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#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
48static 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
65static uint32_t get_generic_seed(void)
66{
67    uint64_t tmp[120/8];
68    struct AVSHA *sha = (void*)tmp;
69    clock_t last_t  = 0;
70    clock_t last_td = 0;
71    clock_t init_t = 0;
72    static uint64_t i = 0;
73    static uint32_t buffer[512] = { 0 };
74    unsigned char digest[20];
75    uint64_t last_i = i;
76
77    av_assert0(sizeof(tmp) >= av_sha_size);
78
79    if(TEST){
80        memset(buffer, 0, sizeof(buffer));
81        last_i = i = 0;
82    }else{
83#ifdef AV_READ_TIME
84        buffer[13] ^= AV_READ_TIME();
85        buffer[41] ^= AV_READ_TIME()>>32;
86#endif
87    }
88
89    for (;;) {
90        clock_t t = clock();
91        if (last_t + 2*last_td + (CLOCKS_PER_SEC > 1000) >= t) {
92            last_td = t - last_t;
93            buffer[i & 511] = 1664525*buffer[i & 511] + 1013904223 + (last_td % 3294638521U);
94        } else {
95            last_td = t - last_t;
96            buffer[++i & 511] += last_td % 3294638521U;
97            if ((t - init_t) >= CLOCKS_PER_SEC>>5)
98                if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i - last_i > 8)
99                    break;
100        }
101        last_t = t;
102        if (!init_t)
103            init_t = t;
104    }
105
106    if(TEST) {
107        buffer[0] = buffer[1] = 0;
108    } else {
109#ifdef AV_READ_TIME
110        buffer[111] += AV_READ_TIME();
111#endif
112    }
113
114    av_sha_init(sha, 160);
115    av_sha_update(sha, (const uint8_t *)buffer, sizeof(buffer));
116    av_sha_final(sha, digest);
117    return AV_RB32(digest) + AV_RB32(digest + 16);
118}
119
120uint32_t av_get_random_seed(void)
121{
122    uint32_t seed;
123
124#if HAVE_BCRYPT
125    BCRYPT_ALG_HANDLE algo_handle;
126    NTSTATUS ret = BCryptOpenAlgorithmProvider(&algo_handle, BCRYPT_RNG_ALGORITHM,
127                                               MS_PRIMITIVE_PROVIDER, 0);
128    if (BCRYPT_SUCCESS(ret)) {
129        NTSTATUS ret = BCryptGenRandom(algo_handle, (UCHAR*)&seed, sizeof(seed), 0);
130        BCryptCloseAlgorithmProvider(algo_handle, 0);
131        if (BCRYPT_SUCCESS(ret))
132            return seed;
133    }
134#endif
135
136#if HAVE_ARC4RANDOM
137    return arc4random();
138#endif
139
140    if (read_random(&seed, "/dev/urandom") == sizeof(seed))
141        return seed;
142    if (read_random(&seed, "/dev/random")  == sizeof(seed))
143        return seed;
144    return get_generic_seed();
145}
146