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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 reported and patch contributed by Rémi Rampin.
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orsenthil committed Jul 30, 2016
1 parent a850ef6 commit 75d7b615ba70fc5759d16dee95bbd8f0474d8a9c
Showing with 46 additions and 0 deletions.
  1. +5 −0 Doc/howto/urllib2.rst
  2. +10 −0 Doc/library/urllib.rst
  3. +5 −0 Doc/library/urllib2.rst
  4. +12 −0 Lib/test/test_urllib.py
  5. +9 −0 Lib/urllib.py
  6. +1 −0 Misc/ACKS
  7. +4 −0 Misc/NEWS
@@ -525,6 +525,11 @@ setting up a `Basic Authentication`_ handler: ::
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
==================
@@ -295,6 +295,16 @@ Utility functions
If both lowercase and uppercase environment variables exist (and disagree),
lowercase is preferred.

.. 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
@@ -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()

@@ -170,6 +170,18 @@ def test_getproxies_environment_keep_no_proxies(self):
self.assertTrue(urllib.proxy_bypass_environment('anotherdomain.com:8888'))
self.assertTrue(urllib.proxy_bypass_environment('newdomain.com:1234'))

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')

def test_proxy_bypass_environment_host_match(self):
bypass = urllib.proxy_bypass_environment
self.env.set('NO_PROXY',
@@ -1380,12 +1380,21 @@ def getproxies_environment():
If you need a different way, you can pass a proxies dictionary to the
[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
for name, value in os.environ.items():
if name[-6:] == '_proxy':
name = name.lower()
@@ -1123,6 +1123,7 @@ Burton Radons
Jeff Ramnani
Varpu Rantala
Brodie Rao
Rémi Rampin
Senko Rasic
Antti Rasinen
Nikolaus Rath
@@ -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 #27130: In the "zlib" module, fix handling of large buffers
(typically 2 or 4 GiB). Previously, inputs were limited to 2 GiB, and
compression and decompression operations did not properly handle results of

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