RFR: JDK-6676643: Improve current C_GetAttributeValue native implementation

[Greg Rubin]

On Tue, 27 Apr 2021 18:36:28 GMT, Valerie Peng <valeriep at openjdk.org> wrote:

>> src/jdk.crypto.cryptoki/share/native/libj2pkcs11/p11_objmgmt.c line 252:
>> 
>>> 250: 
>>> 251:     if (rv != CKR_OK) {
>>> 252:         if (rv == CKR_ATTRIBUTE_SENSITIVE || rv == CKR_ATTRIBUTE_TYPE_INVALID) {
>> 
>> According to the PKCS#11v2.40 spec, `CKR_BUFFER_TOO_SMALL` should be handled in the same special ways as these too (in that it isn't a "true error").
>
> For this particular call, the pValue field is null, it's meant to query the exact length of the specified attribute. Thus, CKR_BUFFER_TOO_SMALL should not be returned. 
> Afterwards, we then allocate the buffer based on this queried result, so CKR_BUFFER_TOO_SMALL should also not occur.
> So, based on the current API usage, CKR_BUFFER_TOO_SMALL should not happen.

All my concerns are addressed then. So, while my review doesn't count towards acceptance of this change, everything LGTM.

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PR: https://git.openjdk.java.net/jdk/pull/3709