How to allow access to only some specific ruby classes?

Question

I'm trying to use jruby as a script language (for writing quests for a game), but I need to prevent usage of potentially dangerous classes like Dir, Process or RubyVM.

I already found a cumbersome way to blacklist single methods and classes:

class Dir
    def Dir.[]
    end
    def Dir.chdir
    end
    def Dir.chroot
    end
    def Dir.delete
    end
    def Dir.entries
    end
    def Dir.exist?
    end
    def Dir.exists?
    end
    def Dir.foreach
    end
    def Dir.getwd
    end
    def Dir.glob
    end
    def Dir.home
    end
    def Dir.mkdir
    end
    def Dir.initialitze
    end
    def Dir.open
    end
    def Dir.pwd
    end
    def Dir.rmdir
    end
    def Dir.unlink
    end
    def close
    end
    def each
    end
    def fileno
    end
    def inspect
    end
    def path
    end
    def pos
    end
    def read
    end
    def rewind
    end
    def seek
    end
    def tell
    end
    def to_path
    end
end

But I really hope that there is a much easier way to perform this task or even better whitelist the classes that should be able to use.

Answer 1

You can just make specific methods private:

class Dir
  private :close, :each ....
  private_class_method :glob, :home ...
end

Or you can undefine whole class (bad idea as for me):

Object.send(:remove_const, :Dir)

Or remove methods (also bad idea to remove methods from Ruby core class):

class Dir
  remove_method :close, :each ....
end