Code sharing and code isolation

[BOTTARO Andre RD-MAPS-GRE]

 
For security purposes, I would like to prevent bundles from using classes that 
belong to private packages of any bundle.

I checked that if I have a hacking bundle (B) with the following code, it will 
be able to call a method (criticalAlert) on a private class 
(private.packages.Sample) of a bundle (A), i.e. a class which neither exported 
by A nor imported by B. In order to do that, B must acces the classloader of A, 
thus I suppose that B imports an exported package (public.packages) from A:

        public void start(BundleContext bc) throws Exception {  
                //Getting an instance of an exported class from A...
                public.packages.Sample sample = new public.packages.Sample();
        
                //Trying to access the private class from A...
                ClassLoader loader = sample.getClass().getClassLoader();
                Class clazz = loader.loadClass("private.packages.Sample");
                Object o = clazz.newInstance();
                Method m = o.getClass().getMethod("criticalAlert", new 
Class[]{});
                m.invoke(o,new Object[]{});
        }

So, tell me if I am wrong, the OSGi solution to this bundle isolation issue is 
to use Java 2 permissions (with OSGi CPA or PA) to forbid the use of reflection 
(Class.newInstance and java.lang.reflect) to untrusted bundles. 

There is also another threat (even more direct) in OSGi R4 : the use of 
Fragments. Are there other threats ?

André