limit length of generated URI to 255 chars to prevent a DoS against the QR-Code dialog

src/qt/qrcodedialog.cpp

@@ -35,6 +35,11 @@ QRCodeDialog::~QRCodeDialog()
 void QRCodeDialog::genCode()
 {
     QString uri = getURI();
+
+    if (uri != "")
+    {
+        ui->lblQRCode->setText("");
+
         QRcode *code = QRcode_encodeString(uri.toUtf8().constData(), 0, QR_ECLEVEL_L, QR_MODE_8, 1);
         myImage = QImage(code->width + 8, code->width + 8, QImage::Format_RGB32);
         myImage.fill(0xffffff);
@@ -50,6 +55,9 @@ void QRCodeDialog::genCode()
         QRcode_free(code);
         ui->lblQRCode->setPixmap(QPixmap::fromImage(myImage).scaled(300, 300));
     }
+    else
+        ui->lblQRCode->setText(tr("Resulting URI too long, try to reduce the text for label / message."));
+}
 
 QString QRCodeDialog::getURI()
 {
@@ -81,7 +89,11 @@ QString QRCodeDialog::getURI()
         paramCount++;
     }
 
+    // limit URI length to 255 chars, to prevent a DoS of the QR-Code dialog
+    if (ret.length() < 256)
         return ret;
+    else
+        return QString("");
 }
 
 void QRCodeDialog::on_lnReqAmount_textChanged(const QString &arg1)