Tunneled SSH Connections

Bad actors are constantly scanning the internet for exposed SSH services. Changing the default port obfuscates, but doesn't protect the service, and implementing and updating advanced SSH authentication can be cumbersome.

By tunneling SSH connections through your Pomerium service:

• All traffic is encrypted twice (once by the Pomerium TCP connection, once by SSH itself),
• The SSH service can remain closed to the internet, or even restricted to only accept connections from the Pomerium Proxy service
• Authentication and authorization is managed by Pomerium, using your IdP for identity, and can be easily managed at scale.

TIP

This example assumes you've already created a TCP route for this service.

Basic Connection

1. Create a TCP tunnel, using either pomerium-cli or the Pomerium Desktop client:

   pomerium-cli tcp aService.corp.example.com:22 --listen :2202
   

   --listen

   The --listen flag is optional. It lets you define what port the tunnel listens on locally. If not specified, the client will choose a random available port.

   

   Local Address

   The Local Address field is optional. Using it defines what port the tunnel listens on locally. If not specified, Pomerium Desktop will choose a random available port.

2. Initiate your SSH connection, pointing to localhost:

   ssh user@localhost -p 2202
   

Tunnel and Connect Simultaneously

The process outlined above requires multiple steps and terminal environments (when using the CLI) or programs (when using the Desktop Client). By invoking pomerium-cli when the connection is made, you can streamline the process into a single connection:

ssh -o ProxyCommand='pomerium-cli tcp --listen - %h:%p' ssh.localhost.pomerium.io

Always Tunnel through Pomerium

Once your SSH service is configured and tested through Pomerium, you can edit your local SSH configuration file to always create a tunnel when connecting to that service:

Host aService.corp.example.com
    ProxyCommand /usr/bin/pomerium-cli tcp --listen - %h:%p

You can even configure all SSH connections to your domain space to use the tunnel:

Host *.corp.example.com
    ProxyCommand /usr/bin/pomerium-cli tcp --listen - %h:%p

More Resources

For more information on SSH ProxyCommand, see:

• ProxyCommand (SSH man page) (opens new window)
• SSH to remote hosts though a proxy or bastion with ProxyJump (RedHat blog) (opens new window)