src/base/utils/randomlayer_linux.cpp

   1 /*
   2  * Bittorrent Client using Qt and libtorrent.
   3  * Copyright (C) 2024  Mike Tzou (Chocobo1)
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18  *
  19  * In addition, as a special exception, the copyright holders give permission to
  20  * link this program with the OpenSSL project's "OpenSSL" library (or with
  21  * modified versions of it that use the same license as the "OpenSSL" library),
  22  * and distribute the linked executables. You must obey the GNU General Public
  23  * License in all respects for all of the code used other than "OpenSSL".  If you
  24  * modify file(s), you may extend this exception to your version of the file(s),
  25  * but you are not obligated to do so. If you do not wish to do so, delete this
  26  * exception statement from your version.
  27  */
  28
  29 #include <cerrno>
  30 #include <cstring>
  31 #include <limits>
  32
  33 #include <sys/random.h>
  34
  35 #include <QtLogging>
  36
  37 namespace
  38 {
  39     class RandomLayer
  40     {
  41     // need to satisfy UniformRandomBitGenerator requirements
  42     public:
  43         using result_type = uint32_t;
  44
  45         RandomLayer()
  46         {
  47         }
  48
  49         static constexpr result_type min()
  50         {
  51             return std::numeric_limits<result_type>::min();
  52         }
  53
  54         static constexpr result_type max()
  55         {
  56             return std::numeric_limits<result_type>::max();
  57         }
  58
  59         result_type operator()()
  60         {
  61             const int RETRY_MAX = 3;
  62
  63             for (int i = 0; i < RETRY_MAX; ++i)
  64             {
  65                 result_type buf = 0;
  66                 const ssize_t result = ::getrandom(&buf, sizeof(buf), 0);
  67                 if (result == sizeof(buf))  // success
  68                     return buf;
  69
  70                 if (result < 0)
  71                     qFatal("getrandom() error. Reason: %s. Error code: %d.", std::strerror(errno), errno);
  72             }
  73
  74             qFatal("getrandom() failed. Reason: too many retries.");
  75         }
  76     };
  77 }