How Can I Execute an In-Memory EXE using CreateProcess?

Execute an In-Memory EXE Using CreateProcess

Introduction:

Creating a process from a memory buffer in CreateProcess presents a unique challenge. This article explores a method that allows you to do this, eliminating the need to write the executable to a file before execution.

Background:

In the gaming industry, distributing unencrypted executables can lead to DRM circumvention. To address this concern, game developers often send encrypted EXEs to distributors who wrap them with proprietary DRM before releasing them to players.

Creating a Patching Solution:

When a crash occurs in the EXE, it can take days or weeks to distribute a patch through DRM channels. To expedite the patching process, developers can embed the original EXE within an encrypted datafile. This allows for easy patching without affecting the DRM.

Implementation:

The solution involves creating a process from the in-memory EXE using CreateProcess with the CREATE_SUSPENDED flag. This flag allows time to modify the suspended process before execution.

Retrieving Process Information:

By obtaining the thread context of the suspended process, you can access the Process Enviroment Block (PBE) structure. The PBE contains the base address of the image, which is crucial for further manipulation.

Loading the In-Memory EXE:

Once you have the base address, you can load the in-memory EXE into the memory space of the suspended process using WriteProcessMemory. However, it may be necessary to adjust alignment or allocate additional memory depending on size and alignment differences.

Patching and Execution:

To complete the process, patch the base address of the in-memory EXE into the PBE of the suspended process and update the thread context with the new entry point. Finally, use ResumeThread to resume execution of the modified process from the in-memory EXE.

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