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selabel_file(5)            SELinux API documentation           selabel_file(5)

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 specifica-
                     tions 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 opti-
                     mization  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 con-
       texts 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 pro-
       cessed:
              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  con-
                  texts 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_con-
                  text_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_con-
              texts.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 pathname that may be in the
                     form of a regular expression.
              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 SELA-
           BEL_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_con-
           texts.template file may also be present, however this is now depre-
           cated.
           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  man-
           aged 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)