0426-Do-not-let-the-server-load-chunks-from-newer-version.patch

From 436002c12133ffec2180ad47f4b16609b6de4399 Mon Sep 17 00:00:00 2001
From: Zach Brown <zach@zachbr.io>
Date: Tue, 23 Jul 2019 20:44:47 -0500
Subject: [PATCH] Do not let the server load chunks from newer versions

If the server attempts to load a chunk generated by a newer version of
the game, immediately stop the server to prevent data corruption.

You can override this functionality at your own peril.

diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
index 98cc4efc..f86d3aa2 100644
--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
@@ -43,9 +43,23 @@ public class ChunkRegionLoader {
         return holder.protoChunk;
     }
 
+     // Paper start
+     private static final int CURRENT_DATA_VERSION = SharedConstants.getGameVersion().getWorldVersion();
+     private static final boolean JUST_CORRUPT_IT = Boolean.getBoolean("Paper.ignoreWorldDataVersion");
+     // Paper end
+
     public static InProgressChunkHolder loadChunk(WorldServer worldserver, DefinedStructureManager definedstructuremanager, VillagePlace villageplace, ChunkCoordIntPair chunkcoordintpair, NBTTagCompound nbttagcompound, boolean distinguish) {
         ArrayDeque<Runnable> tasksToExecuteOnMain = new ArrayDeque<>();
         // Paper end
+        // Paper start - Do NOT attempt to load chunks saved with newer versions
+        if (nbttagcompound.hasKeyOfType("DataVersion", 3)) {
+            int dataVersion = nbttagcompound.getInt("DataVersion");
+            if (!JUST_CORRUPT_IT && dataVersion > CURRENT_DATA_VERSION) {
+                new RuntimeException("Server attempted to load chunk saved with newer version of minecraft! " + dataVersion + " > " + CURRENT_DATA_VERSION).printStackTrace();
+                System.exit(1);
+            }
+        }
+        // Paper end
         ChunkGenerator<?> chunkgenerator = worldserver.getChunkProvider().getChunkGenerator();
         WorldChunkManager worldchunkmanager = chunkgenerator.getWorldChunkManager();
         NBTTagCompound nbttagcompound1 = nbttagcompound.getCompound("Level");
diff --git a/src/main/java/net/minecraft/server/SharedConstants.java b/src/main/java/net/minecraft/server/SharedConstants.java
index cd04322e..7befab85 100644
--- a/src/main/java/net/minecraft/server/SharedConstants.java
+++ b/src/main/java/net/minecraft/server/SharedConstants.java
@@ -33,6 +33,7 @@ public class SharedConstants {
         return stringbuilder.toString();
     }
 
+    public static GameVersion getGameVersion() { return a(); } // Paper - OBFHELPER
     public static GameVersion a() {
         if (SharedConstants.d == null) {
             SharedConstants.d = MinecraftVersion.a();
-- 
2.24.1