Forwarding
F-Secure SSH Client supports forwarding ("Port Forwarding and X Forwarding"), in which another network connection can be passed through SSH to encrypt it. It is also called tunneling because the SSH connection provides a secure "tunnel" through which another connection may pass. Both TCP port forwarding (local and remote) and X forwarding are supported.
Port Forwarding
Each F-Secure configuration you create may have different ports forwarded. To set up forwarding to a particular remote host, disconnect from that host (if you're connected), open the Properties window, and notice the Tunneling category. Select Local Tunneling to set up local forwarding (see Figure 16-2), or Remote Tunneling for remote forwarding, respectively. ["Comparing Local and Remote PortForwarding"] Either way, you are prompted for similar information:
- Source Port:
- The local port number
- Destination Host:
- The remote hostname
- Destination Port:
- The remote port number
- Application to Start:
- An external application to be launched when this port is forwarded
Figure 16-2. F-Secure SSH Client local port forwarding options
For example, to tunnel a telnet connection (TCP port 23) through SSH to connect to server.example.com, you can specify:
Source port: 8500 (any random port number)Destination Host: server.example.comDestination Port: 23Application to Start: c:\windows\telnet.exe
Once you've made your choices, reopen the SSH connection, and the ports will be forwarded for the duration of your connection.Note that F-Secure SSH Client forbids remote connections to locally forwarded ports. This security feature is analogous to specifying "GatewayPorts no". ["Local forwarding and GatewayPorts"]
X Forwarding
The X Window System is the most popular windowing software for Unix machines. If you want to run remote X clients that open windows on your PC, you need:
- A remote host, running an SSH server, that has X client programs available
- An X server running on your PC under Windows, such as Hummingbird's eXceed
SSH makes your X connection secure by a process called X forwarding. ["X Forwarding"] Turning on X forwarding is trivial in F-Secure SSH Client: open the Properties window, select Tunneling, and put a checkmark in the box Enable X11 Tunneling. You may also select the X display number, which you also may change during your SSH session.To secure an X connection by forwarding it through SSH, first run F-Secure SSH Client and establish a secure terminal connection to the SSH server machine. Then run your PC's X server, disabling its login features such as XDM. Now simply invoke X clients on the server machine, and their windows will open on your local X display.