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([2601:646:c200:1ef2:d9a3:6ef8:19c1:abf4]) by smtp.gmail.com with ESMTPSA id i26sm536576pfo.0.2020.06.01.17.49.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jun 2020 17:49:06 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [GRUB PATCH RFC 00/18] i386: Intel TXT secure launcher Date: Mon, 1 Jun 2020 17:49:03 -0700 Message-Id: References: Cc: Andy Lutomirski , Daniel Kiper , Lukasz Hawrylko , grub-devel@gnu.org, LKML , trenchboot-devel@googlegroups.com, X86 ML , alexander.burmashev@oracle.com, Andrew Cooper , Ard Biesheuvel , eric.snowberg@oracle.com, javierm@redhat.com, kanth.ghatraju@oracle.com, Konrad Rzeszutek Wilk , krystian.hebel@3mdeb.com, michal.zygowski@3mdeb.com, Matthew Garrett , phcoder@gmail.com, piotr.krol@3mdeb.com, Peter Jones , Ross Philipson In-Reply-To: To: "Daniel P. Smith" X-Mailer: iPhone Mail (17E262) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 1, 2020, at 5:14 PM, Daniel P. Smith = wrote: >=20 > =EF=BB=BFOn 6/1/20 3:39 PM, Andy Lutomirski wrote: >>>> . >=20 > In other words, the log for the relaunch to attest what is currently > running is really no less useful than using the first launch log to > attest to the what was running in the first launch. >=20 Maybe it would help if you give some examples of what=E2=80=99s actually in t= his log and why anyone, Linux or otherwise, cares for any purpose other than= debugging. We=E2=80=99re talking about a log written by something like GRU= B, right? If so, I=E2=80=99m imagining things like: GRUB: loading such-and-such module GRUB: loading the other module GRUB: loading Linux at /boot/vmlinuz-whatever GRUB: about to do the DRTM launch. Bye-bye. This is surely useful for debugging. But, if I understand your security mod= el correctly, it=E2=80=99s untrustworthy in the sense that this all comes fr= om before the DRTM launch and it could have been tampered with by SMM code o= r even just a malicious USB stick. Or even a malicious compromised kernel o= n the same machine. So you could hash this log into a PCR, but I don=E2=80=99= t see what you=E2=80=99ve accomplished by doing so. Or have I misunderstood what this log is? Perhaps you=E2=80=99re talking ab= out something else entirely.=