SSH Tunneling

SSH tunneling, both reverse and local, is a technique used to establish secure connections between two computers over an untrusted network. While both types of tunneling serve similar purposes, they operate in different directions and have distinct use cases:

1. Local Port Forwarding (Local Tunneling):

   • Direction: Local port forwarding allows the client to forward traffic from a local port on their machine to a remote server through an SSH connection.

   • Use Case: It is commonly used to access services on a remote server that are not directly accessible from the client's machine due to network restrictions or security configurations. For example, accessing a web server running on a remote machine's private network.

   • Example: In the scenario described earlier, PC-1 is forwarding traffic from its local port 80 to the attacker's machine. This is an example of local port forwarding.

   
2. Reverse Port Forwarding (Reverse Tunneling):

   • Direction: Reverse port forwarding, also known as remote port forwarding, allows the server to forward traffic from a remote port back to the client's machine through the SSH connection.

   • Use Case: It is useful when the client's machine is behind a firewall or NAT (Network Address Translation), and the server needs to access services running on the client's machine.

   • Example: Suppose you have a device (such as a Raspberry Pi) behind a firewall, and you want to access its SSH service from an external server. You can establish a reverse SSH tunnel from the device to the server, allowing you to SSH into the device from the server.

In summary, local port forwarding is used to access remote services from the client's machine, while reverse port forwarding is used to make local services accessible from a remote server. Both techniques leverage SSH for secure communication and are valuable tools in network troubleshooting, remote access, and secure communication setups.