RFR: 8353578: Refactor existing usage of internal HKDF impl to use the KDF API [v4]

[Daniel Jeliński]

On Fri, 25 Apr 2025 18:40:17 GMT, Valerie Peng <valeriep at openjdk.org> wrote:

>> src/java.base/share/classes/sun/security/ssl/KAKeyDerivation.java line 131:
>> 
>>> 129: 
>>> 130:             // derive handshake secret
>>> 131:             return hkdf.deriveKey(type, HKDFParameterSpec.ofExtract()
>> 
>> The line above may fail because the `hkdf` object has been used once on line 121 with zero-valued salt and IKM, which selected the software-based HKDF from SunJCE. At this point, however, `sharedSecret` is the result of ECDH and may be non-extractable if produced by an HSM, making it incompatible with the SunJCE implementation. To avoid this issue, get a new `hkdf` by calling `hkdf = KDF.getInstance(hashAlg.hkdfAlgorithm)` before this line.
>
> Hmm, ok, interesting scenario. I add another `KDF.getInstance()` call as you suggested just to be safe.

I think that deserves a code comment; it's far from obvious why we do that. Also, we will make P11 work with zero-valued salt soon.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24393#discussion_r2060870152