Changing a value using a pointer.

[astropirit]

Hi all
i have been having this annoying problem. I can change th value of an memory address. the problem is tha the memory address changes every time the application restarts. Now i figured i would need to use a pointer. So i found a pointer that points to this address, but it has an offset.

lets say the address is: "04A96990"
and the offset is: "A0"
and lets say this points to...:"07b96964" // this is the address i want to modify.

How might one change this code to make it take advantage of the pointer and find the address and be able to modify it.

#include <windows.h>
#include <tlhelp32.h>
#include <conio.h>
#include <stdlib.h>
#include <stdio.h>

bool ChangeMemVal(const char * ProcessName, LPVOID MemAddress, int NewVal, int size);

int main()
{
printf("=== Pinball Trainer Example. Made by <your name here> ===\n\n");
if(ChangeMemVal("PINBALL.EXE", (void*) 0xA90C62, 100000000, 4))
printf("The score has been edited successfully.\n");
else
printf("An error occured while attempting edit the score.\n");
system("PAUSE");
return 0;
}


/* This function modifys a memory address according to its arguments.
Arguments :
ProcessName - the process we want to modify
MemAddress - the memory address we want to modify
NewVal - the value we want to change the memory address to
size - the size of the memory address
Returns :
the success of the edit.
*/


bool ChangeMemVal(const char * ProcessName, LPVOID MemAddress, int NewVal, int size)
{
HANDLE hProcessSnap;
HANDLE hProcess = NULL;
PROCESSENTRY32 pe32;
hProcessSnap = CreateToolhelp32Snapshot( TH32CS_SNAPPROCESS, 0 );
pe32.dwSize = sizeof( PROCESSENTRY32 );
Process32First(hProcessSnap, &pe32);
do
{
if(!strcmp(pe32.szExeFile, ProcessName))
{
hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pe32.th32ProcessID);
break;
}
}
while(Process32Next(hProcessSnap, &pe32));
CloseHandle( hProcessSnap );
if(hProcess != NULL)
{
WriteProcessMemory(hProcess, MemAddress, &NewVal, size, NULL); // write the value
CloseHandle(hProcess);
return true;
}
return false;
}

Help would be greately apreciated.


Astro

[Danny]

You can't really write to a random address without risking a crash. Most operating systems these days use virtual memory so you can't predict what the physical address of a certain memory chunk will be or write directly to it.

[astropirit]

the address here on the forums is arbitary becouse i do not have my values with me, they are on my pc and i am at school. and i found out the value of the address using a software called cheatengine.

[Danny]

Are these addresses random? How does the cheatengine software calculate those addresses?
Anyway, the more commonplace of writing to an address is by declaring a pointer and using new or malloc.