Executing Code as a Control Panel Item through an Exported Cplapplet Function

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Executing Code as a Control Panel Item through an Exported Cplapplet Function

This is a quick note that shows how to execute code in a .cpl file, which is a regular DLL file representing a Control Panel item.
The .cpl file needs to export a function CplApplet in order to be recognized by Windows as a Control Panel item.
Once the DLL is compiled and renamed to .CPL, it can simply be double clicked and executed like a regular Windows .exe file.
Code
item.cpl
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// dllmain.cpp : Defines the entry point for the DLL application.
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#include "stdafx.h"
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#include <Windows.h>
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​
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//Cplapplet
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extern "C" __declspec(dllexport) LONG Cplapplet(
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	HWND hwndCpl,
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	UINT msg,
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	LPARAM lParam1,
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	LPARAM lParam2
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)
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{
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	MessageBoxA(NULL, "Hey there, I am now your control panel item you know.", "Control Panel", 0);
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	return 1;
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}
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​
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BOOL APIENTRY DllMain( HMODULE hModule,
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                       DWORD  ul_reason_for_call,
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                       LPVOID lpReserved
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                     )
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{
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    switch (ul_reason_for_call)
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    {
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    case DLL_PROCESS_ATTACH:
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	{
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		Cplapplet(NULL, NULL, NULL, NULL);
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	}
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    case DLL_THREAD_ATTACH:
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    case DLL_THREAD_DETACH:
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    case DLL_PROCESS_DETACH:
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        break;
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    }
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    return TRUE;
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}
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Once the DLL is compiled, we can see our exported function Cplapplet:
Demo
Below shows that double-clicking the .cpl item is enough to launch it:
CPL file can also be launched with control.exe <pathtothe.cpl> like so:
or with rundll32:
[email protected]
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rundll32 shell32, Control_RunDLL \\VBOXSVR\Experiments\cpldoubleclick
\cpldoubleclick\Debug\cpldoubleclick.cpl
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References
Staying Hidden on the Endpoint: Evading Detection with Shellcode | Mandiant
DueDLLigence/DueDLLigence.cs at master · mandiant/DueDLLigence
GitHub
Using CPLApplet - Win32 apps
docsmsft

Control Panel Item

Code Execution through Control Panel Add-ins

Last modified 2yr ago

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