Index

1. VNC

• stands for Virtual Network Computing
• it allows you to remotely view and control a PC desktop, and will run on a wide variety of operating systems
• VNC and Security
  • access to a VNC desktop means security is very important

2. VNC and security

• VNC uses encryption when making an initial connection
  • when you login
• however once connected
  • all VNC data is unencrypted
  • a malicious user could snoop your VNC session
• a number of VNC scanning programs exist
  • which will scan a subnet looking for PCs which are listening on one of the ports which VNC uses
• tunneling VNC over a SSH connection allows you to use VNC to access your computer
  • with all traffic strongly encrypted, and optionally compressed

3. Running VNC

• log into mcgreg and run vnc4server

• $ ssh mcgreg.comp.glam.ac.uk
  Password:
  $ vnc4server
  You will require a password to access your desktops.
  
  Password:
  Verify:
  
  
  New ’X’ desktop is mcgreg:1
  $ exit
  Connection to mcgreg closed.

• you will be prompted for a password, note this does not have to be the same as your login password
• note the New ’X’ desktop is value, write this down
• now run the vncclient from your start bar menu
  • you will need to give it the server name mcgreg.comp.glam.ac.uk:1
  • note that mcgreg.comp.glam.ac.uk:1 was used in this example, yours might be mcgreg.comp.glam.ac.uk:6 you need to check the output from when you ran vnc4server
• you will be prompted for your VNC server name
  • in this example it was: mcgreg.comp.glam.ac.uk:1
• now your will be prompted for your VNC password
• how many vnc4server s are being run on mcgreg?
  • hint use the command ps -aux and grep and wc to find this out
• now shutdown your vncclient and log into another GNU/Linux workstation and run vncclient again
  

4. VNC over SSH

• as VNC is insecure we can tunnel VNC traffic over SSH
  • VNC becomes as safe as SSH
• firstly we need to connect a secure pipe to the vnc4server running on mcgreg
• we initiate this from our GNU/Linux workstation

• $ ssh -g -A -X -N -T -L5901:localhost:5901 mcgreg.comp.glam.ac.uk

• now we start our xvncclient
  • however we tell it to connect to localhost:1
• which maps onto localhost:5901 , which is the other end of the secure pipe
• does the connection appear slower?
  • why?
    

5. Tidying up

• please shutdown your vnc4server once you have finished this tutorial

• $ ssh mcgreg.comp.glam.ac.uk
  Password:
  $ vnc4server -kill :1

• remember in your case :1 might be :6 as defined when you created the server instance
• finally examine the ssh manual page and find out what the parameters -g -A -X -N -T -L5901:localhost:5901 mean when given to ssh

Index

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