[merge from 3.4] - 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.

1 files changed, 6 insertions, 0 deletions

diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 1731fe3..3be327d 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -2412,6 +2412,12 @@ 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 "proxy" is lowercase, it will still be used thanks to the next block
+    if 'REQUEST_METHOD' in os.environ:
+        proxies.pop('http', None)
     for name, value in os.environ.items():
         if name[-6:] == '_proxy':
             name = name.lower()