DTLS trickery

Probably the last post in 2022.

I fixed SOCKS5 handling in psc and crash so that it is now possible to use it with curl and IPv6. Also added DTLS (read: TLS over UDP) support for crash in order to make it possible to use anti censorship SOCKS proxies in countries that block outgoing TCP connections such as in Iran (see previous post).

When I read about LibreSSL having QUIC support, I tried to use this, but their bold announcement was a spoiler. They only "support" the QUIC handshake to obtain keying materials by means of TLS integration. I wouldn't really call this "QUIC support", although I love LibreSSL much more than OpenSSL (due to their permanent API changes). As DTLS has only reliability for its handshake, I had to add my own TCP-style data flow mechanisms to handle packet loss and re-orders. OpenSSL also wants to add QUIC support, so lets see in a couple of years how far this goes (hopefully with full proto and API support and not just the handshake) to finally have a usable QUIC lib.

Crash also switched from TLS v1.2 to v1.3 being mandatory, i.e. it is not proto compatible to the 2.x versions anymore. As soon as DTLS v1.3 will be widely deployed, it will also switch to DTLS v1.3. Due to all these new features and compat things the crash-3 versions are dubbed experimental (although working stable).

Wish you a nice rest of 2022 and a Guten Rutsch for 2023!