GNet Solutions » FreeBSD Administration

This is a guide for setting up a persistent reverse SSH tunnel using AutoSSH on FreeBSD.

Once completed, the service that will autostart at boot will open port 5000 on the remote SSH connection that will allow SSH connections back to the originating host.

Prepare the Environment¶

• Switch to the root user:
  

  sudo -s
  

• Make sure the system is up to date:
  

  pkg update && pkg upgrade
  

• Generate a root ssh keypair:
  

  ssh-keygen -t ed25519
  

• Copy the ssh public key to the remote host:
  

  ssh-copy-id bob@ssh.example.com
  

AutoSSH¶

• Install autossh:
  

  pkg install autossh
  

Host Config¶

• Create a .ssh config file:
  

  vi ~/.ssh/config
  

  • And add the following:
    

    Host remote-tunnel-home
       HostName      ssh.example.com
       User          bob
       Port          7022
       IdentityFile  ~/.ssh/id_ed25519
       RemoteForward  5000 localhost:22
       ServerAliveInterval 30
       ServerAliveCountMax 3
    

Start Tunnel at Boot¶

• Edit the rc.local file:
  

  vi /etc/rc.local 
  

  • And add the following:
    

    #!/bin/sh
    
    /usr/local/bin/autossh -M 0 -N remote-tunnel-home &
    

• Run the script to start the tunnel without rebooting:
  

  sh /etc/rc.local
  

Resources¶

• https://raymii.org/s/tutorials/Autossh_persistent_tunnels.html
• https://www.everythingcli.org/ssh-tunnelling-for-fun-and-profit-autossh/
• https://blog.sleeplessbeastie.eu/2014/12/23/how-to-create-persistent-reverse-ssh-tunnel/