Request Elevated Privileges in Windows Vista and 7 where UAC is enabled

This article explains how to request elevated privileges for windows applications running under Windows Vista or 7, where UAC is enabled.

If an application requires administrator right, you have to pass through the UAC elevation process. Three options available to do in this case:

1. Add a manifest file to the project and configure it to ask for elevation on each application start;
2. Separate the application part that requires admin rights into another process;
3. Rework the application so it won’t require admin rights, this one not being always possible as in my case.

There is always the fourth option, stopping UAC, but this may result in different damage to the system and should never be used.

The first option is the most simple; still it should be avoided if possible. When the UAC dialog box appears, is like someone asking you “Please, let me mess with your PC!”, and for an application that always runs as elevated… seams dangerous.

To add a manifest file to the project, right click the project in Visual Studio, select Add New Item and choose the Application Manifest File. The file added to the project contains comments which explain what you have to change to for the application to run as elevated. There are other configurations available in the manifest file; however, the following is all that is needed for obtaining admin rights:

<trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
 
<security>
 
<requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
 
<requestedExecutionLevel level="asInvoker" uiAccess="false" />
 
</requestedPrivileges>
 
</security>
 
</trustInfo>

The other available elevation levels are:

– “requireAdministrator”, this will force the UAC prompt, and the application will run with admin rights;

– “highestAvailable”, will use the highest privileges available for the current user.

Using the elevation level  ”asInvoker”, will use the same security token as the calling process, usually the desktop shell. If the application separation may be implemented, then it should be considered, this way the user may not be disturbed every time it starts the application, just when the user chooses to execute the specific application part. The elevation required part may be implemented in two separate ways:

– Using a manifest file to obtain elevation;

– Starting the process as elevated, everything done programmatically in this method.

The following snippet checks if the application is elevated and if not, it tries to restart itself requesting for elevation: C#:

WindowsPrincipal pricipal = new WindowsPrincipal(WindowsIdentity.GetCurrent());
bool hasAdministrativeRight = pricipal.IsInRole(WindowsBuiltInRole.Administrator);
 
if (!hasAdministrativeRight)
{
    ProcessStartInfo processInfo = new ProcessStartInfo();
    processInfo.Verb = "runas";
    processInfo.FileName = Application.ExecutablePath;
    try
    {
        Process.Start(processInfo);
    }
    catch (Win32Exception)
    {
	 /*Do nothing. Probably the user canceled the UAC window
         or provided invalid credentials.*/
    }
 
    this.Close();
    Application.Exit();
}

Try using the first two methods only if there is no way of using the third one, that of rewriting the application so it won’t require administrator rights anymore.
Additional material on this matter can be found here: Design Applications for Windows Vista.

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