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

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Message-ID: <5236e03f-9be4-f7f3-ec6c-29f00c16dc18@linux.microsoft.com>
Date:   Wed, 17 Feb 2021 10:53:40 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.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

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.

Thanks,
Tushar

> 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>