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

Thomas Gleixner
2024-08-15T19:10:22Z

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@kernel.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