Setup reverse SSH tunnel

Posted on 30.09.16   CLI Linux Raspberry Pi SysAdmin

Quick example for setting up reverse SSH tunnels on clients which can be controlled from the server anywhere. This example presumes all the clients has a unique id, for example 9001, 9002, 9003, 9004 etc.
Let’s say we have 10 clients stuck behind a firewall we’d like to access.

Start the SSH server on all clients like this:

ssh -R 1xxxx:localhost:22 user@server.com // replace xxxx with this client's unique id

Now we have all our clients setup with a reversed ssh tunnel.
If we’d like to ssh into id 9003 we run the following command from the server:

ssh user@localhost -p 19003

Lets ssh into 9005 instead:

ssh user@localhost -p 19005

Replace user with a local user on the client machine.

Example

I want to ssh into my Raspberry Pi. Local username is pi.

  • Step 1 – setup reverse ssh tunnel on the raspberry:
    ssh -R 19999:localhost:22 kek@it-db.com
  • Step 2 – from my “it-db.com” server I run the following command:
    ssh pi@localhost -p 19999

Combining with sshpass and autossh

sshpass -p "mypassword" autossh -R 19999:localhost:22 user@server.com

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