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