RE: [RFC PATCH 00/30] ima: Introduce IMA namespace

Krzysztof Struczynski
2020-09-14T12:06:18Z

> From: Mimi Zohar [mailto:zohar@linux.ibm.com]
> Sent: Wednesday, September 2, 2020 8:53 PM
> > > So I think this can work in the use case where the system owner is
> > > responsible for doing the logging and attestation and the tenants just
> > > trust the owner without requiring an attestation. However, in a multi-
> > > tenant system you need a way for the attestation to be per-container
> > > (because the combined list of who executed what would be a security
> > > leak between tenants). Since we can't virtualise the PCRs without
> > > introducing a vtpm this is going to require a vtpm infrastructure like
> > > that used for virtual machines and then we can do IMA logging per
> > > container.
> >
> > I agree and wonder if we should decouple the attestation trust model,
> > which depends on the specific use case (e.g. multi/single tenant,
> > public/private cloud), from the IMA logic of linking the measurements to
> > the container. Indeed, attestation from within the container might require
> > anchoring to a vTPM/vPCR and the current measurement tagging mechanism
> can
> > support several ways of anchoring them to a (virtual) root of trust.
> >
> > > I don't think the above has to be in your first patch set, we just have
> > > to have an idea of how it could be done to show that nothing in this
> > > patch set precludes a follow on from doing this.
> >
> > Given that virtualizing trust anchors seems like a separate problem in
> > which industry consensus is not easy to reach for all use cases, an
> > anchoring mechanism should probably be a separate IMA feature.
>
> Other trust anchors for "trusted keys" has been discussed, but I wasn't
> aware of any discussion about other trust anchors for the IMA
> measurement list. The IMA measurement list is very much tied to a TPM.
>

Agreed. I wouldn't consider anything else than the TPM in the IMA
measurement list context. The anchoring mechanism mentioned above
pertained to the possible extensions of the TPM anchor in the
containerized environment, like the vTPM.

> Including container measurements in the host measurement list, will
> unnecessarily cause the host measurement list to grow. The decision of
> what should and shouldn't be included in the host measurement list
> shouldn't be defined by the container.
>

The container has no impact on the measurement list entries other than the
ones related to the processes running within the container. This in turn,
the same as for the original IMA, is defined by the (container's) policy,
loaded on the container's creation.

Best regards,
Krzysztof

> Mimi