shell bypass 403
"""ndg_httpsclient - module containing SSL peer verification class.
"""
__author__ = "P J Kershaw (STFC)"
__date__ = "09/12/11"
__copyright__ = "(C) 2012 Science and Technology Facilities Council"
__license__ = "BSD - see LICENSE file in top-level directory"
__contact__ = "Philip.Kershaw@stfc.ac.uk"
__revision__ = '$Id$'
import re
import logging
log = logging.getLogger(__name__)
try:
from ndg.httpsclient.subj_alt_name import SubjectAltName
from pyasn1.codec.der import decoder as der_decoder
SUBJ_ALT_NAME_SUPPORT = True
except ImportError, e:
SUBJ_ALT_NAME_SUPPORT = False
SUBJ_ALT_NAME_SUPPORT_MSG = (
'SubjectAltName support is disabled - check pyasn1 package '
'installation to enable'
)
import warnings
warnings.warn(SUBJ_ALT_NAME_SUPPORT_MSG)
class ServerSSLCertVerification(object):
"""Check server identity. If hostname doesn't match, allow match of
host's Distinguished Name against server DN setting"""
DN_LUT = {
'commonName': 'CN',
'organisationalUnitName': 'OU',
'organisation': 'O',
'countryName': 'C',
'emailAddress': 'EMAILADDRESS',
'localityName': 'L',
'stateOrProvinceName': 'ST',
'streetAddress': 'STREET',
'domainComponent': 'DC',
'userid': 'UID'
}
SUBJ_ALT_NAME_EXT_NAME = 'subjectAltName'
PARSER_RE_STR = '/(%s)=' % '|'.join(DN_LUT.keys() + DN_LUT.values())
PARSER_RE = re.compile(PARSER_RE_STR)
__slots__ = ('__hostname', '__certDN', '__subj_alt_name_match')
def __init__(self, certDN=None, hostname=None, subj_alt_name_match=True):
"""Override parent class __init__ to enable setting of certDN
setting
@type certDN: string
@param certDN: Set the expected Distinguished Name of the
server to avoid errors matching hostnames. This is useful
where the hostname is not fully qualified
@type hostname: string
@param hostname: hostname to match against peer certificate
subjectAltNames or subject common name
@type subj_alt_name_match: bool
@param subj_alt_name_match: flag to enable/disable matching of hostname
against peer certificate subjectAltNames. Nb. A setting of True will
be ignored if the pyasn1 package is not installed
"""
self.__certDN = None
self.__hostname = None
if certDN is not None:
self.certDN = certDN
if hostname is not None:
self.hostname = hostname
if subj_alt_name_match:
if not SUBJ_ALT_NAME_SUPPORT:
log.warning('Overriding "subj_alt_name_match" keyword setting: '
'peer verification with subjectAltNames is disabled')
self.__subj_alt_name_match = False
else:
self.__subj_alt_name_match = True
else:
log.debug('Disabling peer verification with subject '
'subjectAltNames!')
self.__subj_alt_name_match = False
def __call__(self, connection, peerCert, errorStatus, errorDepth,
preverifyOK):
"""Verify server certificate
@type connection: OpenSSL.SSL.Connection
@param connection: SSL connection object
@type peerCert: basestring
@param peerCert: server host certificate as OpenSSL.crypto.X509
instance
@type errorStatus: int
@param errorStatus: error status passed from caller. This is the value
returned by the OpenSSL C function X509_STORE_CTX_get_error(). Look-up
x509_vfy.h in the OpenSSL source to get the meanings of the different
codes. PyOpenSSL doesn't help you!
@type errorDepth: int
@param errorDepth: a non-negative integer representing where in the
certificate chain the error occurred. If it is zero it occured in the
end entity certificate, one if it is the certificate which signed the
end entity certificate and so on.
@type preverifyOK: int
@param preverifyOK: the error status - 0 = Error, 1 = OK of the current
SSL context irrespective of any verification checks done here. If this
function yields an OK status, it should enforce the preverifyOK value
so that any error set upstream overrides and is honoured.
@rtype: int
@return: status code - 0/False = Error, 1/True = OK
"""
if peerCert.has_expired():
# Any expired certificate in the chain should result in an error
log.error('Certificate %r in peer certificate chain has expired',
peerCert.get_subject())
return False
elif errorDepth == 0:
# Only interested in DN of last certificate in the chain - this must
# match the expected Server DN setting
peerCertSubj = peerCert.get_subject()
peerCertDN = peerCertSubj.get_components()
peerCertDN.sort()
if self.certDN is None:
# Check hostname against peer certificate CN field instead:
if self.hostname is None:
log.error('No "hostname" or "certDN" set to check peer '
'certificate against')
return False
# Check for subject alternative names
if self.__subj_alt_name_match:
dns_names = self._get_subj_alt_name(peerCert)
if self.hostname in dns_names:
return preverifyOK
# If no subjectAltNames, default to check of subject Common Name
if peerCertSubj.commonName == self.hostname:
return preverifyOK
else:
log.error('Peer certificate CN %r doesn\'t match the '
'expected CN %r', peerCertSubj.commonName,
self.hostname)
return False
else:
if peerCertDN == self.certDN:
return preverifyOK
else:
log.error('Peer certificate DN %r doesn\'t match the '
'expected DN %r', peerCertDN, self.certDN)
return False
else:
return preverifyOK
@classmethod
def _get_subj_alt_name(cls, peer_cert):
'''Extract subjectAltName DNS name settings from certificate extensions
@param peer_cert: peer certificate in SSL connection. subjectAltName
settings if any will be extracted from this
@type peer_cert: OpenSSL.crypto.X509
'''
# Search through extensions
dns_name = []
general_names = SubjectAltName()
for i in range(peer_cert.get_extension_count()):
ext = peer_cert.get_extension(i)
ext_name = ext.get_short_name()
if ext_name == cls.SUBJ_ALT_NAME_EXT_NAME:
# PyOpenSSL returns extension data in ASN.1 encoded form
ext_dat = ext.get_data()
decoded_dat = der_decoder.decode(ext_dat,
asn1Spec=general_names)
for name in decoded_dat:
if isinstance(name, SubjectAltName):
for entry in range(len(name)):
component = name.getComponentByPosition(entry)
dns_name.append(str(component.getComponent()))
return dns_name
def _getCertDN(self):
return self.__certDN
def _setCertDN(self, val):
if isinstance(val, basestring):
# Allow for quoted DN
certDN = val.strip('"')
dnFields = self.__class__.PARSER_RE.split(certDN)
if len(dnFields) < 2:
raise TypeError('Error parsing DN string: "%s"' % certDN)
self.__certDN = zip(dnFields[1::2], dnFields[2::2])
self.__certDN.sort()
elif not isinstance(val, list):
for i in val:
if not len(i) == 2:
raise TypeError('Expecting list of two element DN field, '
'DN field value pairs for "certDN" '
'attribute')
self.__certDN = val
else:
raise TypeError('Expecting list or string type for "certDN" '
'attribute')
certDN = property(fget=_getCertDN,
fset=_setCertDN,
doc="Distinguished Name for Server Certificate")
# Get/Set Property methods
def _getHostname(self):
return self.__hostname
def _setHostname(self, val):
if not isinstance(val, basestring):
raise TypeError("Expecting string type for hostname "
"attribute")
self.__hostname = val
hostname = property(fget=_getHostname,
fset=_setHostname,
doc="hostname of server")