Re: [PATCH] nfsd: permit unauthenticated stat of export root

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Mon, 2008-08-11 at 17:27 -0400, Peter Staubach wrote:
> A better description of the set of operations which should be
> allowed and which ones are not should include a discussion on
> the contents of the response to the FSINFO request.  If the
> server returns attributes in the FSINFO response, then it does
> not need to allow unauthenticated GETATTR requests.  If it does
> not return attributes in the FSINFO response, then it must allow
> unauthenticated GETATTR requests because this is required in
> order to allow clients to successfully mount file systems using
> strong authentication.

Well... That's true for NFSv3, but if your server also supports
NFSv2-with-RPCSEC_GSS, then it also has to support the NFSv2 FSSTAT
+GETATTR under AUTH_SYS.

In any case, this is an issue of efficiency rather than security.
Whether you allow FSINFO w/ post-op attributes but no GETATTR, or you
allow FSINFO w/o post-op attributes and allow GETATTR on the mountpoint
is entirely equivalent from the security viewpoint: the amount of
information available using weak security is the same.

Cheers,
   Trond