Permalink
Browse files

Prevented leaking the CSRF token through caching.

This is a security fix. Disclosure will follow shortly.
  • Loading branch information...
1 parent 8b93b31 commit c083e3815aec23b99833da710eea574e6f2e8566 @aaugustin aaugustin committed with timgraham Apr 20, 2014
Showing with 36 additions and 1 deletion.
  1. +9 −1 django/middleware/cache.py
  2. +27 −0 tests/cache/tests.py
View
@@ -45,7 +45,8 @@
from django.conf import settings
from django.core.cache import caches, DEFAULT_CACHE_ALIAS
-from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age
+from django.utils.cache import (get_cache_key, get_max_age, has_vary_header,
+ learn_cache_key, patch_response_headers)
class UpdateCacheMiddleware(object):
@@ -77,8 +78,15 @@ def process_response(self, request, response):
if not self._should_update_cache(request, response):
# We don't need to update the cache, just return.
return response
+
if response.streaming or response.status_code != 200:
return response
+
+ # Don't cache responses that set a user-specific (and maybe security
+ # sensitive) cookie in response to a cookie-less request.
+ if not request.COOKIES and response.cookies and has_vary_header(response, 'Cookie'):
+ return response
+
# Try to get the timeout from the "max-age" section of the "Cache-
# Control" header before reverting to using the default cache_timeout
# length.
View
@@ -18,11 +18,13 @@
from django.core import management
from django.core.cache import (cache, caches, CacheKeyWarning,
InvalidCacheBackendError, DEFAULT_CACHE_ALIAS)
+from django.core.context_processors import csrf
from django.db import connection, connections, router, transaction
from django.core.cache.utils import make_template_fragment_key
from django.http import HttpResponse, StreamingHttpResponse
from django.middleware.cache import (FetchFromCacheMiddleware,
UpdateCacheMiddleware, CacheMiddleware)
+from django.middleware.csrf import CsrfViewMiddleware
from django.template import Template
from django.template.response import TemplateResponse
from django.test import TestCase, TransactionTestCase, RequestFactory, override_settings
@@ -1741,6 +1743,10 @@ def hello_world_view(request, value):
return HttpResponse('Hello World %s' % value)
+def csrf_view(request):
+ return HttpResponse(csrf(request)['csrf_token'])
+
+
@override_settings(
CACHE_MIDDLEWARE_ALIAS='other',
CACHE_MIDDLEWARE_KEY_PREFIX='middlewareprefix',
@@ -1905,6 +1911,27 @@ def test_view_decorator(self):
response = other_with_prefix_view(request, '16')
self.assertEqual(response.content, b'Hello World 16')
+ def test_sensitive_cookie_not_cached(self):
+ """
+ Django must prevent caching of responses that set a user-specific (and
+ maybe security sensitive) cookie in response to a cookie-less request.
+ """
+ csrf_middleware = CsrfViewMiddleware()
+ cache_middleware = CacheMiddleware()
+
+ request = self.factory.get('/view/')
+ self.assertIsNone(cache_middleware.process_request(request))
+
+ csrf_middleware.process_view(request, csrf_view, (), {})
+
+ response = csrf_view(request)
+
+ response = csrf_middleware.process_response(request, response)
+ response = cache_middleware.process_response(request, response)
+
+ # Inserting a CSRF cookie in a cookie-less request prevented caching.
+ self.assertIsNone(cache_middleware.process_request(request))
+
@override_settings(
CACHE_MIDDLEWARE_KEY_PREFIX='settingsprefix',

0 comments on commit c083e38

Please sign in to comment.