linux-kernel - Re: [PATCH v2 2/3] efi: call get_event

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Message-ID: <CACdnJuu2Aq1mvdvooBgC3-1jfi3CPnZ6WGysOGc2Xizm-mbU0w@mail.gmail.com>
Date:   Thu, 14 Sep 2017 11:48:54 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Thiebaud Weksteen <tweek@...gle.com>, linux-efi@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        linux-kernel@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net,
        peterhuewe@....de, jgunthorpe@...idianresearch.com,
        tpmdd@...horst.net
Subject: Re: [PATCH v2 2/3] efi: call get_event_log before ExitBootServices

On Thu, Sep 14, 2017 at 11:43 AM, Jarkko Sakkinen
<jarkko.sakkinen@...ux.intel.com> wrote:
> On Mon, Sep 11, 2017 at 12:00:21PM +0200, Thiebaud Weksteen wrote:
>> With TPM 2.0 specification, the event logs may only be accessible by
>> calling an EFI Boot Service. Modify the EFI stub to copy the log area to
>> a new Linux-specific EFI configuration table so it remains accessible
>> once booted.
>>
>> When calling this service, it is possible to specify the expected format
>> of the logs: TPM 1.2 (SHA1) or TPM 2.0 ("Crypto Agile"). For now, only the
>> first format is retrieved.
>>
>> Signed-off-by: Thiebaud Weksteen <tweek@...gle.com>
>
> With a quick skim the code change looks good but I remember from
> Matthew's talk that there was this issue that ExitBootServices() would
> cause a yet another event?
>
> I guess you could manually synthetize that event by reading the PCR
> values right after ExitBootServices()?

I think that would involve breaking SHA1… the information should be
available in the TCG_TREE_FINAL_EVENTS configuration table, so it
/should/ just be a matter of merging the events from that into the
event log.