libevent/evutil_rand.c

   1 /*
   2  * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The name of the author may not be used to endorse or promote products
  13  *    derived from this software without specific prior written permission.
  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 /* This file has our secure PRNG code.  On platforms that have arc4random(),
  28  * we just use that.  Otherwise, we include arc4random.c as a bunch of static
  29  * functions, and wrap it lightly.  We don't expose the arc4random*() APIs
  30  * because A) they aren't in our namespace, and B) it's not nice to name your
  31  * APIs after their implementations.  We keep them in a separate file
  32  * so that other people can rip it out and use it for whatever.
  33  */
  34
  35 #include "event2/event-config.h"
  36
  37 #include <limits.h>
  38
  39 #include "util-internal.h"
  40 #include "evthread-internal.h"
  41
  42 #ifdef _EVENT_HAVE_ARC4RANDOM
  43 #include <stdlib.h>
  44 #include <string.h>
  45 int
  46 evutil_secure_rng_init(void)
  47 {
  48         /* call arc4random() now to force it to self-initialize */
  49         (void) arc4random();
  50         return 0;
  51 }
  52 int
  53 evutil_secure_rng_global_setup_locks_(const int enable_locks)
  54 {
  55         return 0;
  56 }
  57
  58 static void
  59 ev_arc4random_buf(void *buf, size_t n)
  60 {
  61 #ifdef _EVENT_HAVE_ARC4RANDOM_BUF
  62         return arc4random_buf(buf, n);
  63 #else
  64         unsigned char *b = buf;
  65         /* Make sure that we start out with b at a 4-byte alignment; plenty
  66          * of CPUs care about this for 32-bit access. */
  67         if (n >= 4 && ((ev_uintptr_t)b) & 3) {
  68                 ev_uint32_t u = arc4random();
  69                 int n_bytes = 4 - (((ev_uintptr_t)b) & 3);
  70                 memcpy(b, &u, n_bytes);
  71                 b += n_bytes;
  72                 n -= n_bytes;
  73         }
  74         while (n >= 4) {
  75                 *(ev_uint32_t*)b = arc4random();
  76                 b += 4;
  77                 n -= 4;
  78         }
  79         if (n) {
  80                 ev_uint32_t u = arc4random();
  81                 memcpy(b, &u, n);
  82         }
  83 #endif
  84 }
  85
  86 #else /* !_EVENT_HAVE_ARC4RANDOM { */
  87
  88 #ifdef _EVENT_ssize_t
  89 #define ssize_t _EVENT_SSIZE_t
  90 #endif
  91 #define ARC4RANDOM_EXPORT static
  92 #define _ARC4_LOCK() EVLOCK_LOCK(arc4rand_lock, 0)
  93 #define _ARC4_UNLOCK() EVLOCK_UNLOCK(arc4rand_lock, 0)
  94 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
  95 static void *arc4rand_lock;
  96 #endif
  97
  98 #define ARC4RANDOM_UINT32 ev_uint32_t
  99 #define ARC4RANDOM_NOSTIR
 100 #define ARC4RANDOM_NORANDOM
 101 #define ARC4RANDOM_NOUNIFORM
 102
 103 #include "./arc4random.c"
 104
 105 #ifndef _EVENT_DISABLE_THREAD_SUPPORT
 106 int
 107 evutil_secure_rng_global_setup_locks_(const int enable_locks)
 108 {
 109         EVTHREAD_SETUP_GLOBAL_LOCK(arc4rand_lock, 0);
 110         return 0;
 111 }
 112 #endif
 113
 114 int
 115 evutil_secure_rng_init(void)
 116 {
 117         int val;
 118
 119         _ARC4_LOCK();
 120         if (!arc4_seeded_ok)
 121                 arc4_stir();
 122         val = arc4_seeded_ok ? 0 : -1;
 123         _ARC4_UNLOCK();
 124         return val;
 125 }
 126
 127 static void
 128 ev_arc4random_buf(void *buf, size_t n)
 129 {
 130         arc4random_buf(buf, n);
 131 }
 132
 133 #endif /* } !_EVENT_HAVE_ARC4RANDOM */
 134
 135 void
 136 evutil_secure_rng_get_bytes(void *buf, size_t n)
 137 {
 138         ev_arc4random_buf(buf, n);
 139 }
 140
 141 void
 142 evutil_secure_rng_add_bytes(const char *buf, size_t n)
 143 {
 144         arc4random_addrandom((unsigned char*)buf,
 145             n>(size_t)INT_MAX ? INT_MAX : (int)n);
 146 }
 147