msfvenom

#!/usr/bin/env ruby
# -*- coding: binary -*-

class MsfVenomError < StandardError; end
class HelpError < StandardError; end
class UsageError < MsfVenomError; end

require 'optparse'
require 'timeout'

def require_deps
  msfbase = __FILE__
  while File.symlink?(msfbase)
    msfbase = File.expand_path(File.readlink(msfbase), File.dirname(msfbase))
  end

  $:.unshift(File.expand_path(File.join(File.dirname(msfbase), 'lib')))
  require 'msfenv'

  $:.unshift(ENV['MSF_LOCAL_LIB']) if ENV['MSF_LOCAL_LIB']

  require 'rex'
  require 'msf/ui'
  require 'msf/base'
  require 'msf/core/payload_generator'

  @framework_loaded = true
end

# Creates a new framework object.
#
# @note Ignores any previously cached value.
# @param (see ::Msf::Simple::Framework.create)
# @return [Msf::Framework]
def init_framework(create_opts={})
  require_deps unless @framework_loaded

  create_opts[:module_types] ||= [
    ::Msf::MODULE_PAYLOAD, ::Msf::MODULE_ENCODER, ::Msf::MODULE_NOP
  ]

  create_opts[:module_types].map! do |type|
    type = Msf.const_get("MODULE_#{type.upcase}")
  end

  @framework = ::Msf::Simple::Framework.create(create_opts.merge('DisableDatabase' => true))
end

# Cached framework object
#
# @return [Msf::Framework]
def framework
  return @framework if @framework

  init_framework

  @framework
end

def parse_args(args)
  opts = {}
  datastore = {}
  opt = OptionParser.new
  banner = "MsfVenom - a Metasploit standalone payload generator.\n"
  banner << "Also a replacement for msfpayload and msfencode.\n"
  banner << "Usage: #{$0} [options] <var=val>"
  opt.banner = banner
  opt.separator('')
  opt.separator('Options:')

  opt.on('-p', '--payload       <payload>', String,
         'Payload to use. Specify a \'-\' or stdin to use custom payloads') do |p|
    if p == '-'
      opts[:payload] = 'stdin'
    else
      opts[:payload] = p
    end
  end

  opt.on('--payload-options', "List the payload's standard options") do
    opts[:list_options] = true
  end

  opt.on('-l', '--list          [type]', Array, 'List a module type. Options are: payloads, encoders, nops, all') do |l|
    if l.nil? or l.empty?
      l = ["all"]
    end
    opts[:list] = l
  end

  opt.on('-n', '--nopsled       <length>', Integer, 'Prepend a nopsled of [length] size on to the payload') do |n|
    opts[:nops] = n.to_i
  end

  opt.on('-f', '--format        <format>', String, "Output format (use --help-formats for a list)") do |f|
    opts[:format] = f
  end

  opt.on('--help-formats', String, "List available formats") do
    init_framework(:module_types => [])
    msg = "Executable formats\n" +
      "\t" + ::Msf::Util::EXE.to_executable_fmt_formats.join(", ") + "\n" +
      "Transform formats\n" +
      "\t" + ::Msf::Simple::Buffer.transform_formats.join(", ")
    raise HelpError, msg
  end

  opt.on('-e', '--encoder       <encoder>', String, 'The encoder to use') do |e|
    opts[:encoder] = e
  end

  opt.on('-a', '--arch          <arch>', String, 'The architecture to use') do |a|
    opts[:arch] = a
  end

  opt.on('--platform      <platform>', String, 'The platform of the payload') do |l|
    opts[:platform] = l
  end

  opt.on('--help-platforms', String, 'List available platforms') do
    init_framework(:module_types => [])
    supported_platforms = []
    Msf::Module::Platform.subclasses.each {|c| supported_platforms << "#{c.realname.downcase}"}
    msg = "Platforms\n" +
      "\t" + supported_platforms.sort * ", "
    raise HelpError, msg
  end

  opt.on('-s', '--space         <length>', Integer, 'The maximum size of the resulting payload') do |s|
    opts[:space] = s
  end

  opt.on('--encoder-space <length>', Integer, 'The maximum size of the encoded payload (defaults to the -s value)') do |s|
    opts[:encoder_space] = s
  end

  opt.on('-b', '--bad-chars     <list>', String, 'The list of characters to avoid example: \'\x00\xff\'') do |b|
    init_framework()
    opts[:badchars] = Rex::Text.hex_to_raw(b)
  end

  opt.on('-i', '--iterations    <count>', Integer, 'The number of times to encode the payload') do |i|
    opts[:iterations] = i
  end

  opt.on('-c', '--add-code      <path>', String, 'Specify an additional win32 shellcode file to include') do |x|
    opts[:add_code] = x
  end

  opt.on('-x', '--template      <path>', String, 'Specify a custom executable file to use as a template') do |x|
    opts[:template] = x
  end

  opt.on('-k', '--keep', 'Preserve the template behavior and inject the payload as a new thread') do
    opts[:keep] = true
  end

  opt.on('-o', '--out           <path>', 'Save the payload') do |x|
    opts[:out] = x
  end

  opt.on('-v', '--var-name      <name>', String, 'Specify a custom variable name to use for certain output formats') do |x|
    opts[:var_name] = x
  end

  opt.on('--smallest', 'Generate the smallest possible payload') do
    opts[:smallest] = true
  end

  opt.on_tail('-h', '--help', 'Show this message') do
    raise HelpError, "#{opt}"
  end

  begin
    opt.parse!(args)
  rescue OptionParser::InvalidOption => e
    raise UsageError, "Invalid option\n#{opt}"
  rescue OptionParser::MissingArgument => e
    raise UsageError, "Missing required argument for option\n#{opt}"
  end

  if opts.empty?
    raise UsageError, "No options\n#{opt}"
  end

  if args
    args.each do |x|
      k,v = x.split('=', 2)
      datastore[k.upcase] = v.to_s
    end
    if opts[:payload].to_s =~ /[\_\/]reverse/ and datastore['LHOST'].nil?
      init_framework()
      datastore['LHOST'] = Rex::Socket.source_address
    end
  end

  if opts[:payload].nil? # if no payload option is selected assume we are reading it from stdin
    opts[:payload] = "stdin"
  end

  if opts[:payload] == 'stdin' and not opts[:list]
    $stderr.puts "Attempting to read payload from STDIN..."
    begin
      ::Timeout.timeout(30) do
        opts[:stdin] = payload_stdin
      end
    rescue Timeout::Error
      opts[:stdin] = ''
    end
  end

  opts[:datastore] = datastore

  opts
end

# Read a raw payload from stdin (or whatever IO object we're currently
# using as stdin, see {#initialize})
#
# @return [String]
def payload_stdin
  @in = $stdin
  @in.binmode
  payload = @in.read
  payload
end

def dump_payloads
  init_framework(:module_types => [ :payload ])
  tbl = Rex::Text::Table.new(
    'Indent'  => 4,
    'Header'  => "Framework Payloads (#{framework.stats.num_payloads} total)",
    'Columns' =>
    [
      "Name",
      "Description"
    ])

  framework.payloads.each_module { |name, mod|
    tbl << [ name, mod.new.description.split.join(' ') ]
  }

  "\n" + tbl.to_s + "\n"
end

def dump_encoders(arch = nil)
  init_framework(:module_types => [ :encoder ])
  tbl = Rex::Text::Table.new(
    'Indent'  => 4,
    'Header'  => "Framework Encoders" + ((arch) ? " (architectures: #{arch})" : ""),
    'Columns' =>
    [
      "Name",
      "Rank",
      "Description"
    ])
  cnt = 0

  framework.encoders.each_module(
    'Arch' => arch ? arch.split(',') : nil) { |name, mod|
      tbl << [ name, mod.rank_to_s, mod.new.name ]

      cnt += 1
    }

    (cnt > 0) ? "\n" + tbl.to_s + "\n" : "\nNo compatible encoders found.\n\n"
end

def dump_nops
  init_framework(:module_types => [ :nop ])
  tbl = Rex::Text::Table.new(
    'Indent'  => 4,
    'Header'  => "Framework NOPs (#{framework.stats.num_nops} total)",
    'Columns' =>
    [
      "Name",
      "Description"
    ])

  framework.nops.each_module { |name, mod|
    tbl << [ name, mod.new.description.split.join(' ') ]
  }

  "\n" + tbl.to_s + "\n"
end

begin
  generator_opts = parse_args(ARGV)
rescue HelpError => e
  $stderr.puts e.message
  exit(1)
rescue MsfVenomError => e
  $stderr.puts "Error: #{e.message}"
  exit(1)
end

if generator_opts[:list]
  generator_opts[:list].each do |mod|
    case mod.downcase
    when "payloads", "payload", "p"
      $stdout.puts dump_payloads
    when "encoders", "encoder", "e"
      $stdout.puts dump_encoders(generator_opts[:arch])
    when "nops", "nop", "n"
      $stdout.puts dump_nops
    when "all"
      # Init here so #dump_payloads doesn't create a framework with
      # only payloads, etc.
      init_framework
      $stdout.puts dump_payloads
      $stdout.puts dump_encoders
      $stdout.puts dump_nops
    else
      $stderr.puts "Invalid module type. These are valid: payloads, encoders, nops, all"
    end
  end
  exit(0)
end

if generator_opts[:list_options]
  payload_mod = framework.payloads.create(generator_opts[:payload])

  if payload_mod.nil?
    $stderr.puts "Invalid payload: #{generator_opts[:payload]}"
    exit
  end

  $stderr.puts "Options for #{payload_mod.fullname}:\n\n"
  $stdout.puts ::Msf::Serializer::ReadableText.dump_module(payload_mod, '    ')

  $stderr.puts "Advanced options for #{payload_mod.fullname}:\n\n"
  $stdout.puts ::Msf::Serializer::ReadableText.dump_advanced_options(payload_mod, '    ')

  $stderr.puts "Evasion options for #{payload_mod.fullname}:\n\n"
  $stdout.puts ::Msf::Serializer::ReadableText.dump_evasion_options(payload_mod, '    ')
  exit(0)
end

generator_opts[:framework] = framework
generator_opts[:cli] = true

begin
  venom_generator = Msf::PayloadGenerator.new(generator_opts)
  payload = venom_generator.generate_payload
rescue ::Exception => e
  elog("#{e.class} : #{e.message}\n#{e.backtrace * "\n"}")
  $stderr.puts "Error: #{e.message}"
end

# No payload generated, no point to go on
exit(2) unless payload

if generator_opts[:out]
  begin
    ::File.open(generator_opts[:out], 'wb') do |f|
      f.write(payload)
    end
    $stderr.puts "Saved as: #{generator_opts[:out]}"
  rescue ::Exception => e
    # If I can't save it, then I can't save it. I don't think it matters what error.
    elog("#{e.class} : #{e.message}\n#{e.backtrace * "\n"}")
    $stderr.puts "Error: #{e.message}"
  end
else
  output_stream = $stdout
  output_stream.binmode
  output_stream.write payload
  # trailing newline for pretty output
  $stderr.puts unless payload =~ /\n$/
end