[Python-checkins] cpython (2.7): Prevent HTTPoxy attack (CVE-2016-1000110)

Sat Jul 30 08:49:59 EDT 2016

https://hg.python.org/cpython/rev/ba915d561667
changeset: 102496:ba915d561667
branch: 2.7
parent: 102472:c8c1ea94379a
user: Senthil Kumaran <senthil at uthcode.com>
date: Sat Jul 30 05:49:53 2016 -0700
summary:
 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.
files:
 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(+), 0 deletions(-)

diff --git a/Doc/howto/urllib2.rst b/Doc/howto/urllib2.rst
--- a/Doc/howto/urllib2.rst
+++ b/Doc/howto/urllib2.rst
@@ -525,6 +525,11 @@
 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
 ==================
diff --git a/Doc/library/urllib.rst b/Doc/library/urllib.rst
--- a/Doc/library/urllib.rst
+++ b/Doc/library/urllib.rst
@@ -295,6 +295,16 @@
 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
diff --git a/Doc/library/urllib2.rst b/Doc/library/urllib2.rst
--- a/Doc/library/urllib2.rst
+++ b/Doc/library/urllib2.rst
@@ -229,6 +229,11 @@
 
 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()
 
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -170,6 +170,18 @@
 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',
diff --git a/Lib/urllib.py b/Lib/urllib.py
--- a/Lib/urllib.py
+++ b/Lib/urllib.py
@@ -1380,12 +1380,21 @@
 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()
diff --git a/Misc/ACKS b/Misc/ACKS
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1123,6 +1123,7 @@
 Jeff Ramnani
 Varpu Rantala
 Brodie Rao
+Rémi Rampin
 Senko Rasic
 Antti Rasinen
 Nikolaus Rath
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -29,6 +29,10 @@
 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
-- 
Repository URL: https://hg.python.org/cpython
