1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $FreeBSD$
28 */
29#pragma once
30
31#include <sys/systm.h>
32
33/*
34 * The root BRNG seed version, or generation.
35 *
36 * FenestrasX-aware downstream CSPRNGs (i.e., arc4random(9)) should track the
37 * generation number they seeded from, using the read_random_key(9) API below.
38 * If their current seed version is older than the root generation, they should
39 * reseed before producing output.
40 *
41 * The variable is read-only outside of the fenestrasX implementation and
42 * should be accessed using 'atomic_load_acq_64(&fxrng_root_generation)'.
43 * Reseeds are extremely infrequent, so callers may wish to hint to the
44 * compiler that a matching generation is the expected case, with
45 * __predict_true() or __predict_false().
46 */
47extern uint64_t __read_mostly fxrng_root_generation;
48
49/*
50 * A routine for generating seed/key material
51 * Bypasses random(4) for now, but conceivably could be incorporated into that.
52 */
53void read_random_key(void *buf, size_t nbytes, uint64_t *seed_version_out);
54