Dynamic SSH tunnel

Dynamic SSH tunnel, also known as dynamic port forwarding allows the creation of a SOCKS proxy, allowing traffic to be relayed through the SSH connection. SOCKS, which stands for Socket Secure, is a network protocol that facilitates exchanges of network packets between a client and a server through a proxy server.

Dynamic tunneling is enabled with the -D flag, with the supplied values: [local_address:]local_port

$ ssh user@server -D [local_address:]local_port

To test the configurations, we can use the cURL command with the --socks5 or -x options.

Eg. Suppose we have a remote server at the address 10.10.10.10 (running SSH at default port 22). We want to configure a proxy on our localhost at port 8888, that tunnels and proxies all traffic through the remote server.

$ ssh user@10.10.10.10 -D 127.0.0.1:8888

# Test the configurations
$ curl [destination_addr] --socks5 127.0.0.1:8888
$ curl [destination_addr] -x socks5://127.0.0.1:8888

The source address as seen from the destination address server will be that of 
# the remote server at 10.10.10.10

The source address as seen from the destination address server will be that of the remote server (10.10.10.10).