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
48 static int read_random_phony(void *, int);
49
50 /* Structure holding the desired entropy sources */
51 struct harvest_select harvest = { 1, 1, 1, 1 };
52 static int warned = 0;
53
54 /* hold the address of the routine which is actually called if
55 * the randomdev is loaded
56 */
57 static void (*reap_func)(u_int64_t, const void *, u_int, u_int,
58 enum esource) = NULL;
59 static int (*read_func)(void *, int) = read_random_phony;
60
61 /* Initialise the harvester at load time */
62 void
randomdev_init_harvester(void (* reaper)(u_int64_t,const void *,u_int,u_int,enum esource),int (* reader)(void *,int))63 randomdev_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 */
71 void
randomdev_deinit_harvester(void)72 randomdev_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 */
88 void
random_harvest(void * entropy,u_int count,u_int bits,enum esource origin)89 random_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 */
96 int
read_random(void * buf,int count)97 read_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 */
106 static int
read_random_phony(void * buf,int count)107 read_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 */
135 void
random_set_wakeup_exit(void * control)136 random_set_wakeup_exit(void *control)
137 {
138 wakeup(control);
139 kproc_exit(0);
140 /* NOTREACHED */
141 }
142