Provided by: selinux-utils_3.5-2ubuntu2.1_amd64 bug

NAME

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

SYNOPSIS

       #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

       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

       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

       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

File Contexts Format

       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

       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

       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

       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)

Security Enhanced Linux                            01 Dec 2011                                   selabel_file(5)