crypto/libressl/crypto/compat/arc4random.c

   1 /*      $OpenBSD: arc4random.c,v 1.53 2015/09/10 18:53:50 bcook Exp $   */
   2
   3 /*
   4  * Copyright (c) 1996, David Mazieres <dm@uun.org>
   5  * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
   6  * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
   7  * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
   8  *
   9  * Permission to use, copy, modify, and distribute this software for any
  10  * purpose with or without fee is hereby granted, provided that the above
  11  * copyright notice and this permission notice appear in all copies.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  14  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  15  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  16  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  17  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  18  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  19  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  20  */
  21
  22 /*
  23  * ChaCha based random number generator for OpenBSD.
  24  */
  25
  26 #include <fcntl.h>
  27 #include <limits.h>
  28 #include <signal.h>
  29 #include <stdint.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <unistd.h>
  33 #include <sys/types.h>
  34 #include <sys/time.h>
  35
  36 #define KEYSTREAM_ONLY
  37 #include "chacha_private.h"
  38
  39 #define minimum(a, b) ((a) < (b) ? (a) : (b))
  40
  41 #if defined(__GNUC__) || defined(_MSC_VER)
  42 #define inline __inline
  43 #else                           /* __GNUC__ || _MSC_VER */
  44 #define inline
  45 #endif                          /* !__GNUC__ && !_MSC_VER */
  46
  47 #define KEYSZ   32
  48 #define IVSZ    8
  49 #define BLOCKSZ 64
  50 #define RSBUFSZ (16*BLOCKSZ)
  51
  52 /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */
  53 static struct _rs {
  54         size_t          rs_have;        /* valid bytes at end of rs_buf */
  55         size_t          rs_count;       /* bytes till reseed */
  56 } *rs;
  57
  58 /* Maybe be preserved in fork children, if _rs_allocate() decides. */
  59 static struct _rsx {
  60         chacha_ctx      rs_chacha;      /* chacha context for random keystream */
  61         u_char          rs_buf[RSBUFSZ];        /* keystream blocks */
  62 } *rsx;
  63
  64 static inline int _rs_allocate(struct _rs **, struct _rsx **);
  65 static inline void _rs_forkdetect(void);
  66 #include "arc4random.h"
  67
  68 static inline void _rs_rekey(u_char *dat, size_t datlen);
  69
  70 static inline void
  71 _rs_init(u_char *buf, size_t n)
  72 {
  73         if (n < KEYSZ + IVSZ)
  74                 return;
  75
  76         if (rs == NULL) {
  77                 if (_rs_allocate(&rs, &rsx) == -1)
  78                         abort();
  79         }
  80
  81         chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
  82         chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
  83 }
  84
  85 static void
  86 _rs_stir(void)
  87 {
  88         u_char rnd[KEYSZ + IVSZ];
  89
  90         if (getentropy(rnd, sizeof rnd) == -1)
  91                 _getentropy_fail();
  92
  93         if (!rs)
  94                 _rs_init(rnd, sizeof(rnd));
  95         else
  96                 _rs_rekey(rnd, sizeof(rnd));
  97         explicit_bzero(rnd, sizeof(rnd));       /* discard source seed */
  98
  99         /* invalidate rs_buf */
 100         rs->rs_have = 0;
 101         memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
 102
 103         rs->rs_count = 1600000;
 104 }
 105
 106 static inline void
 107 _rs_stir_if_needed(size_t len)
 108 {
 109         _rs_forkdetect();
 110         if (!rs || rs->rs_count <= len)
 111                 _rs_stir();
 112         if (rs->rs_count <= len)
 113                 rs->rs_count = 0;
 114         else
 115                 rs->rs_count -= len;
 116 }
 117
 118 static inline void
 119 _rs_rekey(u_char *dat, size_t datlen)
 120 {
 121 #ifndef KEYSTREAM_ONLY
 122         memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
 123 #endif
 124         /* fill rs_buf with the keystream */
 125         chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
 126             rsx->rs_buf, sizeof(rsx->rs_buf));
 127         /* mix in optional user provided data */
 128         if (dat) {
 129                 size_t i, m;
 130
 131                 m = minimum(datlen, KEYSZ + IVSZ);
 132                 for (i = 0; i < m; i++)
 133                         rsx->rs_buf[i] ^= dat[i];
 134         }
 135         /* immediately reinit for backtracking resistance */
 136         _rs_init(rsx->rs_buf, KEYSZ + IVSZ);
 137         memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
 138         rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
 139 }
 140
 141 static inline void
 142 _rs_random_buf(void *_buf, size_t n)
 143 {
 144         u_char *buf = (u_char *)_buf;
 145         u_char *keystream;
 146         size_t m;
 147
 148         _rs_stir_if_needed(n);
 149         while (n > 0) {
 150                 if (rs->rs_have > 0) {
 151                         m = minimum(n, rs->rs_have);
 152                         keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
 153                             - rs->rs_have;
 154                         memcpy(buf, keystream, m);
 155                         memset(keystream, 0, m);
 156                         buf += m;
 157                         n -= m;
 158                         rs->rs_have -= m;
 159                 }
 160                 if (rs->rs_have == 0)
 161                         _rs_rekey(NULL, 0);
 162         }
 163 }
 164
 165 static inline void
 166 _rs_random_u32(uint32_t *val)
 167 {
 168         u_char *keystream;
 169
 170         _rs_stir_if_needed(sizeof(*val));
 171         if (rs->rs_have < sizeof(*val))
 172                 _rs_rekey(NULL, 0);
 173         keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
 174         memcpy(val, keystream, sizeof(*val));
 175         memset(keystream, 0, sizeof(*val));
 176         rs->rs_have -= sizeof(*val);
 177 }
 178
 179 uint32_t
 180 arc4random(void)
 181 {
 182         uint32_t val;
 183
 184         _ARC4_LOCK();
 185         _rs_random_u32(&val);
 186         _ARC4_UNLOCK();
 187         return val;
 188 }
 189
 190 void
 191 arc4random_buf(void *buf, size_t n)
 192 {
 193         _ARC4_LOCK();
 194         _rs_random_buf(buf, n);
 195         _ARC4_UNLOCK();
 196 }