Hi Krystian,

On 14.09.24 00:03, Krystian Hebel wrote:
>> So, what I'm suggesting is to just look for an update in a pre-
>> defined path on the boot medium. [...]
>
> This is something we were considering. The problem with that
> approach is that coreboot can (and, in most of platforms
> supported by us, does) lock the boot medium, either by
> mechanism implemented by src/security/lockdown, or SMM BWP,
> or both. The payload isn't able to remove those locks, they
> wouldn't be of much use if it could.

Um no, not coreboot. coreboot is free software and if it would
do something that hinders security,  we would fix it.  Judging
by the terms you are using,  I assume this is about Intel FSP.
FSP does lock things,  sometimes too early,  sometimes even in
an insecure state (i.e. locking empty protection registers). I
don't think we should allow Intel's insecurity to have such an
influence on coreboot designs,  rather we should contain it as
much as possible, i.e. try to find solutions that are as close
as possible to what we would do in a nicer world without FSP.

> The only option is to not set them in the first place, which
> means that coreboot must be aware of existence of update,
> whatever it's form may be. Dealing with in-memory capsules
> is much easier than adding storage and filesystem drivers
> to coreboot, not to mention that this would be against its
> design philosophy.

You're mixing things that shouldn't be mixed, IMO. Absolutely
yes, of course  dealing with memory structures is easier than
dealing with storage  *in coreboot*.  But we shouldn't do any
such data processing *in coreboot*, anyway. What coreboot re-
quires is only the control over the locking.  And there *are*
alternatives.

tl;dr this is what we came up with @secunet when Intel FSP was
pushed into mainstream coreboot:  We use an nvram flag to tell
coreboot to lock or not[1].  The payload then has to live with
what it gets: locked => don't update, unlocked => don't boot.

Nico

[1] https://review.coreboot.org/c/coreboot/+/56344/

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