feat: tpa automatic logout (#32193)

* feat: tpa automatic logout

* chore: modify toggle documentations

* chore: check TPA_AUTOMATIC_LOGOUT_ENABLED in _show_tpa_logout_link

* docs: modify method doc

lms/envs/common.py

@@ -1216,6 +1216,18 @@
 TPA_PROVIDER_BURST_THROTTLE = '10/min'
 TPA_PROVIDER_SUSTAINED_THROTTLE = '50/hr'
 
+# .. toggle_name: TPA_AUTOMATIC_LOGOUT_ENABLED
+# .. toggle_implementation: DjangoSetting
+# .. toggle_default: False
+# .. toggle_description: Redirect the user to the TPA logout URL if this flag is enabled, the
+#   TPA logout URL is configured, and the user logs in through TPA.
+# .. toggle_use_cases: opt_in
+# .. toggle_warning: Enabling this toggle skips rendering logout.html, which is used to log the user out
+#   from the different IDAs. To ensure the user is logged out of all the IDAs be sure to redirect
+#   back to <LMS>/logout after logging out of the TPA.
+# .. toggle_creation_date: 2023-05-07
+TPA_AUTOMATIC_LOGOUT_ENABLED = False
+
 ################################## TEMPLATE CONFIGURATION #####################################
 # Mako templating
 import tempfile  # pylint: disable=wrong-import-position,wrong-import-order

openedx/core/djangoapps/user_authn/views/logout.py

@@ -8,6 +8,7 @@
 import bleach
 from django.conf import settings
 from django.contrib.auth import logout
+from django.shortcuts import redirect
 from django.utils.http import urlencode
 from django.views.generic import TemplateView
 from oauth2_provider.models import Application
@@ -83,6 +84,17 @@ def dispatch(self, request, *args, **kwargs):
         delete_logged_in_cookies(response)
 
         mark_user_change_as_expected(None)
+
+        # Redirect to tpa_logout_url if TPA_AUTOMATIC_LOGOUT_ENABLED is set to True and if
+        # tpa_logout_url is configured.
+        #
+        # NOTE: This step skips rendering logout.html, which is used to log the user out from the
+        # different IDAs. To ensure the user is logged out of all the IDAs be sure to redirect
+        # back to <LMS>/logout after logging out of the TPA.
+        if getattr(settings, 'TPA_AUTOMATIC_LOGOUT_ENABLED', False):
+            if self.tpa_logout_url:
+                return redirect(self.tpa_logout_url)
+
         return response
 
     def _build_logout_url(self, url):
@@ -113,13 +125,18 @@ def _is_enterprise_target(self, url):
     def _show_tpa_logout_link(self, target, referrer):
         """
         Return Boolean value indicating if TPA logout link needs to displayed or not.
-        We display TPA logout link when user has active SSO session and logout flow is
-        triggered via learner portal.
+        We display TPA logout link when user has active SSO session, logout flow is
+        triggered via learner portal and TPA_AUTOMATIC_LOGOUT_ENABLED toggle is False.
         Args:
             target: url of the page to land after logout
             referrer: url of the page where logout request initiated
         """
-        if bool(target == self.default_target and self.tpa_logout_url) and settings.LEARNER_PORTAL_URL_ROOT in referrer:
+        tpa_automatic_logout_enabled = getattr(settings, 'TPA_AUTOMATIC_LOGOUT_ENABLED', False)
+        if (
+            bool(target == self.default_target and self.tpa_logout_url) and
+            settings.LEARNER_PORTAL_URL_ROOT in referrer and
+            not tpa_automatic_logout_enabled
+        ):
             return True
 
         return False

openedx/core/djangoapps/user_authn/views/tests/test_logout.py

@@ -196,6 +196,33 @@ def test_learner_portal_logout_having_idp_logout_url(self):
             }
             self.assertDictContainsSubset(expected, response.context_data)
 
+    @mock.patch('django.conf.settings.TPA_AUTOMATIC_LOGOUT_ENABLED', True)
+    def test_automatic_tpa_logout_url_redirect(self):
+        """
+        Test user automatically redirected to tpa logout_url
+        when TPA_AUTOMATIC_LOGOUT is set to True.
+        """
+        idp_logout_url = 'http://mock-idp.com/logout'
+        client = self._create_oauth_client()
+
+        with mock.patch(
+            'openedx.core.djangoapps.user_authn.views.logout.tpa_pipeline.get_idp_logout_url_from_running_pipeline'
+        ) as mock_idp_logout_url:
+            mock_idp_logout_url.return_value = idp_logout_url
+            self._authenticate_with_oauth(client)
+            response = self.client.get(reverse('logout'))
+            assert response.status_code == 302
+            assert response.url == idp_logout_url
+
+    @mock.patch('django.conf.settings.TPA_AUTOMATIC_LOGOUT_ENABLED', True)
+    def test_no_automatic_tpa_logout_without_logout_url(self):
+        """
+        Test user is NOT automatically redirected when tpa logout_url is not set
+        even if TPA_AUTOMATIC_LOGOUT is set to True.
+        """
+        client = self._create_oauth_client()
+        self._assert_session_logged_out(client)
+
     @ddt.data(
         ('%22%3E%3Cscript%3Ealert(%27xss%27)%3C/script%3E', 'edx.org'),
     )