Re: [PATCH v1 3/3] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

Eric Biggers
2021-04-01T06:04:23Z

On Thu, Apr 01, 2021 at 08:50:05AM +0300, Jarkko Sakkinen wrote:
> On Thu, Apr 01, 2021 at 12:11:32PM +1100, Herbert Xu wrote:
> > On Wed, Mar 31, 2021 at 04:34:29PM -0700, Eric Biggers wrote:
> > > On Thu, Apr 01, 2021 at 02:31:46AM +0300, Jarkko Sakkinen wrote:
> > > >
> > > > It's a bummer but uapi is the god in the end. Since TPM does not do it
> > > > today, that behaviour must be supported forever. That's why a boot option
> > > > AND a warning would be the best compromise.
> > >
> > > It's not UAPI if there is no way for userspace to tell if it changed.
> >
> > Exactly. UAPI is only an issue if something *breaks*.
>
> If there's even one user that comes shouting that he has a user space
> configuration, where e.g. rng entropy is consumed constantly and the
> code assumes that trusted keys does not add to that, then something
> would break.
>
> It would be a crap user space yes, but I don't want to go on reverting
> because of that. I think there is small but still existing chance that
> something could break.

random.c no longer provides any interfaces that subtract entropy credits, as
that was never something that made sense. So "consuming" all the entropy from
random.c isn't a thing anymore.

>
> Why not just add a boot parameter instead of making brutal enforcing
> changes, indirectly visible to the user space?

Why not just fix this bug instead of providing an option to fix it that everyone
will need to remember to provide?

- Eric