Ask HN: Why is there no native SSH hook to run a local command before connecting

6•tetris11•2d ago

The `LocalCommand` parameter only runs a command on the local machine after the connection is established.

Is there no pre-connection hook?

My use case is simply that I do port knocking to expose my ssh port, and want this working automatically at the SSH config level so that I can use it transparently from other utilities (e.g. Ansible inventory, Emacs over TRAMP)

Comments

Bender•2d ago

This [1] is one way.

[1] - https://unix.stackexchange.com/questions/44307/can-ssh-confi...

ranger_danger•4h ago

Besides the ProxyCommand approach, another way would be to define 'ssh' as a shell alias/function that does the port knocking first and then passes any parameters to the normal /usr/bin/ssh.

Or you could make your own 'ssh' shell script somewhere else on the filesystem that handles it for you.

dylan604•3h ago

without making it an alias, would this shell script somewhere else be usable by the other applications from the question? if you can provide the specific path rather than the system looking for whatever ssh was installed, then maybe, but i don't know those specifics which makes using the shell script have question marks.

waqasx•3h ago

You can write a script and put it in PATH

ranger_danger•3h ago

You could either put the script somewhere earlier within the PATH than wherever the normal ssh binary is, or manually export a new PATH with some other custom folder that comes first, which you could use to override anything, e.g. export PATH=/root/bin:$PATH

capitainenemo•3h ago

Can't you use Match exec?

bityard•3h ago

OpenSSH was written by and is still maintained by those who adhere to The Unix Way. If you asked for this feature, they would probably tell you to just use a shell alias or function instead.

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