selabel_file(5) SELinux API documentation selabel_file(5)
NAME
selabel_file - userspace SELinux labeling interface and configuration file format for the file contexts back‐
end
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 clar‐
ified 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.
ory' 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 SELA‐
BEL_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 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:
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)
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