Sending garbage data will raise weird exception

[ph]

If you throw garbage at a plain text beats input, you get all kinds of fun exceptions:

To reproduce:

% bin/logstash --log.level debug -e 'input { beats { port => 12345 } }'
...
% dd if=/dev/urandom bs=4k count=1 | nc localhost 12345

full output

Jul 11, 2016 3:05:14 PM io.netty.channel.AbstractChannelHandlerContext invokeExceptionCaught
WARNING: An exception was thrown by a user handler's exceptionCaught() method while handling the following exception:
io.netty.handler.codec.DecoderException: java.lang.IllegalArgumentException: Illegal initial capacity: -1982301064
        at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:442)
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:248)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
        at io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:36)
        at io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:339)
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:339)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:393)
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:742)
        at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:145)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: Illegal initial capacity: -1982301064
        at java.util.HashMap.<init>(HashMap.java:448)
        at java.util.HashMap.<init>(HashMap.java:467)
        at org.logstash.beats.BeatsParser.decode(BeatsParser.java:125)
        at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:411)
        ... 9 more

[ph]

The beats parser get confused by the frame it received and just crash, So the way to fix this is to make sure we have received a valid header at the beginning of the batch to continue with the parser if its not the case we can just raise and InvalidFrameException or UnknownProtocol Error.