Updated SUBSCRIBE to be 3.1.1 compliant

netty_parser/src/main/java/org/dna/mqtt/moquette/parser/netty/SubscribeDecoder.java

@@ -38,6 +38,7 @@ class SubscribeDecoder extends DemuxDecoder {
             in.resetReaderIndex();
             return;
         }
+        //TODO check reserved fixed flags = b0010
         
         //check qos level
         if (message.getQos() != QOSType.LEAST_ONE) {
@@ -53,6 +54,10 @@ class SubscribeDecoder extends DemuxDecoder {
             readed = in.readerIndex()- start;
         }
         
+        if (message.subscriptions().isEmpty()) {
+            throw new CorruptedFrameException("subscribe MUST have got at least 1 couple topic/QoS");
+        } 
+        
         out.add(message);
     }
     
@@ -61,7 +66,12 @@ class SubscribeDecoder extends DemuxDecoder {
      */
     private void decodeSubscription(ByteBuf in, SubscribeMessage message) throws UnsupportedEncodingException {
         String topic = Utils.decodeString(in);
-        byte qos = (byte)(in.readByte() & 0x03);
+        byte qosByte = in.readByte();
+        if ((qosByte & 0xFC) > 0) { //the first 6 bits is reserved => has to be 0
+            throw new CorruptedFrameException("subscribe MUST have QoS byte with reserved buts to 0, found " + Integer.toHexString(qosByte));
+        }
+        byte qos = (byte)(qosByte & 0x03);
+        //TODO check qos id 000000xx
         message.addSubscription(new SubscribeMessage.Couple(qos, topic));
     }