Re: Remote crash in tcpdump from OpenBSD

[Otto Moerbeek <otto () drijf net>]

On Fri, 6 Aug 2004, Balaram Amgoth wrote:

> In-Reply-To: <20031221174837.14808.qmail () sf-www3-symnsj securityfocus com>
>
> Hi Mike,
> 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.

        -Otto

> Thanks for your time in advance
>
> Balaram
>
>
>
> > Received: (qmail 9162 invoked from network); 22 Dec 2003 22:59:01 -0000
> > Received: from outgoing2.securityfocus.com (205.206.231.26)
> >  by mail.securityfocus.com with SMTP; 22 Dec 2003 22:59:01 -0000
> > Received: from lists2.securityfocus.com (lists2.securityfocus.com [205.206.231.20])
> >         by outgoing2.securityfocus.com (Postfix) with QMQP
> >         id 910C48F350; Mon, 22 Dec 2003 10:01:02 -0700 (MST)
> > Mailing-List: contact bugtraq-help () securityfocus com; run by ezmlm
> > Precedence: bulk
> > List-Id: <bugtraq.list-id.securityfocus.com>
> > List-Post: <mailto:bugtraq () securityfocus com>
> > List-Help: <mailto:bugtraq-help () securityfocus com>
> > List-Unsubscribe: <mailto:bugtraq-unsubscribe () securityfocus com>
> > List-Subscribe: <mailto:bugtraq-subscribe () securityfocus com>
> > Delivered-To: mailing list bugtraq () securityfocus com
> > Delivered-To: moderator for bugtraq () securityfocus com
> > Received: (qmail 20728 invoked from network); 21 Dec 2003 17:42:27 -0000
> > Date: 21 Dec 2003 17:48:37 -0000
> > Message-ID: <20031221174837.14808.qmail () sf-www3-symnsj securityfocus com>
> > Content-Type: text/plain
> > Content-Disposition: inline
> > Content-Transfer-Encoding: binary
> > MIME-Version: 1.0
> > X-Mailer: MIME-tools 5.411 (Entity 5.404)
> > 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 
> > bad data.
> > 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
> > Lines: ~566-616
> >
> > 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
> > tcpdump: 3.4.0
> > libpcap" 0.5
> >
> > Thanks,
> > Mike