Nov
24
What is DNS Tunneling and how do you do it?????????
November 24, 2009 | Tagged dreamhost | Leave a Comment
I hope this will help every one with the question of how to bypass this block or how to unblock this… or I need a proxy to view this…
TCP-over-DNS tunnel software HOWTO
Q: How do I get free internet where I should have none?
A: Use tcp-over-dns tunnelling software.
We’ll show you how.
How it works
DNS stands for "Domain Name System". The purpose of DNS is convert a domain name, such as "analogbit.com" to an ip address, such as "208.113.168.166". The interesting thing about DNS queries is that they are usually recursive queries. This means that if a server doesn’t know the answer for a domain name, it is allowed to ask other servers for the answer. So while a firewall or restrictive ISP may filter regular internet traffic they probably overlooked DNS traffic.
tcp-over-dns diagramtcp-over-dns diagram
Hexdump of tcp-over-dns packetHexdump of tcp-over-dns packet
The tcp-over-dns client will encode data in an address and sends that out to the ISP’s dns server. The ISP’s dns server then realizes it cannot answer the question, so it forwards it onto the tcp-over-dns server. The tcp-over-dns server decodes the client’s data from the address and encodes the server’s data in the answer that is sent back to the client.
There are many things working against the efficiency of the tunnel. There are certain restrictions about what characters may be in a domain name (a-z, A-Z, 0-9, hyphen) so data is converted into the appropriate character set before transmission. The server’s answer to a query also has many restricted characters, so it too must do the same thing with a different set of characters. Every query that is answered by the DNS server must also include the question in the response. The combination of these restrictions means the total data transmitted is not very efficient compared to the number of bytes actually sent.
Requirements
1. An internet connection that has been intentionally crippled by the connection’s administator. A candidate connection will filter normal internet traffic, but it will allow DNS queries through. You can tell if it will work if when you ping a server you can get its IP address but all ping/tcp/udp packets are lost.
2. Server under your control where you are the root or administrator user. You need to be able to set up a server to listen on the DNS port (port 53). This can be a machine you are running at home, most (all?) ISPs do not filter dns traffic.
3. A domain name that you can use to direct queries to your server.
4. tcp-over-dns server and client software, as well as a functional Java Runtime Environment. It’s free!
Step 1 – Set up the domain
First you need to point the domain to the location of your server. If you want to squeeze out a few more bytes per query, try to keep the domain name as short as possible. Ultimately we need two DNS records. One that says that there is a name server for *.dnstunnel.domain.com. The next record says where you can find the ip address of the aforementioned nameserver.
Method 1:
If you have direct access to the the DNS record you can add something like this to the bottom of it:
;set up the DNS tunnel
$ORIGIN dnstunnel.analogbit.com.
@ IN NS ns.analogbit.com.
ns IN A <server ip>
Method 2:
Okay, maybe I’m a cheapskate, I don’t actually own a server where I can edit the DNS record directly. However I am in luck. Some of my users have brought http://freedns.afraid.org to my attention. You can use afraid.org with tcp-over-dns without even registering a domain name. Set up any two subdomains so they look like this.
freedns.afraid.org setupfreedns.afraid.org setup
Make sure you replace the A record with the ip address of your server. You can use various clients to update this A record automatically if you ip address changes. Read more about it on afraid.org’s webpage.
Method 3:
Our hosting company lets us edit our DNS record through a web interface. You can do the same thing if this sort of functionality is provided to you.
Dreamhost DNS SetupDreamhost DNS Setup
Step 2 – Setup the server
Download and extract the tcp-over-dns software to the server machine you are using.
Choose a port on the server you want the client to be able to access. Currently, there is no authentication, so keep security in mind. This works on any OS that runs java, and both TCP and UDP traffic is tunnelled through, so really any application you wish to use should work. Please note that you need to have a program running and listening on the –forward-port. You will connect to this program through the DNS tunnel.
Some of the best choices are:
* Proxy server (for basic web browsing)
* An openssh server on linux (for controlling the server and also works as a proxy)
* VPN server (your computer appears on the home network)
* VNC server (for access to your desktop at home)
The best choices are either the SSH po
sorry the bottom got cut off…
Go here to view the entire walkthrough http://analogbit.com/tcp-over-dns_howto
This is not for everyday use… this is for those that need to bypass some sort of firewall or software that is blocking certain sites… It is not intended for that kind of use… you can however encrypt the info being sent… it’s just a name server and not operating in the traditional sense of a proxy… I’ve not ever been able to unscramble the garbled mess of characters of DNS traffic any ways when it’s not encrypted… a better walkthrough is a video from Patchy and Nox of Infinity Exsist… http://www.infinityexsist.com
If i was to change my primary or secondary DNS address to a third party i would need to get assurances that it it will not reroute my bank links or other sensitive details.
So far i have seen none from any third party DNS service, so for security reasons i will stay with my IPS supplied DNS service who are home grown and can be trusted
The Plop | Oct 09, 2009