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BIND Nuking
From: MoNoLiTH+ () CMU EDU (Aveek Datta)
Date: Fri, 25 Jul 1997 00:49:45 -0400

This was sent to me by my nameserver administrator. Credit goes
to him, listed below.
This little script "bind_nuke" :


echo 'bind_nuke (c) Artur Skawina skawina () usa net'

nsupdate <<END
update delete x.$1 A
update add x.$1 60 IN A
update delete x.$1 A


when executed as "bind_nuke bogus.org" on a host, that bogus.org's
primary NS is configured to accept updates from, will cause named
to silently die. Nothing in the logs, nothing on the console.
After a number of similar packets has been received by named any
subsequent attempt to run it will only result in a Segmentation Fault.
[and there's "spoofing"...]

The problem seems to be that bind can not handle updating the
same RR more than once in the same DNS packet.
And as it saves the update requests in the <zone>.log file
and attempts to perform the updates again when restarted,
the bug is triggered again...

The bug is present in both bind8.1 and bind8.1.1.
With bind8.1 one such DU packet was enough to prevent named from runing,
until the /var/named/pri/<zone>.log file was removed/edited.
Bind 8.1.1 needs a few packets (but usually <=3) before this happens
(named still dies after only one packet, but it is sometimes possible to
restart it w/o any immediate errors/warnings).

  Network Administrator, Monolith Internet Services [TM]  _ _ _   _  Aveek
  SysAdmin, Carnegie Mellon Univ ITC   _ __  ___ _ _  ___| (_) |_| |_Datta
  Personal Website @ datta.ml.org    _| '  \/ _ \ ' \/ _ \ | |  _| ' \ _
  All opinions are ONLY mine.       (_)_|_|_\___/_||_\___/_|_|\__|_||_(_)
  [Get a free domain for your website or machine at http://www.ml.org]

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