Dynamic DNS "Spoofing" & IRC

[Intel Nop]

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
username@spooftest.domain.com

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
there.

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".

0x90
www.invisiblenet.net

[Markus Kovero]

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
> username@spooftest.domain.com
>
> 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
> there.
>
> 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".
>
> 0x90
> www.invisiblenet.net
>
>
>
>

[c4]

Well you dont even have to have dyndns... just control over the over the
domain is sufficient.
Just connect and change the dns afterwards...

This dosn't have anything to do with dns & irc really... it just utilizes
the fact that your ircclient performs a dns check seperatly.

The problem with rechecking dns is that for a pretty large network such as
ircnet or efnet it would take some resources to do this check, thus
allowing a denial attack being made more easily against one server.

At 23:47 2003-05-01, you 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
>username@spooftest.domain.com
>
>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
>there.
>
>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".
>
>0x90
>www.invisiblenet.net

[Niels Bakker]

* 0x90@invisiblenet.net (Intel Nop) [Fri 02 May 2003, 17:10 CEST]:
> 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.
[..]
> 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).

You can retrieve the IP address of any user on irc via the STATS L
command (the uppercase L is important).

For privacy reasons some networks (most notably Undernet but also
Freenode) have disabled this command for users that do not have IRC
Operator status.


-- Niels.

--
Note: some countries impose serious penalties for a conspiracy to overthrow
the political system. THIS DOES NOT FIX THE VULNERABILITY.

[Thomas Wouters]

this would mean if you get disconected from the irc server and reconed you
would not have any reverse at all, so the 'real' hack isn't there your just
'abuseing' the fact that ircd's dont lookup the hosts while your are
connected

like almoste every deamon does (like sshd/apache enz)

-- Thomas

----- Original Message -----
From: "Intel Nop" <0x90@invisiblenet.net>
To: <bugtraq@securityfocus.com>
Sent: Thursday, May 01, 2003 11:47 PM
Subject: Dynamic DNS "Spoofing" & IRC



> 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.
>


--------
Thomas Wouters - xhoy
e-mail: Thomas@xhoy.nl
IRC: IRCnet - #IceBox & #ne2000 | EFnet - #IceBox

* ne2000 - Press Any Key To Continue | http://www.ne2000.nl *
* IceBox - SLUT partner | http://slut.icebox.nl *
--------

[Darren Reed]

In some mail from Intel Nop, sie said:
>
> 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.

Bah! Why do people still expect to have any sort of privacy ?!

Haven't you all gotten over it yet and realised that anyone can
know anything and everything about your life if they have enough $$ ?!

Privacy is such a 20th century concept, get with the times!

Oh, and btw, revealing user@hostname was quite a deliberate design
decision that was debated many times (and probably still is.)

IRC is meant to be a means for communicating with people and when
you're communicating with someone you generally want to know something
about them. Revealing user@hostname was not ever considered to be a
privacy risk and you might argue is no different to CLID. I for one
refuse to answer the phone if I cannot see who the other party is that
is calling me because it is generally considered good etiquette to let
someone know who you are when calling. Revealing more information also
serves as something of a disincentive towards anti-social behaviour and
before you say "but if someone wants to be, they can use methods like
that posted to hide", history shows that for most it is either too
difficult or too much trouble for the average moron to do.

Another reply mentioned "stats L" output being useful. Well at one
point it was, but today IRC is, for better or worse, far from being
anything as egalitarian as it used to be.

Darren