Lots of allocations in CipherCore

[Anthony Scarpino]

Hi,

I think it's a mistake. Looking at the old code I believe the if() for 
cipher.save() above that was suppose to include the new byte allocation 
and offset, but got missed.

Feel free to fix it if you like.  Let me know if you need something.

Tony

On 1/25/22 12:06 PM, Sebastian Stenzel wrote:
> Hi all,
> 
> while playing around with JFR today, I stumbled upon a piece of code 
> that causes a thousands of byte[] allocations. In fact it is responsible 
> for 90% of the memory allocations in my application and causes GC to run 
> without pause during decryption of large files.
> 
> The line in question can be found here [1]. The behaviour can be 
> triggered with a simple AES-CTR cipher as in this minimal example [2].
> 
> As you can see, the comments in [1] even say that this byte[] _should_ 
> only be allocated if there is insufficient space in the provided output 
> buffer. However some kind of conditional statement is missing.
> 
> There used to be a `if (getMode() != GCM_MODE || outputCapacity < 
> estOutSize)`, before GCM has been decoupled from CipherCore. But this 
> line seems wrong to me either.
> 
> I guess this should be fixed, as I'm probably not the only one affected 
> by those allocations. I'd be volunteering, unless the behaviour is intended.
> 
> Cheers!
> Sebastian
> 
> 
> [1] 
> https://github.com/openjdk/jdk/blob/76fe03fe01a7c824e2e9263de95b8bcbb4b9d752/src/java.base/share/classes/com/sun/crypto/provider/CipherCore.java#L815-L818 
> <https://github.com/openjdk/jdk/blob/76fe03fe01a7c824e2e9263de95b8bcbb4b9d752/src/java.base/share/classes/com/sun/crypto/provider/CipherCore.java#L815-L818>
> [2] 
> https://gist.github.com/overheadhunter/f3969950c0fdbaecaa77c857b2246cc5 
> <https://gist.github.com/overheadhunter/f3969950c0fdbaecaa77c857b2246cc5>
> 
>