OfflineSimpleLogin

A Folia-compatible Minecraft Paper plugin that requires offline-mode players to register and login. Passwords are encrypted with Argon2id and stored in SQLite or PostgreSQL. Designed to work alongside LimitedOfflineModePaper.

Features

• ✅ Folia support — Fully compatible with Folia's regionized multithreading
• ✅ Offline-mode authentication — Register/login for players joining without Mojang auth
• ✅ Premium bypass — Mojang-authenticated players are automatically detected and bypass the auth system
• ✅ Argon2id hashing — Industry-standard password hashing with configurable parameters
• ✅ SQLite & PostgreSQL — Choose your database backend
• ✅ Session management — IP-based auto-login with configurable timeout
• ✅ Player restrictions — Block movement, interaction, chat, damage until authenticated
• ✅ Fully configurable — All messages use MiniMessage format, configurable in config.yml
• ✅ LimitedOfflineModePaper compatible — Works seamlessly alongside LOM for Netty-level offline login bypass

How It Works

Player connects → LimitedOfflineModePaper (Netty intercept)
               → Player joins server
               → OfflineSimpleLogin checks GameProfile
               │
               ├─ Premium player (has "textures" property)
               │  └─ Auto-authenticated — no prompt, no restrictions
               │
               └─ Offline player (no "textures" property)
                  ├─ Has valid IP session? → Auto-authenticated
                  ├─ Registered? → Show login prompt
                  └─ Not registered? → Show register prompt

Requirements

• Server: Paper 26.1.2+ or Folia
• Java: 25+
• Optional: LimitedOfflineModePaper (for Netty-level offline login bypass)

Installation

1. Download the latest JAR from Releases
2. Place the JAR in your server's plugins/ folder
3. Restart the server
4. Configure plugins/OfflineSimpleLogin/config.yml as needed

Commands

Command	Permission	Description
/register <password> <confirm>	offlinesimplelogin.register	Register a new account
/login <password>	offlinesimplelogin.login	Login to your account
/logout	offlinesimplelogin.logout	Logout from your account
/changepassword <old> <new>	offlinesimplelogin.changepassword	Change your password

All commands default to true for all players. Premium (online-mode) players are automatically rejected with a message.

Configuration

Database

database:
  type: sqlite  # or "postgresql"
  sqlite:
    file: "data/offline-simple-login.db"
  postgresql:
    host: localhost
    port: 5432
    database: offlinesimplelogin
    username: minecraft
    password: ""

Argon2

argon2:
  salt-length: 16
  hash-length: 32
  parallelism: 1
  memory: 65536    # 64 MB
  iterations: 3

Sessions

session:
  timeout: 1800        # Session timeout (seconds)
  ip-auto-login: true   # Auto-login same IP within timeout

Restrictions

restrictions:
  show-title: true           # Show Title prompts on join
  prevent-movement: true
  prevent-interaction: true
  prevent-inventory: true
  prevent-chat: true
  prevent-damage: true
  prevent-dealing-damage: true

All messages in config.yml support Adventure MiniMessage format.

Building from Source

# Build with default version (0.1.0+26.1.2)
./gradlew build

# Build with custom version
./gradlew build -Pver="vX.Y.Z"

# Build a release (strips version from filename for stable tags)
./gradlew -Pver="v0.1.0" release

Output JAR is in build/libs/.

Architecture

OfflineSimpleLogin/
├── OfflineSimpleLogin.kt        # Main plugin class + Brigadier command executors
├── config/
│   └── PluginConfig.kt          # Configuration data classes
├── database/
│   ├── DatabaseManager.kt       # Database interface
│   ├── SQLiteDatabaseManager.kt # SQLite implementation (WAL mode)
│   └── PostgreSQLDatabaseManager.kt # PostgreSQL implementation (HikariCP)
├── auth/
│   ├── PasswordHasher.kt        # Argon2id hashing wrapper
│   ├── SessionManager.kt        # Session management (memory + DB)
│   └── AuthManager.kt           # Auth flow orchestration
└── listener/
    ├── PlayerLoginListener.kt   # Join event handling + premium detection
    └── PlayerRestrictionListener.kt # Unauthenticated player restrictions

Dependencies

• Paper API 26.1.2+
• Kotlin 2.4.0
• Argon2-jvm — Argon2 hashing
• SQLite JDBC — SQLite driver
• PostgreSQL JDBC — PostgreSQL driver
• HikariCP — Connection pooling
• PaperLib — Paper utilities

License

This project is licensed under the MIT License — see the LICENSE file for details.