ldap: Support alternative attrs to userAccountControl.

Fixes #17456.

The main tricky part has to do with what values the attribute should
have. LDAP defines a Boolean as
Boolean = "TRUE" / "FALSE"
so ideally we'd always see exactly those values. However,
although the issue is now marked as resolved, the discussion in
https://pagure.io/freeipa/issue/1259 shows how this may not always be
respected - meaning it makes sense for us to be more liberal in
interpreting these values.

docs/production/authentication-methods.md

@@ -212,17 +212,23 @@ corresponding LDAP attribute is `linkedinProfile` then you just need
 to add `'custom_profile_field__linkedin_profile': 'linkedinProfile'`
 to the `AUTH_LDAP_USER_ATTR_MAP`.
 
-#### Automatically deactivating users with Active Directory
+#### Automatically deactivating users
 
 Zulip supports synchronizing the
-disabled/deactivated status of users from Active Directory. You can
+disabled/deactivated status of users. If you're using Active Directory,
-configure this by uncommenting the sample line
+you can configure this by uncommenting the sample line
 `"userAccountControl": "userAccountControl",` in
 `AUTH_LDAP_USER_ATTR_MAP` (and restarting the Zulip server). Zulip
 will then treat users that are disabled via the "Disable Account"
 feature in Active Directory as deactivated in Zulip.
 
-Users disabled in active directory will be immediately unable to log in
+If you're using a different LDAP server which uses a boolean attribute
+which is `TRUE` or `YES` for users that should be deactivated and `FALSE`
+or `NO` otherwise. You can configure a mapping for `deactivated` in
+`AUTH_LDAP_USER_ATTR_MAP`. For example, `"deactivated": "nsAccountLock",` is a correct mapping for a
+[FreeIPA](https://www.freeipa.org/) LDAP database.
+
+Disabled users will be immediately unable to log in
 to Zulip, since Zulip queries the LDAP/Active Directory server on
 every login attempt. The user will be fully deactivated the next time
 your `manage.py sync_ldap_user_data` cron job runs (at which point

zerver/tests/test_auth_backends.py

@@ -5877,7 +5877,7 @@ class TestZulipLDAPUserPopulator(ZulipLDAPTestCase):
             ["WARNING:django_auth_ldap:Name too short! while authenticating hamlet"],
         )
 
-    def test_deactivate_user(self) -> None:
+    def test_deactivate_user_with_useraccountcontrol_attr(self) -> None:
         self.change_ldap_user_attr("hamlet", "userAccountControl", "2")
 
         with self.settings(
@@ -5893,6 +5893,50 @@ class TestZulipLDAPUserPopulator(ZulipLDAPTestCase):
             ],
         )
 
+    def test_deactivate_reactivate_user_with_deactivated_attr(self) -> None:
+        self.change_ldap_user_attr("hamlet", "someCustomAttr", "TRUE")
+
+        with self.settings(
+            AUTH_LDAP_USER_ATTR_MAP={"full_name": "cn", "deactivated": "someCustomAttr"}
+        ), self.assertLogs("zulip.ldap") as info_logs:
+            self.perform_ldap_sync(self.example_user("hamlet"))
+        hamlet = self.example_user("hamlet")
+        self.assertFalse(hamlet.is_active)
+        self.assertEqual(
+            info_logs.output,
+            [
+                "INFO:zulip.ldap:Deactivating user hamlet@zulip.com because they are disabled in LDAP."
+            ],
+        )
+
+        self.change_ldap_user_attr("hamlet", "someCustomAttr", "FALSE")
+        with self.settings(
+            AUTH_LDAP_USER_ATTR_MAP={"full_name": "cn", "deactivated": "someCustomAttr"}
+        ), self.assertLogs("zulip.ldap") as info_logs:
+            self.perform_ldap_sync(self.example_user("hamlet"))
+        hamlet.refresh_from_db()
+        self.assertTrue(hamlet.is_active)
+        self.assertEqual(
+            info_logs.output,
+            [
+                "INFO:zulip.ldap:Reactivating user hamlet@zulip.com because they are not disabled in LDAP."
+            ],
+        )
+
+        self.change_ldap_user_attr("hamlet", "someCustomAttr", "YESSS")
+        with self.settings(
+            AUTH_LDAP_USER_ATTR_MAP={"full_name": "cn", "deactivated": "someCustomAttr"}
+        ), self.assertLogs("django_auth_ldap") as ldap_logs, self.assertRaises(AssertionError):
+            self.perform_ldap_sync(self.example_user("hamlet"))
+        hamlet.refresh_from_db()
+        self.assertTrue(hamlet.is_active)
+        self.assertEqual(
+            ldap_logs.output,
+            [
+                "WARNING:django_auth_ldap:Invalid value 'YESSS' in the LDAP attribute mapped to deactivated while authenticating hamlet"
+            ],
+        )
+
     @mock.patch("zproject.backends.ZulipLDAPAuthBackendBase.sync_full_name_from_ldap")
     def test_dont_sync_disabled_ldap_user(self, fake_sync: mock.MagicMock) -> None:
         self.change_ldap_user_attr("hamlet", "userAccountControl", "2")

zproject/backends.py

@@ -477,6 +477,23 @@ def check_ldap_config() -> None:
         # Email search needs to be configured in this case.
         assert settings.AUTH_LDAP_USERNAME_ATTR and settings.AUTH_LDAP_REVERSE_EMAIL_SEARCH
 
+    # These two are alternatives approaches to deactivating users based on an ldap attribute
+    # and thus don't make sense to have enabled together.
+    assert not (
+        settings.AUTH_LDAP_USER_ATTR_MAP.get("userAccountControl")
+        and settings.AUTH_LDAP_USER_ATTR_MAP.get("deactivated")
+    )
+
+
+def ldap_should_sync_active_status() -> bool:
+    if "userAccountControl" in settings.AUTH_LDAP_USER_ATTR_MAP:
+        return True
+
+    if "deactivated" in settings.AUTH_LDAP_USER_ATTR_MAP:
+        return True
+
+    return False
+
 
 def find_ldap_users_by_email(email: str) -> List[_LDAPUser]:
     """
@@ -715,15 +732,30 @@ class ZulipLDAPAuthBackendBase(ZulipAuthMixin, LDAPBackend):
             else:
                 logging.warning("Could not parse %s field for user %s", avatar_attr_name, user.id)
 
-    def is_account_control_disabled_user(self, ldap_user: _LDAPUser) -> bool:
+    def is_user_disabled_in_ldap(self, ldap_user: _LDAPUser) -> bool:
-        """Implements the userAccountControl check for whether a user has been
+        """Implements checks for whether a user has been
-        disabled in an Active Directory server being integrated with
+        disabled in the LDAP server being integrated with
-        Zulip via LDAP."""
+        Zulip."""
+        if "userAccountControl" in settings.AUTH_LDAP_USER_ATTR_MAP:
             account_control_value = ldap_user.attrs[
                 settings.AUTH_LDAP_USER_ATTR_MAP["userAccountControl"]
             ][0]
-        ldap_disabled = bool(int(account_control_value) & LDAP_USER_ACCOUNT_CONTROL_DISABLED_MASK)
+            return bool(int(account_control_value) & LDAP_USER_ACCOUNT_CONTROL_DISABLED_MASK)
-        return ldap_disabled
+
+        assert "deactivated" in settings.AUTH_LDAP_USER_ATTR_MAP
+        attr_value = ldap_user.attrs[settings.AUTH_LDAP_USER_ATTR_MAP["deactivated"]][0]
+
+        # In the LDAP specification, a Boolean attribute should be
+        # *exactly* either "TRUE" or "FALSE". However,
+        # https://www.freeipa.org/page/V4/User_Life-Cycle_Management suggests
+        # that FreeIPA at least documents using Yes/No for booleans.
+        true_values = ["TRUE", "YES"]
+        false_values = ["FALSE", "NO"]
+        attr_value_upper = attr_value.upper()
+        assert (
+            attr_value_upper in true_values or attr_value_upper in false_values
+        ), f"Invalid value '{attr_value}' in the LDAP attribute mapped to deactivated"
+        return attr_value_upper in true_values
 
     def is_account_realm_access_forbidden(self, ldap_user: _LDAPUser, realm: Realm) -> bool:
         # org_membership takes priority over AUTH_LDAP_ADVANCED_REALM_ACCESS_CONTROL.
@@ -881,8 +913,8 @@ class ZulipLDAPAuthBackend(ZulipLDAPAuthBackendBase):
         if self.is_account_realm_access_forbidden(ldap_user, self._realm):
             raise ZulipLDAPException("User not allowed to access realm")
 
-        if "userAccountControl" in settings.AUTH_LDAP_USER_ATTR_MAP:  # nocoverage
+        if ldap_should_sync_active_status():  # nocoverage
-            ldap_disabled = self.is_account_control_disabled_user(ldap_user)
+            ldap_disabled = self.is_user_disabled_in_ldap(ldap_user)
             if ldap_disabled:
                 # Treat disabled users as deactivated in Zulip.
                 return_data["inactive_user"] = True
@@ -1012,8 +1044,8 @@ class ZulipLDAPUserPopulator(ZulipLDAPAuthBackendBase):
         user = get_user_by_delivery_email(username, ldap_user.realm)
         built = False
         # Synchronise the UserProfile with its LDAP attributes:
-        if "userAccountControl" in settings.AUTH_LDAP_USER_ATTR_MAP:
+        if ldap_should_sync_active_status():
-            user_disabled_in_ldap = self.is_account_control_disabled_user(ldap_user)
+            user_disabled_in_ldap = self.is_user_disabled_in_ldap(ldap_user)
             if user_disabled_in_ldap:
                 if user.is_active:
                     ldap_logger.info(

zproject/prod_settings_template.py

@@ -239,6 +239,9 @@ AUTH_LDAP_USER_ATTR_MAP = {
     ## who are disabled in LDAP/Active Directory (and reactivate users who are not).
     ## See docs for usage details and precise semantics.
     # "userAccountControl": "userAccountControl",
+    ## Alternatively, you can map "deactivated" to a boolean attribute
+    ## that is "TRUE" for deactivated users and "FALSE" otherwise.
+    # "deactivated": "nsAccountLock",
     ## Restrict access to organizations using an LDAP attribute.
     ## See https://zulip.readthedocs.io/en/latest/production/authentication-methods.html#restricting-ldap-user-access-to-specific-organizations
     # "org_membership": "department",