x11vnc setup

A x11vnc setup

This is based on a configuration I did for a customer. They wanted the following:

• that users could remote-desktop into an already-running desktop running on the system console;
• that users could initiate a session running on the console if one wasn't already running, and then use that; and
• that other users could connect to an already-running desktop, sharing access with the user who was already logged in.

As such, we set up two separate services:

x11vnc-5900: this is for the user to remote-desktop in to the session. If there is a session running, the user will be prompted for a password; otherwise he will be shown the gdm login screen.

x11vnc-5901: this is for other users to connect to the running desktop. The connecting user will not be prompted for a password, however the user on the running desktop will be shown a dialog prompting them to grant view-only or full control, or alternatively, dropping the connection altogether.

Prerequisites

This is for CentOS 5.x

• x11vnc (from rpmforge)
• xinetd

/etc/services:

Add to the end:

x11vnc-5900     5900/tcp                        # vnc
x11vnc-5901     5901/tcp                        # vnc

/etc/xinetd.d/x11vnc-5900:

service x11vnc-5900
{
        disable = no
        port                    = 5900
        socket_type             = stream
        protocol                = tcp
        wait                    = no
        user                    = root
        passenv                 = PATH
        server                  = /usr/local/sbin/run-x11vnc.pl
        server_args             = -m 5900
}

/etc/xinetd.d/x11vnc-5901:

service x11vnc-5901
{
        disable = no
        port                    = 5901
        socket_type             = stream
        protocol                = tcp
        wait                    = no
        user                    = root
        passenv                 = PATH
        server                  = /usr/local/sbin/run-x11vnc.pl
        server_args             = -m 5901
}

/usr/local/sbin/run-x11vnc.pl: Attached to this page.

Setup

Ensure you've run chkconfig xinetd on ; service xinetd start if this is a new installation of xinetd.

Each user should use vncpasswd to create a ~/.vnc/remote.passwd file.

Problems

• After successfully logging into the gdm, the vnc session gets disconnected; the user must then re-connect, this time being prompted for his remote.passwd file.

Security issues

• This does nothing to deal with the problem that the desktop session is being run on the console; therefore anyone passing by the real desktop will be able to see what is going on, and possibly control the desktop (ie fight with the remote user). But x11vnc has this problem anyways.