Add S_IFTRIGGER to st_mode [PSARC/2007/563 FastTrack timeout 10/04/2007]

[James Carlson]

Nicolas Williams writes:
> On Fri, Oct 05, 2007 at 03:37:01PM -0400, James Carlson wrote:
> > Don Cragun writes:
> > > I'm still strongly opposed.  If the path presented to the first
> > > *stat*() function is a symlink pointing to an autofs/nfs directory, the
> > > symlink can be changed between the *stat*() call and the opendir() call
> > > and this spoofing action cannot be reliably detected by the
> > > application.  With AT_TRIGGER, this spoofing action can be caught every
> > > time it happens.
> > 
> > Yes.  However, that's actually the same state we are in right now
> > (with no fix at all), and the state we've been in since February 2005
> > when CR 6198351 integrated and added the autofs-testing logic.  It's a
> > hole that ought to be fixed, but it's a little less clear to me that
> > it's this project team's responsibility to do so.
> 
> This hole is not much of a hole for the autofs case because users don't
> normally get to make symlinks in autofs directories.  That consideration
> does not apply here, so technically the change made for autofs did not
> introduce a security bug, but this change would.

How's that?

The proposed change looks equivalent to me in terms of security.  Have
you looked at the webrev?  Previously, we compared st_fstype from the
first stat() against "autofs" to check for trigger points, and now
(with the proposed change, and in exactly the same code) we look at
st_mode from the first stat() and check for the S_TRIGGER flag.  The
two versions do exactly the same thing functionally, so I don't see
how this change introduces any flaw that isn't there today and hasn't
been there for more than 2.5 years.

I also agree that users can't normally write to those directories, so
it's likely moot -- both before and after this project.

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
Sun Microsystems / 35 Network Drive        71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677