From dbcfc664ee7ae6e9e97ca0d69ad6581a36871836 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 30 Jan 2020 16:13:03 +0100
Subject: [PATCH] bpo-39503: Fix urllib basic auth regex

The AbstractBasicAuthHandler class of the urllib.request module uses
an inefficient regular expression which can be exploited by an
attacker to cause a denial of service. Fix the regex to prevent the
catastrophic backtracking.

Vulnerability reported by Matt Schwager.

Signed-off-by: hanxinke <hanxinke@huawei.com>
---
 Lib/urllib2.py                                                | 2 +-
 .../next/Security/2020-01-30-16-15-29.bpo-39503.B299Yq.rst    | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Security/2020-01-30-16-15-29.bpo-39503.B299Yq.rst

diff --git a/Lib/urllib2.py b/Lib/urllib2.py
index fd19e1a..1596a51 100644
--- a/Lib/urllib2.py
+++ b/Lib/urllib2.py
@@ -858,7 +858,7 @@ class AbstractBasicAuthHandler:
 
     # allow for double- and single-quoted realm values
     # (single quotes are a violation of the RFC, but appear in the wild)
-    rx = re.compile('(?:.*,)*[ \t]*([^ \t]+)[ \t]+'
+    rx = re.compile('(?:[^,]*,)*[ \t]*([^ \t]+)[ \t]+'
                     'realm=(["\']?)([^"\']*)\\2', re.I)
 
     # XXX could pre-emptively send auth info already accepted (RFC 2617,
diff --git a/Misc/NEWS.d/next/Security/2020-01-30-16-15-29.bpo-39503.B299Yq.rst b/Misc/NEWS.d/next/Security/2020-01-30-16-15-29.bpo-39503.B299Yq.rst
new file mode 100644
index 0000000..92f186d
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2020-01-30-16-15-29.bpo-39503.B299Yq.rst
@@ -0,0 +1,4 @@
+CVE-2020-8492: The :class:`~urllib.request.AbstractBasicAuthHandler` class of the
+:mod:`urllib.request` module uses an inefficient regular expression which can
+be exploited by an attacker to cause a denial of service. Fix the regex to
+prevent the catastrophic backtracking. Vulnerability reported by Matt Schwager.
-- 
2.23.0

