python3/00183-cve-2013-2099-fix-ssl-match_hostname-dos.patch
2013-05-20 08:04:03 +02:00

50 lines
2.1 KiB
Diff

# HG changeset patch
# User Antoine Pitrou <solipsis@pitrou.net>
# Date 1368892602 -7200
# Node ID c627638753e2d25a98950585b259104a025937a9
# Parent 9682241dc8fcb4b1aef083bd30860efa070c3d6d
Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of service using certificates with many wildcards (CVE-2013-2099).
diff --git a/Lib/ssl.py b/Lib/ssl.py
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -129,9 +129,16 @@ class CertificateError(ValueError):
pass
-def _dnsname_to_pat(dn):
+def _dnsname_to_pat(dn, max_wildcards=1):
pats = []
for frag in dn.split(r'.'):
+ if frag.count('*') > max_wildcards:
+ # Issue #17980: avoid denials of service by refusing more
+ # than one wildcard per fragment. A survery of established
+ # policy among SSL implementations showed it to be a
+ # reasonable choice.
+ raise CertificateError(
+ "too many wildcards in certificate DNS name: " + repr(dn))
if frag == '*':
# When '*' is a fragment by itself, it matches a non-empty dotless
# fragment.
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -349,6 +349,17 @@ class BasicSocketTests(unittest.TestCase
self.assertRaises(ValueError, ssl.match_hostname, None, 'example.com')
self.assertRaises(ValueError, ssl.match_hostname, {}, 'example.com')
+ # Issue #17980: avoid denials of service by refusing more than one
+ # wildcard per fragment.
+ cert = {'subject': ((('commonName', 'a*b.com'),),)}
+ ok(cert, 'axxb.com')
+ cert = {'subject': ((('commonName', 'a*b.co*'),),)}
+ ok(cert, 'axxb.com')
+ cert = {'subject': ((('commonName', 'a*b*.com'),),)}
+ with self.assertRaises(ssl.CertificateError) as cm:
+ ssl.match_hostname(cert, 'axxbxxc.com')
+ self.assertIn("too many wildcards", str(cm.exception))
+
def test_server_side(self):
# server_hostname doesn't work for server sockets
ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)