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Date:   Fri, 8 Jul 2022 05:56:38 +0100
From:   Matthew Garrett <mjg59@srcf.ucam.org>
To:     Brendan Trotter <btrotter@gmail.com>
Cc:     "Daniel P. Smith" <dpsmith@apertussolutions.com>,
        The development of GNU GRUB <grub-devel@gnu.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Daniel Kiper <daniel.kiper@oracle.com>,
        Alec Brown <alec.r.brown@oracle.com>,
        Kanth Ghatraju <kanth.ghatraju@oracle.com>,
        Ross Philipson <ross.philipson@oracle.com>,
        "piotr.krol@3mdeb.com" <piotr.krol@3mdeb.com>,
        "krystian.hebel@3mdeb.com" <krystian.hebel@3mdeb.com>,
        "persaur@gmail.com" <persaur@gmail.com>,
        "Yoder, Stuart" <stuart.yoder@arm.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        "michal.zygowski@3mdeb.com" <michal.zygowski@3mdeb.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        "lukasz@hawrylko.pl" <lukasz@hawrylko.pl>,
        linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
        James Morris <jmorris@namei.org>
Subject: Re: Linux DRTM on UEFI platforms
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On Fri, Jul 08, 2022 at 01:06:19PM +0930, Brendan Trotter wrote:

> This leaves me wondering what your true motivation is. Are you trying
> to benefit GRUB/Trenchboot (at the expense of security, end-user
> convenience, distro installer hassle, etc); or trying to manufacture
> scope for future man-in-the middle attacks (by promoting a solution
> that requires something between firmware and kernel)?

The described mechanism doesn't require trusting the code that's in the 
middle - if the state is perturbed by this code, the measurements will 
be different, and the system will be untrusted. I agree that this 
implementation is more complicated than just leaving it all up to the 
kernel, but I'm having a *lot* of trouble seeing how this has any impact 
on its security. Jumping immediately to impugning the motivation of the 
people involved is entirely inappropriate.