Method pickCipherSuite

handshake_server.go:328–366

()

}

func (hs *serverHandshakeState) pickCipherSuite() error {
	c := hs.c

	preferenceOrder := cipherSuitesPreferenceOrder
	if !hasAESGCMHardwareSupport || !aesgcmPreferred(hs.clientHello.cipherSuites) {
		preferenceOrder = cipherSuitesPreferenceOrderNoAES
	}

	configCipherSuites := c.config.cipherSuites()
	preferenceList := make([]uint16, 0, len(configCipherSuites))
	for _, suiteID := range preferenceOrder {
		for _, id := range configCipherSuites {
			if id == suiteID {
				preferenceList = append(preferenceList, id)
				break
			}
		}
	}

	hs.suite = selectCipherSuite(preferenceList, hs.clientHello.cipherSuites, hs.cipherSuiteOk)
	if hs.suite == nil {
		c.sendAlert(alertHandshakeFailure)
		return errors.New("tls: no cipher suite supported by both client and server")
	}
	c.cipherSuite = hs.suite.id

	for _, id := range hs.clientHello.cipherSuites {
		if id == TLS_FALLBACK_SCSV {
			// The client is doing a fallback connection. See RFC 7507.
			if hs.clientHello.vers < c.config.maxSupportedVersion(roleClient) {
				c.sendAlert(alertInappropriateFallback)
				return errors.New("tls: client using inappropriate protocol fallback")
			}
			break
		}
	}

	return nil
}

func (hs *serverHandshakeState) cipherSuiteOk(c *cipherSuite) bool {
	if c.flags&suiteECDHE != 0 {