Authenticating with x11vnc: what's the difference between -auth and -rfbauth?

Question

I'm on xubuntu 11.10 trying to setup x11vnc server.

I followed instructions here and I can connect to VNC server - but it never asks me for password!

Is there a difference between these 2 options:

-auth file
and
-rfbauth passwd-file

Or why wouldn't my VNC client (remmina) ask for password. any clues?

UPDATE: OK. - I've added -rfbauth option and now authentication works with that single password.

I can connect and prompted for password:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -display :0 \
-auth /var/run/lightdm/root/:0 -forever -bg -o /var/log/x11vnc.log \
-rfbauth /etc/.x11vnc.pass

I can connect but NOT! prompted for password:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -display :0 \
-auth /var/run/lightdm/root/:0 -forever -bg -o /var/log/x11vnc.log

I don't get - what is the reason for -auth option then if not for authentication?

Answer 1

x11vnc -auth $XAUTHORITY starts a VNC server where you authenticate with an X cookie. A cookie is a byte sequence that is randomly generated when the X server starts and which (under most setups nowadays) any application that wants to connect to the X server must provide. The cookie is typically stored in a file called ~/.Xauthority or indicated by the XAUTHORITY environment variable. You can manipulate cookie files with the xauth command. You would not normally type X cookies manually; rather, you'd copy them with judicious use of cp (and commands such as ssh may copy them automatically). A common use case is x11vnc -auth guess, which says to use the same cookie when going through the x11vnc channel as when connecting to the X server directly.

x11vnc -rfbauth $RFB_PASSWORD_FILE starts a VNC server where you authenticate by typing a password. If you don't specify -rfbauth, anyone can connect to the VNC server (but not then connect to the X server unless they know the X cookie or your X server accepts connections without a cookie).