linux-kernel - Re: [PATCH v6 0/3] IMA: Deferred measurement of keys

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Message-Id: <1578064099.5874.170.camel@linux.ibm.com>
Date:   Fri, 03 Jan 2020 10:08:19 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        James.Bottomley@...senPartnership.com,
        linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        mathew.j.martineau@...ux.intel.com, matthewgarrett@...gle.com,
        sashal@...nel.org, jamorris@...ux.microsoft.com,
        linux-kernel@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH v6 0/3] IMA: Deferred measurement of keys

Hi Lakshmi,

Instead of loosing the cover letter, Jonathan Corbet suggested
including it as the merge comment.  I'd like to do that with this
cover letter.

On Thu, 2020-01-02 at 21:56 -0800, Lakshmi Ramasubramanian wrote:
> This patchset extends the previous version[1] by adding support for
> deferred processing of keys.
> 
> With the patchset referenced above, the IMA subsystem supports
> measuring asymmetric keys when the key is created or updated.

The first sentence and the clause of the next sentence are
unnecessary.  I would begin the cover letter with "The IMA subsystem
supports" and add the reference afterwards.

> But keys created or updated before a custom IMA policy is loaded
> are currently not measured. This includes keys added to, for instance,
> .builtin_trusted_keys which happens early in the boot process.

Let's not limit the example to just the .builtin_trusted_keys keyring.
 Please update it as:

This includes keys added, for instance, to either the .ima or
.builtin_trusted_keys keyrings, which happens early in the boot
process.

> 
> This change adds support for queuing keys created or updated before
> a custom IMA policy is loaded. The queued keys are processed when
> a custom policy is loaded. Keys created or updated after a custom policy
> is loaded are measured immediately (not queued).
> 
> If the kernel is built with both CONFIG_IMA and
> CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE enabled then the IMA policy
> must be applied as a custom policy for the keys to be measured.
> If a custom IMA policy is not provided within 5 minutes after
> IMA is initialized, any queued keys will be freed.

As the merge message, this is too much information.  I would extend
the previous paragraph and drop this one, like:
"... (not queued).  In the case when a custom policy is not loaded
within 5 minutes of IMA initialization, the queued keys are freed."

> This is by design.

It's unclear what "is by design" refers to.  Perhaps expand this
sentence like: "Measuring the early boot keys, by design, requires
loading a custom policy.

> 
> [1] https://lore.kernel.org/linux-integrity/20191211164707.4698-1-nramas@linux.microsoft.com/

thanks,

Mimi