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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


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

On Mon, 12 Dec 2005, Thierry Carrez wrote:


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.


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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