SSHConsole

A simple command console for servers using SwiftNIO SSH.

Why Would I Use This?

This package provides an SSH listener to your server which allows you to ssh commmands to your server and receive the response back to your terminal.

You might use this to report on your server's internals, issue tuning commands, or tell it to restart or shutdown.

It is MIT licensed. Go wild.

How Much Work is This?

Just three lines of code.

Plus 5 to manage your host key so you don't annoy yourself by having to approve a new one each time you restart your server.

Plus 10 more to have some sort of responsible authentication.

Plus however you do your commands. I use Swift Argument Parser to define my commands, which is great, but not quite intended to be used this way and there is a page of extensions required to work around it's limitations. But strictly speaking, that's not part of this project and you can do whatever you want with your commands.

Can You Show Me?

import SSHConsole

/// get your program doing it's stuff

let console = SSHConsole( port:2525, 
                          hostKeys:hostKeys, 
                          passwordDelegate: TrivialPassword(), 
                          publicKeyDelegate: AuthenticatePublicKey() )
try console.listen( runner: myHandler )

func myHandler( command: String, to: SSHConsole.CommandHandler.Output, user:String, environment: [String : String]) {
    to.write("Thank you for connecting to my demo service.\r\n")
    to.write("Good bye now.\r\n")
}

/// wait around in your program until you are ready to exit

try console.stop()   // Or don't, but this flushes and closes the open sockets

Ok, I've lied there. You will notice that TrivialPassword() seems like a really bad idea, AuthenticatePublicKey() is not defined. But go look in the example Echo server. The whole think with all the missing bits as ~130 lines and that's mostly comments for you.

Here is the complete source for the Echo server

How Much Does This Drag In?

• SwiftNIO SSH

• SwiftNIO SSH will then drag in SwiftNIO, and Swift Crypto but you probably already have them if you are writing a server.

It Looks Small, What Kind of Limitiations Does It Have?

• It only does commands with no input. If you try to send input it will chastise you and destroy your sockets. I thought about adding sessions, but that is more code than the whole thing now, and if I give you that you'll want command line editting and recall, and well, it all can get out of hand in a hurry. There is a utility which lets you edit commands locally and ship them off on enter. But I've forgotten the name. Still, it would be great with this. Maybe someone will remind me and I'll suggest it here.

• It doesn't handle RSA keys. This is a, possibly permanent, limitation of the SwiftNIO SSH project.

• It only does ED25519 host keys. This can be expanded, but I'm annoyed at Swift NIO blinding me to the private keys and I'm hoping they'll open that up and I won't have to write the 20 lines of code to expand my shadow private key logic I use to work around the blinding.

How Stable is the API?

Mostly stable. There is still a problem where I can't find the authenticated user name, so I'm passing "???". That will either get resolved by me finding the name, or removing the ability to know which user is running your command.

How Committed Is The Maintainer?

Not at all. This is a two-day rathole I ran down for my own servers. I'll use it and probably spend another day polishing it, but if you are a sizeable organization or an active developer and want to use it, maybe I should give it to you. (I also vanish for months at a time, so responses are not timely.) – fork is your friend

What's Next?

• Still working on retrieving the authenticated user, sending "???" for now.

• Can I send an exit code back through this to the client?