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SubjectRe: [PATCH v2 2/3] efi: call get_event_log before ExitBootServices
On Thu, Sep 14, 2017 at 12:02:47PM -0700, Jarkko Sakkinen wrote:
> 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@linux.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@google.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?

Anyway, I'll try this out out when I get back to Finland. Still before
landing this to mainline I think it would make sense to make it complete
wouldn't it?

/Jarkko

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