--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -283,10 +283,10 @@ Certificate handling
Verify that *cert* (in decoded format as returned by
:meth:`SSLSocket.getpeercert`) matches the given *hostname*. The rules
applied are those for checking the identity of HTTPS servers as outlined
- in :rfc:`2818`, except that IP addresses are not currently supported.
- In addition to HTTPS, this function should be suitable for checking the
- identity of servers in various SSL-based protocols such as FTPS, IMAPS,
- POPS and others.
+ in :rfc:`2818` and :rfc:`6125`, except that IP addresses are not currently
+ supported. In addition to HTTPS, this function should be suitable for
+ checking the identity of servers in various SSL-based protocols such as
+ FTPS, IMAPS, POPS and others.
:exc:`CertificateError` is raised on failure. On success, the function
returns nothing::
@@ -301,6 +301,13 @@ Certificate handling
.. versionadded:: 3.2
+ .. versionchanged:: 3.3.3
+ The function now follows :rfc:`6125`, section 6.4.3 and does neither
+ match multiple wildcards (e.g. ``*.*.com`` or ``*a*.example.org``) nor
+ a wildcard inside an internationalized domain names (IDN) fragment.
+ IDN A-labels such as ``www*.xn--pthon-kva.org`` are still supported,
+ but ``x*.python.org`` no longer matches ``xn--tda.python.org``.
+
.. function:: cert_time_to_seconds(timestring)
Returns a floating-point value containing a normal seconds-after-the-epoch
unchanged:
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -129,25 +129,53 @@ class CertificateError(ValueError):
pass
-def _dnsname_to_pat(dn, max_wildcards=1):
+def _dnsname_match(dn, hostname, max_wildcards=1):
+ """Matching according to RFC 6125, section 6.4.3
+
+ http://tools.ietf.org/html/rfc6125#section-6.4.3
+ """
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.
- pats.append('[^.]+')
- else:
- # Otherwise, '*' matches any dotless fragment.
- frag = re.escape(frag)
- pats.append(frag.replace(r'\*', '[^.]*'))
- return re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
+ if not dn:
+ return False
+
+ leftmost, *remainder = dn.split(r'.')
+
+ wildcards = leftmost.count('*')
+ if wildcards > 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))
+
+ # speed up common case w/o wildcards
+ if not wildcards:
+ return dn.lower() == hostname.lower()
+
+ # RFC 6125, section 6.4.3, subitem 1.
+ # The client SHOULD NOT attempt to match a presented identifier in which
+ # the wildcard character comprises a label other than the left-most label.
+ if leftmost == '*':
+ # When '*' is a fragment by itself, it matches a non-empty dotless
+ # fragment.
+ pats.append('[^.]+')
+ elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
+ # RFC 6125, section 6.4.3, subitem 3.
+ # The client SHOULD NOT attempt to match a presented identifier
+ # where the wildcard character is embedded within an A-label or
+ # U-label of an internationalized domain name.
+ pats.append(re.escape(leftmost))
+ else:
+ # Otherwise, '*' matches any dotless string, e.g. www*
+ pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
+
+ # add the remaining fragments, ignore any wildcards
+ for frag in remainder:
+ pats.append(re.escape(frag))
+
+ pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
+ return pat.match(hostname)
def match_hostname(cert, hostname):
unchanged:
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -304,11 +304,7 @@ class BasicSocketTests(unittest.TestCase
fail(cert, 'Xa.com')
fail(cert, '.a.com')
- cert = {'subject': ((('commonName', 'a.*.com'),),)}
- ok(cert, 'a.foo.com')
- fail(cert, 'a..com')
- fail(cert, 'a.com')
-
+ # only match one left-most wildcard
cert = {'subject': ((('commonName', 'f*.com'),),)}
ok(cert, 'foo.com')
ok(cert, 'f.com')
@@ -323,6 +319,36 @@ class BasicSocketTests(unittest.TestCase
fail(cert, 'example.org')
fail(cert, 'null.python.org')
+ # error cases with wildcards
+ cert = {'subject': ((('commonName', '*.*.a.com'),),)}
+ fail(cert, 'bar.foo.a.com')
+ fail(cert, 'a.com')
+ fail(cert, 'Xa.com')
+ fail(cert, '.a.com')
+
+ cert = {'subject': ((('commonName', 'a.*.com'),),)}
+ fail(cert, 'a.foo.com')
+ fail(cert, 'a..com')
+ fail(cert, 'a.com')
+
+ # wildcard doesn't match IDNA prefix 'xn--'
+ idna = 'püthon.python.org'.encode("idna").decode("ascii")
+ cert = {'subject': ((('commonName', idna),),)}
+ ok(cert, idna)
+ cert = {'subject': ((('commonName', 'x*.python.org'),),)}
+ fail(cert, idna)
+ cert = {'subject': ((('commonName', 'xn--p*.python.org'),),)}
+ fail(cert, idna)
+
+ # wildcard in first fragment and IDNA A-labels in sequent fragments
+ # are supported.
+ idna = 'www*.pythön.org'.encode("idna").decode("ascii")
+ cert = {'subject': ((('commonName', idna),),)}
+ ok(cert, 'www.pythön.org'.encode("idna").decode("ascii"))
+ ok(cert, 'www1.pythön.org'.encode("idna").decode("ascii"))
+ fail(cert, 'ftp.pythön.org'.encode("idna").decode("ascii"))
+ fail(cert, 'pythön.org'.encode("idna").decode("ascii"))
+
# Slightly fake real-world example
cert = {'notAfter': 'Jun 26 21:41:46 2011 GMT',
'subject': ((('commonName', 'linuxfrz.org'),),),
@@ -383,7 +409,7 @@ class BasicSocketTests(unittest.TestCase
cert = {'subject': ((('commonName', 'a*b.com'),),)}
ok(cert, 'axxb.com')
cert = {'subject': ((('commonName', 'a*b.co*'),),)}
- ok(cert, 'axxb.com')
+ fail(cert, 'axxb.com')
cert = {'subject': ((('commonName', 'a*b*.com'),),)}
with self.assertRaises(ssl.CertificateError) as cm:
ssl.match_hostname(cert, 'axxbxxc.com')
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -192,7 +192,7 @@ def match_hostname(cert, hostname):
san = cert.get('subjectAltName', ())
for key, value in san:
if key == 'DNS':
- if _dnsname_to_pat(value).match(hostname):
+ if _dnsname_match(value, hostname):
return
dnsnames.append(value)
if not dnsnames:
@@ -203,7 +203,7 @@ def match_hostname(cert, hostname):
# XXX according to RFC 2818, the most specific Common Name
# must be used.
if key == 'commonName':
- if _dnsname_to_pat(value).match(hostname):
+ if _dnsname_match(value, hostname):
return
dnsnames.append(value)
if len(dnsnames) > 1: