VPN over SSH

Manual creation and destruction of interfaces

On the pivot machine

sudo ip tuntap add dev tun0 mode tun
sudo ip addr add 10.43.43.1/30 peer 10.43.43.2 dev tun0
sudo ip link set tun0 up

sudo sysctl net.ipv4.conf.default.forwarding=1

On the attacker machine

sudo ip tuntap add dev tun0 mode tun
sudo ip addr add 10.43.43.2/30 peer 10.43.43.1 dev tun0
sudo ip link set tun0 up

ssh user1@$PIVOT -w 0:0

-w permits to specify the interface numbers

Setup NAT on the pivot machine

sudo iptables -t nat -A POSTROUTING -s 10.43.43.2 -o eth1 -j MASQUERADE

Or

sudo iptables -t nat -A POSTROUTING -s 10.43.43.2 -d 10.42.42.0/24 -j MASQUERADE

Setup route on the attacker machine

sudo ip route add 10.42.42.0/24 via 10.43.43.1

Use ARP proxy instead of NAT

sudo sysctl net.ipv4.conf.eth0.proxy_arp=1
sudo ip neigh add proxy 10.43.43.2 dev eth0