Topic 4.1

UAC

Windows User Account Control

With Windows Vista or above, the correct way to mark a program is to embed an application manifest within your application that tells the operating system what the application needs. There are attributes within this application manifest that permit developers to specify their programs level of execution or requested execution level.

The request level options are as follows:

Request Levels
  • As Invoker – The application runs with the same access token as the parent process. (Recommended for standard user applications)
  • Highest Available – The application runs with the highest privileges the current user can obtain. (Recommended for mixed-mode applications)
  • Require Administrator – The application runs only for administrators and requires that the application be launched with the full access token of an administrator. (Recommended for administrator only applications)
  • No Execution Level Information – The application does not have an embeded request execution level manifest.

When making a PAF it can be good practice to embed an application manifest file with a request execution level. Operating systems earlier than Windows Vista ignore the required execution level specified in the application's manifest.

The benefit of elevating your PAF is that privileges are elevated only once (if necessary) and these privileges are inherited by all of the process' that are executed from your PAF without requiring multiple elevation prompts. In most cases, running an application with elevated privileges on Windows Vista and above is not recommended and as such you should really try to just use asInvoker where you can.

Unless an application is designed to be run exclusively by system administrators, it should be run with the least privileges possible.
No Execution
On Windows Vista and above, when no execution level information is set in the application's manifest and the application is not elevated previously the application runs in "legacy mode" for backwards compatibility support. In this mode the operating system uses a virtualization mechanism for the file system and registry to access. This means that its attempt to create or change files in restricted folder locations or to write in registry restricted hives is redirected (reflected) towards a "per-user" accessible location. See VirtualStore for more information on how this applies here.
Heuristic
Windows Vista or above heuristically detects installation, updater, uninstallation programs and requests administrator credentials or administrator approval in order to run with access privileges. This heuristic detection checks such attributes like: filenames, keywords, versioning resources, etc. (e.g. keywords like: "install", "setup", "update", etc.). Note that this detection heuristic applies only if you do not add requested execution level information to the application's manifest. Beware, if you do not set an execution level information your application might be easily mistaken as an application that needs administrator privileges.
Manifests

Below is the code needed for adding a manifest in your PAF. This code should go somewhere within PortableApps.comLauncher.nsi towards the beginning of the file. You can download the required files to use this code for your PAFs just below the example code. These files should be placed in a folder called Manifests inside the Contrib directory in the NSIS application folder. So if you are using this with your NSISPortable, then the full filepath would look like the following: X:\PortableApps\NSISPortable\App\NSIS\Contrib\Manifests

Example
;!define RequestLevel User
;!define RequestLevel Admin
!define ResHacker    `${NSISDIR}\Contrib\Manifests\ResHacker.exe`
!define ManifDir     `${NSISDIR}\Contrib\Manifests`
!define Manifest     `NSIS_2.46_Win8`
!packhdr             `$%TEMP%\exehead.tmp` `"${Reshacker}" -addoverwrite "%TEMP%\exehead.tmp", "%TEMP%\exehead.tmp", "${ManifDir}\${Manifest}_${RequestLevel}.manifest", 24,1,1033`

You would uncomment line 1 or line 2 depending on your particular needs. Remember to try and use asInvoker or User when possible.

Downloads
Manifests (38 hits)