[Python-checkins] cpython (3.3): Prevent HTTPoxy attack (CVE-2016-1000110)

Sun Jul 31 02:51:49 EDT 2016

https://hg.python.org/cpython/rev/95b09ccc8a3e
changeset: 102501:95b09ccc8a3e
branch: 3.3
parent: 102340:1c06e02b968a
user: Senthil Kumaran <senthil at uthcode.com>
date: Sat Jul 30 23:24:16 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 #27568 Reported and patch contributed by Rémi Rampin.
files:
 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(+), 0 deletions(-)

diff --git a/Doc/howto/urllib2.rst b/Doc/howto/urllib2.rst
--- a/Doc/howto/urllib2.rst
+++ b/Doc/howto/urllib2.rst
@@ -538,6 +538,11 @@
 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
 ==================
diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
--- a/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@ -161,6 +161,14 @@
 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 @@
 
 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()
 
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
@@ -194,6 +194,19 @@
 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."""
 
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -2366,6 +2366,13 @@
 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):
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 #24521: Fix possible integer overflows in the pickle module.
 
 - Issue #22931: Allow '[' and ']' in cookie values.
-- 
Repository URL: https://hg.python.org/cpython
