3.3. NewSessionTicket Handshake Message

This message is sent by the server during the TLS handshake before the ChangeCipherSpec message. This message MUST be sent if the server included a SessionTicket extension in the ServerHello. This message MUST NOT be sent if the server did not include a SessionTicket extension in the ServerHello. This message is included in the hash used to create and verify the Finished message. In the case of a full handshake, the server MUST verify the client's Finished message before sending the ticket. The client MUST NOT treat the ticket as valid until it has verified the server's Finished message. If the server determines that it does not want to include a ticket after it has included the SessionTicket extension in the ServerHello, then it sends a zero-length ticket in the NewSessionTicket handshake message.

If the server successfully verifies the client's ticket, then it MAY renew the ticket by including a NewSessionTicket handshake message after the ServerHello in the abbreviated handshake. The client should start using the new ticket as soon as possible after it verifies the server's Finished message for new connections. Note that since the updated ticket is issued before the handshake completes, it is possible that the client may not put the new ticket into use before it initiates new connections. The server MUST NOT assume that the client actually received the updated ticket until it successfully verifies the client's Finished message.

The NewSessionTicket handshake message has been assigned the number 4 and its definition is given at the end of this section. The ticket_lifetime_hint field contains a hint from the server about how long the ticket should be stored. The value indicates the lifetime in seconds as a 32-bit unsigned integer in network byte order relative to when the ticket is received. A value of zero is reserved to indicate that the lifetime of the ticket is unspecified. A client SHOULD delete the ticket and associated state when the time expires. It MAY delete the ticket earlier based on local policy. A server MAY treat a ticket as valid for a shorter or longer period of time than what is stated in the ticket_lifetime_hint.

   struct {
       HandshakeType msg_type;
       uint24 length;
       select (HandshakeType) {
           case hello_request:       HelloRequest;
           case client_hello:        ClientHello;
           case server_hello:        ServerHello;
           case certificate:         Certificate;
           case server_key_exchange: ServerKeyExchange;
           case certificate_request: CertificateRequest;
           case server_hello_done:   ServerHelloDone;
           case certificate_verify:  CertificateVerify;
           case client_key_exchange: ClientKeyExchange;
           case finished:            Finished;
           case session_ticket:      NewSessionTicket; /* NEW */
       } body;
   } Handshake;

   struct {
       uint32 ticket_lifetime_hint;
       opaque ticket<0..2^16-1>;
   } NewSessionTicket;