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Þ'¯°ÌME[YéïĵÂCå½ Ué©Áû'Ê9%eÔðNU”ë‘ÌsD3/®+UI˜9h.WC”빓$#:pz:YÓ ¿xž* ³$Í +$kñAŠ‹†¢ Uê>¸)_š¬÷©ßAÂÔb9ÇU ¯¾á•9¯ÏÏ÷O÷¼¼Fähal1‰3Ì[Ïr•´UCksNÐ] R‘¸¥H+§Šé†c©vÖÞ0iÓ76s†î!§=ß ¼~Ô'°Ãmäoäš³ªøi1úÉ)³yV8 CLÄØÁ‘WYïi€H6ÖÑiámø^ÈY´°Ñ7¥Û*—Ñ©L«Qƒï—Ùrÿ ›£Ð*š¸ˆL©ˆ$ˆ ÷¾D§9È®«qbqC)–ˆïv´çñsÑVT­Ø, <àïºÀO«Jý·õ àfPìð .wFšir´þ’2_Y *Æ€x\« ì€9š@ Ž|F⇥ˆkZ@hÖÄ0t¿-<“‹qµ¾*ZL¤Ú)&BJpÓF5=$„at*Zš$’ÑtdûÝRI1 2Ž‰$€$I$#‰SÞ’Hë¬ï;Á$¡t$’`<(ñÇt)$‡Ð.Êf¢X’Kt=Éé$‚ˆªè¢oÝëòI%Rgcª÷ŠyI%¡‰ÿ !ñ)´õ $¤ Ô’IIGÿÙimport base64 import datetime import ssl from urllib.parse import urljoin, urlparse import cryptography.hazmat.primitives.hashes import requests from cryptography import hazmat, x509 from cryptography.exceptions import InvalidSignature from cryptography.hazmat import backends from cryptography.hazmat.primitives.asymmetric.dsa import DSAPublicKey from cryptography.hazmat.primitives.asymmetric.ec import ECDSA, EllipticCurvePublicKey from cryptography.hazmat.primitives.asymmetric.padding import PKCS1v15 from cryptography.hazmat.primitives.asymmetric.rsa import RSAPublicKey from cryptography.hazmat.primitives.hashes import SHA1, Hash from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat from cryptography.x509 import ocsp from redis.exceptions import AuthorizationError, ConnectionError def _verify_response(issuer_cert, ocsp_response): pubkey = issuer_cert.public_key() try: if isinstance(pubkey, RSAPublicKey): pubkey.verify( ocsp_response.signature, ocsp_response.tbs_response_bytes, PKCS1v15(), ocsp_response.signature_hash_algorithm, ) elif isinstance(pubkey, DSAPublicKey): pubkey.verify( ocsp_response.signature, ocsp_response.tbs_response_bytes, ocsp_response.signature_hash_algorithm, ) elif isinstance(pubkey, EllipticCurvePublicKey): pubkey.verify( ocsp_response.signature, ocsp_response.tbs_response_bytes, ECDSA(ocsp_response.signature_hash_algorithm), ) else: pubkey.verify(ocsp_response.signature, ocsp_response.tbs_response_bytes) except InvalidSignature: raise ConnectionError("failed to valid ocsp response") def _check_certificate(issuer_cert, ocsp_bytes, validate=True): """A wrapper the return the validity of a known ocsp certificate""" ocsp_response = ocsp.load_der_ocsp_response(ocsp_bytes) if ocsp_response.response_status == ocsp.OCSPResponseStatus.UNAUTHORIZED: raise AuthorizationError("you are not authorized to view this ocsp certificate") if ocsp_response.response_status == ocsp.OCSPResponseStatus.SUCCESSFUL: if ocsp_response.certificate_status != ocsp.OCSPCertStatus.GOOD: raise ConnectionError( f'Received an {str(ocsp_response.certificate_status).split(".")[1]} ' "ocsp certificate status" ) else: raise ConnectionError( "failed to retrieve a sucessful response from the ocsp responder" ) if ocsp_response.this_update >= datetime.datetime.now(): raise ConnectionError("ocsp certificate was issued in the future") if ( ocsp_response.next_update and ocsp_response.next_update < datetime.datetime.now() ): raise ConnectionError("ocsp certificate has invalid update - in the past") responder_name = ocsp_response.responder_name issuer_hash = ocsp_response.issuer_key_hash responder_hash = ocsp_response.responder_key_hash cert_to_validate = issuer_cert if ( responder_name is not None and responder_name == issuer_cert.subject or responder_hash == issuer_hash ): cert_to_validate = issuer_cert else: certs = ocsp_response.certificates responder_certs = _get_certificates( certs, issuer_cert, responder_name, responder_hash ) try: responder_cert = responder_certs[0] except IndexError: raise ConnectionError("no certificates found for the responder") ext = responder_cert.extensions.get_extension_for_class(x509.ExtendedKeyUsage) if ext is None or x509.oid.ExtendedKeyUsageOID.OCSP_SIGNING not in ext.value: raise ConnectionError("delegate not autorized for ocsp signing") cert_to_validate = responder_cert if validate: _verify_response(cert_to_validate, ocsp_response) return True def _get_certificates(certs, issuer_cert, responder_name, responder_hash): if responder_name is None: certificates = [ c for c in certs if _get_pubkey_hash(c) == responder_hash and c.issuer == issuer_cert.subject ] else: certificates = [ c for c in certs if c.subject == responder_name and c.issuer == issuer_cert.subject ] return certificates def _get_pubkey_hash(certificate): pubkey = certificate.public_key() # https://stackoverflow.com/a/46309453/600498 if isinstance(pubkey, RSAPublicKey): h = pubkey.public_bytes(Encoding.DER, PublicFormat.PKCS1) elif isinstance(pubkey, EllipticCurvePublicKey): h = pubkey.public_bytes(Encoding.X962, PublicFormat.UncompressedPoint) else: h = pubkey.public_bytes(Encoding.DER, PublicFormat.SubjectPublicKeyInfo) sha1 = Hash(SHA1(), backend=backends.default_backend()) sha1.update(h) return sha1.finalize() def ocsp_staple_verifier(con, ocsp_bytes, expected=None): """An implemention of a function for set_ocsp_client_callback in PyOpenSSL. This function validates that the provide ocsp_bytes response is valid, and matches the expected, stapled responses. """ if ocsp_bytes in [b"", None]: raise ConnectionError("no ocsp response present") issuer_cert = None peer_cert = con.get_peer_certificate().to_cryptography() for c in con.get_peer_cert_chain(): cert = c.to_cryptography() if cert.subject == peer_cert.issuer: issuer_cert = cert break if issuer_cert is None: raise ConnectionError("no matching issuer cert found in certificate chain") if expected is not None: e = x509.load_pem_x509_certificate(expected) if peer_cert != e: raise ConnectionError("received and expected certificates do not match") return _check_certificate(issuer_cert, ocsp_bytes) class OCSPVerifier: """A class to verify ssl sockets for RFC6960/RFC6961. This can be used when using direct validation of OCSP responses and certificate revocations. @see https://datatracker.ietf.org/doc/html/rfc6960 @see https://datatracker.ietf.org/doc/html/rfc6961 """ def __init__(self, sock, host, port, ca_certs=None): self.SOCK = sock self.HOST = host self.PORT = port self.CA_CERTS = ca_certs def _bin2ascii(self, der): """Convert SSL certificates in a binary (DER) format to ASCII PEM.""" pem = ssl.DER_cert_to_PEM_cert(der) cert = x509.load_pem_x509_certificate(pem.encode(), backends.default_backend()) return cert def components_from_socket(self): """This function returns the certificate, primary issuer, and primary ocsp server in the chain for a socket already wrapped with ssl. """ # convert the binary certifcate to text der = self.SOCK.getpeercert(True) if der is False: raise ConnectionError("no certificate found for ssl peer") cert = self._bin2ascii(der) return self._certificate_components(cert) def _certificate_components(self, cert): """Given an SSL certificate, retract the useful components for validating the certificate status with an OCSP server. Args: cert ([bytes]): A PEM encoded ssl certificate """ try: aia = cert.extensions.get_extension_for_oid( x509.oid.ExtensionOID.AUTHORITY_INFORMATION_ACCESS ).value except cryptography.x509.extensions.ExtensionNotFound: raise ConnectionError("No AIA information present in ssl certificate") # fetch certificate issuers issuers = [ i for i in aia if i.access_method == x509.oid.AuthorityInformationAccessOID.CA_ISSUERS ] try: issuer = issuers[0].access_location.value except IndexError: issuer = None # now, the series of ocsp server entries ocsps = [ i for i in aia if i.access_method == x509.oid.AuthorityInformationAccessOID.OCSP ] try: ocsp = ocsps[0].access_location.value except IndexError: raise ConnectionError("no ocsp servers in certificate") return cert, issuer, ocsp def components_from_direct_connection(self): """Return the certificate, primary issuer, and primary ocsp server from the host defined by the socket. This is useful in cases where different certificates are occasionally presented. """ pem = ssl.get_server_certificate((self.HOST, self.PORT), ca_certs=self.CA_CERTS) cert = x509.load_pem_x509_certificate(pem.encode(), backends.default_backend()) return self._certificate_components(cert) def build_certificate_url(self, server, cert, issuer_cert): """Return the complete url to the ocsp""" orb = ocsp.OCSPRequestBuilder() # add_certificate returns an initialized OCSPRequestBuilder orb = orb.add_certificate( cert, issuer_cert, cryptography.hazmat.primitives.hashes.SHA256() ) request = orb.build() path = base64.b64encode( request.public_bytes(hazmat.primitives.serialization.Encoding.DER) ) url = urljoin(server, path.decode("ascii")) return url def check_certificate(self, server, cert, issuer_url): """Checks the validitity of an ocsp server for an issuer""" r = requests.get(issuer_url) if not r.ok: raise ConnectionError("failed to fetch issuer certificate") der = r.content issuer_cert = self._bin2ascii(der) ocsp_url = self.build_certificate_url(server, cert, issuer_cert) # HTTP 1.1 mandates the addition of the Host header in ocsp responses header = { "Host": urlparse(ocsp_url).netloc, "Content-Type": "application/ocsp-request", } r = requests.get(ocsp_url, headers=header) if not r.ok: raise ConnectionError("failed to fetch ocsp certificate") return _check_certificate(issuer_cert, r.content, True) def is_valid(self): """Returns the validity of the certificate wrapping our socket. This first retrieves for validate the certificate, issuer_url, and ocsp_server for certificate validate. Then retrieves the issuer certificate from the issuer_url, and finally checks the valididy of OCSP revocation status. """ # validate the certificate try: cert, issuer_url, ocsp_server = self.components_from_socket() if issuer_url is None: raise ConnectionError("no issuers found in certificate chain") return self.check_certificate(ocsp_server, cert, issuer_url) except AuthorizationError: cert, issuer_url, ocsp_server = self.components_from_direct_connection() if issuer_url is None: raise ConnectionError("no issuers found in certificate chain") return self.check_certificate(ocsp_server, cert, issuer_url)