VPN over SSH
There are several ways to set up a Virtual Private Network through SSH. Note that, while this may be useful from time to time, it may not be a full replacement for a regular VPN. See for example .
OpenSSH's built in tunneling
OpenSSH has built-in TUN/TAP support using -w<local-tun-number>:<remote-tun-number>. Here, a layer 3/point-to-point/ TUN tunnel is described. It is also possible to create a layer 2/ethernet/TAP tunnel.
Create tun interfaces using netcfg
Create tun interfaces:
$ cat /etc/network.d/vpn INTERFACE='tun5' CONNECTION='tuntap' MODE='tun' USER='vpn' GROUP='network' IP='static' SKIPNOCARRIER='yes' ADDR='<IP>' IPCFG=('ip route add <REMOTE-NETWORK/MASK> via <REMOTE-SIDE-IP>')
Then do 'netcfg -u vpn' or add it into /etc/conf.d/netcfg.
Create tun interfaces using systemd-networkd
$ cat /etc/systemd/network/vpn.netdev [NetDev] Name=tun5 Kind=tun [Tun] User=vpn Group=network $ cat /etc/systemd/network/vpn.network [Match] Name=tun5 [Address] Address=192.168.200.2/24
Once these files are created, enable them by restarting
Also you may manage tun interfaces with 'ip tunnel' command.
Creating interfaces in SSH command
SSH can create both interfaces automatically, but you should configure IP and routing after the connection is established.
ssh \ -o PermitLocalCommand=yes \ -o LocalCommand="sudo ifconfig tun5 192.168.244.2 pointopoint 192.168.244.1 netmask 255.255.255.0" \ -o ServerAliveInterval=60 \ -w 5:5 email@example.com \ 'sudo ifconfig tun5 192.168.244.1 pointopoint 192.168.244.2 netmask 255.255.255.0; echo tun0 ready'
ssh -f -w5:5 firstname.lastname@example.org -i ~/.ssh/key "sleep 1000000000"
or you may add keep-alive options if you are behind a NAT.
ssh -f -w5:5 email@example.com \ -o ServerAliveInterval=30 \ -o ServerAliveCountMax=5 \ -o TCPKeepAlive=yes \ -i ~/.ssh/key "sleep 1000000000"
- ssh should have access rights to tun interface or permissions to create it. Check owner of tun interface and/or /dev/net/tun.
- Obviously if you want to access a network rather than a single machine you should properly set up IP packet forwarding, routing and maybe a netfilter on both sides.
Using PPP over SSH
pppd can easily be used to create a tunnel through an SSH server:
/usr/sbin/pppd updetach noauth silent nodeflate pty "/usr/bin/ssh root@remote-gw /usr/sbin/pppd nodetach notty noauth" ipparam vpn 10.0.8.1:10.0.8.2
When the VPN is established, you can route traffic through it. To get access to an internal network:
ip route add 192.168.0.0/16 via 10.0.8.2
To route all Internet traffic through the tunnel, for example to protect your communication on an unencrypted network, first add a route to the SSH server through your regular gateway:
ip route add <remote-gw> via <current default gateway>
Next, replace the default route with the tunnel
ip route replace default via 10.0.8.2