[TLS] TLS 1.3 - ignoring version values in record protocol header

[David Holmes <[e-mail]>]

On day 1 of the Seattle TLS 1.3 working group, it was questioned what to
do with the TLS version bytes in record protocol. Send but ignore seemed
to be the consensus, with ³pin to [3,4] forever"

In draft 5, if the version bytes are still included in the AEAD
computation, they shouldn¹t be ignored, right?

If we keep the record protocol version bytes, the most straightforward
action is to [continue with the tradition of having them] match the
version of TLS negotiated in the handshake. In this case [3,4].

6.2.2 Record Payload Protection


struct {
          ContentType type;
          ProtocolVersion version;
          uint16 length;
          opaque nonce_explicit[SecurityParameters.record_iv_length];
          aead-ciphered struct {
             opaque content[TLSPlaintext.length];
          } fragment;
} TLSCiphertext;

Š

additional_data = seq_num + TLSPlaintext.type + TLSPlaintext.version

Š

AEADEncrypted = AEAD-Encrypt(write_key, nonce, plaintext, additional_data)