def match_hostname(cert, hostname):
    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")
Verify that *cert* (in decoded format as returned by
dataset/ETHPy150Open blynch/CloudMemeBackend/pymongo/ssl_match_hostname.py/match_hostname