1.20.2 Fix

[SzczurekYT]

Summary of your change

Before fast login had support for two variants of the start login packet - before and after 1.19.
But since then the packet has changed two times:

• In 1.19.3 removing all the signing and cryptographic stuff from it. Somehow it didn't break FastLogin, but it's always better to have it implemented properly.
• In 1.20.2 the player's uuid stopped being optional field. This broke FastLogin, resulting in an error as reported in Spigot compatibility 1.20.2 #1095

While figuring out what broke I accidentally found out that 1.19.3+ should have a proper implementation so I added it too.
Here is an image on how the start login packet has changed since 1.18.2.

Related issue

Fixes #1095

[games647]

Thank you very much for the changes. Do you know if the new "Login Acknowledged" (Client -> Server) causes any issues? In theory this packet gets received before we send the fake packet to the server. Maybe it already works due to re-ordering.

[SzczurekYT]

I don't know but I deployed the updated version of fast login on a 1.20.2 server with around 10 people and I didn't have any issues yet.

[games647]

Spent some time with it. Seems like it already works as intended, because the server (not we) sends the Login Success packet. Therefore, the client sends the acknowledge packet correctly after it.