Merge pull request #6166

Maxim Biro (1):
      fix: Usage of random

src/core/core.cpp

@@ -34,8 +34,10 @@
 #include "util/strongtype.h"
 
 #include <QCoreApplication>
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 #include <QRandomGenerator>
+#else
+#include <QDateTime>
 #endif
 #include <QRegularExpression>
 #include <QString>
@@ -667,6 +669,10 @@ void Core::onStarted()
 {
     ASSERT_CORE_THREAD;
 
+#if (QT_VERSION < QT_VERSION_CHECK(5, 10, 0))
+    qsrand(static_cast<uint>(QDateTime::currentMSecsSinceEpoch()));
+#endif
+
     // One time initialization stuff
     QString name = getUsername();
     if (!name.isEmpty()) {
@@ -795,10 +801,10 @@ void Core::bootstrapDht()
     }
 
     int i = 0;
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
-    static int j = QRandomGenerator::global()->generate() % listSize;
+    static int j = QRandomGenerator::global()->bounded(listSize);
 #else
-    static int j = qrand() % listSize;
+    static int j = static_cast<int>((static_cast<double>(qrand()) / static_cast<double>(RAND_MAX+1l)) * listSize);
 #endif
     // i think the more we bootstrap, the more we jitter because the more we overwrite nodes
     while (i < 2) {
@@ -827,7 +833,8 @@ void Core::bootstrapDht()
             PARSE_ERR(error);
         }
 
-        ++j;
+        // bootstrap off every 5th node (+ a special case to avoid cycles when listSize % 5 == 0)
+        j += 5 + !(listSize % 5);
         ++i;
     }
 }

src/widget/form/settings/privacyform.cpp

@@ -23,8 +23,10 @@
 #include <QDebug>
 #include <QFile>
 #include <QMessageBox>
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 #include <QRandomGenerator>
+#else
+#include <QDateTime>
 #endif
 
 #include "src/core/core.h"
@@ -102,19 +104,16 @@ void PrivacyForm::showEvent(QShowEvent*)
 
 void PrivacyForm::on_randomNosapamButton_clicked()
 {
-    QTime time = QTime::currentTime();
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
-    QRandomGenerator(static_cast<uint>(time.msec()));
-#else
-    qsrand(static_cast<uint>(time.msec()));
-#endif
-
     uint32_t newNospam{0};
-    for (int i = 0; i < 4; ++i)
+
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
-        newNospam = (newNospam << 8) + (QRandomGenerator::global()->generate() % 256); // Generate byte by byte. For some reason.
+    // guarantees to give a random 32-bit unsigned integer
+    newNospam = QRandomGenerator::global()->generate();
 #else
-        newNospam = (newNospam << 8) + (qrand() % 256); // Generate byte by byte. For some reason.
+    qsrand(static_cast<uint>(QDateTime::currentMSecsSinceEpoch()));
+    for (int i = 0; i < 4; ++i)
+        // Generate byte by byte, as qrand() is guaranteed to have only 15 bits of randomness (RAND_MAX is guaranteed to be 2^15)
+        newNospam = (newNospam << 8) + (static_cast<int>((static_cast<double>(qrand()) / static_cast<double>(RAND_MAX+1l)) * 256));
 #endif
 
     core->setNospam(newNospam);