RFR: 8297878: KEM: Implementation [v2]

[Weijun Wang]

On Thu, 13 Apr 2023 21:43:24 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

>>> Currently, `provider()` is a method of `KEM.Encapsulator`. If `KEMSpi. newEncapsulator` also returns this interface, then what value should its `provider()` method return? This is what I meant registering itself to a provider.
>>> 
>>> When I said different instances, I was asking
>>> 
>>> ```
>>> var k = KEM.getInstance("DHKEM", p);
>>> var e = k.newEncapsulator(pk);
>>> // now, is p == e.provider()?
>>> ```
>>> 
>>> Or, are you suggesting we should define `provider()` somewhere else? It's possible, but I have difficulty making every class immutable.
>> 
>> If the provider() method in KEM.Encapsulator is the only reason, the cost to support it may be too high with so many duplicated/similar specifications/names and code.
>> 
>> Option 1: Remove the KEM.Encapsulator.provider() method, and provide no access to the underlying provider object.
>> 
>>>  do you expect it to return new SunJCE()? This means the p in getInstance("DHKEM", p) will be a different instance from the value returned by getProvider(). 
>> 
>> The Provider class is mutable, we may not want to change the provider object asked for "DHKEM".  I think you have used a solution to pass the provider object in the KEM.java implementation currently.  Maybe, it could be twitted a little bit so that the provider can be passed to a delegated KM.Encapsulator interface implementation.
>> 
>> Option 2:
>> 
>> public final class KEM {
>>     interface Encapsulator {
>>         ...
>>         KEM.Encapsulated encapsulate(...);
>>         ...
>>         
>>         default Provider provider() {
>>             return null;
>>         }
>>     }
>>     
>>     private static class DelegatedEncapsulator implements Encapsulator {
>>         private final Provider p;
>>         private DelegatedEncapsulator(Encapsulator e, Provider p) {
>>             this.p = p;
>>             ...
>>         } 
>>         public Provider provider() {
>>             return this.p;
>>         }
>>     }
>> 
>>     ...
>>           KEMSpi spi = (KEMSpi) service.newInstance(null);
>>           return new DelegatedEncapsulator(
>>                        spi.engineNewEncapsulator(pk, spec, secureRandom),  // This is the interface implementation, use the same provider as KEM.
>>                 service.getProvider());    // This is the provider passed to the delegated KEM.Encapsulator object.
>>     ...
>> }
>
> For more details about option 2, please refer to https://github.com/openjdk/jdk/pull/13470/files.  The KEM.java and KEMSpi.java is pretty much the same except the clean up of En/Decapsulator(s) in this PR.

I see. So the security providers are told:
1. Don't implement `provider()` (If you do, we won't look at it)
2. Do validate parameters on your own (because no one else does)

Let me think about it. I can even ask a security provider what their opinion is.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13256#discussion_r1166948493