BugTraq
Re: Samba Remote Zero-Day Exploit Feb 06 2010 01:21PM
Stefan Kanthak (stefan kanthak nexgo de) (2 replies)
RE: Samba Remote Zero-Day Exploit Feb 08 2010 08:38PM
Michael Wojcik (Michael Wojcik microfocus com) (1 replies)
Re: Samba Remote Zero-Day Exploit Feb 08 2010 09:33PM
Stefan Kanthak (stefan kanthak nexgo de) (1 replies)
RE: Samba Remote Zero-Day Exploit Feb 09 2010 02:20PM
Michael Wojcik (Michael Wojcik microfocus com)
> From: Stefan Kanthak [mailto:stefan.kanthak (at) nexgo (dot) de [email concealed]]
> Sent: Monday, 08 February, 2010 16:33
>
> Michael Wojcik wrote:
>
> >> From: Stefan Kanthak [mailto:stefan.kanthak (at) nexgo (dot) de [email concealed]]
> >> Sent: Saturday, 06 February, 2010 08:21
> >>
> >> Since Windows 2000 NTFS supports "junctions", which pretty much
> >> resemble Unix symlinks, but only for directories.
> >> See <http://support.microsoft.com/kb/205524/en-us>
> >
> > And at least since Vista, it also supports symlinks, which are
> > designed
>
> s/at least//
> [ well-known facts snipped ]

So ... your original note about junctions did not cover "well-known
facts", but my note about other reparse point types did?

> > The Windows SMB server apparently won't cross reparse points,
though,
> > so there's no equivalent vulnerability.
>
> NO, Windows SMB server crosses reparse points!

Not in my testing, at least not for junctions and symlinks. User with
requisite authority could traverse the junctions and symlinks locally,
but not remotely via a share.

> But as Dan Kaminsky pointed out, you need to have administrative
rights
> to remotely create a junction on an SMB share, so the non-admin user
> cant get himself access to files outside a share he's allowed to
> access.

Unless the reparse point already exists.

This particular exploit happened to involve a remote user creating a
symlink. That doesn't mean there are no other imaginable vulnerabilities
stemming from filesystem objects that violate the notional tree
structure of the directory hierarchy.

The obvious one: someone shares a branch of the directory tree in the
belief that clients only have access to that part of the tree, but the
tree already contains a convenience symlink (Unix) or reparse point
(Windows) that points elsewhere in the hierarchy. That's one reason why
Samba has had the "wide links=no" option since, what, the mid-1990s.

--
Michael Wojcik
Principal Software Systems Developer, Micro Focus

[ reply ]
Re: Samba Remote Zero-Day Exploit Feb 06 2010 05:43PM
Dan Kaminsky (dan doxpara com) (1 replies)
Re: Samba Remote Zero-Day Exploit Feb 06 2010 10:26PM
Stefan Kanthak (stefan kanthak nexgo de)


 

Privacy Statement
Copyright 2010, SecurityFocus