amazon vpn script (from https://github.com/sarfata/voodooprivacy/blob/master/voodoo-vpn.sh)

gistfile1.txt

#!/bin/sh
#
# voodoo-vpn.sh: Amazon EC2 user-data file for automatic configuration of a VPN
# on a Ubuntu server instance. Tested with 12.04.
#
# See http://www.sarfata.org/posts/setting-up-an-amazon-vpn-server.md
#
# DO NOT RUN THIS SCRIPT ON YOUR MAC! THIS IS MEANT TO BE RUN WHEN 
# YOUR AMAZON INSTANCE STARTS!
#
# Copyright Thomas Sarlandie 2012
#
# This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 
# Unported License: http://creativecommons.org/licenses/by-sa/3.0/
#
# Attribution required: please include my name in any derivative and let me
# know how you have improved it! 

if [[ "`uname`" == "Darwin" ]]; then
    echo "Do not run this script on your mac! This script should only be run on a newly-created EC2 instance, after you have modified it to set the three variables below."
    exit 1
fi

# Please define your own values for those variables
IPSEC_PSK=very_unsecure_key
VPN_USER=johndoe
VPN_PASSWORD=unsecure

# Those two variables will be found automatically
PRIVATE_IP=`wget -q -O - 'http://169.254.169.254/latest/meta-data/local-ipv4'`
PUBLIC_IP=`wget -q -O - 'http://169.254.169.254/latest/meta-data/public-ipv4'`

apt-get install -y openswan xl2tpd

cat > /etc/ipsec.conf <<EOF
version 2.0
config setup
  dumpdir=/var/run/pluto/
  nat_traversal=yes
  virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12,%v4:25.0.0.0/8,%v6:fd00::/8,%v6:fe80::/10
  oe=off
  protostack=netkey
  nhelpers=0
  interfaces=%defaultroute
conn vpnpsk
  auto=add
  left=$PRIVATE_IP
  leftid=$PUBLIC_IP
  leftsubnet=$PRIVATE_IP/32
  leftnexthop=%defaultroute
  leftprotoport=17/1701
  rightprotoport=17/%any
  right=%any
  rightsubnetwithin=0.0.0.0/0
  forceencaps=yes
  authby=secret
  pfs=no
  type=transport
  auth=esp
  ike=3des-sha1
  phase2alg=3des-sha1
  dpddelay=30
  dpdtimeout=120
  dpdaction=clear
EOF

cat > /etc/ipsec.secrets <<EOF
$PUBLIC_IP  %any  : PSK "$IPSEC_PSK"
EOF

cat > /etc/xl2tpd/xl2tpd.conf <<EOF
[global]
port = 1701
;debug avp = yes
;debug network = yes
;debug state = yes
;debug tunnel = yes
[lns default]
ip range = 192.168.42.10-192.168.42.250
local ip = 192.168.42.1
require chap = yes
refuse pap = yes
require authentication = yes
name = l2tpd
;ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes
EOF

cat > /etc/ppp/options.xl2tpd <<EOF
ipcp-accept-local
ipcp-accept-remote
ms-dns 8.8.8.8
ms-dns 8.8.4.4
noccp
auth
crtscts
idle 1800
mtu 1280
mru 1280
lock
connect-delay 5000
EOF

cat > /etc/ppp/chap-secrets <<EOF
# Secrets for authentication using CHAP
# client	server	secret			IP addresses
$VPN_USER	l2tpd   $VPN_PASSWORD   *
EOF

iptables -t nat -A POSTROUTING -s 192.168.42.0/24 -o eth0 -j MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forward

iptables-save > /etc/iptables.rules

cat > /etc/network/if-pre-up.d/iptablesload <<EOF
#!/bin/sh
iptables-restore < /etc/iptables.rules
echo 1 > /proc/sys/net/ipv4/ip_forward
exit 0
EOF

chmod a+x /etc/network/if-pre-up.d/iptablesload

/etc/init.d/ipsec restart
/etc/init.d/xl2tpd restart