return 404 if the exam code does not exist

edx_proctoring/callbacks.py

@@ -5,6 +5,8 @@ Various callback paths
 from django.template import Context, loader
 from django.http import HttpResponse
 
+from edx_proctoring.exceptions import StudentExamAttemptDoesNotExistsException
+
 from edx_proctoring.api import (
     start_exam_attempt_by_code,
 )
@@ -22,7 +24,13 @@ def start_exam_callback(request, attempt_code):  # pylint: disable=unused-argume
     """
 
     # start the exam!
-    start_exam_attempt_by_code(attempt_code)
+    try:
+        start_exam_attempt_by_code(attempt_code)
+    except StudentExamAttemptDoesNotExistsException:
+        return HttpResponse(
+            content='That exam code is not valid',
+            status=404
+        )
 
     template = loader.get_template('proctoring/proctoring_launch_callback.html')
 

edx_proctoring/tests/test_views.py

@@ -755,6 +755,18 @@ class TestStudentProctoredExamAttempt(LoggedInTestCase):
         attempt = get_exam_attempt_by_id(attempt_id)
         self.assertIsNotNone(attempt['started_at'])
 
+    def test_bad_exam_code_callback(self):
+        """
+        Assert that we get a 404 when doing a callback on an exam code that does not exist
+        """
+        response = self.client.get(
+            reverse(
+                'edx_proctoring.anonymous.proctoring_launch_callback.start_exam',
+                args=['foo']
+            )
+        )
+        self.assertEqual(response.status_code, 404)
+
 
 class TestExamAllowanceView(LoggedInTestCase):
     """