sefcontext: add support for path substitutions (#5830)

* sefcontext: add path substitution support (#1193)

First commit for feedback, missing docs and tests.

* sefcontext: add documentation

* Add changelog fragment

* Documentation formatting

* Delete extra newline

* pep8 fixes

Fix indentation

* Add version_added to arg docs

* Add examples

* Don't delete non-matching path substitutions

* Add integration tests

* Delete only substitutions if such arg passed

Don't delete existing regular file context mappings if deletion of
a path substitution was requested with the presence of the
`equal` arg - delete only path substitutions in such case.

Path substitutions and regular mappings may overlap.

* Can only add args in minor releases

:(

* Cleanup before tests

* Fix deletion using substitution

Was comparing wrong var.

* Fix test checking wrong var

* Improve args documentation and examples

List the default values for selevel, seuser.
Add example for deleting path substitutions only.

* Add attributes documentation block

Not sure if should add become/delegate/async,
shouldn't those work just like that without any
specific code added for them?

* and fix indentation on attribute block

* Consistent indentation for attributes

Confusing, most plugins indent with 4 spaces.
But some use 2 like the rest of the code, so use 2.

* Add missing ref for attribute block

* Use correct c.g version in doc block

Co-authored-by: Felix Fontein <felix@fontein.de>

* Add full stop to changelog fragment

Co-authored-by: Felix Fontein <felix@fontein.de>

* Streamline documentation

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* Support limiting deletion to setype

Deleting file context mappings may be limited by
passing setype or equal, if neither arg is passed
then delete either setype/equal mappings that match.

* Change arg name, diff mode output fix

Change arg name from equal to substitute.
Print target = subsitute in diff mode same way as
semanage does.

Also put back platform attribute, try to improve
clumsy language in the substitute arg docs.

* Delete even if arg setype not match existing

Test 5 indicates that deletion is supposed to not check that
the arg setype passed when deleting matches the setype
of the mapping to delete.
Delete any mapping that matches target, regardless of
setype arg value.

* Update arg name in tests

* Too eager replacing

Accidentally replaced seobject function names so fix them back

* 4564: Fix invalid setype in doc example

Change from httpd_git_rw_content_t which
does not exist to httpd_sys_rw_content_t

Fixes #4564

* Fix documentation attributes

Additional fragment

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update version_added in docs

Bumping minor to 6.4.0 since it didn't make 6.3.0.

* Add more description to the new arg docs

Try to improve discoverability of the new feature and make it easier to understand without deep SELinux understanding.

* Update platform to Linux in documentation

* Add equal as alias for the new argument

Improve discoverability of the new feature by adding an alias to the new module argument. The argument name "equal" will be easy to find for users who are not familiar with SELinux and who just try to match to the CLI tool `semanage`.

* And add alias argument properly

Previous commit missed actually adding the alias (added to docs only).

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>
(cherry picked from commit c8a2ac3)

changelogs/fragments/5830-sefcontext-path-subs.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - sefcontext - add support for path substitutions (https://github.com/ansible-collections/community.general/issues/1193).

plugins/modules/sefcontext.py

@@ -17,11 +17,14 @@
   - Similar to the C(semanage fcontext) command.
 extends_documentation_fragment:
   - community.general.attributes
+  - community.general.attributes.platform
 attributes:
   check_mode:
     support: full
   diff_mode:
     support: full
+  platform:
+    platforms: linux
 options:
   target:
     description:
@@ -46,21 +49,30 @@
     default: a
   setype:
     description:
-    - SELinux type for the specified target.
+    - SELinux type for the specified I(target).
     type: str
-    required: true
+  substitute:
+    description:
+    - Path to use to substitute file context(s) for the specified I(target). The context labeling for the I(target) subtree is made equivalent to this path.
+    - This is also referred to as SELinux file context equivalence and it implements the C(equal) functionality of the SELinux management tools.
+    version_added: 6.4.0
+    type: str
+    aliases: [ equal ]
   seuser:
     description:
-    - SELinux user for the specified target.
+    - SELinux user for the specified I(target).
+    - Defaults to C(system_u) for new file contexts and to existing value when modifying file contexts.
     type: str
   selevel:
     description:
-    - SELinux range for the specified target.
+    - SELinux range for the specified I(target).
+    - Defaults to C(s0) for new file contexts and to existing value when modifying file contexts.
     type: str
     aliases: [ serange ]
   state:
     description:
     - Whether the SELinux file context must be C(absent) or C(present).
+    - Specifying C(absent) without either I(setype) or I(substitute) deletes both SELinux type or path substitution mappings that match I(target).
     type: str
     choices: [ absent, present ]
     default: present
@@ -77,6 +89,8 @@
     default: false
 notes:
 - The changes are persistent across reboots.
+- I(setype) and I(substitute) are mutually exclusive.
+- If I(state=present) then one of I(setype) or I(substitute) is mandatory.
 - The M(community.general.sefcontext) module does not modify existing files to the new
   SELinux context(s), so it is advisable to first create the SELinux
   file contexts before creating files, or run C(restorecon) manually
@@ -96,9 +110,26 @@
 - name: Allow apache to modify files in /srv/git_repos
   community.general.sefcontext:
     target: '/srv/git_repos(/.*)?'
-    setype: httpd_git_rw_content_t
+    setype: httpd_sys_rw_content_t
+    state: present
+
+- name: Substitute file contexts for path /srv/containers with /var/lib/containers
+  community.general.sefcontext:
+    target: /srv/containers
+    substitute: /var/lib/containers
     state: present
 
+- name: Delete file context path substitution for /srv/containers
+  community.general.sefcontext:
+    target: /srv/containers
+    substitute: /var/lib/containers
+    state: absent
+
+- name: Delete any file context mappings for path /srv/git
+  community.general.sefcontext:
+    target: /srv/git
+    state: absent
+
 - name: Apply new SELinux file context to filesystem
   ansible.builtin.command: restorecon -irv /srv/git_repos
 '''
@@ -170,7 +201,13 @@ def semanage_fcontext_exists(sefcontext, target, ftype):
         return None
 
 
-def semanage_fcontext_modify(module, result, target, ftype, setype, do_reload, serange, seuser, sestore=''):
+def semanage_fcontext_substitute_exists(sefcontext, target):
+    ''' Get the SELinux file context path substitution definition from policy. Return None if it does not exist. '''
+
+    return sefcontext.equiv_dist.get(target, sefcontext.equiv.get(target))
+
+
+def semanage_fcontext_modify(module, result, target, ftype, setype, substitute, do_reload, serange, seuser, sestore=''):
     ''' Add or modify SELinux file context mapping definition to the policy. '''
 
     changed = False
@@ -179,39 +216,63 @@ def semanage_fcontext_modify(module, result, target, ftype, setype, do_reload, s
     try:
         sefcontext = seobject.fcontextRecords(sestore)
         sefcontext.set_reload(do_reload)
-        exists = semanage_fcontext_exists(sefcontext, target, ftype)
-        if exists:
-            # Modify existing entry
-            orig_seuser, orig_serole, orig_setype, orig_serange = exists
+        if substitute is None:
+            exists = semanage_fcontext_exists(sefcontext, target, ftype)
+            if exists:
+                # Modify existing entry
+                orig_seuser, orig_serole, orig_setype, orig_serange = exists
+
+                if seuser is None:
+                    seuser = orig_seuser
+                if serange is None:
+                    serange = orig_serange
+
+                if setype != orig_setype or seuser != orig_seuser or serange != orig_serange:
+                    if not module.check_mode:
+                        sefcontext.modify(target, setype, ftype, serange, seuser)
+                    changed = True
+
+                    if module._diff:
+                        prepared_diff += '# Change to semanage file context mappings\n'
+                        prepared_diff += '-%s      %s      %s:%s:%s:%s\n' % (target, ftype, orig_seuser, orig_serole, orig_setype, orig_serange)
+                        prepared_diff += '+%s      %s      %s:%s:%s:%s\n' % (target, ftype, seuser, orig_serole, setype, serange)
+            else:
+                # Add missing entry
+                if seuser is None:
+                    seuser = 'system_u'
+                if serange is None:
+                    serange = 's0'
 
-            if seuser is None:
-                seuser = orig_seuser
-            if serange is None:
-                serange = orig_serange
-
-            if setype != orig_setype or seuser != orig_seuser or serange != orig_serange:
                 if not module.check_mode:
-                    sefcontext.modify(target, setype, ftype, serange, seuser)
+                    sefcontext.add(target, setype, ftype, serange, seuser)
                 changed = True
 
                 if module._diff:
-                    prepared_diff += '# Change to semanage file context mappings\n'
-                    prepared_diff += '-%s      %s      %s:%s:%s:%s\n' % (target, ftype, orig_seuser, orig_serole, orig_setype, orig_serange)
-                    prepared_diff += '+%s      %s      %s:%s:%s:%s\n' % (target, ftype, seuser, orig_serole, setype, serange)
+                    prepared_diff += '# Addition to semanage file context mappings\n'
+                    prepared_diff += '+%s      %s      %s:%s:%s:%s\n' % (target, ftype, seuser, 'object_r', setype, serange)
         else:
-            # Add missing entry
-            if seuser is None:
-                seuser = 'system_u'
-            if serange is None:
-                serange = 's0'
-
-            if not module.check_mode:
-                sefcontext.add(target, setype, ftype, serange, seuser)
-            changed = True
-
-            if module._diff:
-                prepared_diff += '# Addition to semanage file context mappings\n'
-                prepared_diff += '+%s      %s      %s:%s:%s:%s\n' % (target, ftype, seuser, 'object_r', setype, serange)
+            exists = semanage_fcontext_substitute_exists(sefcontext, target)
+            if exists:
+                # Modify existing path substitution entry
+                orig_substitute = exists
+
+                if substitute != orig_substitute:
+                    if not module.check_mode:
+                        sefcontext.modify_equal(target, substitute)
+                    changed = True
+
+                    if module._diff:
+                        prepared_diff += '# Change to semanage file context path substitutions\n'
+                        prepared_diff += '-%s = %s\n' % (target, orig_substitute)
+                        prepared_diff += '+%s = %s\n' % (target, substitute)
+            else:
+                # Add missing path substitution entry
+                if not module.check_mode:
+                    sefcontext.add_equal(target, substitute)
+                changed = True
+                if module._diff:
+                    prepared_diff += '# Addition to semanage file context path substitutions\n'
+                    prepared_diff += '+%s = %s\n' % (target, substitute)
 
     except Exception as e:
         module.fail_json(msg="%s: %s\n" % (e.__class__.__name__, to_native(e)))
@@ -222,7 +283,7 @@ def semanage_fcontext_modify(module, result, target, ftype, setype, do_reload, s
     module.exit_json(changed=changed, seuser=seuser, serange=serange, **result)
 
 
-def semanage_fcontext_delete(module, result, target, ftype, do_reload, sestore=''):
+def semanage_fcontext_delete(module, result, target, ftype, setype, substitute, do_reload, sestore=''):
     ''' Delete SELinux file context mapping definition from the policy. '''
 
     changed = False
@@ -232,7 +293,8 @@ def semanage_fcontext_delete(module, result, target, ftype, do_reload, sestore='
         sefcontext = seobject.fcontextRecords(sestore)
         sefcontext.set_reload(do_reload)
         exists = semanage_fcontext_exists(sefcontext, target, ftype)
-        if exists:
+        substitute_exists = semanage_fcontext_substitute_exists(sefcontext, target)
+        if exists and substitute is None:
             # Remove existing entry
             orig_seuser, orig_serole, orig_setype, orig_serange = exists
 
@@ -243,6 +305,17 @@ def semanage_fcontext_delete(module, result, target, ftype, do_reload, sestore='
             if module._diff:
                 prepared_diff += '# Deletion to semanage file context mappings\n'
                 prepared_diff += '-%s      %s      %s:%s:%s:%s\n' % (target, ftype, exists[0], exists[1], exists[2], exists[3])
+        if substitute_exists and setype is None and ((substitute is not None and substitute_exists == substitute) or substitute is None):
+            # Remove existing path substitution entry
+            orig_substitute = substitute_exists
+
+            if not module.check_mode:
+                sefcontext.delete(target, orig_substitute)
+            changed = True
+
+            if module._diff:
+                prepared_diff += '# Deletion to semanage file context path substitutions\n'
+                prepared_diff += '-%s = %s\n' % (target, orig_substitute)
 
     except Exception as e:
         module.fail_json(msg="%s: %s\n" % (e.__class__.__name__, to_native(e)))
@@ -259,12 +332,23 @@ def main():
             ignore_selinux_state=dict(type='bool', default=False),
             target=dict(type='str', required=True, aliases=['path']),
             ftype=dict(type='str', default='a', choices=list(option_to_file_type_str.keys())),
-            setype=dict(type='str', required=True),
+            setype=dict(type='str'),
+            substitute=dict(type='str', aliases=['equal']),
             seuser=dict(type='str'),
             selevel=dict(type='str', aliases=['serange']),
             state=dict(type='str', default='present', choices=['absent', 'present']),
             reload=dict(type='bool', default=True),
         ),
+        mutually_exclusive=[
+            ('setype', 'substitute'),
+            ('substitute', 'ftype'),
+            ('substitute', 'seuser'),
+            ('substitute', 'selevel'),
+        ],
+        required_if=[
+            ('state', 'present', ('setype', 'substitute'), True),
+        ],
+
         supports_check_mode=True,
     )
     if not HAVE_SELINUX:
@@ -281,17 +365,18 @@ def main():
     target = module.params['target']
     ftype = module.params['ftype']
     setype = module.params['setype']
+    substitute = module.params['substitute']
     seuser = module.params['seuser']
     serange = module.params['selevel']
     state = module.params['state']
     do_reload = module.params['reload']
 
-    result = dict(target=target, ftype=ftype, setype=setype, state=state)
+    result = dict(target=target, ftype=ftype, setype=setype, substitute=substitute, state=state)
 
     if state == 'present':
-        semanage_fcontext_modify(module, result, target, ftype, setype, do_reload, serange, seuser)
+        semanage_fcontext_modify(module, result, target, ftype, setype, substitute, do_reload, serange, seuser)
     elif state == 'absent':
-        semanage_fcontext_delete(module, result, target, ftype, do_reload)
+        semanage_fcontext_delete(module, result, target, ftype, setype, substitute, do_reload)
     else:
         module.fail_json(msg='Invalid value of argument "state": {0}'.format(state))