Ticket #4148: 5079-fix_IE_cache_bugs_2.diff

django/core/handlers/base.py

@@ -3 +3 @@
 from django import http
 import sys
 
+def fix_IE_for_attach(request, response):
+    """
+    This function will prevent Django from serving a
+    Content-Disposition header while expecting the browser
+    to cache it. This leads to IE not allowing the client
+    to download.
+    """
+
+    offending_headers = ('no-cache','no-store',)
+    
+    try:
+        if 'MSIE' not in request.META['User-Agent'].upper():
+            return response
+    except KeyError:
+        return response
+
+    if response.has_header('Content-Disposition'):
+        del response['Pragma']
+        if response.has_header('Cache-Control'):
+            cache_control_values = [value.strip() for value in
+                                    response['Cache-Control'].split(',')
+                                    if value.strip().lower() not in
+                                    offending_headers                   ]
+
+            if len(cache_control_values) == 0:
+                del response['Cache-Control']
+            else:
+                response['Cache-Control'] = ', '.join(cache_control_values)
+        
+    return response
+
+def fix_IE_for_vary(request, response):
+    """
+    This function will fix the bug reported at
+    http://support.microsoft.com/kb/824847/en-us?spid=8722&sid=global
+    by clearing the Vary header whenever the mime-type is not safe
+    enough for Internet Explorer to handle.
+    """
+    
+    # a list of mime-types that are decreed "Vary-safe" for IE
+    safe_mime_types = ('text/html',
+                       'text/plain',
+                       'text/sgml',
+                       )
+
+    # establish that the user is using IE
+    try:
+        if 'MSIE' not in request.META['User-Agent'].upper():
+            return response
+    except KeyError:
+        return response
+
+
+    # IE will break
+    if response.mimetype.lower() not in safe_mime_types: 
+        try:
+            del response['Vary']
+            response['Pragma'] = 'no-cache'
+            response['Cache-Control'] = 'no-cache, must-revalidate'
+        except KeyError:
+            return response
+            
+    return response
+
 class BaseHandler(object):
     def __init__(self):
         self._request_middleware = self._view_middleware = self._response_middleware = self._exception_middleware = None
@@ -17 +81 @@
         from django.core import exceptions
         self._request_middleware = []
         self._view_middleware = []
-        self._response_middleware = []
+        # add processing for IE caching bugs
+        self._response_middleware = [fix_IE_for_vary,fix_IE_for_attach]
+            
         self._exception_middleware = []
         for middleware_path in settings.MIDDLEWARE_CLASSES:
             try: