#!/usr/bin/env python3
#
# Copyright VyOS maintainers and contributors <maintainers@vyos.io>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# 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/>.

import os
from sys import exit

from vyos.base import Warning
from vyos.config import Config
from vyos.configverify import verify_pki_certificate
from vyos.configverify import verify_pki_ca_certificate
from vyos.pki import find_chain
from vyos.pki import encode_certificate
from vyos.pki import load_certificate
from vyos.pki import wrap_private_key
from vyos.template import render
from vyos.utils.dict import dict_search
from vyos.utils.file import write_file
from vyos.utils.network import check_port_availability
from vyos.utils.network import is_listen_port_bind_service
from vyos.utils.process import call
from vyos.utils.process import is_systemd_service_running
from vyos import ConfigError
from passlib.hash import sha512_crypt
from time import sleep

from vyos import airbag

airbag.enable()

cfg_dir = '/run/ocserv'
ocserv_conf = cfg_dir + '/ocserv.conf'
ocserv_passwd = cfg_dir + '/ocpasswd'
ocserv_otp_usr = cfg_dir + '/users.oath'
radius_cfg = cfg_dir + '/radiusclient.conf'
radius_servers = cfg_dir + '/radius_servers'


# Generate hash from user cleartext password
def get_hash(password):
    return sha512_crypt.hash(password)


def get_config(config=None):
    if config:
        conf = config
    else:
        conf = Config()
    base = ['vpn', 'openconnect']
    if not conf.exists(base):
        return None

    ocserv = conf.get_config_dict(
        base,
        key_mangling=('-', '_'),
        get_first_key=True,
        with_recursive_defaults=True,
        with_pki=True,
    )

    return ocserv


def verify(ocserv):
    if ocserv is None:
        return None
    # Check if listen-ports not binded other services
    # It can be only listen by 'ocserv-main'
    for proto, port in ocserv.get('listen_ports').items():
        if check_port_availability(
            ocserv['listen_address'], int(port), proto
        ) is not True and not is_listen_port_bind_service(int(port), 'ocserv-main'):
            raise ConfigError(f'"{proto}" port "{port}" is used by another service')

    # Check accounting
    if 'accounting' in ocserv:
        if 'mode' in ocserv['accounting'] and 'radius' in ocserv['accounting']['mode']:
            if not ocserv['accounting']['radius']['server']:
                raise ConfigError(
                    'OpenConnect accounting mode radius requires at least one RADIUS server'
                )
            if 'authentication' not in ocserv or 'mode' not in ocserv['authentication']:
                raise ConfigError(
                    'Accounting depends on OpenConnect authentication configuration'
                )
            elif 'radius' not in ocserv['authentication']['mode']:
                raise ConfigError(
                    'RADIUS accounting must be used with RADIUS authentication'
                )

    # Check authentication
    if 'authentication' in ocserv:
        if 'mode' in ocserv['authentication']:
            if (
                'local' in ocserv['authentication']['mode']
                and 'radius' in ocserv['authentication']['mode']
            ):
                raise ConfigError(
                    'OpenConnect authentication modes are mutually-exclusive, remove either local or radius from your configuration'
                )
            if 'radius' in ocserv['authentication']['mode']:
                if 'server' not in ocserv['authentication']['radius']:
                    raise ConfigError(
                        'OpenConnect authentication mode radius requires at least one RADIUS server'
                    )
            if 'local' in ocserv['authentication']['mode']:
                if not ocserv.get('authentication', {}).get('local_users'):
                    raise ConfigError(
                        'OpenConnect mode local required at least one user'
                    )
                if not ocserv['authentication']['local_users']['username']:
                    raise ConfigError(
                        'OpenConnect mode local required at least one user'
                    )
                else:
                    # For OTP mode: verify that each local user has an OTP key
                    if 'otp' in ocserv['authentication']['mode']['local']:
                        users_wo_key = []
                        for user, user_config in ocserv['authentication'][
                            'local_users'
                        ]['username'].items():
                            # User has no OTP key defined
                            if dict_search('otp.key', user_config) is None:
                                users_wo_key.append(user)
                        if users_wo_key:
                            raise ConfigError(
                                f'OTP enabled, but no OTP key is configured for these users:\n{users_wo_key}'
                            )
                    # For password (and default) mode: verify that each local user has password
                    if (
                        'password' in ocserv['authentication']['mode']['local']
                        or 'otp' not in ocserv['authentication']['mode']['local']
                    ):
                        users_wo_pswd = []
                        for user in ocserv['authentication']['local_users']['username']:
                            if (
                                'password'
                                not in ocserv['authentication']['local_users'][
                                    'username'
                                ][user]
                            ):
                                users_wo_pswd.append(user)
                        if users_wo_pswd:
                            raise ConfigError(
                                f'password required for users:\n{users_wo_pswd}'
                            )

            # Validate that if identity-based-config is configured all child config nodes are set
            if 'identity_based_config' in ocserv['authentication']:
                if 'disabled' not in ocserv['authentication']['identity_based_config']:
                    Warning(
                        'Identity based configuration files is a 3rd party addition. Use at your own risk, this might break the ocserv daemon!'
                    )
                    if 'mode' not in ocserv['authentication']['identity_based_config']:
                        raise ConfigError(
                            'OpenConnect radius identity-based-config enabled but mode not selected'
                        )
                    elif (
                        'group'
                        in ocserv['authentication']['identity_based_config']['mode']
                        and 'radius' not in ocserv['authentication']['mode']
                    ):
                        raise ConfigError(
                            'OpenConnect config-per-group must be used with radius authentication'
                        )
                    if (
                        'directory'
                        not in ocserv['authentication']['identity_based_config']
                    ):
                        raise ConfigError(
                            'OpenConnect identity-based-config enabled but directory not set'
                        )
                    if (
                        'default_config'
                        not in ocserv['authentication']['identity_based_config']
                    ):
                        raise ConfigError(
                            'OpenConnect identity-based-config enabled but default-config not set'
                        )
        else:
            raise ConfigError('OpenConnect authentication mode required')
    else:
        raise ConfigError('OpenConnect authentication credentials required')

    # Check ssl
    if 'ssl' not in ocserv:
        raise ConfigError('SSL missing on OpenConnect config!')

    if 'certificate' not in ocserv['ssl']:
        raise ConfigError('SSL certificate missing on OpenConnect config!')
    verify_pki_certificate(ocserv, ocserv['ssl']['certificate'])

    if 'ca_certificate' in ocserv['ssl']:
        for ca_cert in ocserv['ssl']['ca_certificate']:
            verify_pki_ca_certificate(ocserv, ca_cert)

    # Check network settings
    if 'network_settings' in ocserv:
        if 'push_route' in ocserv['network_settings']:
            # Replace default route
            if '0.0.0.0/0' in ocserv['network_settings']['push_route']:
                ocserv['network_settings']['push_route'].remove('0.0.0.0/0')
                ocserv['network_settings']['push_route'].append('default')
        else:
            ocserv['network_settings']['push_route'] = ['default']
    else:
        raise ConfigError('OpenConnect network settings required!')


def generate(ocserv):
    if not ocserv:
        return None

    if 'radius' in ocserv['authentication']['mode']:
        if dict_search(ocserv, 'accounting.mode.radius'):
            # Render radius client configuration
            render(radius_cfg, 'ocserv/radius_conf.j2', ocserv)
            merged_servers = (
                ocserv['accounting']['radius']['server']
                | ocserv['authentication']['radius']['server']
            )
            # Render radius servers
            # Merge the accounting and authentication servers into a single dictionary
            render(
                radius_servers, 'ocserv/radius_servers.j2', {'server': merged_servers}
            )
        else:
            # Render radius client configuration
            render(radius_cfg, 'ocserv/radius_conf.j2', ocserv)
            # Render radius servers
            render(
                radius_servers,
                'ocserv/radius_servers.j2',
                ocserv['authentication']['radius'],
            )
    elif 'local' in ocserv['authentication']['mode']:
        # if mode "OTP", generate OTP users file parameters
        if 'otp' in ocserv['authentication']['mode']['local']:
            if 'local_users' in ocserv['authentication']:
                for user in ocserv['authentication']['local_users']['username']:
                    # OTP token type from CLI parameters:
                    otp_interval = str(
                        ocserv['authentication']['local_users']['username'][user][
                            'otp'
                        ].get('interval')
                    )
                    token_type = ocserv['authentication']['local_users']['username'][
                        user
                    ]['otp'].get('token_type')
                    otp_length = str(
                        ocserv['authentication']['local_users']['username'][user][
                            'otp'
                        ].get('otp_length')
                    )
                    if token_type == 'hotp-time':
                        otp_type = 'HOTP/T' + otp_interval
                    elif token_type == 'hotp-event':
                        otp_type = 'HOTP/E'
                    else:
                        otp_type = 'HOTP/T' + otp_interval
                    ocserv['authentication']['local_users']['username'][user]['otp'][
                        'token_tmpl'
                    ] = otp_type + '/' + otp_length
        # if there is a password, generate hash
        if (
            'password' in ocserv['authentication']['mode']['local']
            or 'otp' not in ocserv['authentication']['mode']['local']
        ):
            if 'local_users' in ocserv['authentication']:
                for user in ocserv['authentication']['local_users']['username']:
                    ocserv['authentication']['local_users']['username'][user][
                        'hash'
                    ] = get_hash(
                        ocserv['authentication']['local_users']['username'][user][
                            'password'
                        ]
                    )

        if 'password-otp' in ocserv['authentication']['mode']['local']:
            # Render local users ocpasswd
            render(
                ocserv_passwd,
                'ocserv/ocserv_passwd.j2',
                ocserv['authentication']['local_users'],
            )
            # Render local users OTP keys
            render(
                ocserv_otp_usr,
                'ocserv/ocserv_otp_usr.j2',
                ocserv['authentication']['local_users'],
            )
        elif 'password' in ocserv['authentication']['mode']['local']:
            # Render local users ocpasswd
            render(
                ocserv_passwd,
                'ocserv/ocserv_passwd.j2',
                ocserv['authentication']['local_users'],
            )
        elif 'otp' in ocserv['authentication']['mode']['local']:
            # Render local users OTP keys
            render(
                ocserv_otp_usr,
                'ocserv/ocserv_otp_usr.j2',
                ocserv['authentication']['local_users'],
            )
        else:
            # Render local users ocpasswd
            render(
                ocserv_passwd,
                'ocserv/ocserv_passwd.j2',
                ocserv['authentication']['local_users'],
            )
    else:
        if 'local_users' in ocserv['authentication']:
            for user in ocserv['authentication']['local_users']['username']:
                ocserv['authentication']['local_users']['username'][user]['hash'] = (
                    get_hash(
                        ocserv['authentication']['local_users']['username'][user][
                            'password'
                        ]
                    )
                )
            # Render local users
            render(
                ocserv_passwd,
                'ocserv/ocserv_passwd.j2',
                ocserv['authentication']['local_users'],
            )

    if 'ssl' in ocserv:
        cert_file_path = os.path.join(cfg_dir, 'cert.pem')
        cert_key_path = os.path.join(cfg_dir, 'cert.key')

        if 'certificate' in ocserv['ssl']:
            cert_name = ocserv['ssl']['certificate']
            pki_cert = ocserv['pki']['certificate'][cert_name]

            loaded_pki_cert = load_certificate(pki_cert['certificate'])
            loaded_ca_certs = (
                {
                    load_certificate(c['certificate'])
                    for c in ocserv['pki']['ca'].values()
                }
                if 'ca' in ocserv['pki']
                else {}
            )

            cert_full_chain = find_chain(loaded_pki_cert, loaded_ca_certs)

            write_file(
                cert_file_path,
                '\n'.join(encode_certificate(c) for c in cert_full_chain),
            )

            if 'private' in pki_cert and 'key' in pki_cert['private']:
                write_file(cert_key_path, wrap_private_key(pki_cert['private']['key']))

        if 'ca_certificate' in ocserv['ssl']:
            ca_cert_file_path = os.path.join(cfg_dir, 'ca.pem')
            ca_chains = []

            for ca_name in ocserv['ssl']['ca_certificate']:
                pki_ca_cert = ocserv['pki']['ca'][ca_name]
                loaded_ca_cert = load_certificate(pki_ca_cert['certificate'])
                ca_full_chain = find_chain(loaded_ca_cert, loaded_ca_certs)
                ca_chains.append(
                    '\n'.join(encode_certificate(c) for c in ca_full_chain)
                )

            write_file(ca_cert_file_path, '\n'.join(ca_chains))

    # Render config
    render(ocserv_conf, 'ocserv/ocserv_config.j2', ocserv)


def apply(ocserv):
    if not ocserv:
        call('systemctl stop ocserv.service')
        for file in [ocserv_conf, ocserv_passwd, ocserv_otp_usr]:
            if os.path.exists(file):
                os.unlink(file)
    else:
        call('systemctl reload-or-restart ocserv.service')
        counter = 0
        while True:
            # exit early when service runs
            if is_systemd_service_running('ocserv.service'):
                break
            sleep(0.250)
            if counter > 5:
                raise ConfigError(
                    'OpenConnect failed to start, check the logs for details'
                )
                break
            counter += 1


if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)