linux-kernel - Re: [PATCH 0/3] support for duplicate measurement of integrity critical data

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Message-ID: <27f73411fc1d6ce6dd16a29344d729d9aa760250.camel@linux.ibm.com>
Date:   Mon, 08 Feb 2021 15:22:54 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Tushar Sugandhi <tusharsu@...ux.microsoft.com>,
        stephen.smalley.work@...il.com, casey@...aufler-ca.com,
        agk@...hat.com, snitzer@...hat.com, gmazyland@...il.com,
        paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH 0/3] support for duplicate measurement of integrity
 critical data

Hi Tushar,

On Fri, 2021-01-29 at 16:45 -0800, Tushar Sugandhi wrote:
> IMA does not measure duplicate buffer data since TPM extend is a very
> expensive operation.  However, in some cases for integrity critical
> data, 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 integrity critical data on the
> system.
> 
> This series addresses this gap by providing the ability to measure
> duplicate entries for integrity critical data, driven by policy.

The same reason for re-measuring buffer data is equally applicable to
files.  In both cases, the file or the buffer isn't re-measured if it
already exists in the htable.   Please don't limit this patch set to
just buffer data.

thanks,

Mimi