From 8f065bba6b262fe7b1bfde15e70bcbc7e4602a48 Mon Sep 17 00:00:00 2001
From: Adrian Holovaty <adrian@holovaty.com>
Date: Fri, 18 Aug 2006 03:12:36 +0000
Subject: [PATCH] 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 | 24 ++++++++++++++++++++++++
 docs/middleware.txt       | 18 +++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/django/middleware/http.py b/django/middleware/http.py
index 12d0c0f6836..3ebd8ffd1ab 100644
--- a/django/middleware/http.py
+++ b/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
diff --git a/docs/middleware.txt b/docs/middleware.txt
index bad00fd890c..efc4d895699 100644
--- a/docs/middleware.txt
+++ b/docs/middleware.txt
@@ -63,7 +63,7 @@ Adds a few conveniences for perfectionists:
   last component in the path contains a period. So ``foo.com/bar`` is
   redirected to ``foo.com/bar/``, but ``foo.com/bar/file.txt`` is passed
   through unchanged.
-  
+
   If ``PREPEND_WWW`` is ``True``, URLs that lack a leading "www." will be
   redirected to the same URL with a leading "www."
 
@@ -101,6 +101,22 @@ Handles conditional GET operations. If the response has a ``ETag`` or
 Also removes the content from any response to a HEAD request and sets the
 ``Date`` and ``Content-Length`` response-headers.
 
+django.middleware.http.SetRemoteAddrFromForwardedFor
+----------------------------------------------------
+
+**New in Django development version**
+
+Sets ``request['REMOTE_ADDR']`` based on ``request.['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``.
+
+**Important note:** 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``.
+
 django.contrib.sessions.middleware.SessionMiddleware
 ----------------------------------------------------