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Stealing Program's Memory

, 2 Dec 2003
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An advanced article on allocating and using memory in another process using the Win32 API.

Introduction

I was recently trying to steal strings from another program's listview control. You need to pass a pointer so it knows where to put the string. Normally this wouldn't be a problem, but because Windows uses virtual memory pointers are not valid across programs.

Virtual memory is how Windows deals out memory to all it's programs. It makes programs think they have 2 Gb of memory to use. It also protects programs from using each other's memory so if one program crashes it doesn't take down the whole system with it.

So after coding a fair bit, I realized my pointers were all invalid and it wouldn't work. A few hours of digging through MSDN brought me to the functions VirtualAllocEx(), VirtualFreeEx(), WriteProcessMemory() and ReadProcessMemory(). Armed with this new information, I set out to modify my code. Here is what I had so far:

#define WIN32_LEAN_AND_MEAN
#include <stdio.h>
#include <windows.h>
#include <commctrl.h>

int main(void) {
 /* Run through the windows until we find our listview. */
 HWND hwnd=FindWindow(NULL, "Stealing Program's Memory: ListView");
 HWND listview=FindWindowEx(hwnd, NULL, "SysListView32", NULL);

 int count=(int)SendMessage(listview, LVM_GETITEMCOUNT, 0, 0);
 int i;

 char item[512], subitem[512];

 /* Shove all items of listview into item and subitem
    and print out one by one. */

 LVITEM lvi;
 lvi.cchTextMax=512;

 for(i=0; i<count; i++) {
  lvi.iSubItem=0;
  lvi.pszText=item;
  SendMessage(listview, LVM_GETITEMTEXT, (WPARAM)i, (LPARAM)&lvi);

  lvi.iSubItem=1;
  lvi.pszText=subitem;
  SendMessage(listview, LVM_GETITEMTEXT, (WPARAM)i, (LPARAM)&lvi);

  printf("%s - %s\n", item, subitem);
 }
 return 0;
}

As I said before, this won't work. The pointers to lvi, item, and subitem all get screwed when they go across process. The solution? Use WriteProcessMemory() and ReadProcessMemory() to use the other programs memory, perform LVM_GETITEMTEXT on it, and read it back. Hackish yes, but then again reading items from another program's listview control is one giant hack.

First, we get the process of the listview like this:

unsigned long pid;
HANDLE process;
GetWindowThreadProcessId(listview, &pid);
process=OpenProcess(PROCESS_VM_OPERATION|PROCESS_VM_READ|
                    PROCESS_VM_WRITE|PROCESS_QUERY_INFORMATION, FALSE, pid);

Next We create three pointers, LVITEM *_lvi, char *_item, and char *_subitem and allocate them in the other program's virtual memory space with VirtualAllocEx():

LVITEM *_lvi=(LVITEM*)VirtualAllocEx(process, NULL, sizeof(LVITEM),
                                     MEM_COMMIT, PAGE_READWRITE);
char *_item=(char*)VirtualAllocEx(process, NULL, 512, MEM_COMMIT,
                                  PAGE_READWRITE);
char *_subitem=(char*)VirtualAllocEx(process, NULL, 512, MEM_COMMIT,
                                     PAGE_READWRITE);

Now we point lvi.pszText to _item, and copy it's memory to _lvi using WriteMemoryProcess():

lvi.pszText=_item;
WriteProcessMemory(process, _lvi, &lvi, sizeof(LVITEM), NULL);

Now that we have an LVITEM pointer that is valid in the other programs virtual memory, we can shoot off LVM_GETITEMTEXT to listview and copy _item's text into item so we can read it in our program:

SendMessage(hwnd, LVM_GETITEMTEXT, (WPARAM)i, (LPARAM)_lvi);
ReadProcessMemory(process, _item, item, max, NULL);

Repeat that for subitem, then free the memory we used in the other program's memory:

VirtualFreeEx(process, _lvi, 0, MEM_RELEASE);
VirtualFreeEx(process, _item, 0, MEM_RELEASE);
VirtualFreeEx(process, _subitem, 0, MEM_RELEASE);

Yay, all done. In case that didn't make too much sense to you, here is our new code, all fixed up:

#define WIN32_LEAN_AND_MEAN
#include <stdio.h>
#include <windows.h>
#include <commctrl.h>

int main(void) {
 HWND hwnd=FindWindow(NULL, "Stealing Program's Memory: ListView");
 HWND listview=FindWindowEx(hwnd, NULL, "SysListView32", NULL);

 int count=(int)SendMessage(listview, LVM_GETITEMCOUNT, 0, 0);
 int i;

 LVITEM lvi, *_lvi;
 char item[512], subitem[512];
 char *_item, *_subitem;
 unsigned long pid;
 HANDLE process;

 GetWindowThreadProcessId(listview, &pid);
 process=OpenProcess(PROCESS_VM_OPERATION|PROCESS_VM_READ|
                     PROCESS_VM_WRITE|PROCESS_QUERY_INFORMATION, FALSE, pid);

 _lvi=(LVITEM*)VirtualAllocEx(process, NULL, sizeof(LVITEM),
                              MEM_COMMIT, PAGE_READWRITE);
 _item=(char*)VirtualAllocEx(process, NULL, 512, MEM_COMMIT,
                             PAGE_READWRITE);
 _subitem=(char*)VirtualAllocEx(process, NULL, 512, MEM_COMMIT,
                                PAGE_READWRITE);

 lvi.cchTextMax=512;

 for(i=0; i<count; i++) {
  lvi.iSubItem=0;
  lvi.pszText=_item;
  WriteProcessMemory(process, _lvi, &lvi, sizeof(LVITEM), NULL);
  SendMessage(listview, LVM_GETITEMTEXT, (WPARAM)i, (LPARAM)_lvi);

  lvi.iSubItem=1;
  lvi.pszText=_subitem;
  WriteProcessMemory(process, _lvi, &lvi, sizeof(LVITEM), NULL);
  SendMessage(listview, LVM_GETITEMTEXT, (WPARAM)i, (LPARAM)_lvi);

  ReadProcessMemory(process, _item, item, 512, NULL);
  ReadProcessMemory(process, _subitem, subitem, 512, NULL);

  printf("%s - %s\n", item, subitem);
 }

 VirtualFreeEx(process, _lvi, 0, MEM_RELEASE);
 VirtualFreeEx(process, _item, 0, MEM_RELEASE);
 VirtualFreeEx(process, _subitem, 0, MEM_RELEASE);

 return 0;
}

If you're looking to use a program's memory for another reason, or have had a similar problem to mine, adapting this should be fairly easy.

This article was originally written for int64.org

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About the Author

Cory Nelson
Web Developer
United States United States
No Biography provided

Comments and Discussions

 
QuestionI tried to read Header control? using HDITEM . PinmemberSathishMask29-Sep-14 6:36 
Questionthanks PinmemberImbue16-Mar-13 11:37 
Thanks a million. This is exactly what I needed!
QuestionLVM_GETITEMRECT PinmemberZockerman™22-May-12 8:08 
GeneralMy vote of 5 PinmemberSynetech2-Mar-12 15:08 
QuestionBut GetWindowText() works. :-? PinmemberSynetech2-Mar-12 12:51 
QuestionRemove Item PinmemberMustafa Chelik11-Dec-11 3:38 
QuestionC# Code Version PinmemberNilesh bhope8-Aug-11 3:57 
AnswerRe: C# Code Version Pinmembertaylorza21-Aug-11 2:23 
GeneralRe: C# Code Version PinmemberNilesh bhope29-Aug-11 3:01 
GeneralRe: C# Code Version PinmemberNilesh bhope29-Aug-11 6:04 
GeneralThank you very much - it is exactly what I needed. Pinmember__stas__15-Nov-10 23:37 
GeneralExcellent article though requires a little addition PinmemberMember 373653224-Jul-09 5:22 
GeneralRe: Excellent article though requires a little addition PinmemberMember 71363228-Apr-10 6:49 
Generala problem about List Control Pinmemberdyj682213-Jul-09 19:01 
GeneralDoes the job Pinmembersoftware_chotmail13-Jun-09 14:42 
GeneralAPI is returning blank for LVM_GETITEMTEXT message in 64 bit system (Win2003). Pinmemberrushijoshi6-Apr-09 1:50 
QuestionRe: API is returning blank for LVM_GETITEMTEXT message in 64 bit system (Win2003). Pinmemberanadipsia12-Aug-09 4:21 
AnswerRe: API is returning blank for LVM_GETITEMTEXT message in 64 bit system (Win2003). PinmemberChewsHumans11-Mar-10 15:36 
Questioncode returns blanks when tried on listview which seems to be with window style LVS_OWNERDRAWFIXED PinmemberMember 436362620-Jan-09 1:05 
AnswerRe: code returns blanks when tried on listview which seems to be with window style LVS_OWNERDRAWFIXED PinmemberMember 17143758-Sep-10 19:00 
GeneralRidiculous... Pinmemberkilt6-Nov-08 4:11 
GeneralRe: Ridiculous... Pinmemberdamnedyankee7-Nov-08 1:35 
GeneralRe: Ridiculous... Pinmemberzameb10-Aug-10 8:01 
GeneralRe: Ridiculous... PinmemberSynetech2-Mar-12 12:38 
QuestionHow to steal TStringGrid's Memory? Pinmemberwhite88815-Aug-08 18:31 

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