selinux: adjust utils to run restorecon with -Z

cp, mv, install, mkdir, mkfifo, mknod are adjusted so that:
 -Z no longer accepts an argument.
 -Z or --context without an argument do not warn without SELinux.
 --context with an argument will warn without SELinux.

* src/local.mk: Reference the new selinux module where required.
* src/system.h: Make the argument to --context optional.
* src/mkdir.c: Likewise.  Also handle the SMACK case for --context.
Note we currently silently ignore -Z with SMACK.
* src/mkfifo.c: Likewise.
* src/mknod.c: Likewise.
* src/install.c: Likewise.  Note install(1) by default already
set the context for target files to their system default,
albeit with an older method.  Use the -Z option to select between
the old and new context restoration behavior, and document
the differences and details for how context restoration
is done in new and old methods, with a view disabling the
old method entirely in future.
* src/cp.c: Make the argument to --context optional.
Note -Z implies --no-preserve=context.  I.E. -Z overrides
that aspect of -a no matter what order specified.
(struct cp_options): Document the context handling options.
(main): Check/adjust option combinations after all
options are processed, to both simplify processing
and to make handling independent of order of options
on the command line.  Also improve the diagnostics
from a failed call to setfscreatecon().
(set_process_security_ctx): A new function,
refactored to set the default context from the source file,
or with the type adjusted as per the system default for
the destination path.
(set_file_security_ctx): A new function refactored to
set the security context of an existing file, either based on
the process context or the default system context for a path.
(copy_internal): Use the refactored functions to simplify
error handling and consistently fail or warn as needed.
(copy_reg): Likewise.
(copy_internal): With --preserve=context, also copy
context from non regular files.  Note for directories this may
impact the copying of subsequent files to that directory?
(copy_attr): If we're handling SELinux explicitly,
then exclude to avoid the redudant copy with --preserve=context,
and the problematic copy with -Z.  Note SELinux attribute exclusion
also now honors cp -a --no-preserve=context.  Note there was a
very small window over 10 years ago, where attr_copy_file was
available, while attr_copy_check_permissions was not, so we
don't bother adding an explicit m4 check for the latter function.
* src/mv.c: Support --context, but don't allow specifying an argument.
* src/chcon.c: Adjust a comment to be specific to SELinux.
* src/runcon.c: Likewise.
* src/copy.c: Honor the context settings to "restorecon" as appropriate.
* src/copy.h: Add a new setting to select "restorecon" functionality.
* tests/mkdir/selinux.sh: s/-Z/--context=/
* tests/cp/cp-a-selinux.sh: Augment this test with cases
testing basic -Z functionality, and also test the various
invalid option combinations and option precedence.
* tests/mkdir/restorecon.sh: Add a new test for the
more involved mkdir -Z handling, since the directory changing
and non existent directories need to be specially handled.
Also check the similar but simpler handling of -Z by mk{nod,fifo}.
* tests/local.mk: Reference the new test.
* doc/coreutils.texi (cp invocation): Update as per interface changes.
(mv invocation): Likewise.
(install invocation): Likewise.
(mkfifo invocation): Likewise.
(mknod invocation): Likewise.
(mkdir invocation): Likewise.
* NEWS: Mention the new feature and change in behavior.

1 files changed, 34 insertions, 19 deletions

diff --git a/src/install.c b/src/install.c
index a5ed7a821..707665526 100644
--- a/src/install.c
+++ b/src/install.c
@@ -279,7 +279,6 @@ cp_option_init (struct cp_options *x)
   x->reduce_diagnostics=false;
   x->data_copy_required = true;
   x->require_preserve = false;
-  x->require_preserve_context = false;
   x->require_preserve_xattr = false;
   x->recursive = false;
   x->sparse_mode = SPARSE_AUTO;
@@ -295,7 +294,9 @@ cp_option_init (struct cp_options *x)
 
   x->open_dangling_dest_symlink = false;
   x->update = false;
-  x->preserve_security_context = false;
+  x->require_preserve_context = false;  /* Not used by install currently.  */
+  x->preserve_security_context = false; /* Whether to copy context from src.  */
+  x->set_security_context = false;    /* Whether to set sys default context.  */
   x->preserve_xattr = false;
   x->verbose = false;
   x->dest_info = NULL;
@@ -305,7 +306,8 @@ cp_option_init (struct cp_options *x)
 #ifdef ENABLE_MATCHPATHCON
 /* Modify file context to match the specified policy.
    If an error occurs the file will remain with the default directory
-   context.  */
+   context.  Note this sets the context to that returned by matchpathcon,
+   and thus discards MLS levels and user identity of the FILE.  */
 static void
 setdefaultfilecon (char const *file)
 {
@@ -359,7 +361,8 @@ setdefaultfilecon (char const *file)
   first_call = false;
 
   /* If there's an error determining the context, or it has none,
-     return to allow default context */
+     return to allow default context.  Note the "<<none>>" check
+     is only needed for libselinux < 1.20 (2005-01-04).  */
   if ((matchpathcon (file, st.st_mode, &scontext) != 0)
       || STREQ (scontext, "<<none>>"))
     {
@@ -644,8 +647,8 @@ In the 4th form, create all components of the given DIRECTORY(ies).\n\
 "), stdout);
       fputs (_("\
       --preserve-context  preserve SELinux security context\n\
-  -Z, --context=CONTEXT  set SELinux security context of files and directories\
-\n\
+  -Z, --context[=CTX]     set SELinux security context of destination file to\n\
+                            default type, or to CTX if specified\n\
 "), stdout);
 
       fputs (HELP_OPTION_DESCRIPTION, stdout);
@@ -791,7 +794,7 @@ main (int argc, char **argv)
      we'll actually use backup_suffix_string.  */
   backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");
 
-  while ((optc = getopt_long (argc, argv, "bcCsDdg:m:o:pt:TvS:Z:", long_options,
+  while ((optc = getopt_long (argc, argv, "bcCsDdg:m:o:pt:TvS:Z", long_options,
                               NULL)) != -1)
     {
       switch (optc)
@@ -863,7 +866,7 @@ main (int argc, char **argv)
           break;
 
         case PRESERVE_CONTEXT_OPTION:
-          if ( ! selinux_enabled)
+          if (! selinux_enabled)
             {
               error (0, 0, _("WARNING: ignoring --preserve-context; "
                              "this kernel is not SELinux-enabled"));
@@ -873,14 +876,27 @@ main (int argc, char **argv)
           use_default_selinux_context = false;
           break;
         case 'Z':
-          if ( ! selinux_enabled)
+          if (selinux_enabled)
             {
-              error (0, 0, _("WARNING: ignoring --context (-Z); "
-                             "this kernel is not SELinux-enabled"));
-              break;
+              /* Disable use of the install(1) specific setdefaultfilecon().
+                 Note setdefaultfilecon() is different from the newer and more
+                 generic restorecon() in that the former sets the context of
+                 the dest files to that returned by matchpathcon directly,
+                 thus discarding MLS level and user identity of the file.
+                 TODO: consider removing setdefaultfilecon() in future.  */
+              use_default_selinux_context = false;
+
+              if (optarg)
+                scontext = optarg;
+              else
+                x.set_security_context = true;
+            }
+          else if (optarg)
+            {
+              error (0, 0,
+                     _("warning: ignoring --context; "
+                       "it requires an SELinux-enabled kernel"));
             }
-          scontext = optarg;
-          use_default_selinux_context = false;
           break;
         case_GETOPT_HELP_CHAR;
         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
@@ -897,11 +913,6 @@ main (int argc, char **argv)
     error (EXIT_FAILURE, 0,
            _("target directory not allowed when installing a directory"));
 
-  if (x.preserve_security_context && scontext != NULL)
-    error (EXIT_FAILURE, 0,
-           _("cannot force target context to %s and preserve it"),
-           quote (scontext));
-
   if (backup_suffix_string)
     simple_backup_suffix = xstrdup (backup_suffix_string);
 
@@ -910,6 +921,10 @@ main (int argc, char **argv)
                                    version_control_string)
                    : no_backups);
 
+  if (x.preserve_security_context && (x.set_security_context || scontext))
+    error (EXIT_FAILURE, 0,
+           _("cannot set target context and preserve it"));
+
   if (scontext && setfscreatecon (scontext) < 0)
     error (EXIT_FAILURE, errno,
            _("failed to set default file creation context to %s"),