linux-kernel - Re: [RFCv2 0/9] UEFI emulator for kexec

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Message-ID: <ZsyFr8V6yizMiBTw@gardel-login>
Date: Mon, 26 Aug 2024 15:39:59 +0200
From: Lennart Poettering <mzxreary@...inter.de>
To: Pingfan Liu <piliu@...hat.com>
Cc: Ard Biesheuvel <ardb@...nel.org>, Jan Hendrik Farr <kernel@...rr.cc>,
	Philipp Rudo <prudo@...hat.com>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Eric Biederman <ebiederm@...ssion.com>, Baoquan He <bhe@...hat.com>,
	Dave Young <dyoung@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Will Deacon <will@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	kexec@...ts.infradead.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFCv2 0/9] UEFI emulator for kexec

On Do, 22.08.24 22:29, Pingfan Liu (piliu@...hat.com) wrote:

> > Hmm, I'd really think about this with some priority. The measurement
> > stuff should not be an afterthought, it typically has major
> > implications on how you design your transitions, because measurements
> > of some component always need to happen *before* you pass control to
> > it, otherwise they are pointless.
> >
>
> At present, my emulator returns false to is_efi_secure_boot(), so
> systemd-stub does not care about the measurement, and moves on.
>
> Could you enlighten me about how systemd utilizes the measurement? I
> grepped 'TPM2_PCR_KERNEL_CONFIG', and saw the systemd-stub asks to
> extend PCR. But where is the value checked? I guess the systemd will
> hang if the check fails.

systemd's "systemd-pcrlock" tool will look for measurements like that
and generate disk encryption TPM policies from that.

Lennart

--
Lennart Poettering, Berlin