RFR: 8255557: Decouple GCM from CipherCore [v4]

[Anthony Scarpino]

On Fri, 21 May 2021 00:03:40 GMT, Valerie Peng <valeriep at openjdk.org> wrote:

>> Anthony Scarpino has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix perf problem by reorganizing doLastBlock()
>
> src/java.base/share/classes/com/sun/crypto/provider/GaloisCounterMode.java line 1437:
> 
>> 1435:             } catch (ArrayIndexOutOfBoundsException aiobe) {
>> 1436:                 throw new ShortBufferException("Output buffer invalid");
>> 1437:             }
> 
> I think this should be moved to the very beginning before all the processing and if the output capacity is less than 'len-tagLenBytes' value, then no need to proceed? IIRC, the save/restore is more for algorithms which use padding, may not be needed for GCM?

I had this down here because it's not needed until gctr ops are done and ghash doesn't use an output, but I can move it up.
I remember Sean C having to do save/restore work for GCM.. The tag can create the similar padding issues.  It felt safe to keep it.

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PR: https://git.openjdk.java.net/jdk/pull/4072