sys/dev/random/random_adaptors.c

   1 /*-
   2  * Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
   3  * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
   4  * Copyright (c) 2013 Mark R V Murray
   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 #include <sys/param.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include <sys/systm.h>
  33 #include <sys/kernel.h>
  34 #include <sys/kthread.h>
  35 #include <sys/libkern.h>
  36 #include <sys/lock.h>
  37 #include <sys/malloc.h>
  38 #include <sys/queue.h>
  39 #include <sys/random.h>
  40 #include <sys/selinfo.h>
  41 #include <sys/sx.h>
  42 #include <sys/sysctl.h>
  43 #include <sys/unistd.h>
  44
  45 #include <dev/random/randomdev.h>
  46 #include <dev/random/randomdev_soft.h>
  47 #include <dev/random/random_adaptors.h>
  48
  49 LIST_HEAD(adaptors_head, random_adaptors);
  50 static struct adaptors_head adaptors = LIST_HEAD_INITIALIZER(adaptors);
  51 static struct sx adaptors_lock; /* need a sleepable lock */
  52
  53 /* List for the dynamic sysctls */
  54 static struct sysctl_ctx_list random_clist;
  55
  56 struct random_adaptor *random_adaptor;
  57
  58 MALLOC_DEFINE(M_ENTROPY, "entropy", "Entropy harvesting buffers and data structures");
  59
  60 int
  61 random_adaptor_register(const char *name, struct random_adaptor *rsp)
  62 {
  63         struct random_adaptors *rpp;
  64
  65         KASSERT(name != NULL && rsp != NULL, ("invalid input to %s", __func__));
  66
  67         rpp = malloc(sizeof(struct random_adaptors), M_ENTROPY, M_WAITOK);
  68         rpp->name = name;
  69         rpp->rsp = rsp;
  70
  71         sx_xlock(&adaptors_lock);
  72         LIST_INSERT_HEAD(&adaptors, rpp, entries);
  73         sx_xunlock(&adaptors_lock);
  74
  75         return (0);
  76 }
  77
  78 struct random_adaptor *
  79 random_adaptor_get(const char *name)
  80 {
  81         struct random_adaptors  *rpp;
  82         struct random_adaptor   *rsp;
  83
  84         rsp = NULL;
  85
  86         sx_slock(&adaptors_lock);
  87
  88         LIST_FOREACH(rpp, &adaptors, entries)
  89                 if (strcmp(rpp->name, name) == 0)
  90                         rsp = rpp->rsp;
  91
  92         sx_sunlock(&adaptors_lock);
  93
  94         return (rsp);
  95 }
  96
  97 /*
  98  * Walk a list of registered random(4) adaptors and pick the last non-selected
  99  * one.
 100  *
 101  * If none are selected, use yarrow if available.
 102  */
 103 void
 104 random_adaptor_choose(struct random_adaptor **adaptor)
 105 {
 106         char                     rngs[128], *token, *cp;
 107         struct random_adaptors  *rppi, *ramax;
 108         unsigned                 primax;
 109
 110         KASSERT(adaptor != NULL, ("pre-conditions failed"));
 111
 112         *adaptor = NULL;
 113         if (TUNABLE_STR_FETCH("kern.random.active_adaptor", rngs, sizeof(rngs))) {
 114                 cp = rngs;
 115
 116                 while ((token = strsep(&cp, ",")) != NULL)
 117                         if ((*adaptor = random_adaptor_get(token)) != NULL)
 118                                 break;
 119                         else if (bootverbose)
 120                                 printf("%s random adaptor is not available,"
 121                                     " skipping\n", token);
 122         }
 123
 124         primax = 0U;
 125         if (*adaptor == NULL) {
 126                 /*
 127                  * Fall back to the highest priority item on the available
 128                  * RNG list.
 129                  */
 130                 sx_slock(&adaptors_lock);
 131
 132                 ramax = NULL;
 133                 LIST_FOREACH(rppi, &adaptors, entries) {
 134                         if (rppi->rsp->priority >= primax) {
 135                                 ramax = rppi;
 136                                 primax = rppi->rsp->priority;
 137                         }
 138                 }
 139                 if (ramax != NULL)
 140                         *adaptor = ramax->rsp;
 141
 142                 sx_sunlock(&adaptors_lock);
 143
 144                 if (bootverbose && *adaptor)
 145                         printf("Falling back to <%s> random adaptor\n",
 146                             (*adaptor)->ident);
 147         }
 148 }
 149
 150 static void
 151 random_adaptors_deinit(void *unused)
 152 {
 153
 154         sx_destroy(&adaptors_lock);
 155         sysctl_ctx_free(&random_clist);
 156 }
 157
 158 static int
 159 random_sysctl_adaptors_handler(SYSCTL_HANDLER_ARGS)
 160 {
 161         struct random_adaptors  *rpp;
 162         int error, count;
 163
 164         count = error = 0;
 165
 166         sx_slock(&adaptors_lock);
 167
 168         if (LIST_EMPTY(&adaptors))
 169                 error = SYSCTL_OUT(req, "", 0);
 170         else {
 171                 LIST_FOREACH(rpp, &adaptors, entries) {
 172
 173                         error = SYSCTL_OUT(req, ",", count++ ? 1 : 0);
 174                         if (error)
 175                                 break;
 176
 177                         error = SYSCTL_OUT(req, rpp->name, strlen(rpp->name));
 178                         if (error)
 179                                 break;
 180                 }
 181         }
 182
 183         sx_sunlock(&adaptors_lock);
 184
 185         return (error);
 186 }
 187
 188 static int
 189 random_sysctl_active_adaptor_handler(SYSCTL_HANDLER_ARGS)
 190 {
 191         struct random_adaptor   *rsp;
 192         struct random_adaptors  *rpp;
 193         const char              *name;
 194         int error;
 195
 196         name = NULL;
 197         rsp = random_adaptor;
 198
 199         if (rsp != NULL) {
 200                 sx_slock(&adaptors_lock);
 201
 202                 LIST_FOREACH(rpp, &adaptors, entries)
 203                         if (rpp->rsp == rsp)
 204                                 name = rpp->name;
 205
 206                 sx_sunlock(&adaptors_lock);
 207         }
 208
 209         if (rsp == NULL || name == NULL)
 210                 error = SYSCTL_OUT(req, "", 0);
 211         else
 212                 error = SYSCTL_OUT(req, name, strlen(name));
 213
 214         return (error);
 215 }
 216
 217 static void
 218 random_adaptors_init(void *unused)
 219 {
 220
 221         SYSCTL_PROC(_kern_random, OID_AUTO, adaptors,
 222             CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
 223             NULL, 0, random_sysctl_adaptors_handler, "",
 224             "Random Number Generator adaptors");
 225
 226         SYSCTL_PROC(_kern_random, OID_AUTO, active_adaptor,
 227             CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
 228             NULL, 0, random_sysctl_active_adaptor_handler, "",
 229             "Active Random Number Generator Adaptor");
 230
 231         sx_init(&adaptors_lock, "random_adaptors");
 232 }
 233
 234 SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW, 0, "Random Number Generator");
 235
 236 SYSINIT(random_adaptors, SI_SUB_DRIVERS, SI_ORDER_FIRST, random_adaptors_init,
 237     NULL);
 238 SYSUNINIT(random_adaptors, SI_SUB_DRIVERS, SI_ORDER_FIRST,
 239     random_adaptors_deinit, NULL);
 240
 241 static void
 242 random_adaptors_reseed(void *unused)
 243 {
 244
 245         (void)unused;
 246         if (random_adaptor != NULL)
 247                 (*random_adaptor->reseed)();
 248         arc4rand(NULL, 0, 1);
 249 }
 250 SYSINIT(random_reseed, SI_SUB_INTRINSIC_POST, SI_ORDER_SECOND,
 251     random_adaptors_reseed, NULL);