On Aug 24, 2009, at 1:41 PM, J. Bruce Fields wrote:
On Mon, Aug 24, 2009 at 01:06:58PM -0400, Trond Myklebust wrote:
On Mon, 2009-08-24 at 12:10 -0400, J. Bruce Fields wrote:
On Fri, Aug 21, 2009 at 05:51:02PM -0400, Trond Myklebust wrote:
On Fri, 2009-08-21 at 17:47 -0400, J. Bruce Fields wrote:
On Fri, Aug 21, 2009 at 05:40:36PM -0400, Trond Myklebust wrote:
On Fri, 2009-08-21 at 17:30 -0400, J. Bruce Fields wrote:
3c1bb23c037, first in 1.1.3, removes AUTH_NULL from that static
list.
Does the server support auth_null security? I didn't think it
did.
Just off the top of my head, without looking at the code: I
believe it
treats auth_null rpc calls exactly as if they were auth_sys
calls with
uid and gid set to the "anonymous" uid and gid.
OK, so that would break too.
I've lost track of the antecedent to "that".
Negotiating AUTH_NULL security for those mountd programs that fake
up a
list of flavours that excludes AUTH_NULL.
OK, got it.
(And note (a reminder to anyone that forgot) the omission of AUTH_NULL
is a workaround for a bug in older mount.nfs which caused the client
to
prefer flavors at the end of the list. (Fixed in 3c1bb23c03, which
went
into 1.1.3. When was that bug introduced?) That means some clients
read the list forwards, and some backwards, so if you want clients to
avoid picking AUTH_NULL by default, there's no safe place to put it.
Since AUTH_NULL seems rarely needed, it seemed best just to leave it
off.)
RFC 2623 suggests how the server should sort the returned flavor
list. However I don't think there's a consistent algorithm the client
can use with that list to determine a good default for that mount.
So, I would argue that any client that uses the "first" or "last"
entry in that list as the mount's auth flavor is probably broken; it
should pick a sec= default for all mounts, and if it's not on the
returned list, fail the mount. That is, incidentally, what the kernel
MNT client does now.
Anyway, we could add a second special case on the client side that
allowed an explicit sec=null to bypass checking against the server
list.
I don't know who actually needs mounts with sec=null.
Or, we can make sure the server provides AUTH_NULL in the list _only_
if that flavor is specified explicitly on the export line. Otherwise,
a single entry flavor list (ie supporting only AUTH_UNIX) is probably
the best default we can provide for the reasons you state above.
It would help to provide some documenting comments to that effect in
the code, or maybe even state it in the exports(5) man page.
And/or we could plan to put AUTH_NULL back on the server's list some
day, depending on how widely disseminated we think the backwards mount
behavior was....
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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