Fixed #2552 -- Added SetRemoteAddrFromForwardedFor middleware and documentation. Thanks, Ian Holsman

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3602 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/middleware/http.py

@@ -35,3 +35,27 @@ class ConditionalGetMiddleware(object):
             response.content = ''
 
         return response
+
+class SetRemoteAddrFromForwardedFor(object):
+    """
+    Middleware that sets REMOTE_ADDR based on HTTP_X_FORWARDED_FOR, if the
+    latter is set. This is useful if you're sitting behind a reverse proxy that
+    causes each request's REMOTE_ADDR to be set to 127.0.0.1.
+
+    Note that this does NOT validate HTTP_X_FORWARDED_FOR. If you're not behind
+    a reverse proxy that sets HTTP_X_FORWARDED_FOR automatically, do not use
+    this middleware. Anybody can spoof the value of HTTP_X_FORWARDED_FOR, and
+    because this sets REMOTE_ADDR based on HTTP_X_FORWARDED_FOR, that means
+    anybody can "fake" their IP address. Only use this when you can absolutely
+    trust the value of HTTP_X_FORWARDED_FOR.
+    """
+    def process_request(self, request):
+        try:
+            real_ip = request.META['HTTP_X_FORWARDED_FOR']
+        except KeyError:
+            return None
+        else:
+            # HTTP_X_FORWARDED_FOR can be a comma-separated list of IPs.
+            # Take just the first one.
+            real_ip = real_ip.split(",")[0]
+            request.META['REMOTE_ADDR'] = real_ip