From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 15 Feb 2019 01:08:19 -0500
Subject: [PATCH] Allow Saving of Oversized Chunks

The Minecraft World Region File format has a hard cap of 1MB per chunk.
This is due to the fact that the header of the file format only allocates
a single byte for sector count, meaning a maximum of 256 sectors, at 4k per sector.

This limit can be reached fairly easily with books, resulting in the chunk being unable
to save to the world. Worse off, is that nothing printed when this occured, and silently
performed a chunk rollback on next load.

This leads to security risk with duplication and is being actively exploited.

This patch catches the too large scenario, falls back and moves any large Entity
or Tile Entity into a new compound, and this compound is saved into a different file.

On Chunk Load, we check for oversized status, and if so, we load the extra file and
merge the Entities and Tile Entities from the oversized chunk back into the level to
then be loaded as normal.

Once a chunk is returned back to normal size, the oversized flag will clear, and no
extra data file will exist.

This fix maintains compatability with all existing Anvil Region Format tools as it
does not alter the save format. They will just not know about the extra entities.

This fix also maintains compatability if someone switches server jars to one without
this fix, as the data will remain in the oversized file. Once the server returns
to a jar with this fix, the data will be restored.

diff --git a/src/main/java/net/minecraft/server/NBTCompressedStreamTools.java b/src/main/java/net/minecraft/server/NBTCompressedStreamTools.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/NBTCompressedStreamTools.java
+++ b/src/main/java/net/minecraft/server/NBTCompressedStreamTools.java
@@ -0,0 +0,0 @@ public class NBTCompressedStreamTools {
 
     }
 
+    public static NBTTagCompound readNBT(DataInputStream datainputstream) throws IOException { return a(datainputstream); } // Paper - OBFHELPER
     public static NBTTagCompound a(DataInputStream datainputstream) throws IOException {
         return a((DataInput) datainputstream, NBTReadLimiter.a);
     }
@@ -0,0 +0,0 @@ public class NBTCompressedStreamTools {
         }
     }
 
+    public static void writeNBT(NBTTagCompound nbttagcompound, DataOutput dataoutput) throws IOException { a(nbttagcompound, dataoutput); } // Paper - OBFHELPER
     public static void a(NBTTagCompound nbttagcompound, DataOutput dataoutput) throws IOException {
         a((NBTBase) nbttagcompound, dataoutput);
     }
diff --git a/src/main/java/net/minecraft/server/RegionFile.java b/src/main/java/net/minecraft/server/RegionFile.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/RegionFile.java
+++ b/src/main/java/net/minecraft/server/RegionFile.java
@@ -0,0 +0,0 @@ import java.nio.file.Files;
 import java.nio.file.LinkOption;
 import java.nio.file.StandardCopyOption;
 import java.nio.file.StandardOpenOption;
+import java.util.zip.InflaterInputStream; // Paper
+
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -0,0 +0,0 @@ public class RegionFile implements AutoCloseable {
     private final IntBuffer g;
     private final IntBuffer h;
     private final RegionFileBitSet freeSectors;
+    public final File file;
 
     public RegionFile(File file, File file1, boolean flag) throws IOException {
         this(file.toPath(), file1.toPath(), RegionFileCompression.b, flag);
     }
 
     public RegionFile(java.nio.file.Path java_nio_file_path, java.nio.file.Path java_nio_file_path1, RegionFileCompression regionfilecompression, boolean flag) throws IOException {
+        this.file = java_nio_file_path.toFile(); // Paper
         this.f = ByteBuffer.allocateDirect(8192);
+        initOversizedState();
         this.freeSectors = new RegionFileBitSet();
         this.e = regionfilecompression;
         if (!Files.isDirectory(java_nio_file_path1, new LinkOption[0])) {
@@ -0,0 +0,0 @@ public class RegionFile implements AutoCloseable {
         void run() throws IOException;
     }
 
+    private final byte[] oversized = new byte[1024];
+    private int oversizedCount = 0;
+
+    private synchronized void initOversizedState() throws IOException {
+        File metaFile = getOversizedMetaFile();
+        if (metaFile.exists()) {
+            final byte[] read = java.nio.file.Files.readAllBytes(metaFile.toPath());
+            System.arraycopy(read, 0, oversized, 0, oversized.length);
+            for (byte temp : oversized) {
+                oversizedCount += temp;
+            }
+        }
+    }
+
+    private static int getChunkIndex(int x, int z) {
+        return (x & 31) + (z & 31) * 32;
+    }
+    synchronized boolean isOversized(int x, int z) {
+        return this.oversized[getChunkIndex(x, z)] == 1;
+    }
+    synchronized void setOversized(int x, int z, boolean oversized) throws IOException {
+        final int offset = getChunkIndex(x, z);
+        boolean previous = this.oversized[offset] == 1;
+        this.oversized[offset] = (byte) (oversized ? 1 : 0);
+        if (!previous && oversized) {
+            oversizedCount++;
+        } else if (!oversized && previous) {
+            oversizedCount--;
+        }
+        if (previous && !oversized) {
+            File oversizedFile = getOversizedFile(x, z);
+            if (oversizedFile.exists()) {
+                oversizedFile.delete();
+            }
+        }
+        if (oversizedCount > 0) {
+            if (previous != oversized) {
+                writeOversizedMeta();
+            }
+        } else if (previous) {
+            File oversizedMetaFile = getOversizedMetaFile();
+            if (oversizedMetaFile.exists()) {
+                oversizedMetaFile.delete();
+            }
+        }
+    }
+
+    private void writeOversizedMeta() throws IOException {
+        java.nio.file.Files.write(getOversizedMetaFile().toPath(), oversized);
+    }
+
+    private File getOversizedMetaFile() {
+        return new File(this.file.getParentFile(), this.file.getName().replaceAll("\\.mca$", "") + ".oversized.nbt");
+    }
+
+    private File getOversizedFile(int x, int z) {
+        return new File(this.file.getParentFile(), this.file.getName().replaceAll("\\.mca$", "") + "_oversized_" + x + "_" + z + ".nbt");
+    }
+
+    synchronized NBTTagCompound getOversizedData(int x, int z) throws IOException {
+        File file = getOversizedFile(x, z);
+        try (DataInputStream out = new DataInputStream(new BufferedInputStream(new InflaterInputStream(new java.io.FileInputStream(file))))) {
+            return NBTCompressedStreamTools.readNBT(out);
+        }
+
+    }
+    // Paper end
+
     class ChunkBuffer extends ByteArrayOutputStream {
 
         private final ChunkCoordIntPair b;
diff --git a/src/main/java/net/minecraft/server/RegionFileCache.java b/src/main/java/net/minecraft/server/RegionFileCache.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/RegionFileCache.java
+++ b/src/main/java/net/minecraft/server/RegionFileCache.java
@@ -0,0 +0,0 @@ public final class RegionFileCache implements AutoCloseable {
         }
     }
 
+    // Paper start
+    private static void printOversizedLog(String msg, File file, int x, int z) {
+        org.apache.logging.log4j.LogManager.getLogger().fatal(msg + " (" + file.toString().replaceAll(".+[\\\\/]", "") + " - " + x + "," + z + ") Go clean it up to remove this message. /minecraft:tp " + (x<<4)+" 128 "+(z<<4) + " - DO NOT REPORT THIS TO PAPER - You may ask for help on Discord, but do not file an issue. These error messages can not be removed.");
+    }
+
+    private static final int DEFAULT_SIZE_THRESHOLD = 1024 * 8;
+    private static final int OVERZEALOUS_TOTAL_THRESHOLD = 1024 * 64;
+    private static final int OVERZEALOUS_THRESHOLD = 1024;
+    private static int SIZE_THRESHOLD = DEFAULT_SIZE_THRESHOLD;
+    private static void resetFilterThresholds() {
+        SIZE_THRESHOLD = Math.max(1024 * 4, Integer.getInteger("Paper.FilterThreshhold", DEFAULT_SIZE_THRESHOLD));
+    }
+    static {
+        resetFilterThresholds();
+    }
+
+    static boolean isOverzealous() {
+        return SIZE_THRESHOLD == OVERZEALOUS_THRESHOLD;
+    }
+
+
+    private static NBTTagCompound readOversizedChunk(RegionFile regionfile, ChunkCoordIntPair chunkCoordinate) throws IOException {
+        synchronized (regionfile) {
+            try (DataInputStream datainputstream = regionfile.getReadStream(chunkCoordinate)) {
+                NBTTagCompound oversizedData = regionfile.getOversizedData(chunkCoordinate.x, chunkCoordinate.z);
+                NBTTagCompound chunk = NBTCompressedStreamTools.readNBT(datainputstream);
+                if (oversizedData == null) {
+                    return chunk;
+                }
+                NBTTagCompound oversizedLevel = oversizedData.getCompound("Level");
+                NBTTagCompound level = chunk.getCompound("Level");
+
+                mergeChunkList(level, oversizedLevel, "Entities");
+                mergeChunkList(level, oversizedLevel, "TileEntities");
+
+                chunk.set("Level", level);
+
+                return chunk;
+            } catch (Throwable throwable) {
+                throwable.printStackTrace();
+                throw throwable;
+            }
+        }
+    }
+
+    private static void mergeChunkList(NBTTagCompound level, NBTTagCompound oversizedLevel, String key) {
+        NBTTagList levelList = level.getList(key, 10);
+        NBTTagList oversizedList = oversizedLevel.getList(key, 10);
+
+        if (!oversizedList.isEmpty()) {
+            levelList.addAll(oversizedList);
+            level.set(key, levelList);
+        }
+    }
+
+    private static int getNBTSize(NBTBase nbtBase) {
+        DataOutputStream test = new DataOutputStream(new org.apache.commons.io.output.NullOutputStream());
+        try {
+            nbtBase.write(test);
+            return test.size();
+        } catch (IOException e) {
+            e.printStackTrace();
+            return 0;
+        }
+    }
+
+    // Paper End
+
     @Nullable
     public NBTTagCompound read(ChunkCoordIntPair chunkcoordintpair) throws IOException {
         // CraftBukkit start - SPIGOT-5680: There's no good reason to preemptively create files on read, save that for writing
@@ -0,0 +0,0 @@ public final class RegionFileCache implements AutoCloseable {
         }
         // CraftBukkit end
         DataInputStream datainputstream = regionfile.a(chunkcoordintpair);
+        // Paper start
+        if (regionfile.isOversized(chunkcoordintpair.x, chunkcoordintpair.z)) {
+            printOversizedLog("Loading Oversized Chunk!", regionfile.file, chunkcoordintpair.x, chunkcoordintpair.z);
+            return readOversizedChunk(regionfile, chunkcoordintpair);
+        }
+        // Paper end
         Throwable throwable = null;
 
         NBTTagCompound nbttagcompound;
@@ -0,0 +0,0 @@ public final class RegionFileCache implements AutoCloseable {
 
         try {
             NBTCompressedStreamTools.a(nbttagcompound, (DataOutput) dataoutputstream);
+            regionfile.setOversized(chunkcoordintpair.x, chunkcoordintpair.z, false); // We don't do this anymore
         } catch (Throwable throwable1) {
             throwable = throwable1;
             throw throwable1;
