module Msf

require 'msf/core/exploit/tcp'

###
#
# This module exposes methods that may be useful to exploits that deal with
# servers that speak the telnet protocol.
#
###
module Exploit::Remote::Telnet

	include Exploit::Remote::Tcp

	# Borrowing constants from Ruby's Net::Telnet class (ruby license)
    IAC   = 255.chr # "\377" # "\xff" # interpret as command
    DONT  = 254.chr # "\376" # "\xfe" # you are not to use option
    DO    = 253.chr # "\375" # "\xfd" # please, you use option
    WONT  = 252.chr # "\374" # "\xfc" # I won't use option
    WILL  = 251.chr # "\373" # "\xfb" # I will use option
    SB    = 250.chr # "\372" # "\xfa" # interpret as subnegotiation
    GA    = 249.chr # "\371" # "\xf9" # you may reverse the line
    EL    = 248.chr # "\370" # "\xf8" # erase the current line
    EC    = 247.chr # "\367" # "\xf7" # erase the current character
    AYT   = 246.chr # "\366" # "\xf6" # are you there
    AO    = 245.chr # "\365" # "\xf5" # abort output--but let prog finish
    IP    = 244.chr # "\364" # "\xf4" # interrupt process--permanently
    BREAK = 243.chr # "\363" # "\xf3" # break
    DM    = 242.chr # "\362" # "\xf2" # data mark--for connect. cleaning
    NOP   = 241.chr # "\361" # "\xf1" # nop
    SE    = 240.chr # "\360" # "\xf0" # end sub negotiation
    EOR   = 239.chr # "\357" # "\xef" # end of record (transparent mode)
    ABORT = 238.chr # "\356" # "\xee" # Abort process
    SUSP  = 237.chr # "\355" # "\xed" # Suspend process
    EOF   = 236.chr # "\354" # "\xec" # End of file
    SYNCH = 242.chr # "\362" # "\xf2" # for telfunc calls

    OPT_BINARY         =   0.chr # "\000" # "\x00" # Binary Transmission
    OPT_ECHO           =   1.chr # "\001" # "\x01" # Echo
    OPT_RCP            =   2.chr # "\002" # "\x02" # Reconnection
    OPT_SGA            =   3.chr # "\003" # "\x03" # Suppress Go Ahead
    OPT_NAMS           =   4.chr # "\004" # "\x04" # Approx Message Size Negotiation
    OPT_STATUS         =   5.chr # "\005" # "\x05" # Status
    OPT_TM             =   6.chr # "\006" # "\x06" # Timing Mark
    OPT_RCTE           =   7.chr # "\a"   # "\x07" # Remote Controlled Trans and Echo
    OPT_NAOL           =   8.chr # "\010" # "\x08" # Output Line Width
    OPT_NAOP           =   9.chr # "\t"   # "\x09" # Output Page Size
    OPT_NAOCRD         =  10.chr # "\n"   # "\x0a" # Output Carriage-Return Disposition
    OPT_NAOHTS         =  11.chr # "\v"   # "\x0b" # Output Horizontal Tab Stops
    OPT_NAOHTD         =  12.chr # "\f"   # "\x0c" # Output Horizontal Tab Disposition
    OPT_NAOFFD         =  13.chr # "\r"   # "\x0d" # Output Formfeed Disposition
    OPT_NAOVTS         =  14.chr # "\016" # "\x0e" # Output Vertical Tabstops
    OPT_NAOVTD         =  15.chr # "\017" # "\x0f" # Output Vertical Tab Disposition
    OPT_NAOLFD         =  16.chr # "\020" # "\x10" # Output Linefeed Disposition
    OPT_XASCII         =  17.chr # "\021" # "\x11" # Extended ASCII
    OPT_LOGOUT         =  18.chr # "\022" # "\x12" # Logout
    OPT_BM             =  19.chr # "\023" # "\x13" # Byte Macro
    OPT_DET            =  20.chr # "\024" # "\x14" # Data Entry Terminal
    OPT_SUPDUP         =  21.chr # "\025" # "\x15" # SUPDUP
    OPT_SUPDUPOUTPUT   =  22.chr # "\026" # "\x16" # SUPDUP Output
    OPT_SNDLOC         =  23.chr # "\027" # "\x17" # Send Location
    OPT_TTYPE          =  24.chr # "\030" # "\x18" # Terminal Type
    OPT_EOR            =  25.chr # "\031" # "\x19" # End of Record
    OPT_TUID           =  26.chr # "\032" # "\x1a" # TACACS User Identification
    OPT_OUTMRK         =  27.chr # "\e"   # "\x1b" # Output Marking
    OPT_TTYLOC         =  28.chr # "\034" # "\x1c" # Terminal Location Number
    OPT_3270REGIME     =  29.chr # "\035" # "\x1d" # Telnet 3270 Regime
    OPT_X3PAD          =  30.chr # "\036" # "\x1e" # X.3 PAD
    OPT_NAWS           =  31.chr # "\037" # "\x1f" # Negotiate About Window Size
    OPT_TSPEED         =  32.chr # " "    # "\x20" # Terminal Speed
    OPT_LFLOW          =  33.chr # "!"    # "\x21" # Remote Flow Control
    OPT_LINEMODE       =  34.chr # "\""   # "\x22" # Linemode
    OPT_XDISPLOC       =  35.chr # "#"    # "\x23" # X Display Location
    OPT_OLD_ENVIRON    =  36.chr # "$"    # "\x24" # Environment Option
    OPT_AUTHENTICATION =  37.chr # "%"    # "\x25" # Authentication Option
    OPT_ENCRYPT        =  38.chr # "&"    # "\x26" # Encryption Option
    OPT_NEW_ENVIRON    =  39.chr # "'"    # "\x27" # New Environment Option
    OPT_EXOPL          = 255.chr # "\377" # "\xff" # Extended-Options-List

    NULL = "\000"
    CR   = "\015"
    LF   = "\012"
    EOL  = CR + LF


	#
	# Creates an instance of a Telnet exploit module.
	#
	def initialize(info = {})
		super

		# Register the options that all Telnet exploits may make use of.
		register_options(
			[
				Opt::RHOST,
				Opt::RPORT(23),
				OptString.new('USERNAME', [ false, 'The username to authenticate as' ]),
				OptString.new('PASSWORD', [ false, 'The password for the specified username' ])
			], Msf::Exploit::Remote::Telnet)

		register_advanced_options(
			[
				OptInt.new('TelnetTimeout', [ true, 'The number of seconds to wait for a reply from a Telnet command', 10]),
				OptInt.new('TelnetBannerTimeout', [ true, 'The number of seconds to wait for the initial banner', 25])
			], Msf::Exploit::Remote::Telnet)

		register_autofilter_ports([ 23 ])
		register_autofilter_services(%W{ telnet })
	end

	#
	# This method establishes an Telnet connection to host and port specified by
	# the RHOST and RPORT options, respectively.  After connecting, the banner
	# message is read in and stored in the 'banner' attribute. This method has the
	# benefit of handling telnet option negotiation.
	#
	def connect(global = true, verbose = true)
		fd = super(global)

		self.banner = ''
		# Wait for a banner to arrive...
		begin
		Timeout.timeout(datastore['TelnetBannerTimeout']) do
			while(true)
				buff = recv_telnet(fd)
				self.banner << buff if buff
				if(self.banner =~ /login|user|welcome|pass|\$|\#/i)
					break
				end
			end
		end
		rescue ::Timeout::Error
		end

		self.banner.strip!

		# Return the file descriptor to the caller
		fd
	end


	#
	# Handle telnet option negotiation
	#
	def recv_telnet(fd=self.sock, timeout=datastore['TelnetTimeout'])

		data = fd.get_once(-1, timeout.to_i)
		return nil if not data

		# combine CR+NULL into CR
		data.gsub!(/#{CR}#{NULL}/no, CR)

		# combine EOL into "\n"
		data.gsub!(/#{EOL}/no, "\n")

		data.gsub(/#{IAC}(
		            [#{IAC}#{AO}#{AYT}#{DM}#{IP}#{NOP}]|
		            [#{DO}#{DONT}#{WILL}#{WONT}]
		                [#{OPT_BINARY}-#{OPT_NEW_ENVIRON}#{OPT_EXOPL}]|
		            #{SB}[^#{IAC}]*#{IAC}#{SE}
		            )/xno) do
            m = $1

			if m == IAC
				IAC
			elsif m == AYT
				fd.write("YES" + EOL)
			elsif m[0,1] == DO
				if(m[1,1] == OPT_BINARY)
					fd.write(IAC + WILL + OPT_BINARY)
				else
					fd.write(IAC + WONT + m[1,1])
				end
				''
			elsif m[0,1] == DONT
				fd.write(IAC + WONT + m[1,1])
				''
			elsif m[0,1] == WILL
				if m[1,1] == OPT_BINARY
					fd.write(IAC + DO + OPT_BINARY)
				# We already print user input, so echo is unnecessary and looks
				# weird on a session.
				elsif m[1,1] == OPT_ECHO
					fd.write(IAC + DO + OPT_ECHO)
				elsif m[1,1] == OPT_SGA
					fd.write(IAC + DO + OPT_SGA)
				else
					fd.write(IAC + DONT + m[1,1])
				end
				''
			elsif m[0,1] == WONT
				fd.write(IAC + DONT + m[1,1])
     			''
			else
				''
			end
 		end
	end

	def user
		datastore["USERNAME"]
	end
	def pass
		datastore["PASSWORD"]
	end

	#
	# Connect and login to the remote telnet server using the credentials
	# that have been supplied in the exploit options.
	#
	def connect_login(global = true, verbose = true)
		telsock = connect(global, verbose)

		if !(user and pass)
			print_status("No username and password were supplied, unable to login")
			return false
		end

		print_status("Authenticating as #{user} with password #{pass}...") if verbose
		res = send_user(user, telsock)

		if (pass)
			print_status("Sending password...") if verbose
			res = send_pass(pass, telsock)
			if (res =~ /fail/i)
				print_status("The server rejected our password") if verbose
				return false
			end
		end

		return telsock
	end

	#
	# This method logs in as the supplied user by transmitting the username
	#
	def send_user(user, nsock = self.sock)
		raw_send("#{user}\r\n", nsock)
		recv_telnet(nsock)
	end

	#
	# This method completes user authentication by sending the supplied password
	#
	def send_pass(pass, nsock = self.sock)
		raw_send("#{pass}\r\n", nsock)
		# Some servers send options after a successful login, so we have to
		# recv all of those before we see the initial prompt.  Some servers
		# send a single newline before the next login prompt after a failed
		# login, so strip the response to check for that.
		resp = recv_telnet(nsock)
		while (resp and resp.strip.length == 0)
			resp = recv_telnet(nsock)
		end
		# Server didn't like our credentials if they give us nothing or a
		# failure message.  Otherwise, assume login succeeded
		return (not resp or resp !~ /fail|incorrect/i)
	end

	#
	# This method sends one command with zero or more parameters
	#
	def send_cmd(args, recv = true, nsock = self.sock)
		cmd = args.join(" ") + "\r\n"
		ret = raw_send(cmd, nsock)
		if (recv)
			return recv_telnet(nsock)
		end
		return ret
	end

	#
	# This method transmits a telnet command and does not wait for a response
	#
	def raw_send(cmd, nsock = self.sock)
		nsock.put(cmd)
	end

	##
	#
	# Wrappers for getters
	#
	##

	#
	# Returns the number of seconds to wait for a telnet reply
	#
	def tel_timeout
		(datastore['TelnetTimeout'] || 10).to_i
	end

protected

	#
	# This attribute holds the banner that was read in after a successful call
	# to connect or connect_login.
	#
	attr_accessor :banner

end

end