create-client

#!/usr/bin/env python

# Copyright 2017-2019 Fizyr B.V. - https://fizyr.com
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import os
import sys
from pathlib import Path

from argparse import ArgumentParser
from datetime import datetime, timedelta
from typing import List, Optional, Tuple

from cryptography import x509
from cryptography.x509.oid import NameOID, ExtendedKeyUsageOID
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization

from message import msg, msg2, error
import util
import cert_tools


crypto_backend = default_backend()


def parseArguments():
	parser = ArgumentParser(description='Create new client certificate using for a parent CA certificate.')
	parser.add_argument('PARENT',   help='Parent CA certificate')
	parser.add_argument('MACHINE',  help='Machine name.')
	parser.add_argument('--key',    help='Path to store the generated key.')
	parser.add_argument('--csr',    help='Path to store the generated CSR.')
	return parser.parse_args()


def create_csr(key_file: Path, csr_file: Path, dn: x509.Name, dns_name: str) -> int:
	files = [key_file, csr_file]

	# Make sure the files don't exist yet.
	for file in files:
		if file.exists():
			error('File already exists: {}', file)
			return 1

	# Generate key with modified umask.
	msg('Generating key pair: {}', key_file)
	umask = util.or_umask(0o277)
	key = cert_tools.generate_rsa_key(key_file)
	os.umask(umask)

	# Create a CSR for the parent CA to sign.
	msg('Making CSR: {}', csr_file)
	cert_tools.make_csr(csr_file, key=key, name=dn, extensions=cert_tools.client_extensions(dns_name))

	return 0


def main():
	now  = datetime.now().astimezone()
	args = parseArguments()

	ca_cert = cert_tools.load_first_certificate(util.read_file(args.PARENT))
	ca_dns  = cert_tools.get_first_dns_name(cert_tools.get_subject_alt_names(ca_cert))

	if not ca_dns:
		error('Parent certificate does not have a subject alternative DNS name')
		return 1

	ca_dns       = ca_dns.value.lower()
	args.MACHINE = args.MACHINE.lower()

	client_name = cert_tools.prefix_name(ca_cert.subject, NameOID.COMMON_NAME, args.MACHINE)
	client_dns  = '{}.{}'.format(args.MACHINE, ca_dns)


	key_file = Path(args.key or '{}-{:%Y-%m-%d-%H-%M-%S}.key.pem'.format(client_dns, now))
	csr_file = Path(args.csr or '{}-{:%Y-%m-%d-%H-%M-%S}.csr.pem'.format(client_dns, now))

	return create_csr(key_file, csr_file, client_name, client_dns)


if __name__ == '__main__':
	sys.exit(main())