From 5be8d3e97b1d2e526548cb346fd5f8980d31616a Mon Sep 17 00:00:00 2001
From: Senthil Kumaran <senthil@uthcode.com>
Date: Sat, 30 Jul 2016 05:49:53 -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 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.rst  | 10 ++++++++++
 Doc/library/urllib2.rst |  5 +++++
 Lib/test/test_urllib.py | 12 ++++++++++++
 Lib/urllib.py           |  9 +++++++++
 Misc/ACKS               |  1 +
 Misc/NEWS               |  4 ++++
 7 files changed, 46 insertions(+)

Index: Python-2.7.11/Doc/howto/urllib2.rst
===================================================================
--- Python-2.7.11.orig/Doc/howto/urllib2.rst
+++ Python-2.7.11/Doc/howto/urllib2.rst
@@ -523,6 +523,11 @@ setting up a `Basic Authentication`_ han
     through a proxy.  However, this can be enabled by extending urllib2 as
     shown in the recipe [#]_.
 
+.. note::
+
+    ``HTTP_PROXY`` will be ignored if a variable ``REQUEST_METHOD`` is set; see
+    the documentation on :func:`~urllib.getproxies`.
+
 
 Sockets and Layers
 ==================
Index: Python-2.7.11/Doc/library/urllib.rst
===================================================================
--- Python-2.7.11.orig/Doc/library/urllib.rst
+++ Python-2.7.11/Doc/library/urllib.rst
@@ -293,6 +293,16 @@ Utility functions
    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,
+        either use ``ProxyHandler`` explicitly, or make sure the variable name
+        is in lowercase (or at least the ``_proxy`` suffix).
+
 .. note::
     urllib also exposes certain utility functions like splittype, splithost and
     others parsing url into various components. But it is recommended to use
Index: Python-2.7.11/Doc/library/urllib2.rst
===================================================================
--- Python-2.7.11.orig/Doc/library/urllib2.rst
+++ Python-2.7.11/Doc/library/urllib2.rst
@@ -229,6 +229,11 @@ 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.getproxies`.
+
 
 .. class:: HTTPPasswordMgr()
 
Index: Python-2.7.11/Misc/ACKS
===================================================================
--- Python-2.7.11.orig/Misc/ACKS
+++ Python-2.7.11/Misc/ACKS
@@ -1110,6 +1110,7 @@ Jérôme Radix
 Burton Radons
 Jeff Ramnani
 Brodie Rao
+Rémi Rampin
 Senko Rasic
 Antti Rasinen
 Nikolaus Rath
Index: Python-2.7.11/Lib/test/test_urllib.py
===================================================================
--- Python-2.7.11.orig/Lib/test/test_urllib.py
+++ Python-2.7.11/Lib/test/test_urllib.py
@@ -162,6 +162,18 @@ class ProxyTests(unittest.TestCase):
         self.assertTrue(urllib.proxy_bypass_environment('anotherdomain.com'))
 
 
+    def test_proxy_cgi_ignore(self):
+        try:
+            self.env.set('HTTP_PROXY', 'http://somewhere:3128')
+            proxies = urllib.getproxies_environment()
+            self.assertEqual('http://somewhere:3128', proxies['http'])
+            self.env.set('REQUEST_METHOD', 'GET')
+            proxies = urllib.getproxies_environment()
+            self.assertNotIn('http', proxies)
+        finally:
+            self.env.unset('REQUEST_METHOD')
+            self.env.unset('HTTP_PROXY')
+
 class urlopen_HttpTests(unittest.TestCase, FakeHTTPMixin):
     """Test urlopen() opening a fake http connection."""
 
Index: Python-2.7.11/Lib/urllib.py
===================================================================
--- Python-2.7.11.orig/Lib/urllib.py
+++ Python-2.7.11/Lib/urllib.py
@@ -1382,11 +1382,21 @@ def getproxies_environment():
     [Fancy]URLopener constructor.
 
     """
+    # Get all variables
     proxies = {}
     for name, value in os.environ.items():
         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 "proxy" is lowercase, it will still be used thanks to the next block
+    if 'REQUEST_METHOD' in os.environ:
+        proxies.pop('http', None)
+
+    # Get lowercase variables
     return proxies
 
 def proxy_bypass_environment(host):
Index: Python-2.7.11/Misc/NEWS
===================================================================
--- Python-2.7.11.orig/Misc/NEWS
+++ Python-2.7.11/Misc/NEWS
@@ -10,6 +10,10 @@ What's New in Python 2.7.11?
 Library
 -------
 
+- 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 #25624: ZipFile now always writes a ZIP_STORED header for directory
   entries.  Patch by Dingyuan Wang.