#
# Copyright (C) 2017  FreeIPA Contributors see COPYING for license
#
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
from __future__ import absolute_import, print_function

import argparse

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

import datetime
import six


class ExternalCA(object):
    """
    Provide external CA for testing
    """
    def __init__(self, days=365):
        self.now = datetime.datetime.utcnow()
        self.delta = datetime.timedelta(days=days)

    def create_ca(self, cn='example.test'):
        """Create root CA.

        :returns: bytes -- Root CA in PEM format.
        """
        self.ca_key = rsa.generate_private_key(
            public_exponent=65537,
            key_size=2048,
            backend=default_backend(),
        )

        self.ca_public_key = self.ca_key.public_key()

        subject = self.issuer = x509.Name([
            x509.NameAttribute(NameOID.COMMON_NAME, six.text_type(cn)),
        ])

        builder = x509.CertificateBuilder()
        builder = builder.subject_name(subject)
        builder = builder.issuer_name(self.issuer)
        builder = builder.public_key(self.ca_public_key)
        builder = builder.serial_number(x509.random_serial_number())
        builder = builder.not_valid_before(self.now)
        builder = builder.not_valid_after(self.now + self.delta)

        builder = builder.add_extension(
            x509.KeyUsage(
                digital_signature=False,
                content_commitment=False,
                key_encipherment=False,
                data_encipherment=False,
                key_agreement=False,
                key_cert_sign=True,
                crl_sign=True,
                encipher_only=False,
                decipher_only=False,
            ),
            critical=True,
        )

        builder = builder.add_extension(
            x509.BasicConstraints(ca=True, path_length=None),
            critical=True,
        )

        builder = builder.add_extension(
            x509.SubjectKeyIdentifier.from_public_key(self.ca_public_key),
            critical=False,
        )

        builder = builder.add_extension(
            x509.AuthorityKeyIdentifier.from_issuer_public_key(
                 self.ca_public_key
                 ),
            critical=False,
        )

        cert = builder.sign(self.ca_key, hashes.SHA256(), default_backend())

        return cert.public_bytes(serialization.Encoding.PEM)

    def sign_csr(self, ipa_csr, path_length=1):
        """Sign certificate CSR.

        :param ipa_csr: CSR in PEM format.
        :type ipa_csr: bytes.
        :returns: bytes -- Signed CA in PEM format.
        """
        csr_tbs = x509.load_pem_x509_csr(ipa_csr, default_backend())

        csr_public_key = csr_tbs.public_key()
        csr_subject = csr_tbs.subject

        builder = x509.CertificateBuilder()
        builder = builder.public_key(csr_public_key)
        builder = builder.subject_name(csr_subject)
        builder = builder.serial_number(x509.random_serial_number())
        builder = builder.issuer_name(self.issuer)
        builder = builder.not_valid_before(self.now)
        builder = builder.not_valid_after(self.now + self.delta)

        builder = builder.add_extension(
            x509.KeyUsage(
                digital_signature=False,
                content_commitment=False,
                key_encipherment=False,
                data_encipherment=False,
                key_agreement=False,
                key_cert_sign=True,
                crl_sign=True,
                encipher_only=False,
                decipher_only=False,
            ),
            critical=True,
        )

        builder = builder.add_extension(
            x509.SubjectKeyIdentifier.from_public_key(csr_public_key),
            critical=False,
        )

        builder = builder.add_extension(
            x509.AuthorityKeyIdentifier.from_issuer_public_key(
                 self.ca_public_key
                 ),
            critical=False,
        )

        builder = builder.add_extension(
            x509.BasicConstraints(ca=True, path_length=path_length),
            critical=True,
        )

        cert = builder.sign(
            private_key=self.ca_key,
            algorithm=hashes.SHA256(),
            backend=default_backend(),
        )

        return cert.public_bytes(serialization.Encoding.PEM)


def main():
    IPA_CSR = '/root/ipa.csr'
    ROOT_CA = '/tmp/rootca.pem'
    IPA_CA = '/tmp/ipaca.pem'
    parser = argparse.ArgumentParser("Create external CA")
    parser.add_argument(
        '--csr', type=argparse.FileType('rb'), default=IPA_CSR,
        help="Path to ipa.csr (default: {})".format(IPA_CSR)
    )
    parser.add_argument(
        '--rootca', type=argparse.FileType('wb'), default=ROOT_CA,
        help="New root CA file (default: {})".format(ROOT_CA)
    )
    parser.add_argument(
        '--ipaca', type=argparse.FileType('wb'), default=IPA_CA,
        help="New IPA CA file (default: {})".format(ROOT_CA)
    )

    args = parser.parse_args()

    with args.csr as f:
        ipa_csr = f.read()

    external_ca = ExternalCA()
    root_ca = external_ca.create_ca()
    ipa_ca = external_ca.sign_csr(ipa_csr)

    with args.rootca as f:
        f.write(root_ca)

    with args.ipaca as f:
        f.write(ipa_ca)

    o = "ipa-server-install --external-cert-file={} --external-cert-file={}"
    print(o.format(args.rootca.name, args.ipaca.name))


if __name__ == '__main__':
    main()
