ffmpeg/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_CRYPTGENRANDOM
  30 #include <windows.h>
  31 #include <wincrypt.h>
  32 #endif
  33 #include <fcntl.h>
  34 #include <math.h>
  35 #include <time.h>
  36 #include <string.h>
  37 #include "avassert.h"
  38 #include "internal.h"
  39 #include "intreadwrite.h"
  40 #include "timer.h"
  41 #include "random_seed.h"
  42 #include "sha.h"
  43
  44 #ifndef TEST
  45 #define TEST 0
  46 #endif
  47
  48 static int read_random(uint32_t *dst, const char *file)
  49 {
  50 #if HAVE_UNISTD_H
  51     int fd = avpriv_open(file, O_RDONLY);
  52     int err = -1;
  53
  54     if (fd == -1)
  55         return -1;
  56     err = read(fd, dst, sizeof(*dst));
  57     close(fd);
  58
  59     return err;
  60 #else
  61     return -1;
  62 #endif
  63 }
  64
  65 static uint32_t get_generic_seed(void)
  66 {
  67     uint8_t tmp[120];
  68     struct AVSHA *sha = (void*)tmp;
  69     clock_t last_t  = 0;
  70     static uint64_t i = 0;
  71     static uint32_t buffer[512] = { 0 };
  72     unsigned char digest[20];
  73     uint64_t last_i = i;
  74
  75     av_assert0(sizeof(tmp) >= av_sha_size);
  76
  77     if(TEST){
  78         memset(buffer, 0, sizeof(buffer));
  79         last_i = i = 0;
  80     }else{
  81 #ifdef AV_READ_TIME
  82         buffer[13] ^= AV_READ_TIME();
  83         buffer[41] ^= AV_READ_TIME()>>32;
  84 #endif
  85     }
  86
  87     for (;;) {
  88         clock_t t = clock();
  89
  90         if (last_t == t) {
  91             buffer[i & 511]++;
  92         } else {
  93             buffer[++i & 511] += (t - last_t) % 3294638521U;
  94             if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i - last_i > 8)
  95                 break;
  96         }
  97         last_t = t;
  98     }
  99
 100     if(TEST)
 101         buffer[0] = buffer[1] = 0;
 102
 103     av_sha_init(sha, 160);
 104     av_sha_update(sha, (const uint8_t *)buffer, sizeof(buffer));
 105     av_sha_final(sha, digest);
 106     return AV_RB32(digest) + AV_RB32(digest + 16);
 107 }
 108
 109 uint32_t av_get_random_seed(void)
 110 {
 111     uint32_t seed;
 112
 113 #if HAVE_CRYPTGENRANDOM
 114     HCRYPTPROV provider;
 115     if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
 116                             CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
 117         BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
 118         CryptReleaseContext(provider, 0);
 119         if (ret)
 120             return seed;
 121     }
 122 #endif
 123
 124     if (read_random(&seed, "/dev/urandom") == sizeof(seed))
 125         return seed;
 126     if (read_random(&seed, "/dev/random")  == sizeof(seed))
 127         return seed;
 128     return get_generic_seed();
 129 }
 130
 131 #if TEST
 132 #undef printf
 133 #define N 256
 134 #include <stdio.h>
 135
 136 int main(void)
 137 {
 138     int i, j, retry;
 139     uint32_t seeds[N];
 140
 141     for (retry=0; retry<3; retry++){
 142         for (i=0; i<N; i++){
 143             seeds[i] = av_get_random_seed();
 144             for (j=0; j<i; j++)
 145                 if (seeds[j] == seeds[i])
 146                     goto retry;
 147         }
 148         printf("seeds OK\n");
 149         return 0;
 150         retry:;
 151     }
 152     printf("FAIL at %d with %X\n", j, seeds[j]);
 153     return 1;
 154 }
 155 #endif