linux-kernel - Re: [PATCH v2] IMA: support for duplicate data measurement

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Date:   Wed, 17 Feb 2021 10:03:55 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Tushar Sugandhi <tusharsu@...ux.microsoft.com>
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] IMA: support for duplicate data measurement

Hi Tushar,

The Subject line could be improved.  Perhaps something like - "IMA:
support for duplicate measurement records"

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 ..."

thanks,

Mimi

> 
> Update ima_add_template_entry() to support measurement of duplicate
> data, driven by a Kconfig option - IMA_DISABLE_HTABLE.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>