On Mon, 2020-06-15 at 11:47 -0400, Stephen Smalley wrote: > On Mon, Jun 15, 2020 at 10:59 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote: > > > > On Mon, 2020-06-15 at 09:33 -0400, Stephen Smalley wrote: > > > On Fri, Jun 12, 2020 at 10:42 PM Lakshmi Ramasubramanian > > > <nramas@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > The data maintained by the security modules could be tampered with by > > > > malware. The LSM needs to periodically query the state of > > > > the security modules and measure the data when the state is changed. > > > > > > > > Define a workqueue for handling this periodic query and measurement. > > > > > > Won't this make it difficult/impossible to predict the IMA PCR value? > > > Unless I missed it, you are going to end up measuring every N minutes > > > even if there was no change and therefore constantly be extending the > > > PCR. That will break attestation or sealing against the IMA PCR. > > > > Even if it attempts to add the same measurement to the list multiple > > times, unless something changed, there should only be one measurement > > in the list. > > Is the PCR only extended once? Yes, otherwise you wouldn't be able to verify a quote. ima_lookup_digest_entry() first verifies the hash isn't in the cache, before adding it to the measurement list and then extending the TPM. Mimi
