selabel_file(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | FILE FORMAT | File Contexts Format | Substitution File Format | NOTES | SEE ALSO | COLOPHON

selabel_file(5)         SELinux API documentation        selabel_file(5)

NAME         top

       selabel_file - userspace SELinux labeling interface and
       configuration file format for the file contexts backend

SYNOPSIS         top

       #include <selinux/label.h>

       int selabel_lookup(struct selabel_handle *hnd,
                          char **context,
                          const char *path, int mode);

       int selabel_lookup_raw(struct selabel_handle *hnd,
                          char **context,
                          const char *path, int mode);

DESCRIPTION         top

       The file contexts backend maps from pathname/mode combinations
       into security contexts. It is used to find the appropriate
       context for each file when relabeling a file system. The returned
       context must be freed using freecon(3).
       selabel_lookup(3) describes the function with its return and
       error codes, however the following errno is clarified further for
       the file contexts backend:

              ENOENT No context corresponding to the path and mode was
                     found - This will also be returned when the file
                     contexts series of files have a context of <<none>>
                     against the path (see the FILE FORMAT section).

       The path argument should be set to the full pathname of the file
       whose assigned context is being checked. The mode argument should
       be set to the mode bits of the file, as determined by lstat(2).
       mode may be zero, however full matching may not occur.

       Any messages generated by selabel_lookup(3) are sent to stderr by
       default, although this can be changed by selinux_set_callback(3).

       selabel_lookup_raw(3) behaves identically to selabel_lookup(3)
       but does not perform context translation.

       The FILES section details the configuration files used to
       determine a file context.

OPTIONS         top

       In addition to the global options described in selabel_open(3),
       this backend recognizes the following options:

              SELABEL_OPT_PATH
                     A non-null value for this option specifies a path
                     to a file that will be opened in lieu of the
                     standard file contexts file.  This value is also
                     used as the base name for determining the names of
                     local customization files.

              SELABEL_OPT_BASEONLY
                     A non-null value for this option indicates that any
                     local customizations to the file contexts mapping
                     should be ignored.

              SELABEL_OPT_SUBSET
                     A non-null value for this option is interpreted as
                     a path prefix, for example "/etc".  Only file
                     context specifications with starting with a first
                     component that prefix matches the given prefix are
                     loaded.  This may increase lookup performance,
                     however any attempt to look up a path not starting
                     with the given prefix may fail.  This optimization
                     is no longer required due to the use of
                     file_contexts.bin files and is deprecated.

FILES         top

       The file context files used to retrieve the default context
       depends on the SELABEL_OPT_PATH parameter passed to
       selabel_open(3). If NULL, then the SELABEL_OPT_PATH value will
       default to the active policy file contexts location (as returned
       by selinux_file_context_path(3)), otherwise the actual
       SELABEL_OPT_PATH value specified is used.

       If SELABEL_OPT_BASEONLY is set, then the following files will be
       processed:

              1.  The mandatory file contexts file that is either the
                  fully qualified file name from SELABEL_OPT_PATH.value
                  or if NULL, then the path returned by
                  selinux_file_context_path(3).

              2.  The optional local and distribution substitution files
                  that perform path aliasing on the 'in memory' version
                  of the file contexts file.
                  These files have the same name as the mandatory file
                  contexts file with the extensions .subs and .subs_dist
                  added.

       If the SELABEL_OPT_BASEONLY is not set, then the following files
       will be processed:

              1.  The mandatory file contexts file that is either the
                  fully qualified file name from SELABEL_OPT_PATH.value
                  or if NULL, then the path returned by
                  selinux_file_context_path(3).

              2.  The optional local customizations file that has the
                  same name as the mandatory file contexts file with the
                  extension .local added.
                  selinux_file_context_local_path(3) will return the
                  default path to this file.

              3.  The optional user home directory customizations file
                  that has the same name as the mandatory file contexts
                  file with the extension .homedirs added.
                  selinux_file_context_homedir_path(3) will return the
                  default path to this file.

              4.  The optional local and distribution substitution files
                  that perform any path aliasing on the 'in memory'
                  version of the file contexts file (and the .local
                  and/or .homedirs if present). These files have the
                  same name as the mandatory file contexts file with the
                  extensions .subs and .subs_dist added.
                  selinux_file_context_subs_path(3) and
                  selinux_file_context_subs_dist_path(3) will return the
                  default paths to these files.

       The default file context series of files are:
             /etc/selinux/{SELINUXTYPE}/contexts/files/file_contexts
             /etc/selinux/{SELINUXTYPE}/contexts/files/file_contexts.local
             /etc/selinux/{SELINUXTYPE}/contexts/files/file_contexts.homedirs
             /etc/selinux/{SELINUXTYPE}/contexts/files/file_contexts.subs
             /etc/selinux/{SELINUXTYPE}/contexts/files/file_contexts.subs_dist

       Where {SELINUXTYPE} is the entry from the selinux configuration
       file config (see selinux_config(5)).

       Only the file_contexts file is mandatory, the remainder are
       optional.

       The entries within the file contexts series of files are shown in
       the FILE FORMAT section.

FILE FORMAT         top


File Contexts Format         top

       Each line within the file_contexts and the two customization
       files (.local and .homedirs) is as follows:

              pathname [file_type] context

       Where:
              pathname
                     An entry that defines the path to be labeled.  May
                     contain either a fully qualified path, or a Perl
                     compatible regular expression (PCRE), describing
                     fully qualified path(s).  The only PCRE flag in use
                     is PCRE2_DOTALL, which causes a wildcard '.' to
                     match anything, including a new line.  Strings
                     representing paths are processed as bytes (as
                     opposed to Unicode), meaning that non-ASCII
                     characters are not matched by a single wildcard.
              file_type
                     An optional file type consisting of:
                            -b - Block Device      -c - Character Device
                            -d - Directory         -p - Named Pipe
                            -l - Symbolic Link     -s - Socket
                            -- - Ordinary file
              context
                     This entry can be either:

                            a.  The security context that will be
                                assigned to the file (i.e. returned as
                                context).

                            b.  A value of <<none>> can be used to
                                indicate that the matching files should
                                not be re-labeled and causes
                                selabel_lookup(3) to return -1 with
                                errno set to ENOENT.

       Example:
              # ./contexts/files/file_contexts
              # pathname file_type  context
              /.*                   system_u:object_r:default_t:s0
              /[^/]+        --      system_u:object_r:etc_runtime_t:s0
              /tmp/.*               <<none>>

Substitution File Format         top

       Each line within the substitution files (.subs and .subs_dist)
       has the form:
              subs_pathname pathname

       Where:
              pathname
                     A path that matches an entry in one or more of the
                     file contexts policy configuration file.
              subs_pathname
                     The path that will be aliased (considered
                     equivalent) with pathname by the look up process.

       Example:
              # ./contexts/files/file_contexts.subs
              # pathname  subs_pathname
              /myweb      /var/www
              /myspool    /var/spool/mail

              Using the above example, when selabel_lookup(3) is passed
              a path of /myweb/index.html the function will substitute
              the /myweb component with /var/www, therefore the path
              used is:

                     /var/www/index.html

NOTES         top

       1.  If contexts are to be validated, then the global option
           SELABEL_OPT_VALIDATE must be set before calling
           selabel_open(3). If this is not set, then it is possible for
           an invalid context to be returned.

       2.  If the size of file contexts series of files contain many
           entries, then selabel_open(3) may have a delay as it reads in
           the files, and if requested validates the entries.

       3.  Depending on the version of SELinux it is possible that a
           file_contexts.template file may also be present, however this
           is now deprecated.
           The template file has the same format as the file_contexts
           file and may also contain the keywords HOME_ROOT, HOME_DIR,
           ROLE and USER. This functionality has now been moved to the
           policy store and managed by semodule(8) and genhomedircon(8).

SEE ALSO         top

       selinux(8), selabel_open(3), selabel_lookup(3), selabel_stats(3),
       selabel_close(3), selinux_set_callback(3),
       selinux_file_context_path(3), freecon(3), selinux_config(5),
       lstat(2), selinux_file_context_subs_path(3),
       selinux_file_context_subs_dist_path(3),
       selinux_file_context_homedir_path(3),
       selinux_file_context_local_path(3), semodule(8), genhomedircon(8)

COLOPHON         top

       This page is part of the selinux (Security-Enhanced Linux user-
       space libraries and tools) project.  Information about the
       project can be found at 
       ⟨https://github.com/SELinuxProject/selinux/wiki⟩.  If you have a
       bug report for this manual page, see
       ⟨https://github.com/SELinuxProject/selinux/wiki/Contributing⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/SELinuxProject/selinux⟩ on 2021-08-27.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-08-23.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

Security Enhanced Linux        01 Dec 2011               selabel_file(5)

Pages that refer to this page: selabel_get_digests_all_partial_matches(3)selabel_lookup_best_match(3)selabel_open(3)selabel_partial_match(3)selinux_restorecon_default_handle(3)restorecon_xattr(8)