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
45static 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
62static 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
106uint32_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
133int 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
153