DirectAuth

DirectAuth is a server-side authentication mod for Minecraft NeoForge 1.21.1. It provides a secure login system for offline-mode servers, with optional auto-login for players who own a legitimate Minecraft account.

It is strictly server-side: clients do not need to install this mod to join. Players can connect with any vanilla client.

All database operations run asynchronously, so the main server thread never freezes during logins.

Key Features

• Server-Side Only: Install it on your server and players join with any vanilla client. Nothing to install client-side.
• Zero-Configuration Database: Uses an embedded SQLite database. No MySQL or external database server required.
• No Lag: All database I/O is performed asynchronously on a separate thread pool.
• Strong Security: Passwords are hashed with PBKDF2WithHmacSHA256 using a unique salt per user.
• Online Auto-Login: Players with a legitimate Mojang/Microsoft account can use /online to verify their account and skip typing passwords in future sessions.
• Session Grace Period: If a player disconnects and reconnects within the configured grace period, they stay authenticated without logging in again.
• Anti-Bot Protection: Configurable registration delay and a maximum number of accounts per IP address.
• Strict Restrictions: Unauthenticated players cannot move, chat, interact with blocks/entities, drop or pick up items, attack, gain XP, or regenerate health.
• Smart Data Migration: When a player switches from offline to online mode their UUID changes, so the mod automatically migrates their data to the new UUID (see below).
• Localization: Ships with English (en) and Spanish (es); fully customizable message strings.

Commands

Player commands

Admin commands (require OP level 4)

⚠️ Important: Online Mode Migration

When a player runs /online, their UUID changes from the offline UUID to their real Mojang UUID, and DirectAuth migrates their data to the new UUID.

By default the mod already migrates vanilla data (inventory, ender chest, advancements, statistics) and a few common mods (graves/deaths, FTB Quests, SkinRestorer).

If your server uses other mods that store per-player data (e.g. Curios, Astral Sorcery, FTB Teams), the server administrator must add those folder names to the migration config before players run /online. Otherwise that mod-specific progress may be lost.

Always back up your world before migrating on a heavily modded server.

Installation

1. Download the .jar file.
2. Place it in the mods folder of your NeoForge 1.21.1 server.
3. Restart the server.

On first launch the following files are generated:

• Config: world/serverconfig/DirectAuth-config.json
• Language files: world/serverconfig/DirectAuth-lang-en.json and DirectAuth-lang-es.json
• Database: world/serverconfig/directauth.db

Configuration

Edit world/serverconfig/DirectAuth-config.json to customize:

• Language: language ("en" or "es").

• Security: minPasswordLength, maxPasswordLength, maxLoginAttempts, loginCooldownMs, loginTimeout (seconds before a non-authenticated player is kicked).

• Sessions: sessionGracePeriod (seconds a session survives after disconnect) and sessionCleanupInterval (minutes between cleanups of expired sessions).

• Anti-Bot: registrationDelay (seconds to wait before a fresh player can register) and maxAccountsPerIP.

• Data Migration: migrationMap — a map of folder name → migration mode. To support an extra mod, add its data folder there. Available modes:

  • RENAME — rename a single file that is named after the UUID (most vanilla data, SkinRestorer).
  • DIRECTORY — move/rename a whole folder named after the UUID (e.g. graves).
  • TEXT_REPLACE — rename the file and replace UUID strings inside its contents (e.g. FTB Quests).

  Example:

  "migrationMap": {
    "playerdata": "RENAME",
    "stats": "RENAME",
    "advancements": "RENAME",
    "deaths": "DIRECTORY",
    "ftbquests": "TEXT_REPLACE",
    "skinrestorer": "RENAME"
  }

Message strings can be edited in the DirectAuth-lang-*.json files.

Troubleshooting (FAQ)

Q: I keep getting teleported back when I move / I can't eat or regenerate health. A: You aren't authenticated yet. Use /register <password> (first time) or /login <password>.

Q: I lost my items from [some mod] after using /online. A: The server administrator likely hadn't added that mod's data folder to migrationMap. Contact your admin.

Technical Details

• Hashing: PBKDF2WithHmacSHA256 with a unique salt per user.
• Storage: SQLite at world/serverconfig/directauth.db — no external database server. A legacy DirectAuth_users.json is migrated automatically on first run if present.
• Session Management: Sessions are validated against the internal database (and Mojang's session servers for online users).
• Protection: The login listener is injected at high priority to prevent unauthorized packet processing.

Compatibility

• Loader: NeoForge 1.21.1
• Side: Server-side only — works with any vanilla client and can be included in any modpack.
• Supported: Dedicated servers and local LAN worlds.
• Not supported: BungeeCord/Velocity networks that need player data synchronized across multiple server instances (e.g. Lobby → Survival transfers), since data is stored in the local world directory.

💖 Support the Project

DirectAuth is open-source and free to use. If you appreciate the work that goes into building and maintaining it, please consider supporting me!

☕ Sponsor me on GitHub

Source Code & Issues: GitHub Repository · Report Issues

License

This project is licensed under the MIT License.