SSH login with gpg keycard backed ssh key and pinentry-curses for pin fails

[necauqua]

Description

I know that this is a contrived setup (hence it probably wasn't reported), just making sure this is tracked.

Steps to Reproduce the Problem

1. Have a yubikey or similar
2. Configure a gpg auth subkey to be used for SSH and export it to the hw key
3. Configure gpg to use pinentry-ncurses for card pin

Expected Behavior

When you do fetch/push, pinentry should ask for the pin and then everything should work.

Actual Behavior

Instead you get the classic Error: authentication required but no callback set; class=Ssh (23); code=Auth (-16).

If you ssh into something once for the pin to get cached it starts working (without asking for pin, obviously).

When it was not pinentry-curses but whatever was the default it worked fine, asking for the pin the one time with a separate dialog window.

And the most interesting thing is that gpg signing works! When you snapshot or whatever for the first time after boot it asks for the pin with pinentry and works just fine. Probably because for gpg we just call the gpg binary and for ssh it's another libssh issue - so this likely may be fixed by the openssh build.

Specifications

• Platform: NixOS
• Version: 0.20.0