Re: Proposed PRF changes to address Ken's comments

[Seema Malkani <Seema.Malkani at Sun.COM>]

Nicolas Williams wrote:

> - I await a reply from Seema about Ken's Java bindings question.
>
>
> Comments?
>
> Nico
>  
To answer Ken's question :

Adding a new method to a standardized interface will break existing 
applications. This means all classes that implement GSSContext interface 
will now need to add the new method. All implementations of Java GSS 
will NOT compile until the new method is added.

Abstract classes don't have such a problem, since you can provide a 
default (possibly empty) implementation, and existing implementations 
will not break. It is easier to evolve an abstract class than to evolve 
an interface. Since GSSContext was defined to be an interface, we cannot 
change it.

Alternatives ?

We can possibly add the new method to GSSManager class, which is an 
abstract class. This class serves as a factory for three GSS interfaces: 
GSSName, GSSCredential, and GSSContext. The new method will have to be 
invoked after the GSSContext has been established.

GSSManager class:
public byte[] prf(GSSContext context, int prf_key, byte[] inBuf, int outlen)
        throws GSSException

GSSManager mgr = GSSManager.getInstance();
GSSName targetName = mgt.createName("service at host", ..);
GSSContext context = mgr.createContext(targetName, ..);
..
if (context.isEstablished()) {
  // define PRF key, input..
  int prf_key = ..
  ..
  byte[] prf_out = mgr.prf(context, prf_key, inBuf, outlen);
}

Seema



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