On Mon, Aug 19, 2024 at 09:05:47PM +0300, Jarkko Sakkinen wrote:

On Fri Aug 16, 2024 at 9:41 PM EEST, Matthew Garrett wrote:

quoted

On Fri, Aug 16, 2024 at 02:22:04PM +0300, Jarkko Sakkinen wrote:

quoted

For (any) non-legacy features we can choose, which choices we choose to
support, and which we do not. This is not an oppositive view just saying
how it is, and platforms set of choices is not a selling argument.

NIST still permits the use of SHA-1 until 2030, and the most significant 
demonstrated weaknesses in it don't seem applicable to the use case 
here. We certainly shouldn't encourage any new uses of it, and anyone 
who's able to use SHA-2 should be doing that instead, but it feels like 
people are arguing about not supporting hardware that exists in the real 
world for vibes reasons rather than it being a realistically attackable 
weakness (and if we really *are* that concerned about SHA-1, why are we 
still supporting TPM 1.2 at all?)

We are life-supporting TPM 1.2 as long as necessary but neither the
support is extended nor new features will gain TPM 1.2 support. So
that is at least my policy for that feature.

But the fact that we support it and provide no warning labels is a 
pretty clear indication that we're not actively trying to prevent people 
from using SHA-1 in the general case. Why is this a different case? 
Failing to support it actually opens an entire separate set of footgun 
opportunities in terms of the SHA-1 banks now being out of sync with the 
SHA-2 ones, so either way we're leaving people open to making poor 
choices.