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import logging
from datetime import datetime, timedelta
try:
from pyasn1.codec.der import decoder, encoder
from pyasn1.type.univ import Any, ObjectIdentifier, OctetString
from pyasn1.type.char import BMPString, IA5String, UTF8String
from pyasn1.type.useful import GeneralizedTime
from pyasn1_modules.rfc2459 import Certificate, DirectoryString, SubjectAltName, GeneralNames, GeneralName
from pyasn1_modules.rfc2459 import id_ce_subjectAltName as SUBJECT_ALT_NAME
from pyasn1_modules.rfc2459 import id_at_commonName as COMMON_NAME
XMPP_ADDR = ObjectIdentifier('1.3.6.1.5.5.7.8.5')
SRV_NAME = ObjectIdentifier('1.3.6.1.5.5.7.8.7')
HAVE_PYASN1 = True
except ImportError:
HAVE_PYASN1 = False
log = logging.getLogger(__name__)
class CertificateError(Exception):
pass
def decode_str(data):
encoding = 'utf-16-be' if isinstance(data, BMPString) else 'utf-8'
return bytes(data).decode(encoding)
def extract_names(raw_cert):
results = {'CN': set(),
'DNS': set(),
'SRV': set(),
'URI': set(),
'XMPPAddr': set()}
cert = decoder.decode(raw_cert, asn1Spec=Certificate())[0]
tbs = cert.getComponentByName('tbsCertificate')
subject = tbs.getComponentByName('subject')
extensions = tbs.getComponentByName('extensions')
# Extract the CommonName(s) from the cert.
for rdnss in subject:
for rdns in rdnss:
for name in rdns:
oid = name.getComponentByName('type')
value = name.getComponentByName('value')
if oid != COMMON_NAME:
continue
value = decoder.decode(value, asn1Spec=DirectoryString())[0]
value = decode_str(value.getComponent())
results['CN'].add(value)
# Extract the Subject Alternate Names (DNS, SRV, URI, XMPPAddr)
for extension in extensions:
oid = extension.getComponentByName('extnID')
if oid != SUBJECT_ALT_NAME:
continue
value = decoder.decode(extension.getComponentByName('extnValue'),
asn1Spec=OctetString())[0]
sa_names = decoder.decode(value, asn1Spec=SubjectAltName())[0]
for name in sa_names:
name_type = name.getName()
if name_type == 'dNSName':
results['DNS'].add(decode_str(name.getComponent()))
if name_type == 'uniformResourceIdentifier':
value = decode_str(name.getComponent())
if value.startswith('xmpp:'):
results['URI'].add(value[5:])
elif name_type == 'otherName':
name = name.getComponent()
oid = name.getComponentByName('type-id')
value = name.getComponentByName('value')
if oid == XMPP_ADDR:
value = decoder.decode(value, asn1Spec=UTF8String())[0]
results['XMPPAddr'].add(decode_str(value))
elif oid == SRV_NAME:
value = decoder.decode(value, asn1Spec=IA5String())[0]
results['SRV'].add(decode_str(value))
return results
def extract_dates(raw_cert):
if not HAVE_PYASN1:
log.warning("Could not find pyasn1 module. " + \
"SSL certificate expiration COULD NOT BE VERIFIED.")
return None, None
cert = decoder.decode(raw_cert, asn1Spec=Certificate())[0]
tbs = cert.getComponentByName('tbsCertificate')
validity = tbs.getComponentByName('validity')
not_before = validity.getComponentByName('notBefore')
not_before = str(not_before.getComponent())
not_after = validity.getComponentByName('notAfter')
not_after = str(not_after.getComponent())
if isinstance(not_before, GeneralizedTime):
not_before = datetime.strptime(not_before, '%Y%m%d%H%M%SZ')
else:
not_before = datetime.strptime(not_before, '%y%m%d%H%M%SZ')
if isinstance(not_after, GeneralizedTime):
not_after = datetime.strptime(not_after, '%Y%m%d%H%M%SZ')
else:
not_after = datetime.strptime(not_after, '%y%m%d%H%M%SZ')
return not_before, not_after
def get_ttl(raw_cert):
not_before, not_after = extract_dates(raw_cert)
if not_after is None:
return None
return not_after - datetime.utcnow()
def verify(expected, raw_cert):
if not HAVE_PYASN1:
log.warning("Could not find pyasn1 module. " + \
"SSL certificate COULD NOT BE VERIFIED.")
return
not_before, not_after = extract_dates(raw_cert)
cert_names = extract_names(raw_cert)
now = datetime.utcnow()
if not_before > now:
raise CertificateError(
'Certificate has not entered its valid date range.')
if not_after <= now:
raise CertificateError(
'Certificate has expired.')
expected_wild = expected[expected.index('.'):]
expected_srv = '_xmpp-client.%s' % expected
for name in cert_names['XMPPAddr']:
if name == expected:
return True
for name in cert_names['SRV']:
if name == expected_srv or name == expected:
return True
for name in cert_names['DNS']:
if name == expected:
return True
if name.startswith('*'):
name_wild = name[name.index('.'):]
if expected_wild == name_wild:
return True
for name in cert_names['URI']:
if name == expected:
return True
for name in cert_names['CN']:
if name == expected:
return True
raise CertificateError(
'Could not match certficate against hostname: %s' % expected)
|
