Possible DOS attack in the .nu domain service

[shane () CM NU (Shane Wegner)]

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Hello all,

I am not sure if this is known or even relevant to the list and if not,
please excuse this post.

There appears to be a bug in the niu DNS setup process which could result
in a DOS attack for those using their domains.  For those unfamiliar with
niu, they provide sub-domain service under the .nu domain to machines
which do there own DNS.  I have written to them on several occasions about
this issue but as of yet have received no response.

OK the bug is that any user who is willing to pay the $25 to register a
=2Enu domain can knock out or redirect a host under another.  This is best
shown through an example.

I register mycompany.nu and in the registration form enter the hosts I
have doing the DNS for it.

Name: mycompany.nu
DNS1: machine.someserver.com
DNS2: machine2.someserver.com

After this step, my DNS entry in the .nu table looks like this

$ORIGIN nu.
mycompany       IN      NS      machine2.someserver.com.
                IN      NS      machine2.someserver.com.

mycompany.nu for the sake of this example had the following DNS table.

$ORIGIN nu.
mycompany       IN      SOA     mymachine.mycompany.nu. hostmaster.mycompany.nu. (
                1 301 120 604800 600 )
                IN      NS      machine1.someserver.com.=20
                IN      NS      machine2.someserver.com.
$ORIGIN  mycompany.nu.
mymachine       IN      A       192.168.1.1

So Al's well until someone registers evil.nu with the goal of knocking out
myserver.mycompany.nu.  On the form, they enter the following.

name: evil.nu
DNS1: mymachine.mycompany.nu
DNS1IP: 127.0.0.1

Now here's the bug, if you enter an IP for a machine which falls under the
=2Enu name-space, it maps it statically.  It does not check to see if it
falls under your name-space.  Therefore, our evil.nu entry in the .nu
table looks like this.

$ORIGIN nu.
evil            IN      NS      mymachine.mycompany.nu.
$ORIGIN mycompany.nu.
mymachine       IN      A       127.0.0.1

So the IP for mymachine.mycompany.nu has been redirected from its
192.168.1.1 to 127.0.0.1.  An attacker could conceivably redirect the mail
servers of a company to his own machine or anything to that effect.

Regards,
Shane

--=20
Shane Wegner: shane () cm nu
Tel: (604) 930-0530
Sysadmin, Continuum Systems: http://www.cm.nu
Personal website: http://www.cm.nu/~shane
ICQ UIN: 120000
PGP: keyid:       2048/F5C2BD91
     Fingerprint: 8C 48 B9 D8 53 BB D8 EF
                  76 BB DB A2 1C 0D 1D 87

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