Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of service using certificates with many wildcards (CVE-2013-2099).
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@ -129,9 +129,16 @@ class CertificateError(ValueError):
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pass
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def _dnsname_to_pat(dn):
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def _dnsname_to_pat(dn, max_wildcards=1):
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pats = []
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for frag in dn.split(r'.'):
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if frag.count('*') > max_wildcards:
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# Issue #17980: avoid denials of service by refusing more
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# than one wildcard per fragment. A survery of established
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# policy among SSL implementations showed it to be a
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# reasonable choice.
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raise CertificateError(
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"too many wildcards in certificate DNS name: " + repr(dn))
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if frag == '*':
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# When '*' is a fragment by itself, it matches a non-empty dotless
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# fragment.
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@ -349,6 +349,17 @@ class BasicSocketTests(unittest.TestCase):
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self.assertRaises(ValueError, ssl.match_hostname, None, 'example.com')
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self.assertRaises(ValueError, ssl.match_hostname, {}, 'example.com')
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# Issue #17980: avoid denials of service by refusing more than one
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# wildcard per fragment.
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cert = {'subject': ((('commonName', 'a*b.com'),),)}
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ok(cert, 'axxb.com')
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cert = {'subject': ((('commonName', 'a*b.co*'),),)}
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ok(cert, 'axxb.com')
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cert = {'subject': ((('commonName', 'a*b*.com'),),)}
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with self.assertRaises(ssl.CertificateError) as cm:
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ssl.match_hostname(cert, 'axxbxxc.com')
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self.assertIn("too many wildcards", str(cm.exception))
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def test_server_side(self):
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# server_hostname doesn't work for server sockets
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ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
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@ -24,6 +24,9 @@ Core and Builtins
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Library
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-------
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- Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of
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service using certificates with many wildcards (CVE-2013-2099).
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- Issue #17981: Closed socket on error in SysLogHandler.
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- Fix typos in the multiprocessing module.
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