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

Eric Biggers
2024-08-27T18:14:29Z

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?

- Eric