src/base/utils/random.cpp

   1 /*
   2  * Bittorrent Client using Qt and libtorrent.
   3  * Copyright (C) 2017  Mike Tzou
   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 "random.h"
  30
  31 #include <random>
  32
  33 #include <QtLogging>
  34 #include <QtSystemDetection>
  35
  36 #if defined(Q_OS_WIN)
  37 #include <windows.h>
  38 #include "base/global.h"
  39 #include "base/utils/os.h"
  40 #elif defined(Q_OS_LINUX)
  41 #include <cerrno>
  42 #include <cstring>
  43 #include <sys/random.h>
  44 #else
  45 #include <cerrno>
  46 #include <cstdio>
  47 #include <cstring>
  48 #endif
  49
  50 namespace
  51 {
  52 #if defined(Q_OS_WIN)
  53     class RandomLayer
  54     {
  55     // need to satisfy UniformRandomBitGenerator requirements
  56     public:
  57         using result_type = uint32_t;
  58
  59         RandomLayer()
  60             : m_processPrng {Utils::OS::loadWinAPI<PPROCESSPRNG>(u"BCryptPrimitives.dll"_s, "ProcessPrng")}
  61         {
  62             if (!m_processPrng)
  63                 qFatal("Failed to load ProcessPrng().");
  64         }
  65
  66         static constexpr result_type min()
  67         {
  68             return std::numeric_limits<result_type>::min();
  69         }
  70
  71         static constexpr result_type max()
  72         {
  73             return std::numeric_limits<result_type>::max();
  74         }
  75
  76         result_type operator()()
  77         {
  78             result_type buf = 0;
  79             const bool result = m_processPrng(reinterpret_cast<PBYTE>(&buf), sizeof(buf));
  80             if (!result)
  81                 qFatal("ProcessPrng() failed.");
  82
  83             return buf;
  84         }
  85
  86     private:
  87         using PPROCESSPRNG = BOOL (WINAPI *)(PBYTE, SIZE_T);
  88         const PPROCESSPRNG m_processPrng;
  89     };
  90 #elif defined(Q_OS_LINUX)
  91     class RandomLayer
  92     {
  93     // need to satisfy UniformRandomBitGenerator requirements
  94     public:
  95         using result_type = uint32_t;
  96
  97         RandomLayer()
  98         {
  99         }
 100
 101         static constexpr result_type min()
 102         {
 103             return std::numeric_limits<result_type>::min();
 104         }
 105
 106         static constexpr result_type max()
 107         {
 108             return std::numeric_limits<result_type>::max();
 109         }
 110
 111         result_type operator()()
 112         {
 113             const int RETRY_MAX = 3;
 114
 115             for (int i = 0; i < RETRY_MAX; ++i)
 116             {
 117                 result_type buf = 0;
 118                 const ssize_t result = ::getrandom(&buf, sizeof(buf), 0);
 119                 if (result == sizeof(buf))  // success
 120                     return buf;
 121
 122                 if (result < 0)
 123                     qFatal("getrandom() error. Reason: %s. Error code: %d.", std::strerror(errno), errno);
 124             }
 125
 126             qFatal("getrandom() failed. Reason: too many retries.");
 127         }
 128     };
 129 #else
 130     class RandomLayer
 131     {
 132     // need to satisfy UniformRandomBitGenerator requirements
 133     public:
 134         using result_type = uint32_t;
 135
 136         RandomLayer()
 137             : m_randDev {fopen("/dev/urandom", "rb")}
 138         {
 139             if (!m_randDev)
 140                 qFatal("Failed to open /dev/urandom. Reason: %s. Error code: %d.", std::strerror(errno), errno);
 141         }
 142
 143         ~RandomLayer()
 144         {
 145             fclose(m_randDev);
 146         }
 147
 148         static constexpr result_type min()
 149         {
 150             return std::numeric_limits<result_type>::min();
 151         }
 152
 153         static constexpr result_type max()
 154         {
 155             return std::numeric_limits<result_type>::max();
 156         }
 157
 158         result_type operator()() const
 159         {
 160             result_type buf = 0;
 161             if (fread(&buf, sizeof(buf), 1, m_randDev) != 1)
 162                 qFatal("Read /dev/urandom error. Reason: %s. Error code: %d.", std::strerror(errno), errno);
 163
 164             return buf;
 165         }
 166
 167     private:
 168         FILE *m_randDev = nullptr;
 169     };
 170 #endif
 171 }
 172
 173 uint32_t Utils::Random::rand(const uint32_t min, const uint32_t max)
 174 {
 175     static RandomLayer layer;
 176
 177     // new distribution is cheap: https://stackoverflow.com/a/19036349
 178     std::uniform_int_distribution<uint32_t> uniform(min, max);
 179
 180     return uniform(layer);
 181 }