From 5e0700418dc27b645edbe33c744daff93cd66618 Mon Sep 17 00:00:00 2001
From: Senthil Kumaran <senthil@uthcode.com>
Date: Sat, 30 Jul 2016 23:24:16 -0700
Subject: [PATCH] Prevent HTTPoxy attack (CVE-2016-1000110)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which
indicates that the script is in CGI mode.

Issue #27568 Reported and patch contributed by Rémi Rampin.

Upstream-Status: Backport
CVE: CVE-2016-1000110

Signed-off-by: Armin Kuster <akuster@mvista.com>

---
 Doc/howto/urllib2.rst          |  5 +++++
 Doc/library/urllib.request.rst | 13 +++++++++++++
 Lib/test/test_urllib.py        | 13 +++++++++++++
 Lib/urllib/request.py          |  7 +++++++
 Misc/NEWS                      |  4 ++++
 5 files changed, 42 insertions(+)

Index: Python-3.5.1/Doc/howto/urllib2.rst
===================================================================
--- Python-3.5.1.orig/Doc/howto/urllib2.rst
+++ Python-3.5.1/Doc/howto/urllib2.rst
@@ -538,6 +538,11 @@ setting up a `Basic Authentication`_ han
     through a proxy.  However, this can be enabled by extending urllib.request as
     shown in the recipe [#]_.
 
+.. note::
+
+   `HTTP_PROXY`` will be ignored if a variable ``REQUEST_METHOD`` is set; see
+   the documentation on :func:`~urllib.request.getproxies`.
+
 
 Sockets and Layers
 ==================
Index: Python-3.5.1/Doc/library/urllib.request.rst
===================================================================
--- Python-3.5.1.orig/Doc/library/urllib.request.rst
+++ Python-3.5.1/Doc/library/urllib.request.rst
@@ -166,6 +166,14 @@ The :mod:`urllib.request` module defines
    cannot find it, looks for proxy information from Mac OSX System
    Configuration for Mac OS X and Windows Systems Registry for Windows.
 
+   .. note::
+
+      If the environment variable ``REQUEST_METHOD`` is set, which usually
+      indicates your script is running in a CGI environment, the environment
+      variable ``HTTP_PROXY`` (uppercase ``_PROXY``) will be ignored. This is
+      because that variable can be injected by a client using the "Proxy:" HTTP
+      header. If you need to use an HTTP proxy in a CGI environment use
+      ``ProxyHandler`` explicitly.
 
 The following classes are provided:
 
@@ -275,6 +283,11 @@ The following classes are provided:
 
    To disable autodetected proxy pass an empty dictionary.
 
+   .. note::
+
+      ``HTTP_PROXY`` will be ignored if a variable ``REQUEST_METHOD`` is set;
+      see the documentation on :func:`~urllib.request.getproxies`.
+
 
 .. class:: HTTPPasswordMgr()
 
Index: Python-3.5.1/Lib/urllib/request.py
===================================================================
--- Python-3.5.1.orig/Lib/urllib/request.py
+++ Python-3.5.1/Lib/urllib/request.py
@@ -2394,6 +2394,13 @@ def getproxies_environment():
         name = name.lower()
         if value and name[-6:] == '_proxy':
             proxies[name[:-6]] = value
+
+    # CVE-2016-1000110 - If we are running as CGI script, forget HTTP_PROXY
+    # (non-all-lowercase) as it may be set from the web server by a "Proxy:"
+    # header from the client
+    if 'REQUEST_METHOD' in os.environ:
+        proxies.pop('http', None)
+
     return proxies
 
 def proxy_bypass_environment(host):
Index: Python-3.5.1/Misc/NEWS
===================================================================
--- Python-3.5.1.orig/Misc/NEWS
+++ Python-3.5.1/Misc/NEWS
@@ -1266,6 +1266,10 @@ Library
   lines from the code object, fixing an issue when a lambda function is used as
   decorator argument. Patch by Thomas Ballinger and Allison Kaptur.
 
+- Issue #27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
+  HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates
+  that the script is in CGI mode.
+
 - Issue #24521: Fix possible integer overflows in the pickle module.
 
 - Issue #22931: Allow '[' and ']' in cookie values.
Index: Python-3.5.1/Lib/test/test_urllib.py
===================================================================
--- Python-3.5.1.orig/Lib/test/test_urllib.py
+++ Python-3.5.1/Lib/test/test_urllib.py
@@ -224,6 +224,18 @@ class ProxyTests(unittest.TestCase):
         # List of no_proxies with space.
         self.env.set('NO_PROXY', 'localhost, anotherdomain.com, newdomain.com')
         self.assertTrue(urllib.request.proxy_bypass_environment('anotherdomain.com'))
+    def test_proxy_cgi_ignore(self):
+        try:
+            self.env.set('HTTP_PROXY', 'http://somewhere:3128')
+            proxies = urllib.request.getproxies_environment()
+            self.assertEqual('http://somewhere:3128', proxies['http'])
+            self.env.set('REQUEST_METHOD', 'GET')
+            proxies = urllib.request.getproxies_environment()
+            self.assertNotIn('http', proxies)
+        finally:
+            self.env.unset('REQUEST_METHOD')
+            self.env.unset('HTTP_PROXY')
+
 
 class urlopen_HttpTests(unittest.TestCase, FakeHTTPMixin, FakeFTPMixin):
     """Test urlopen() opening a fake http connection."""