Claimed Zero Day exploit in Samba.
michael.s.gilbert at gmail.com
Fri Feb 5 14:37:01 MST 2010
On Fri, 05 Feb 2010 16:18:59 -0500, simo wrote:
> On Fri, 2010-02-05 at 16:10 -0500, Michael Gilbert wrote:
> > On Fri, 5 Feb 2010 12:46:06 -0800, Jeremy Allison wrote:
> > > On Fri, Feb 05, 2010 at 03:48:37PM -0500, Michael Gilbert wrote:
> > > >
> > > > in your original description, you stated that "wide links = no" will
> > > > generate an "access denied" error when a "wide link" is accessed;
> > > > however, you didn't mention that creation of "wide links" is also
> > > > prevented. if this is true, then that is a very satisfactory
> > > > solution.
> > >
> > > No, it's actually incorrect. If "wide links = no", then no
> > > one can ever access anything off share, and so UNIX symlinks
> > > should be allowed to point to anywhere they like, as UNIX
> > > clients will follow them locally, not on the server.
> > >
> > > > however, i think that the prevention code itself already
> > > > solves the root of the issue, and enabling that by default would fully
> > > > solve the problem.
> > >
> > > Nope - see above :-).
> > >
> > > > i can understand giving the local administrator this capability.
> > > > however, i don't see the need for remote users to have such authority
> > > > (although any enlightenment would be very much appreciated).
> > >
> > > Imagine an app running on a Linux client that needs a symlink
> > > to /usr/local/lib inside it's filespace (don't know why, but
> > > it might :-). If that app is run off a CIFSFS share creating
> > > the /usr/local/lib symlink would fail with "wide links = no",
> > > which is not what you want.
> > that's a very good example. would it be wrong to dictate that local
> > paths must be hardcoded, rather than symlinked
> hardcoded to what ?
i.e. the app would have to always make use of /usr/local/lib, rather
> > (or manually symlinked by the samba server administrator)?
> what would be advantage except making the life of a user harder when an
> application that needs to create a symlink breaks ?
> Remember that creating a symlink is not a problem, with wide links = no
> it is not followed in any case.
the problem is that some users will need to set "wide links = yes", and
will be forced to leave themselves vulnerable to this issue.
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