qt: Force TLS1.0+ for SSL connections

Github-Pull: #6384
Rebased-From: 15e26a6

src/qt/bitcoin.cpp

@@ -48,6 +48,7 @@
 #include <QThread>
 #include <QTimer>
 #include <QTranslator>
+#include <QSslConfiguration>
 
 #if defined(QT_STATICPLUGIN)
 #include <QtPlugin>
@@ -515,6 +516,13 @@ int main(int argc, char *argv[])
 #ifdef Q_OS_MAC
     QApplication::setAttribute(Qt::AA_DontShowIconsInMenus);
 #endif
+#if QT_VERSION >= 0x050500
+    // Because of the POODLE attack it is recommended to disable SSLv3 (https://disablessl3.com/),
+    // so set SSL protocols to TLS1.0+.
+    QSslConfiguration sslconf = QSslConfiguration::defaultConfiguration();
+    sslconf.setProtocol(QSsl::TlsV1_0OrLater);
+    QSslConfiguration::setDefaultConfiguration(sslconf);
+#endif
 
     // Register meta types used for QMetaObject::invokeMethod
     qRegisterMetaType< bool* >();