Script to set up an ipsec tunnel between two machinesFor Example: ./tunnel.sh 10.10.10.1 10.10.10.2 192.168.0.1 192.168.0.2 would set up an ipsec tunnel over 10.10.10.1 address using 192.168.0.1 as a virtual addresspasswordless sudo required for user on remote machine

tunnel.sh

#!/bin/bash

if [ "$4" == "" ]; then
    echo "usage: $0 <local_ip> <remote_ip> <overlay_local_ip> <overlay_remote_ip>"
    echo "creates an ipsec tunnel between two machines"
    exit 1
fi

SRC="$1"; shift
DST="$1"; shift
LOCAL="$1"; shift
REMOTE="$1"; shift

KEY1=0x`dd if=/dev/urandom count=32 bs=1 2> /dev/null| xxd -p -c 64`
KEY2=0x`dd if=/dev/urandom count=32 bs=1 2> /dev/null| xxd -p -c 64`
ID=0x`dd if=/dev/urandom count=4 bs=1 2> /dev/null| xxd -p -c 8`

echo "spdflush; flush;" | setkey -c
ip xfrm state add src $SRC dst $DST proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc aes $KEY2
ip xfrm state add src $DST dst $SRC proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc aes $KEY2
ip xfrm policy add src $LOCAL dst $REMOTE dir out tmpl src $SRC dst $DST proto esp reqid $ID mode tunnel
ip xfrm policy add src $REMOTE dst $LOCAL dir in tmpl src $DST dst $SRC proto esp reqid $ID mode tunnel
ip addr add $LOCAL dev lo
ip route add $REMOTE dev eth0 src $LOCAL


ssh $DST /bin/bash << EOF
    echo "spdflush; flush;" | setkey -c
    ip xfrm state add src $SRC dst $DST proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc aes $KEY2
    ip xfrm state add src $DST dst $SRC proto esp spi $ID reqid $ID mode tunnel auth sha256 $KEY1 enc aes $KEY2
    ip xfrm policy add src $REMOTE dst $LOCAL dir out tmpl src $DST dst $SRC proto esp reqid $ID mode tunnel
    ip xfrm policy add src $LOCAL dst $REMOTE dir in tmpl src $SRC dst $DST proto esp reqid $ID mode tunnel
    ip addr add $REMOTE dev lo
    ip route add $LOCAL dev eth0 src $REMOTE
EOF