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

[Paul Wouters <paul () xelerance com>]

On Mon, 12 Dec 2005, Thierry Carrez wrote:

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> Gentoo Linux Security Advisory                           GLSA 200512-04
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>                                            http://security.gentoo.org/
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>  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)

> 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)

> 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.

Paul