How to modify program memory using WriteProcessMemory() in C++?

Question

C++ / C#

There is a simple test application

#include <iostream>
#include <Windows.h>
#include <conio.h>

using namespace std;

int main(int argc, char* argv[])
{
  system("title Test Program");
  int value = 100;
  int* ptr = &value;
  cout << "value = " << value << "\naddr = " << ptr << "\n\n";
  for (;;)
  {
    _getch();
    cout << "value = " << ++value << "\naddr = " << ptr << "\n\n";
  }
  return 0;
}

At the moment there is this code

#include <iostream>
#include <Windows.h>
#include <WtsApi32.h>
#include <tlhelp32.h>
#include <clocale>

#pragma comment(lib, "wtsapi32.lib")

using namespace std;

int AppIsRun(const LPCWSTR ProcessName, DWORD *ProcessId)
{
  WTS_PROCESS_INFOW * pProcessInfo;
  DWORD               NumProcesses;
  if (NULL == WTSEnumerateProcessesW(WTS_CURRENT_SERVER_HANDLE,
    0, // Reserved.
    1, // Version,
    &pProcessInfo,
    &NumProcesses))
  {
    return EXIT_FAILURE;
  }
  bool ProcessFound = false;
  for (DWORD i = 0; i < NumProcesses; ++i)
    if (!lstrcmpW(pProcessInfo[i].pProcessName, ProcessName))
    {
      ProcessFound = true;
      *ProcessId = pProcessInfo[i].ProcessId;
      break;
    }
  WTSFreeMemory(pProcessInfo);
  return ProcessFound;
}

int main(int argc, char* argv[])
{
  setlocale(LC_ALL, "Russian");
  wchar_t Title[256] = L"Test Program";
  wchar_t ExeName[256] = L"test.exe";
  HWND hWnd = NULL;
  HANDLE processHandle = NULL;
  DWORD ProccessId = NULL;
  if (AppIsRun(ExeName, &ProccessId) && FindWindow(NULL, Title))
  {
    cout << "SUCCESS\n";
    hWnd = FindWindow(NULL, Title);
    processHandle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, ProccessId);
  }
  else
  {
    cout << "ERROR\n";
    if (!AppIsRun(ExeName, &ProccessId))
      cout << "Приложение не запущенно\n";
    if (!FindWindow(NULL, Title))
      cout << "Не верно указан заголовок окна\n";
  }
  return 0;
}

How to change the value of the variable itself using the address of the variable obtained from the first program?

Answer 1

How to change the value of the variable itself using the address of the variable obtained from the first program?

DWORD ProcessId = ...;
LPVOID Address = ...;
int value = 500;

processHandle = OpenProcess(PROCESS_VM_WRITE, FALSE, ProccessId);
if (WriteProcessMemory(processHandle, Address, &newValue, sizeof(newValue), NULL))
    printf("Success\n");
else
    printf("Error\n");

In the first program, you need to make volatile int value = 100;sure that it retrieves the value of the variable from memory at each iteration of the loop.