random_adaptor_example.c revision 254784 
1/*-
2 * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer
10 *    in this position and unchanged.
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 ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 */
27
28#include <sys/cdefs.h>
29__FBSDID("$FreeBSD: projects/random_number_generator/share/examples/kld/random_adaptor/random_adaptor_example.c 254784 2013-08-24 13:54:56Z markm $");
30
31#include <sys/param.h>
32#include <sys/kernel.h>
33#include <sys/module.h>
34#include <sys/selinfo.h>
35#include <sys/systm.h>
36
37#include <dev/random/random_adaptors.h>
38#include <dev/random/randomdev.h>
39
40static int random_example_entropy_control;
41
42#define RNG_NAME "example"
43
44static int random_example_read(void *, int);
45static void random_example_init(void);
46
47struct random_adaptor random_example = {
48	.ident = "Example RNG",
49	.init = random_example_init,
50	.deinit = (random_deinit_func_t *)random_null_func,
51	.read = random_example_read,
52	.write = (random_write_func_t *)random_null_func,
53	.reseed = (random_reseed_func_t *)random_null_func,
54	.seeded = 1,
55};
56
57static void
58random_example_init(void)
59{
60
61	/*
62	 * Init() is called only if this RNG was chosen to plugin in to
63	 * random(4). In which case, we should no longer use this adaptor as
64	 * an entropy source.
65	 */
66	random_example_entropy_control = 1;
67}
68
69/*
70 * Used under the license provided @ http://xkcd.com/221/
71 * http://creativecommons.org/licenses/by-nc/2.5/
72 */
73static u_char
74getRandomNumber(void)
75{
76	return 4;   /* chosen by fair dice roll, guaranteed to be random */
77}
78
79static int
80random_example_read(void *buf, int c)
81{
82	u_char *b;
83	int count;
84
85	b = buf;
86
87	for (count = 0; count < c; count++) {
88		b[count] = getRandomNumber();
89	}
90
91	printf("returning %d bytes of pure randomness\n", c);
92	return (c);
93}
94
95static int
96random_example_modevent(module_t mod, int type, void *unused)
97{
98
99	switch (type) {
100	case MOD_LOAD:
101		/* start off by using this as an entropy source */
102		random_adaptor_use_as_entropy(RNG_NAME, &random_example,
103		    &random_example_entropy_control);
104		random_adaptor_register(RNG_NAME, &random_example);
105		EVENTHANDLER_INVOKE(random_adaptor_attach, &random_example);
106		return (0);
107	}
108
109	return (EINVAL);
110}
111
112RANDOM_ADAPTOR_MODULE(random_example, random_example_modevent, 1);
113