Re: NFS4 ACL <-> Posix ACL

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Mar 24, 2009 at 06:22:47PM -0400, Trond Myklebust wrote:
> On Tue, 2009-03-24 at 18:15 -0400, J. Bruce Fields wrote:
> > On Tue, Mar 24, 2009 at 05:44:07PM -0400, Trond Myklebust wrote:
> > > On Tue, 2009-03-24 at 16:10 -0400, J. Bruce Fields wrote:
> > > > On Tue, Mar 24, 2009 at 02:56:25AM +0100, Alex Bremer wrote:
> > > > > >> How do other people share public files with NFS4? If there is no other
> > > > > >> way than setting the users's umask to 002, this would practically
> > > > > >> limit the use of NFS4 to private shares like home directories.
> > > > > >
> > > > > > I don't understand why--can't you use the user-private-group trick?:
> > ...
> > > > > - we actually have directories where files should only be group readable.
> > > > 
> > > > I don't get it--why not set an inheritable acl on those directories that
> > > > permits only read to the group?
> > > 
> > > That only works if the client actually respects the acl...
> > 
> > I don't understand.  ACL enforcement and inheritance are both done on
> > the server side.
> > 
> > The problem is just that the umask is applied on the client side.  But
> > if the umask is 002, and an inheritable ACL permits only read, then the
> > result of inheritance and umask-application will be an ACL that permits
> > reads (and only reads) to the group owner (and to any named users and
> > groups).
> 
> The client currently always sends a mode. My interpretation of RFC3530
> is that this will always override the inherited ACL (see the discussion
> in OP_OPEN and OP_CREATE w.r.t. the createattrs field).

Depends on what you mean by "override".  It shouldn't be replacing the
inherited ACL wholesale; see 6.4.3.

And I don't think we'd want to *entirely* stop sending the mode.

With POSIX ACLs the compromise is to ignore the umask, but continue to
respect the creat()/open() mode.

--b.