Date: Fri, 29 Feb 2008 09:52:15 -0800 (PST)
From: Casey Schaufler <casey@schaufler-ca.com>
Reply-To: casey@schaufler-ca.com
Subject: Re: [PATCH 01/11] Security: Add hook to get full maclabel xattr name
To: Stephen Smalley <sds@tycho.nsa.gov>, Christoph Hellwig <hch@infradead.org>
Cc: casey@schaufler-ca.com, Dave Quigley <dpquigl@tycho.nsa.gov>,
       viro@ftp.linux.org.uk, trond.myklebust@fys.uio.no, bfields@fieldses.org,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       LSM List <linux-security-module@vger.kernel.org>
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--- Stephen Smalley <sds@tycho.nsa.gov> wrote:

> 
> On Thu, 2008-02-28 at 18:48 -0500, Christoph Hellwig wrote:
> > On Thu, Feb 28, 2008 at 02:30:35PM -0500, Stephen Smalley wrote:
> > > This is an interface to be used by NFS to get information from the
> > > security module.  The information desired is specific to the MAC
> > > labeling functionality in NFSv4 that is being proposed.  That
> > > functionality is MAC specific (necessarily so, just like the ACL
> > > functionality is ACL specific).  We are hiding the SELinux-specific bits
> > > behind the LSM interface, and non-MAC LSMs are free to return NULL in
> > > order to indicate that they don't support MAC labeling.  We do NOT want
> > > the capability module to return its security blob here, or any other
> > > non-MAC LSM - it will yield the wrong semantics for the NFS MAC support.
> > 
> > I think Casey is totally right here.  The LSM interface should not be
> > as specific here.  If you want to limit the NFSv4 interface to single
> > MAC xattr label based systems add an additional method to check if
> > the LSM is that.  But the proper fix is of course to not add somthing
> > so specific to NFSv4 at all, as it's got enough shortcoming already.
> > Please add a proper xattr protocol.  It's not like it's hard, SGI
> > has been doing this in IRIX for NFSv3 for ages as a sideband protocol,
> > and even release the reference source under the GPL.  Just either use
> > that with NFSv4 or if you feel fancy merge it into the NFS spec for
> > NFSv6^H4.2.
> > 
> > > In any event, I don't think we need your permission.
> > 
> > Wow, that's rude even to someone as direct as me.  Casey is the only
> > other person having an in-tree LSM, and I think his input in this
> > area is important.  But if not I as a VFS person can happily give
> > you my "no" for the current version from the VFS point of view.
> 
> Fair point - my apologies to Casey.

Accepted. Now we work together like horses in troika.


Casey Schaufler
casey@schaufler-ca.com
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