Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220329174057.GA17778@srcf.ucam.org> <f9622b47-c45f-8c91-cb85-e5db7fd541cf@apertussolutions.com>
 <CAMj1kXEUT8BK_akqjF1Wx0JkLniFyV_h9s1TfQnPqfxCHsKfWw@mail.gmail.com> <7aab2990-9c57-2456-b08d-299ae96ac919@apertussolutions.com>
In-Reply-To: <7aab2990-9c57-2456-b08d-299ae96ac919@apertussolutions.com>
From:   Brendan Trotter <btrotter@gmail.com>
Date:   Wed, 6 Jul 2022 09:33:23 +0930
Message-ID: <CAELHeEfZ-feZnexp7Gx3VAJPerENcoO1Uccbe3xxUX95jvLUdA@mail.gmail.com>
Subject: Re: Linux DRTM on UEFI platforms
To:     The development of GNU GRUB <grub-devel@gnu.org>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Matthew Garrett <mjg59@srcf.ucam.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>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi,

On Wed, Jul 6, 2022 at 4:52 AM Daniel P. Smith
<dpsmith@apertussolutions.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