[PATCH] lsm: drop LSM_ID_IMA

[Paul Moore]

On Wed, Oct 25, 2023 at 6:36 AM Roberto Sassu
<roberto.sassu at huaweicloud.com> wrote:
> On 10/24/2023 11:18 PM, Paul Moore wrote:
> > On Mon, Oct 23, 2023 at 11:48 AM Casey Schaufler <casey at schaufler-ca.com> wrote:
> >> On 10/23/2023 8:20 AM, Roberto Sassu wrote:
> >>> On 10/20/2023 11:56 PM, Casey Schaufler wrote:
> >>>> On 10/19/2023 1:08 AM, Roberto Sassu wrote:
> >>>>> On Wed, 2023-10-18 at 17:50 -0400, Paul Moore wrote:
> >>>>>> When IMA becomes a proper LSM we will reintroduce an appropriate
> >>>>>> LSM ID, but drop it from the userspace API for now in an effort
> >>>>>> to put an end to debates around the naming of the LSM ID macro.
> >>>>>>
> >>>>>> Signed-off-by: Paul Moore <paul at paul-moore.com>
> >>>>> Reviewed-by: Roberto Sassu <roberto.sassu at huawei.com>
> >>>>>
> >>>>> This makes sense according to the new goal of making 'ima' and 'evm' as
> >>>>> standalone LSMs.
> >>>>>
> >>>>> Otherwise, if we took existing LSMs, we should have defined
> >>>>> LSM_ID_INTEGRITY, associated to DEFINE_LSM(integrity).
> >>>>>
> >>>>> If we proceed with the new direction, I will add the new LSM IDs as
> >>>>> soon as IMA and EVM become LSMs.
> >>>>
> >>>> This seems right to me. Thank You.
> >>>
> >>> Perfect! Is it fine to assign an LSM ID to 'ima' and 'evm' and keep
> >>> the 'integrity' LSM to reserve space in the security blob without LSM
> >>> ID (as long as it does not register any hook)?
> >>
> >> That will work, although it makes me wonder if all the data in the 'integrity' blob
> >> is used by both IMA and EVM. If these are going to be separate LSMs they should probably
> >> have their own security blobs. If there is data in common then an 'integrity' blob can
> >> still makes sense.
> >
> > Users interact with IMA and EVM, not the "integrity" layer, yes?  If
> > so, I'm not sure it makes sense to have an "integrity" LSM, we should
> > just leave it at "IMA" and "EVM".
>
> The problem is who reserves and manages the shared integrity metadata.
> For now, it is still the 'integrity' LSM. If not, it would be IMA or EVM
> on behalf of the other (depending on which ones are enabled). Probably
> the second would not be a good idea.

I'm not certain that managing kernel metadata alone necessitates a LSM
ID token value.  Does "integrity" have any user visible "things" that
it would want to expose to userspace?

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