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https://github.com/FFmpeg/FFmpeg.git
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01d245ef43
The new code is faster and reuses the previous state in case of multiple calls. The previous code could easily end up in near-infinite loops, if the difference between two clock() calls never was larger than 1. This makes fate-parseutils finish in finite time when run in wine, if CryptGenRandom isn't available (which e.g. isn't available if targeting Windows RT/metro). Patch originally by Michael Niedermayer but with some modifications by Martin Storsjö. Signed-off-by: Martin Storsjö <martin@martin.st>
116 lines
3.0 KiB
C
116 lines
3.0 KiB
C
/*
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* Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "config.h"
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#if HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#if HAVE_CRYPTGENRANDOM
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#include <windows.h>
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#include <wincrypt.h>
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#endif
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#include <fcntl.h>
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#include <math.h>
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#include <time.h>
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#include "internal.h"
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#include "intreadwrite.h"
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#include "mem.h"
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#include "timer.h"
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#include "random_seed.h"
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#include "sha.h"
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static int read_random(uint32_t *dst, const char *file)
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{
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#if HAVE_UNISTD_H
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int fd = avpriv_open(file, O_RDONLY);
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int err = -1;
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if (fd == -1)
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return -1;
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err = read(fd, dst, sizeof(*dst));
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close(fd);
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return err;
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#else
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return -1;
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#endif
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}
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static uint32_t get_generic_seed(void)
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{
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struct AVSHA *sha = av_sha_alloc();
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clock_t last_t = 0;
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static uint64_t i = 0;
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static uint32_t buffer[512] = { 0 };
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unsigned char digest[20];
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uint64_t last_i = i;
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for (;;) {
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clock_t t = clock();
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if (last_t == t) {
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buffer[i & 511]++;
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} else {
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buffer[++i & 511] += (t - last_t) % 3294638521U;
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if (last_i && i - last_i > 4 || i - last_i > 64)
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break;
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}
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last_t = t;
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}
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if (!sha) {
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uint32_t seed = 0;
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int j;
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// Unable to allocate an sha context, just xor the buffer together
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// to create something hopefully unique.
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for (j = 0; j < 512; j++)
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seed ^= buffer[j];
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return seed;
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}
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av_sha_init(sha, 160);
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av_sha_update(sha, (const uint8_t *) buffer, sizeof(buffer));
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av_sha_final(sha, digest);
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av_free(sha);
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return AV_RB32(digest) + AV_RB32(digest + 16);
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}
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uint32_t av_get_random_seed(void)
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{
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uint32_t seed;
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#if HAVE_CRYPTGENRANDOM
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HCRYPTPROV provider;
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if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
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CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
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BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
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CryptReleaseContext(provider, 0);
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if (ret)
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return seed;
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}
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#endif
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if (read_random(&seed, "/dev/urandom") == sizeof(seed))
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return seed;
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if (read_random(&seed, "/dev/random") == sizeof(seed))
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return seed;
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return get_generic_seed();
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}
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