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 <QtSystemDetection>
  34
  35 #ifdef Q_OS_WIN
  36 #include <windows.h>
  37 #include <ntsecapi.h>
  38 #else  // Q_OS_WIN
  39 #include <cerrno>
  40 #include <cstdio>
  41 #include <cstring>
  42 #endif
  43
  44 #include <QString>
  45
  46 #include "base/global.h"
  47
  48 #ifdef Q_OS_WIN
  49 #include "base/utils/os.h"
  50 #endif
  51
  52 namespace
  53 {
  54 #ifdef Q_OS_WIN
  55     class RandomLayer
  56     {
  57     // need to satisfy UniformRandomBitGenerator requirements
  58     public:
  59         using result_type = uint32_t;
  60
  61         RandomLayer()
  62             : m_rtlGenRandom {Utils::OS::loadWinAPI<PRTLGENRANDOM>(u"Advapi32.dll"_s, "SystemFunction036")}
  63         {
  64             if (!m_rtlGenRandom)
  65                 qFatal("Failed to load RtlGenRandom()");
  66         }
  67
  68         static constexpr result_type min()
  69         {
  70             return std::numeric_limits<result_type>::min();
  71         }
  72
  73         static constexpr result_type max()
  74         {
  75             return std::numeric_limits<result_type>::max();
  76         }
  77
  78         result_type operator()()
  79         {
  80             result_type buf = 0;
  81             const bool result = m_rtlGenRandom(&buf, sizeof(buf));
  82             if (!result)
  83                 qFatal("RtlGenRandom() failed");
  84
  85             return buf;
  86         }
  87
  88     private:
  89         using PRTLGENRANDOM = BOOLEAN (WINAPI *)(PVOID, ULONG);
  90         const PRTLGENRANDOM m_rtlGenRandom;
  91     };
  92 #else  // Q_OS_WIN
  93     class RandomLayer
  94     {
  95     // need to satisfy UniformRandomBitGenerator requirements
  96     public:
  97         using result_type = uint32_t;
  98
  99         RandomLayer()
 100             : m_randDev {fopen("/dev/urandom", "rb")}
 101         {
 102             if (!m_randDev)
 103                 qFatal("Failed to open /dev/urandom. Reason: %s. Error code: %d.\n", std::strerror(errno), errno);
 104         }
 105
 106         ~RandomLayer()
 107         {
 108             fclose(m_randDev);
 109         }
 110
 111         static constexpr result_type min()
 112         {
 113             return std::numeric_limits<result_type>::min();
 114         }
 115
 116         static constexpr result_type max()
 117         {
 118             return std::numeric_limits<result_type>::max();
 119         }
 120
 121         result_type operator()() const
 122         {
 123             result_type buf = 0;
 124             if (fread(&buf, sizeof(buf), 1, m_randDev) != 1)
 125                 qFatal("Read /dev/urandom error. Reason: %s. Error code: %d.\n", std::strerror(errno), errno);
 126
 127             return buf;
 128         }
 129
 130     private:
 131         FILE *m_randDev = nullptr;
 132     };
 133 #endif
 134 }
 135
 136 uint32_t Utils::Random::rand(const uint32_t min, const uint32_t max)
 137 {
 138     static RandomLayer layer;
 139
 140     // new distribution is cheap: https://stackoverflow.com/a/19036349
 141     std::uniform_int_distribution<uint32_t> uniform(min, max);
 142
 143     return uniform(layer);
 144 }