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Simple proof of concept showing how you can abuse Discord's in-game internal module to draw on top of the game (even if the game is in fullscreen) from an external application without modifying any Discord files or loading its modules.

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OverlayCord

This project is a simple proof of concept that shows you how to hijack Discord's internal game overlay from an external process without modifying any Discord files, loading any Discord modules, or hooking anything.

How does it work?

Discord's whitelisted internal module (DiscordHook64.dll), which is loaded by games using SetWindowHookEx, simply copies the framebuffer from a memory-mapped file. The code snippet from this repo is pretty much self-explanatory:

typedef struct _Header
{
	UINT Magic;
	UINT FrameCount;
	UINT NoClue;
	UINT Width;
	UINT Height;
	BYTE Buffer[1]; // B8G8R8A8
} Header;

bool ConnectToProcess(ConnectedProcessInfo& processInfo)
{
	std::string mappedFilename = "DiscordOverlay_Framebuffer_Memory_" + std::to_string(processInfo.ProcessId);
	processInfo.File = OpenFileMappingA(FILE_MAP_ALL_ACCESS, false, mappedFilename.c_str());
	if (!processInfo.File || processInfo.File == INVALID_HANDLE_VALUE)
		return false;

	processInfo.MappedAddress = static_cast<Header*>(MapViewOfFile(processInfo.File, FILE_MAP_ALL_ACCESS, 0, 0, 0));
	return processInfo.MappedAddress;
}

Please note that this straightforward example uses very basic CPU rendering, which does not offer optimal performance. In addition, regardless of your intention to use GPU rendering (such as DirectX), the framebuffer will still be copied by the CPU.

Media

Video showing the example (in case embed does not work click here)

video

Image showing the example

pic1

Image showing custom project that renders using DX11

pic2

Image showing custom project rendering over anticheat protected game

pic3

About

Simple proof of concept showing how you can abuse Discord's in-game internal module to draw on top of the game (even if the game is in fullscreen) from an external application without modifying any Discord files or loading its modules.

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