1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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#pragma once
28
29#include <sys/systm.h>
30
31/*
32 * The root BRNG seed version, or generation.
33 *
34 * FenestrasX-aware downstream CSPRNGs (i.e., arc4random(9)) should track the
35 * generation number they seeded from, using the read_random_key(9) API below.
36 * If their current seed version is older than the root generation, they should
37 * reseed before producing output.
38 *
39 * The variable is read-only outside of the fenestrasX implementation and
40 * should be accessed using 'atomic_load_acq_64(&fxrng_root_generation)'.
41 * Reseeds are extremely infrequent, so callers may wish to hint to the
42 * compiler that a matching generation is the expected case, with
43 * __predict_true() or __predict_false().
44 */
45extern uint64_t __read_mostly fxrng_root_generation;
46
47/*
48 * A routine for generating seed/key material
49 * Bypasses random(4) for now, but conceivably could be incorporated into that.
50 */
51void read_random_key(void *buf, size_t nbytes, uint64_t *seed_version_out);
52