How to Create DNS Tunnel in Ubuntu Using Iodine

What is DNS tunnel?

• Technique to tunnel IPv4 data through DNS server.

Why do we use DNS tunnel?

• We use DNS tunnel when in situation where our internet access is blocked by firewall, but DNS queries is allowed (e.g: in office, hotspot internet).

Requirements:

• Ubuntu PC
• Iodine package
• Windows PC to test the tunnel
• Domain name

How to do?

1. Install Iodine package.
   

   # apt-get install iodine

2. Modify DNS record by add in subdomain record t1.id-ebook.com.
   

   t1 IN NS t1ns.id-ebook.com.
t1ns IN A 202.130.222.111

   IP address 202.130.222.111 is the server where Iodine will run.

3. Run Iodine server.
   

   # iodined -f -p 5353 10.0.0.1 t1.id-ebook.com

   We use port 5353, because port 53 is already in use by DNS server. That’s why we have to forward the traffic using iptables.

   # iptables -t nat -A PREROUTING -i eth0 -p udp --dport 53 -j DNAT --to :5353

4. In another PC running Windows XP, download Iodine software at http://code.kryo.se/iodine/. Extract and run Iodine client.
   

   C:\iodine\bin>iodine -f -r 202.130.222.111 t1.id-ebook.com

5. Test the connection by ping each other.
   In server:

   # ping 10.0.0.2

   In client:

   C:\iodine\bin>ping 10.0.0.1

6. To enable internet, activate IP forwarding and IP Masquerade.
   

   # echo 1 > /proc/sys/net/ipv4/ip_forward
# iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -o eth0 -j MASQUERADE

7. To modify default gateway in client (Windows XP), run ROUTE command.
   

   (run command prompt as Administrator)
C:\iodine\bin>route delete 0.0.0.0
C:\iodine\bin>route add 0.0.0.0 mask 0.0.0.0 10.0.0.1

8. Test by browse to google.com or yahoo.com
9. Finish.

Reference: Iodine