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

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Message-ID: <87ttflli09.ffs@tglx>
Date: Thu, 15 Aug 2024 21:10:14 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: "Daniel P. Smith" <dpsmith@...rtussolutions.com>, "Eric W. Biederman"
 <ebiederm@...ssion.com>, Eric Biggers <ebiggers@...nel.org>
Cc: 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, iommu@...ts.linux-foundation.org,
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 James.Bottomley@...senpartnership.com, peterhuewe@....de,
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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 Thu, Aug 15 2024 at 13:38, Daniel P. Smith wrote:
> On 5/31/24 09:54, Eric W. Biederman wrote:
>> Eric Biggers <ebiggers@...nel.org> writes:
>>> That paragraph is also phrased as a hypothetical, "Even if we'd prefer to use
>>> SHA-256-only".  That implies that you do not, in fact, prefer SHA-256 only.  Is
>>> that the case?  Sure, maybe there are situations where you *have* to use SHA-1,
>>> but why would you not at least *prefer* SHA-256?
>> 
>> Yes.  Please prefer to use SHA-256.
>> 
>> Have you considered implementing I think it is SHA1-DC (as git has) that
>> is compatible with SHA1 but blocks the known class of attacks where
>> sha1 is actively broken at this point?
>
> We are using the kernel's implementation, addressing what the kernel 
> provides is beyond our efforts. Perhaps someone who is interested in 
> improving the kernel's SHA1 could submit a patch implementing/replacing 
> it with SHA1-DC, as I am sure the maintainers would welcome the help.

Well, someone who is interested to get his "secure" code merged should
have a vested interested to have a non-broken SHA1 implementation if
there is a sensible requirement to use SHA1 in that new "secure" code,
no?

Just for the record. The related maintainers can rightfully decide to
reject known broken "secure" code on a purely technical argument.

Thanks,

        tglx