name : ssl_match_hostname.py """The match_hostname() function from Python 3.3.3, essential when using SSL.""" # Note: This file is under the PSF license as the code comes from the python # stdlib. http://docs.python.org/3/license.html import re import sys # ipaddress has been backported to 2.6+ in pypi. If it is installed on the # system, use it to handle IPAddress ServerAltnames (this was added in # python-3.5) otherwise only do DNS matching. This allows # util.ssl_match_hostname to continue to be used in Python 2.7. try: import ipaddress except ImportError: ipaddress = None __version__ = "3.5.0.1" class CertificateError(ValueError): pass 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 = [] if not dn: return False # Ported from python3-syntax: # leftmost, *remainder = dn.split(r'.') parts = dn.split(r".") leftmost = parts[0] remainder = parts[1:] wildcards = leftmost.count("*") if wildcards > max_wildcards: # Issue #17980: avoid denials of service by refusing more # than one wildcard per fragment. A survey 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 _to_unicode(obj): if isinstance(obj, str) and sys.version_info < (3,): # ignored flake8 # F821 to support python 2.7 function obj = unicode(obj, encoding="ascii", errors="strict") # noqa: F821 return obj def _ipaddress_match(ipname, host_ip): """Exact matching of IP addresses. RFC 6125 explicitly doesn't define an algorithm for this (section 1.7.2 - "Out of Scope"). """ # OpenSSL may add a trailing newline to a subjectAltName's IP address # Divergence from upstream: ipaddress can't handle byte str ip = ipaddress.ip_address(_to_unicode(ipname).rstrip()) return ip == host_ip def match_hostname(cert, hostname): """Verify that *cert* (in decoded format as returned by SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125 rules are 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, match_hostname needs a " "SSL socket or SSL context with either " "CERT_OPTIONAL or CERT_REQUIRED" ) try: # Divergence from upstream: ipaddress can't handle byte str host_ip = ipaddress.ip_address(_to_unicode(hostname)) except (UnicodeError, ValueError): # ValueError: Not an IP address (common case) # UnicodeError: Divergence from upstream: Have to deal with ipaddress not taking # byte strings. addresses should be all ascii, so we consider it not # an ipaddress in this case host_ip = None except AttributeError: # Divergence from upstream: Make ipaddress library optional if ipaddress is None: host_ip = None else: # Defensive raise dnsnames = [] san = cert.get("subjectAltName", ()) for key, value in san: if key == "DNS": if host_ip is None and _dnsname_match(value, hostname): return dnsnames.append(value) elif key == "IP Address": if host_ip is not None and _ipaddress_match(value, host_ip): return dnsnames.append(value) if not dnsnames: # The subject is only checked when there is no dNSName entry # in subjectAltName 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_match(value, 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" )