FreeBSD Security Advisory: FreeBSD-SA-98:08.fragment
FreeBSD Security Officer
security-officer at FreeBSD.ORG
Wed Nov 4 11:37:49 PST 1998
-----BEGIN PGP SIGNED MESSAGE-----
=============================================================================
FreeBSD-SA-98:08 Security Advisory
FreeBSD, Inc.
Topic: IP fragmentation denial of service
Category: core
Module: kernel
Announced: 1998-11-04
Affects: FreeBSD 3.0 and
FreeBSD-current before the correction date.
Corrected: FreeBSD-3.0 and FreeBSD-current as of 1998/10/27
FreeBSD only: Yes
Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:08/
I. Background
IP connections are controlled through a series of packets that are
received by the two computers involved in the connection.
When packets are too large to be sent in a single IP packet (due to
interface hardware limitations for example), they can be fragmented
(unless prohibited by the Don't Fragment flag).
The final destination will reassemble all the fragments of an IP packet
and pass it to higher protocol layers (like TCP or UDP).
II. Problem Description
There is a bug in the IP fragment reassembly code that might lead
to a kernel panic. An attacker can create and send a pair of
malformed IP packets which are then reassembled into an invalid
UDP datagram. Such an UDP datagram would then cause a server to
panic and crash.
III. Impact
When this bug is exploited the operating system will panic. This results
in a reboot of the system.
This vulnerability has been discussed in public security forums and
exploit programs are circulating to take advantage of this bug.
IV. Workaround
None.
V. Solution
Index: ip_input.c
===================================================================
RCS file: /home/cvsup/freebsd/CVS/src/sys/netinet/ip_input.c,v
retrieving revision 1.102
retrieving revision 1.103
diff -u -u -r1.102 -r1.103
--- ip_input.c 1998/10/16 03:55:01 1.102
+++ ip_input.c 1998/10/27 09:11:41 1.103
@@ -750,7 +750,7 @@
* if they are completely covered, dequeue them.
*/
for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
- p = q, q = nq) {
+ q = nq) {
i = (ip->ip_off + ip->ip_len) -
GETIP(q)->ip_off;
if (i < GETIP(q)->ip_len) {
=============================================================================
FreeBSD, Inc.
Web Site: http://www.freebsd.org/
Confidential contacts: security-officer at freebsd.org
Security notifications: security-notifications at freebsd.org
Security public discussion: freebsd-security at freebsd.org
PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc
Notice: Any patches in this document may not apply cleanly due to
modifications caused by digital signature or mailer software.
Please reference the URL listed at the top of this document
for original copies of all patches if necessary.
=============================================================================
-----BEGIN PGP SIGNATURE-----
Version: 2.6.3ia
Charset: noconv
iQCVAwUBNkCrf1UuHi5z0oilAQE0GgQAga3x91fd4QU8/vXKkPp8h2hUmHifhdIc
K4PynSKtqP8IQFzMzGApMU5MLCV2s6cXLj2cznAuCcHiF6xWsTIf1JoqgtaYZaTS
pBtW9Dxp+5OYlVnGHfijUbO8sop2PpAqaBpVv2CnxYvFz3sMbM8z1H7wkWEHvL7Z
MHXYAJ2Apfk=
=fOyn
-----END PGP SIGNATURE-----
This is the moderated mailing list freebsd-announce.
The list contains announcements of new FreeBSD capabilities,
important events and project milestones.
See also the FreeBSD Web pages at http://www.freebsd.org
To Unsubscribe: send mail to majordomo at FreeBSD.org
with "unsubscribe freebsd-announce" in the body of the message
More information about the freebsd-announce
mailing list