linux-kernel - Re: [PATCH v1 3/5] ima: limit including fs-verity's file digest in measurement list

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Date:   Thu, 02 Dec 2021 17:55:59 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-integrity@...r.kernel.org, linux-fscrypt@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/5] ima: limit including fs-verity's file digest in
 measurement list

On Thu, 2021-12-02 at 14:22 -0800, Eric Biggers wrote:
> On Thu, Dec 02, 2021 at 04:55:05PM -0500, Mimi Zohar wrote:
> > Without the file signature included in the IMA measurement list, the type
> > of file digest is unclear.  Set up the plumbing to limit including
> > fs-verity's file digest in the IMA measurement list based on whether the
> > template name is ima-sig.  In the future, this could be relaxed to include
> > any template format that includes the file signature.
> > 
> 
> Does it make sense to tie IMA's fs-verity support to files having signatures?
> What about IMA audit mode?  I thought that is just about collecting hashes, and
> has nothing to do with signatures.

There's IMA-measurement, IMA-audit, and IMA-appraisal.  IMA-audit
refers to adding the file hash to the audit log record.  IMA-
measurement stores the collected hash in the IMA measurement list and
extends the TPM with the measurement, if there's a TPM.  Based on
policy, determines whether the file is measured, audited, and/or
appraised.  I actually do think it makes sense to require a signature,
but not necessarily enforce signature verification, in order to
differentiate the type of measurement being included in the measurement
list.

thanks,

Mimi