Re: [ GLSA 200512-04 ] Openswan, IPsec-Tools: Vulnerabilities in ISAK MP Protocol implementation

On Tue, Dec 13, 2005 at 09:49:40PM +0100, Paul Wouters wrote:
> On Mon, 12 Dec 2005, Thierry Carrez wrote:
>
> >- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> >Gentoo Linux Security Advisory GLSA 200512-04
> >- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> > http://security.gentoo.org/
> >- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> >
> > Severity: Normal
> > Title: Openswan, IPsec-Tools: Vulnerabilities in ISAKMP Protocol
> > implementation
> > Date: December 12, 2005
> > Bugs: #112568, #113201
> > ID: 200512-04
>
> >Openswan and IPsec-Tools suffer from an implementation flaw which may
> >allow a Denial of Service attack.
>
> That is correct (for openswan)

It is also correct for ipsec-tools, but require a very weak
configuration.

> >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 !

Yvan, ipsec-tools team.

-- 
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