linux-kernel - Re: [PATCH v2 06/15] ima: add parser of digest lists metadata

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Date:   Mon, 20 Nov 2017 10:52:06 -0600
From:   "Serge E. Hallyn" <serge@...lyn.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     Roberto Sassu <roberto.sassu@...wei.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, silviu.vlasceanu@...wei.com
Subject: Re: [PATCH v2 06/15] ima: add parser of digest lists metadata

Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> On Mon, 2017-11-20 at 10:40 +0100, Roberto Sassu wrote:
> > On 11/19/2017 12:23 AM, Mimi Zohar wrote:
> > > Hi Serge,
> > > 
> > > On Fri, 2017-11-17 at 22:20 -0600, Serge E. Hallyn wrote:
> > >> On Tue, Nov 07, 2017 at 11:37:01AM +0100, Roberto Sassu wrote:
> > >>> from a predefined position (/etc/ima/digest_lists/metadata), when rootfs
> > >>> becomes available. Digest lists must be loaded before IMA appraisal is in
> > >>> enforcing mode.
> > >>
> > >> I'm sure there's a good reason for it, but this seems weird to me.
> > >> Why read it from a file on disk instead of accepting it through say
> > >> a securityfile write?
> > 
> > There are two reasons.
> > 
> > Digest lists must be loaded before any file is accessed, otherwise IMA
> > will deny the operation if appraisal is in enforcing mode. With digest
> > lists it is possible to appraise files in the initial ram disk without
> > including extended attributes (the default policy excludes those files).
> 
> There are a number of people interested in extending CPIO to support
> extended attributes, not just for IMA-appraisal. (Years ago I started
> but unfortunately haven't had time to finish it.)  Isn't the right
> solution to add extended attribute support to CPIO?

(For the record) Yes, yes it is.