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

require 'msf/core'

class Metasploit3 < Msf::Auxiliary

	include Msf::Exploit::Remote::HttpClient
	include Msf::Auxiliary::Scanner

	def initialize(info={})
		super(update_info(info,
			'Name'        => 'Ruby on Rails JSON Processor YAML Deserialization Scanner',
			'Description' => %q{
				This module attempts to identify Ruby on Rails instances vulnerable to
				an arbitrary object instantiation flaw in the JSON request processor.
			},
			'Author'      =>
				[
						'jjarmoc',	# scanner module
						'hdm'		# CVE-2013-0156 scanner, basis of this technique.
				],
			'License'     => MSF_LICENSE,
			'References'  =>
				[
					['CVE', '2013-0333']
				]
		))

		register_options([
			OptString.new('TARGETURI', [true, "The URI to test", "/"]),
			OptEnum.new('HTTP_METHOD', [true, 'HTTP Method', 'POST', ['GET', 'POST', 'PUT']]),
		], self.class)
	end

	def send_probe(pdata)
		res = send_request_cgi({
			'uri'    => normalize_uri(datastore['TARGETURI']),
			'method' => datastore['HTTP_METHOD'],
			'ctype'  => 'application/json',
			'data'   => pdata
		})
	end

	def run_host(ip)

		# Straight JSON as a baseline
		res1 = send_probe(
			"{ \"#{Rex::Text.rand_text_alpha(rand(8)+1)}\" : \"#{Rex::Text.rand_text_alpha(rand(8)+1)}\" }"
			)

		unless res1
			vprint_status("#{rhost}:#{rport} No reply to the initial JSON request")
			return
		end

		if res1.code.to_s =~ /^[5]/
			vprint_error("#{rhost}:#{rport} The server replied with #{res1.code} for our initial JSON request, double check TARGETURI and HTTP_METHOD")
			return
		end

		# Deserialize a hash, this should work if YAML deserializes.
		res2 = send_probe("--- {}\n".gsub(':', '\u003a'))

		unless res2
			vprint_status("#{rhost}:#{rport} No reply to the initial YAML probe")
			return
		end

		# Deserialize a malformed object, inducing an error.
		res3 = send_probe("--- !ruby/object:\x00".gsub(':', '\u003a'))

		unless res3
			vprint_status("#{rhost}:#{rport} No reply to the second YAML probe")
			return
		end

		vprint_status("Probe response codes: #{res1.code} / #{res2.code} / #{res3.code}")

		if (res2.code == res1.code) and (res3.code != res2.code) and (res3.code != 200)
			# If first and second requests are the same, and the third is different but not a 200, we're vulnerable.
			print_good("#{rhost}:#{rport} is likely vulnerable due to a #{res3.code} reply for invalid YAML")
			report_vuln({
				:host	=> rhost,
				:port	=> rport,
				:proto  => 'tcp',
				:name	=> self.name,
				:info	=> "Module triggered a #{res3.code} reply",
				:refs   => self.references
			})
		else
			# Otherwise we're not likely vulnerable.
			vprint_status("#{rhost}:#{rport} is not likely to be vulnerable or TARGETURI & HTTP_METHOD must be set")
		end
	end

end