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From:   Matthew Garrett <mgarrett@aurora.tech>
Date:   Mon, 29 Aug 2022 14:51:50 -0700
Message-ID: <CAHSSk06+CNQLKS8p_jh8JH7acn6=Ck8W3W2DM75rV3paZQ+MbA@mail.gmail.com>
Subject: Re: TPM: hibernate with IMA PCR 10
To:     Ken Goldman <kgold@linux.ibm.com>
Cc:     Evan Green <evgreen@chromium.org>, linux-kernel@vger.kernel.org,
        dlunev@google.com, zohar@linux.ibm.com, jejb@linux.ibm.com,
        linux-integrity@vger.kernel.org, corbet@lwn.net, rjw@rjwysocki.net,
        gwendal@chromium.org, jarkko@kernel.org, linux-pm@vger.kernel.org,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        "Rafael J. Wysocki" <rafael@kernel.org>
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On Mon, Aug 29, 2022 at 2:45 PM Ken Goldman <kgold@linux.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.