Secure DNS for DMZ Clients

BI BE BU VA Computer Science
Secure DNS for DMZ Clients
IT Security / Hansjürg Wenger / Daniel Walther, T-Systems Schweiz AG
Expert: Dipl. Ing. ETH Andreas Dürsteler, Swisscom AG
Internet without DNS is like shopping on a low budget - you will not go very far! DNS stands for Domain
Name System and functions like a phone directory: It converts names into numbers, or more precisely
domain names into IP-addresses. But what if you get a manipulated phone book? You would probably
discover very soon that you are not talking with the right person. On the internet, however, you would not
realise that you are on a wrong site! There are several dangerous scenarios that could happen if you get
wrong DNS data. And that’s the reason why DNSSEC is becoming more and more necessary.
Marc Bettler
David Schärer
Problem statement
In mid-2008 Dan Kaminsky published a proof of concept demonstrating that cache poisoning is
possible 1. This came as a terrible
shock to the IT world. T-Systems
Schweiz AG realized that this serious problem could be solved by
using secure DNS Servers and
wants to provide secure DNS
services to their customers. They
offer safe environments (Demilitarized Zones or DMZ) to allow
companies to have their internet
services outsourced. Therefore a
need for secure DNS arose. Our
challange was to ensure that the
integrity and the authentication
of DNS data were guaranteed.
Furthermore, the communication
between DNS servers has to be
protected against eavesdropping.
For our research we create a virtual environment similar to the
T-Systems’ situation, inside of
which the two Sun Solaris 10
servers run DNS Security Extensions (DNSSEC) and allow us to
examine how DNSSEC works.
This knowledge is then used for
creating a concept containing
recommendations on how to deploy DNSSEC as easily as possible. Apart from this, we test how
to achieve secure communication
between master and slave DNS
Resolve a DNS query with DNSSEC
Although experts are saying that
there is no reason to not deploy
DNSSEC, certain critics disagree.
Some of them do not rely on foreign «islands of trust», others worry that DNSSEC will drastically reduce the performance and speed
of servers. The fact is that the root
zone has to be signed as early as
possible, afterwhich DNSSEC will
finally become more popular. Network administrators will reconfigure their servers, and this will
lead to the annihilation of cache