main.cpp

#include <cstdio>
#include <vector>
#include <windows.h>

using namespace std;

class Buffer: public vector<unsigned char>
{
public:
	void push_dword(DWORD dw)
	{
		push_back(dw);
		push_back(dw >> 8);
		push_back(dw >> 16);
		push_back(dw >> 24);
	}

	void push_ptr(const void *p)
	{
		push_dword(reinterpret_cast<DWORD>(p));
	}

	int Execute()
	{
		char *func = reinterpret_cast<char *>(VirtualAlloc(
			0, size() + 1, MEM_COMMIT, PAGE_EXECUTE_READWRITE ));

		memcpy( func, data(), size() );
		func[size()] = 0xC3; // add the ret to the final of code final

		int ret = (*reinterpret_cast<int(*)()>(func))();

		VirtualFree( func, 0, MEM_RELEASE );

		return ret;
	}
};

int main()
{
	Buffer code;

	// push MESSAGE
	const char* ohi = "HI\n";
	code.push_back( 0x68 );
	code.push_ptr( ohi );

	// mov eax, printf
	code.push_back( 0xb8 );
	code.push_ptr( reinterpret_cast<void *>(&printf) );

	// call eax
	code.push_back( 0xff );
	code.push_back( 0xd0 );

	// add esp, 4
	code.push_back( 0x83 );
	code.push_back( 0xc4 );
	code.push_back( 0x04 );

	int exec = code.Execute();
	printf("SUM = %d\n", exec);

	return 0;
}