Method ticketKeyFromBytes

common.go:948–958

ticketKeyFromBytes converts from the external representation of a session ticket key to a ticketKey. Externally, session ticket keys are 32 random bytes and this function expands that into sufficient name and key material.

(b [32]byte)

// ticket key to a ticketKey. Externally, session ticket keys are 32 random
// bytes and this function expands that into sufficient name and key material.
func (c *Config) ticketKeyFromBytes(b [32]byte) (key ticketKey) {
	hashed := sha512.Sum512(b[:])
	// The first 16 bytes of the hash used to be exposed on the wire as a ticket
	// prefix. They MUST NOT be used as a secret. In the future, it would make
	// sense to use a proper KDF here, like HKDF with a fixed salt.
	const legacyTicketKeyNameLen = 16
	copy(key.aesKey[:], hashed[legacyTicketKeyNameLen:])
	copy(key.hmacKey[:], hashed[legacyTicketKeyNameLen+len(key.aesKey):])
	key.created = c.time()
	return key
}

// maxSessionTicketLifetime is the maximum allowed lifetime of a TLS 1.3 session
// ticket, and the lifetime we set for all tickets we send.