Is there a way for code to run with lower privileges, if Windows UAC is denied

user_15054785 0
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I'm trying to code a simple app in C for windows and I want it to run with elevated privileges. That's working fine, but I would like to make it work, with lower privileges, if the UAC prompt is denied by the user.

This is my manifest file:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> 
  <assemblyIdentity version="1.0.0.0"
     processorArchitecture="X86"
     name="reverse_shell"
     type="win32"/> 
  <description>Description of your application</description> 
  <!-- Identify the application security requirements. -->
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
    <security>
      <requestedPrivileges>
        <requestedExecutionLevel
          level="highestAvailable"
          uiAccess="false"/>
        </requestedPrivileges>
       </security>
  </trustInfo>
</assembly>

Sorry if I didn't specify it well enough...

I would like that my code works like this:

  1. User runs the program
  2. UAC shows up to ask for elevate privileges
  3. If user answers yes everything fine, if user answers no i would like my code to run with low privileges

Thanks for your help

uac administrator c manifest windows
3 Answers

By using a manifest, you inform the OS you complete program needs the requested privileges.

What you describe though, is a program with only one code path that actually needs these privileges, and another that does not. In this case, you would be better off programmatically requesting privileges from your program code, instead of through the manifest (which is handled by the OS before starting your actual application).

The problem is this isn't provided (as far as my quick google shows), so an alternative would be to write a wrapper (or keep the logic inside the same application somehow) that starts without permissions, then tries to run the actual program with elevated permissions, and if that fails, runs the actual program without elevated permissions.

user_2561380

Check the command-line of your program, whether it contains "-low". If it contains "-low" run the program with lower privileges. If the command-line of your program contains nothing, use IsUserAndmin to check, if the user is an Administrator. If true, run your code with higher privileges. If false, use GetModuleFileName together with ShellExecute and "runas" as lpOperation and check ShellExecute's return value. If the return value is 5, run your program using ShellExecute with"-low" as an argument. If it doesn't return 5, don't do anything.

user_8322200

It's nice to see that you are trying to use highestAvailable; unfortunately it cannot do what you want.

If the user declines the UAC dialog, the process is not launched.

What you can do instead is:

  • mark your application with asInvoker
  • when your app starts up, check if the user is an Administrator
  • ask the user if they would like to run the app as an administrator (i.e. kind of how UAC asks if you'd like to run as an administrator)
    • if they say No, continue your app as normal
    • if they say Yes:
      • relaunch yourself using ShellExecute with the runas verb
      • and exit your own process
user_125970
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