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verify_attestation_chains.py
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verify_attestation_chains.py
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#!/usr/bin/env python
# Copyright 2021 Google, LLC.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""This application verifies HSM attestations using certificate chains
obtained from Cloud HSM and the HSM manufacturer.
For more information, visit https://cloud.google.com/kms/docs/attest-key.
"""
# [START kms_verify_chains]
import argparse
import gzip
import io
import zipfile
from cryptography import exceptions
from cryptography import x509
from cryptography.hazmat import backends
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
import pem
import requests
ATTESTATION_SIGNATURE_LEN = 256
MANUFACTURER_CERT_URL = 'https://www.marvell.com/content/dam/marvell/en/public-collateral/security-solutions/liquid_security_certificate.zip'
# <Name(C=US,ST=California,L=San Jose,O=Cavium\, Inc.,OU=LiquidSecurity,CN=localca.liquidsecurity.cavium.com)>
MANUFACTURER_CERT_SUBJECT_BYTES = (
b'0\x81\x911\x0b0\t\x06\x03U\x04\x06\x13\x02US1\x130\x11\x06\x03U\x04\x08'
b'\x0c\nCalifornia1\x110\x0f\x06\x03U\x04\x07\x0c\x08San Jose1\x150\x13\x06'
b'\x03U\x04\n\x0c\x0cCavium, Inc.1\x170\x15\x06\x03U\x04\x0b\x0c\x0e'
b'LiquidSecurity1*0(\x06\x03U\x04\x03\x0c!localca.liquidsecurity.cavium.com'
)
# The owner root cert can be obtained from
# 'https://www.gstatic.com/cloudhsm/roots/global_1498867200.pem'
OWNER_ROOT_CERT_PEM = """Certificate:
Data:
Version: 3 (0x2)
Serial Number: 3 (0x3)
Signature Algorithm: sha256WithRSAEncryption
Issuer: C = US, ST = CA, L = Mountain View, O = Google Inc, CN = Hawksbill Root v1 prod
Validity
Not Before: Jul 1 00:00:00 2017 GMT
Not After : Jan 1 00:00:00 2030 GMT
Subject: C = US, ST = CA, L = Mountain View, O = Google Inc, CN = Hawksbill Root v1 prod
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public-Key: (2048 bit)
Modulus:
00:ac:2e:a8:62:89:21:a0:70:92:df:b0:8e:c3:93:
4d:26:38:db:a5:a2:5f:6b:1e:6d:a8:6c:2c:83:d6:
5b:9a:f8:02:a0:f8:b0:16:fb:5c:da:b9:9b:b9:8b:
4d:bc:15:26:e0:0e:4f:2f:b5:20:43:1c:31:7e:5e:
c1:67:a9:36:c8:19:5e:c2:b5:a8:b6:96:76:90:7b:
55:15:4d:53:16:10:f0:62:d5:d8:98:19:c7:9e:0e:
b2:69:26:a3:f3:d9:a5:d3:70:88:21:ac:62:12:7b:
2a:be:20:2e:33:db:9b:90:a7:b1:bf:0f:c0:11:7a:
c2:98:a9:8c:4d:36:a7:1f:66:53:08:93:4b:3a:12:
1e:1a:3f:2b:c2:5d:8b:4b:97:d4:17:0f:41:83:27:
a9:f3:e0:d9:82:f8:5c:37:d4:1e:5d:e4:a8:3d:59:
7c:43:64:e6:02:d7:35:39:f4:95:db:77:1c:73:78:
2f:c4:26:8d:64:d4:01:e0:86:da:3f:27:c7:9d:bd:
32:25:e4:d4:34:6a:13:87:2a:85:19:ce:18:43:46:
c5:41:8a:81:66:ca:65:6e:c1:a1:ce:71:74:d4:b0:
77:b7:35:39:0d:c9:e2:c8:7e:81:69:b1:04:38:5d:
c1:fd:92:33:ba:ed:85:d3:91:d0:96:78:d6:30:fc:
56:19
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints: critical
CA:TRUE
X509v3 Key Usage: critical
Digital Signature, Certificate Sign, CRL Sign
X509v3 Subject Key Identifier:
31:E8:52:DF:E1:49:F8:12:7B:7C:6E:E7:4E:91:7A:97:75:BC:A8:AE
Signature Algorithm: sha256WithRSAEncryption
8f:12:8e:8e:7a:fb:59:82:a8:0f:e6:be:b8:09:5d:17:c8:8e:
c1:3a:c7:a4:52:d4:0d:2e:ac:a8:5c:b1:f4:52:ee:b7:c4:25:
9a:2a:32:fc:91:3d:ba:29:9a:ed:c8:de:1f:75:39:54:16:d1:
72:74:e0:95:a0:e2:41:36:9c:f8:95:c2:21:10:29:12:5f:4d:
d1:b0:e1:a1:5b:c5:79:3c:d1:23:c9:c9:74:c2:42:58:fa:1b:
35:75:77:30:7a:58:b2:07:e0:cd:ec:21:e2:51:54:59:08:21:
be:c7:05:df:6e:55:81:21:0d:d1:ad:61:81:77:27:3e:bd:39:
81:df:bd:91:32:3d:cc:5d:eb:de:fc:a7:73:26:2f:cd:88:a7:
70:65:f4:35:06:b3:d6:02:56:e1:ba:e6:d5:6f:b0:4d:b5:95:
cb:c6:34:a3:a7:35:79:99:bb:bf:cb:07:a0:d4:a0:de:f2:2c:
e8:9b:27:43:c6:c0:5c:ae:62:da:a3:bf:01:76:50:bb:6e:70:
1f:56:8f:41:cb:7c:41:d1:b0:c7:62:41:b2:31:23:99:6a:47:
b8:10:c0:5c:f0:9e:b0:3e:5c:bb:d5:33:cc:38:1c:a5:dc:26:
8b:b5:e2:76:5e:f8:92:3d:df:fc:78:2b:39:e8:a6:45:d3:9b:
f2:51:b9:fc
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
"""
def get_manufacturer_root_certificate():
"""Gets the manufacturer root certificate."""
resp = requests.get(MANUFACTURER_CERT_URL)
tmp_file = io.BytesIO(resp.content)
zip_file = zipfile.ZipFile(tmp_file)
with zip_file.open('liquid_security_certificate.crt') as f:
return x509.load_pem_x509_certificate(f.read(), backends.default_backend())
def get_owner_root_certificate():
"""Gets the owner root certificate."""
return x509.load_pem_x509_certificate(
OWNER_ROOT_CERT_PEM.encode('utf-8'), backends.default_backend())
def verify_certificate(signing_cert, issued_cert):
"""Verifies the signing_cert issued the issued_cert.
Args:
signing_cert: The certificate used to verify the issued certificate's
signature.
issued_cert: The issued certificate.
Returns:
True if the signing_cert issued the issued_cert.
"""
if signing_cert.subject != issued_cert.issuer:
return False
try:
signing_cert.public_key().verify(issued_cert.signature,
issued_cert.tbs_certificate_bytes,
padding.PKCS1v15(),
issued_cert.signature_hash_algorithm)
return True
except exceptions.InvalidSignature:
return False
return False
def get_issued_certificate(issuer_cert,
untrusted_certs,
predicate=lambda _: True):
"""Finds an issued certificates issued by an issuer certificate.
The issued certificate is removed from the set of untrusted certificates.
Args:
issuer_cert: The issuer certificate.
untrusted_certs: A set of untrusted certificates.
predicate: An additional condition for the issued certificate.
Returns:
A certificate within the set of untrusted certificates that was issued
by the issuer certificate and matches the predicate.
"""
for cert in untrusted_certs:
if verify_certificate(issuer_cert, cert) and predicate(cert):
untrusted_certs.remove(cert)
return cert
return None
def verify_attestation(cert, attestation):
"""Verifies that the certificate signed the attestation.
Args:
cert: The certificate used to verify the attestation.
attestation: The attestation to verify.
Returns:
True if the certificate verified the attestation.
"""
data = attestation[:-ATTESTATION_SIGNATURE_LEN]
signature = attestation[-ATTESTATION_SIGNATURE_LEN:]
try:
cert.public_key().verify(signature, data, padding.PKCS1v15(),
hashes.SHA256())
return True
except exceptions.InvalidSignature:
return False
return False
def verify(certs_file, attestation_file):
"""Verifies that the certificate chains are valid.
Args:
certs_file: The certificate chains filename.
attestation_file: The attestation filename.
Returns:
True if the certificate chains are valid.
"""
mfr_root_cert = get_manufacturer_root_certificate()
if (mfr_root_cert.subject.public_bytes(backends.default_backend()) !=
MANUFACTURER_CERT_SUBJECT_BYTES):
return False
untrusted_certs_pem = pem.parse_file(certs_file)
untrusted_certs = {
x509.load_pem_x509_certificate(
str(cert_pem).encode('utf-8'), backends.default_backend())
for cert_pem in untrusted_certs_pem
}
# Build the manufacturer certificate chain.
mfr_card_cert = get_issued_certificate(mfr_root_cert, untrusted_certs)
mfr_partition_cert = get_issued_certificate(mfr_card_cert, untrusted_certs)
if not mfr_card_cert or not mfr_partition_cert:
print('Invalid HSM manufacturer certificate chain.')
return False
print('Successfully built HSM manufacturer certificate chain.')
owner_root_cert = get_owner_root_certificate()
# Build the owner card certificate chain.
def _check_card_pub_key(cert):
cert_pub_key_bytes = cert.public_key().public_bytes(
serialization.Encoding.DER,
serialization.PublicFormat.SubjectPublicKeyInfo)
mfr_card_pub_key_bytes = mfr_card_cert.public_key().public_bytes(
serialization.Encoding.DER,
serialization.PublicFormat.SubjectPublicKeyInfo)
return cert_pub_key_bytes == mfr_card_pub_key_bytes
owner_card_cert = get_issued_certificate(
owner_root_cert, untrusted_certs, predicate=_check_card_pub_key)
# Build the owner partition certificate chain.
def _check_partition_pub_key(cert):
cert_pub_key_bytes = cert.public_key().public_bytes(
serialization.Encoding.PEM,
serialization.PublicFormat.SubjectPublicKeyInfo)
mfr_partition_pub_key_bytes = mfr_partition_cert.public_key().public_bytes(
serialization.Encoding.PEM,
serialization.PublicFormat.SubjectPublicKeyInfo)
return cert_pub_key_bytes == mfr_partition_pub_key_bytes
owner_partition_cert = get_issued_certificate(
owner_root_cert, untrusted_certs, predicate=_check_partition_pub_key)
if not owner_card_cert or not owner_partition_cert or untrusted_certs:
print('Invalid HSM owner certificate chain.')
return False
print('Successfully built HSM owner certificate chain.')
with gzip.open(attestation_file, 'rb') as f:
attestation = f.read()
return (verify_attestation(mfr_partition_cert, attestation) and
verify_attestation(owner_partition_cert, attestation))
if __name__ == '__main__':
parser = argparse.ArgumentParser(
description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument(
'--certificates', help='The certificate chains filename.')
parser.add_argument('--attestation', help='The attestation filename.')
args = parser.parse_args()
if verify(args.certificates, args.attestation):
print('The attestation has been verified.')
else:
print('The attestation could not be verified.')
# [END kms_verify_chains]