What is it?

If you have a webserver running on one computer (say your development laptop), and you want to expose it securely (ie HTTPS) via a public URL, SirTunnel allows you to easily do that.

How do you use it?

If you have:

• A SirTunnel server instance listening on port 443 of example.com.
• A copy of the sirtunnel.py script available on the PATH of the server.
• An SSH server running on port 22 of example.com.
• A webserver running on port 8080 of your laptop.

And you run the following command on your laptop:

ssh -tR 9001:localhost:8080 example.com sirtunnel.py sub1.example.com 9001

Now any requests to https://sub1.example.com will be proxied to your local webserver.

How does it work?

The command above does 2 things:

1. It starts a standard remote SSH tunnel from the server port 9001 to local port 8080.
2. It runs the command sirtunnel.py sub1.example.com 9001 on the server. The python script parses sub1.example.com 9001 and uses the Caddy API to reverse proxy sub1.example.com to port 9001 on the server. Caddy automatically retrieves an HTTPS cert for sub1.example.com.

Note: The -t is necessary so that doing CTRL-C on your laptop stops the sirtunnel.py command on the server, which allows it to clean up the tunnel on Caddy. Otherwise it would leave sirtunnel.py running and just kill your SSH tunnel locally.

How is it different?

There are a lot of solutions to this problem. In fact, I've made something of a hobby of maintaining a list of the ones I've found so far.

The main advantages of SirTunnel are:

• Minimal. It leverages Caddy and whatever SSH server you already have running on your server. Other than that, it consists of a 50-line Python script on the server. That's it. Any time you spend learning to customize and configure it will be time well spent because you're learning Caddy and your SSH server.
• 0-configuration. There is no configuration on the server side. Not even CLI arguments.
• Essentially stateless. The only state is the certs (which is handled entirely by Caddy) and the tunnel mappings, which are ephemeral and controlled by the clients.
• Automatic HTTPS certificate management. Some other solutions do this as well, so it's important but not unique.
• No special client is required. You can use any standard SSH client that supports remote tunnels. Again, this is not a unique feature.

Running the server

Assuming you already have an ssh server running, getting the SirTunnel server going consists of simply downloading a copy of Caddy and running it with the provided config. Take a look at install.sh and run_server.sh for details.

Note: Caddy needs to bind to port 443, either by running as root (not recommended), setting the CAP_NET_BIND_SERVICE capability on the Caddy binary (what the install.sh script does), or changing caddy_config.json to bind to a different port (say 9000) and using something like iptables to forward to that port.