пользовательский интерфейс маркировки SELinux и формат файла конфигурации для серверной части контекстов файлов (userspace SELinux labeling interface and configuration file format for the file contexts backend)
Имя (Name)
selabel_file - userspace SELinux labeling interface and
configuration file format for the file contexts backend
Синопсис (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);
Описание (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.
Параметры (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.
Файлы (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.
Формат файла (File 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>>
Формат файла подстановки (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
Примечание (Note)
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).
Смотри также (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)
