gen_key_credentials.py

"""
@author: Carlo Pires <carlopires@gmail.com>

To generate the certificate with openssl:
    openssl genrsa 2048 > o365app.key
    openssl req -new -x509 -nodes -sha512 -days 365 -key o365app.key > o365app.crt
    
To generate key credentials for MS Azure:
    python gen_key_credentials.py o365app.crt
"""
import sys
import ssl
import uuid
import json
import binascii
import hashlib


def gen_key_credentials_from_crt(filename):
    with open(filename, 'r') as cert:
        crt = cert.read()

    cert_raw = ssl.PEM_cert_to_DER_cert(crt)
    cert_b64 = binascii.b2a_base64(cert_raw)[:-1]
    cert_hash = hashlib.sha1(cert_raw).digest()
    cert_hash_b64 = binascii.b2a_base64(cert_hash)[:-1]
    cert_id = str(uuid.uuid4())

    key_credentials = {
        'keyCredentials': [{
            'customKeyIdentifier': cert_hash_b64.decode(),
            'keyId': cert_id,
            'type': 'AsymmetricX509Cert',
            'usage': 'Verify',
            'value':  cert_b64.decode(),
        }]
    }

    return json.dumps(key_credentials, indent=2)


if __name__ == '__main__':
    if len(sys.argv) != 2:
        print('Use: {} <certificate_file.pem>')
    else:
        print(gen_key_credentials_from_crt(sys.argv[1]))