How to use the SSH protocol with Go – part 1/2 (opens in new tab)

Not yet.. I've set up a GitHub clone and had to patch OpenSSH: the authorisation process can execute an external command (AuthorizedKeysCommand option IIRC) but doesn't provide enough information to do a DB lookup à-la-GitHub.

Post author here, unfortunately no, after some time, we realized it was quicker to develop a complete SSH server than patching some legacy C code. It was really confortable to work with go to do that.

As jerf said, it's always difficult to see if an implementation of a protocol respects it completely. Most of us trust OpenSSH because of its background. It's old enough, the codebase is mature enough and maintained by the OpenBSD team. However it's quite a massive project, I don't know how they would be able that their implementation fits completely the 6 RFCs, I mean, more than the go implementation.

In our case, the SSH server is not for general purpose, but for something really specific, so it's really easier to test. What other feature? As I will explain next week, our SSH server is actually an authentication/autorization proxy which forwards connections to another server. By building our solution, it is now easier to control the logics for the load balancing etc.

That's really hard to answer.

On the other hand, OpenSSH's server has become so big that even when it is perfectly implementing the security contract its authors intend it can still allow users to do things that may surprise the heck out of you. Given what I've seen of trying to secure things that use SSH and really shouldn't, I would believe it might be easier to audit your own server rather than a deployment of opensshd.

Hi j_s,

By sensitive data, we meant part of the identity of all our users (there is quite often user@host at the end of the public keys sent by our users), and the second point is linked to the internal commands.

In the `command="ssh-handler" ssh-rsa....` the command doesn't receive the SSH public key as argument, so we would have to provide additional information like: `command="ssh-handler <user_id|username|key_id>" ssh-rsa....` So yes, if we have a way to avoid having a copy of that on all our servers able to authenticate users, we take it!