2018 October 23
Here’s another bit of backlog to clear out: I’ve been toying with the idea of writing a certain small utility program for a while now, and earlier this year I finally want ahead and did it. The result is called stund, which is short for “SSH tunnel daemon”.
stund will open an SSH tunnel for you and maintain it in the background. The key trick is that it can do this even when you need to perform some kind of interactive login to start your connection. This UX might sound simple enough, but the implementation is surprisingly complex — the only way to accomplish it is to start SSH attached to its own pseudoterminal, then relay input back and forth between the user’s terminal and the SSH virtual session during the login phase.
If you use SSH connection sharing — which you should — stund makes it so that you can just login once in the morning and not worry about having to type your password throughout the day. I’ve found this to be an extremely helpful feature since system administrators are tending to require password and/or two-factor authentication more and more these days.
So, yes, the effect is basically like running SSH inside
screen, or launching it with
ControlPersist set to yes. But the user experience is cleaner:
$ stund open ssh.aoc.nrao.edu
pwilliam@ssh.aoc.nrao.edu’s password:
[Tunnel successfully opened.]
$
Importantly, this behavior makes it relatively easy to incorporate stund into shell scripts and other batch-y operations — you can put it at the top of the file, then use the connection throughout your script. The user can type their password right off the bat and then walk away. I don’t know how to do this cleanly with screen.
There are more details in the README. As mentioned in my how-to on SSH connection sharing, this kind of user experience polish might not sound important, but I’ve found that it dramatically smoothes the ways in which I interact with remote computer systems.
stund is a simple static Rust program, so it should be pretty easy to install — you will need the Rust compilers, but they’re easy to install on just about any platform. stund won’t work on Windows, though, because the whole concept of a pseudoterminal is Unix-specific.