[tpm2] Re: tpm2_eventlog ERROR: SpecID eventType must be EV_NO_ACTION

From: Kenneth Goldman <kgoldman at us.ibm.com>
To: tpm2@lists.01.org
Subject: [tpm2] Re: tpm2_eventlog ERROR: SpecID eventType must be EV_NO_ACTION
Date: Thu, 15 Apr 2021 15:37:23 -0400	[thread overview]
Message-ID: <OF390046DF.F4A70955-ON002586B8.006B4F6E-852586B8.006BCB08@notes.na.collabserv.com> (raw)
In-Reply-To: 20210415182554.2848.69001@ml01.vlan13.01.org

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In theory, the BIOS event log is constructed pre-OS, and certainly the
beginning part should not be affected.

If you're booting two different kernels and the first event changes, my
first guess is that something in the kernel is affecting the pseudo-file
and skipping or deleting the first measurement.  "Customized Linux kernel"
sounds suspicious.

I think you might have a better audience on the Linux security mailing
list.

--
Ken Goldman   kgoldman(a)us.ibm.com
914-945-2415 (862-2415)

From:	nicolasoliver03(a)gmail.com
To:	tpm2(a)lists.01.org
Date:	04/15/2021 02:26 PM
Subject:	[EXTERNAL] [tpm2] Re: tpm2_eventlog ERROR: SpecID eventType
            must be EV_NO_ACTION

Hello again,

I have been debugging this issue with the manufacturer for a couple of
days, and found something very interesting.
Initially, I thought it was a System Firmware (BIOS) problem, that it was
misbehaving and reporting an invalid log.
But it seems to be a Kernel related problem.

If the system is booted with a customized Linux Kernel 4.19, the TPM Event
Log present in sysfs is invalid: tools fails to parse it, and there are no
SHA256 measurements.
If the system is booted with a vanilla Linux Kernel 5.8.15 (Fedora
Workstation 33 Live), the TPM Event Log is valid, tools can parse it, there
are both SHA1 and SHA256 measurements, and the reconstruction matches
perfectly with the state of the TPM PCRs

This is more evident by comparing the binary_bios_measurements files taken
from both executions. I can see the good one starting with "Spec ID Ev..",
and the bad one directly with "Secure Boot" related info

The git history of the kernel source related to TPM Event Log is available
here
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/drivers/char/tpm/eventlog
 .
I will look there to see if something shed some light to this issue.

Any hints are appreciated,

Thank you for your help so far!
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