From 0000000000000000000000000000000000000000 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If the server attempts to load a chunk generated by a newer version of
the game, immediately stop the server to prevent data corruption.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/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
index 7862caa0f787634cec14af81fe1f39803a43f115..1650541abeedce04ddeddfed15411b64a01be452 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
@@ -124,8 +124,20 @@ public class ChunkSerializer {
         InProgressChunkHolder holder = loadChunk(world, poiStorage, chunkPos, nbt, true);
         return holder.protoChunk;
     }
+    // Paper start - Do not let the server load chunks from newer versions
+    private static final int CURRENT_DATA_VERSION = net.minecraft.SharedConstants.getCurrentVersion().getDataVersion().getVersion();
+    private static final boolean JUST_CORRUPT_IT = Boolean.getBoolean("Paper.ignoreWorldDataVersion");
+    // Paper end - Do not let the server load chunks from newer versions
 
     public static InProgressChunkHolder loadChunk(ServerLevel world, PoiManager poiStorage, ChunkPos chunkPos, CompoundTag nbt, boolean distinguish) {
+        // Paper start - Do not let the server load chunks from newer versions
+        if (nbt.contains("DataVersion", net.minecraft.nbt.Tag.TAG_ANY_NUMERIC)) {
+            int dataVersion = nbt.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
         ChunkPos chunkcoordintpair1 = new ChunkPos(nbt.getInt("xPos"), nbt.getInt("zPos")); // Paper - guard against serializing mismatching coordinates; diff on change, see ChunkSerializer#getChunkCoordinate