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"""The match_hostname() function from Python 3.2, essential when using SSL."""
# XXX put it here until it's packaged
import re
__version__ = '3.2a3'
class CertificateError(ValueError):
pass
def _dnsname_to_pat(dn):
pats = []
for frag in dn.split(r'.'):
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)
def match_hostname(cert, hostname):
"""Verify that *cert* (in decoded format as returned by
SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 rules
are mostly followed, but IP addresses are not accepted for *hostname*.
CertificateError is raised on failure. On success, the function
returns nothing.
"""
if not cert:
raise ValueError("empty or no certificate")
dnsnames = []
san = cert.get('subjectAltName', ())
for key, value in san:
if key == 'DNS':
if _dnsname_to_pat(value).match(hostname):
return
dnsnames.append(value)
if not san:
# The subject is only checked when subjectAltName is empty
for sub in cert.get('subject', ()):
for key, value in sub:
# XXX according to RFC 2818, the most specific Common Name
# must be used.
if key == 'commonName':
if _dnsname_to_pat(value).match(hostname):
return
dnsnames.append(value)
if len(dnsnames) > 1:
raise CertificateError(
"hostname %r doesn't match either of %s"
% (hostname, ', '.join(map(repr, dnsnames))))
elif len(dnsnames) == 1:
raise CertificateError(
"hostname %r doesn't match %r"
% (hostname, dnsnames[0]))
else:
raise CertificateError(
"no appropriate commonName or "
"subjectAltName fields were found")
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