thing.py

from cryptography import x509
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.backends import default_backend

cert_file = open('/etc/letsencrypt/live/www.example.com/cert.pem')
cert_data = cert_file.read()
cert = x509.load_pem_x509_certificate(data=cert_data, backend=default_backend())
cert_pk = cert.public_key()
cert_pn = cert_pk.public_numbers()


chain_file = open('/etc/letsencrypt/live/www.example.com/chain.pem')
chain_data = chain_file.read()
chain = x509.load_pem_x509_certificate(data=chain_data, backend=default_backend())
chain_pk = chain.public_key()
chain_pn = chain_pk.public_numbers()

"""
fullchain_file = open('/etc/letsencrypt/live/www.example.com/fullchain.pem')
fullchain_data = fullchain_file.read()
fullchain = x509.load_pem_x509_certificate(data=fullchain_data, backend=default_backend())
fullchain_pk = fullchain.public_key()
fullchain_pn = fullchain_pk.public_numbers()
"""

privkey_file = open('/etc/letsencrypt/live/www.example.com/privkey.pem')
privkey_data = privkey_file.read()

import ipdb; ipdb.set_trace()

#public_key = cert.public_key()
public_key = chain.public_key()

verifier = public_key.verifier(
        signature = cert.signature,
        padding = padding.PSS(
            mgf = padding.MGF1(hashes.SHA256()),
            salt_length = padding.PSS.MAX_LENGTH),
        algorithm = hashes.SHA256()
        )
verifier.update(cert.tbs_certificate_bytes)
#verifier.update(cert_data)
verifier.verify()