Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of service using certificates with many wildcards (CVE-2013-2099).

This commit is contained in:
Antoine Pitrou 2013-05-18 17:56:42 +02:00
parent ef9683b73f
commit 636f93c63b
3 changed files with 22 additions and 1 deletions

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@ -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.

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@ -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)

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@ -24,6 +24,9 @@ Core and Builtins
Library
-------
- Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of
service using certificates with many wildcards (CVE-2013-2099).
- Issue #17981: Closed socket on error in SysLogHandler.
- Fix typos in the multiprocessing module.