1/*-
2 * Copyright (c) 2000-2013 Mark R V Murray
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("$FreeBSD$");
30
31#include <sys/param.h>
32#include <sys/kthread.h>
33#include <sys/lock.h>
34#include <sys/malloc.h>
35#include <sys/mutex.h>
36#include <sys/poll.h>
37#include <sys/queue.h>
38#include <sys/random.h>
39#include <sys/selinfo.h>
40#include <sys/syslog.h>
41#include <sys/systm.h>
42#include <sys/sysctl.h>
43
44#include <machine/cpu.h>
45
46#include <dev/random/randomdev_soft.h>
47
48static int read_random_phony(void *, int);
49
50/* Structure holding the desired entropy sources */
51struct harvest_select harvest = { 1, 1, 1, 1 };
52static int warned = 0;
53
54/* hold the address of the routine which is actually called if
55 * the randomdev is loaded
56 */
57static void (*reap_func)(u_int64_t, const void *, u_int, u_int,
58    enum esource) = NULL;
59static int (*read_func)(void *, int) = read_random_phony;
60
61/* Initialise the harvester at load time */
62void
63randomdev_init_harvester(void (*reaper)(u_int64_t, const void *, u_int,
64    u_int, enum esource), int (*reader)(void *, int))
65{
66	reap_func = reaper;
67	read_func = reader;
68}
69
70/* Deinitialise the harvester at unload time */
71void
72randomdev_deinit_harvester(void)
73{
74	reap_func = NULL;
75	read_func = read_random_phony;
76	warned = 0;
77}
78
79/* Entropy harvesting routine. This is supposed to be fast; do
80 * not do anything slow in here!
81 * Implemented as in indirect call to allow non-inclusion of
82 * the entropy device.
83 *
84 * XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle
85 * counters are built in, but on older hardware it will do a real time clock
86 * read which can be quite expensive.
87 */
88void
89random_harvest(void *entropy, u_int count, u_int bits, enum esource origin)
90{
91	if (reap_func)
92		(*reap_func)(get_cyclecount(), entropy, count, bits, origin);
93}
94
95/* Userland-visible version of read_random */
96int
97read_random(void *buf, int count)
98{
99	return ((*read_func)(buf, count));
100}
101
102/* If the entropy device is not loaded, make a token effort to
103 * provide _some_ kind of randomness. This should only be used
104 * inside other RNG's, like arc4random(9).
105 */
106static int
107read_random_phony(void *buf, int count)
108{
109	u_long randval;
110	int size, i;
111
112	if (!warned) {
113		log(LOG_WARNING, "random device not loaded; using insecure entropy\n");
114		warned = 1;
115	}
116
117	/* srandom() is called in kern/init_main.c:proc0_post() */
118
119	/* Fill buf[] with random(9) output */
120	for (i = 0; i < count; i+= (int)sizeof(u_long)) {
121		randval = random();
122		size = MIN(count - i, sizeof(u_long));
123		memcpy(&((char *)buf)[i], &randval, (size_t)size);
124	}
125
126	return (count);
127}
128
129/* Helper routine to enable kproc_exit() to work while the module is
130 * being (or has been) unloaded.
131 * This routine is in this file because it is always linked into the kernel,
132 * and will thus never be unloaded. This is critical for unloadable modules
133 * that have threads.
134 */
135void
136random_set_wakeup_exit(void *control)
137{
138	wakeup(control);
139	kproc_exit(0);
140	/* NOTREACHED */
141}
142