gpg-agent (macOS) doesn't provide any key for SSH

Question

There are several topics addressing similar issues, but none of the solutions provided there work for my environment, being:

• macOS 11.2.3 (MacBookPro M1/Apple silicon)
• GnuPG 2.2.27 (installed via Homebrew)
• Zsh shell
• GPG key with Auth-only subkey for SSH

The ~/.gnupg/gpg-agent.conf file:

pinentry-program /opt/homebrew/bin/pinentry-tty
enable-ssh-support

The ~/.gnupg/sshcontrol file:

FADD8723...AE7ED (the keygrip retrieved with `gpg -K --with-keygrip`)

The ~/.zshrc file:

unset SSH_AGENT_PID
export GPG_TTY="$(tty)"
export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket)
gpgconf --launch gpg-agent

I made sure ssh-agent is not running (also rebooted the system to be sure). But no keys are found when running:

ssh-add -L
The agent has no identities

What am i missing?

EDIT: I should add that I also configured a few Debian 10 systems like this and it works just fine.

Answer 1

It looks like you're using gpg-agent for handling SSH keys instead of ssh-agent. This is fine, but because SSH keys can be installed anywhere on the system, you still have to use ssh-add to add the keys to the agent as before. At least on Linux, gpg-agent will memorize which keys you've told it about and try to load them the next time, but you still need to tell it which keys to use at first.