From: Anthony Wright <anthony@...>
Date: 2010-10-12T21:34:32+09:00
Subject: Using DRB as a secure interface

Is it possible to implement a secure interface exposed to the internet 
using DRB?

I want to pass complex structures through an external API and DRB seems 
like an obvious choice, but I'm concerned that DRB will allow code to 
pass as well as the data, or methods to be called that I didn't want to 
be exposed.

Are my concerns well founded and if so, is there a way to secure the 
interface?

 From my simple tests, any modifications to a standard class are not 
passed, and non-standard classes are not passed either.

I tie down the interface class by creating an "EmptyClass" and 
subclassing the interface class from that.

class EmptyClass
	safe_methods = 
[:__send__,:__id__,:inspect,:respond_to?,:to_s,:private_methods,:protected_methods,:object_id]

	(instance_methods - safe_methods).each do |method|
		undef_method method
	end
end

I also carefully check the data in the arguments too. I tried to use 
$SAFE, but it got in the way rather than helped.

Could anybody provide advice on securing DRB and the proper use of $SAFE 
for argument checking?

thanks,

Anthony Wright.