Method checkForResumption

handshake_server.go:442–543

checkForResumption reports whether we should perform resumption on this connection.

()

// checkForResumption reports whether we should perform resumption on this connection.
func (hs *serverHandshakeState) checkForResumption() error {
	c := hs.c

	if c.config.SessionTicketsDisabled {
		return nil
	}

	var sessionState *SessionState
	if c.config.UnwrapSession != nil {
		ss, err := c.config.UnwrapSession(hs.clientHello.sessionTicket, c.connectionStateLocked())
		if err != nil {
			return err
		}
		if ss == nil {
			return nil
		}
		sessionState = ss
	} else {
		plaintext := c.config.decryptTicket(hs.clientHello.sessionTicket, c.ticketKeys)
		if plaintext == nil {
			return nil
		}
		ss, err := ParseSessionState(plaintext)
		if err != nil {
			return nil
		}
		sessionState = ss
	}

	// TLS 1.2 tickets don't natively have a lifetime, but we want to avoid
	// re-wrapping the same master secret in different tickets over and over for
	// too long, weakening forward secrecy.
	createdAt := time.Unix(int64(sessionState.createdAt), 0)
	if c.config.time().Sub(createdAt) > maxSessionTicketLifetime {
		return nil
	}

	// Never resume a session for a different TLS version.
	if c.vers != sessionState.version {
		return nil
	}

	cipherSuiteOk := false
	// Check that the client is still offering the ciphersuite in the session.
	for _, id := range hs.clientHello.cipherSuites {
		if id == sessionState.cipherSuite {
			cipherSuiteOk = true
			break
		}
	}
	if !cipherSuiteOk {
		return nil
	}

	// Check that we also support the ciphersuite from the session.
	suite := selectCipherSuite([]uint16{sessionState.cipherSuite},
		c.config.supportedCipherSuites(), hs.cipherSuiteOk)
	if suite == nil {