Date: 2 Sep 2004 14:05:57 +0200
From: SecuriTeam <support@securiteam.com.>
To: [email protected]Subject: [UNIX] OpenBSD Kernel Panic While Processing IPSec Link2 Option
The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
- - promotion
The SecuriTeam alerts list - Free, Accurate, Independent.
Get your security news from a reliable source.
http://www.securiteam.com/mailinglist.html
- - - - - - - - -
OpenBSD Kernel Panic While Processing IPSec Link2 Option
------------------------------------------------------------------------
SUMMARY
A bug in the way the OpenBSD kernel handles ICMP packets while the link2
option is set for IPSec processing leaves the system vulnerable to a
single ICMP packet attack able to crash the kernel.
DETAILS
Vulnerable Systems:
* OpenBSD version 3.5
An OpenBSD system configured as a gateway between two networks might be
vulnerable to a specific attack that can crash the kernel if bridging is
enabled and the link2 option is given for IPSec processing. In an event
that a malformed ICMP echo request packet arrives from a host on network A
with a destination of a host on network B, the OpenBSD kernel will crash
and cause a kernel panic.
No core file is generated. If the DDB_PANIC option is set, the machine
reboots upon receipt of the ICMP echo request. The commands that lead to
the vulnerable situations are as follows:
# ifconfig bridge0 create
# brconfig bridge0 add fxp0 add fxp1 up
# brconfig bridge0 link2
Naturally, in order to configure the system in such a manner, a user would
have to have root access on the system.
The problem was observed on a test network and was reproduced as well on a
VMWare network.
Patch Availability:
The OpenBSD team was contacted and a patch was introduced to the CVS
within 12 hours, an errata is available at:
<http://www.openbsd.org/errata34.html>;
http://www.openbsd.org/errata34.html. The patch code is listed below and
is also available from
<ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.4/common/028_bridge.patch>;
ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.4/common/028_bridge.patch:
Index: sys/net/if_bridge.c
RCS file: /cvs/src/sys/net/if_bridge.c,v
retrieving revision 1.136
diff -u -r1.136 if_bridge.c
--- sys/net/if_bridge.c 21 Jun 2004 23:50:36 -0000 1.136+ sys/net/if_bridge.c 18 Aug 2004 09:29:04 -0000
@@ -2275,9 +2275,9 @@
splx(s);
return (1);
} else {
+ splx(s);
skiplookup:
/* XXX do an input policy lookup */
- splx(s);
return (0);
}
} else { /* Outgoing from the bridge. */
ADDITIONAL INFORMATION
The information has been provided by <mailto:vafa@hush.ai.> Vafa Izadinia.
This bulletin is sent to members of the SecuriTeam mailing list.
To unsubscribe from the list, send mail with an empty subject line and body to: [email protected]
In order to subscribe to the mailing list, simply forward this email to: [email protected]
DISCLAIMER:
The information in this bulletin is provided "AS IS" without warranty of any kind.
In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.
