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Revision 1.5, Wed Apr 22 17:05:07 2020 UTC (4 years, 1 month ago) by jsing
Branch: MAIN
CVS Tags: OPENBSD_7_5_BASE, OPENBSD_7_5, OPENBSD_7_4_BASE, OPENBSD_7_4, OPENBSD_7_3_BASE, OPENBSD_7_3, OPENBSD_7_2_BASE, OPENBSD_7_2, OPENBSD_7_1_BASE, OPENBSD_7_1, OPENBSD_7_0_BASE, OPENBSD_7_0, OPENBSD_6_9_BASE, OPENBSD_6_9, OPENBSD_6_8_BASE, OPENBSD_6_8, OPENBSD_6_7_BASE, OPENBSD_6_7, HEAD
Changes since 1.4: +4 -4 lines 

Improve TLSv1.3 state machine for HelloRetryRequest handling.

The state machine currently handles the HelloRetryRequest case by using
WITH_HRR - in other words, we're explicitly indicating when we transition
to the alternate path. The problem here is that we do not know if we're
going to receive a ServerHello or a HelloRetryRequest until we process
the message. This means that the ServerHello processing code has to handle
both types of messages.

The state machine and associated processing code becomes cleaner if we flip
this around so that we assume we are going to receive a HelloRetryRequest
and upon discovering that it is not, trigger WITHOUT_HRR and hand off to
the ServerHello processing function. In particular, this makes the logic
much more straight forward on the server side, when adding support for HRR.

With feedback from tb@

ok tb@

/* $OpenBSD: tls13_handshake.h,v 1.5 2020/04/22 17:05:07 jsing Exp $ */
/*
 * Copyright (c) 2019 Theo Buehler <tb@openbsd.org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef HEADER_TLS13_HANDSHAKE_H
#define HEADER_TLS13_HANDSHAKE_H

#include <stddef.h>	/* for NULL */

__BEGIN_HIDDEN_DECLS

#define INITIAL			0x00
#define NEGOTIATED		0x01
#define WITHOUT_HRR		0x02
#define WITHOUT_CR		0x04
#define WITH_PSK		0x08
#define WITH_CCV		0x10
#define WITH_0RTT		0x20

enum tls13_message_type {
	INVALID,
	CLIENT_HELLO,
	SERVER_HELLO_RETRY_REQUEST,
	CLIENT_HELLO_RETRY,
	SERVER_HELLO,
	SERVER_ENCRYPTED_EXTENSIONS,
	SERVER_CERTIFICATE_REQUEST,
	SERVER_CERTIFICATE,
	SERVER_CERTIFICATE_VERIFY,
	SERVER_FINISHED,
	CLIENT_END_OF_EARLY_DATA,
	CLIENT_CERTIFICATE,
	CLIENT_CERTIFICATE_VERIFY,
	CLIENT_FINISHED,
	APPLICATION_DATA,
	TLS13_NUM_MESSAGE_TYPES,
};

__END_HIDDEN_DECLS

#endif /* !HEADER_TLS13_HANDSHAKE_H */