Wednesday 12 June 2013

Firewall Tunnelling using SSH & Putty

 Firewall Tunnelling using SSH & Putty
SSH (secure shell) is a protocol that allows two devices to exchange data with each other securely in an encrypted format, hence protecting data being transmitted. It usually uses the Port 22 for all connection.

PuTTY is a free, open source client that allows user to establish connection using SSH, Telnet and other network protocols with remote systen, it can be downloaded free for cost from http://www.putty.org/. Putty is also available as a portable application that you can run from your USB Pen drive.


There are numerous step involved in firewall tunnelling using SSH & Putty.
Step 1: You need to either set up your own SSH Server with unblocked Internet access or ragister an account on a SSH Server that has unblocked access to the Internet, This SSH Server can be in any part of the world.

Step 2: Use putty to create an encrypted SSH connection to the Remote SSH Server. (Outgoing Port 22, encrypted communication will be allowed by most local firewalls.) Putty opens a local port that you can now connect to in order to access the remote SSH Server.

Step 3: Once you have connected to the remote SSH Server that has unblocked access to the Internet.

Now that we know, we know the broad steps that are involved in SSH Tunnelling, let us get down to the specifics. Let us assume that your firewall has blocked outgoing connections to remote port 25 & 80 and you want to use putty and SSH to bypass this blocking mechanism and access the remote systems.
Step 1: Download putty and click sesson. In the host name field enter the IP Address of SHH Server that you want to connect to. In the port field enter 22.

Step 2: Click on Connection >SSH> Tunnels and enter the IP Addresses and port numbers of the blocked remote systems you wish to tunnel to. For example, i entered 110 in the source port field & 192.168.0.11:110 in the Destination field then clicked on Add. Repeat this for all blocked systems and ports you which to tunnel to.

Step 3: Based on configuration, now the local port 80 on your system will connect to port 80 on 192.168.0.1 (Using SSH Connection to SSH Server) and the local port 25 will connect to port 25 on 192.168.0.22 (Using SSH Connection to SSH Server) and so on.

STEP 4: Now click on the Open button, You will be prompted to enter the SSH Server username or password. You would have recieved it when you created an account on the remote SSH server. Putty now start to listen to port 80 and port 110 on the local system. Now in order to access the port 80 on 192.168.0.1, you need to start your browser or any other tool and simply type local host:80 or local host: 110 and press enter!

Enjoy...

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