Method decryptTicket

ticket.go:370–399

(encrypted []byte, ticketKeys []ticketKey)

}

func (c *Config) decryptTicket(encrypted []byte, ticketKeys []ticketKey) []byte {
	if len(encrypted) < aes.BlockSize+sha256.Size {
		return nil
	}

	iv := encrypted[:aes.BlockSize]
	ciphertext := encrypted[aes.BlockSize : len(encrypted)-sha256.Size]
	authenticated := encrypted[:len(encrypted)-sha256.Size]
	macBytes := encrypted[len(encrypted)-sha256.Size:]
	for _, key := range ticketKeys {
		mac := hmac.New(sha256.New, key.hmacKey[:])
		mac.Write(authenticated)
		expected := mac.Sum(nil)

		if subtle.ConstantTimeCompare(macBytes, expected) != 1 {
			continue
		}

		block, err := aes.NewCipher(key.aesKey[:])
		if err != nil {
			return nil
		}
		plaintext := make([]byte, len(ciphertext))
		cipher.NewCTR(block, iv).XORKeyStream(plaintext, ciphertext)

		return plaintext
	}

	return nil
}

// ClientSessionState contains the state needed by a client to
// resume a previous TLS session.