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  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. #define HAVE_CRYPTGENRANDOM 0
  24.  
  25. #if HAVE_UNISTD_H
  26. #include <unistd.h>
  27. #endif
  28. #if HAVE_CRYPTGENRANDOM
  29. #include <windows.h>
  30. #include <wincrypt.h>
  31. #endif
  32. #include <fcntl.h>
  33. #include <math.h>
  34. #include <time.h>
  35. #include <string.h>
  36. #include "avassert.h"
  37. #include "internal.h"
  38. #include "timer.h"
  39. #include "random_seed.h"
  40. #include "sha.h"
  41. #include "intreadwrite.h"
  42.  
  43. #ifndef TEST
  44. #define TEST 0
  45. #endif
  46.  
  47. static int read_random(uint32_t *dst, const char *file)
  48. {
  49. #if HAVE_UNISTD_H
  50.     int fd = avpriv_open(file, O_RDONLY);
  51.     int err = -1;
  52.  
  53.     if (fd == -1)
  54.         return -1;
  55.     err = read(fd, dst, sizeof(*dst));
  56.     close(fd);
  57.  
  58.     return err;
  59. #else
  60.     return -1;
  61. #endif
  62. }
  63.  
  64. static uint32_t get_generic_seed(void)
  65. {
  66.     uint8_t tmp[120];
  67.     struct AVSHA *sha = (void*)tmp;
  68.     clock_t last_t  = 0;
  69.     static uint64_t i = 0;
  70.     static uint32_t buffer[512] = {0};
  71.     unsigned char digest[20];
  72.     uint64_t last_i = i;
  73.  
  74.     av_assert0(sizeof(tmp) >= av_sha_size);
  75.  
  76.     if(TEST){
  77.         memset(buffer, 0, sizeof(buffer));
  78.         last_i = i = 0;
  79.     }else{
  80. #ifdef AV_READ_TIME
  81.         buffer[13] ^= AV_READ_TIME();
  82.         buffer[41] ^= AV_READ_TIME()>>32;
  83. #endif
  84.     }
  85.  
  86.     for (;;) {
  87.         clock_t t = clock();
  88.  
  89.         if(last_t == t){
  90.             buffer[i&511]++;
  91.         }else{
  92.             buffer[++i&511]+= (t-last_t) % 3294638521U;
  93.             if(last_i && i-last_i > 4 || i-last_i > 64 || TEST && i-last_i > 8)
  94.                 break;
  95.         }
  96.         last_t = t;
  97.     }
  98.  
  99.     if(TEST)
  100.         buffer[0] = buffer[1] = 0;
  101.  
  102.     av_sha_init(sha, 160);
  103.     av_sha_update(sha, (uint8_t*)buffer, sizeof(buffer));
  104.     av_sha_final(sha, digest);
  105.     return AV_RB32(digest) + AV_RB32(digest+16);
  106. }
  107.  
  108. uint32_t av_get_random_seed(void)
  109. {
  110.     uint32_t seed;
  111.  
  112. #if HAVE_CRYPTGENRANDOM
  113.     HCRYPTPROV provider;
  114.     if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
  115.                             CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
  116.         BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
  117.         CryptReleaseContext(provider, 0);
  118.         if (ret)
  119.             return seed;
  120.     }
  121. #endif
  122.  
  123.     if (read_random(&seed, "/dev/urandom") == sizeof(seed))
  124.         return seed;
  125.     if (read_random(&seed, "/dev/random")  == sizeof(seed))
  126.         return seed;
  127.     return get_generic_seed();
  128. }
  129.  
  130. #if TEST
  131. #undef printf
  132. #define N 256
  133. #include <stdio.h>
  134.  
  135. int main(void)
  136. {
  137.     int i, j, retry;
  138.     uint32_t seeds[N];
  139.  
  140.     for (retry=0; retry<3; retry++){
  141.         for (i=0; i<N; i++){
  142.             seeds[i] = av_get_random_seed();
  143.             for (j=0; j<i; j++)
  144.                 if (seeds[j] == seeds[i])
  145.                     goto retry;
  146.         }
  147.         printf("seeds OK\n");
  148.         return 0;
  149.         retry:;
  150.     }
  151.     printf("FAIL at %d with %X\n", j, seeds[j]);
  152.     return 1;
  153. }
  154. #endif
  155.