RFR: 8330842: Support AES CBC with Ciphertext Stealing (CTS) in SunPKCS11 [v4]

[Martin Balao]

On Wed, 5 Jun 2024 12:54:45 GMT, Francisco Ferrari Bihurriet <fferrari at openjdk.org> wrote:

>> I have no personal preference, but would suggest that if we change it to cut the pad, we keep the decryption case aligned.
>
> What I like about this suggestion is that it allows unifying the repeated logic: the two blocks inside `if (encrypt)` and the corresponding `else` would become almost identical, allowing an additional abstraction. How about the following?
> 
> 
>     private void convertCTSVariant(ByteBuffer ciphertextBuf,
>             byte[] ciphertextArr, int end) {
>         // [...]
>         // [...] omitted code
>         // [...]
>         if (ciphertextBuf != null) {
>             pad = pad == 0 ? blockSize : pad;
>             if (encrypt) {
>                 // .... pp[pp] ffff -> .... ffff pp[pp]
>                 swapLastTwoBlocks(ciphertextBuf, end, pad, blockSize);
>             } else {
>                 // .... ffff pp[pp] -> .... pp[pp] ffff
>                 swapLastTwoBlocks(ciphertextBuf, end, blockSize, pad);
>             }
>         }
>     }
> 
>     private static void swapLastTwoBlocks(ByteBuffer buffer, int end,
>             int prevBlockLen, int lastBlockLen) {
>         // .... prevBlock lastBlock -> .... lastBlock prevBlock
>         int prevBlockStart = end - prevBlockLen - lastBlockLen;
>         byte[] prevBlockBackup = new byte[prevBlockLen];
>         buffer.get(prevBlockStart, prevBlockBackup);
>         buffer.put(prevBlockStart, buffer, end - lastBlockLen, lastBlockLen);
>         buffer.put(end - prevBlockLen, prevBlockBackup);
>     }

Looks good to me.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18898#discussion_r1627887918