/*
  Copyright (c) 2012-2015, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/**
   \file

   ec25519-fhmqvc protocol: handshake handling
*/


#pragma once

#include "ec25519_fhmqvc.h"


/**
   An ephemeral keypair used for the handshake protocol

   When a keypair's \e preferred_till has timed out, a new keypair
   will be generated.
*/
typedef struct handshake_key {
	/**
	   With each keypair, the serial number gets incremented.
	   By saving the serial number for established sessions,
	   it can be ensured that no two sessions with the same peer are established
	   with the same keypair
	*/
	uint64_t serial;

	fastd_timeout_t preferred_till;		/**< Specifies how long this keypair will be used for new handshakes */
	fastd_timeout_t valid_till;		/**< Specifies how long handshakes using this keypair will be answered */

	keypair_t key;				/**< The actual keypair */
} handshake_key_t;

/**
   The protocol-specific global state

   There are up to two keys valid at the same time.
*/
struct fastd_protocol_state {
	handshake_key_t prev_handshake_key;	/**< The previously generated handshake keypair */
	handshake_key_t handshake_key;		/**< The newest handshake keypair */
};


/** Checks if a handshake keypair is currently valid */
static inline bool is_handshake_key_valid(const handshake_key_t *handshake_key) {
	return !fastd_timed_out(handshake_key->valid_till);
}

/** Checks if a handshake keypair is currently peferred */
static inline bool is_handshake_key_preferred(const handshake_key_t *handshake_key) {
	return !fastd_timed_out(handshake_key->preferred_till);
}