Line data    Source code

       1             : /*
       2             :  * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
       3             :  *
       4             :  * This file is part of Libav.
       5             :  *
       6             :  * Libav 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             :  * Libav 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 Libav; 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 "internal.h"
      34             : #include "intreadwrite.h"
      35             : #include "mem.h"
      36             : #include "timer.h"
      37             : #include "random_seed.h"
      38             : #include "sha.h"
      39             : 
      40           0 : static int read_random(uint32_t *dst, const char *file)
      41             : {
      42             : #if HAVE_UNISTD_H
      43           0 :     int fd = avpriv_open(file, O_RDONLY);
      44           0 :     int err = -1;
      45             : 
      46           0 :     if (fd == -1)
      47           0 :         return -1;
      48           0 :     err = read(fd, dst, sizeof(*dst));
      49           0 :     close(fd);
      50             : 
      51           0 :     return err;
      52             : #else
      53             :     return -1;
      54             : #endif
      55             : }
      56             : 
      57           0 : static uint32_t get_generic_seed(void)
      58             : {
      59           0 :     struct AVSHA *sha = av_sha_alloc();
      60           0 :     clock_t last_t  = 0;
      61             :     static uint64_t i = 0;
      62             :     static uint32_t buffer[512] = { 0 };
      63             :     unsigned char digest[20];
      64           0 :     uint64_t last_i = i;
      65             : 
      66           0 :     for (;;) {
      67           0 :         clock_t t = clock();
      68             : 
      69           0 :         if (last_t == t) {
      70           0 :             buffer[i & 511]++;
      71             :         } else {
      72           0 :             buffer[++i & 511] += (t - last_t) % 3294638521U;
      73           0 :             if (last_i && i - last_i > 4 || i - last_i > 64)
      74             :                 break;
      75             :         }
      76           0 :         last_t = t;
      77             :     }
      78             : 
      79           0 :     if (!sha) {
      80           0 :         uint32_t seed = 0;
      81             :         int j;
      82             :         // Unable to allocate an sha context, just xor the buffer together
      83             :         // to create something hopefully unique.
      84           0 :         for (j = 0; j < 512; j++)
      85           0 :             seed ^= buffer[j];
      86           0 :         return seed;
      87             :     }
      88           0 :     av_sha_init(sha, 160);
      89           0 :     av_sha_update(sha, (const uint8_t *) buffer, sizeof(buffer));
      90           0 :     av_sha_final(sha, digest);
      91           0 :     av_free(sha);
      92           0 :     return AV_RB32(digest) + AV_RB32(digest + 16);
      93             : }
      94             : 
      95           0 : uint32_t av_get_random_seed(void)
      96             : {
      97             :     uint32_t seed;
      98             : 
      99             : #if HAVE_CRYPTGENRANDOM
     100             :     HCRYPTPROV provider;
     101             :     if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
     102             :                             CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
     103             :         BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);
     104             :         CryptReleaseContext(provider, 0);
     105             :         if (ret)
     106             :             return seed;
     107             :     }
     108             : #endif
     109             : 
     110           0 :     if (read_random(&seed, "/dev/urandom") == sizeof(seed))
     111           0 :         return seed;
     112           0 :     if (read_random(&seed, "/dev/random")  == sizeof(seed))
     113           0 :         return seed;
     114           0 :     return get_generic_seed();
     115             : }