Re: [TrouSerS-users] Regarding the PCR values

[Hal F. <hal...@gm...>]

On Wed, Mar 12, 2008 at 9:21 PM, Spark Blurr <spa...@gm...> wrote:
> Hi,
>
> I would like to find out which PCR register is being used by which entity in
> the system? I search the net and could not find any reference to what I
> want.
>
> Thanks,
> spark

Hi Spark - Take a look at the TCG's PC Client specifications at
https://www.trustedcomputinggroup.org/specs/PCClient/ . Specifically
the TCG PC Client Specific Implementation Specification for
Conventional Bios section 3.2.3 which discusses the use of the PCRs by
the BIOS in some detail.

If you are interested in the use of the higher numbered PCRs 16-23,
and you understand the notion of locality, section 3.2.4 in that
document goes into that somewhat. Also the TCG PC Client Specific TPM
Interface Specification (TIS) document from that same directory,
section 7 discusses these PCRs in more detail.

PCRs 8-15 are for the use of the OS, and I don't know of any spec that
defines what an OS might do with them. These days there is much
interest in using TPMs for secure virtualization so it may turn out
that the OS and VMM have to share these (depending on whether advanced
TPM-aware hardware virtualization is in use). IBM has a Linux kernel
patch and client code for their Integrity Measurement Architecture
(IMA) which will hash every executable into a PCR before it runs,
http://sourceforge.net/projects/linux-ima . It measures everything
into PCR 10 by default - overridable with the kernel config option
IMA_MEASURE_PCR_IDX.

Hal Finney