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[1.6.x] Prevented leaking the CSRF token through caching.

This is a security fix. Disclosure will follow shortly.

Backport of c083e38 from master
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1 parent 4352a50 commit d63e20942f3024f24cb8cd85a49461ba8a9b6736 @aaugustin aaugustin committed with timgraham Apr 20, 2014
Showing with 37 additions and 1 deletion.
  1. +9 −1 django/middleware/cache.py
  2. +28 −0 tests/cache/tests.py
View
@@ -47,7 +47,8 @@
from django.conf import settings
from django.core.cache import get_cache, 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):
@@ -90,8 +91,15 @@ 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
@@ -19,12 +19,14 @@
from django.core.cache import get_cache
from django.core.cache.backends.base import (CacheKeyWarning,
InvalidCacheBackendError)
+from django.core.context_processors import csrf
from django.db import router, transaction
from django.core.cache.utils import make_template_fragment_key
from django.http import (HttpResponse, HttpRequest, StreamingHttpResponse,
QueryDict)
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
@@ -1578,6 +1580,10 @@ 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',
@@ -1797,6 +1803,28 @@ 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',
CACHE_MIDDLEWARE_SECONDS=1,

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