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Re: [ GLSA 200512-04 ] Openswan, IPsec-Tools: Vulnerabilities in ISAKMP Protocol implementation
From: Thierry Carrez <koon () gentoo org>
Date: Wed, 14 Dec 2005 13:12:16 +0100

VANHULLEBUS Yvan wrote:

On Tue, Dec 13, 2005 at 09:49:40PM +0100, Paul Wouters wrote:

On Mon, 12 Dec 2005, Thierry Carrez wrote:

[...]
Impact
======

A remote attacker can create a specially crafted packet using 3DES with
an invalid key length, resulting in a Denial of Service attack, format
string vulnerabilities or buffer overflows.

That's a copy and paste from the IPsec proto testsuite.

1) It conflicts with the above comment that this is only a DOS
2) It's incorrect (for openswan)

Also incorrect for ipsec-tools AFAIK. The only problem we noticed with
protos testsuite was a lack of verification for some payloads
existency in aggressive mode.

Workaround
==========

Avoid using "aggressive mode" in ISAKMP Phase 1, which exchanges
information between the sides before there is a secure channel.

In fact, you would to both have aggressive mode enabled AND know the PSK.
If you have those two enabled, you are vulnerable to a MITM anyway, since
any client knowing the PSK can pretend to be the IPsec security gateway.


Knowing the PSK is not really needed, as AGGRESSIVE+PSK mode is known
to be quite unsecure, and can be bruteforced offline.

The "workaround" for ipsec-tools is to upgrade, and is only needed for
some people which really have a week configuration and should care
about lots of potential problems !

Paul, Yvan,

Many thanks for the precisions and sorry for getting it wrong. I'll fix
the GLSA text for Impact and Workaround on the Gentoo website asap.

-- 
Thierry Carrez (Koon)
Gentoo Linux Security

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