#!/usr/bin/env python3
#
# Copyright (C) 2018 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/>.
#
#
#### TODO:
# fwmark
# preshared key
# mtu
####


import sys
import os
import re
import syslog as sl
import subprocess

from vyos.config import Config
from vyos import ConfigError

dir = r'/config/auth/wireguard'
pk  = dir + '/private.key'
pub = dir + '/public.key'

### check_kmod may be removed in the future, 
### just want to have everything smoothly running after reboot
def check_kmod():
  if not os.path.exists('/sys/module/wireguard'):
    sl.syslog(sl.LOG_NOTICE, "loading wirguard kmod") 
    if  os.system('sudo modprobe wireguard') != 0:
      sl.syslog(sl.LOG_NOTICE, "modprobe wireguard failed")
      raise ConfigError("modprobe wireguard failed")

def get_config():
  config_data = {
    'interfaces' : {}
  }

  c = Config()
  if not c.exists('interfaces wireguard'):
    return None
  
  c.set_level('interfaces') 
  intfcs = c.list_nodes('wireguard')
  intfcs_eff = c.list_effective_nodes('wireguard')
  new_lst = list( set(intfcs) - set(intfcs_eff) ) 
  del_lst = list( set(intfcs_eff) - set(intfcs) )

  ### setting deafult and determine status of the config 
  for intfc in intfcs:
    cnf = 'wireguard ' + intfc
    # default data struct
    config_data['interfaces'].update (
      {
        intfc : {
          'addr'        : '',
          'descr'       : intfc, ## snmp ifAlias
          'lport'       : '',
          'status'      : 'exists',
          'state'       : 'enabled',
          'mtu'         : 1420,
          'peer'        : {},
          'fwmark'      : 0
          }
        }
    ) 

  for i in new_lst:
    config_data['interfaces'][i]['status'] = 'create' 

  for i in del_lst:
    config_data['interfaces'].update (
      {
        i : {
          'status': 'delete'
        }
      }
    )

  ### based on the status, set real values
  for intfc in intfcs:
    cnf = 'wireguard ' + intfc
    if config_data['interfaces'][intfc]['status'] != 'delete':
      #### addresses
      if c.exists(cnf + ' address'):
        config_data['interfaces'][intfc]['addr'] = c.return_values(cnf + ' address')
      ### listen port
      if c.exists(cnf + ' listen-port'):
        config_data['interfaces'][intfc]['lport'] = c.return_value(cnf + ' listen-port')
      ### description
      if c.exists(cnf + ' description'):
        config_data['interfaces'][intfc]['descr'] = c.return_value(cnf + ' description')
      ### mtu
      if c.exists(cnf + ' mtu'):
        config_data['interfaces'][intfc]['mtu'] = c.return_value(cnf + ' mtu')
      ### fwmark
      if c.exists(cnf + ' fwmark'):
        config_data['interfaces'][intfc]['fwmark'] = c.return_value(cnf + ' fwmark')
      
      ### peers
      if c.exists(cnf + ' peer'):
        for p in c.list_nodes(cnf + ' peer'):
          config_data['interfaces'][intfc]['peer'].update  (
            {
              p : {
                'allowed-ips' : [],
                'endpoint'  : '',
                'pubkey'  : ''
              }
            }
          )
          if c.exists(cnf + ' peer ' + p + ' pubkey'):
            config_data['interfaces'][intfc]['peer'][p]['pubkey'] = c.return_value(cnf + ' peer ' + p + ' pubkey')
          if c.exists(cnf + ' peer ' + p + ' allowed-ips'):
            config_data['interfaces'][intfc]['peer'][p]['allowed-ips'] = c.return_values(cnf + ' peer ' + p + ' allowed-ips')
          if c.exists(cnf + ' peer ' + p + ' endpoint'):
            config_data['interfaces'][intfc]['peer'][p]['endpoint'] = c.return_value(cnf + ' peer ' + p + ' endpoint')
          if c.exists(cnf + ' peer ' + p + ' persistent-keepalive'):
            config_data['interfaces'][intfc]['peer'][p]['persistent-keepalive'] = c.return_value(cnf + ' peer ' + p + ' persistent-keepalive')

  return config_data

def verify(c):
  if not c:
    return None

  for i in c['interfaces']:
    if c['interfaces'][i]['status'] != 'delete':
      if not c['interfaces'][i]['addr']:
        raise ConfigError("address required for interface " + i) 
      if not c['interfaces'][i]['peer']:
        raise ConfigError("peer required on interface " + i)
      else:
        for p in c['interfaces'][i]['peer']:
          if not c['interfaces'][i]['peer'][p]['allowed-ips']:
            raise ConfigError("allowed-ips required on interface " + i + " for peer " + p)
          if not c['interfaces'][i]['peer'][p]['pubkey']:
            raise ConfigError("pubkey from your peer is mandatory on " + i + " for peer " + p)

    ### endpoint needs to be IP:port, mabey verify it here, but consider IPv6 in the pattern :)

def apply(c):
  ### no wg config left, delete all wireguard devices on the os
  if not c:
    net_devs = os.listdir('/sys/class/net/')
    for dev in net_devs:
      buf = open('/sys/class/net/' + dev + '/uevent','r').read()
      if re.search("DEVTYPE=wireguard", buf, re.I|re.M):
        wg_intf = re.sub("INTERFACE=","", re.search("INTERFACE=.*", buf, re.I|re.M).group(0) ) 
        sl.syslog(sl.LOG_NOTICE, "removing interface " + wg_intf)
        subprocess.call(['ip l d dev ' + wg_intf + ' >/dev/null'], shell=True)
    return None
  
  ###
  ## to find the diffs between old config an new config
  ## so we only configure/delete what was not previously configured
  ###
  c_eff = Config()
  c_eff.set_level('interfaces wireguard')

  ### deletion of specific interface
  for intf in c['interfaces']:
    if c['interfaces'][intf]['status'] == 'delete':
      sl.syslog(sl.LOG_NOTICE, "removing interface " + intf)
      subprocess.call(['ip l d dev ' + intf + ' &>/dev/null'], shell=True)

    ### new config
    if c['interfaces'][intf]['status'] == 'create':
      if not os.path.exists(pk):
        raise ConfigError("No keys found, generate them by executing: \'run generate wireguard keypair\'")

      subprocess.call(['ip l a dev ' + intf + ' type wireguard 2>/dev/null'], shell=True)
      for addr in c['interfaces'][intf]['addr']:
        add_addr(intf, addr)
      subprocess.call(['ip l set up dev ' + intf + ' &>/dev/null'], shell=True)
      configure_interface(c,intf)

    ### config updates
    if c['interfaces'][intf]['status'] == 'exists':
      ### IP address change
      addr_eff  = re.sub("\'", "", c_eff.return_effective_values(intf + ' address')).split() 
      addr_rem  = list( set(addr_eff) - set(c['interfaces'][intf]['addr']) )
      addr_add  = list( set(c['interfaces'][intf]['addr']) - set(addr_eff) )

      if len(addr_rem) !=0:
        for addr in addr_rem:
          del_addr(intf, addr)

      if len(addr_add) !=0:
        for addr in addr_add:
          add_addr(intf, addr)

      ### persistent-keepalive
      for p in c_eff.list_nodes(intf + ' peer'):
        val_eff = ""
        val = "" 

        if c_eff.exists_effective(intf + ' peer ' + p + ' persistent-keepalive'):
          val_eff = c_eff.return_effective_value(intf + ' peer ' + p + ' persistent-keepalive')

        if 'persistent-keepalive' in c['interfaces'][intf]['peer'][p]:
          val = c['interfaces'][intf]['peer'][p]['persistent-keepalive']
        
        ### disable keepalive
        if val_eff and not val:
          c['interfaces'][intf]['peer'][p]['persistent-keepalive'] = 0 
        
        ### set new keepalive value
        if not val_eff and val:
          c['interfaces'][intf]['peer'][p]['persistent-keepalive'] = val

      ## wg command call
      configure_interface(c,intf)

    ### ifalias for snmp from description   
    descr_eff = c_eff.return_effective_value(intf + ' description')
    cnf_descr = c['interfaces'][intf]['descr']
    if descr_eff != cnf_descr:
      open('/sys/class/net/' + str(intf) + '/ifalias','w').write(str(cnf_descr))

def configure_interface(c, intf):
  wg_config = {
    'interface'   : intf,
    'listen-port' : 0,
    'private-key' : '/config/auth/wireguard/private.key',
    'peer'        :
      {
        'pubkey'  : ''
      },
    'allowed-ips' : [],
    'fwmark'      : 0x00,
    'endpoint'    : None,
    'keepalive'   : 0

  }

  for p in c['interfaces'][intf]['peer']:
    ## mandatory settings
    wg_config['peer']['pubkey'] = c['interfaces'][intf]['peer'][p]['pubkey']
    wg_config['allowed-ips'] = c['interfaces'][intf]['peer'][p]['allowed-ips']

    ## optional settings
    # listen-port
    if c['interfaces'][intf]['lport']:
      wg_config['listen-port'] = c['interfaces'][intf]['lport']

    ## endpoint
    if c['interfaces'][intf]['peer'][p]['endpoint']:
      wg_config['endpoint'] = c['interfaces'][intf]['peer'][p]['endpoint']

    ## persistent-keepalive
    if 'persistent-keepalive' in c['interfaces'][intf]['peer'][p]:
      wg_config['keepalive']  = c['interfaces'][intf]['peer'][p]['persistent-keepalive']
  
    ## fwmark
    wg_config['fwmark'] = hex(int(c['interfaces'][intf]['fwmark']))

    ### assemble wg command
    cmd = "sudo wg set " + intf
    cmd += " listen-port " + str(wg_config['listen-port'])
    cmd += " fwmark " + wg_config['fwmark'] 
    cmd += " private-key " + wg_config['private-key']
    cmd += " peer " + wg_config['peer']['pubkey']
    cmd += " allowed-ips "
    for ap in wg_config['allowed-ips']:
      if ap != wg_config['allowed-ips'][-1]:
        cmd += ap + ","
      else:
        cmd += ap

    if wg_config['endpoint']:
      cmd += " endpoint " + wg_config['endpoint']

    if wg_config['keepalive'] !=0:
      cmd += " persistent-keepalive " + wg_config['keepalive']
    else:
      cmd += " persistent-keepalive 0"

    sl.syslog(sl.LOG_NOTICE, cmd)
    subprocess.call([cmd], shell=True)

def add_addr(intf, addr):
  ret = subprocess.call(['ip a a dev ' + intf + ' ' + addr + ' &>/dev/null'], shell=True)
  if ret != 0:
    raise ConfigError('Can\'t set IP ' + addr + ' on ' + intf )
  else:
    sl.syslog(sl.LOG_NOTICE, "ip a a dev " + intf + " " + addr)

def del_addr(intf, addr):
  ret = subprocess.call(['ip a d dev ' + intf + ' ' + addr + ' &>/dev/null'], shell=True)
  if ret != 0:
    raise ConfigError('Can\'t delete IP ' + addr + ' on ' + intf )
  else:
    sl.syslog(sl.LOG_NOTICE, "ip a d dev " + intf + " " + addr)

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