[15] RFR JDK-8246077: Cloneable test in HmacCore seems questionable

Weijun Wang weijun.wang at oracle.com
Sat Jun 6 05:54:00 UTC 2020


Is it possible to try "md instanceof Cloneable || md.clone() returns"? Hopefully this is fast enough in most cases and also has the chance to recognize more actually-cloneable ones.

I'm also OK with simply using "md instanceof Cloneable".

--Max

> On Jun 6, 2020, at 12:02 PM, Valerie Peng <valerie.peng at oracle.com> wrote:
> 
> 
> I am merely following the spec's recommendation of trying the clone() for cloneability check.
> 
> If you both are ok with it and prefer the instanceof check, I can sure reverting back the changes in HmacCore and HandshakeHash classes.
> 
> Valerie
> 
> On 6/5/2020 2:04 AM, Seán Coffey wrote:
>> I share the same concern. clone() is a heavy weight operation in constructors that can be called alot during intensive crypto operations.
>> 
>> Now that you've done work on Delegate class - why not also keep the (instanceof Cloneable) test ? That can serve as your fastpath for the default JDK configuration AFAIK.
>> 
>> regards,
>> Sean.
>> 
>> On 05/06/2020 00:16, Weijun Wang wrote:
>>> 
>>>> 在 2020年6月5日,03:19,Valerie Peng <valerie.peng at oracle.com> 写道:
>>>> 
>>>>> Can you give an example when these 2 rules have different results? Is this only true for those implementation that directly subclass MessageDigest?
>>>> Before this fix, even the Spi impl implements Cloneable the instanceof check will always fail because the wrapper class, i.e. MessageDigest.Delegate does not. However, if you call the clone() (made public by the MessageDigest class), it will succeed because Delegate.clone() checks to see if the spi object implements the Cloneable interface, if yes, it will proceed to call the spi clone(). So, for this scenario, the results are different, e.g. instanceof returns false, but clone() succeeds. This is just one example. Is this what you are asking?
>>> No.
>>> 
>>> I understand this case, but this has already been fixed. Is there any other example? Or are you only follow the words in the spec? i.e. try clone() to see if it’s cloneable.
>>> 
>>> I am worried that try clone() is much heavier than just check instanof Cloneable.
>>> 
>>> Thanks,
>>> Max



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