Remote Assistance and UAC prompts
Recently, I received some e-mail sent to one of our internal DLs describing an issue a customer is facing when using Remote Assistance:
My customers engineer requests to connect to a user’s machine via remote assistance.
The user accepts and the engineer requests to take control.
The user ticks the box to allow the engineer to respond to UAC prompts – then selects Yes.
However – this change requires admin rights and the user is prompted for admin credentials (which they obviously don’t have)
Is there a way to work around this?
Why, yes! Enter UIAccess.
The way Remote Assistance “remote control” feature works is through an OS feature called UIAccess, which allows the app the ability to control the desktop programmatically. By combining this with RDP/TS, Remote Assistance is able to provide the “remote control” feature.
However, in order for this to work properly in scenarios that prompt for elevation (i.e. UAC prompt), you have to enable a certain group policy:
User Account Control: Allow UIAccess applications to prompt for elevation without using the secure desktop
What this will do is it will enable Remote Assistance to show the UAC prompt on the user’s desktop, as opposed to the secure desktop. If you don’t enable this, the user being helped (call him novice) will get the prompt on his local machine – so the expert cannot interact with it since RA will only remote out the user’s desktop. At that point, the novice may not know what to do with it, and/or he may not have the administrator password. So it is important that you enable this group policy in order to have the UAC prompt show up in the user’s desktop and have RA remote out this dialog to the expert’s machine.
However, there was a bug with RA and how it determined where to show the UAC prompt. However I’m happy to say that my team fixed this bug recently, and you can now download a hotfix that should fix this issue.
You can download this hotfix here: http://support.microsoft.com/kb/2614066 (“Black screen during a Remote Assistance session in Windows Vista, in Windows Server 2008, in Windows 7, or in Windows Server 2008 R2”)