Mike,
So what I think you may be getting at is one of two things:
1. Most BIND exploits are TCP-based, and most sharp firewalls
admins allow only UDP. In this case, no dice.
Three or four years ago there was a UDP based exploit for
BIND, some vuln in recursion I think...anyway go Google. :)
2. Some of the BIND exploits were attacked via overflow in
the protocol headers, so if you are facing a firewall that
does some protocol validation, and DNS is a common/easy one
to do, then you exploit may be blocked over TCP by a protocol
validator that sees a non-RFC compliant/sized header.
3. There's lots of third options that may or may not be
viable. Look for a proxy with CONNECT method enabled to
the outside world, and shove a TCP connection to the BIND
server through their proxy, or Citrix box, or anything
else you can find open.
-ae
-----Original Message-----
From: Julian Totzek [mailto:julian.totzek@bristol.de]
Sent: Monday, February 13, 2006 2:32 PM
To: Mike Gilligan; pen-test@securityfocus.com
Subject: AW: pushing exploits through the Firewall
Hi group
Say a pentester manages to discover a vulnerable version of BIND
running
on
an external DNS server and has successfully sourced an
exploit for the
vuln.
I'm curious how it would be possible to launch the exploit
against the
server when a packet filtering device and stateful
inspection Firewall
sit
between the pentester and the vuln host. It would seem at
first glance
that
this is not a viable option. How else might one go about exploiting
the
vuln?
Hi Mike,
remember, a firewall is mostly controlling the entrance but not the
application itself. So if there is a exploit running on port
UDP 53 the
firewall will let it pass, cause it only knows port 53 UDP is
legitimate
traffic.
Sometimes there are some kind of filter enabled in firewalls
which will
block these exploits, but normally there is nothing ;-)
So just go for it and try it :-)
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