libavutil/random_seed.c

   1 /*
   2  * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "config.h"
  22
  23 #if HAVE_UNISTD_H
  24 #include <unistd.h>
  25 #endif
  26 #if HAVE_IO_H
  27 #include <io.h>
  28 #endif
  29 #if HAVE_BCRYPT
  30 #include <windows.h>
  31 #include <bcrypt.h>
  32 #endif
  33 #if CONFIG_GCRYPT
  34 #include <gcrypt.h>
  35 #elif CONFIG_OPENSSL
  36 #include <openssl/rand.h>
  37 #endif
  38 #include <fcntl.h>
  39 #include <math.h>
  40 #include <time.h>
  41 #include <string.h>
  42 #include "avassert.h"
  43 #include "file_open.h"
  44 #include "internal.h"
  45 #include "intreadwrite.h"
  46 #include "timer.h"
  47 #include "random_seed.h"
  48 #include "sha.h"
  49
  50 #ifndef TEST
  51 #define TEST 0
  52 #endif
  53
  54 static int read_random(uint8_t *dst, size_t len, const char *file)
  55 {
  56 #if HAVE_UNISTD_H
  57     FILE *fp = avpriv_fopen_utf8(file, "r");
  58     size_t err;
  59
  60     if (!fp)
  61         return AVERROR_UNKNOWN;
  62     setvbuf(fp, NULL, _IONBF, 0);
  63     err = fread(dst, 1, len, fp);
  64     fclose(fp);
  65
  66     if (err != len)
  67         return AVERROR_UNKNOWN;
  68
  69     return 0;
  70 #else
  71     return AVERROR(ENOSYS);
  72 #endif
  73 }
  74
  75 static uint32_t get_generic_seed(void)
  76 {
  77     uint64_t tmp[120/8];
  78     struct AVSHA *sha = (void*)tmp;
  79     clock_t last_t  = 0;
  80     clock_t last_td = 0;
  81     clock_t init_t = 0;
  82     static uint64_t i = 0;
  83     static uint32_t buffer[512] = { 0 };
  84     unsigned char digest[20];
  85     uint64_t last_i = i;
  86     int repeats[3] = { 0 };
  87
  88     av_assert0(sizeof(tmp) >= av_sha_size);
  89
  90     if(TEST){
  91         memset(buffer, 0, sizeof(buffer));
  92         last_i = i = 0;
  93     }else{
  94 #ifdef AV_READ_TIME
  95         buffer[13] ^= AV_READ_TIME();
  96         buffer[41] ^= AV_READ_TIME()>>32;
  97 #endif
  98     }
  99
 100     for (;;) {
 101         clock_t t = clock();
 102         int incremented_i = 0;
 103         int cur_td = t - last_t;
 104         if (last_t + 2*last_td + (CLOCKS_PER_SEC > 1000) < t) {
 105             // If the timer incremented by more than 2*last_td at once,
 106             // we may e.g. have had a context switch. If the timer resolution
 107             // is high (CLOCKS_PER_SEC > 1000), require that the timer
 108             // incremented by more than 1. If the timer resolution is low,
 109             // it is enough that the timer incremented at all.
 110             buffer[++i & 511] += cur_td % 3294638521U;
 111             incremented_i = 1;
 112         } else if (t != last_t && repeats[0] > 0 && repeats[1] > 0 &&
 113                    repeats[2] > 0 && repeats[0] != repeats[1] &&
 114                    repeats[0] != repeats[2]) {
 115             // If the timer resolution is high, and we get the same timer
 116             // value multiple times, use variances in the number of repeats
 117             // of each timer value as entropy. If we get a different number of
 118             // repeats than the last two unique cases, count that as entropy
 119             // and proceed to the next index.
 120             buffer[++i & 511] += (repeats[0] + repeats[1] + repeats[2]) % 3294638521U;
 121             incremented_i = 1;
 122         } else {
 123             buffer[i & 511] = 1664525*buffer[i & 511] + 1013904223 + (cur_td % 3294638521U);
 124         }
 125         if (incremented_i && (t - init_t) >= CLOCKS_PER_SEC>>5) {
 126             if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i - last_i > 8)
 127                 break;
 128         }
 129         if (t == last_t) {
 130             repeats[0]++;
 131         } else {
 132             // If we got a new unique number of repeats, update the history.
 133             if (repeats[0] != repeats[1]) {
 134                 repeats[2] = repeats[1];
 135                 repeats[1] = repeats[0];
 136             }
 137             repeats[0] = 0;
 138         }
 139         last_t = t;
 140         last_td = cur_td;
 141         if (!init_t)
 142             init_t = t;
 143     }
 144
 145     if(TEST) {
 146         buffer[0] = buffer[1] = 0;
 147     } else {
 148 #ifdef AV_READ_TIME
 149         buffer[111] += AV_READ_TIME();
 150 #endif
 151     }
 152
 153     av_sha_init(sha, 160);
 154     av_sha_update(sha, (const uint8_t *)buffer, sizeof(buffer));
 155     av_sha_final(sha, digest);
 156     return AV_RB32(digest) + AV_RB32(digest + 16);
 157 }
 158
 159 int av_random_bytes(uint8_t* buf, size_t len)
 160 {
 161     int err;
 162
 163 #if HAVE_BCRYPT
 164     BCRYPT_ALG_HANDLE algo_handle;
 165     NTSTATUS ret = BCryptOpenAlgorithmProvider(&algo_handle, BCRYPT_RNG_ALGORITHM,
 166                                                MS_PRIMITIVE_PROVIDER, 0);
 167     if (BCRYPT_SUCCESS(ret)) {
 168         NTSTATUS ret = BCryptGenRandom(algo_handle, (PUCHAR)buf, len, 0);
 169         BCryptCloseAlgorithmProvider(algo_handle, 0);
 170         if (BCRYPT_SUCCESS(ret))
 171             return 0;
 172     }
 173 #endif
 174
 175 #if HAVE_ARC4RANDOM_BUF
 176     arc4random_buf(buf, len);
 177     return 0;
 178 #endif
 179
 180     err = read_random(buf, len, "/dev/urandom");
 181     if (!err)
 182         return err;
 183
 184 #if CONFIG_GCRYPT
 185     gcry_randomize(buf, len, GCRY_VERY_STRONG_RANDOM);
 186     return 0;
 187 #elif CONFIG_OPENSSL
 188     if (RAND_bytes(buf, len) == 1)
 189         return 0;
 190     return AVERROR_EXTERNAL;
 191 #else
 192     return err;
 193 #endif
 194 }
 195
 196 uint32_t av_get_random_seed(void)
 197 {
 198     uint32_t seed;
 199
 200     if (av_random_bytes((uint8_t *)&seed, sizeof(seed)) < 0)
 201         return get_generic_seed();
 202
 203     return seed;
 204 }