RFR: 8366454: TLS1.3 server fails with bad_record_mac when receiving encrypted records with empty body [v2]

[Alice Pellegrini]

> According to RFC 8446 section 5.4, third paragraph 
>> Application Data records may contain a zero-length
>>    TLSInnerPlaintext.content if the sender desires.  This permits
>>    generation of plausibly sized cover traffic in contexts where the
>>    presence or absence of activity may be sensitive.  Implementations
>>    MUST NOT send Handshake and Alert records that have a zero-length
>>    TLSInnerPlaintext.content; if such a message is received, the
>>    receiving implementation MUST terminate the connection with an
>>    "unexpected_message" alert.
> 
> 
> The proposed change removes an off by 1 error in the SSLCipher implementation, forces the correct Alert message to be sent in response to zero-length Alert fragments, as well as updating some tests which detected the BadPaddingException but now detect a SSLProtocolException, which is thrown by `TransportContext.fatal`

Alice Pellegrini has updated the pull request incrementally with one additional commit since the last revision:

  Update copyright, apply suggestions from review, more consistent style for for loop between the two ciphers
  
  Co-authored-by: Daniel Jelinski <daniel.jelinski at oracle.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27438/files
  - new: https://git.openjdk.org/jdk/pull/27438/files/6a99f91a..a76fa9c3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27438&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27438&range=00-01

  Stats: 7 lines in 3 files changed: 0 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/27438.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27438/head:pull/27438

PR: https://git.openjdk.org/jdk/pull/27438