[RFC V2] IMA Log Snapshotting Design Proposal

[Mimi Zohar]

On Tue, 2023-11-21 at 17:01 -0800, Tushar Sugandhi wrote:
> Hi Mimi,
> To address your concern about pausing the measurements -
> We are not proposing to pause the measurements for the entire duration
> of UM <--> Kernel interaction while taking a snapshot.
> 
> We are simply proposing to pause the measurements when we get the TPM
> PCR quotes to add them to "snapshot_aggregate". (which should be a very
> small time window). IMA already has this mechanism when two separate
> modules try to add entry to IMA log - by using
> mutex_lock(&ima_extend_list_mutex); in ima_add_template_entry.
> 
> 
> We plan to use this existing locking functionality.
> Hope this addresses your concern about pausing extending the measurement
> list.

Each TPM PCR read is a separate TPM command.  Have you done any
performance anlaysis to see how long it actually takes to calculate the
"snapshot_aggregate" with a physical TPM?

The "snapshot_aggregate" is a new critical-data and should be
upstreamed independently of this patch set.

-- 
thanks,

Mimi