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

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Message-ID: <20170914190247.rrbdzdexjjywxipf@linux.intel.com>
Date:   Thu, 14 Sep 2017 12:02:47 -0700
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Matthew Garrett <mjg59@...gle.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 11:48:54AM -0700, Matthew Garrett wrote:
> 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

You are absolutely right, was not thinking clearly :-)

> 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.

Right, it is available through runtime services. Why this isn't part
of the patch set?

/Jrakko

/Jarkko