feat: handle 500 errors that occur when user is unauthenticated during LTI 1.1 launch

In the LTI 1.1 launch handler, we set the user context, including the user_id. We do this by calling to the LMS's DjangoXBlockUserService to get information about the user. Sometimes, the user is unauthenticated. Sometimes, this is because the user is a web crawler. Other times, the user is a real user, but we do not know why the user is unauthenticated. We have some theories, but we have been unable to confirm them. Regardless, we should not surface a 500 error to the user.

This commit adds handling for the LtiError that is raised when a user is unauthenticated during an LTI 1.1 launch. It catches the LtiError and renders an error page. The error page that was used for LTI 1.3 launches, formerly named "lti_1p3_launch_error.html", has been renamed to "lti_launch_error.html" to reflect the fact that it is used for both LTI 1.1 and 1.3 launches. It was modified to remove the reference to the version of LTI used by the XBlock; these details are unnecessary for a learner, and removing them allows us to reuse a single template for both LTI versions.

Author: michaelroytman

lti_consumer/__init__.py

@@ -4,4 +4,4 @@
 from .apps import LTIConsumerApp
 from .lti_xblock import LtiConsumerXBlock
 
-__version__ = '4.4.0'
+__version__ = '4.5.0'

lti_consumer/lti_xblock.py

@@ -745,7 +745,11 @@ def role(self):
         """
         Get system user role and convert it to LTI role.
         """
-        role = self.runtime.service(self, 'user').get_current_user().opt_attrs.get('edx-platform.user_role', 'student')
+        user = self.runtime.service(self, 'user').get_current_user()
+        if not user.opt_attrs["edx-platform.is_authenticated"]:
+            raise LtiError(self.ugettext("Could not get user data for current request"))
+
+        role = user.opt_attrs.get('edx-platform.user_role', 'student')
         return ROLE_MAP.get(role, 'Student,Learner')
 
     @property
@@ -978,6 +982,10 @@ def extract_real_user_data(self):
         Extract and return real user data from the runtime
         """
         user = self.runtime.service(self, 'user').get_current_user()
+
+        if not user.opt_attrs["edx-platform.is_authenticated"]:
+            raise LtiError(self.ugettext("Could not get user data for current request"))
+
         user_data = {
             'user_email': None,
             'user_username': None,
@@ -1080,10 +1088,21 @@ def lti_launch_handler(self, request, suffix=''):  # pylint: disable=unused-argu
         Returns:
             webob.response: HTML LTI launch form
         """
-        real_user_data = self.extract_real_user_data()
-
         lti_consumer = self._get_lti_consumer()
 
+        # Occassionally, users try to do an LTI launch while they are unauthenticated. It is not known why this occurs.
+        # Sometimes, it is due to a web crawlers; other times, it is due to actual users of the platform. Regardless,
+        # return a 400 response with an appropriate error template.
+        try:
+            real_user_data = self.extract_real_user_data()
+            user_id = self.user_id
+            role = self.role
+            result_sourcedid = self.lis_result_sourcedid
+        except LtiError:
+            loader = ResourceLoader(__name__)
+            template = loader.render_django_template('/templates/html/lti_launch_error.html')
+            return Response(template, status=400, content_type='text/html')
+
         username = None
         email = None
         if self.ask_to_send_username and real_user_data['user_username']:
@@ -1092,12 +1111,13 @@ def lti_launch_handler(self, request, suffix=''):  # pylint: disable=unused-argu
             email = real_user_data['user_email']
 
         lti_consumer.set_user_data(
-            self.user_id,
-            self.role,
-            result_sourcedid=self.lis_result_sourcedid,
+            user_id,
+            role,
+            result_sourcedid=result_sourcedid,
             person_sourcedid=username,
             person_contact_email_primary=email
         )
+
         lti_consumer.set_context_data(
             self.context_id,
             self.course.display_name_with_default,

lti_consumer/plugin/views.py

@@ -150,7 +150,7 @@ def launch_gate_endpoint(request, suffix=None):  # pylint: disable=unused-argume
     usage_id = request.GET.get('login_hint')
     if not usage_id:
         log.info('The `login_hint` query param in the request is missing or empty.')
-        return render(request, 'html/lti_1p3_launch_error.html', status=HTTP_400_BAD_REQUEST)
+        return render(request, 'html/lti_launch_error.html', status=HTTP_400_BAD_REQUEST)
 
     try:
         usage_key = UsageKey.from_string(usage_id)
@@ -161,7 +161,7 @@ def launch_gate_endpoint(request, suffix=None):  # pylint: disable=unused-argume
             exc,
             exc_info=True
         )
-        return render(request, 'html/lti_1p3_launch_error.html', status=HTTP_404_NOT_FOUND)
+        return render(request, 'html/lti_launch_error.html', status=HTTP_404_NOT_FOUND)
 
     try:
         lti_config = LtiConfiguration.objects.get(
@@ -173,7 +173,7 @@ def launch_gate_endpoint(request, suffix=None):  # pylint: disable=unused-argume
 
     if lti_config.version != LtiConfiguration.LTI_1P3:
         log.error("The LTI Version of configuration %s is not LTI 1.3", lti_config)
-        return render(request, 'html/lti_1p3_launch_error.html', status=HTTP_404_NOT_FOUND)
+        return render(request, 'html/lti_launch_error.html', status=HTTP_404_NOT_FOUND)
 
     context = {}
 
@@ -269,7 +269,7 @@ def launch_gate_endpoint(request, suffix=None):  # pylint: disable=unused-argume
             exc,
             exc_info=True
         )
-        return render(request, 'html/lti_1p3_launch_error.html', context, status=HTTP_400_BAD_REQUEST)
+        return render(request, 'html/lti_launch_error.html', context, status=HTTP_400_BAD_REQUEST)
     except AssertionError as exc:
         log.warning(
             "Permission on LTI block %r denied for user %r: %s",

…templates/html/lti_1p3_launch_error.html …mer/templates/html/lti_launch_error.htmllti_consumer/templates/html/lti_1p3_launch_error.html renamed to lti_consumer/templates/html/lti_launch_error.html lti_consumer/templates/html/lti_1p3_launch_error.html renamed to lti_consumer/templates/html/lti_launch_error.html

@@ -7,7 +7,7 @@
     </head>
     <body>
         <p>
-            <b>{% trans "There was an error while launching the LTI 1.3 tool." %}</b>
+            <b>{% trans "There was an error while launching the LTI tool." %}</b>
         </p>
         <p>
             {% trans "If you're seeing this on a live course, please contact the course staff." %}

lti_consumer/tests/unit/plugin/test_views.py

@@ -196,7 +196,7 @@ def test_launch_callback_endpoint_fails(self):
         self.assertEqual(response.status_code, 400)
 
         response_body = response.content.decode('utf-8')
-        self.assertIn("There was an error while launching the LTI 1.3 tool.", response_body)
+        self.assertIn("There was an error while launching the LTI tool.", response_body)
         self.assertNotIn("% trans", response_body)
 
         with patch(

lti_consumer/tests/unit/test_lti_xblock.py

@@ -146,29 +146,40 @@ def test_role(self):
         """
         fake_user = Mock()
         fake_user.opt_attrs = {
-            'edx-platform.user_role': 'student'
+            'edx-platform.user_role': 'student',
+            'edx-platform.is_authenticated': True,
         }
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
         self.assertEqual(self.xblock.role, 'Student,Learner')
 
         fake_user.opt_attrs = {
-            'edx-platform.user_role': 'guest'
+            'edx-platform.user_role': 'guest',
+            'edx-platform.is_authenticated': True,
         }
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
         self.assertEqual(self.xblock.role, 'Student,Learner')
 
         fake_user.opt_attrs = {
-            'edx-platform.user_role': 'staff'
+            'edx-platform.user_role': 'staff',
+            'edx-platform.is_authenticated': True,
         }
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
         self.assertEqual(self.xblock.role, 'Administrator')
 
         fake_user.opt_attrs = {
-            'edx-platform.user_role': 'instructor'
+            'edx-platform.user_role': 'instructor',
+            'edx-platform.is_authenticated': True,
         }
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
         self.assertEqual(self.xblock.role, 'Instructor')
 
+        fake_user.opt_attrs = {
+            'edx-platform.user_role': 'student',
+            'edx-platform.is_authenticated': False,
+        }
+        with self.assertRaises(LtiError):
+            _ = self.xblock.role
+
     def test_course(self):
         """
         Test `course` calls modulestore.get_course
@@ -593,7 +604,8 @@ def test_get_real_user_callable(self):
         fake_user.emails = [fake_user_email]
         fake_username = 'fake'
         fake_user.opt_attrs = {
-            "edx-platform.username": fake_username
+            "edx-platform.username": fake_username,
+            "edx-platform.is_authenticated": True,
         }
 
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
@@ -616,14 +628,29 @@ def test_get_real_user_callable_with_language_preference(self):
         fake_user.opt_attrs = {
             "edx-platform.user_preferences": {
                 "pref-lang": "en"
-            }
+            },
+            "edx-platform.is_authenticated": True,
         }
 
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
 
         real_user_data = self.xblock.extract_real_user_data()
         self.assertEqual(real_user_data['user_language'], pref_language)
 
+    def test_unauthenticated_user(self):
+        """
+        Test that an LtiError is raised when the user is unauthenticated.
+        """
+        fake_user = Mock()
+        fake_user.opt_attrs = {
+            "edx-platform.is_authenticated": False,
+        }
+
+        self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
+
+        with self.assertRaises(LtiError):
+            self.xblock.extract_real_user_data()
+
 
 class TestStudentView(TestLtiConsumerXBlock):
     """
@@ -734,7 +761,8 @@ def setUp(self):
         fake_user.emails = [fake_user_email]
         fake_username = 'fake'
         fake_user.opt_attrs = {
-            "edx-platform.username": fake_username
+            "edx-platform.username": fake_username,
+            "edx-platform.is_authenticated": True,
         }
 
         self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
@@ -757,6 +785,36 @@ def test_generate_launch_request_called(self, mock_course):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.content_type, 'text/html')
 
+    @patch('lti_consumer.lti_xblock.LtiConsumerXBlock.course')
+    def test_lti_launch_handler_unauthenticated(self, mock_course):
+        """
+        Test that a 400 response an an appropriate template is rendered when a user is unauthenticated
+        during an LTI launch according to the LMS's user service.
+        """
+        provider = 'lti_provider'
+        key = 'test'
+        secret = 'secret'
+        type(mock_course).lti_passports = PropertyMock(return_value=[f"{provider}:{key}:{secret}"])
+
+        fake_user = Mock()
+        fake_user_email = 'abc@example.com'
+        fake_user.emails = [fake_user_email]
+        fake_username = 'fake'
+        fake_user.opt_attrs = {
+            "edx-platform.username": fake_username,
+            "edx-platform.is_authenticated": True,
+        }
+        self.xblock.runtime.service(self, 'user').get_current_user = Mock(return_value=fake_user)
+
+        request = make_request('', 'GET')
+        response = self.xblock.lti_launch_handler(request)
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.content_type, 'text/html')
+
+        response_body = response.body.decode('utf-8')
+        self.assertIn("There was an error while launching the LTI tool.", response_body)
+
     @patch('lti_consumer.lti_xblock.LtiConsumerXBlock.course')
     @patch('lti_consumer.lti_xblock.LtiConsumerXBlock.user_id', PropertyMock(return_value=FAKE_USER_ID))
     def test_publish_tracking_event(self, mock_course):