From 094ca96844842928810f14844413109fc6cdd890 Mon Sep 17 00:00:00 2001 From: Eduardo Chappa Date: Sun, 3 Feb 2013 00:59:38 -0700 Subject: Initial Alpine Version --- imap/docs/rfc/rfc2221.txt | 283 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 283 insertions(+) create mode 100644 imap/docs/rfc/rfc2221.txt (limited to 'imap/docs/rfc/rfc2221.txt') 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 + + 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 + ; See [IMAP-URL] for definition of + ; 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] + -- cgit v1.2.3-70-g09d2