Allocation of Resources Without Limits or Throttling in io.netty:netty-all

Summary

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In versions through 4.1.93.Final, 5.0.0.Alpha1 through 5.0.0.Alpha5, the `SniHandler` can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the `SniHandler` to allocate 16MB of heap. The `SniHandler` class is a handler that waits for the TLS handshake to configure a `SslHandler` according to the indicated server name by the `ClientHello` record. For this matter it allocates a `ByteBuf` using the value defined in the `ClientHello` record. Normally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the `SslClientHelloHandler`.