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/*
* Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_CRYPTGENRANDOM
#include <windows.h>
#include <wincrypt.h>
#endif
#include <fcntl.h>
#include <math.h>
#include <time.h>
#include "internal.h"
#include "intreadwrite.h"
#include "mem.h"
#include "timer.h"
#include "random_seed.h"
#include "sha.h"
static int read_random(uint32_t *dst, const char *file)
{
#if HAVE_UNISTD_H
int fd = avpriv_open(file, O_RDONLY);
int err = -1;
if (fd == -1)
return -1;
err = read(fd, dst, sizeof(*dst));
close(fd);
return err;
#else
return -1;
#endif
}
static uint32_t get_generic_seed(void)
{
struct AVSHA *sha = av_sha_alloc();
clock_t last_t = 0;
static uint64_t i = 0;
static uint32_t buffer[512] = { 0 };
unsigned char digest[20];
uint64_t last_i = i;
for (;;) {
clock_t t = clock();
if (last_t == t) {
buffer[i & 511]++;
} else {
buffer[++i & 511] += (t - last_t) % 3294638521U;
if (last_i && i - last_i > 4 || i - last_i > 64)
break;
}
last_t = t;
}
if (!sha) {
uint32_t seed = 0;
int j;
// Unable to allocate an sha context, just xor the buffer together
// to create something hopefully unique.
for (j = 0; j < 512; j++)
seed ^= buffer[j];
return seed;
}
av_sha_init(sha, 160);
av_sha_update(sha, (const uint8_t *) buffer, sizeof(buffer));
av_sha_final(sha, digest);
av_free(sha);
return AV_RB32(digest) + AV_RB32(digest + 16);
}
uint32_t av_get_random_seed(void)
{
uint32_t seed;
#if HAVE_CRYPTGENRANDOM
HCRYPTPROV provider;
if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
CryptReleaseContext(provider, 0);
if (ret)
return seed;
}
#endif
if (read_random(&seed, "/dev/urandom") == sizeof(seed))
return seed;
if (read_random(&seed, "/dev/random") == sizeof(seed))
return seed;
return get_generic_seed();
}
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