#!/usr/bin/ruby

module Rex
module Post
module Meterpreter

###
#
# PacketParser
# ------------
#
# This class is responsible for reading in and decrypting meterpreter
# packets that arrive on a socket
#
###
class PacketParser

	# Initializes the packet parser context with an optional cipher
	def initialize(cipher = nil)
		self.cipher = cipher

		reset
	end

	# Resets the parser state so that a new packet can begin being parsed
	def reset
		self.raw = ''
		self.hdr_length_left = 8
		self.payload_length_left = 0
	end

	# Reads data from the wire
	def recv(sock)
		if (self.hdr_length_left > 0)
			buf = sock.read(self.hdr_length_left)

			if (buf)
				self.raw << buf

				self.hdr_length_left -= buf.length
			else
				raise EOFError
			end

			# If we've finished reading the header, set the
			# payload length left to the number of bytes
			# specified in the length
			if (self.hdr_length_left == 0)
				self.payload_length_left = raw.unpack("N")[0] - 8
			end
		elsif (self.payload_length_left > 0)
			buf = sock.read(self.payload_length_left)

			if (buf)
				self.raw << buf

				self.payload_length_left -= buf.length
			else
				raise EOFError
			end
		end

		# If we've finished reading the entire packet
		if ((self.hdr_length_left == 0) &&
		    (self.payload_length_left == 0))

			# Create a typeless packet
			packet = Packet.new(0)

			# TODO: cipher decryption
			if (cipher)
			end

			# Serialize the packet from the raw buffer
			packet.from_r(self.raw)

			# Reset our state
			reset

			return packet
		end
	end
	
protected
	attr_accessor :cipher, :raw, :hdr_length_left, :payload_length_left

end


end; end; end