Creating a proxy DLL

[amateur]

Hi.

I would like some help on some advanced subject for me. I'm doing my first steps to create a proxy dlls for practice. I use VS2008 and 2010.

So assuming i have a simple crackme. Ηypothetically to get the registered message, offsets with patches are: 0x1234: 73->90 and 0x1235: 33->90.
 

offsets[]  = {0x1234, 0x1235};
srcbytes[] = {0x73, 0x33};
rplbytes[] = {0x90. 0x90};

Ok with this. Now i will explaing what i do quickly.

I try to locate possible dlls and i'm finding, hypothetically again, "version.dll". (Using Procomon -> filters: Procces name..is ->  crackme.exe, Path...ends -> dll, Result...contains -> NAME NOT FOUND).

Alright.  In VS Studio now. Creating a DLL project (no precompiled headers, and checked export symbols). And we have the basic template:

// dllmain.cpp : Defines the entry point for the DLL application.
#include "stdafx.h"

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
					 )
{
	switch (ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:
	case DLL_THREAD_ATTACH:
	case DLL_THREAD_DETACH:
	case DLL_PROCESS_DETACH:
		break;
	}
	return TRUE;
}

I don't know if i do something wrong up to here. Do i?

In this step now, can someone guide/help me on how to apply on this template, the hypothetical patches at the specific offsets that i have mentioned in the small C code snippet, to study the filled template further.

Practical, i think i do mistakes regarding the APIs: WriteProcessMemory, ReadProcessMemory, LoadLibrary and the other related API's that are needed to make it work.

The only things i can do at the moment are: to add messageboxes, splash screens

I haven't found a tutorials or something that fits to my needs yet, so any help would be appreciated!

Thanks all!

Edited November 30, 2021 by amateur