msfvenom

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

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 'fastlib'
require 'msfenv'

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

require 'rex'
require 'msf/ui'
require 'msf/base'

# Mad payload generation
#
# @example
#   venom = MsfVenom.new
#   # ARGV will be parsed destructively!
#   venom.parse_args(ARGV)
#   $stdout.puts venom.generate
class MsfVenom
  class MsfVenomError < StandardError; end
  class UsageError < MsfVenomError; end
  class NoTemplateError < MsfVenomError; end
  class IncompatibleError < MsfVenomError; end

  Status = "[*] "
  Error = "[-] "

  require 'optparse'

  def initialize(in_stream=$stdin, out_stream=$stdout, err_stream=$stderr, framework=nil)
    @in = in_stream
    @out = out_stream
    @err = err_stream
    @framework = framework
  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={})
    create_opts[:module_types] ||= [
      ::Msf::MODULE_PAYLOAD, ::Msf::MODULE_ENCODER, ::Msf::MODULE_NOP
    ]
    @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

  # Initialize the options for this run from ARGV
  # @param args [Array] Usually ARGV. Parsed destructively.
  # @return [void]
  # @raise [UsageError] When given invalid options
  def parse_args(args)
    @opts = {}
    @datastore = {}
    opt = OptionParser.new
    opt.banner = "Usage: #{$0} [options] <var=val>"
    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('-l', '--list       [module_type]', Array, 'List a module type example: 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[:nopsled] = 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('-e', '--encoder    [encoder]', String, 'The encoder to use') do |e|
      @opts[:encode] = true
      @opts[:encoder] = e
    end

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

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

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

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

    opt.on_tail('--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 UsageError, msg
    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
    end

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

  def print_status(msg)
    @err.puts(Status + msg)
  end

  def print_error(msg)
    @err.puts(Error + msg)
  end

  def get_encoders(arch, encoder)
    encoders = []

    if (encoder)
      encoders << framework.encoders.create(encoder)
    else
      framework.encoders.each_module_ranked(
          'Arch' => arch ? arch.split(',') : nil) { |name, mod|
        encoders << mod.new
      }
    end

    encoders
  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.binmode
    payload = @in.read
    payload
  end

  def generate_nops(arch, len, nop_mod=nil, nop_opts={})
    nop_opts['BadChars'] ||= ''
    nop_opts['SaveRegisters'] ||= [ 'esp', 'ebp', 'esi', 'edi' ]

    if nop_mod
      nop = framework.nops.create(nop_mod)
      raw = nop.generate_sled(len, nop_opts)
      return raw if raw
    end

    framework.nops.each_module_ranked('Arch' => arch) do |name, mod|
      begin
        nop = framework.nops.create(name)
        raw = nop.generate_sled(len, nop_opts)
        return raw if raw
      rescue
      end
    end
    nil
  end

  def dump_payloads
    init_framework(:module_types => [ ::Msf::MODULE_PAYLOAD ])
    tbl = Rex::Ui::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 ]
    }

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

  def dump_encoders(arch = nil)
    init_framework(:module_types => [ ::Msf::MODULE_ENCODER ])
    tbl = Rex::Ui::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 => [ ::Msf::MODULE_NOP ])
    tbl = Rex::Ui::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 ]
    }

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

  # @return [String] A raw shellcode blob
  # @return [nil] When commandline options conspire to produce no output
  def generate_raw_payload

    if @opts[:payload] == 'stdin'
      payload_raw = payload_stdin
      if @opts[:encode] and (@opts[:arch].nil? or @opts[:platform].nil?)
        print_error("Cannot encode stdin payload without specifying the proper architecture and platform")
        @opts[:encode] = false
      end
      # defaults for stdin payloads users should define them
      unless @opts[:arch]
        print_error("Defaulting to x86 architecture for stdin payload, use -a to change")
        @opts[:arch] = "x86"
      end
      unless @opts[:platform]
        print_error("Defaulting to Windows platform for stdin payload, use --platform to change")
        @opts[:platform] = ::Msf::Module::PlatformList.transform("Windows")
      end
    else
      payload = framework.payloads.create(@opts[:payload])
      if payload.nil?
        raise UsageError, "Invalid payload: #{@opts[:payload]}"
      end
      @opts[:arch]     ||= payload.arch[0]
      # If it's not stdin, we'll already have a PlatformList
      @opts[:platform] ||= payload.platform
      payload.datastore.merge! @datastore

      if @opts[:list_options]
        print_status("Options for #{payload.fullname}\n\n" +
           ::Msf::Serializer::ReadableText.dump_module(payload,'    '))
        return
      end
      payload_raw = payload.generate_simple(
        'Format'   => 'raw',
        'Options'  => @datastore,
        'Encoder'  => nil)
    end

    payload_raw
  end


  # Main dispatch method to do the right thing with the given options.
  def generate
    if @opts[:list]
      @opts[:list].each do |mod|
        case mod.downcase
        when "payloads"
          @err.puts dump_payloads
        when "encoders"
          @err.puts dump_encoders(@opts[:arch])
        when "nops"
          @err.puts dump_nops
        when "all"
          # Init here so #dump_payloads doesn't create a framework with
          # only payloads, etc.
          init_framework
          @err.puts dump_payloads
          @err.puts dump_encoders
          @err.puts dump_nops
        else
          raise UsageError, "Invalid module type"
        end
      end
      return
    end

    # Normalize the options
    @opts[:platform] = ::Msf::Module::PlatformList.transform(@opts[:platform]) if @opts[:platform]
    @opts[:badchars] = Rex::Text.hex_to_raw(@opts[:badchars])                if @opts[:badchars]
    @opts[:format]   ||= 'ruby'
    @opts[:encoder]  ||= nil
    @opts[:encode]   ||= !(@opts[:badchars].nil? or @opts[:badchars].empty?)


    payload_raw = generate_raw_payload
    return unless payload_raw

    if @opts[:template]
      unless File.exist?(@opts[:template])
        raise NoTemplateError, "Template file (#{@opts[:template]}) does not exist"
      end
      path = File.dirname(@opts[:template])
      altexe = File.basename(@opts[:template])
    end
    exeopts = { :inject => @opts[:inject], :template_path => path, :template => altexe }

    # If we were given addshellcode for a win32 payload,
    # create a double-payload; one running in one thread, one running in the other
    if @opts[:addshellcode] and @opts[:platform].platforms.include?(::Msf::Module::Platform::Windows) and @opts[:arch] == 'x86'
      payload_raw = ::Msf::Util::EXE.win32_rwx_exec_thread(payload_raw,0,'end')
      file = ::File.new(@opts[:addshellcode])
      file.binmode
      payload_raw << file.read
      file.close
    end

    if @opts[:encode]
      done = false
      encoders = get_encoders(@opts[:arch], @opts[:encoder])
      encoders.each do |enc|
        next if not enc
        begin
          break if done
          enc.datastore.import_options_from_hash(@datastore)
          skip = false
          raw = nil

          @opts[:iterations] ||= 1

          1.upto(@opts[:iterations].to_i) do |iteration|
            begin
              raw = enc.encode(payload_raw.dup, @opts[:badchars], nil, @opts[:platform])
            rescue ::Msf::EncodingError
              print_error("#{enc.refname} failed: #{$!.class} : #{$!}")
              skip = true
              break
            end
            if @opts[:space] and @opts[:space] > 0 and raw.length > @opts[:space]
              print_error("#{enc.refname} created buffer that is too big (#{raw.length})\n\n")
              skip = true
              break
            end

            print_status("#{enc.refname} succeeded with size #{raw.length} (iteration=#{iteration})\n")
            payload_raw = raw.dup
            if iteration == @opts[:iterations]
              done = true
              break
            end
          end
          next if skip

        rescue ::Errno::ENOENT, ::Errno::EINVAL
          print_error("#{enc.refname} failed: #{$!}")
          break

        rescue => e
          print_error("#{enc.refname} failed: #{e.class} #{e}")
          e.backtrace.each { |el|
            @err.puts(el.to_s)
          }
        end
      end
    end

    if @opts[:nopsled]
      nopts = { 'BadChars' => @opts[:badchars] }
      nops = generate_nops([@opts[:arch]], @opts[:nopsled], nil, nopts)
      payload_raw = nops + payload_raw
    end

    @out.binmode

    case @opts[:format].downcase
    # Special-case this to check endianness
    when "js_be"

      if Rex::Arch.endian(payload.arch) != ENDIAN_BIG
          raise IncompatibleError, "Big endian format selected for a non big endian payload"
      end
      @out.write ::Msf::Simple::Buffer.transform(payload_raw, @opts[:format])

    # Special-case this so we can build a war directly from the payload if
    # possible
    when "war"
      exe = ::Msf::Util::EXE.to_executable_fmt(framework, @opts[:arch], @opts[:platform], payload_raw, @opts[:format], exeopts)
      if (!exe && payload.respond_to?(:generate_war))
        exe = payload.generate_war.pack
      end
      @out.write exe

    # Same as war, special-case this so we can build a jar directly from the
    # payload if possible
    when "java"
      exe = ::Msf::Util::EXE.to_executable_fmt(framework, @opts[:arch], @opts[:platform], payload_raw, @opts[:format], exeopts)
      if (!exe && payload.respond_to?(:generate_jar))
        exe = payload.generate_jar.pack
      end
      if exe
        @out.write exe
      else
        print_error("Could not generate payload format")
      end

    when *::Msf::Simple::Buffer.transform_formats
      buf = ::Msf::Simple::Buffer.transform(payload_raw, @opts[:format])
      @out.write buf

    when *::Msf::Util::EXE.to_executable_fmt_formats
      exe = ::Msf::Util::EXE.to_executable_fmt(framework, @opts[:arch], @opts[:platform], payload_raw, @opts[:format], exeopts)
      if exe.nil?
        raise IncompatibleError, "This format does not support that platform/architecture"
      end
      @out.write exe

    else
      raise IncompatibleError, "Unsupported format"
      return
    end
  end
end


if __FILE__ == $0
  begin
    venom = MsfVenom.new
    venom.parse_args(ARGV)
    venom.generate
  rescue MsfVenom::MsfVenomError, Msf::OptionValidateError => e
    $stderr.puts e.message
    exit(-1)
  end
end