Re: [PATCH v9 06/19] x86: Add early SHA-1 support for Secure Launch early measurements

ross.philipson
2024-08-28T20:16:06Z

On 8/27/24 11:14 AM, 'Eric Biggers' via trenchboot-devel wrote:
> On Thu, May 30, 2024 at 07:16:56PM -0700, Eric Biggers wrote:
>> On Thu, May 30, 2024 at 06:03:18PM -0700, Ross Philipson wrote:
>>> From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
>>>
>>> For better or worse, Secure Launch needs SHA-1 and SHA-256. The
>>> choice of hashes used lie with the platform firmware, not with
>>> software, and is often outside of the users control.
>>>
>>> Even if we'd prefer to use SHA-256-only, if firmware elected to start us
>>> with the SHA-1 and SHA-256 backs active, we still need SHA-1 to parse
>>> the TPM event log thus far, and deliberately cap the SHA-1 PCRs in order
>>> to safely use SHA-256 for everything else.
>>>
>>> The SHA-1 code here has its origins in the code from the main kernel:
>>>
>>> commit c4d5b9ffa31f ("crypto: sha1 - implement base layer for SHA-1")
>>>
>>> A modified version of this code was introduced to the lib/crypto/sha1.c
>>> to bring it in line with the SHA-256 code and allow it to be pulled into the
>>> setup kernel in the same manner as SHA-256 is.
>>>
>>> Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
>>> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
>>
>> Thanks. This explanation doesn't seem to have made it into the actual code or
>> documentation. Can you please get it into a more permanent location?
>
> I see that a new version of the patchset was sent out but this suggestion was
> not taken. Are you planning to address it?

Sorry we sort of overlooked that part of the request. We will take the
latest commit message, clean it up a little and put it in
boot/compressed/sha1.c file as a comment. I believe that is what you
would like us to do.

Thanks
Ross

>
> - Eric
>