#!/usr/bin/env python3
#
# Copyright (C) 2018-2020 VyOS maintainers and contributors
#
# 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 re
import os

from time import sleep

# Top level import so that configd can override it
from sys import argv

from vyos.config import Config
from vyos import ConfigError
from vyos.util import call, wait_for_file_write_complete
from vyos.template import render

from vyos import airbag
airbag.enable()

ra_conn_name = "remote-access"
charon_conf_file = "/etc/strongswan.d/charon.conf"
ipsec_secrets_file = "/etc/ipsec.secrets"
ipsec_ra_conn_dir = "/etc/ipsec.d/tunnels/"
ipsec_ra_conn_file = ipsec_ra_conn_dir + ra_conn_name
ipsec_conf_file = "/etc/ipsec.conf"
ca_cert_path = "/etc/ipsec.d/cacerts"
server_cert_path = "/etc/ipsec.d/certs"
server_key_path = "/etc/ipsec.d/private"
delim_ipsec_l2tp_begin = "### VyOS L2TP VPN Begin ###"
delim_ipsec_l2tp_end = "### VyOS L2TP VPN End ###"
charon_pidfile = "/var/run/charon.pid"

def get_config(config=None):
    if config:
        config = config
    else:
        config = Config()

    # IPsec isn't configured enough to warrant starting StrongSWAN for it,
    # it's just some incomplete or leftover options.
    if not (config.exists("vpn ipsec site-to-site peer") or \
       config.exists("vpn ipsec profile") or \
       config.exists("vpn l2tp remote-access ipsec-settings")):
        return {}

    data = {"install_routes": "yes"}

    if config.exists("vpn ipsec options disable-route-autoinstall"):
        data["install_routes"] = "no"

    if config.exists("vpn ipsec ipsec-interfaces interface"):
        data["ipsec_interfaces"] = config.return_values("vpn ipsec ipsec-interfaces interface")

    # Init config variables
    data["delim_ipsec_l2tp_begin"] = delim_ipsec_l2tp_begin
    data["delim_ipsec_l2tp_end"] = delim_ipsec_l2tp_end
    data["ipsec_ra_conn_file"] = ipsec_ra_conn_file
    data["ra_conn_name"] = ra_conn_name
    # Get l2tp ipsec settings
    data["ipsec_l2tp"] = False
    conf_ipsec_command = "vpn l2tp remote-access ipsec-settings " #last space is useful
    if config.exists(conf_ipsec_command):
        data["ipsec_l2tp"] = True

        # Authentication params
        if config.exists(conf_ipsec_command + "authentication mode"):
            data["ipsec_l2tp_auth_mode"] = config.return_value(conf_ipsec_command + "authentication mode")
        if config.exists(conf_ipsec_command + "authentication pre-shared-secret"):
            data["ipsec_l2tp_secret"] = config.return_value(conf_ipsec_command + "authentication pre-shared-secret")

        # mode x509
        if config.exists(conf_ipsec_command + "authentication x509 ca-cert-file"):
            data["ipsec_l2tp_x509_ca_cert_file"] = config.return_value(conf_ipsec_command + "authentication x509 ca-cert-file")
        if config.exists(conf_ipsec_command + "authentication x509 crl-file"):
            data["ipsec_l2tp_x509_crl_file"] = config.return_value(conf_ipsec_command + "authentication x509 crl-file")
        if config.exists(conf_ipsec_command + "authentication x509 server-cert-file"):
            data["ipsec_l2tp_x509_server_cert_file"] = config.return_value(conf_ipsec_command + "authentication x509 server-cert-file")
            data["server_cert_file_copied"] = server_cert_path+"/"+re.search('\w+(?:\.\w+)*$', config.return_value(conf_ipsec_command + "authentication x509 server-cert-file")).group(0)
        if config.exists(conf_ipsec_command + "authentication x509 server-key-file"):
            data["ipsec_l2tp_x509_server_key_file"] = config.return_value(conf_ipsec_command + "authentication x509 server-key-file")
            data["server_key_file_copied"] = server_key_path+"/"+re.search('\w+(?:\.\w+)*$', config.return_value(conf_ipsec_command + "authentication x509 server-key-file")).group(0)
        if config.exists(conf_ipsec_command + "authentication x509 server-key-password"):
            data["ipsec_l2tp_x509_server_key_password"] = config.return_value(conf_ipsec_command + "authentication x509 server-key-password")

        # Common l2tp ipsec params
        if config.exists(conf_ipsec_command + "ike-lifetime"):
            data["ipsec_l2tp_ike_lifetime"] = config.return_value(conf_ipsec_command + "ike-lifetime")
        else:
            data["ipsec_l2tp_ike_lifetime"] = "3600"

        if config.exists(conf_ipsec_command + "lifetime"):
            data["ipsec_l2tp_lifetime"] = config.return_value(conf_ipsec_command + "lifetime")
        else:
            data["ipsec_l2tp_lifetime"] = "3600"

    if config.exists("vpn l2tp remote-access outside-address"):
        data['outside_addr'] = config.return_value('vpn l2tp remote-access outside-address')

    return data

def write_ipsec_secrets(c):
    if c.get("ipsec_l2tp_auth_mode") == "pre-shared-secret":
        secret_txt = "{0}\n{1} %any : PSK \"{2}\"\n{3}\n".format(delim_ipsec_l2tp_begin, c['outside_addr'], c['ipsec_l2tp_secret'], delim_ipsec_l2tp_end)
    elif c.get("ipsec_l2tp_auth_mode") == "x509":
        secret_txt = "{0}\n: RSA {1}\n{2}\n".format(delim_ipsec_l2tp_begin, c['server_key_file_copied'], delim_ipsec_l2tp_end)

    old_umask = os.umask(0o077)
    with open(ipsec_secrets_file, 'a+') as f:
        f.write(secret_txt)
    os.umask(old_umask)

def write_ipsec_conf(c):
    ipsec_confg_txt = "{0}\ninclude {1}\n{2}\n".format(delim_ipsec_l2tp_begin, ipsec_ra_conn_file, delim_ipsec_l2tp_end)

    old_umask = os.umask(0o077)
    with open(ipsec_conf_file, 'a+') as f:
        f.write(ipsec_confg_txt)
    os.umask(old_umask)

### Remove config from file by delimiter
def remove_confs(delim_begin, delim_end, conf_file):
    call("sed -i '/"+delim_begin+"/,/"+delim_end+"/d' "+conf_file)


### Checking certificate storage and notice if certificate not in /config directory
def check_cert_file_store(cert_name, file_path, dts_path):
    if not re.search('^\/config\/.+', file_path):
        print("Warning: \"" + file_path + "\" lies outside of /config/auth directory. It will not get preserved during image upgrade.")
    #Checking file existence
    if not os.path.isfile(file_path):
      raise ConfigError("L2TP VPN configuration error: Invalid "+cert_name+" \""+file_path+"\"")
    else:
      ### Cpy file to /etc/ipsec.d/certs/ /etc/ipsec.d/cacerts/
      # todo make check
      ret = call('cp -f '+file_path+' '+dts_path)
      if ret:
         raise ConfigError("L2TP VPN configuration error: Cannot copy "+file_path)

def verify(data):
    if not data:
        return

    # l2tp ipsec check
    if data["ipsec_l2tp"]:
        # Checking dependecies for "authentication mode pre-shared-secret"
        if data.get("ipsec_l2tp_auth_mode") == "pre-shared-secret":
            if not data.get("ipsec_l2tp_secret"):
                raise ConfigError("pre-shared-secret required")
            if not data.get("outside_addr"):
                raise ConfigError("outside-address not defined")

        # Checking dependecies for "authentication mode x509"
        if data.get("ipsec_l2tp_auth_mode") == "x509":
            if not data.get("ipsec_l2tp_x509_server_key_file"):
                raise ConfigError("L2TP VPN configuration error: \"server-key-file\" not defined.")
            else:
                check_cert_file_store("server-key-file", data['ipsec_l2tp_x509_server_key_file'], server_key_path)

            if not data.get("ipsec_l2tp_x509_server_cert_file"):
                raise ConfigError("L2TP VPN configuration error: \"server-cert-file\" not defined.")
            else:
                check_cert_file_store("server-cert-file", data['ipsec_l2tp_x509_server_cert_file'], server_cert_path)

            if not data.get("ipsec_l2tp_x509_ca_cert_file"):
                raise ConfigError("L2TP VPN configuration error: \"ca-cert-file\" must be defined for X.509")
            else:
                check_cert_file_store("ca-cert-file", data['ipsec_l2tp_x509_ca_cert_file'], ca_cert_path)

        if not data.get('ipsec_interfaces'):
           raise ConfigError("L2TP VPN configuration error: \"vpn ipsec ipsec-interfaces\" must be specified.")

def generate(data):
    if not data:
        return

    render(charon_conf_file, 'ipsec/charon.tmpl', data)

    if data["ipsec_l2tp"]:
        remove_confs(delim_ipsec_l2tp_begin, delim_ipsec_l2tp_end, ipsec_secrets_file)
        # old_umask = os.umask(0o077)
        # render(ipsec_secrets_file, 'ipsec/ipsec.secrets.tmpl', data)
        # os.umask(old_umask)
        ## Use this method while IPSec CLI handler won't be overwritten to python
        write_ipsec_secrets(data)

        old_umask = os.umask(0o077)

        # Create tunnels directory if does not exist
        if not os.path.exists(ipsec_ra_conn_dir):
            os.makedirs(ipsec_ra_conn_dir)

        render(ipsec_ra_conn_file, 'ipsec/remote-access.tmpl', data)
        os.umask(old_umask)

        remove_confs(delim_ipsec_l2tp_begin, delim_ipsec_l2tp_end, ipsec_conf_file)
        # old_umask = os.umask(0o077)
        # render(ipsec_conf_file, 'ipsec/ipsec.conf.tmpl', data)
        # os.umask(old_umask)
        ## Use this method while IPSec CLI handler won't be overwritten to python
        write_ipsec_conf(data)

    else:
        if os.path.exists(ipsec_ra_conn_file):
            remove_confs(delim_ipsec_l2tp_begin, delim_ipsec_l2tp_end, ipsec_ra_conn_file)
        remove_confs(delim_ipsec_l2tp_begin, delim_ipsec_l2tp_end, ipsec_secrets_file)
        remove_confs(delim_ipsec_l2tp_begin, delim_ipsec_l2tp_end, ipsec_conf_file)

def is_charon_responsive():
    # Check if charon responds to strokes
    #
    # Sometimes it takes time to fully initialize,
    # so waiting for the process to come to live isn't always enough
    #
    # There's no official "no-op" stroke so we use the "memusage" stroke as a substitute
    from os import system
    res = system("ipsec stroke memusage >&/dev/null")
    if res == 0:
        return True
    else:
        return False

def restart_ipsec():
    try:
        # Restart the IPsec daemon when it's running.
        # Since it's started by the legacy ipsec.pl in VyOS 1.3,
        # there's a chance that this script will run before charon is up,
        # so we can't assume it's running and have to check and wait if needed.

        # But before everything else, there's a catch!
        # This script is run from _two_ places: "vpn ipsec options" and the top level "vpn" node
        # When IPsec isn't set up yet, and a user wants to commit an IPsec config with some
        # "vpn ipsec settings", this script will first be called before StrongSWAN is started by vpn-config.pl!
        # Thus if this script is run from "settings" _and_ charon is unresponsive,
        # we shouldn't wait for it, else there will be a deadlock.
        # We indicate that by running the script under vyshim from "vpn ipsec options" (which sets a variable named "argv")
        # and running it without configd from "vpn ipsec"
        if "from-options" in argv:
            if not is_charon_responsive():
                return

        # If we got this far, then we actually need to restart StrongSWAN

        # First, wait for charon to get started by the old vpn-config.pl script.
        from time import sleep, time
        from os import system
        now = time()
        while True:
            if (time() - now) > 60:
                raise OSError("Timeout waiting for the IPsec process to become responsive")
            if is_charon_responsive():
                break
            sleep(5)

        # Force configuration load
        call('swanctl -q >&/dev/null')

    except OSError:
        raise ConfigError('VPN configuration error: IPSec process did not start.')

def apply(data):
    if data:
        restart_ipsec()
    else:
        print("Note: the IPsec process will not start until you configure some tunnels, profiles, or L2TP/IPsec settings")

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