linux-kernel - Re: Linux DRTM on UEFI platforms

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Message-ID: <CAELHeEfZ-feZnexp7Gx3VAJPerENcoO1Uccbe3xxUX95jvLUdA@mail.gmail.com>
Date:   Wed, 6 Jul 2022 09:33:23 +0930
From:   Brendan Trotter <btrotter@...il.com>
To:     The development of GNU GRUB <grub-devel@....org>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Alec Brown <alec.r.brown@...cle.com>,
        Kanth Ghatraju <kanth.ghatraju@...cle.com>,
        Ross Philipson <ross.philipson@...cle.com>,
        "piotr.krol@...eb.com" <piotr.krol@...eb.com>,
        "krystian.hebel@...eb.com" <krystian.hebel@...eb.com>,
        "persaur@...il.com" <persaur@...il.com>,
        "Yoder, Stuart" <stuart.yoder@....com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        "michal.zygowski@...eb.com" <michal.zygowski@...eb.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        "lukasz@...rylko.pl" <lukasz@...rylko.pl>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        James Morris <jmorris@...ei.org>
Subject: Re: Linux DRTM on UEFI platforms

Hi,

On Wed, Jul 6, 2022 at 4:52 AM Daniel P. Smith
<dpsmith@...rtussolutions.com> wrote:
> On 6/10/22 12:40, Ard Biesheuvel wrote:> On Thu, 19 May 2022 at 22:59,
> To help provide clarity, consider the following flows for comparison,
>
> Normal/existing efi-stub:
>   EFI -> efi-stub -> head_64.S
>
> Proposed secure launch:
>   EFI -> efi-stub -> dl-handler -> [cpu] -> sl_stub ->head_64.S

For more clarity; the entire point is to ensure that the kernel only
has to trust itself and the CPU/TPM hardware (and does not have to
trust a potentially malicious boot loader)..Any attempt to avoid a
one-off solution for Linux is an attempt to weaken security.

The only correct approach is "efi-stub -> head_64.S -> kernel's own
secure init"; where (on UEFI systems) neither GRUB nor Trenchboot has
a valid reason to exist and should never be installed.


Cheers,

Brendan