Add UEFI structs

[Foxboron]

This is a draft PR that includes the current progress on parsing UEFI structs as defined in Version 2.8 Errata A. Attempting to parse the revocation list published by UEFI as they are easy to fetch and usually interesting to look at.

https://uefi.org/revocationlistfile

Currently it hits the wall of what the pattern language can do, but nonetheless probably interesting.

Signed-off-by: Morten Linderud morten@linderud.pw

[WerWolv]

Thanks a lot for the PR!

What are some things that are currently missing in the language in order to properly parse the data? I'm always glad to add new features.

[Foxboron]

A EFI_SIGNATURE_LIST file is one or more signature lists. Currently I can only have one EFI_SIGNATURE_LIST struct in dbx_esl, and no way to say "read EFI_SIGNATURE_LIST until EOF". That's the first one.

The second one is that each EFI_SIGNATURE_LIST can contain multiple signatures inside the list (e.g the published DBX has 3 signature lists. 2 signature lists with one x509 certificate each, and one signature list with 190 sha256 checksums). I know the size of the last signature list with the checksums, and I know how large each of the sha256 checksum structs are. But I can't say "Parse this struct (200/20) times".

sizeof would be neat, but defining the static sizes isn't really hard either.

Thanks for the work on this project :)

[WerWolv]

The first issue requires some kind of loops and a way to get the current offset and the size of the whole file probably. That's definitely something I can implement.
For the second one, aren't if-else conditionals enough for that?

sizeof and co are planed and will probably come with the next version :)

[Foxboron]

The first issue requires some kind of loops and a way to get the current offset and the size of the whole file probably.

EFI_SIGNATURE_LIST x509_1[...];

You could maybe also do it declaratively by saying the above. Would allow [5...] which would be "read at least 5 until EOF"

For the second one, aren't if-else conditionals enough for that?

No, I need to be able to express "read 10 of these structs" with math in practise.

[hexadecimalDinosaur]

The first issue requires some kind of loops and a way to get the current offset and the size of the whole file probably. That's definitely something I can implement.

This would be much appreciated for writing patterns for filetypes like PNG which have an unknown amount of chunks.

[Foxboron]

For the sake of inspiration I implemented the same with GNU Poke

https://github.com/Foxboron/poke-uefi/blob/master/uefi.pk#L87

EFI_SIGNATURE_LIST[] lists was enough to read the lists until EOF and similar to the suggested syntax above

[WerWolv]

I'm just gonna merge this PR now because what the hell