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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)
selabel_file - userspace SELinux labeling interface and configuration
file format for the file contexts backend
#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);
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.
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.
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.
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>>
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
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).
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)
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 2017-07-05. If you
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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_lookup_best_match(3), selabel_open(3), selabel_partial_match(3), selinux_restorecon_default_handle(3), restorecon_xattr(8)