNEXT 30013] Predicted next UID
+ S: * OK [HIGHESTMODSEQ 90060115205545359]
+ S: * OK [UNSEEN 7] There are some unseen messages in the mailbox
+ S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
+ S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
+ \Deleted \Seen \*)] Permanent flags
+ S: * VANISHED (EARLIER) 29998:29999,30001:30002,30004:30005,30007:
+ 30008
+ S: * 9889 FETCH (UID 29667 FLAGS (\Seen \Answered) MODSEQ
+ (90060115194045027))
+ S: * 9890 FETCH (UID 29670 FLAGS (\Draft $MDNSent) MODSEQ
+ (90060115194045028))
+ S: ...
+ S: * 9999 FETCH (UID 29997 FLAGS (\Seen $Forwarded) MODSEQ
+ (90060115194045031))
+ S: B04 OK [READ-WRITE] mailbox selected
+
+3.2. VANISHED UID FETCH Modifier
+
+ [IMAPABNF] has extended the syntax of the FETCH and UID FETCH
+ commands to include an optional FETCH modifier. This document
+ defines a new UID FETCH modifier: VANISHED.
+
+ Note, that the VANISHED UID FETCH modifier is NOT allowed with a
+ FETCH command. The server MUST return a tagged BAD response if this
+ response is specified as a modifier to the FETCH command.
+
+ A server MUST respond with a tagged BAD response if the VANISHED UID
+ FETCH modifier is specified and the client hasn't issued "ENABLE
+ QRESYNC" in the current connection.
+
+ The VANISHED UID FETCH modifier MUST only be specified together with
+ the CHANGEDSINCE UID FETCH modifier.
+
+ The VANISHED UID FETCH modifier instructs the server to report those
+ messages from the UID set parameter that have been expunged and whose
+ associated mod-sequence is larger than the specified mod-sequence.
+ That is, the client requests to be informed of messages from the
+ specified set that were expunged since the specified mod-sequence.
+ Note that the mod-sequence(s) associated with these messages were
+
+
+
+Melnikov, et al. Standards Track [Page 8]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ updated when the messages were expunged (as described above). The
+ expunged messages are reported using the VANISHED response as
+ described in Section 3.6, which MUST contain the EARLIER tag. Any
+ VANISHED (EARLIER) responses MUST be returned before any FETCH
+ responses, as otherwise the client might get confused about how
+ message numbers map to UIDs.
+
+ Note: A server that receives a mod-sequence smaller than <minmodseq>,
+ where <minmodseq> is the value of the smallest expunged mod-sequence
+ it remembers minus one, MUST behave as if it was requested to report
+ all expunged messages from the provided UID set parameter.
+
+ Example 1: Without the VANISHED UID FETCH modifier, a CONDSTORE-aware
+ client [CONDSTORE] needs to issue separate commands to learn of flag
+ changes and expunged messages since the last synchronization:
+
+ C: s100 UID FETCH 300:500 (FLAGS) (CHANGEDSINCE 12345)
+ S: * 1 FETCH (UID 404 MODSEQ (65402) FLAGS (\Seen))
+ S: * 2 FETCH (UID 406 MODSEQ (75403) FLAGS (\Deleted))
+ S: * 4 FETCH (UID 408 MODSEQ (29738) FLAGS ($NoJunk
+ $AutoJunk $MDNSent))
+ S: s100 OK FETCH completed
+ C: s101 UID SEARCH 300:500
+ S: * SEARCH 404 406 407 408 410 412
+ S: s101 OK search completed
+
+ Where 300 and 500 are the lowest and highest UIDs from client's
+ cache. The second SEARCH response tells the client that the messages
+ with UIDs 407, 410, and 412 are still present, but their flags
+ haven't changed since the specified modification sequence.
+
+ Using the VANISHED UID FETCH modifier, it is sufficient to issue only
+ a single command:
+
+ C: s100 UID FETCH 300:500 (FLAGS) (CHANGEDSINCE 12345
+ VANISHED)
+ S: * VANISHED (EARLIER) 300:310,405,411
+ S: * 1 FETCH (UID 404 MODSEQ (65402) FLAGS (\Seen))
+ S: * 2 FETCH (UID 406 MODSEQ (75403) FLAGS (\Deleted))
+ S: * 4 FETCH (UID 408 MODSEQ (29738) FLAGS ($NoJunk
+ $AutoJunk $MDNSent))
+ S: s100 OK FETCH completed
+
+
+
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 9]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+3.3. EXPUNGE Command
+
+ Arguments: none
+
+ Responses: untagged responses: EXPUNGE or VANISHED
+
+ Result: OK - expunge completed
+ NO - expunge failure: can't expunge (e.g., permission denied)
+ BAD - command unknown or arguments invalid
+
+ This section updates the definition of the EXPUNGE command described
+ in Section 6.4.3 of [RFC3501].
+
+ The EXPUNGE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox. Before
+ returning an OK to the client, those messages that are removed are
+ reported using a VANISHED response or EXPUNGE responses.
+
+ If the server is capable of storing modification sequences for the
+ selected mailbox, it MUST increment the per-mailbox mod-sequence if
+ at least one message was permanently removed due to the execution of
+ the EXPUNGE command. For each permanently removed message, the
+ server MUST remember the incremented mod-sequence and corresponding
+ UID. If at least one message got expunged, the server MUST send the
+ updated per-mailbox modification sequence using the HIGHESTMODSEQ
+ response code (defined in [CONDSTORE]) in the tagged OK response.
+
+ Example: C: A202 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 5 EXPUNGE
+ S: * 8 EXPUNGE
+ S: A202 OK [HIGHESTMODSEQ 20010715194045319] expunged
+
+ Note: In this example, messages 3, 4, 7, and 11 had the \Deleted flag
+ set. The first "* 3 EXPUNGE" reports message # 3 as expunged. The
+ second "* 3 EXPUNGE" reports message # 4 as expunged (the message
+ number got decremented due to the previous EXPUNGE response). See
+ the description of the EXPUNGE response in [RFC3501] for further
+ explanation.
+
+ Note that if the server chooses to always send VANISHED responses
+ instead of EXPUNGE responses, the previous example might look like
+ this:
+
+ Example: C: B202 EXPUNGE
+ S: * VANISHED 405,407,410,425
+ S: B202 OK [HIGHESTMODSEQ 20010715194045319] expunged
+
+
+
+Melnikov, et al. Standards Track [Page 10]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Here messages with message numbers 3, 4, 7, and 11 have respective
+ UIDs 405, 407, 410, and 425.
+
+3.4. CLOSE Command
+
+ Arguments: none
+
+ Responses: no specific responses for this command
+
+ Result: OK - close completed, now in authenticated state
+ BAD - command unknown or arguments invalid
+
+ This section updates the definition of the CLOSE command described in
+ Section 6.4.2 of [RFC3501].
+
+ The CLOSE command permanently removes all messages that have the
+ \Deleted flag set from the currently selected mailbox, and returns to
+ the authenticated state from the selected state. No untagged EXPUNGE
+ (or VANISHED) responses are sent.
+
+ If the server is capable of storing modification sequences for the
+ selected mailbox, it MUST increment the per-mailbox mod-sequence if
+ at least one message was permanently removed due to the execution of
+ the CLOSE command. For each permanently removed message, the server
+ MUST remember the incremented mod-sequence and corresponding UID. If
+ at least one message got expunged, the server MUST send the updated
+ per-mailbox modification sequence using the HIGHESTMODSEQ response
+ code (defined in [CONDSTORE]) in the tagged OK response.
+
+ Example: C: A202 CLOSE
+ S: A202 OK [HIGHESTMODSEQ 20010715194045319] done
+
+3.5. UID EXPUNGE Command
+
+ Arguments: message set
+
+ Responses: untagged responses: EXPUNGE or VANISHED
+
+ Result: OK - expunge completed
+ NO - expunge failure: can't expunge (e.g., permission denied)
+ BAD - command unknown or arguments invalid
+
+ This section updates the definition of the UID EXPUNGE command
+ described in Section 2.1 of [UIDPLUS]. Servers that implement both
+ [UIDPLUS] and QRESYNC extensions must implement UID EXPUNGE as
+ described in this section.
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 11]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ The UID EXPUNGE command permanently removes from the currently
+ selected mailbox all messages that both have the \Deleted flag set
+ and have a UID that is included in the specified message set. If a
+ message either does not have the \Deleted flag set or has a UID that
+ is not included in the specified message set, it is not affected.
+
+ This command is particularly useful for disconnected mode clients.
+ By using UID EXPUNGE instead of EXPUNGE when resynchronizing with the
+ server, the client can avoid inadvertently removing any messages that
+ have been marked as \Deleted by other clients between the time that
+ the client was last connected and the time the client resynchronizes.
+
+ Before returning an OK to the client, those messages that are removed
+ are reported using a VANISHED response or EXPUNGE responses.
+
+ If the server is capable of storing modification sequences for the
+ selected mailbox, it MUST increment the per-mailbox mod-sequence if
+ at least one message was permanently removed due to the execution of
+ the UID EXPUNGE command. For each permanently removed message, the
+ server MUST remember the incremented mod-sequence and corresponding
+ UID. If at least one message got expunged, the server MUST send the
+ updated per-mailbox modification sequence using the HIGHESTMODSEQ
+ response code (defined in [CONDSTORE]) in the tagged OK response.
+
+ Example: C: . UID EXPUNGE 3000:3002
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: . OK [HIGHESTMODSEQ 20010715194045319] Ok
+
+ Note: In this example, at least messages with message numbers 3, 4,
+ and 5 (UIDs 3000 to 3002) had the \Deleted flag set. The first "* 3
+ EXPUNGE" reports message # 3 as expunged. The second "* 3 EXPUNGE"
+ reports message # 4 as expunged (the message number got decremented
+ due to the previous EXPUNGE response). See the description of the
+ EXPUNGE response in [RFC3501] for further explanation.
+
+3.6. VANISHED Response
+
+ Contents: an optional EARLIER tag
+
+ list of UIDs
+
+ The VANISHED response reports that the specified UIDs have been
+ permanently removed from the mailbox. This response is similar to
+ the EXPUNGE response [RFC3501]; however, it can return information
+ about multiple messages, and it returns UIDs instead of message
+
+
+
+
+Melnikov, et al. Standards Track [Page 12]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ numbers. The first benefit saves bandwidth, while the second is more
+ convenient for clients that only use UIDs to access the IMAP server.
+
+ The VANISHED response has the same restrictions on when it can be
+ sent as does the EXPUNGE response (see below).
+
+ The VANISHED response has two forms. The first form contains the
+ EARLIER tag, which signifies that the response was caused by a UID
+ FETCH (VANISHED) or a SELECT/EXAMINE (QRESYNC) command. This
+ response is sent if the UID set parameter to the UID FETCH (VANISHED)
+ command includes UIDs of messages that are no longer in the mailbox.
+ When the client sees a VANISHED EARLIER response, it MUST NOT
+ decrement message sequence numbers for each successive message in the
+ mailbox.
+
+ The second form doesn't contain the EARLIER tag and is described
+ below. Once a client has issued "ENABLE QRESYNC", the server SHOULD
+ use the VANISHED response without the EARLIER tag instead of the
+ EXPUNGE response. The server SHOULD continue using VANISHED in lieu
+ of EXPUNGE for the duration of the connection. In particular, this
+ affects the EXPUNGE [RFC3501] and UID EXPUNGE [UIDPLUS] commands, as
+ well as messages expunged in other connections. Such a VANISHED
+ response MUST NOT contain the EARLIER tag.
+
+ A VANISHED response sent because of an EXPUNGE or UID EXPUNGE command
+ or because messages were expunged in other connections (i.e., the
+ VANISHED response without the EARLIER tag) also decrements the number
+ of messages in the mailbox; it is not necessary for the server to
+ send an EXISTS response with the new value. It also decrements
+ message sequence numbers for each successive message in the mailbox
+ (see the example at the end of this section). Note that a VANISHED
+ response caused by EXPUNGE, UID EXPUNGE, or messages expunged in
+ other connections SHOULD only contain UIDs for messages expunged
+ since the last VANISHED/EXPUNGE response sent for the currently
+ opened mailbox or since the mailbox was opened. That is, servers
+ SHOULD NOT send UIDs for previously expunged messages, unless
+ explicitly requested to do so by the UID FETCH (VANISHED) command.
+
+ Note that client implementors must take care to properly decrement
+ the number of messages in the mailbox even if a server violates this
+ last SHOULD or repeats the same UID multiple times in the returned
+ UID set. In general, this means that a client using this extension
+ should either avoid using message numbers entirely, or have a
+ complete mapping of UIDs to message sequence numbers for the selected
+ mailbox.
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 13]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Because clients handle the two different forms of the VANISHED
+ response differently, servers MUST NOT report UIDs resulting from a
+ UID FETCH (VANISHED) or a SELECT/EXAMINE (QRESYNC) in the same
+ VANISHED response as UIDs of messages expunged now (i.e., messages
+ expunged in other connections). Instead, the server MUST send
+ separate VANISHED responses: one with the EARLIER tag and one
+ without.
+
+ A VANISHED response MUST NOT be sent when no command is in progress,
+ nor while responding to a FETCH, STORE, or SEARCH command. This rule
+ is necessary to prevent a loss of synchronization of message sequence
+ numbers between client and server. A command is not "in progress"
+ until the complete command has been received; in particular, a
+ command is not "in progress" during the negotiation of command
+ continuation.
+
+ Note: UID FETCH, UID STORE, and UID SEARCH are different commands
+ from FETCH, STORE, and SEARCH. A VANISHED response MAY be sent
+ during a UID command. However, the VANISHED response MUST NOT be
+ sent during a UID SEARCH command that contains message numbers in the
+ search criteria.
+
+ The update from the VANISHED response MUST be recorded by the client.
+
+ Example: Let's assume that there is the following mapping between
+ message numbers and UIDs in the currently selected mailbox (here "X"
+ marks messages with the \Deleted flag set, and "x" represents UIDs
+ which are not relevant for the example):
+
+ Message numbers: 1 2 3 4 5 6 7 8 9 10 11
+ UIDs: x 504 505 507 508 x 510 x x x 625
+ \Deleted messages: X X X X
+
+ In the presence of the extension defined in this document:
+
+ C: A202 EXPUNGE
+ S: * VANISHED 505,507,510,625
+ S: A202 OK EXPUNGE completed
+
+ Without the QRESYNC extension, the same example might look like:
+
+ C: A202 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 3 EXPUNGE
+ S: * 5 EXPUNGE
+ S: * 8 EXPUNGE
+ S: A202 OK EXPUNGE completed
+
+
+
+
+Melnikov, et al. Standards Track [Page 14]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ (Continuing previous example) If subsequently messages with UIDs 504
+ and 508 got marked as \Deleted:
+
+ C: A210 EXPUNGE
+ S: * VANISHED 504,508
+ S: A210 OK EXPUNGE completed
+
+ i.e., the last VANISHED response only contains UIDs of messages
+ expunged since the previous VANISHED response.
+
+3.7. CLOSED Response Code
+
+ The CLOSED response code has no parameters. A server implementing
+ the extension defined in this document MUST return the CLOSED
+ response code when the currently selected mailbox is closed
+ implicitly using the SELECT/EXAMINE command on another mailbox. The
+ CLOSED response code serves as a boundary between responses for the
+ previously opened mailbox (which was closed) and the newly selected
+ mailbox: all responses before the CLOSED response code relate to the
+ mailbox that was closed, and all subsequent responses relate to the
+ newly opened mailbox.
+
+ There is no need to return the CLOSED response code on completion of
+ the CLOSE or the UNSELECT [UNSELECT] command (or similar) whose
+ purpose is to close the currently selected mailbox without opening a
+ new one.
+
+4. Server Implementation Considerations
+
+ This section describes a minimalist implementation, a moderate
+ implementation, and an example of a full implementation.
+
+4.1. Server Implementations That Don't Store Extra State
+
+ Strictly speaking, a server implementation that doesn't remember mod-
+ sequences associated with expunged messages can be considered
+ compliant with this specification. Such implementations return all
+ expunged messages specified in the UID set of the UID FETCH
+ (VANISHED) command every time, without paying attention to the
+ specified CHANGEDSINCE mod-sequence. Such implementations are
+ discouraged, as they can end up returning VANISHED responses that are
+ bigger than the result of a UID SEARCH command for the same UID set.
+
+ Clients that use the message sequence match data can reduce the scope
+ of this VANISHED response substantially in the typical case where
+ expunges have not happened, or happen only toward the end of the
+ mailbox.
+
+
+
+
+Melnikov, et al. Standards Track [Page 15]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+4.2. Server Implementations Storing Minimal State
+
+ A server that stores the HIGHESTMODSEQ value at the time of the last
+ EXPUNGE can omit the VANISHED response when a client provides a
+ MODSEQ value that is equal to, or higher than, the current value of
+ this datum, that is, when there have been no EXPUNGEs.
+
+ A client providing message sequence match data can reduce the scope
+ as above. In the case where there have been no expunges, the server
+ can ignore this data.
+
+4.3. Additional State Required on the Server
+
+ When compared to the [CONDSTORE] extension, this extension requires
+ servers to store additional state associated with expunged messages.
+ Note that implementations are not required to store this state in
+ persistent storage; however, use of persistent storage is advisable.
+
+ One possible way to correctly implement the extension described in
+ this document is to store a queue of <UID set, mod-sequence> pairs.
+ <UID set> can be represented as a sequence of <min UID, max UID>
+ pairs.
+
+ When messages are expunged, one or more entries are added to the
+ queue tail.
+
+ When the server receives a request to return messages expunged since
+ a given mod-sequence, it will search the queue from the tail (i.e.,
+ going from the highest expunged mod-sequence to the lowest) until it
+ sees the first record with a mod-sequence less than or equal to the
+ given mod-sequence or it reaches the head of the queue.
+
+ Note that indefinitely storing information about expunged messages
+ can cause storage and related problems for an implementation. In the
+ worst case, this could result in almost 64Gb of storage for each IMAP
+ mailbox. For example, consider an implementation that stores <min
+ UID, max UID, mod-sequence> triples for each range of messages
+ expunged at the same time. Each triple requires 16 octets: 4 octets
+ for each of the two UIDs, and 8 octets for the mod-sequence. Assume
+ that there is a mailbox containing a single message with a UID of
+ 2**32-1 (the maximum possible UID value), where messages had
+ previously existed with UIDs starting at 1, and have been expunged
+ one at a time. For this mailbox alone, storage is required for the
+ triples <1, 1, modseq1>, <2, 2, modseq2>, ..., <2**32-2, 2**32-2,
+ modseq4294967294>.
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 16]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ Hence, implementations are encouraged to adopt strategies to protect
+ against such storage problems, such as limiting the size of the queue
+ used to store mod-sequences for expunged messages and "expiring"
+ older records when this limit is reached. When the selected
+ implementation-specific queue limit is reached, the oldest record(s)
+ are deleted from the queue (note that such records are located at the
+ queue head). For all such "expired" records, the server needs to
+ store a single mod-sequence, which is the highest mod-sequence for
+ all "expired" expunged messages.
+
+ Note that if the client provides the message sequence match data,
+ this can heavily reduce the data cost of sending a complete set of
+ missing UIDs; thus, reducing the problems for clients if a server is
+ unable to persist much of this queue. If the queue contains data
+ back to the requested mod-sequence, this data can be ignored.
+
+ Also, note that if the UIDVALIDITY of the mailbox changes or if the
+ mailbox is deleted, then any state associated with expunged messages
+ doesn't need to be preserved and SHOULD be deleted.
+
+5. Updated Synchronization Sequence
+
+ This section updates the description of optimized synchronization in
+ Section 6.1 of the [IMAP-DISC].
+
+ An advanced disconnected mail client should use the QRESYNC and
+ [CONDSTORE] extensions when they are supported by the server. The
+ client uses the value from the HIGHESTMODSEQ OK response code
+ received on mailbox opening to determine if it needs to
+ resynchronize. Once the synchronization is complete, it MUST cache
+ the received value (unless the mailbox UIDVALIDITY value has changed;
+ see below). The client MUST update its copy of the HIGHESTMODSEQ
+ value whenever the server sends a subsequent HIGHESTMODSEQ OK
+ response code.
+
+ After completing a full synchronization, the client MUST also take
+ note of any unsolicited MODSEQ FETCH data items received from the
+ server. Whenever the client receives a tagged response to a command,
+ it calculates the highest value among all MODSEQ FETCH data items
+ received since the last tagged response. If this value is bigger
+ than the client's copy of the HIGHESTMODSEQ value, then the client
+ MUST use this value as its new HIGHESTMODSEQ value.
+
+ Note: It is not safe to update the client's copy of the HIGHESTMODSEQ
+ value with a MODSEQ FETCH data item value as soon as it is received
+ because servers are not required to send MODSEQ FETCH data items in
+ increasing modseqence order. This can lead to the client missing
+ some changes in case of connectivity loss.
+
+
+
+Melnikov, et al. Standards Track [Page 17]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ When opening the mailbox for synchronization, the client uses the
+ QRESYNC parameter to the SELECT/EXAMINE command. The QRESYNC
+ parameter is followed by the UIDVALIDITY and mailbox HIGHESTMODSEQ
+ values, as known to the client. It can be optionally followed by the
+ set of UIDs, for example, if the client is only interested in partial
+ synchronization of the mailbox. The client may also transmit a list
+ containing its knowledge of message numbers.
+
+ If the SELECT/EXAMINE command is successful, the client compares
+ UIDVALIDITY as described in step d)1) in Section 3 of the
+ [IMAP-DISC]. If the cached UIDVALIDITY value matches the one
+ returned by the server and the server also returns the HIGHESTMODSEQ
+ response code, then the server reports expunged messages and returns
+ flag changes for all messages specified by the client in the UID set
+ parameter (or for all messages in the mailbox, if the client omitted
+ the UID set parameter). At this point, the client is synchronized,
+ except for maybe the new messages.
+
+ If upon a successful SELECT/EXAMINE (QRESYNC) command the client
+ receives a NOMODSEQ OK untagged response (instead of the
+ HIGHESTMODSEQ response code), it MUST remove the last known
+ HIGHESTMODSEQ value from its cache and follow the more general
+ instructions in Section 3 of the [IMAP-DISC].
+
+ At this point, the client is in sync with the server regarding old
+ messages. This client can now fetch information about new messages
+ (if requested by the user).
+
+ Step d) ("Server-to-client synchronization") in Section 4 of the
+ [IMAP-DISC] in the presence of the QRESYNC & CONDSTORE extensions is
+ amended as follows:
+
+ d) "Server-to-client synchronization" -- for each mailbox that
+ requires synchronization, do the following:
+
+ 1a) Check the mailbox UIDVALIDITY (see Section 4.1 of the [IMAP-DISC]
+ for more details) after issuing SELECT/EXAMINE (QRESYNC) command.
+
+ If the UIDVALIDITY value returned by the server differs, the
+ client MUST
+
+ * empty the local cache of that mailbox;
+
+ * "forget" the cached HIGHESTMODSEQ value for the mailbox;
+
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 18]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ * remove any pending "actions" which refer to UIDs in that
+ mailbox. Note, this doesn't affect actions performed on
+ client generated fake UIDs (see Section 5 of the
+ [IMAP-DISC]);
+
+ 2) Fetch the current "descriptors";
+
+ I) Discover new messages.
+
+ 3) Fetch the bodies of any "interesting" messages that the client
+ doesn't already have.
+
+ Example: The UIDVALIDITY value is the same, but the HIGHESTMODSEQ
+ value has changed on the server while the client was
+ offline:
+
+ C: A142 SELECT INBOX (QRESYNC (3857529045 20010715194032001 1:198))
+ S: * 172 EXISTS
+ S: * 1 RECENT
+ S: * OK [UNSEEN 12] Message 12 is first unseen
+ S: * OK [UIDVALIDITY 3857529045] UIDs valid
+ S: * OK [UIDNEXT 201] Predicted next UID
+ S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
+ S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
+ S: * OK [HIGHESTMODSEQ 20010715194045007]
+ S: * VANISHED (EARLIER) 1:5,7:8,10:15
+ S: * 2 FETCH (UID 6 MODSEQ (20010715205008000)
+ FLAGS (\Deleted))
+ S: * 5 FETCH (UID 9 MODSEQ (20010715195517000)
+ FLAGS ($NoJunk $AutoJunk $MDNSent))
+ ...
+ S: A142 OK [READ-WRITE] SELECT completed
+
+6. Formal Syntax
+
+ The following syntax specification uses the Augmented Backus-Naur
+ Form (ABNF) notation as specified in [ABNF].
+
+ Non-terminals referenced but not defined below are as defined by
+ [RFC3501], [CONDSTORE], or [IMAPABNF].
+
+ Except as noted otherwise, all alphabetic characters are case-
+ insensitive. The use of upper or lower case characters to define
+ token strings is for editorial clarity only. Implementations MUST
+ accept these strings in a case-insensitive fashion.
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 19]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+ capability =/ "QRESYNC"
+
+ select-param = "QRESYNC" SP "(" uidvalidity SP
+ mod-sequence-value [SP known-uids]
+ [SP seq-match-data] ")"
+ ;; conforms to the generic select-param
+ ;; syntax defined in [IMAPABNF]
+
+ seq-match-data = "(" known-sequence-set SP known-uid-set ")"
+
+ uidvalidity = nz-number
+
+ known-uids = sequence-set
+ ;; sequence of UIDs, "*" is not allowed
+
+ known-sequence-set = sequence-set
+ ;; set of message numbers corresponding to
+ ;; the UIDs in known-uid-set, in ascending order.
+ ;; * is not allowed.
+
+ known-uid-set = sequence-set
+ ;; set of UIDs corresponding to the messages in
+ ;; known-sequence-set, in ascending order.
+ ;; * is not allowed.
+
+ message-data =/ expunged-resp
+
+ expunged-resp = "VANISHED" [SP "(EARLIER)"] SP known-uids
+
+ rexpunges-fetch-mod = "VANISHED"
+ ;; VANISHED UID FETCH modifier conforms
+ ;; to the fetch-modifier syntax
+ ;; defined in [IMAPABNF]. It is only
+ ;; allowed in the UID FETCH command.
+
+ resp-text-code =/ "CLOSED"
+
+7. Security Considerations
+
+ As always, it is important to thoroughly test clients and servers
+ implementing this extension, as it changes how the server reports
+ expunged messages to the client.
+
+ Security considerations relevant to [CONDSTORE] are relevant to this
+ extension.
+
+ This document doesn't raise any new security concerns not already
+ raised by [CONDSTORE] or [RFC3501].
+
+
+
+Melnikov, et al. Standards Track [Page 20]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+8. IANA Considerations
+
+ IMAP4 capabilities are registered by publishing a standards track or
+ IESG approved experimental RFC. The registry is currently located
+ at:
+
+ http://www.iana.org/assignments/imap4-capabilities
+
+ This document defines the QRESYNC IMAP capability. IANA has added
+ this capability to the registry.
+
+9. Acknowledgments
+
+ Thanks to Steve Hole, Cyrus Daboo, and Michael Wener for encouraging
+ creation of this document.
+
+ Valuable comments, both in agreement and in dissent, were received
+ from Timo Sirainen, Michael Wener, Randall Gellens, Arnt Gulbrandsen,
+ Chris Newman, Peter Coates, Mark Crispin, Elwyn Davies, Dan Karp,
+ Eric Rescorla, and Mike Zraly.
+
+ This document takes substantial text from [RFC3501] by Mark Crispin.
+
+10. References
+
+10.1. Normative References
+
+ [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
+ Specifications: ABNF", STD 68, RFC 5234, January 2008.
+
+ [CONDSTORE] Melnikov, A. and S. Hole, "IMAP Extension for
+ Conditional STORE Operation or Quick Flag Changes
+ Resynchronization", RFC 4551, June 2006.
+
+ [ENABLE] Gulbrandsen, A., Ed. and A. Melnikov, Ed., "The IMAP
+ ENABLE Extension", RFC 5161, March 2008.
+
+ [IMAPABNF] Melnikov, A. and C. Daboo, "Collected Extensions to
+ IMAP4 ABNF", RFC 4466, April 2006.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
+ 4rev1", RFC 3501, March 2003.
+
+ [UIDPLUS] Crispin, M., "Internet Message Access Protocol (IMAP) -
+ UIDPLUS extension", RFC 4315, December 2005.
+
+
+
+Melnikov, et al. Standards Track [Page 21]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+10.2. Informative References
+
+ [IMAP-DISC] Melnikov, A., Ed., "Synchronization Operations For
+ Disconnected Imap4 Clients", RFC 4549, June 2006.
+
+ [UNSELECT] Melnikov, A., "Internet Message Access Protocol (IMAP)
+ UNSELECT command", RFC 3691, February 2004.
+
+Authors' Addresses
+
+ Alexey Melnikov
+ Isode Ltd
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: Alexey.Melnikov@isode.com
+
+
+ Dave Cridland
+ Isode Ltd
+ 5 Castle Business Village
+ 36 Station Road
+ Hampton, Middlesex TW12 2BX
+ UK
+
+ EMail: dave.cridland@isode.com
+
+
+ Corby Wilson
+ Nokia
+ 5 Wayside Rd.
+ Burlington, MA 01803
+ USA
+
+ EMail: corby@computer.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 22]
+
+RFC 5162 IMAP Quick Mailbox Resync March 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Melnikov, et al. Standards Track [Page 23]
+
diff --git a/imap/docs/rfc/rfc5234.txt b/imap/docs/rfc/rfc5234.txt
new file mode 100644
index 00000000..42bb44ca
--- /dev/null
+++ b/imap/docs/rfc/rfc5234.txt
@@ -0,0 +1,899 @@
+
+
+
+
+
+
+Network Working Group D. Crocker, Ed.
+Request for Comments: 5234 Brandenburg InternetWorking
+STD: 68 P. Overell
+Obsoletes: 4234 THUS plc.
+Category: Standards Track January 2008
+
+
+ Augmented BNF for Syntax Specifications: ABNF
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ Internet technical specifications often need to define a formal
+ syntax. Over the years, a modified version of Backus-Naur Form
+ (BNF), called Augmented BNF (ABNF), has been popular among many
+ Internet specifications. The current specification documents ABNF.
+ It balances compactness and simplicity with reasonable
+ representational power. The differences between standard BNF and
+ ABNF involve naming rules, repetition, alternatives, order-
+ independence, and value ranges. This specification also supplies
+ additional rule definitions and encoding for a core lexical analyzer
+ of the type common to several Internet specifications.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 1]
+
+RFC 5234 ABNF January 2008
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2. Rule Definition . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2.1. Rule Naming . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2.2. Rule Form . . . . . . . . . . . . . . . . . . . . . . . . 4
+ 2.3. Terminal Values . . . . . . . . . . . . . . . . . . . . . 4
+ 2.4. External Encodings . . . . . . . . . . . . . . . . . . . . 6
+ 3. Operators . . . . . . . . . . . . . . . . . . . . . . . . . . 6
+ 3.1. Concatenation: Rule1 Rule2 . . . . . . . . . . . . . . . 6
+ 3.2. Alternatives: Rule1 / Rule2 . . . . . . . . . . . . . . . 7
+ 3.3. Incremental Alternatives: Rule1 =/ Rule2 . . . . . . . . . 7
+ 3.4. Value Range Alternatives: %c##-## . . . . . . . . . . . . 8
+ 3.5. Sequence Group: (Rule1 Rule2) . . . . . . . . . . . . . . 8
+ 3.6. Variable Repetition: *Rule . . . . . . . . . . . . . . . 9
+ 3.7. Specific Repetition: nRule . . . . . . . . . . . . . . . 9
+ 3.8. Optional Sequence: [RULE] . . . . . . . . . . . . . . . . 9
+ 3.9. Comment: ; Comment . . . . . . . . . . . . . . . . . . . 9
+ 3.10. Operator Precedence . . . . . . . . . . . . . . . . . . . 10
+ 4. ABNF Definition of ABNF . . . . . . . . . . . . . . . . . . . 10
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
+ 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
+ 6.1. Normative References . . . . . . . . . . . . . . . . . . . 12
+ 6.2. Informative References . . . . . . . . . . . . . . . . . . 12
+ Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 13
+ Appendix B. Core ABNF of ABNF . . . . . . . . . . . . . . . . . . 13
+ B.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . . . 13
+ B.2. Common Encoding . . . . . . . . . . . . . . . . . . . . . 15
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 2]
+
+RFC 5234 ABNF January 2008
+
+
+1. Introduction
+
+ Internet technical specifications often need to define a formal
+ syntax and are free to employ whatever notation their authors deem
+ useful. Over the years, a modified version of Backus-Naur Form
+ (BNF), called Augmented BNF (ABNF), has been popular among many
+ Internet specifications. It balances compactness and simplicity with
+ reasonable representational power. In the early days of the Arpanet,
+ each specification contained its own definition of ABNF. This
+ included the email specifications, [RFC733] and then [RFC822], which
+ came to be the common citations for defining ABNF. The current
+ document separates those definitions to permit selective reference.
+ Predictably, it also provides some modifications and enhancements.
+
+ The differences between standard BNF and ABNF involve naming rules,
+ repetition, alternatives, order-independence, and value ranges.
+ Appendix B supplies rule definitions and encoding for a core lexical
+ analyzer of the type common to several Internet specifications. It
+ is provided as a convenience and is otherwise separate from the meta
+ language defined in the body of this document, and separate from its
+ formal status.
+
+2. Rule Definition
+
+2.1. Rule Naming
+
+ The name of a rule is simply the name itself, that is, a sequence of
+ characters, beginning with an alphabetic character, and followed by a
+ combination of alphabetics, digits, and hyphens (dashes).
+
+ NOTE:
+
+ Rule names are case insensitive.
+
+ The names <rulename>, <Rulename>, <RULENAME>, and <rUlENamE> all
+ refer to the same rule.
+
+ Unlike original BNF, angle brackets ("<", ">") are not required.
+ However, angle brackets may be used around a rule name whenever their
+ presence facilitates in discerning the use of a rule name. This is
+ typically restricted to rule name references in free-form prose, or
+ to distinguish partial rules that combine into a string not separated
+ by white space, such as shown in the discussion about repetition,
+ below.
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 3]
+
+RFC 5234 ABNF January 2008
+
+
+2.2. Rule Form
+
+ A rule is defined by the following sequence:
+
+ name = elements crlf
+
+ where <name> is the name of the rule, <elements> is one or more rule
+ names or terminal specifications, and <crlf> is the end-of-line
+ indicator (carriage return followed by line feed). The equal sign
+ separates the name from the definition of the rule. The elements
+ form a sequence of one or more rule names and/or value definitions,
+ combined according to the various operators defined in this document,
+ such as alternative and repetition.
+
+ For visual ease, rule definitions are left aligned. When a rule
+ requires multiple lines, the continuation lines are indented. The
+ left alignment and indentation are relative to the first lines of the
+ ABNF rules and need not match the left margin of the document.
+
+2.3. Terminal Values
+
+ Rules resolve into a string of terminal values, sometimes called
+ characters. In ABNF, a character is merely a non-negative integer.
+ In certain contexts, a specific mapping (encoding) of values into a
+ character set (such as ASCII) will be specified.
+
+ Terminals are specified by one or more numeric characters, with the
+ base interpretation of those characters indicated explicitly. The
+ following bases are currently defined:
+
+ b = binary
+
+ d = decimal
+
+ x = hexadecimal
+
+ Hence:
+
+ CR = %d13
+
+ CR = %x0D
+
+ respectively specify the decimal and hexadecimal representation of
+ [US-ASCII] for carriage return.
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 4]
+
+RFC 5234 ABNF January 2008
+
+
+ A concatenated string of such values is specified compactly, using a
+ period (".") to indicate a separation of characters within that
+ value. Hence:
+
+ CRLF = %d13.10
+
+ ABNF permits the specification of literal text strings directly,
+ enclosed in quotation marks. Hence:
+
+ command = "command string"
+
+ Literal text strings are interpreted as a concatenated set of
+ printable characters.
+
+ NOTE:
+
+ ABNF strings are case insensitive and the character set for these
+ strings is US-ASCII.
+
+ Hence:
+
+ rulename = "abc"
+
+ and:
+
+ rulename = "aBc"
+
+ will match "abc", "Abc", "aBc", "abC", "ABc", "aBC", "AbC", and
+ "ABC".
+
+ To specify a rule that is case sensitive, specify the characters
+ individually.
+
+ For example:
+
+ rulename = %d97 %d98 %d99
+
+ or
+
+ rulename = %d97.98.99
+
+ will match only the string that comprises only the lowercase
+ characters, abc.
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 5]
+
+RFC 5234 ABNF January 2008
+
+
+2.4. External Encodings
+
+ External representations of terminal value characters will vary
+ according to constraints in the storage or transmission environment.
+ Hence, the same ABNF-based grammar may have multiple external
+ encodings, such as one for a 7-bit US-ASCII environment, another for
+ a binary octet environment, and still a different one when 16-bit
+ Unicode is used. Encoding details are beyond the scope of ABNF,
+ although Appendix B provides definitions for a 7-bit US-ASCII
+ environment as has been common to much of the Internet.
+
+ By separating external encoding from the syntax, it is intended that
+ alternate encoding environments can be used for the same syntax.
+
+3. Operators
+
+3.1. Concatenation: Rule1 Rule2
+
+ A rule can define a simple, ordered string of values (i.e., a
+ concatenation of contiguous characters) by listing a sequence of rule
+ names. For example:
+
+ foo = %x61 ; a
+
+ bar = %x62 ; b
+
+ mumble = foo bar foo
+
+ So that the rule <mumble> matches the lowercase string "aba".
+
+ Linear white space: Concatenation is at the core of the ABNF parsing
+ model. A string of contiguous characters (values) is parsed
+ according to the rules defined in ABNF. For Internet specifications,
+ there is some history of permitting linear white space (space and
+ horizontal tab) to be freely and implicitly interspersed around major
+ constructs, such as delimiting special characters or atomic strings.
+
+ NOTE:
+
+ This specification for ABNF does not provide for implicit
+ specification of linear white space.
+
+ Any grammar that wishes to permit linear white space around
+ delimiters or string segments must specify it explicitly. It is
+ often useful to provide for such white space in "core" rules that are
+ then used variously among higher-level rules. The "core" rules might
+ be formed into a lexical analyzer or simply be part of the main
+ ruleset.
+
+
+
+Crocker & Overell Standards Track [Page 6]
+
+RFC 5234 ABNF January 2008
+
+
+3.2. Alternatives: Rule1 / Rule2
+
+ Elements separated by a forward slash ("/") are alternatives.
+ Therefore,
+
+ foo / bar
+
+ will accept <foo> or <bar>.
+
+ NOTE:
+
+ A quoted string containing alphabetic characters is a special form
+ for specifying alternative characters and is interpreted as a non-
+ terminal representing the set of combinatorial strings with the
+ contained characters, in the specified order but with any mixture
+ of upper- and lowercase.
+
+3.3. Incremental Alternatives: Rule1 =/ Rule2
+
+ It is sometimes convenient to specify a list of alternatives in
+ fragments. That is, an initial rule may match one or more
+ alternatives, with later rule definitions adding to the set of
+ alternatives. This is particularly useful for otherwise independent
+ specifications that derive from the same parent ruleset, such as
+ often occurs with parameter lists. ABNF permits this incremental
+ definition through the construct:
+
+ oldrule =/ additional-alternatives
+
+ So that the ruleset
+
+ ruleset = alt1 / alt2
+
+ ruleset =/ alt3
+
+ ruleset =/ alt4 / alt5
+
+ is the same as specifying
+
+ ruleset = alt1 / alt2 / alt3 / alt4 / alt5
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 7]
+
+RFC 5234 ABNF January 2008
+
+
+3.4. Value Range Alternatives: %c##-##
+
+ A range of alternative numeric values can be specified compactly,
+ using a dash ("-") to indicate the range of alternative values.
+ Hence:
+
+ DIGIT = %x30-39
+
+ is equivalent to:
+
+ DIGIT = "0" / "1" / "2" / "3" / "4" / "5" / "6" /
+
+ "7" / "8" / "9"
+
+ Concatenated numeric values and numeric value ranges cannot be
+ specified in the same string. A numeric value may use the dotted
+ notation for concatenation or it may use the dash notation to specify
+ one value range. Hence, to specify one printable character between
+ end-of-line sequences, the specification could be:
+
+ char-line = %x0D.0A %x20-7E %x0D.0A
+
+3.5. Sequence Group: (Rule1 Rule2)
+
+ Elements enclosed in parentheses are treated as a single element,
+ whose contents are strictly ordered. Thus,
+
+ elem (foo / bar) blat
+
+ matches (elem foo blat) or (elem bar blat), and
+
+ elem foo / bar blat
+
+ matches (elem foo) or (bar blat).
+
+ NOTE:
+
+ It is strongly advised that grouping notation be used, rather than
+ relying on the proper reading of "bare" alternations, when
+ alternatives consist of multiple rule names or literals.
+
+ Hence, it is recommended that the following form be used:
+
+ (elem foo) / (bar blat)
+
+ It will avoid misinterpretation by casual readers.
+
+
+
+
+
+Crocker & Overell Standards Track [Page 8]
+
+RFC 5234 ABNF January 2008
+
+
+ The sequence group notation is also used within free text to set off
+ an element sequence from the prose.
+
+3.6. Variable Repetition: *Rule
+
+ The operator "*" preceding an element indicates repetition. The full
+ form is:
+
+ <a>*<b>element
+
+ where <a> and <b> are optional decimal values, indicating at least
+ <a> and at most <b> occurrences of the element.
+
+ Default values are 0 and infinity so that *<element> allows any
+ number, including zero; 1*<element> requires at least one;
+ 3*3<element> allows exactly 3; and 1*2<element> allows one or two.
+
+3.7. Specific Repetition: nRule
+
+ A rule of the form:
+
+ <n>element
+
+ is equivalent to
+
+ <n>*<n>element
+
+ That is, exactly <n> occurrences of <element>. Thus, 2DIGIT is a
+ 2-digit number, and 3ALPHA is a string of three alphabetic
+ characters.
+
+3.8. Optional Sequence: [RULE]
+
+ Square brackets enclose an optional element sequence:
+
+ [foo bar]
+
+ is equivalent to
+
+ *1(foo bar).
+
+3.9. Comment: ; Comment
+
+ A semicolon starts a comment that continues to the end of line. This
+ is a simple way of including useful notes in parallel with the
+ specifications.
+
+
+
+
+
+Crocker & Overell Standards Track [Page 9]
+
+RFC 5234 ABNF January 2008
+
+
+3.10. Operator Precedence
+
+ The various mechanisms described above have the following precedence,
+ from highest (binding tightest) at the top, to lowest (loosest) at
+ the bottom:
+
+ Rule name, prose-val, Terminal value
+
+ Comment
+
+ Value range
+
+ Repetition
+
+ Grouping, Optional
+
+ Concatenation
+
+ Alternative
+
+ Use of the alternative operator, freely mixed with concatenations,
+ can be confusing.
+
+ Again, it is recommended that the grouping operator be used to
+ make explicit concatenation groups.
+
+4. ABNF Definition of ABNF
+
+ NOTES:
+
+ 1. This syntax requires a formatting of rules that is relatively
+ strict. Hence, the version of a ruleset included in a
+ specification might need preprocessing to ensure that it can
+ be interpreted by an ABNF parser.
+
+ 2. This syntax uses the rules provided in Appendix B.
+
+
+ rulelist = 1*( rule / (*c-wsp c-nl) )
+
+ rule = rulename defined-as elements c-nl
+ ; continues if next line starts
+ ; with white space
+
+ rulename = ALPHA *(ALPHA / DIGIT / "-")
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 10]
+
+RFC 5234 ABNF January 2008
+
+
+ defined-as = *c-wsp ("=" / "=/") *c-wsp
+ ; basic rules definition and
+ ; incremental alternatives
+
+ elements = alternation *c-wsp
+
+ c-wsp = WSP / (c-nl WSP)
+
+ c-nl = comment / CRLF
+ ; comment or newline
+
+ comment = ";" *(WSP / VCHAR) CRLF
+
+ alternation = concatenation
+ *(*c-wsp "/" *c-wsp concatenation)
+
+ concatenation = repetition *(1*c-wsp repetition)
+
+ repetition = [repeat] element
+
+ repeat = 1*DIGIT / (*DIGIT "*" *DIGIT)
+
+ element = rulename / group / option /
+ char-val / num-val / prose-val
+
+ group = "(" *c-wsp alternation *c-wsp ")"
+
+ option = "[" *c-wsp alternation *c-wsp "]"
+
+ char-val = DQUOTE *(%x20-21 / %x23-7E) DQUOTE
+ ; quoted string of SP and VCHAR
+ ; without DQUOTE
+
+ num-val = "%" (bin-val / dec-val / hex-val)
+
+ bin-val = "b" 1*BIT
+ [ 1*("." 1*BIT) / ("-" 1*BIT) ]
+ ; series of concatenated bit values
+ ; or single ONEOF range
+
+ dec-val = "d" 1*DIGIT
+ [ 1*("." 1*DIGIT) / ("-" 1*DIGIT) ]
+
+ hex-val = "x" 1*HEXDIG
+ [ 1*("." 1*HEXDIG) / ("-" 1*HEXDIG) ]
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 11]
+
+RFC 5234 ABNF January 2008
+
+
+ prose-val = "<" *(%x20-3D / %x3F-7E) ">"
+ ; bracketed string of SP and VCHAR
+ ; without angles
+ ; prose description, to be used as
+ ; last resort
+
+5. Security Considerations
+
+ Security is truly believed to be irrelevant to this document.
+
+6. References
+
+6.1. Normative References
+
+ [US-ASCII] American National Standards Institute, "Coded Character
+ Set -- 7-bit American Standard Code for Information
+ Interchange", ANSI X3.4, 1986.
+
+6.2. Informative References
+
+ [RFC733] Crocker, D., Vittal, J., Pogran, K., and D. Henderson,
+ "Standard for the format of ARPA network text messages",
+ RFC 733, November 1977.
+
+ [RFC822] Crocker, D., "Standard for the format of ARPA Internet
+ text messages", STD 11, RFC 822, August 1982.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 12]
+
+RFC 5234 ABNF January 2008
+
+
+Appendix A. Acknowledgements
+
+ The syntax for ABNF was originally specified in RFC 733. Ken L.
+ Harrenstien, of SRI International, was responsible for re-coding the
+ BNF into an Augmented BNF that makes the representation smaller and
+ easier to understand.
+
+ This recent project began as a simple effort to cull out the portion
+ of RFC 822 that has been repeatedly cited by non-email specification
+ writers, namely the description of Augmented BNF. Rather than simply
+ and blindly converting the existing text into a separate document,
+ the working group chose to give careful consideration to the
+ deficiencies, as well as benefits, of the existing specification and
+ related specifications made available over the last 15 years, and
+ therefore to pursue enhancement. This turned the project into
+ something rather more ambitious than was first intended.
+ Interestingly, the result is not massively different from that
+ original, although decisions, such as removing the list notation,
+ came as a surprise.
+
+ This "separated" version of the specification was part of the DRUMS
+ working group, with significant contributions from Jerome Abela,
+ Harald Alvestrand, Robert Elz, Roger Fajman, Aviva Garrett, Tom
+ Harsch, Dan Kohn, Bill McQuillan, Keith Moore, Chris Newman, Pete
+ Resnick, and Henning Schulzrinne.
+
+ Julian Reschke warrants a special thanks for converting the Draft
+ Standard version to XML source form.
+
+Appendix B. Core ABNF of ABNF
+
+ This appendix contains some basic rules that are in common use.
+ Basic rules are in uppercase. Note that these rules are only valid
+ for ABNF encoded in 7-bit ASCII or in characters sets that are a
+ superset of 7-bit ASCII.
+
+B.1. Core Rules
+
+ Certain basic rules are in uppercase, such as SP, HTAB, CRLF, DIGIT,
+ ALPHA, etc.
+
+ ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
+
+ BIT = "0" / "1"
+
+ CHAR = %x01-7F
+ ; any 7-bit US-ASCII character,
+ ; excluding NUL
+
+
+
+Crocker & Overell Standards Track [Page 13]
+
+RFC 5234 ABNF January 2008
+
+
+ CR = %x0D
+ ; carriage return
+
+ CRLF = CR LF
+ ; Internet standard newline
+
+ CTL = %x00-1F / %x7F
+ ; controls
+
+ DIGIT = %x30-39
+ ; 0-9
+
+ DQUOTE = %x22
+ ; " (Double Quote)
+
+ HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
+
+ HTAB = %x09
+ ; horizontal tab
+
+ LF = %x0A
+ ; linefeed
+
+ LWSP = *(WSP / CRLF WSP)
+ ; Use of this linear-white-space rule
+ ; permits lines containing only white
+ ; space that are no longer legal in
+ ; mail headers and have caused
+ ; interoperability problems in other
+ ; contexts.
+ ; Do not use when defining mail
+ ; headers and use with caution in
+ ; other contexts.
+
+ OCTET = %x00-FF
+ ; 8 bits of data
+
+ SP = %x20
+
+ VCHAR = %x21-7E
+ ; visible (printing) characters
+
+ WSP = SP / HTAB
+ ; white space
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 14]
+
+RFC 5234 ABNF January 2008
+
+
+B.2. Common Encoding
+
+ Externally, data are represented as "network virtual ASCII" (namely,
+ 7-bit US-ASCII in an 8-bit field), with the high (8th) bit set to
+ zero. A string of values is in "network byte order", in which the
+ higher-valued bytes are represented on the left-hand side and are
+ sent over the network first.
+
+Authors' Addresses
+
+ Dave Crocker (editor)
+ Brandenburg InternetWorking
+ 675 Spruce Dr.
+ Sunnyvale, CA 94086
+ US
+
+ Phone: +1.408.246.8253
+ EMail: dcrocker@bbiw.net
+
+
+ Paul Overell
+ THUS plc.
+ 1/2 Berkeley Square,
+ 99 Berkeley Street
+ Glasgow G3 7HR
+ UK
+
+ EMail: paul.overell@thus.net
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 15]
+
+RFC 5234 ABNF January 2008
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+ The IETF takes no position regarding the validity or scope of any
+ Intellectual Property Rights or other rights that might be claimed to
+ pertain to the implementation or use of the technology described in
+ this document or the extent to which any license under such rights
+ might or might not be available; nor does it represent that it has
+ made any independent effort to identify any such rights. Information
+ on the procedures with respect to rights in RFC documents can be
+ found in BCP 78 and BCP 79.
+
+ Copies of IPR disclosures made to the IETF Secretariat and any
+ assurances of licenses to be made available, or the result of an
+ attempt made to obtain a general license or permission for the use of
+ such proprietary rights by implementers or users of this
+ specification can be obtained from the IETF on-line IPR repository at
+ http://www.ietf.org/ipr.
+
+ The IETF invites any interested party to bring to its attention any
+ copyrights, patents or patent applications, or other proprietary
+ rights that may cover technology that may be required to implement
+ this standard. Please address the information to the IETF at
+ ietf-ipr@ietf.org.
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker & Overell Standards Track [Page 16]
+