From 79956d06946c881cb71958f27a12f62b9cab8de5 Mon Sep 17 00:00:00 2001
From: Mark Lavin <mlavin@caktusgroup.com>
Date: Mon, 14 Apr 2014 19:44:05 -0400
Subject: [PATCH] Fixed #22440 -- Updated ConditionalGetMiddleware to comply
 with RFC 2616.

---
 django/middleware/http.py |  9 +++++++--
 tests/middleware/tests.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/django/middleware/http.py b/django/middleware/http.py
index 8e4bc55881..60fb194704 100644
--- a/django/middleware/http.py
+++ b/django/middleware/http.py
@@ -14,7 +14,10 @@ class ConditionalGetMiddleware(object):
         if not response.streaming and not response.has_header('Content-Length'):
             response['Content-Length'] = str(len(response.content))
 
-        if response.has_header('ETag'):
+        # If-None-Match must be ignored if original result would be anything
+        # other than a 2XX or 304 status. 304 status would result in no change.
+        # http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26
+        if 200 <= response.status_code < 300 and response.has_header('ETag'):
             if_none_match = request.META.get('HTTP_IF_NONE_MATCH')
             if if_none_match == response['ETag']:
                 # Setting the status is enough here. The response handling path
@@ -22,7 +25,9 @@ class ConditionalGetMiddleware(object):
                 # http.conditional_content_removal()).
                 response.status_code = 304
 
-        if response.has_header('Last-Modified'):
+        # If-Modified-Since must be ignored if the original result was not a 200.
+        # http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.25
+        if response.status_code == 200 and response.has_header('Last-Modified'):
             if_modified_since = request.META.get('HTTP_IF_MODIFIED_SINCE')
             if if_modified_since is not None:
                 if_modified_since = parse_http_date_safe(if_modified_since)
diff --git a/tests/middleware/tests.py b/tests/middleware/tests.py
index 7df1d04418..556e07f72c 100644
--- a/tests/middleware/tests.py
+++ b/tests/middleware/tests.py
@@ -366,6 +366,19 @@ class ConditionalGetMiddlewareTest(TestCase):
         self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
         self.assertEqual(self.resp.status_code, 200)
 
+    def test_if_none_match_and_redirect(self):
+        self.req.META['HTTP_IF_NONE_MATCH'] = self.resp['ETag'] = 'spam'
+        self.resp['Location'] = '/'
+        self.resp.status_code = 301
+        self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(self.resp.status_code, 301)
+
+    def test_if_none_match_and_client_error(self):
+        self.req.META['HTTP_IF_NONE_MATCH'] = self.resp['ETag'] = 'spam'
+        self.resp.status_code = 400
+        self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(self.resp.status_code, 400)
+
     @override_settings(USE_ETAGS=True)
     def test_etag(self):
         req = HttpRequest()
@@ -419,6 +432,21 @@ class ConditionalGetMiddlewareTest(TestCase):
         self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
         self.assertEqual(self.resp.status_code, 200)
 
+    def test_if_modified_since_and_redirect(self):
+        self.req.META['HTTP_IF_MODIFIED_SINCE'] = 'Sat, 12 Feb 2011 17:38:44 GMT'
+        self.resp['Last-Modified'] = 'Sat, 12 Feb 2011 17:35:44 GMT'
+        self.resp['Location'] = '/'
+        self.resp.status_code = 301
+        self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(self.resp.status_code, 301)
+
+    def test_if_modified_since_and_client_error(self):
+        self.req.META['HTTP_IF_MODIFIED_SINCE'] = 'Sat, 12 Feb 2011 17:38:44 GMT'
+        self.resp['Last-Modified'] = 'Sat, 12 Feb 2011 17:35:44 GMT'
+        self.resp.status_code = 400
+        self.resp = ConditionalGetMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(self.resp.status_code, 400)
+
 
 class XFrameOptionsMiddlewareTest(TestCase):
     """