Re: [PATCH 01/11] Security: Add hook to get full maclabel xattr name

Stephen Smalley
2008-02-29T13:31:59Z

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.

--
Stephen Smalley
National Security Agency