Reverse SSH

ssh_reverse.md

SSH Reverse Proxy

Some simple notes to setup SSH reverse proxy

1. on source machine (behind the network), run: ssh -N -R 2222:localhost:22 YOURUSER@YOURSERVER

2. on YOURSERVER, run: ssh -l SOURCEUSER -p 2222 localhost

3. If you want to automated it, do something like...

#!/bin/bash
createTunnel() {
  /usr/bin/ssh -N -R 2222:localhost:22 serverUser@25.25.25.25
  if [[ $? -eq 0 ]]; then
    echo Tunnel to jumpbox created successfully
  else
    echo An error occurred creating a tunnel to jumpbox. RC was $?
  fi
}
/bin/pidof ssh
if [[ $? -ne 0 ]]; then
  echo Creating new tunnel connection
  createTunnel
fi

4. Get the right permissions chmod +x create_ssh_tunnel.sh

5. Cron it up! crontab -e then jam in:

*/1 * * * * ~/create_ssh_tunnel.sh > tunnel.log 2>&1

Consider adding a sleep $(( ( RANDOM % 10 ) + 1 )) if you'd like the tunnel re-establishment to be a little less deterministic. Someone could notice an SSH session opening every minute on the minute. Mix it up to look human.