SSH: Port Forwarding¶

Port Forwarding - The Problem (1)¶

Remote port is unreachable (behind a firewall)
Remote computer has a service running
That service listens on port 1234
The service’s protocol is not encrypted
⟶ remote admin denies access through the firewall. Right he is!
I have SSH access to the remote computer because I am trusted.

Port Forwarding - The Problem (2)¶

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Port Forwarding - The Solution (1)¶

Hmmm …

I am trusted ⟶ I have access to the remote computer via port 22/ssh
⟶ I can login to the remote computer
⟶ I can do there whateer I am permitted to
⟶ I can login to the remote computer and connect to port 1234

Hmmm …

Then it cannot be a security risk if I automate the entire process

Port Forwarding - The Solution (2)¶

../../../../../_images/ssh-tunnel-solution.svg

Port Forwarding - The Commandline ¶

Creating the tunnel during login

$ ssh -L 5678:127.0.0.1:1234 jfasch@home.com

Rather than connect to remote computer on port 1234 (remember: not possible because of firewall), the client connects to port 5678 locally
As a reaction, SSH server (“daemon”, sitting on the remote computer) connects to port 1234 on remote machine
Client (local/5678) and service (remote/1234) are “virtually” connected