#!/bin/bash

#set -x
usage() {
  printf "Usage:\n"
  printf "Create VPN     : %s -c -r <ip range for clients> -l <localip> -p <ipsec psk> -s <public ip> \n" $(basename $0)
  printf "Delete VPN     : %s -d -s <public ip>\n" $(basename $0)
  printf "Add VPN User   : %s -u <username,password> \n" $(basename $0)
  printf "Remote VPN User: %s -U <username \n" $(basename $0)
}

get_intf_ip() {
  ip addr show $1 | grep -w inet | awk '{print $2}' | awk -F'/' '{print $1}'
}


iptables_() {
   local op=$1
   local public_ip=$2
   local public_if="eth2"
   local subnet_if="eth0"
   local subnet_ip=$(get_intf_ip $subnet_if)

   iptables $op INPUT -i $public_if --dst $public_ip -p udp -m udp --dport 500 -j ACCEPT
   iptables $op INPUT -i $public_if --dst $public_ip -p udp -m udp --dport 4500 -j ACCEPT
   iptables $op INPUT -i $public_if --dst $public_ip -p udp -m udp --dport 1701 -j ACCEPT
   iptables $op INPUT -i eth2 -p ah -j ACCEPT
   iptables $op INPUT -i eth2 -p esp -j ACCEPT
   iptables $op FORWARD -i ppp+ -o $subnet_if -j ACCEPT 
   iptables $op FORWARD -i $subnet_if -o ppp+ -j ACCEPT 
   iptables $op FORWARD -i ppp+ -o ppp+ -j ACCEPT 
   iptables $op INPUT -i ppp+ -m udp -p udp --dport 53 -j ACCEPT


   iptables -t nat $op PREROUTING -i ppp+ -p udp -m udp --dport 53 -j  DNAT --to-destination $subnet_ip
   
}

ipsec_server() {
   local op=$1
   if [ "$op" == "restart" ]; then
     service ipsec stop
     service xl2tpd stop
     service ipsec start
     service xl2tpd start
     return $?
   fi
   service ipsec $op
   service xl2tpd $op
}

create_l2tp_ipsec_vpn_server() {
   local ipsec_psk=$1
   local public_ip=$2
   local client_range=$3
   local local_ip=$4

   sed -i -e "s/left=.*$/left=$public_ip/" /etc/ipsec.d/l2tp.conf
   echo ": PSK \"$ipsec_psk\"" > /etc/ipsec.d/ipsec.any.secrets
   sed -i -e "s/^ip range = .*$/ip range = $client_range/"  /etc/xl2tpd/xl2tpd.conf
   sed -i -e "s/^local ip = .*$/local ip = $local_ip/"  /etc/xl2tpd/xl2tpd.conf

   sed -i -e "s/^ms-dns.*$/ms-dns $local_ip/" /etc/ppp/options.xl2tpd

   iptables_ "-D" $public_ip
   iptables_ "-I" $public_ip

   ipsec_server "restart"

   ipsec auto --rereadsecrets 
   ipsec auto --replace L2TP-PSK
}

destroy_l2tp_ipsec_vpn_server() {
   local public_ip=$1

   ipsec auto --down L2TP-PSK

   iptables_ "-D" $public_ip
   
   ipsec_server "stop"
}

remove_l2tp_ipsec_user() {
   local u=$1
   sed -i -e "/^$u .*$/d" /etc/ppp/chap-secrets
   if [ -x /usr/bin/tdbdump ]; then
      pid=$(tdbdump /var/run/pppd2.tdb | grep -w $u | awk -F';' '{print $4}' | awk -F= '{print $2}')
      [ "$pid" != "" ] && kill -9 $pid
   fi
   return 0
}

add_l2tp_ipsec_user() {
   local u=$1
   local passwd=$2

   remove_l2tp_ipsec_user $u
   echo "$u * $passwd *" >> /etc/ppp/chap-secrets
}

rflag=
pflag=
lflag=
sflag=
create=
destroy=
useradd=
userdel=

while getopts 'cdl:p:r:s:u:U:' OPTION
do
  case $OPTION in
  c)	create=1
		;;
  d)	destroy=1
		;;
  u)	useradd=1
		user_pwd="$OPTARG"
		;;
  U)	userdel=1
		user="$OPTARG"
		;;
  r)	rflag=1
		client_range="$OPTARG"
		;;
  p)	pflag=1
		ipsec_psk="$OPTARG"
		;;
  l)	lflag=1
		local_ip="$OPTARG"
		;;
  s)	sflag=1
		server_ip="$OPTARG"
		;;
  ?)	usage
		exit 2
		;;
  esac
done

[ "$create$destroy" == "11" ] || [ "$create$destroy$useradd$userdel" == "" ] && usage && exit 2
[ "$create" == "1" ] && [ "$lflag$pflag$rflag$sflag" != "1111" ] && usage && exit 2

if [ "$create" == "1" ]; then
    create_l2tp_ipsec_vpn_server $ipsec_psk $server_ip $client_range $local_ip
    exit $?
fi

if [ "$destroy" == "1" ]; then
   destroy_l2tp_ipsec_vpn_server $server_ip
   exit $?
fi

if [ "$useradd" == "1" ]; then
   u=$(echo $user_pwd | awk -F',' '{print $1}')
   pwd=$(echo $user_pwd | awk -F',' '{print $2}')
   add_l2tp_ipsec_user $u $pwd
   exit $?
fi
if [ "$userdel" == "1" ]; then
   remove_l2tp_ipsec_user $user 
   exit $?
fi