How to write process memory with multilevel pointer with c++?

Question

I'm trying to make a cheat for RE2. I found memory's with pointer-scan with cheat engine. My code is not working :(

#include <iostream>
#include <windows.h>

using namespace std;

int main() {
    int newValue = 10 ;
    HWND hwnd = FindWindowA(NULL, "RESIDENT EVIL 2");
    if ( hwnd == NULL )
    {
        cout << endl << "Process handle not found !" << endl;
        return 0 ;
    } else {
        DWORD pId;
        GetWindowThreadProcessId(hwnd, &pId);
        HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pId);
        if(!hProc) {
            cerr << "Cannot open process !" << endl ;
        } else {

            int c = WriteProcessMemory(hProc, (LPVOID)0x707B6D0 + 0x80 + 0x78 + 0x98 + 0x50 + 0x18, &newValue, (DWORD)sizeof(newValue), NULL);
            if (c>0) {
                clog << "yes" << endl ;
            } else {
                clog << "no" << endl ;
            }
            CloseHandle(hProc);
        }
    }
    return 0;
}

I can send you .net or C# if you want that instead. Are you grabbing the clients name correctly? Make sure its not dynamic. — John Kens, May 10 '19 at 20:20

Remy Lebeau · Answer 1 · 2019-05-10T22:58:28.000

You are misinterpreting what Cheat Engine is showing you.

In your code, 0x707B6D0 + 0x80 + 0x78 + 0x98 + 0x50 + 0x18 equals 0x707B8C8, which is NOWHERE even close to the value of 0x0EC1A3F0 that you are trying to reach.

What you need to do instead is:

First, read a pointer that is stored at the base address 0x707B6D0 (the value read is 0x128BFBB0).
Then, add 0x18 to that pointer (0x128BFBB0 + 0x18 = 0x128BFBC8) and read a new pointer at that address (the value read is 0x128564D0).
Then, add 0x50 to that pointer (0x128564D0 + 0x50 = 0x12856520) and read a new pointer at that address (the value read is 0x0F2EC940).
Then, add 0x98 to that pointer (0x0F2EC940 + 0x98 = 0x0F2EC9D8) and read a new pointer at that address (the value read is 0x0F2EB2B0).
Then, add 0x78 to that pointer (0x0F2EB2B0 + 0x78 = 0x0F2EB328) and read a new pointer at that address (the value read is 0x0EC1A370).
Then, add 0x80 to that pointer (0x0EC1A370 + 0x80 = 0x0EC1A3F0), and write your data to that address.

Try something more like this:

#include <iostream>
#include <stdexcept>
#include <memory>
#include <windows.h>

DWORD_PTR readPointerFromProc(HANDLE hProc, DWORD_PTR baseAddr)
{
    DWORD ptr;

    if (!ReadProcessMemory(hProc, reinterpret_cast<LPVOID>(baseAddr), &ptr, sizeof(ptr), NULL);
        throw std::runtime_error("Cannot read from process !");

    return ptr;
}

void WriteIntToProc(HANDLE hProc, DWORD_PTR baseAddr, int value)
{
    if (!WriteProcessMemory(hProc, reinterpret_cast<LPVOID>(baseAddr), &value, sizeof(value), NULL);
        throw std::runtime_error("Cannot write to process !");
}

struct HandleDeleter
{
    typedef HANDLE pointer;
    void operator()(HANDLE handle) const { CloseHandle(handle); }
};

int main()
{
    int newValue = 10;

    try
    {
        HWND hwnd = FindWindowA(NULL, "RESIDENT EVIL 2");
        if (!hwnd)
           throw std::runtime_error("Process window not found !");

        DWORD pId = 0;
        GetWindowThreadProcessId(hwnd, &pId);

        HANDLE hProc = OpenProcess(PROCESS_VM_READ | PROCESS_VM_WRITE | PROCESS_VM_OPERATION, FALSE, pId);
        if (!hProc)
            throw std::runtime_error("Cannot open process !");

        std::unique_ptr<HANDLE, HandleDeleter> hProc_deleter(hProc);

        DWORD_PTR ptr = readPointerFromProc(hProc, 0x707B6D0);
        ptr = readPointerFromProc(hProc, ptr + 0x18);
        ptr = readPointerFromProc(hProc, ptr + 0x50);
        ptr = readPointerFromProc(hProc, ptr + 0x98);
        ptr = readPointerFromProc(hProc, ptr + 0x78);
        writeIntToProc(hProc, ptr + 0x80, newValue);
    }
    catch (const std::exception &e)
    {
        std::cerr << e.what() << std::endl;
        return 0;
    }

    std::cout << "Success !" << std::endl;
    return 0;
}

score 0 · Answer 2 · answered May 25 '19 at 20:50

You need to de-reference between each offset so that you are following the pointer chain. Just adding the offsets is not enough.

Here is a function that does this for you, please keep in mind there is no error checking:

uintptr_t FindDMAAddy(HANDLE hProc, uintptr_t ptr, std::vector<unsigned int> offsets)
{
    uintptr_t addr = ptr;
    for (unsigned int i = 0; i < offsets.size(); ++i)
    {
        ReadProcessMemory(hProc, (BYTE*)addr, &addr, sizeof(addr), 0);
        addr += offsets[i];
    }
    return addr;
}

Calling the function would look like:

uintptr_t ammoAddr = FindDMAAddy(hProcess, dynamicPtrBaseAddr, { 0x374, 0x14, 0x0 });

It does not de-reference the last offset, which is ideal.

After that, call WriteProcessMemory using the return from that function as the lpBaseAddress argument.

How to write process memory with multilevel pointer with c++?

2 Answers2

You are misinterpreting what Cheat Engine is showing you.