131 lines
4.2 KiB
Python
131 lines
4.2 KiB
Python
"""
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.. module: lemur.certificates.verify
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:platform: Unix
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:copyright: (c) 2015 by Netflix Inc., see AUTHORS for more
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:license: Apache, see LICENSE for more details.
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.. moduleauthor:: Kevin Glisson <kglisson@netflix.com>
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"""
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import requests
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import subprocess
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from requests.exceptions import ConnectionError, InvalidSchema
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from cryptography import x509
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from cryptography.hazmat.backends import default_backend
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from lemur.utils import mktempfile
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from lemur.common.utils import parse_certificate
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def ocsp_verify(cert_path, issuer_chain_path):
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"""
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Attempts to verify a certificate via OCSP. OCSP is a more modern version
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of CRL in that it will query the OCSP URI in order to determine if the
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certificate has been revoked
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:param cert_path:
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:param issuer_chain_path:
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:return bool: True if certificate is valid, False otherwise
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"""
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command = ['openssl', 'x509', '-noout', '-ocsp_uri', '-in', cert_path]
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p1 = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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url, err = p1.communicate()
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p2 = subprocess.Popen(['openssl', 'ocsp', '-issuer', issuer_chain_path,
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'-cert', cert_path, "-url", url.strip()], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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message, err = p2.communicate()
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p_message = message.decode('utf-8')
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if 'error' in p_message or 'Error' in p_message:
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raise Exception("Got error when parsing OCSP url")
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elif 'revoked' in p_message:
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return
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elif 'good' not in p_message:
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raise Exception("Did not receive a valid response")
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return True
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def crl_verify(cert_path):
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"""
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Attempts to verify a certificate using CRL.
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:param cert_path:
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:return: True if certificate is valid, False otherwise
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:raise Exception: If certificate does not have CRL
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"""
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with open(cert_path, 'rt') as c:
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cert = parse_certificate(c.read())
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distribution_points = cert.extensions.get_extension_for_oid(x509.OID_CRL_DISTRIBUTION_POINTS).value
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for p in distribution_points:
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point = p.full_name[0].value
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try:
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response = requests.get(point)
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if response.status_code != 200:
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raise Exception("Unable to retrieve CRL: {0}".format(point))
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except InvalidSchema:
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# Unhandled URI scheme (like ldap://); skip this distribution point.
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continue
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except ConnectionError:
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raise Exception("Unable to retrieve CRL: {0}".format(point))
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crl = x509.load_der_x509_crl(response.content, backend=default_backend())
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for r in crl:
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if cert.serial == r.serial_number:
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try:
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reason = r.extensions.get_extension_for_class(x509.CRLReason).value
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# Handle "removeFromCRL" revoke reason as unrevoked; continue with the next distribution point.
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# Per RFC 5280 section 6.3.3 (k): https://tools.ietf.org/html/rfc5280#section-6.3.3
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if reason == x509.ReasonFlags.remove_from_crl:
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break
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except x509.ExtensionNotFound:
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pass
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return
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return True
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def verify(cert_path, issuer_chain_path):
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"""
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Verify a certificate using OCSP and CRL
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:param cert_path:
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:param issuer_chain_path:
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:return: True if valid, False otherwise
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"""
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# OCSP is our main source of truth, in a lot of cases CRLs
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# have been deprecated and are no longer updated
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try:
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return ocsp_verify(cert_path, issuer_chain_path)
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except Exception as e:
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try:
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return crl_verify(cert_path)
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except Exception as e:
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raise Exception("Failed to verify")
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def verify_string(cert_string, issuer_string):
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"""
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Verify a certificate given only it's string value
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:param cert_string:
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:param issuer_string:
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:return: True if valid, False otherwise
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"""
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with mktempfile() as cert_tmp:
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with open(cert_tmp, 'w') as f:
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f.write(cert_string)
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with mktempfile() as issuer_tmp:
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with open(issuer_tmp, 'w') as f:
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f.write(issuer_string)
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status = verify(cert_tmp, issuer_tmp)
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return status
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