Windows desktop sharing Dovydas Patapas, group 2

Content What is Windows Desktop Sharing? Where is it used? How does it work?

Windows Desktop Sharing – a service which allows users to see a remote graphical interface on their computer Windows desktop sharing – a functionality provided by the windows api, and used in applications which allow users to see a remote machine’s graphical user interface on their computer

Windows Desktop Sharing allows useful screen sharing capabilities, such as remote assistance, multiple-party conferencing and video communication Windows desktop sharing can be used to build applications that provide various screen sharing capabilities, such as remote assistance, multiple-party conferencing and video communication This particular part of the windows api is available on versions newer that Windows Vista (2007)

Windows Desktop Sharing vs Remote Desktop Services? Very similar use cases In the official windows api documentation there are 2 separate sections for Windows Desktop Sharing and Remote Desktop Services According to this documentation, Windows Desktop Sharing can transmit a local desktop over an RDP connection without creating an additional session, While with Remote Desktop Services RDP is also used, but a user session is always created.

RDP – Remote Desktop Protocol RDP server listens on TCP and UDP port 3389 RDP – a protocol created by Microsoft, provides a user with a graphical interface to connect to another computer over a network connection. RDP servers also exist for UNIX and OS X operating systems. By default, an RDP server can be accessed through network port 3389

A Session - a certain time frame for communication between two devices, two systems or two parts of a system An Interface - a shared boundary across which two or more separate components of a computer system exchange information In IT, the word Session refers to a certain time frame of communication between two devices or systems. An Interface – shared logical boundary with is used to exchange infromation between two or more systems or system components.

Windows Desktop Sharing – the sharer and the viewer RDPSession and RDPViewer objects Windows Desktop Sharing consists of two participants - the sharer and the viewer The sharer is the system whose screen is being shared out, while the viewer is the system that can view the sharer's screen. The main two objects that are created for windows desktop sharing are RDPSession and RDPViewer. RDPSession object is used to create a sharer instance, while RDPViewer object is needed to create a viewer instance All other objects are created and accessed through the methods of these two main objects

TheWindows Desktop Sharing process During the windows desktop sharing process, the system shares application objects though the network. Each application object contains, is referred to by a list of window objects So when an application object is shared, all its windows are shared too.

An Application Filter manages the shared desktop area at the window and process level. Applications can use enumerators to display lists of objects in the session that can be shared Windows Remote Desktop sharing process uses a so called application filter, that manages the shared desktop. In order for desktop sharing application to see which object can be shared in a session, they use enumerators.

Enumerator – an object that lists elements of some set An enumerator is something that is used to list a certain set of objects, in this case various properties Each object of a remote desktop viewer that is shared, has some of these properties

Security – client authentication via a ticket and a password. A viewer cannot take control of a shared application running as an administrator. When an attendee connects to a session, the client sends a ticket and a password These two pieces of information are used to authenticate the user in a desktop sharing session. Also, a viewer usually can not be granted admin rights to shared applications while in session.

If an application in a shared desktop or a shared application elevates, asks for administrator rights via the UAC prompt, remote viewer will not see it If some application requests elevation, meaning it requests the user to authenticate the application for higher access rights, the remote viewer won‘t see the prompt. This prompt is called the UAC prompt, or User Account Control prompt.

Thank you for your attention If an application in a shared desktop or a shared application elevates, the viewer will not see the UAC prompt