Is anyone familiar with adding functionality to the macOS pre-boot process? I'm trying to supplement FileVault's functionality so that it can integrate with a user directory service, which isn't really an Apple-supported or well-documented type of task.
My goal is to allow remote users to unlock and login to the device without having a local account setup yet. FileVault currently only allows users with existing local accounts to unlock a device. I'm working on a Mac Pro running macOS High Sierra 10.13.6 with APFS.
Based on Apple's documentation of the boot process and Eclectic Light Co's articles on the topic, my understanding is that pre-boot procedures such as kernel loading and FileVault decryption are handled by the
boot.efi file in the Preboot APFS disk partition.
So as far as I can tell, I need to modify how
boot.efi works to achieve my goals. Is there a way I can build my own
boot.efi with additional functionality and then safely replace the existing one, or can I add a supplemental EFI file with additional functionality that is run in conjunction with
Along those lines, the only resource I have found so far is Piker Alpha's boot loader source tree, but I'm hesitant to use this project since it appears to be outdated/only for HFS+ based Macs (and also only builds using Visual Studio).
Does anyone have other resources or suggestions on how I can modify macOS pre-boot procedures?