1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer
12 *    in this position and unchanged.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/param.h>
34#include <sys/kernel.h>
35#include <sys/lock.h>
36#include <sys/module.h>
37#include <sys/random.h>
38#include <sys/systm.h>
39
40#include <dev/random/randomdev.h>
41#include <dev/random/randomdev_soft.h>
42#include <dev/random/random_adaptors.h>
43#include <dev/random/live_entropy_sources.h>
44
45static void live_random_example_init(void);
46static void live_random_example_deinit(void);
47static u_int live_random_example_read(void *, u_int);
48
49struct random_adaptor live_random_example = {
50	.les_ident = "Example RNG",
51	.les_source = RANDOM_PURE_BOGUS, /* Make sure this is in
52					  * sys/random.h and is unique */
53	.les_read = live_random_example_read,
54};
55
56/*
57 * Used under the license provided @ http://xkcd.com/221/
58 * http://creativecommons.org/licenses/by-nc/2.5/
59 */
60static uint8_t
61getRandomNumber(void)
62{
63	return 4;   /* chosen by fair dice roll, guaranteed to be random */
64}
65
66static void
67live_random_example_init(void)
68{
69
70	/* Do initialisation stuff here */
71}
72
73static void
74live_random_example_deinit(void)
75{
76
77	/* Do de-initialisation stuff here */
78}
79
80/* get <c> bytes of random stuff into <buf>. You may presume
81 * that <c> is a multiple of 2^n, with n>=3. A typical value
82 * is c=16.
83 */
84static u_int
85live_random_example_read(void *buf, u_int c)
86{
87	uint8_t *b;
88	int count;
89
90	b = buf;
91
92	for (count = 0; count < c; count++)
93		b[count] = getRandomNumber();
94
95	/* printf("returning %d bytes of pure randomness\n", c); */
96	return (c);
97}
98
99/* ARGSUSED */
100static int
101live_random_example_modevent(module_t mod __unused, int type, void *unused __unused)
102{
103	int error = 0;
104
105	switch (type) {
106	case MOD_LOAD:
107		live_entropy_source_register(&live_random_example);
108		break;
109
110	case MOD_UNLOAD:
111		live_entropy_source_deregister(&live_random_example);
112		break;
113
114	case MOD_SHUTDOWN:
115		break;
116
117	default:
118		error = EOPNOTSUPP;
119		break;
120	}
121
122	return (error);
123}
124
125DEV_MODULE(live_random_example, live_random_example_modevent, NULL);
126MODULE_VERSION(live_random_example, 1);
127MODULE_DEPEND(live_random_example, randomdev, 1, 1, 1);
128