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Re: Wired captive portal pen-test
From: "JosŽé M. Palazón Romero" <josem.palazon () gmail com>
Date: Wed, 16 Jul 2008 09:28:19 +0100

Sergio Castro escribió:
So yes, if you only see broadcast ARP requests from the router, the switch
is very likely securely configured.

This is incorrect, Sergio. ARP replies are not broadcast, so it's perfectly ok that he doesn't see them.

Did you try using Cain? You may be able to do ARP poisoning with it and
intercept traffic between the router and IPs in your same subdomain.

If the switch were secured, then this wouldn't work either. Not even an ARP spoofing would work. The only option would be to find a flaw in the switch firmware or to trick it in such a way that, as most switches do, that it doesn't know how to behave anymore, and it starts acting as a hub. But it's unlikely that you find this in any modern switch. Have you tried to atack the switch itself? Try the firsts and the lasts IPs in your network. If the switch is advanced enough to filter that way, then it has a way to setup that, and probably that's a web interface. Try also uPNP. It's no authenticated, so if it's enabled, is your lucky day.

Anyway, I still think they are probably not filtering at layer 2.


- Sergio

-----Mensaje original-----
De: Roman Medina-Heigl Hernandez [mailto:roman () rs-labs com] Enviado el: Lunes, 14 de Julio de 2008 02:34 p.m.
Para: Sergio Castro
CC: pen-test () securityfocus com
Asunto: Re: Wired captive portal pen-test

Sergio Castro escribió:
I've done similar voipsec audits at hotels. The hotel is very likely using a switch-router (and very likely VLANs) so you will not be able to see any other IPs on the network. What is your sniffer showing?

I saw ARP requests coming from the router and asking for the MAC of several
other IPs of the same segment where my laptop was connected (in my case,
192.168.9.x). I didn't catch any ARP responses...

Another probe I did was walking to a "public computer" in the hotel (some
kind of internet-kiosk) and get the IP. The IP was in the same 192.168.9.x
range. I didn't have time to get its MAC and try to configure my laptop's
NIC with that MAC (although the switch should probably stop that... shouldn't it?).

Another possible attack vector you may use is their IP phones. If the room has an IP phone, try connecting your laptop to the phone's RJ45 and do a packet sniff. I've been able to access entire corporate LANs
doing this.

I didn't have a look at this... although I'd guess it was rj-11... Next time
I'll check it! :)

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