Traits System Anticheat (#1358)

# Description

It turns out that there was no system in place for serverside fact
checking of whether or not people have a legal traits list. Last night a
bug was reported whereby a player used Cheat Engine to give himself
every trait in the game, bypassing the points system entirely. It's not
actually possible to reduce a trait selection down to a legal list
without creating interesting race conditions, which limits my options on
how to deal with it.

So I made it a vote on the Einstein Engines discord, and the vote was
unanimous. PUNISH THE CHEATERS.

<details><summary><h1>Media</h1></summary>
<p>

https://www.youtube.com/watch?v=X2QMN0a_TrA

</p>
</details>

# Changelog


:cl:
- add: Implemented Anti-cheat for Traits. Attempting to join a round
with an illegal traits list will result in hilarious consequences.

Content.Server/Traits/TraitSystem.cs

@@ -1,14 +1,23 @@
 using System.Linq;
+using Content.Server.Administration.Logs;
+using Content.Server.Administration.Systems;
+using Content.Server.Chat.Managers;
 using Content.Server.GameTicking;
 using Content.Server.Players.PlayTimeTracking;
+using Content.Shared.CCVar;
+using Content.Shared.Chat;
 using Content.Shared.Customization.Systems;
+using Content.Shared.Database;
 using Content.Shared.Players;
 using Content.Shared.Roles;
 using Content.Shared.Traits;
+using Robust.Server.Player;
 using Robust.Shared.Configuration;
 using Robust.Shared.Prototypes;
+using Robust.Shared.Random;
 using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Utility;
+using Timer = Robust.Shared.Timing.Timer;
 
 namespace Content.Server.Traits;
 
@@ -20,6 +29,11 @@ public sealed class TraitSystem : EntitySystem
     [Dependency] private readonly PlayTimeTrackingManager _playTimeTracking = default!;
     [Dependency] private readonly IConfigurationManager _configuration = default!;
     [Dependency] private readonly IComponentFactory _componentFactory = default!;
+    [Dependency] private readonly IAdminLogManager _adminLog = default!;
+    [Dependency] private readonly AdminSystem _adminSystem = default!;
+    [Dependency] private readonly IPlayerManager _playerManager = default!;
+    [Dependency] private readonly IRobustRandom _random = default!;
+    [Dependency] private readonly IChatManager _chatManager = default!;
 
     public override void Initialize()
     {
@@ -31,6 +45,9 @@ public override void Initialize()
     // When the player is spawned in, add all trait components selected during character creation
     private void OnPlayerSpawnComplete(PlayerSpawnCompleteEvent args)
     {
+        var pointsTotal = _configuration.GetCVar(CCVars.GameTraitsDefaultPoints);
+        var traitSelections = _configuration.GetCVar(CCVars.GameTraitsMax);
+
         foreach (var traitId in args.Profile.TraitPreferences)
         {
             if (!_prototype.TryIndex<TraitPrototype>(traitId, out var traitPrototype))
@@ -47,8 +64,15 @@ private void OnPlayerSpawnComplete(PlayerSpawnCompleteEvent args)
                 out _))
                 continue;
 
+            // To check for cheaters. :FaridaBirb.png:
+            pointsTotal += traitPrototype.Points;
+            --traitSelections;
+
             AddTrait(args.Mob, traitPrototype);
         }
+
+        if (pointsTotal < 0 || traitSelections < 0)
+            PunishCheater(args.Mob);
     }
 
     /// <summary>
@@ -59,4 +83,41 @@ public void AddTrait(EntityUid uid, TraitPrototype traitPrototype)
         foreach (var function in traitPrototype.Functions)
             function.OnPlayerSpawn(uid, _componentFactory, EntityManager, _serialization);
     }
+
+    /// <summary>
+    ///     On a non-cheating client, it's not possible to save a character with a negative number of traits. This can however
+    ///     trigger incorrectly if a character was saved, and then at a later point in time an admin changes the traits Cvars to reduce the points.
+    ///     Or if the points costs of traits is increased.
+    /// </summary>
+    private void PunishCheater(EntityUid uid)
+    {
+        _adminLog.Add(LogType.AdminMessage, LogImpact.High,
+            $"{ToPrettyString(uid):entity} attempted to spawn with an invalid trait list. This might be a mistake, or they might be cheating");
+
+        if (!_configuration.GetCVar(CCVars.TraitsPunishCheaters)
+            || !_playerManager.TryGetSessionByEntity(uid, out var targetPlayer))
+            return;
+
+        // For maximum comedic effect, this is plenty of time for the cheater to get on station and start interacting with people.
+        var timeToDestroy = _random.NextFloat(120, 360);
+
+        Timer.Spawn(TimeSpan.FromSeconds(timeToDestroy), () => VaporizeCheater(targetPlayer));
+    }
+
+    /// <summary>
+    ///     https://www.youtube.com/watch?v=X2QMN0a_TrA
+    /// </summary>
+    private void VaporizeCheater (Robust.Shared.Player.ICommonSession targetPlayer)
+    {
+        _adminSystem.Erase(targetPlayer);
+
+        var feedbackMessage = $"[font size=24][color=#ff0000]{"You have spawned in with an illegal trait point total. If this was a result of cheats, then your nonexistence is a skill issue. Otherwise, feel free to click 'Return To Lobby', and fix your trait selections."}[/color][/font]";
+        _chatManager.ChatMessageToOne(
+            ChatChannel.Emotes,
+            feedbackMessage,
+            feedbackMessage,
+            EntityUid.Invalid,
+            false,
+            targetPlayer.Channel);
+    }
 }

Content.Shared/CCVar/CCVars.cs

@@ -381,6 +381,13 @@ public static readonly CVarDef<bool>
         public static readonly CVarDef<int> GameTraitsDefaultPoints =
             CVarDef.Create("game.traits_default_points", 10, CVar.REPLICATED);
 
+        /// <summary>
+        ///     Whether the game will SMITE people who used cheat engine to spawn with all of the traits.
+        ///     Illegal trait totals will still be logged even if this is disabled.
+        ///     If you are intending to decrease the trait points availability, or modify the costs of traits, consider temporarily disabling this.
+        /// </summary>
+        public static readonly CVarDef<bool> TraitsPunishCheaters =
+            CVarDef.Create("game.traits_punish_cheaters", true, CVar.REPLICATED);
 
         /// <summary>
         ///     Whether to allow characters to select loadout items.