TgAuth2

A player who joins the server types tgauth link and is sent to a Telegram bot. The player opens the chat, sends start to the bot, and the bot checks the whitelist before issuing a 6-digit code. Once that code is entered, the Telegram account is permanently linked to the player's server account, so later logins can be confirmed from Telegram alone.

Each login is confirmed in the Telegram chat with inline Yes and No buttons. A device that the player has used before stays trusted for a 12-hour session, while a new device or a changed IP prompts a new confirmation. The fingerprint combines the IP address with the player UUID, so two players behind the same NAT still get separate fingerprints. A player using a VPN whose IP changes has the session invalidated and must confirm through Telegram at the next login.

The mod is server-side only and is written for NeoForge 1.21.1. Only Telegram IDs on the whitelist can register, so the server owner controls who gets an account. The bot token is created with BotFather, and Telegram IDs can be collected by having players write to userinfobot and copy the Id. The mod works with offline mode servers, since UUID matching is provided by NeoForge in both online and offline modes. It is released under the Apache License 2.0 and is open source, with public links for the source code and issue tracker.