From: Yeting Li <liyt@ios.ac.cn>
Date: Wed, 7 Apr 2021 11:27:41 +0000 (+0800)
Subject: bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391)
X-Git-Tag: v3.10.0b1~378
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7215d1ae25525c92b026166f9d5cac85fb1defe1;p=thirdparty%2FPython%2Fcpython.git

bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391)

Fix Regular Expression Denial of Service (ReDoS) vulnerability in
urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex
has quadratic worst-case complexity and it allows cause a denial of
service when identifying crafted invalid RFCs. This ReDoS issue is on
the client side and needs remote attackers to control the HTTP server.
---

diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index e5febe61f556..8363905f20fa 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -945,7 +945,7 @@ class AbstractBasicAuthHandler:
     # (single quotes are a violation of the RFC, but appear in the wild)
     rx = re.compile('(?:^|,)'   # start of the string or ','
                     '[ \t]*'    # optional whitespaces
-                    '([^ \t]+)' # scheme like "Basic"
+                    '([^ \t,]+)' # scheme like "Basic"
                     '[ \t]+'    # mandatory whitespaces
                     # realm=xxx
                     # realm='xxx'
diff --git a/Misc/NEWS.d/next/Security/2021-01-31-05-28-14.bpo-43075.DoAXqO.rst b/Misc/NEWS.d/next/Security/2021-01-31-05-28-14.bpo-43075.DoAXqO.rst
new file mode 100644
index 000000000000..1c9f727e965f
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2021-01-31-05-28-14.bpo-43075.DoAXqO.rst
@@ -0,0 +1 @@
+Fix Regular Expression Denial of Service (ReDoS) vulnerability in :class:`urllib.request.AbstractBasicAuthHandler`.  The ReDoS-vulnerable regex has quadratic worst-case complexity and it allows cause a denial of service when identifying crafted invalid RFCs. This ReDoS issue is on the client side and needs remote attackers to control the HTTP server.