Module: Rex::Post::Meterpreter::Extensions::Stdapi::Railgun::LibraryHelper

Included in:
Library, MultiCaller, Util
Defined in:
lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb

Overview

shared functions

Instance Method Summary collapse

Instance Method Details

#asciiz_to_str(asciiz) ⇒ Object

converts 0-terminated ASCII string to ruby string



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 45

def asciiz_to_str(asciiz)
  zero_byte_idx = asciiz.index("\x00")
  if zero_byte_idx != nil
    return asciiz[0, zero_byte_idx]
  else
    return asciiz
  end
end

#assemble_buffer(direction, function, args, arch) ⇒ Object

assembles the buffers “in” and “inout”



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 94

def assemble_buffer(direction, function, args, arch)
  layout = {} # paramName => BufferItem
  blob = ""
  #puts " building buffer: #{direction}"
  function.params.each_with_index do |param_desc, param_idx|
    #puts "  processing #{param_desc[0]} #{param_desc[1]} #{param_desc[2]}"
    # we care only about inout buffers
    if param_desc[2] == direction
      buffer = nil
      # Special case:
      # The user can choose to supply a Null pointer instead of a buffer
      # in this case we don't need space in any heap buffer
      if param_desc[0][0,1] == 'P' # type is a pointer
        if args[param_idx] == nil
          next
        end
      end

      case param_desc[0] # required argument type
      when 'PULONG_PTR'
        val = param_to_number(args[param_idx])
        buffer = [val].pack(arch == ARCH_X64 ? 'Q<' : 'V')
      when "PDWORD"
        val = param_to_number(args[param_idx])
        buffer = [val].pack('V')
      when "PWCHAR"
        next if args[param_idx].is_a?(Integer) && direction == 'in'
        raise "param #{param_desc[1]}: string or integer expected" unless args[param_idx].class == String
        buffer = str_to_uni_z(args[param_idx])
      when "PCHAR"
        next if args[param_idx].is_a?(Integer) && direction == 'in'
        raise "param #{param_desc[1]}: string or integer expected" unless args[param_idx].class == String
        buffer = str_to_ascii_z(args[param_idx])
      when "PBLOB"
        next if args[param_idx].is_a?(Integer) && direction == 'in'
        args[param_idx] = args[param_idx].to_binary_s if args[param_idx].is_a?(BinData::Struct)

        raise "param #{param_desc[1]}: string or integer expected" unless args[param_idx].class == String
        buffer = args[param_idx]
        # other types (non-pointers) don't reference buffers
        # and don't need any treatment here
      end

      unless buffer.nil?
        #puts "   adding #{buffer.length} bytes to heap blob"
        layout[param_desc[1]] = BufferItem.new(param_idx, blob.length, buffer.length, param_desc[0])
        blob += buffer
        # sf: force 8 byte alignment to satisfy x64, wont matter on x86.
        while blob.length % 8 != 0
          blob += "\x00"
        end
        #puts "   heap blob size now #{blob.length}"
      end
    end
  end
  #puts "  built buffer: #{direction}"
  return [layout, blob]
end

#param_to_number(v, consts_mgr = @consts_mgr) ⇒ Object

parses a number param and returns the value raises an exception if the param cannot be converted to a number examples:

nil => 0
3 => 3
"MB_OK" => 0
"SOME_CONSTANT | OTHER_CONSTANT" => 17
"tuna" => !!!!!!!!!!Exception

Parameter “consts_mgr” is a ConstantManager



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 76

def param_to_number(v, consts_mgr = @consts_mgr)
  if v.class == NilClass then
    return 0
  elsif v.kind_of? Integer then
    return v # ok, it's already a number
  elsif v.kind_of? String then
    dw = consts_mgr.parse(v) # might raise an exception
    if dw != nil
      return dw
    else
      raise ArgumentError, "Param #{v} (class #{v.class}) cannot be converted to a number. It's a string but matches no constants I know."
    end
  else
    raise "Param #{v} (class #{v.class}) should be a number but isn't"
  end
end

#str_to_ascii_z(str) ⇒ Object

converts ruby string to zero-terminated ASCII string



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 40

def str_to_ascii_z(str)
  return str + "\x00"
end

#str_to_uni_z(str) ⇒ Object

converts ruby string to zero-terminated WCHAR string



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 55

def str_to_uni_z(str)
  enc = str.encode('UTF-16LE').force_encoding('binary')
  enc += "\x00\x00"
  return enc
end

#uniz_to_str(uniz) ⇒ Object

converts 0-terminated UTF16 to ruby string



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# File 'lib/rex/post/meterpreter/extensions/stdapi/railgun/library_helper.rb', line 62

def uniz_to_str(uniz)
  uniz.force_encoding('UTF-16LE').encode('UTF-8')
end