# -*- coding: binary -*-
# Copyright (c) 2010, patrickHVE@googlemail.com
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#     * Redistributions of source code must retain the above copyright
#       notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
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#       derived from this software without specific prior written permission.
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# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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module Rex
module Post
module Meterpreter
module Extensions
module Stdapi
module Railgun

#
# represents one function, e.g. MessageBoxW
#
class LibraryFunction
  @@allowed_datatypes = {
    'VOID'       => ['return'],
    'BOOL'       => ['in', 'return'],
    'BYTE'       => ['in', 'return'],
    'WORD'       => ['in', 'return'],
    'DWORD'      => ['in', 'return'],
    'LPVOID'     => ['in', 'return'], # sf: for specifying a memory address (e.g. VirtualAlloc/HeapAlloc/...) where we don't want to back it up with actual mem ala PBLOB
    'ULONG_PTR'  => ['in', 'return'],
    'PDWORD'     => ['in', 'out', 'inout'], # todo: support for functions that return pointers to strings
    'PULONG_PTR' => ['in', 'out', 'inout', 'return'],
    'PWCHAR'     => ['in', 'out', 'inout', 'return'],
    'PCHAR'      => ['in', 'out', 'inout', 'return'],
    'PBLOB'      => ['in', 'out', 'inout'],
  }.freeze

  @@allowed_convs = ['stdcall', 'cdecl']

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

  attr_reader :return_type,  :params, :remote_name, :calling_conv

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

  private

  def check_calling_conv(conv)
    if not @@allowed_convs.include?(conv)
      raise ArgumentError, "Calling convention unknown: #{conv}."
    end
  end

  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 described 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
      if direction == "return"
        raise "direction 'return' is only for the return value of the function."
      end
    end
  end
end

end; end; end; end; end; end