bugtraq - Re: [Full-disclosure] Samba Remote Zero-Day Exploit

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Message-ID: <m3pr4fs85g.fsf@intrepid.localdomain>
Date: Mon, 08 Feb 2010 22:57:15 +0100
From: Krzysztof Halasa <khc@...waw.pl>
To: Thierry Zoller <Thierry@...ler.lu>
Cc: bugtraq@...urityfocus.com, full-disclosure@...ts.grok.org.uk,
	<kcope2@...glemail.com>
Subject: Re: [Full-disclosure] Samba Remote Zero-Day Exploit

Thierry Zoller <Thierry@...ler.lu> writes:

> Facts :
> - Several distributions run with vulnerable settings per default
>   if there is a "misconfiguration" it is part of the vendor.
> - Your not supposed to be able to traverse dirs.

What's wrong with creating $HOME/tmp -> /tmp/$USER (not necessarily
with Samba, maybe with xterm or ssh) and then accessing /tmp/$USER via
/host/HOME/tmp? Why is it a problem while "ssh host cat /etc/passwd" is
not?

Can you traverse a directory for which you have no +x right?
Can you, for example, write to a file for which you have no +w right?
Read without +r?

If you can't, maybe it's a (local config?) issue with guest accounts, or
maybe Windows-only (and similar, non-guest) accounts, instead of
permissions and symlinks?

Disabling or limiting symlink creation will not really close the "hole",
the problem is not the symlink but that the user has fs access which he
(or she) should never have.

... unless (obviously) answer to any of the 3 questions is positive
(I haven't checked, to be honest) - is it?
-- 
Chris