Re: Exploitation of unused IPv6-capabilities

[Sebastian Krahmer <krahmer () suse de>]

Hi,

The papers pointed to by the others are basically straight
forward and not really new issues if you know how
ARP poisoning works. The thing that makes me wonder
and adds some new points is

'As soon as the "victim" has an IPv6 address issued by your radvd it will
 prefer AAAA-entries over A-entries'

What do you mean by that? I looked at the glibc resolver,
it might be that if getaddrinfo() does not get proper
ai_family arguments of AF_INET, it will accept AAAA records.
So, the application which thinks is using IPv4 DNS resolving
will eventually connect using IPv6?
This however will require built-in functionallity in the
application (for example ssh client has it) and you need to
play DNS tricks. Or I am completely mistaken and
dont understand what you mean with the A-records?!

Sebastian

On Sun, Jan 18, 2009 at 10:17:44PM +0100, Lukas Th. Hey wrote:

> Hi folks,
>
> while playing around I had an idea for some "new kind of mitm" which
> works quite well here.
>
> Affected:     All operating systems with unused IPv6 capabilities
>               listening to router advertisements (radvd for example)
>
> Attack:               Have an IPv6 tunnel with appropriate prefix delegated.
>               Configure your machine to propagate the prefix and
>               switch on IPv6 routing.
>
> As soon as the "victim" has an IPv6 address issued by your radvd it will
> prefer AAAA-entries over A-entries and connect via your tunnel where
> you're waiting with a password sniffer of your choice ;).
>
> This works in any computing center where you have colo'ed you box, have
> a dedicated system or...simply physical access. During my
> proof-of-concept I was able to intercept SMTP, HTTP and DNS sessions. It
> should also work in LANs (lanparties, corporations). The "danger" of
> misled connections will dramatically increase with the increasing amount
> of ISPs also offering services usable via IPv6. 
>
> Advisory:     Turn off your sever's/client's entire IPv6 capability or
>               at least the capability to catch up router
>               advertisement messages
>
> I hope you find the contents of my mail useful, entertaining or at least
> noch entirely shitty.
>
> Night!
>
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-- 
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~ krahmer () suse de - SuSE Security Team
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