create-ca

#!/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
import subprocess

from cryptography import x509

from typing import List, Optional

from message import msg, msg2, error

import util
import cert_tools

def parseArguments():
	parser = ArgumentParser(description='Create new root CA key and certificate.')
	parser.add_argument('CA_DIR',                              help='Root directory for the CA files.')
	parser.add_argument('--csr',          action='store_true', help='Create a CSR to be signed by the parent CA.')
	parser.add_argument('--self-signed',  action='store_true', help='Create a self signed certificate, useful for a root CA.')
	parser.add_argument('--reuse-key',    action='store_true', help='Re-use the existing CA key, useful for reneweing the certificate of a CA.')
	parser.add_argument('--import-cert',                       help='Import an existing certificate as CA cert.')
	parser.add_argument('--days',            type=int,         help='The validity period of the self signed certificate in days, starting today.')
	parser.add_argument('--max-path-length', type=int,         help='The maximum path of intermediate CA\'s following the newly created one.')
	return parser.parse_args()


def create_csr(
	root: Path,
	dn: x509.Name,
	dns_name,
	reuse_key: bool,
	max_path_length: Optional[int],
	now: datetime,
) -> int:
	key_link = root / 'ca.key.pem'

	csr_file = root / 'ca-csr' / '{}-{:%Y-%m-%d-%H-%M-%S}.csr.pem'.format(dns_name, now)
	csr_link = root / 'ca.csr.pem'

	files        = [csr_file]
	links        = [csr_link]
	public_dirs  = [root / 'signed', csr_file.parent]

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

	# Make sure the symlinks are non-existing or indeed symlinks.
	for link in links:
		if link.exists() and not link.is_symlink():
			error('File exists but it not a symlink: {}', link)
			return 1

	# Create all public directories.
	for dir in public_dirs:
		os.makedirs(dir, exist_ok=True)

	if reuse_key:
		# Load existing private key.
		key = cert_tools.load_key(key_link)
	else:
		key_file = root / 'ca-key' / '{}-{:%Y-%m-%d-%H-%M-%S}.key.pem'.format(dns_name, now)
		msg('Generating key pair: {}', key_file)

		# Create private directories with modified umask.
		umask = util.or_umask(0o077)
		os.makedirs(key_file.parent, exist_ok=True)

		# Generate key with modified umask.
		util.or_umask(0o277)
		key = cert_tools.generate_rsa_key(key_file)
		os.umask(umask)
		files.append(key_file)
		links.append(key_link)

	# 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.ca_extensions(dns_name, max_path_length),
	)

	# Create/update all the symlinks.
	for file, link in zip(files, links):
		util.force_relative_symlink(file, link);

	return 0


def create_self_signed(
	root: Path,
	dn: x509.Name,
	dns_name: str,
	reuse_key: bool,
	max_path_length: Optional[int],
	days: int,
	now: datetime,
) -> int:
	key_link = root / 'ca.key.pem'

	cert_file = root / 'ca-cert' / '{}-{:%Y-%m-%d-%H-%M-%S}.csr.pem'.format(dns_name, now)
	cert_link = root / 'ca.cert.pem'

	files        = [cert_file]
	links        = [cert_link]
	public_dirs  = [root / 'signed', cert_file.parent]
	private_dirs = [key_file.parent]

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

	# Make sure the symlinks are non-existing or indeed symlinks.
	for link in links:
		if link.exists() and not link.is_symlink():
			error('File exists but it not a symlink: {}', link)
			return 1

	# Create all public directories.
	for dir in public_dirs:
		os.makedirs(dir, exist_ok=True)

	if reuse_key:
		# Load existing private key.
		key = cert_tools.load_key(key_link)
	else:
		key_file = root / 'ca-key' / '{}-{:%Y-%m-%d-%H-%M-%S}.key.pem'.format(dns_name, now)
		msg('Generating key pair: {}', key_file)

		# Create private directories with modified umask.
		umask = util.or_umask(0o077)
		os.makedirs(key_file.parent, exist_ok=True)

		# Generate key with modified umask.
		util.or_umask(0o277)
		key = cert_tools.generate_rsa_key(key_file)
		os.umask(umask)
		files.append(key_file)
		links.append(key_link)

	# Create and/or bump serial number.
	serial = cert_tools.bump_serial(root / 'serial')

	# Create self signed certificate.
	msg('Making self signed certificate: {}', cert_file)
	cert_tools.make_self_signed_cert(
		cert_file,
		key        = key,
		name       = dn,
		serial     = serial,
		extensions = cert_tools.ca_extensions(dns_name, max_path_length),
		days       = days,
		now        = now,
	)

	# Create/update all the symlinks.
	for file, link in zip(files, links):
		util.force_relative_symlink(file, link);

	return 0


def import_certificate(root: Path, cert_in: Path):
	cert_file = root / 'ca-cert' / cert_in.name
	cert_link = root / 'ca.cert.pem'

	files        = [cert_file]
	links        = [cert_link]
	public_dirs  = [root / 'signed', cert_file.parent]

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

	# Make sure the symlinks are non-existing or indeed symlinks.
	for link in links:
		if link.exists() and not link.is_symlink():
			error('File exists but it not a symlink: {}', link)
			return 1

	# Create all public directories.
	for dir in public_dirs:
		os.makedirs(dir, exist_ok=True)

	# Copy the certificate.
	util.write_file(cert_file, util.read_file(cert_in))

	# Create/update all the symlinks.
	for file, link in zip(files, links):
		util.force_relative_symlink(file, link);

	return 0


def count_bools(*args) -> int:
	total = 0
	for arg in args:
		if arg: total += 1
	return total


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

	dn  = cert_tools.parse_dn(util.read_file(root / 'dirname').decode('utf8'))
	dns = util.read_file(root / 'domain').decode('utf8').strip()

	if count_bools(args.csr, args.self_signed, args.import_cert is not None) != 1:
		error('You must choose exactly one of --csr, --self-signed and --import-cert')
		return 1

	if args.csr:
		return create_csr(root, dn, dns, args.reuse_key, args.max_path_length, now)
	elif args.self_signed:
		if args.days is None:
			error('The options --days is required when using --self-signed')
			return 1
		return create_self_signed(root, dn, dns, args.reuse_key, args.max_path_length, args.days, now)
	elif args.import_cert is not None:
		return import_certificate(root, Path(args.import_cert))

	return 0


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