linux-kernel - Re: TPM: hibernate with IMA PCR 10

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Date:   Mon, 29 Aug 2022 14:51:50 -0700
From:   Matthew Garrett <mgarrett@...ora.tech>
To:     Ken Goldman <kgold@...ux.ibm.com>
Cc:     Evan Green <evgreen@...omium.org>, linux-kernel@...r.kernel.org,
        dlunev@...gle.com, zohar@...ux.ibm.com, jejb@...ux.ibm.com,
        linux-integrity@...r.kernel.org, corbet@....net, rjw@...ysocki.net,
        gwendal@...omium.org, jarkko@...nel.org, linux-pm@...r.kernel.org,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: TPM: hibernate with IMA PCR 10

On Mon, Aug 29, 2022 at 2:45 PM Ken Goldman <kgold@...ux.ibm.com> wrote:
>
> On 5/4/2022 7:20 PM, Evan Green wrote:
> > Enabling the kernel to be able to do encryption and integrity checks on
> > the hibernate image prevents a malicious userspace from escalating to
> > kernel execution via hibernation resume.  [snip]
>
> I have a related question.
>
> When a TPM powers up from hibernation, PCR 10 is reset.  When a
> hibernate image is restored:
>
> 1. Is there a design for how PCR 10 is restored?

I don't see anything that does that at present.

> 2. How are /sys/kernel/security/ima/[pseudofiles] saved and
> restored?

They're part of the running kernel state, so should re-appear without
any special casing. However, in the absence of anything repopulating
PCR 10, they'll no longer match the in-TPM value.