# Copyright (c) 2010, patrickHVE@googlemail.com
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#
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module Rex
module Post
module Meterpreter
module Extensions
module Stdapi
module Railgun

#
# represents one function, e.g. MessageBoxW
#
class DLLFunction
	@@allowed_datatypes = {
		"VOID"   => ["return"],
		"BOOL"   => ["in", "return"],
		"DWORD"  => ["in", "return"],
		"WORD"   => ["in", "return"],
		"BYTE"   => ["in", "return"],
		"LPVOID" => ["in", "return"], # sf: for specifying a memory address (e.g. VirtualAlloc/HeapAlloc/...) where we dont want ot back it up with actuall mem ala PBLOB
		"HANDLE" => ["in", "return"],
		"PDWORD" => ["in", "out", "inout"], # todo: support for functions that return pointers to strings
		"PWCHAR" => ["in", "out", "inout"],
		"PCHAR"  => ["in", "out", "inout"],
		"PBLOB"  => ["in", "out", "inout"],
	}.freeze

	@@directions = ["in", "out", "inout", "return"].freeze

	attr_reader :return_type,  :params, :windows_name

	def initialize(return_type, params, windows_name)
		check_return_type(return_type) # we do error checking as early as possible so the library is easier to use
		check_params(params)
		@return_type = return_type
		@params = params
		@windows_name = windows_name
	end

	private

	def check_type_exists (type)
		if not @@allowed_datatypes.has_key?(type)
			raise ArgumentError, "Type unknown: #{type}. Allowed types: #{PP.pp(@@allowed_datatypes.keys, "")}"
		end
	end

	def check_return_type (type)
		check_type_exists(type)
		if not @@allowed_datatypes[type].include?("return")
			raise ArgumentError, "#{type} is not allowed as a return type"
		end
	end

	def check_params (params)
		params.each do |param|
			raise ArgumentError, "each param must be descriped by a three-tuple [type,name,direction]" unless param.length == 3
			type = param[0]
			direction = param[2]

			# Assert a valid type
			check_type_exists(type)

			# Only our set of predefined directions are valid
			unless @@directions.include?(direction)
				raise ArgumentError, "invalid direction: #{direction}"
			end

			# 'return' is not a valid direction in this context
			unless direction != "return"
				raise "direction 'return' is only for the return value of the function."
			end
		end
	end

end

end; end; end; end; end; end