linux-kernel - Re: [RFC][Patch 2/6] integrity: fs hook placement

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Message-ID: <20070308210700.GB2750@sergelap.austin.ibm.com>
Date:	Thu, 8 Mar 2007 15:07:00 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, safford@...son.ibm.com,
	serue@...ux.vnet.ibm.com, kjhall@...ux.vnet.ibm.com,
	zohar@...ibm.com
Subject: Re: [RFC][Patch 2/6] integrity: fs hook placement

Quoting Stephen Smalley (sds@...ho.nsa.gov):
> On Thu, 2007-03-08 at 12:01 -0600, Serge E. Hallyn wrote:
> > Quoting Chris Wright (chrisw@...s-sol.org):
> > > * Serge E. Hallyn (serue@...ibm.com) wrote:
> > > > Are you objecting only to the duplication at the callsites, so that an
> > > > fsnotify-type of consolidation of security and integrity hooks would be
> > > > ok?  Or are you complaining that the security_inode_setxattr and
> > > > integrity_inode_setxattr hooks are too similar anyway, and integrity
> > > > modules should just use some lsm hooks for anything which will be
> > > > authoritative?
> > > 
> > > It's duplication of callsites with many identical implementations
> > > that's the problem.
> > 
> > Yes it's ugly...
> > 
> > But I guess it gets a point across :)
> > 
> > > > (I could see an argument that integirty subsystem should be purely for
> > > > measuring and hence its hooks should never return a value.  Only hitch
> > > > there is that if integrity subsystem hits ENOMEM it should be able to
> > > > refuse the action...)
> > > 
> > > Right, that's what I was expecting to see, just the measurement
> > > infrastructure.
> > 
> > So what you are saying is EVM would stay an LSM, with a cooperating
> > integrity subsystem *just* doing measurements?
> > 
> > That's kind of what i was expecting too, however that doesn't fit as
> > well with the idea that an integrity subsystem prevents the need for lsm
> > stacking.  I think the idea was that evm would still be able to enforce
> > integrity of selinux xattrs without it stack with selinux.  So I can see
> > where this approach came from.
> 
> The enforcement mechanism should be directly integrated into SELinux,
> not stacked as a separate module.

And a big plus of splitting it up as I was describing is that anyone
who wanted could make use of the measurement module to add such
functionality to SELinux, as an alternative to the EVM LSM module.

-serge
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