linux-kernel - Re: [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig

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Message-Id: <871s0i75nt.fsf@morokweng.localdomain>
Date:   Tue, 28 May 2019 16:14:30 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jessica Yu <jeyu@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        "AKASHI\, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [PATCH v10 12/12] ima: Store the measurement again when appraising a modsig


Mimi Zohar <zohar@...ux.ibm.com> writes:

> Hi Thiago,
>
> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> If the IMA template contains the "modsig" or "d-modsig" field, then the
>> modsig should be added to the measurement list when the file is appraised.
>>
>> And that is what normally happens, but if a measurement rule caused a file
>> containing a modsig to be measured before a different rule causes it to be
>> appraised, the resulting measurement entry will not contain the modsig
>> because it is only fetched during appraisal. When the appraisal rule
>> triggers, it won't store a new measurement containing the modsig because
>> the file was already measured.
>>
>> We need to detect that situation and store an additional measurement with
>> the modsig. This is done by adding an IMA_MEASURE action flag if we read a
>> modsig and the IMA template contains a modsig field.
>
> With the new per policy rule "template" support being added, this
> patch needs to be modified so that the per policy "template" format is
> checked. ima_template_has_modsig() should be called with the
> template_desc being used.

Right. Thanks for point out what needs to be done. After rebasing on top
of Matthew Garret's "IMA: Allow profiles to define the desired IMA
template" patch I changed ima_template_has_modsig() to check the
template_desc obtained from process_measurement().

--
Thiago Jung Bauermann
IBM Linux Technology Center