linux-kernel - Re: [PATCH v8 06/15] x86: Add early SHA support for Secure Launch early measurements

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Message-ID: <20240223183004.GE1112@sol.localdomain>
Date: Fri, 23 Feb 2024 10:30:04 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Ard Biesheuvel <ardb@...nel.org>,
	Ross Philipson <ross.philipson@...cle.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-crypto@...r.kernel.org, kexec@...ts.infradead.org,
	linux-efi@...r.kernel.org, dpsmith@...rtussolutions.com,
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
	dave.hansen@...ux.intel.com, mjg59@...f.ucam.org,
	James.Bottomley@...senpartnership.com, peterhuewe@....de,
	jarkko@...nel.org, jgg@...pe.ca, luto@...capital.net,
	nivedita@...m.mit.edu, herbert@...dor.apana.org.au,
	davem@...emloft.net, kanth.ghatraju@...cle.com,
	trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v8 06/15] x86: Add early SHA support for Secure Launch
 early measurements

On Fri, Feb 23, 2024 at 06:20:27PM +0000, Andrew Cooper wrote:
> On 23/02/2024 5:54 pm, Eric Biggers wrote:
> > On Fri, Feb 23, 2024 at 04:42:11PM +0000, Andrew Cooper wrote:
> >> Yes, and I agree.  We're not looking to try and force this in with
> >> underhand tactics.
> >>
> >> But a blind "nack to any SHA-1" is similarly damaging in the opposite
> >> direction.
> >>
> > Well, reviewers have said they'd prefer that SHA-1 not be included and given
> > some thoughtful reasons for that.  But also they've given suggestions on how to
> > make the SHA-1 support more palatable, such as splitting it into a separate
> > patch and giving it a proper justification.
> >
> > All suggestions have been ignored.
> 
> The public record demonstrates otherwise.
> 
> But are you saying that you'd be happy if the commit message read
> something more like:
> 
> ---8<---
> 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.
> ---

Please take some time to read through the comments that reviewers have left on
previous versions of the patchset.

- Eric