FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavutil/random_seed.c
Date: 2025-10-27 03:13:05
Exec Total Coverage
Lines: 51 62 82.3%
Functions: 4 4 100.0%
Branches: 27 42 64.3%
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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_BCRYPT
30 #include <windows.h>
31 #include <bcrypt.h>
32 #endif
33 #if CONFIG_GCRYPT
34 #include <gcrypt.h>
35 #elif CONFIG_OPENSSL
36 #include <openssl/rand.h>
37 #endif
38 #include <fcntl.h>
39 #include <math.h>
40 #include <time.h>
41 #include <string.h>
42 #include "avassert.h"
43 #include "file_open.h"
44 #include "internal.h"
45 #include "intreadwrite.h"
46 #include "timer.h"
47 #include "random_seed.h"
48 #include "sha.h"
49
50 #ifndef TEST
51 #define TEST 0
52 #endif
53
54 387 static int read_random(uint8_t *dst, size_t len, const char *file)
55 {
56 #if HAVE_UNISTD_H
57 387 FILE *fp = avpriv_fopen_utf8(file, "r");
58 size_t err;
59
60
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 387 if (!fp)
61 ✗ return AVERROR_UNKNOWN;
62 387 setvbuf(fp, NULL, _IONBF, 0);
63 387 err = fread(dst, 1, len, fp);
64 387 fclose(fp);
65
66
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 387 if (err != len)
67 ✗ return AVERROR_UNKNOWN;
68
69 387 return 0;
70 #else
71 return AVERROR(ENOSYS);
72 #endif
73 }
74
75 256 static uint32_t get_generic_seed(void)
76 {
77 uint64_t tmp[120/8];
78 256 struct AVSHA *sha = (void*)tmp;
79 256 clock_t last_t = 0;
80 256 clock_t last_td = 0;
81 256 clock_t init_t = 0;
82 static uint64_t i = 0;
83 static uint32_t buffer[512] = { 0 };
84 unsigned char digest[20];
85 256 uint64_t last_i = i;
86 256 int repeats[3] = { 0 };
87
88
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 256 av_assert0(sizeof(tmp) >= av_sha_size);
89
90 if(TEST){
91 256 memset(buffer, 0, sizeof(buffer));
92 256 last_i = i = 0;
93 }else{
94 #ifdef AV_READ_TIME
95 ✗ buffer[13] ^= AV_READ_TIME();
96 ✗ buffer[41] ^= AV_READ_TIME()>>32;
97 #endif
98 }
99
100 21486795 for (;;) {
101 21487051 clock_t t = clock();
102 21487051 int incremented_i = 0;
103 21487051 int cur_td = t - last_t;
104
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 21487051 if (last_t + 2*last_td + (CLOCKS_PER_SEC > 1000) < t) {
105 // If the timer incremented by more than 2*last_td at once,
106 // we may e.g. have had a context switch. If the timer resolution
107 // is high (CLOCKS_PER_SEC > 1000), require that the timer
108 // incremented by more than 1. If the timer resolution is low,
109 // it is enough that the timer incremented at all.
110 2986 buffer[++i & 511] += cur_td % 3294638521U;
111 2986 incremented_i = 1;
112
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 21484065 } else if (t != last_t && repeats[0] > 0 && repeats[1] > 0 &&
113 ✗ repeats[2] > 0 && repeats[0] != repeats[1] &&
114 ✗ repeats[0] != repeats[2]) {
115 // If the timer resolution is high, and we get the same timer
116 // value multiple times, use variances in the number of repeats
117 // of each timer value as entropy. If we get a different number of
118 // repeats than the last two unique cases, count that as entropy
119 // and proceed to the next index.
120 ✗ buffer[++i & 511] += (repeats[0] + repeats[1] + repeats[2]) % 3294638521U;
121 ✗ incremented_i = 1;
122 } else {
123 21484065 buffer[i & 511] = 1664525*buffer[i & 511] + 1013904223 + (cur_td % 3294638521U);
124 }
125
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 21487051 if (incremented_i && (t - init_t) >= CLOCKS_PER_SEC>>5) {
126
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 1378 if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i - last_i > 8)
127 break;
128 }
129
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 21486795 if (t == last_t) {
130 1268 repeats[0]++;
131 } else {
132 // If we got a new unique number of repeats, update the history.
133
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 21485527 if (repeats[0] != repeats[1]) {
134 1934 repeats[2] = repeats[1];
135 1934 repeats[1] = repeats[0];
136 }
137 21485527 repeats[0] = 0;
138 }
139 21486795 last_t = t;
140 21486795 last_td = cur_td;
141
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 21486795 if (!init_t)
142 256 init_t = t;
143 }
144
145 if(TEST) {
146 256 buffer[0] = buffer[1] = 0;
147 } else {
148 #ifdef AV_READ_TIME
149 ✗ buffer[111] += AV_READ_TIME();
150 #endif
151 }
152
153 256 av_sha_init(sha, 160);
154 256 av_sha_update(sha, (const uint8_t *)buffer, sizeof(buffer));
155 256 av_sha_final(sha, digest);
156 256 return AV_RB32(digest) + AV_RB32(digest + 16);
157 }
158
159 387 int av_random_bytes(uint8_t* buf, size_t len)
160 {
161 int err;
162
163 #if HAVE_BCRYPT
164 BCRYPT_ALG_HANDLE algo_handle;
165 NTSTATUS ret = BCryptOpenAlgorithmProvider(&algo_handle, BCRYPT_RNG_ALGORITHM,
166 MS_PRIMITIVE_PROVIDER, 0);
167 if (BCRYPT_SUCCESS(ret)) {
168 NTSTATUS ret = BCryptGenRandom(algo_handle, (PUCHAR)buf, len, 0);
169 BCryptCloseAlgorithmProvider(algo_handle, 0);
170 if (BCRYPT_SUCCESS(ret))
171 return 0;
172 }
173 #endif
174
175 #if HAVE_ARC4RANDOM_BUF
176 arc4random_buf(buf, len);
177 return 0;
178 #endif
179
180 387 err = read_random(buf, len, "/dev/urandom");
181
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 387 if (!err)
182 387 return err;
183
184 #if CONFIG_GCRYPT
185 gcry_randomize(buf, len, GCRY_VERY_STRONG_RANDOM);
186 return 0;
187 #elif CONFIG_OPENSSL
188 if (RAND_bytes(buf, len) == 1)
189 return 0;
190 return AVERROR_EXTERNAL;
191 #else
192 ✗ return err;
193 #endif
194 }
195
196 387 uint32_t av_get_random_seed(void)
197 {
198 uint32_t seed;
199
200
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 387 if (av_random_bytes((uint8_t *)&seed, sizeof(seed)) < 0)
201 ✗ return get_generic_seed();
202
203 387 return seed;
204 }
205