A new macOS EFI password tool has appeared on Github today
…but I’ve no time today to look at how it works. 😦
CLOSED-SOURCE WARNING: The project includes a few pre-compiled .EFI binaries but no source, so be careful.
https://github.com/smileycreations15/EFI-Firmware-Password-Simulator
See-also:
https://firmwaresecurity.com/2018/05/02/apple-set-your-firmware-password/
https://firmwaresecurity.com/2016/01/02/efi_bruteforce-efi-pin-of-apple-macbooks/