mailing list archives
Re: Remote crash in tcpdump from OpenBSD
From: Otto Moerbeek <otto () drijf net>
Date: Sat, 7 Aug 2004 20:45:30 +0200 (CEST)
On Fri, 6 Aug 2004, Balaram Amgoth wrote:
In-Reply-To: <20031221174837.14808.qmail () sf-www3-symnsj securityfocus com>
Will the following packet be enough to reproduce this problem.
char packet = "\x82\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
FYI, this is a report from December 2003. This has been fixed in OpenBSD
3.4-stable and (then -current, now) 3.5. Feel free to expore this further,
but I don't think this is very interesting material for this list, more
than 7 months after the original report.
Thanks for your time in advance
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Date: 21 Dec 2003 17:48:37 -0000
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From: <mrh_tech () yahoo com>
To: bugtraq () securityfocus com
Subject: Re: Remote crash in tcpdump from OpenBSD
In-Reply-To: <3FE4CAC1.8010306 () freebsd lublin pl>
When an l2tp control packet is sent with optional bits set but containing invalid data, l2tp_avp_print() is passed this
Then, l2tp_avp_print() calls itself and continues an infinite loop of passing bad data to itself.
I had the consistent results sending:
\x82 (control+length bits)
\0x02 (version) then 10 bytes of zeros.
This is in print-l2tp.c
After commenting out (breaking the infinite loop):
~609: l2tp_avp_print(dat + len, length - len);
I was no longer able to crash tcpdump.
Obviously, properly validating the input is the real solution.
Tested on: OpenBSD 3.3 and 3.4