Land rapid7#5067, @wchen-r7's standalone jsobfu tool

Author: jvazquez-r7

spec/tools/jsobfu_spec.rb

@@ -0,0 +1,79 @@
+require 'spec_helper'
+
+load Metasploit::Framework.root.join('tools/jsobfu.rb').to_path
+
+require 'stringio'
+
+describe Jsobfu do
+
+  let(:fname) {
+    'test.js'
+  }
+
+  let(:js) {
+    %Q|alert("test");|
+  }
+
+  describe Jsobfu::Driver do
+
+    subject do
+      Jsobfu::Driver.new
+    end
+
+    describe '#run' do
+      let(:default_opts) {
+        { :input => fname, :iteration => 1 }
+      }
+
+      before(:each) do
+        allow(Jsobfu::OptsConsole).to receive(:parse).with(any_args).and_return(default_opts)
+        allow(File).to receive(:open).with(fname, 'rb').and_yield(StringIO.new(js))
+        @out = $stdout
+        $stdout = StringIO.new
+        $stdout.string = ''
+      end
+
+      after(:each) do
+        $stdout = @out
+      end
+
+      context 'when a javascript file is given' do
+        it 'returns an String' do
+          subject.run
+          expect($stdout.string).to be_a(String)
+        end
+
+        it 'returns a non empty String' do
+          subject.run
+          expect($stdout.string).not_to be_empty
+        end
+
+        it 'returns an String different than the original' do
+          subject.run
+          expect($stdout.string).not_to eq(js)
+        end
+      end
+    end
+  end
+
+
+  describe Jsobfu::OptsConsole do
+    subject do
+      Jsobfu::OptsConsole
+    end
+
+    context 'when no options are given' do
+      it 'raises OptionParser::MissingArgument' do
+        expect{subject.parse([])}.to raise_error(OptionParser::MissingArgument)
+      end
+    end
+
+    context 'when -t isn\'t a number' do
+      it 'raises OptionParser::MissingArgument' do
+        args = "-i #{fname} -t NaN".split
+        expect{subject.parse(args)}.to raise_error(OptionParser::InvalidOption)
+      end
+    end
+  end
+
+end

tools/jsobfu.rb

@@ -0,0 +1,106 @@
+#!/usr/bin/env ruby
+
+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'
+require 'rex'
+require 'msf/core'
+require 'msf/base'
+require 'optparse'
+
+module Jsobfu
+  class OptsConsole
+    def self.parse(args)
+      options = {}
+      parser = OptionParser.new do |opt|
+        opt.banner = "Usage: #{__FILE__} [options]"
+        opt.separator ''
+        opt.separator 'Specific options:'
+
+        opt.on('-t', '--iteration <Fixnum>', "Number of times to obfuscate the JavaScript") do |v|
+          options[:iteration] = v
+        end
+
+        opt.on('-i', '--input <String>', "The JavaScript file you want to obfuscate (default=1)") do |v|
+          options[:input] = v
+        end
+
+        opt.on('-o', '--output <String>', "Save the obfuscated file as") do |v|
+          options[:output] = v
+        end
+
+        opt.on_tail('-h', '--help', 'Show this message') do
+          $stdout.puts opt
+          exit
+        end
+      end
+
+      parser.parse!(args)
+
+      if options.empty?
+        raise OptionParser::MissingArgument, 'No options set, try -h for usage'
+      elsif options[:iteration] && options[:iteration] !~ /^\d+$/
+        raise OptionParser::InvalidOption, "#{options[:format]} is not a number"
+      elsif !::File.exists?(options[:input].to_s)
+        raise OptionParser::InvalidOption, "Cannot find: #{options[:input]}"
+      end
+
+      options[:iteration] = 1 unless options[:iteration]
+
+      options
+    end
+  end
+
+  class Driver
+    def initialize
+      begin
+        @opts = OptsConsole.parse(ARGV)
+      rescue OptionParser::ParseError => e
+        $stderr.puts "[x] #{e.message}"
+        exit
+      end
+    end
+
+    def run
+      original_js = read_js(@opts[:input])
+      js = ::Rex::Exploitation::JSObfu.new(original_js)
+      js.obfuscate(:iterations=>@opts[:iteration].to_i)
+      js = js.to_s
+
+      output_stream = $stdout
+      output_stream.binmode
+      output_stream.write js
+      $stderr.puts
+
+      if @opts[:output]
+        save_as(js, @opts[:output])
+      end
+    end
+
+    private
+
+    def read_js(path)
+      js = ::File.open(path, 'rb') { |f| js = f.read }
+      js
+    end
+
+    def save_as(js, outfile)
+      File.open(outfile, 'wb') do |f|
+        f.write(js)
+      end
+
+      $stderr.puts
+      $stderr.puts "File saved as: #{outfile}"
+    end
+
+  end
+end
+
+
+if __FILE__ == $PROGRAM_NAME
+  driver = Jsobfu::Driver.new
+  driver.run
+end