gosshauth

gosshauth

A tiny hook tool for bash/zsh to re-authenticate with ssh-agent.

What's this?

This small command manages sockets for SSH authentication created by ssh-agent. It automatically detects the valid socket and rewrite the symlink to avoid disconnecting.

When do I need this?

ssh-agent stores the path for sockets into $SSH_AUTH_SOCK. It is a path below, for instance.

# example in macOS
$ echo $SSH_AUTH_SOCK
/private/tmp/com.apple.launchd.sa197Z7kVN/Listeners

This changes every time you login and ssh-agent detects the changes and makes $SSH_AUTH_SOCK indicate validly. Usually that's enough.

But when you use terminal multiplexers -- tmux, screen, or so --, it breaks this.

Reproducible way

1. Login your Mac.

• $SSH_AUTH_SOCK is /some/path/to/Listeners.

1. SSH into a Linux box.

• $SSH_AUTH_SOCK will be changed into /tmp/path/to/agent.foo.

1. Launch tmux in the box. Also you can use SSH authentication in tmux by ssh-agent.
2. Detach tmux and logout the box.
3. SSH into the box again.

• $SSH_AUTH_SOCK will be changed into /tmp/path/to/agent.bar.

1. Attach the existent tmux session.
2. $SSH_AUTH_SOCK will be /tmp/path/to/ssh-agent.foo, not ...bar. You can NOT use SSH authentcation in it.

Solution

Here is gosshauth. You can install this from release page or a command below.

go get github.com/delphinus/gosshauth

And you should set the hook for zsh/bash.

# for bash
if which gosshauth > /dev/null 2>&1; then
  eval "$(gosshauth hook bash)"
fi

# for zsh
if (( $+commands[gosshauth] )); then
  eval "$(gosshauth hook zsh)"
fi

# for fish
if type -q gosshauth
  gosshauth hook fish | source
end

Now you can use SSH authentication even if in the way above.

How do gosshauth work for this?

1. Check $SSH_AUTH_SOCK.
2. gosshauth checks the existence.

• If exists, that's all, done.

1. gosshauth globs all socket-like files for /tmp/**/Listeners and /tmp/ssh*/agent.*.
2. The candidate that has the latest timestamp is the goal, maybe. gosshauth rewrite the ~/.ssh/auth_sock symlink to target the goal, and set $SSH_AUTH_SOCK to use it.

Author

JINNOUCHI Yasushi <me@delphinus.dev>

License

The MIT License