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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 #27568 Reported and patch contributed by Rémi Rampin.
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orsenthil committed Jul 31, 2016
1 parent d27a7c1 commit 4cbb23f8f278fd1f71dcd5968aa0b3f0b4f3bd5d
Showing with 42 additions and 0 deletions.
  1. +5 −0 Doc/howto/urllib2.rst
  2. +13 −0 Doc/library/urllib.request.rst
  3. +13 −0 Lib/test/test_urllib.py
  4. +7 −0 Lib/urllib/request.py
  5. +4 −0 Misc/NEWS
@@ -538,6 +538,11 @@ setting up a `Basic Authentication`_ handler: ::
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
==================
@@ -161,6 +161,14 @@ The :mod:`urllib.request` module defines the following functions:
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:

@@ -265,6 +273,11 @@ 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()

@@ -194,6 +194,19 @@ def test_getproxies_environment_keep_no_proxies(self):
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):
"""Test urlopen() opening a fake http connection."""

@@ -2366,6 +2366,13 @@ 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):
@@ -29,6 +29,10 @@ Core and Builtins
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 #24521: Fix possible integer overflows in the pickle module.

- Issue #22931: Allow '[' and ']' in cookie values.

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