Vulnerable to slow TLS attacks

[SabrinaJewson]

The code of serve_tls_incoming will block the current task while the TLS handshake is being accepted, meaning no new TCP connections can be accepted in this time. It seems to me that this opens up servers to a simple DOS vulnerability, where one client that performs a TLS handshake very slowly will prevent all new connections to the server.

[0xAlcibiades]

@SabrinaJewson would you like to tackle a fix?

[SabrinaJewson]

I don’t know what kind of fix you’d like. There are two ways I can immediately think of:

• Use TlsListener internally. That crate comes with a few configuration options this crate can’t easily make room for in its API, though.
• Change the public API to use something other than Streams, like a stream of futures that each resolves to a TLS stream.

If I were needing the functionality provided by this crate in my own code, I’d just use TlsListener anyway, so I guess I’m not that motivated.

[0xAlcibiades]

That is indeed how this is implemented, it's an async stream of futures which yields, you could simply spawn the acceptor in the loop perhaps? However, the lack of motivation is probably gonna preclude you from working on it ;)