One Password Auth

A lightweight server-side mod/plugin that protects your offline (or online) server with a single shared password. Runs on Fabric and on Paper (and Paper forks such as Purpur) — same behaviour, same config files. Designed for small friend groups and private communities—no per-user accounts, no complex authentication schemes, just one password everyone shares!

✅ Core Features

• Single shared password for entire server access
• Secures all players/inventories before authenticating, even those with OP access
• Disables all known attack vectors (see below) including block-breaking packets from hacked clients
• Players authenticate once with /login <password> then they're IP whitelisted
• Customizable login title and description
• Discord webhook integration for event logging

🚀 Getting Started

Fabric: drop one-password-auth-fabric-*.jar into mods/. Needs Fabric API.

Paper: drop one-password-auth-paper-*.jar into plugins/. Nothing else needed.

That's it! Everything should work out of the box! The next time anyone logs in, they will be greeted with a login dialogue.

Note: On first boot, a phonetic default password (e.g. komipu42!) is generated automatically and written to the config file. Check your server console or that file to find it.

Where the files live

	Fabric	Paper
Config	config/one_password_auth_config.properties	plugins/OnePasswordAuth/one_password_auth_config.properties
IP + UUID whitelist	config/one_password_auth_ip_whitelist.txt	plugins/OnePasswordAuth/one_password_auth_ip_whitelist.txt
Pending sessions	config/one_password_auth_sessions.json	plugins/OnePasswordAuth/one_password_auth_sessions.json

The file names and formats are identical on both, so moving a server from Fabric to Paper is a copy: move those three files from config/ into plugins/OnePasswordAuth/ and everyone stays logged in.

⚙️ Customization

Upon first boot the plugin will generate a config file with a default password (such as komipu42!) and all additional customizable settings (see the table above for where it is).

All the lines except for password= are optional! The server will kick everyone if no password is set.

To change any settings, just edit the config file and restart the server.

Example

password=komipu42!
webhook_url=https://discord.com/api/webhooks/xxx/yyy
admin_webhook_url=https://discord.com/api/webhooks/xxx/zzz
login_title=§6Welcome to my server!
login_description=§7Type /login <password> to join
timeout_seconds=180

Use § followed by a color/format code in login_title or login_description for styling (e.g. §6 gold, §l bold). See https://minecraft.wiki/w/Formatting_codes for the full list.

🛡️ Attack Vectors Defended

Before they log in, players are frozen in place, made invincible, blinded, and put into spectator. On top of that, this mod also blocks:

• Breaking blocks — via hacked clients that send fake packets
• Moving or teleporting away — players are locked in position on every tick
• External state drift & Mod interference — lockdown effects are re-asserted every tick
• Admin commands & OP powers — all op permissions are taken away on lockdown
• Minimized IP-spoofing — successful logins are saved as a user UUID and IP pair
• Same-account session hijacking — if they're already logged in, a second login gets denied instead of kicking them
• Bruteforcing — 1-second cooldown, kicked after 7 tries, kicked if idle too long

🧩 Fabric vs Paper

Everything a player sees is the same on both. Two things behave differently because the Paper API doesn't expose them:

• Op levels. Bukkit can only op and de-op, not at a level. If an op is caught mid-login, Paper re-ops them at the server's op-permission-level (4 by default) instead of their old level, and logs a warning when that differs. Fabric restores the exact level.
• Duplicate logins. Fabric refuses the second connection in the server's own login check; Paper refuses it in AsyncPlayerPreLoginEvent, a moment earlier. Either way the player who is already authenticated stays online and the newcomer is told someone is already logged in.

🔨 Future Development

Upon request I may add features to this mod. It runs on Fabric and Paper; other platforms may follow if others are interested.