Re: Dynamic DNS "Spoofing" & IRC
From: Markus Kovero (muikku_at_muikkuverkko.net)
Date: Fri, 2 May 2003 18:26:24 +0300 (EEST) To: Intel Nop <email@example.com>
We have in Darkmyst ( http://www.darkmyst.org ) this thing called hostname
verification or smthin:
21:36 [nla] !xx.xx.xx.darkmyst.org *** Notice -- IP# Mismatch:
24.xxx.177.xxx != wv-xxx-ubr-b-xxx-196-xxx-130.charterwv.net[82b19f18]
Don't know exactly how it works, probably kills user with fake hostname.
We're using somekind modified darkhex ircd atm and we're coding new one
which is in beta-stage now.
cheers and happy "vappu"-holidays; Markus Kovero
On Thu, 1 May 2003, Intel Nop wrote:
> This is a trivial "feature/flaw" I've been holding onto for a bit, and it's
> probably commonly known, but I haven't seen it posted anywhere, more of a
> neat little thing in taking advantage of IRC and it's treatment of dyndns
> within DNS if reverse lookup is possible.
> IRC (Internet Relay Chat) servers being a common ground for chat, have some
> annoyances such as the username@ipaddress or username@domainname, some
> people don't like that etc, being that they have to use a bouncer to avoid
> showing their own ip address or hostname to other users if they want to
> maintain some sort of privacy.
> Well here's a pseudo-privacy trick that can be reasonably easy to perform
> given one has control of a dns server that performs reverse and forward
> lookups, support for dyndns scripts, and a domain-name registered to you.
> You can optionally use a bouncer if you want.
> In my example, I will use the host name spooftest.domain.com, a port
> forwarding tool, a zoneedit account with my dyndns script that forward
> resolves, and a friend's server (he/she runs an isp) that allows for me to
> have an PTR record to the ip address "10.1.1.1" (<-- this is a private
> address for demo purposes) on his server as spooftest.domain.com
> Step 1) I have zoneedit script set up to tell it that my dyndns address is
> to spooftest.domain.com is 10.1.1.1, which it updates immediately and the
> 10.1.1.1 server has PTR record for 10.1.1.1 as spooftest.domain.com (thus
> allowing reverse and forward lookup of spooftest.domain.com)
> My portforward (say we're using datapipe.c on the 10.1.1.1 box)
> settings are datapipe 10.1.1.1 6667 irc.whateverserver.net 6667
> Step 2) Log into irc server on your local machine by doing a /server
> spooftest.domain.com 6667, make sure the irc server has resolved you as
> Step 3) Run your dyndns script for zoneedit to assign your ip address as
> whatever ip you want (in this case I'll use 127.0.0.1), then wait about a
> minute before joining a channel.
> By this time, your dyndns should have updated and changed your ip address to
> 127.0.0.1, and irc servers don't re-check after you've connected (so anyone
> resolving your hostname will come up with 127.0.0.1).
> I don't know if this is categorized as a flaw in dns or irc, or just merely
> exploiting a feature, and this is a rather trivial trick (surely can't be
> original and I apologize if it's been posted before).
> A fix I think would have ircd recheck after a certain amount of time for
> resolving properties of their dns, and I was going to say dnssec, but I
> can't really see that fixing the problem unless ircd re-checks as well
> This "feature/flaw" could probably apply to other application protocols as
> well that do not recheck dns properties, but I haven't taken the time to
> come up for other practical uses for it.
> This has been tested on most ircd server versions and all so far are victim
> to this "hack".