Phantasm AntiCheat

Last update: August 3rd 2020

Phantasm is a Terraria Anti-Cheat plugin that aims to stop all forms of cheating (and other harmful activity such as crash exploits and lag machines) in their tracks.

Phantasm is unique amongst other anti-cheat projects in that it is completely lag-aware and lag-tolerant (may cause harmless warnings for lagging players but will never ban an innocent) and it blocks and reverts detected cheats rather than just report them.

This means Phantasm is essentially an unattended anticheat solution - server staff do not need to be present for the anticheat to be effective - it deals with everything itself.

Phantasm also, optionally, doubles as a gameplay enhancer:

• When gameplay enhancing is enabled, Phantasm will fix some Multiplayer issues Terraria & tShock have - blocked events not returning items, to name one - for instance, summoning a boss will not consume the summon item if the summon event was blocked by a server plugin. The same applies to block placements and other "item consuming actions".

Update (August 3rd 2020): Protocol enhancing was scrapped because Frostspark provides it out of the box (using Spectre as the protocol library) - protection from computationally expensive action spam will still be included as part of anticheat, however.

Disclaimer

This repository contains no code. Phantasm is currently a private plugin. The goal of this repository is to serve as an issue tracker for individuals that have access to the plugin, as an advertisement of my services for anyone interested, as well as a progress tracker for myself and said involved parties.

Progress on the anticheat can be seen on the discord server I operate for my upcoming dedicated server here.

Don't email/DM me and ask for a copy, I select testers on my own, and much like with becoming a moderator/administrator somewhere - asking will only shrink your chances of being picked

How to make your server compatible with Phantasm

• Use the Frostspark server engine.
• Use only events (and not packet hooks) unless you're executing packet/protocol hacks:
• • This is because Phantasm handles most packets and runs asynchronous cheat checks on them - this means a packet that is already handled must be ignored as to not interfere with the anticheat check. Later (usually within the same tick) an event corresponding to the handled packet is raised if the cheat check passed - only then should you be performing any game-changing actions such as logging, casting abilities in custom gamemodes et cetera.
• Whenever you're sending data to a client (such as an inventory update) you must update the server-side player data as well, otherwise they will rolled back for a cheat violation (or kicked/banned at worst) - in other words, make sure to maintain consistency on both sides (if you're updating inventory, send an update packet AND update the server-side version, etc.
• • Phantasm will provide a "backwards compatibility" mode where it'll catch outgoing update packets and update the server-side model by itself. However, running in backwards compatibility mode comes with a tradeoff: You lose the ability to execute various packet hacks, as they'll get merged into the game state.

The above instructions not only make the server compatible with Phantasm, but also introduce good practices into your codebase, making it easy to fend off various exploits yourself, even if Phantasm never actually releases.

Implementation status

The Anticheat will be ported to Frostspark and live there exclusively. This process has not started yet, but will begin as soon as Frostspark is considered stable and feature-rich.

The below list is features that I've gotten working while testing against a clean/plugin-less tShock server without factoring in plugin interactions. Frostspark will allow plugin interactions to be handled automatically.

Generic:

• Impersonation: Blocked
• Packet exploits (invalid values etc.): Blocked

NPCs:

• Instakill all: Blocked
• Invalid buff/debuff application: Queued
• Teleportation: Queued

Tile:

• Unobtainable and nonexistent tiles: Blocked
• Range hacks: Blocked
• Tool checks: Queued

Projectiles:

• Spam: Blocked
• Spawn hacks: In progress, largely done.
• Damage hacks: Queued
• Projectile origin (offsets): Queued

Movement:

• Teleportation exploits: In progress (rewriting)

Items:

• Inventory editing: Blocked
• Drophacks (spawn items from thin air): Blocked
• Vacuum (pick up items across the map): In progress
• Shop coin bypass: Blocked