arc4random.c

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    1 /*-
    2  * Copyright (c) 2017 The FreeBSD Foundation
    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/types.h>
   32 #include <sys/param.h>
   33 #include <sys/kernel.h>
   34 #include <sys/libkern.h>
   35 #include <sys/linker.h>
   36 #include <sys/lock.h>
   37 #include <sys/malloc.h>
   38 #include <sys/mutex.h>
   39 #include <sys/random.h>
   40 #include <sys/smp.h>
   41 #include <sys/time.h>
   42 
   43 #include <machine/cpu.h>
   44 
   45 #include <crypto/chacha20/chacha.h>
   46 #include <crypto/sha2/sha256.h>
   47 #include <dev/random/randomdev.h>
   48 #ifdef RANDOM_FENESTRASX
   49 #include <dev/random/fenestrasX/fx_pub.h>
   50 #endif
   51 
   52 #define CHACHA20_RESEED_BYTES   65536
   53 #define CHACHA20_RESEED_SECONDS 300
   54 #define CHACHA20_KEYBYTES       32
   55 #define CHACHA20_BUFFER_SIZE    64
   56 
   57 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
   58 
   59 #ifndef RANDOM_FENESTRASX
   60 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
   61 #endif
   62 
   63 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
   64 
   65 struct chacha20_s {
   66         struct mtx mtx;
   67         int numbytes;
   68         time_t t_reseed;
   69         u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
   70         struct chacha_ctx ctx;
   71 #ifdef RANDOM_FENESTRASX
   72         uint64_t seed_version;
   73 #endif
   74 } __aligned(CACHE_LINE_SIZE);
   75 
   76 static struct chacha20_s *chacha20inst = NULL;
   77 
   78 #define CHACHA20_FOREACH(_chacha20) \
   79         for (_chacha20 = &chacha20inst[0]; \
   80              _chacha20 <= &chacha20inst[mp_maxid]; \
   81              _chacha20++)
   82 
   83 /*
   84  * Mix up the current context.
   85  */
   86 static void
   87 chacha20_randomstir(struct chacha20_s *chacha20)
   88 {
   89         struct timeval tv_now;
   90         u_int8_t key[CHACHA20_KEYBYTES];
   91 #ifdef RANDOM_FENESTRASX
   92         uint64_t seed_version;
   93 
   94 #else
   95         if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) {
   96                 SHA256_CTX ctx;
   97                 uint64_t cc;
   98                 uint32_t fver;
   99 
  100                 if (!arc4random_bypassed_before_seeding) {
  101                         arc4random_bypassed_before_seeding = true;
  102                         if (!random_bypass_disable_warnings)
  103                                 printf("arc4random: WARNING: initial seeding "
  104                                     "bypassed the cryptographic random device "
  105                                     "because it was not yet seeded and the "
  106                                     "knob 'bypass_before_seeding' was "
  107                                     "enabled.\n");
  108                 }
  109 
  110                 /* Last ditch effort to inject something in a bad condition. */
  111                 cc = get_cyclecount();
  112                 SHA256_Init(&ctx);
  113                 SHA256_Update(&ctx, key, sizeof(key));
  114                 SHA256_Update(&ctx, &cc, sizeof(cc));
  115                 fver = __FreeBSD_version;
  116                 SHA256_Update(&ctx, &fver, sizeof(fver));
  117                 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH,
  118                     "make sure 256 bits is still 256 bits");
  119                 SHA256_Final(key, &ctx);
  120         } else {
  121 #endif
  122 #ifdef RANDOM_FENESTRASX
  123                 read_random_key(key, CHACHA20_KEYBYTES, &seed_version);
  124 #else
  125                 /*
  126                 * If the loader(8) did not have an entropy stash from the
  127                 * previous shutdown to load, then we will block.  The answer is
  128                 * to make sure there is an entropy stash at shutdown time.
  129                 *
  130                 * On the other hand, if the random_bypass_before_seeding knob
  131                 * was set and we landed in this branch, we know this won't
  132                 * block because we know the random device is seeded.
  133                 */
  134                 read_random(key, CHACHA20_KEYBYTES);
  135         }
  136 #endif
  137         getmicrouptime(&tv_now);
  138         mtx_lock(&chacha20->mtx);
  139         chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
  140         chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
  141         /* Reset for next reseed cycle. */
  142         chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
  143         chacha20->numbytes = 0;
  144 #ifdef RANDOM_FENESTRASX
  145         chacha20->seed_version = seed_version;
  146 #endif
  147         mtx_unlock(&chacha20->mtx);
  148 }
  149 
  150 /*
  151  * Initialize the contexts.
  152  */
  153 static void
  154 chacha20_init(void)
  155 {
  156         struct chacha20_s *chacha20;
  157 
  158         chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
  159                         M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
  160         KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
  161 
  162         CHACHA20_FOREACH(chacha20) {
  163                 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
  164                 chacha20->t_reseed = -1;
  165                 chacha20->numbytes = 0;
  166                 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
  167                 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
  168         }
  169 }
  170 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
  171 
  172 
  173 static void
  174 chacha20_uninit(void)
  175 {
  176         struct chacha20_s *chacha20;
  177 
  178         CHACHA20_FOREACH(chacha20)
  179                 mtx_destroy(&chacha20->mtx);
  180         free(chacha20inst, M_CHACHA20RANDOM);
  181 }
  182 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
  183 
  184 
  185 /*
  186  * MPSAFE
  187  */
  188 void
  189 arc4rand(void *ptr, u_int len, int reseed)
  190 {
  191         struct chacha20_s *chacha20;
  192         struct timeval tv;
  193         u_int length;
  194         u_int8_t *p;
  195 
  196 #ifdef RANDOM_FENESTRASX
  197         if (__predict_false(reseed))
  198 #else
  199         if (__predict_false(reseed ||
  200             (arc4rand_iniseed_state == ARC4_ENTR_HAVE &&
  201             atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))))
  202 #endif
  203                 CHACHA20_FOREACH(chacha20)
  204                         chacha20_randomstir(chacha20);
  205 
  206         getmicrouptime(&tv);
  207         chacha20 = &chacha20inst[curcpu];
  208         /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
  209         if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
  210                 chacha20_randomstir(chacha20);
  211 
  212         mtx_lock(&chacha20->mtx);
  213 #ifdef RANDOM_FENESTRASX
  214         if (__predict_false(
  215             atomic_load_acq_64(&fxrng_root_generation) != chacha20->seed_version
  216             )) {
  217                 mtx_unlock(&chacha20->mtx);
  218                 chacha20_randomstir(chacha20);
  219                 mtx_lock(&chacha20->mtx);
  220         }
  221 #endif
  222 
  223         p = ptr;
  224         while (len) {
  225                 length = MIN(CHACHA20_BUFFER_SIZE, len);
  226                 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
  227                 p += length;
  228                 len -= length;
  229                 chacha20->numbytes += length;
  230                 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
  231                         mtx_unlock(&chacha20->mtx);
  232                         chacha20_randomstir(chacha20);
  233                         mtx_lock(&chacha20->mtx);
  234                 }
  235         }
  236         mtx_unlock(&chacha20->mtx);
  237 }
  238 
  239 uint32_t
  240 arc4random(void)
  241 {
  242         uint32_t ret;
  243 
  244         arc4rand(&ret, sizeof(ret), 0);
  245         return ret;
  246 }
  247 
  248 void
  249 arc4random_buf(void *ptr, size_t len)
  250 {
  251 
  252         arc4rand(ptr, len, 0);
  253 }

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FreeBSD/Linux Kernel Cross Reference sys/libkern/arc4random.c

FreeBSD/Linux Kernel Cross Reference
sys/libkern/arc4random.c