Use backports.ssl_match_hostname

The py2-ipaddress module unfortunately conflicts with the pypi:ipaddress module, which is in the dependency tree of widely used pyOpenSSL. I think it would be a good idea to use a well maintained backport of the Python 3.5 implementation of match_hostname() instead of duplicating the effort and maintain another.

All tests are passing here.
Signed-off-by: Felix Yan <felixonmars@archlinux.org>

docker/ssladapter/ssl_match_hostname.py

-# Slightly modified version of match_hostname in python's ssl library
-# https://hg.python.org/cpython/file/tip/Lib/ssl.py
-# Changed to make code python 2.x compatible (unicode strings for ip_address
-# and 3.5-specific var assignment syntax)
-
-import ipaddress
-import re
-
-try:
-    from ssl import CertificateError
-except ImportError:
-    CertificateError = ValueError
-
-import six
-
-
-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
-    ip = ipaddress.ip_address(six.text_type(ipname.rstrip()))
-    return ip == host_ip
-
-
-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
-
-    split_dn = dn.split(r'.')
-    leftmost, remainder = split_dn[0], split_dn[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 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:
-        host_ip = ipaddress.ip_address(six.text_type(hostname))
-    except ValueError:
-        # Not an IP address (common case)
-        host_ip = None
-    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"
-        )

docker/ssladapter/ssladapter.py

@@ -18,7 +18,7 @@ PoolManager = urllib3.poolmanager.PoolManager
 # Monkey-patching match_hostname with a version that supports
 # IP-address checking. Not necessary for Python 3.5 and above
 if sys.version_info[0] < 3 or sys.version_info[1] < 5:
-    from .ssl_match_hostname import match_hostname
+    from backports.ssl_match_hostname import match_hostname
     urllib3.connection.match_hostname = match_hostname
 
 

requirements.txt

 requests==2.5.3
 six>=1.4.0
 websocket-client==0.32.0
-py2-ipaddress==3.4.1 ; python_version < '3.2'
+backports.ssl_match_hostname>=3.5 ; python_version < '3.5'
\ No newline at end of file

setup.py

@@ -13,7 +13,7 @@ requirements = [
 ]
 
 extras_require = {
-    ':python_version < "3"': 'py2-ipaddress >= 3.4.1',
+    ':python_version < "3.5"': 'backports.ssl_match_hostname >= 3.5',
 }
 
 exec(open('docker/version.py').read())

tests/unit/ssladapter_test.py

 from docker.ssladapter import ssladapter
-from docker.ssladapter.ssl_match_hostname import (
-    match_hostname, CertificateError
-)
+
+try:
+    from backports.ssl_match_hostname import (
+        match_hostname, CertificateError
+    )
+except ImportError:
+    from ssl import (
+        match_hostname, CertificateError
+    )
 
 try:
     from ssl import OP_NO_SSLv3, OP_NO_SSLv2, OP_NO_TLSv1