From 38ebe23d6a784bd1ea15c72432a9ddedad97f72b Mon Sep 17 00:00:00 2001
From: "Dave St.Germain" <dstgermain@edx.org>
Date: Tue, 15 Jan 2019 11:46:12 -0500
Subject: [PATCH] Obscure the user id going to the backend

---
 edx_proctoring/api.py   |  6 +++---
 edx_proctoring/utils.py | 15 +++++++++++++++
 edx_proctoring/views.py |  3 ++-
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/edx_proctoring/api.py b/edx_proctoring/api.py
index 986ce084014..1029f2e9221 100644
--- a/edx_proctoring/api.py
+++ b/edx_proctoring/api.py
@@ -7,7 +7,6 @@
 from __future__ import absolute_import
 
 from datetime import datetime, timedelta
-import hashlib
 import logging
 import uuid
 import pytz
@@ -50,7 +49,8 @@
 
 from edx_proctoring.utils import (
     humanized_time,
-    emit_event
+    emit_event,
+    obscured_user_id,
 )
 
 from edx_proctoring.backends import get_backend_provider
@@ -600,7 +600,7 @@ def create_exam_attempt(exam_id, user_id, taking_as_proctored=False):
         scheme = 'https' if getattr(settings, 'HTTPS', 'on') == 'on' else 'http'
         lms_host = '{scheme}://{hostname}'.format(scheme=scheme, hostname=settings.SITE_NAME)
 
-        obs_user_id = hashlib.sha1((u'%s%s' % (exam['course_id'], user_id)).encode('ascii')).hexdigest()
+        obs_user_id = obscured_user_id(user_id, exam['backend'])
 
         # get the name of the user, if the service is available
         full_name = None
diff --git a/edx_proctoring/utils.py b/edx_proctoring/utils.py
index a3322129ec6..86a8c3640fa 100644
--- a/edx_proctoring/utils.py
+++ b/edx_proctoring/utils.py
@@ -5,9 +5,13 @@
 from __future__ import absolute_import
 
 from datetime import datetime, timedelta
+import hashlib
+import hmac
 import logging
 import pytz
+import six
 
+from django.conf import settings
 from django.utils.translation import ugettext as _
 
 from opaque_keys.edx.keys import CourseKey
@@ -216,3 +220,14 @@ def _emit_event(name, context, data):
             'Analytics tracker not properly configured. '
             'If this message appears in a production environment, please investigate'
         )
+
+
+def obscured_user_id(user_id, *extra):
+    """
+    Obscures the user id, returning a sha1 hash
+    Any extra information can be added to the hash
+    """
+    obs_hash = hmac.new(settings.SECRET_KEY.encode('ascii'), digestmod=hashlib.sha1)
+    obs_hash.update(six.text_type(user_id))
+    obs_hash.update(u''.join(six.text_type(ext) for ext in extra))
+    return obs_hash.hexdigest()
diff --git a/edx_proctoring/views.py b/edx_proctoring/views.py
index 12a9a019b37..84e1c18240c 100644
--- a/edx_proctoring/views.py
+++ b/edx_proctoring/views.py
@@ -72,6 +72,7 @@
     get_time_remaining_for_attempt,
     locate_attempt_by_attempt_code,
     humanized_time,
+    obscured_user_id,
 )
 
 ATTEMPTS_PER_PAGE = 25
@@ -1000,7 +1001,7 @@ def get(self, request, course_id, exam_id=None):
             backend = get_backend_provider(exam)
             if backend:
                 user = {
-                    'id': request.user.id,
+                    'id': obscured_user_id(request.user.id, exam['backend']),
                     'full_name': request.user.get_full_name(),
                     'email': request.user.email
                 }