Messages in this thread | | | Subject | Re: [PATCH v2] IMA: support for duplicate data measurement | From | Tushar Sugandhi <> | Date | Wed, 17 Feb 2021 12:49:37 -0800 |
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On 2021-02-17 12:39 p.m., Mimi Zohar wrote: > On Wed, 2021-02-17 at 10:53 -0800, Tushar Sugandhi wrote: >> Thanks for the feedback Mimi. >> Appreciate it. >> >> On 2021-02-17 7:03 a.m., Mimi Zohar wrote: >>> Hi Tushar, >>> >>> The Subject line could be improved. Perhaps something like - "IMA: >>> support for duplicate measurement records" >>> >> Will do. >> >>> On Tue, 2021-02-16 at 18:46 -0800, Tushar Sugandhi wrote: >>>> IMA does not measure duplicate data since TPM extend is a very expensive >>>> operation. However, in some cases, the measurement of duplicate data >>>> is necessary to accurately determine the current state of the system. >>>> Eg, SELinux state changing from 'audit', to 'enforcing', and back to >>>> 'audit' again. In this example, currently, IMA will not measure the >>>> last state change to 'audit'. This limits the ability of attestation >>>> services to accurately determine the current state of the measurements >>>> on the system. >>> >>> This patch description is written from your specific usecase >>> perspective, but it impacts file and buffer data measurements as well, >>> not only critical data measurements. In all of these situations, with >>> this patch a new measurement record is added/appended to the >>> measurement list. Please re-write the patch description making it more >>> generic. >>> >>> For example, I would start with something like, "IMA does not include >>> duplicate file, buffer or critical data measurement records ..." >>> >> Agreed. >> I will generalize the description further and send the v3 for review. > > It would be good to boot with the ima_policy=tcb policy with/without > your patch and account for the different number of measurements. Are > all the differences related to duplicate measurements - original file > hash -> new file hash -> original file hash - similar to what you > described. > Thanks for the ima_policy=tcb pointer.
I tested my patch with: - duplicate buffer content for "measure func=CRITICAL_DATA" - and reading the same file twice with "measure func=FILE_CHECK mask=MAY_READ"
In both the above use cases, IMA is measuring the duplicate entries with the patch, and not measuring the duplicate entries w/o the patch.
I will test the "ima_policy=tcb" boot-scenario as you suggested, before posting the next version.
Thanks, Tushar
> thanks, > > Mimi >
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