linux-kernel - Re: [PATCH 2/6] integrity: Linux Integrity Module(LIM)

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Message-ID: <20081204192412.GA22390@hallyn.com>
Date:	Thu, 4 Dec 2008 13:24:12 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Morris <jmorris@...ei.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	David Safford <safford@...son.ibm.com>,
	Serge Hallyn <serue@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 2/6] integrity: Linux Integrity Module(LIM)

Quoting Christoph Hellwig (hch@...radead.org):
> On Wed, Dec 03, 2008 at 05:17:35PM -0500, Mimi Zohar wrote:
> > > I have a bit of a problem parsing the above, and it certainly doesn't
> > > look like a justification for keeping all that unused code around.
> > 
> > The purpose of LIM is to provide an integrity infrastructure to support 
> > different types of integrity data.  IMA implements both the LIM
> > API for it's own internal use, and exports it for others to call.
> > 
> > As Dave Safford pointed out in http://lkml.org/lkml/2008/11/17/362,
> > there are other projects that want to add differently structured
> > measurements to the TPM measurement list.  The template abstraction is
> > critical to allowing these differently formatted messages to be added to
> > the list.
> 
> I think we're talking past each other.
> 
> In integrity.h there are two operation vectors defines:
> 
>  - struct integrity_operations delcares the operations called from the
>    VFS.  This one is actually used.  While I don't agree to Dave's
>    argument, because we don't put bloat in just because people might
>    eventually some day use it when they are in the right mood and the
>    sun shines, thisn't isn't the one I'm talking about in this thread.
>  - struct template_operations on the others is not only really badly
>    named for appearing in a global header but also not used in a
>    meaningfull way.  There is one single instace of it,
>    ima_template_ops, and while there are five helpers added in the
>    second patch that use it (integrity_collect_measurement,
>    integrity_appraise_measurement, integrity_store_measurement,
>    integrity_store_template, integrity_must_measure) none of them
>    is used at all during the patch series.  There are two direct
>    uses of these template added in the third path, to implement the
>    show operations for the "binary_runtime_measurements" and
>    "ascii_runtime_measurements" files ins securityfs, but given that
>    those are inside ima there no reason for the indirection at all.

Yeah I can definately see that.

Mimi, you used to have another template (I thought) which just tracked
security_ops to try and prevent subversion of the LSM hooks.  Or something like
that.  That was a separate template_ops, right?  Can you post that again?  That
might answer both Christoph's query about the usefulness of the indirection,
and Dave's question about "how could I use this, anyway".

If you do repost it, please be very clear about what it is expected
to do/protect against, and how, using no acronyms which you don't
define on first use :)

thanks,
-serge
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