From 6be9589eb34f79914666c9d9e1e15bdb7fc44df2 Mon Sep 17 00:00:00 2001
From: "Derek J. Curtis" <djcurtis@summersetsoftware.com>
Date: Wed, 9 Dec 2015 18:07:02 +0700
Subject: [PATCH] Fixed #25900 -- Fixed regression in CommonMiddleware ETag
 support.

---
 django/middleware/common.py |  4 +++-
 docs/releases/1.9.1.txt     |  3 +++
 tests/middleware/tests.py   | 10 ++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/django/middleware/common.py b/django/middleware/common.py
index 5aeb746f81..3db925c894 100644
--- a/django/middleware/common.py
+++ b/django/middleware/common.py
@@ -120,7 +120,9 @@ class CommonMiddleware(object):
             if response.has_header('ETag'):
                 return get_conditional_response(
                     request,
-                    etag=response['ETag'],
+                    # get_conditional_response() requires an unquoted version
+                    # of the response's ETag.
+                    etag=response['ETag'].strip('"'),
                     response=response,
                 )
 
diff --git a/docs/releases/1.9.1.txt b/docs/releases/1.9.1.txt
index 98569a14df..e0b3b17ff9 100644
--- a/docs/releases/1.9.1.txt
+++ b/docs/releases/1.9.1.txt
@@ -19,3 +19,6 @@ Bugfixes
 
 * Fixed a state bug when migrating a ``SeparateDatabaseAndState`` operation
   backwards (:ticket:`25896`).
+
+* Fixed a regression in ``CommonMiddleware`` causing ``If-None-Match`` checks
+  to always return HTTP 200 (:ticket:`25900`).
diff --git a/tests/middleware/tests.py b/tests/middleware/tests.py
index 7ccfd919cc..3e18ee7645 100644
--- a/tests/middleware/tests.py
+++ b/tests/middleware/tests.py
@@ -291,6 +291,16 @@ class CommonMiddlewareTest(SimpleTestCase):
         res = StreamingHttpResponse(['content'])
         self.assertFalse(CommonMiddleware().process_response(req, res).has_header('ETag'))
 
+    @override_settings(USE_ETAGS=True)
+    def test_if_none_match(self):
+        first_req = HttpRequest()
+        first_res = CommonMiddleware().process_response(first_req, HttpResponse('content'))
+        second_req = HttpRequest()
+        second_req.method = 'GET'
+        second_req.META['HTTP_IF_NONE_MATCH'] = first_res['ETag']
+        second_res = CommonMiddleware().process_response(second_req, HttpResponse('content'))
+        self.assertEqual(second_res.status_code, 304)
+
     # Other tests
 
     @override_settings(DISALLOWED_USER_AGENTS=[re.compile(r'foo')])