mkosi-obs: Replace usage of pesign/efitools with systemd-sbsign

[DaanDeMeyer]

Let's consolidate on systemd-sbsign across mkosi to do everything related to secure boot signing.

[DaanDeMeyer]

Requires systemd/systemd#36574

[bluca]

It's fine to use these new tools elsewhere, but I do not want them in the OBS scripts. Everything else in OBS uses pesign, including package builds, so I want to use the same thing, to guarantee it works. pesign has also been battle-tested on real hardware for 10 years, while this new stuff hasn't, I imagine it will take a few years of actual usage before it becomes compatible with all the firmwares and hardware out there

[behrmann]

I mean, shouldn't we have both at least as an option? Assuming that it doesn't work in all cases, then if we don't dogfood it, it won't.

[bluca]

Sure it's fine to use these other tools elsewhere, in the ci, for local builds, etc etc

[DaanDeMeyer]

It's fine to use these new tools elsewhere, but I do not want them in the OBS scripts. Everything else in OBS uses pesign, including package builds, so I want to use the same thing, to guarantee it works. pesign has also been battle-tested on real hardware for 10 years, while this new stuff hasn't, I imagine it will take a few years of actual usage before it becomes compatible with all the firmwares and hardware out there

This is a bit ridiculous, as long as we generate identical output to the other tools, of course we'll be compatible. I'll add integration tests in systemd that ensure we generate the same output.

[bluca]

You cannot verify that you have the same output, because you don't have access to the same input - the certificate. And yes that matters. Hardware quirks matter too, as you found out the hard way with the padding bug in the stub. What the spec says and what happens in real life often diverge.

[DaanDeMeyer]

Cool I'll just modify this PR to have it call both systemd-sbsign and the existing tool and verify the output is identical for both tools and fail the build if it isn't. Then you can be happy knowing we're using your supposedly stable better tools and I can be happy knowing systemd-sbsign is dogfooded and if the comparison ever fails we'll automatically get a bug report so we can fix whatever is different in systemd-sbsign.

And eventually we'll just drop the other tools.