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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. #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
  156.