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

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Message-ID: <601646a2-46ac-47a0-a8b7-1d45a09172ab@oracle.com>
Date: Wed, 28 Aug 2024 13:14:45 -0700
From: ross.philipson@...cle.com
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
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        dpsmith@...rtussolutions.com, tglx@...utronix.de, mingo@...hat.com,
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        trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v9 06/19] x86: Add early SHA-1 support for Secure Launch
 early measurements

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@...rtussolutions.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@...rtussolutions.com>
>>> Signed-off-by: Ross Philipson <ross.philipson@...cle.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
>