1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2013 Arthur Mesh <[email protected]>
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
45 static void live_random_example_init(void);
46 static void live_random_example_deinit(void);
47 static u_int live_random_example_read(void *, u_int);
48
49 struct 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 */
60 static uint8_t
getRandomNumber(void)61 getRandomNumber(void)
62 {
63 return 4; /* chosen by fair dice roll, guaranteed to be random */
64 }
65
66 static void
live_random_example_init(void)67 live_random_example_init(void)
68 {
69
70 /* Do initialisation stuff here */
71 }
72
73 static void
live_random_example_deinit(void)74 live_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 */
84 static u_int
live_random_example_read(void * buf,u_int c)85 live_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 */
100 static int
live_random_example_modevent(module_t mod __unused,int type,void * unused __unused)101 live_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
125 DEV_MODULE(live_random_example, live_random_example_modevent, NULL);
126 MODULE_VERSION(live_random_example, 1);
127 MODULE_DEPEND(live_random_example, randomdev, 1, 1, 1);
128