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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_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
void av_sha_final(AVSHA *ctx, uint8_t *digest)
Finish hashing and output digest value.
Definition: sha.c:341
#define NULL
Definition: coverity.c:32
void av_sha_update(AVSHA *ctx, const uint8_t *data, unsigned int len)
Update hash value.
Definition: sha.c:314
hash context
Definition: sha.c:34
static int read_random(uint32_t *dst, const char *file)
Definition: random_seed.c:48
av_cold int av_sha_init(AVSHA *ctx, int bits)
Initialize SHA-1 or SHA-2 hashing.
Definition: sha.c:273
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
uint8_t
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32
Definition: bytestream.h:87
int avpriv_open(const char *filename, int flags,...)
A wrapper for open() setting O_CLOEXEC.
Definition: file_open.c:66
#define N
Definition: vf_pp7.c:73
static uint32_t get_generic_seed(void)
Definition: random_seed.c:65
#define AV_READ_TIME
Definition: timer.h:26
high precision timer, useful to profile code
#define U(x)
Definition: vp56_arith.h:37
simple assert() macros that are a bit more flexible than ISO C assert().
common internal API header
ret
Definition: avfilter.c:974
static unsigned int seed
Definition: videogen.c:78
#define TEST
Definition: random_seed.c:45
uint32_t BOOL
const int av_sha_size
Definition: sha.c:43
uint32_t av_get_random_seed(void)
Get a seed to use in conjunction with random functions.
Definition: random_seed.c:109
int main(int argc, char **argv)
Definition: main.c:22
GLuint buffer
Definition: opengl_enc.c:102