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FreeBSD Security Advisories

2007-Apr-26 23:49 UTC

FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

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============================================================================FreeBSD-SA-07:03.ipv6
Security Advisory
                                                          The FreeBSD Project

Topic:          IPv6 Routing Header 0 is dangerous

Category:       core
Module:         ipv6
Announced:      2007-04-26
Credits:        Philippe Biondi, Arnaud Ebalard, Jun-ichiro itojun Hagino
Affects:        All FreeBSD releases.
Corrected:      2007-04-24 11:42:42 UTC (RELENG_6, 6.2-STABLE)
                2007-04-26 23:42:23 UTC (RELENG_6_2, 6.2-RELEASE-p4)
                2007-04-26 23:41:59 UTC (RELENG_6_1, 6.1-RELEASE-p16)
                2007-04-24 11:44:23 UTC (RELENG_5, 5.5-STABLE)
                2007-04-26 23:41:27 UTC (RELENG_5_5, 5.5-RELEASE-p12)
CVE Name:       CVE-2007-2242

I.   Background

IPv6 provides a routing header option which allows a packet sender to
indicate how the packet should be routed, overriding the routing knowledge
present in a network.  This functionality is roughly equivalent to the
"source routing" option in IPv4.  All nodes in an IPv6 network -- both
routers and hosts -- are required by RFC 2640 to process such headers.

II.  Problem Description

There is no mechanism for preventing IPv6 routing headers from being used
to route packets over the same link(s) many times.

III. Impact

An attacker can "amplify" a denial of service attack against a link
between
two vulnerable hosts; that is, by sending a small volume of traffic the
attacker can consume a much larger amount of bandwidth between the two
vulnerable hosts.

An attacker can use vulnerable hosts to "concentrate" a denial of
service
attack against a victim host or network; that is, a set of packets sent
over a period of 30 seconds or more could be constructed such that they
all arrive at the victim within a period of 1 second or less.

Other attacks may also be possible.

IV.  Workaround

No workaround is available.

V.   Solution

NOTE WELL: The solution described below causes IPv6 type 0 routing headers
to be ignored.  Support for IPv6 type 0 routing headers can be re-enabled
if required by setting the newly added net.inet6.ip6.rthdr0_allowed sysctl
to a non-zero value.

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE, or 6-STABLE, or to the
RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the
correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 5.5, 6.1,
and 6.2 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch http://security.FreeBSD.org/patches/SA-07:03/ipv6.patch
# fetch http://security.FreeBSD.org/patches/SA-07:03/ipv6.patch.asc

b) Apply the patch.

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:http://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_5
  src/sys/netinet6/in6.h                                         1.35.2.5
  src/sys/netinet6/in6_proto.c                                   1.29.2.5
  src/sys/netinet6/route6.c                                      1.10.4.2
RELENG_5_5
  src/UPDATING                                            1.342.2.35.2.12
  src/sys/conf/newvers.sh                                  1.62.2.21.2.14
  src/sys/netinet6/in6.h                                     1.35.2.3.2.1
  src/sys/netinet6/in6_proto.c                               1.29.2.4.2.1
  src/sys/netinet6/route6.c                                  1.10.4.1.4.1
RELENG_6
  src/sys/netinet6/in6.h                                         1.36.2.8
  src/sys/netinet6/in6_proto.c                                   1.32.2.6
  src/sys/netinet6/route6.c                                      1.11.2.2
RELENG_6_2
  src/UPDATING                                             1.416.2.29.2.7
  src/sys/conf/newvers.sh                                   1.69.2.13.2.7
  src/sys/netinet6/in6.h                                     1.36.2.7.2.1
  src/sys/netinet6/in6_proto.c                               1.32.2.5.2.1
  src/sys/netinet6/route6.c                                  1.11.2.1.4.1
RELENG_6_1
  src/UPDATING                                            1.416.2.22.2.18
  src/sys/conf/newvers.sh                                  1.69.2.11.2.18
  src/sys/netinet6/in6.h                                     1.36.2.6.2.1
  src/sys/netinet6/in6_proto.c                               1.32.2.4.2.1
  src/sys/netinet6/route6.c                                  1.11.2.1.2.1
- -------------------------------------------------------------------------

VII. References

http://www.secdev.org/conf/IPv6_RH_security-csw07.pdf

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2242

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-07:03.ipv6.asc
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Koga Youichirou

2007-Apr-27 05:55 UTC

head link

FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

>
============================================================================>
FreeBSD-SA-07:03.ipv6                                       Security Advisory
>                                                           The FreeBSD
Project
> 
> Topic:          IPv6 Routing Header 0 is dangerous
- snip -> I.   Background
> 
> IPv6 provides a routing header option which allows a packet sender to
> indicate how the packet should be routed, overriding the routing knowledge
> present in a network.  This functionality is roughly equivalent to the
> "source routing" option in IPv4.  All nodes in an IPv6 network --
both
> routers and hosts -- are required by RFC 2640 to process such headers.
s/RFC 2640/RFC 2460/

Regards,

-- Koga, Youichirou

Colin Percival

2007-Apr-28 01:12 UTC

head link

FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

Koga Youichirou wrote:>>
============================================================================>>
FreeBSD-SA-07:03.ipv6                                       Security Advisory
>>                                                           The FreeBSD
Project
>> IPv6 provides a routing header option which allows a packet sender to
>> indicate how the packet should be routed, overriding the routing
knowledge
>> present in a network.  This functionality is roughly equivalent to the
>> "source routing" option in IPv4.  All nodes in an IPv6
network -- both
>> routers and hosts -- are required by RFC 2640 to process such headers.
> 
> s/RFC 2640/RFC 2460/
Oops...

Colin Percival

Peter Thoenen

2007-Apr-28 22:02 UTC

head link

FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

Umm maybe its just but I fail to see why this is a security advisory 
(initially caught this on the OBSD list).  You are following the RFC .. 
if you don't like "evil" packets, then drop them at the firewall
or
router layer ... don't see the need for an OS fix.

Robert Joosten

2007-Apr-29 18:14 UTC

head link

FreeBSD Security Advisory FreeBSD-SA-07:03.ipv6

Hi,
> Affects:        All FreeBSD releases.
> Corrected:      2007-04-24 11:42:42 UTC (RELENG_6, 6.2-STABLE)
>                 2007-04-26 23:42:23 UTC (RELENG_6_2, 6.2-RELEASE-p4)
>                 2007-04-26 23:41:59 UTC (RELENG_6_1, 6.1-RELEASE-p16)
>                 2007-04-24 11:44:23 UTC (RELENG_5, 5.5-STABLE)
>                 2007-04-26 23:41:27 UTC (RELENG_5_5, 5.5-RELEASE-p12)
> CVE Name:       CVE-2007-2242
For those running releng_4_11, I observed this message:
http://leaf.dragonflybsd.org/mailarchive/commits/2007-04/msg00178.html 
from our neighbors at dragonfly. 

It seems to apply cleanly (I did the patch by hand) and the kernel at 
leasts compiles. Unable to verify it runs ok or solves this issue 
due to time constraints atm :-/

Hth.
Robert

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