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:

quoted

Eric Biggers [off-list ref] writes:

quoted

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