Re: servers may allow owners to override permissions on readdir

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

On Wed, Jun 06, 2012 at 01:36:59PM -0400, Peter Staubach wrote:
> Sorry, I don't understand.  Why would it be desirable for the server
> to be able override directory permissions for readdir unless the
> directory is already open?

And I don't understand that question....  Note that there's no way for a
server to tell whether someone has a directory open or not.

> It is desirable to override permissions for regular files because
> executing a file requires that file's contents to be read or when
> writing to a file, requires reading the contents in order to perform
> read/modify/write cycles.

Also, to make something like

	open("file", O_CREAT|O_RDWR, 0)
	write()

work.  Or open, chmod, write.

--b.

> The protocol doesn't contain sufficient
> support to be able to distinguish the various models on a
> per-operation basis, so the server leaves it up the client to "do the
> right thing".
> 
> Perhaps a better solution would be to track open directories?  Or is
> this part of the future directory delegations work?  :-)

> 
> 	Thanx...
> 
> 		ps
> 
> 
> -----Original Message-----
> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of J. Bruce Fields
> Sent: Wednesday, June 06, 2012 12:52 PM
> To: linux-nfs@vger.kernel.org
> Cc: Jian Li
> Subject: servers may allow owners to override permissions on readdir
> 
> Anyone see any reason why I server wouldn't want to allow owners to override directory permissions on readdir?
> 
> (It turns out that the actual behavior of linux nfsd is more
> complicated: it attempts to allow overrides on readdir, but then does a lookup_one_len in the filldir method called on each entry, which results on an ACCESS error.  But readdirs of empty directories, or nfsv4 readdirs with the rdattr_error, may succeed.  I'm not quite sure what to do about that.)
> 
> --b.
> 
> commit a86c3e5f716a9b8a83dddc445a4593305c7e76d6
> Author: J. Bruce Fields <bfields@redhat.com>
> Date:   Wed Jun 6 12:38:58 2012 -0400
> 
>     4.0 server tests: server may allow owner to override permissions on readdir
>     
>     As with regular files, permissions to access a directory are checked on
>     open not on individual reads.  Therefore it is the client's
>     responsibility to do an access check, and the server should be permitted
>     to allow the owner of a directory to overrider permissions.
>     
>     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> diff --git a/nfs4.0/servertests/st_readdir.py b/nfs4.0/servertests/st_readdir.py
> index d3570dd..66efae2 100644
> --- a/nfs4.0/servertests/st_readdir.py
> +++ b/nfs4.0/servertests/st_readdir.py
> @@ -216,41 +216,6 @@ def testReservedCookies(t, env):
>          check(res, NFS4ERR_BAD_COOKIE,
>                "READDIR with reserved cookie=%i" % cookie)
>  
> -def testUnaccessibleDir(t, env):
> -    """READDIR with (cfh) in unaccessible directory 
> -
> -    FLAGS: readdir all
> -    DEPEND: MKDIR MODE
> -    CODE: RDDR11
> -    """
> -    c = env.c1
> -    path = c.homedir + [t.code]
> -    c.maketree([t.code, ['hidden']])
> -    ops = c.use_obj(path) + [c.setattr({FATTR4_MODE:0})]
> -    res = c.compound(ops)
> -    check(res, msg="Setting mode=0 on directory %s" % t.code)
> -    ops = c.use_obj(path) + [c.readdir()]
> -    res = c.compound(ops)
> -    check(res, NFS4ERR_ACCESS, "READDIR of directory with mode=0")
> -   
> -def testUnaccessibleDirAttrs(t, env):
> -    """READDIR with (cfh) in unaccessible directory requesting attrs
> -
> -    FLAGS: readdir all
> -    DEPEND: MKDIR MODE
> -    CODE: RDDR12
> -    """
> -    c = env.c1
> -    path = c.homedir + [t.code]
> -    c.maketree([t.code, ['hidden']])
> -    ops = c.use_obj(path) + [c.setattr({FATTR4_MODE:0})]
> -    res = c.compound(ops)
> -    check(res, msg="Setting mode=0 on directory %s" % t.code)
> -    ops = c.use_obj(path) + \
> -          [c.readdir(attr_request=[FATTR4_RDATTR_ERROR, FATTR4_TYPE])]
> -    res = c.compound(ops)
> -    check(res, NFS4ERR_ACCESS, "READDIR of directory with mode=0")
> -   
>  ###########################################
>  
>  
> --
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