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Date: Wed, 30 Mar 2022 08:18:59 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Daniel Kiper <daniel.kiper@oracle.com>,
 Alec Brown <alec.r.brown@oracle.com>,
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 Kees Cook <keescook@chromium.org>
Subject: Re: Linux DRTM on UEFI platforms
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On Wed, Mar 30, 2022 at 09:12:19AM +0200, Ard Biesheuvel wrote:
> On Wed, 30 Mar 2022 at 09:11, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> > The EFI stub carries out a bunch of actions that have meaningful
> > security impact, and that's material that should be measured. Having the
> > secure launch kernel execute the stub without awareness of what it does
> > means it would need to measure the code without measuring the state,
> > while the goal of DRTM solutions is to measure state rather than the
> > code.
> 
> But how is that any different from the early kernel code?

>From a conceptual perspective we've thought of the EFI stub as being 
logically part of the bootloader rather than the early kernel, and the 
bootloader is a point where the line is drawn. My guy feeling is that 
jumping into the secure kernel environment before EBS has been called is 
likely to end badly.