A simple daemon for MacOS that (very sloppily) detects whether the gpg-agent is waiting for touch input from the YubiKey and posts a notification for the user.
It works by creating a UNIX socket to which the gpg-agent logs are redirected and simply checking for log messages containing "detected card with S/N". Once such a message is detected it posts a notification using notify-rust. In theory this should be Linux-compatible, however I have not tested it and I recommend you use the more stable yubikey-touch-detector.
The gpg-agent documentation explicitly states that these logs are intended for debugging and may change without further notice. However this was the easiest way I could figure out, that did not involve calling gpg and trying to guess if it is stuck waiting for a smartcard. At the time of this writing it is working pretty well, but use at your own risk.
If you happen to have a better idea as to how to implement it please reach out to me, I'd love to hear it!
Make sure rust and cargo are installed on your system. Build using
cargo build --releasePass the path of the UNIX socket to be created via the --socket argument e.g.:
yubikey-watcher --socket /tmp/yubikey-watcher.sock
Adjust your ~/.gnupg/gpg-agent.conf to redirect the log files to the socket by adding:
log-file socket:///tmp/yubikey-watcher.sock
Copy the resulting binary (located in target/release/yubikey-watcher) to a location of your choice.
You can either run the binary on its own or create an OS X launch agent configuration to run it in the background.
A template for the OS X launch agent can be found in daemon/at.sigmoid.yubikey-watcher.plist.
Adjust the paths as required for your setup, copy the launch agent plist to ~/Library/LaunchAgents and load it via launchctl load -w ~/Library/LaunchAgents/at.sigmoid.yubikey-watcher.plist.