tunnel

Note that this library is experimental.

tunnel is a very simple library that allows you to create multi-hop SSH tunnels. From the endpoint of the tunnel you can then Dial() to create network connections, or you can Listen() for incoming connections.

This library uses the ssh-agent to load any keys you might need. If you need to load keys from files, let me know and I'll probably add support for it.

You are responsible for closing any connections or listeners you make. The tunnel doesn't keep track of any connections you might have opened.

You can create multiple connections through the same tunnel.

Typical use

Import

Add the folliwing import and run go mod tidy to add tunnel to your project.

import "github.com/borud/tunnel"

Creating the tunnel

tunnel, err := tunnel.Create(tunnel.Config{
    Hops: []string{
        "bob@bastion.example.com:22",
        "alice@inside.example.com:22",
    },
})

Dial

You can Dial to create a new connection over the tunnel like so:

  conn, err := tunnel.Dial("tcp", "service.example.com:4711")

If everything went according to plan you now have a tunnel that terminates at inside.example.com (since it is the last hop) and connects from there to port 4711 on service.example.com

Listen

You can also listen on the remote endpoint.

listener, err := tunnel.Listen("tcp", ":80")

A note on Listen ports

When you want to Listen to remote ports that should be externally available, you have to make sure that the SSH daemon is configured to allow this. Please review the GatewayPorts configuration option in sshd_config. If you were too lazy to read this paragraph and are just looking for a cut and paste, the config is:

GatewayPorts yes