Move anti xray classes to source

paper-server/src/main/java/io/papermc/paper/antixray/BitStorageReader.java

@@ -0,0 +1,51 @@
+package io.papermc.paper.antixray;
+
+public final class BitStorageReader {
+
+    private byte[] buffer;
+    private int bits;
+    private int mask;
+    private int longInBufferIndex;
+    private int bitInLongIndex;
+    private long current;
+
+    public void setBuffer(byte[] buffer) {
+        this.buffer = buffer;
+    }
+
+    public void setBits(int bits) {
+        this.bits = bits;
+        mask = (1 << bits) - 1;
+    }
+
+    public void setIndex(int index) {
+        longInBufferIndex = index;
+        bitInLongIndex = 0;
+        init();
+    }
+
+    private void init() {
+        if (buffer.length > longInBufferIndex + 7) {
+            current = ((((long) buffer[longInBufferIndex]) << 56)
+                | (((long) buffer[longInBufferIndex + 1] & 0xff) << 48)
+                | (((long) buffer[longInBufferIndex + 2] & 0xff) << 40)
+                | (((long) buffer[longInBufferIndex + 3] & 0xff) << 32)
+                | (((long) buffer[longInBufferIndex + 4] & 0xff) << 24)
+                | (((long) buffer[longInBufferIndex + 5] & 0xff) << 16)
+                | (((long) buffer[longInBufferIndex + 6] & 0xff) << 8)
+                | (((long) buffer[longInBufferIndex + 7] & 0xff)));
+        }
+    }
+
+    public int read() {
+        if (bitInLongIndex + bits > 64) {
+            bitInLongIndex = 0;
+            longInBufferIndex += 8;
+            init();
+        }
+
+        int value = (int) (current >>> bitInLongIndex) & mask;
+        bitInLongIndex += bits;
+        return value;
+    }
+}

paper-server/src/main/java/io/papermc/paper/antixray/BitStorageWriter.java

@@ -0,0 +1,79 @@
+package io.papermc.paper.antixray;
+
+public final class BitStorageWriter {
+
+    private byte[] buffer;
+    private int bits;
+    private long mask;
+    private int longInBufferIndex;
+    private int bitInLongIndex;
+    private long current;
+    private boolean dirty;
+
+    public void setBuffer(byte[] buffer) {
+        this.buffer = buffer;
+    }
+
+    public void setBits(int bits) {
+        this.bits = bits;
+        mask = (1L << bits) - 1;
+    }
+
+    public void setIndex(int index) {
+        longInBufferIndex = index;
+        bitInLongIndex = 0;
+        init();
+    }
+
+    private void init() {
+        if (buffer.length > longInBufferIndex + 7) {
+            current = ((((long) buffer[longInBufferIndex]) << 56)
+                | (((long) buffer[longInBufferIndex + 1] & 0xff) << 48)
+                | (((long) buffer[longInBufferIndex + 2] & 0xff) << 40)
+                | (((long) buffer[longInBufferIndex + 3] & 0xff) << 32)
+                | (((long) buffer[longInBufferIndex + 4] & 0xff) << 24)
+                | (((long) buffer[longInBufferIndex + 5] & 0xff) << 16)
+                | (((long) buffer[longInBufferIndex + 6] & 0xff) << 8)
+                | (((long) buffer[longInBufferIndex + 7] & 0xff)));
+        }
+
+        dirty = false;
+    }
+
+    public void flush() {
+        if (dirty && buffer.length > longInBufferIndex + 7) {
+            buffer[longInBufferIndex] = (byte) (current >> 56 & 0xff);
+            buffer[longInBufferIndex + 1] = (byte) (current >> 48 & 0xff);
+            buffer[longInBufferIndex + 2] = (byte) (current >> 40 & 0xff);
+            buffer[longInBufferIndex + 3] = (byte) (current >> 32 & 0xff);
+            buffer[longInBufferIndex + 4] = (byte) (current >> 24 & 0xff);
+            buffer[longInBufferIndex + 5] = (byte) (current >> 16 & 0xff);
+            buffer[longInBufferIndex + 6] = (byte) (current >> 8 & 0xff);
+            buffer[longInBufferIndex + 7] = (byte) (current & 0xff);
+        }
+    }
+
+    public void write(int value) {
+        if (bitInLongIndex + bits > 64) {
+            flush();
+            bitInLongIndex = 0;
+            longInBufferIndex += 8;
+            init();
+        }
+
+        current = current & ~(mask << bitInLongIndex) | (value & mask) << bitInLongIndex;
+        dirty = true;
+        bitInLongIndex += bits;
+    }
+
+    public void skip() {
+        bitInLongIndex += bits;
+
+        if (bitInLongIndex > 64) {
+            flush();
+            bitInLongIndex = bits;
+            longInBufferIndex += 8;
+            init();
+        }
+    }
+}

paper-server/src/main/java/io/papermc/paper/antixray/ChunkPacketBlockController.java

@@ -0,0 +1,45 @@
+package io.papermc.paper.antixray;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.network.protocol.game.ClientboundLevelChunkWithLightPacket;
+import net.minecraft.network.protocol.game.ServerboundPlayerActionPacket;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.level.ServerPlayerGameMode;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.LevelChunk;
+
+public class ChunkPacketBlockController {
+
+    public static final ChunkPacketBlockController NO_OPERATION_INSTANCE = new ChunkPacketBlockController();
+
+    protected ChunkPacketBlockController() {
+
+    }
+
+    public BlockState[] getPresetBlockStates(Level level, ChunkPos chunkPos, int chunkSectionY) {
+        return null;
+    }
+
+    public boolean shouldModify(ServerPlayer player, LevelChunk chunk) {
+        return false;
+    }
+
+    public ChunkPacketInfo<BlockState> getChunkPacketInfo(ClientboundLevelChunkWithLightPacket chunkPacket, LevelChunk chunk) {
+        return null;
+    }
+
+    public void modifyBlocks(ClientboundLevelChunkWithLightPacket chunkPacket, ChunkPacketInfo<BlockState> chunkPacketInfo) {
+        chunkPacket.setReady(true);
+    }
+
+    public void onBlockChange(Level level, BlockPos blockPos, BlockState newBlockState, BlockState oldBlockState, int flags, int maxUpdateDepth) {
+
+    }
+
+    public void onPlayerLeftClickBlock(ServerPlayerGameMode serverPlayerGameMode, BlockPos blockPos, ServerboundPlayerActionPacket.Action action, Direction direction, int worldHeight, int sequence) {
+
+    }
+}

paper-server/src/main/java/io/papermc/paper/antixray/ChunkPacketBlockControllerAntiXray.java

@@ -0,0 +1,676 @@
+package io.papermc.paper.antixray;
+
+import io.papermc.paper.configuration.WorldConfiguration;
+import io.papermc.paper.configuration.type.EngineMode;
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.IntSupplier;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.network.protocol.game.ClientboundLevelChunkWithLightPacket;
+import net.minecraft.network.protocol.game.ServerboundPlayerActionPacket;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.level.ServerPlayerGameMode;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.EmptyLevelChunk;
+import net.minecraft.world.level.chunk.GlobalPalette;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.MissingPaletteEntryException;
+import net.minecraft.world.level.chunk.Palette;
+import org.bukkit.Bukkit;
+
+public final class ChunkPacketBlockControllerAntiXray extends ChunkPacketBlockController {
+
+    private static final Palette<BlockState> GLOBAL_BLOCKSTATE_PALETTE = new GlobalPalette<>(Block.BLOCK_STATE_REGISTRY);
+    private static final LevelChunkSection EMPTY_SECTION = null;
+    private final Executor executor;
+    private final EngineMode engineMode;
+    private final int maxBlockHeight;
+    private final int updateRadius;
+    private final boolean usePermission;
+    private final BlockState[] presetBlockStates;
+    private final BlockState[] presetBlockStatesFull;
+    private final BlockState[] presetBlockStatesStone;
+    private final BlockState[] presetBlockStatesDeepslate;
+    private final BlockState[] presetBlockStatesNetherrack;
+    private final BlockState[] presetBlockStatesEndStone;
+    private final int[] presetBlockStateBitsGlobal;
+    private final int[] presetBlockStateBitsStoneGlobal;
+    private final int[] presetBlockStateBitsDeepslateGlobal;
+    private final int[] presetBlockStateBitsNetherrackGlobal;
+    private final int[] presetBlockStateBitsEndStoneGlobal;
+    private final boolean[] solidGlobal = new boolean[Block.BLOCK_STATE_REGISTRY.size()];
+    private final boolean[] obfuscateGlobal = new boolean[Block.BLOCK_STATE_REGISTRY.size()];
+    private final LevelChunkSection[] emptyNearbyChunkSections = {EMPTY_SECTION, EMPTY_SECTION, EMPTY_SECTION, EMPTY_SECTION};
+    private final int maxBlockHeightUpdatePosition;
+
+    public ChunkPacketBlockControllerAntiXray(Level level, Executor executor) {
+        this.executor = executor;
+        WorldConfiguration.Anticheat.AntiXray paperWorldConfig = level.paperConfig().anticheat.antiXray;
+        engineMode = paperWorldConfig.engineMode;
+        maxBlockHeight = paperWorldConfig.maxBlockHeight >> 4 << 4;
+        updateRadius = paperWorldConfig.updateRadius;
+        usePermission = paperWorldConfig.usePermission;
+        List<Block> toObfuscate;
+
+        if (engineMode == EngineMode.HIDE) {
+            toObfuscate = paperWorldConfig.hiddenBlocks;
+            presetBlockStates = null;
+            presetBlockStatesFull = null;
+            presetBlockStatesStone = new BlockState[]{Blocks.STONE.defaultBlockState()};
+            presetBlockStatesDeepslate = new BlockState[]{Blocks.DEEPSLATE.defaultBlockState()};
+            presetBlockStatesNetherrack = new BlockState[]{Blocks.NETHERRACK.defaultBlockState()};
+            presetBlockStatesEndStone = new BlockState[]{Blocks.END_STONE.defaultBlockState()};
+            presetBlockStateBitsGlobal = null;
+            presetBlockStateBitsStoneGlobal = new int[]{GLOBAL_BLOCKSTATE_PALETTE.idFor(Blocks.STONE.defaultBlockState())};
+            presetBlockStateBitsDeepslateGlobal = new int[]{GLOBAL_BLOCKSTATE_PALETTE.idFor(Blocks.DEEPSLATE.defaultBlockState())};
+            presetBlockStateBitsNetherrackGlobal = new int[]{GLOBAL_BLOCKSTATE_PALETTE.idFor(Blocks.NETHERRACK.defaultBlockState())};
+            presetBlockStateBitsEndStoneGlobal = new int[]{GLOBAL_BLOCKSTATE_PALETTE.idFor(Blocks.END_STONE.defaultBlockState())};
+        } else {
+            toObfuscate = new ArrayList<>(paperWorldConfig.replacementBlocks);
+            List<BlockState> presetBlockStateList = new LinkedList<>();
+
+            for (Block block : paperWorldConfig.hiddenBlocks) {
+
+                if (!(block instanceof EntityBlock)) {
+                    toObfuscate.add(block);
+                    presetBlockStateList.add(block.defaultBlockState());
+                }
+            }
+
+            // The doc of the LinkedHashSet(Collection<? extends E>) constructor doesn't specify that the insertion order is the predictable iteration order of the specified Collection, although it is in the implementation
+            Set<BlockState> presetBlockStateSet = new LinkedHashSet<>();
+            // Therefore addAll(Collection<? extends E>) is used, which guarantees this order in the doc
+            presetBlockStateSet.addAll(presetBlockStateList);
+            presetBlockStates = presetBlockStateSet.isEmpty() ? new BlockState[]{Blocks.DIAMOND_ORE.defaultBlockState()} : presetBlockStateSet.toArray(new BlockState[0]);
+            presetBlockStatesFull = presetBlockStateSet.isEmpty() ? new BlockState[]{Blocks.DIAMOND_ORE.defaultBlockState()} : presetBlockStateList.toArray(new BlockState[0]);
+            presetBlockStatesStone = null;
+            presetBlockStatesDeepslate = null;
+            presetBlockStatesNetherrack = null;
+            presetBlockStatesEndStone = null;
+            presetBlockStateBitsGlobal = new int[presetBlockStatesFull.length];
+
+            for (int i = 0; i < presetBlockStatesFull.length; i++) {
+                presetBlockStateBitsGlobal[i] = GLOBAL_BLOCKSTATE_PALETTE.idFor(presetBlockStatesFull[i]);
+            }
+
+            presetBlockStateBitsStoneGlobal = null;
+            presetBlockStateBitsDeepslateGlobal = null;
+            presetBlockStateBitsNetherrackGlobal = null;
+            presetBlockStateBitsEndStoneGlobal = null;
+        }
+
+        for (Block block : toObfuscate) {
+
+            // Don't obfuscate air because air causes unnecessary block updates and causes block updates to fail in the void
+            if (block != null && !block.defaultBlockState().isAir()) {
+                // Replace all block states of a specified block
+                for (BlockState blockState : block.getStateDefinition().getPossibleStates()) {
+                    obfuscateGlobal[GLOBAL_BLOCKSTATE_PALETTE.idFor(blockState)] = true;
+                }
+            }
+        }
+
+        EmptyLevelChunk emptyChunk = new EmptyLevelChunk(level, new ChunkPos(0, 0), MinecraftServer.getServer().registryAccess().lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.PLAINS));
+        BlockPos zeroPos = new BlockPos(0, 0, 0);
+
+        for (int i = 0; i < solidGlobal.length; i++) {
+            BlockState blockState = GLOBAL_BLOCKSTATE_PALETTE.valueFor(i);
+
+            if (blockState != null) {
+                solidGlobal[i] = blockState.isRedstoneConductor(emptyChunk, zeroPos)
+                    && blockState.getBlock() != Blocks.SPAWNER && blockState.getBlock() != Blocks.BARRIER && blockState.getBlock() != Blocks.SHULKER_BOX && blockState.getBlock() != Blocks.SLIME_BLOCK && blockState.getBlock() != Blocks.MANGROVE_ROOTS || paperWorldConfig.lavaObscures && blockState == Blocks.LAVA.defaultBlockState();
+                // Comparing blockState == Blocks.LAVA.defaultBlockState() instead of blockState.getBlock() == Blocks.LAVA ensures that only "stationary lava" is used
+                // shulker box checks TE.
+            }
+        }
+
+        maxBlockHeightUpdatePosition = maxBlockHeight + updateRadius - 1;
+    }
+
+    private int getPresetBlockStatesFullLength() {
+        return engineMode == EngineMode.HIDE ? 1 : presetBlockStatesFull.length;
+    }
+
+    @Override
+    public BlockState[] getPresetBlockStates(Level level, ChunkPos chunkPos, int chunkSectionY) {
+        // Return the block states to be added to the paletted containers so that they can be used for obfuscation
+        int bottomBlockY = chunkSectionY << 4;
+
+        if (bottomBlockY < maxBlockHeight) {
+            if (engineMode == EngineMode.HIDE) {
+                return switch (level.getWorld().getEnvironment()) {
+                    case NETHER -> presetBlockStatesNetherrack;
+                    case THE_END -> presetBlockStatesEndStone;
+                    default -> bottomBlockY < 0 ? presetBlockStatesDeepslate : presetBlockStatesStone;
+                };
+            }
+
+            return presetBlockStates;
+        }
+
+        return null;
+    }
+
+    @Override
+    public boolean shouldModify(ServerPlayer player, LevelChunk chunk) {
+        return !usePermission || !player.getBukkitEntity().hasPermission("paper.antixray.bypass");
+    }
+
+    @Override
+    public ChunkPacketInfoAntiXray getChunkPacketInfo(ClientboundLevelChunkWithLightPacket chunkPacket, LevelChunk chunk) {
+        // Return a new instance to collect data and objects in the right state while creating the chunk packet for thread safe access later
+        return new ChunkPacketInfoAntiXray(chunkPacket, chunk, this);
+    }
+
+    @Override
+    public void modifyBlocks(ClientboundLevelChunkWithLightPacket chunkPacket, ChunkPacketInfo<BlockState> chunkPacketInfo) {
+        if (!(chunkPacketInfo instanceof ChunkPacketInfoAntiXray)) {
+            chunkPacket.setReady(true);
+            return;
+        }
+
+        if (!Bukkit.isPrimaryThread()) {
+            // Plugins?
+            MinecraftServer.getServer().scheduleOnMain(() -> modifyBlocks(chunkPacket, chunkPacketInfo));
+            return;
+        }
+
+        LevelChunk chunk = chunkPacketInfo.getChunk();
+        int x = chunk.getPos().x;
+        int z = chunk.getPos().z;
+        Level level = chunk.getLevel();
+        ((ChunkPacketInfoAntiXray) chunkPacketInfo).setNearbyChunks(level.getChunkIfLoaded(x - 1, z), level.getChunkIfLoaded(x + 1, z), level.getChunkIfLoaded(x, z - 1), level.getChunkIfLoaded(x, z + 1));
+        executor.execute((Runnable) chunkPacketInfo);
+    }
+
+    // Actually these fields should be variables inside the obfuscate method but in sync mode or with SingleThreadExecutor in async mode it's okay (even without ThreadLocal)
+    // If an ExecutorService with multiple threads is used, ThreadLocal must be used here
+    private final ThreadLocal<int[]> presetBlockStateBits = ThreadLocal.withInitial(() -> new int[getPresetBlockStatesFullLength()]);
+    private static final ThreadLocal<boolean[]> SOLID = ThreadLocal.withInitial(() -> new boolean[Block.BLOCK_STATE_REGISTRY.size()]);
+    private static final ThreadLocal<boolean[]> OBFUSCATE = ThreadLocal.withInitial(() -> new boolean[Block.BLOCK_STATE_REGISTRY.size()]);
+    // These boolean arrays represent chunk layers, true means don't obfuscate, false means obfuscate
+    private static final ThreadLocal<boolean[][]> CURRENT = ThreadLocal.withInitial(() -> new boolean[16][16]);
+    private static final ThreadLocal<boolean[][]> NEXT = ThreadLocal.withInitial(() -> new boolean[16][16]);
+    private static final ThreadLocal<boolean[][]> NEXT_NEXT = ThreadLocal.withInitial(() -> new boolean[16][16]);
+
+    public void obfuscate(ChunkPacketInfoAntiXray chunkPacketInfoAntiXray) {
+        int[] presetBlockStateBits = this.presetBlockStateBits.get();
+        boolean[] solid = SOLID.get();
+        boolean[] obfuscate = OBFUSCATE.get();
+        boolean[][] current = CURRENT.get();
+        boolean[][] next = NEXT.get();
+        boolean[][] nextNext = NEXT_NEXT.get();
+        // bitStorageReader, bitStorageWriter and nearbyChunkSections could also be reused (with ThreadLocal if necessary) but it's not worth it
+        BitStorageReader bitStorageReader = new BitStorageReader();
+        BitStorageWriter bitStorageWriter = new BitStorageWriter();
+        LevelChunkSection[] nearbyChunkSections = new LevelChunkSection[4];
+        LevelChunk chunk = chunkPacketInfoAntiXray.getChunk();
+        Level level = chunk.getLevel();
+        int maxChunkSectionIndex = Math.min((maxBlockHeight >> 4) - chunk.getMinSectionY(), chunk.getSectionsCount()) - 1;
+        boolean[] solidTemp = null;
+        boolean[] obfuscateTemp = null;
+        bitStorageReader.setBuffer(chunkPacketInfoAntiXray.getBuffer());
+        bitStorageWriter.setBuffer(chunkPacketInfoAntiXray.getBuffer());
+        int numberOfBlocks = presetBlockStateBits.length;
+        // Keep the lambda expressions as simple as possible. They are used very frequently.
+        LayeredIntSupplier random = numberOfBlocks == 1 ? (() -> 0) : engineMode == EngineMode.OBFUSCATE_LAYER ? new LayeredIntSupplier() {
+            // engine-mode: 3
+            private int state;
+            private int next;
+
+            {
+                while ((state = ThreadLocalRandom.current().nextInt()) == 0) ;
+            }
+
+            @Override
+            public void nextLayer() {
+                // https://en.wikipedia.org/wiki/Xorshift
+                state ^= state << 13;
+                state ^= state >>> 17;
+                state ^= state << 5;
+                // https://www.pcg-random.org/posts/bounded-rands.html
+                next = (int) ((Integer.toUnsignedLong(state) * numberOfBlocks) >>> 32);
+            }
+
+            @Override
+            public int getAsInt() {
+                return next;
+            }
+        } : new LayeredIntSupplier() {
+            // engine-mode: 2
+            private int state;
+
+            {
+                while ((state = ThreadLocalRandom.current().nextInt()) == 0) ;
+            }
+
+            @Override
+            public int getAsInt() {
+                // https://en.wikipedia.org/wiki/Xorshift
+                state ^= state << 13;
+                state ^= state >>> 17;
+                state ^= state << 5;
+                // https://www.pcg-random.org/posts/bounded-rands.html
+                return (int) ((Integer.toUnsignedLong(state) * numberOfBlocks) >>> 32);
+            }
+        };
+
+        for (int chunkSectionIndex = 0; chunkSectionIndex <= maxChunkSectionIndex; chunkSectionIndex++) {
+            if (chunkPacketInfoAntiXray.isWritten(chunkSectionIndex) && chunkPacketInfoAntiXray.getPresetValues(chunkSectionIndex) != null) {
+                int[] presetBlockStateBitsTemp;
+
+                if (chunkPacketInfoAntiXray.getPalette(chunkSectionIndex) instanceof GlobalPalette) {
+                    if (engineMode == EngineMode.HIDE) {
+                        presetBlockStateBitsTemp = switch (level.getWorld().getEnvironment()) {
+                            case NETHER -> presetBlockStateBitsNetherrackGlobal;
+                            case THE_END -> presetBlockStateBitsEndStoneGlobal;
+                            default -> chunkSectionIndex + chunk.getMinSectionY() < 0 ? presetBlockStateBitsDeepslateGlobal : presetBlockStateBitsStoneGlobal;
+                        };
+                    } else {
+                        presetBlockStateBitsTemp = presetBlockStateBitsGlobal;
+                    }
+                } else {
+                    // If it's presetBlockStates, use this.presetBlockStatesFull instead
+                    BlockState[] presetBlockStatesFull = chunkPacketInfoAntiXray.getPresetValues(chunkSectionIndex) == presetBlockStates ? this.presetBlockStatesFull : chunkPacketInfoAntiXray.getPresetValues(chunkSectionIndex);
+                    presetBlockStateBitsTemp = presetBlockStateBits;
+
+                    for (int i = 0; i < presetBlockStateBitsTemp.length; i++) {
+                        // This is thread safe because we only request IDs that are guaranteed to be in the palette and are visible
+                        // For more details see the comments in the readPalette method
+                        presetBlockStateBitsTemp[i] = chunkPacketInfoAntiXray.getPalette(chunkSectionIndex).idFor(presetBlockStatesFull[i]);
+                    }
+                }
+
+                bitStorageWriter.setIndex(chunkPacketInfoAntiXray.getIndex(chunkSectionIndex));
+
+                // Check if the chunk section below was not obfuscated
+                if (chunkSectionIndex == 0 || !chunkPacketInfoAntiXray.isWritten(chunkSectionIndex - 1) || chunkPacketInfoAntiXray.getPresetValues(chunkSectionIndex - 1) == null) {
+                    // If so, initialize some stuff
+                    bitStorageReader.setBits(chunkPacketInfoAntiXray.getBits(chunkSectionIndex));
+                    bitStorageReader.setIndex(chunkPacketInfoAntiXray.getIndex(chunkSectionIndex));
+                    solidTemp = readPalette(chunkPacketInfoAntiXray.getPalette(chunkSectionIndex), solid, solidGlobal);
+                    obfuscateTemp = readPalette(chunkPacketInfoAntiXray.getPalette(chunkSectionIndex), obfuscate, obfuscateGlobal);
+                    // Read the blocks of the upper layer of the chunk section below if it exists
+                    LevelChunkSection belowChunkSection = null;
+                    boolean skipFirstLayer = chunkSectionIndex == 0 || (belowChunkSection = chunk.getSections()[chunkSectionIndex - 1]) == EMPTY_SECTION;
+
+                    for (int z = 0; z < 16; z++) {
+                        for (int x = 0; x < 16; x++) {
+                            current[z][x] = true;
+                            next[z][x] = skipFirstLayer || isTransparent(belowChunkSection, x, 15, z);
+                        }
+                    }
+
+                    // Abuse the obfuscateLayer method to read the blocks of the first layer of the current chunk section
+                    bitStorageWriter.setBits(0);
+                    obfuscateLayer(-1, bitStorageReader, bitStorageWriter, solidTemp, obfuscateTemp, presetBlockStateBitsTemp, current, next, nextNext, emptyNearbyChunkSections, random);
+                }
+
+                bitStorageWriter.setBits(chunkPacketInfoAntiXray.getBits(chunkSectionIndex));
+                nearbyChunkSections[0] = chunkPacketInfoAntiXray.getNearbyChunks()[0] == null ? EMPTY_SECTION : chunkPacketInfoAntiXray.getNearbyChunks()[0].getSections()[chunkSectionIndex];
+                nearbyChunkSections[1] = chunkPacketInfoAntiXray.getNearbyChunks()[1] == null ? EMPTY_SECTION : chunkPacketInfoAntiXray.getNearbyChunks()[1].getSections()[chunkSectionIndex];
+                nearbyChunkSections[2] = chunkPacketInfoAntiXray.getNearbyChunks()[2] == null ? EMPTY_SECTION : chunkPacketInfoAntiXray.getNearbyChunks()[2].getSections()[chunkSectionIndex];
+                nearbyChunkSections[3] = chunkPacketInfoAntiXray.getNearbyChunks()[3] == null ? EMPTY_SECTION : chunkPacketInfoAntiXray.getNearbyChunks()[3].getSections()[chunkSectionIndex];
+
+                // Obfuscate all layers of the current chunk section except the upper one
+                for (int y = 0; y < 15; y++) {
+                    boolean[][] temp = current;
+                    current = next;
+                    next = nextNext;
+                    nextNext = temp;
+                    random.nextLayer();
+                    obfuscateLayer(y, bitStorageReader, bitStorageWriter, solidTemp, obfuscateTemp, presetBlockStateBitsTemp, current, next, nextNext, nearbyChunkSections, random);
+                }
+
+                // Check if the chunk section above doesn't need obfuscation
+                if (chunkSectionIndex == maxChunkSectionIndex || !chunkPacketInfoAntiXray.isWritten(chunkSectionIndex + 1) || chunkPacketInfoAntiXray.getPresetValues(chunkSectionIndex + 1) == null) {
+                    // If so, obfuscate the upper layer of the current chunk section by reading blocks of the first layer from the chunk section above if it exists
+                    LevelChunkSection aboveChunkSection;
+
+                    if (chunkSectionIndex != chunk.getSectionsCount() - 1 && (aboveChunkSection = chunk.getSections()[chunkSectionIndex + 1]) != EMPTY_SECTION) {
+                        boolean[][] temp = current;
+                        current = next;
+                        next = nextNext;
+                        nextNext = temp;
+
+                        for (int z = 0; z < 16; z++) {
+                            for (int x = 0; x < 16; x++) {
+                                if (isTransparent(aboveChunkSection, x, 0, z)) {
+                                    current[z][x] = true;
+                                }
+                            }
+                        }
+
+                        // There is nothing to read anymore
+                        bitStorageReader.setBits(0);
+                        solid[0] = true;
+                        random.nextLayer();
+                        obfuscateLayer(15, bitStorageReader, bitStorageWriter, solid, obfuscateTemp, presetBlockStateBitsTemp, current, next, nextNext, nearbyChunkSections, random);
+                    }
+                } else {
+                    // If not, initialize the reader and other stuff for the chunk section above to obfuscate the upper layer of the current chunk section
+                    bitStorageReader.setBits(chunkPacketInfoAntiXray.getBits(chunkSectionIndex + 1));
+                    bitStorageReader.setIndex(chunkPacketInfoAntiXray.getIndex(chunkSectionIndex + 1));
+                    solidTemp = readPalette(chunkPacketInfoAntiXray.getPalette(chunkSectionIndex + 1), solid, solidGlobal);
+                    obfuscateTemp = readPalette(chunkPacketInfoAntiXray.getPalette(chunkSectionIndex + 1), obfuscate, obfuscateGlobal);
+                    boolean[][] temp = current;
+                    current = next;
+                    next = nextNext;
+                    nextNext = temp;
+                    random.nextLayer();
+                    obfuscateLayer(15, bitStorageReader, bitStorageWriter, solidTemp, obfuscateTemp, presetBlockStateBitsTemp, current, next, nextNext, nearbyChunkSections, random);
+                }
+
+                bitStorageWriter.flush();
+            }
+        }
+
+        chunkPacketInfoAntiXray.getChunkPacket().setReady(true);
+    }
+
+    private void obfuscateLayer(int y, BitStorageReader bitStorageReader, BitStorageWriter bitStorageWriter, boolean[] solid, boolean[] obfuscate, int[] presetBlockStateBits, boolean[][] current, boolean[][] next, boolean[][] nextNext, LevelChunkSection[] nearbyChunkSections, IntSupplier random) {
+        // First block of first line
+        int bits = bitStorageReader.read();
+
+        if (nextNext[0][0] = !solid[bits]) {
+            bitStorageWriter.skip();
+            next[0][1] = true;
+            next[1][0] = true;
+        } else {
+            if (current[0][0] || isTransparent(nearbyChunkSections[2], 0, y, 15) || isTransparent(nearbyChunkSections[0], 15, y, 0)) {
+                bitStorageWriter.skip();
+            } else {
+                bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+            }
+        }
+
+        if (!obfuscate[bits]) {
+            next[0][0] = true;
+        }
+
+        // First line
+        for (int x = 1; x < 15; x++) {
+            bits = bitStorageReader.read();
+
+            if (nextNext[0][x] = !solid[bits]) {
+                bitStorageWriter.skip();
+                next[0][x - 1] = true;
+                next[0][x + 1] = true;
+                next[1][x] = true;
+            } else {
+                if (current[0][x] || isTransparent(nearbyChunkSections[2], x, y, 15)) {
+                    bitStorageWriter.skip();
+                } else {
+                    bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+                }
+            }
+
+            if (!obfuscate[bits]) {
+                next[0][x] = true;
+            }
+        }
+
+        // Last block of first line
+        bits = bitStorageReader.read();
+
+        if (nextNext[0][15] = !solid[bits]) {
+            bitStorageWriter.skip();
+            next[0][14] = true;
+            next[1][15] = true;
+        } else {
+            if (current[0][15] || isTransparent(nearbyChunkSections[2], 15, y, 15) || isTransparent(nearbyChunkSections[1], 0, y, 0)) {
+                bitStorageWriter.skip();
+            } else {
+                bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+            }
+        }
+
+        if (!obfuscate[bits]) {
+            next[0][15] = true;
+        }
+
+        // All inner lines
+        for (int z = 1; z < 15; z++) {
+            // First block
+            bits = bitStorageReader.read();
+
+            if (nextNext[z][0] = !solid[bits]) {
+                bitStorageWriter.skip();
+                next[z][1] = true;
+                next[z - 1][0] = true;
+                next[z + 1][0] = true;
+            } else {
+                if (current[z][0] || isTransparent(nearbyChunkSections[0], 15, y, z)) {
+                    bitStorageWriter.skip();
+                } else {
+                    bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+                }
+            }
+
+            if (!obfuscate[bits]) {
+                next[z][0] = true;
+            }
+
+            // All inner blocks
+            for (int x = 1; x < 15; x++) {
+                bits = bitStorageReader.read();
+
+                if (nextNext[z][x] = !solid[bits]) {
+                    bitStorageWriter.skip();
+                    next[z][x - 1] = true;
+                    next[z][x + 1] = true;
+                    next[z - 1][x] = true;
+                    next[z + 1][x] = true;
+                } else {
+                    if (current[z][x]) {
+                        bitStorageWriter.skip();
+                    } else {
+                        bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+                    }
+                }
+
+                if (!obfuscate[bits]) {
+                    next[z][x] = true;
+                }
+            }
+
+            // Last block
+            bits = bitStorageReader.read();
+
+            if (nextNext[z][15] = !solid[bits]) {
+                bitStorageWriter.skip();
+                next[z][14] = true;
+                next[z - 1][15] = true;
+                next[z + 1][15] = true;
+            } else {
+                if (current[z][15] || isTransparent(nearbyChunkSections[1], 0, y, z)) {
+                    bitStorageWriter.skip();
+                } else {
+                    bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+                }
+            }
+
+            if (!obfuscate[bits]) {
+                next[z][15] = true;
+            }
+        }
+
+        // First block of last line
+        bits = bitStorageReader.read();
+
+        if (nextNext[15][0] = !solid[bits]) {
+            bitStorageWriter.skip();
+            next[15][1] = true;
+            next[14][0] = true;
+        } else {
+            if (current[15][0] || isTransparent(nearbyChunkSections[3], 0, y, 0) || isTransparent(nearbyChunkSections[0], 15, y, 15)) {
+                bitStorageWriter.skip();
+            } else {
+                bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+            }
+        }
+
+        if (!obfuscate[bits]) {
+            next[15][0] = true;
+        }
+
+        // Last line
+        for (int x = 1; x < 15; x++) {
+            bits = bitStorageReader.read();
+
+            if (nextNext[15][x] = !solid[bits]) {
+                bitStorageWriter.skip();
+                next[15][x - 1] = true;
+                next[15][x + 1] = true;
+                next[14][x] = true;
+            } else {
+                if (current[15][x] || isTransparent(nearbyChunkSections[3], x, y, 0)) {
+                    bitStorageWriter.skip();
+                } else {
+                    bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+                }
+            }
+
+            if (!obfuscate[bits]) {
+                next[15][x] = true;
+            }
+        }
+
+        // Last block of last line
+        bits = bitStorageReader.read();
+
+        if (nextNext[15][15] = !solid[bits]) {
+            bitStorageWriter.skip();
+            next[15][14] = true;
+            next[14][15] = true;
+        } else {
+            if (current[15][15] || isTransparent(nearbyChunkSections[3], 15, y, 0) || isTransparent(nearbyChunkSections[1], 0, y, 15)) {
+                bitStorageWriter.skip();
+            } else {
+                bitStorageWriter.write(presetBlockStateBits[random.getAsInt()]);
+            }
+        }
+
+        if (!obfuscate[bits]) {
+            next[15][15] = true;
+        }
+    }
+
+    private boolean isTransparent(LevelChunkSection chunkSection, int x, int y, int z) {
+        if (chunkSection == EMPTY_SECTION) {
+            return true;
+        }
+
+        try {
+            return !solidGlobal[GLOBAL_BLOCKSTATE_PALETTE.idFor(chunkSection.getBlockState(x, y, z))];
+        } catch (MissingPaletteEntryException e) {
+            // Race condition / visibility issue / no happens-before relationship
+            // We don't care and treat the block as transparent
+            // Internal implementation details of PalettedContainer, LinearPalette, HashMapPalette, CrudeIncrementalIntIdentityHashBiMap, ... guarantee us that no (other) exceptions will occur
+            return true;
+        }
+    }
+
+    private boolean[] readPalette(Palette<BlockState> palette, boolean[] temp, boolean[] global) {
+        if (palette instanceof GlobalPalette) {
+            return global;
+        }
+
+        try {
+            for (int i = 0; i < palette.getSize(); i++) {
+                temp[i] = global[GLOBAL_BLOCKSTATE_PALETTE.idFor(palette.valueFor(i))];
+            }
+        } catch (MissingPaletteEntryException e) {
+            // Race condition / visibility issue / no happens-before relationship
+            // We don't care because we at least see the state as it was when the chunk packet was created
+            // Internal implementation details of PalettedContainer, LinearPalette, HashMapPalette, CrudeIncrementalIntIdentityHashBiMap, ... guarantee us that no (other) exceptions will occur until we have all the data that we need here
+            // Since all palettes have a fixed initial maximum size and there is no internal restructuring and no values are removed from palettes, we are also guaranteed to see the data
+        }
+
+        return temp;
+    }
+
+    @Override
+    public void onBlockChange(Level level, BlockPos blockPos, BlockState newBlockState, BlockState oldBlockState, int flags, int maxUpdateDepth) {
+        if (oldBlockState != null && solidGlobal[GLOBAL_BLOCKSTATE_PALETTE.idFor(oldBlockState)] && !solidGlobal[GLOBAL_BLOCKSTATE_PALETTE.idFor(newBlockState)] && blockPos.getY() <= maxBlockHeightUpdatePosition) {
+            updateNearbyBlocks(level, blockPos);
+        }
+    }
+
+    @Override
+    public void onPlayerLeftClickBlock(ServerPlayerGameMode serverPlayerGameMode, BlockPos blockPos, ServerboundPlayerActionPacket.Action action, Direction direction, int worldHeight, int sequence) {
+        if (blockPos.getY() <= maxBlockHeightUpdatePosition) {
+            updateNearbyBlocks(serverPlayerGameMode.level, blockPos);
+        }
+    }
+
+    private void updateNearbyBlocks(Level level, BlockPos blockPos) {
+        if (updateRadius >= 2) {
+            BlockPos temp = blockPos.west();
+            updateBlock(level, temp);
+            updateBlock(level, temp.west());
+            updateBlock(level, temp.below());
+            updateBlock(level, temp.above());
+            updateBlock(level, temp.north());
+            updateBlock(level, temp.south());
+            updateBlock(level, temp = blockPos.east());
+            updateBlock(level, temp.east());
+            updateBlock(level, temp.below());
+            updateBlock(level, temp.above());
+            updateBlock(level, temp.north());
+            updateBlock(level, temp.south());
+            updateBlock(level, temp = blockPos.below());
+            updateBlock(level, temp.below());
+            updateBlock(level, temp.north());
+            updateBlock(level, temp.south());
+            updateBlock(level, temp = blockPos.above());
+            updateBlock(level, temp.above());
+            updateBlock(level, temp.north());
+            updateBlock(level, temp.south());
+            updateBlock(level, temp = blockPos.north());
+            updateBlock(level, temp.north());
+            updateBlock(level, temp = blockPos.south());
+            updateBlock(level, temp.south());
+        } else if (updateRadius == 1) {
+            updateBlock(level, blockPos.west());
+            updateBlock(level, blockPos.east());
+            updateBlock(level, blockPos.below());
+            updateBlock(level, blockPos.above());
+            updateBlock(level, blockPos.north());
+            updateBlock(level, blockPos.south());
+        } else {
+            // Do nothing if updateRadius <= 0 (test mode)
+        }
+    }
+
+    private void updateBlock(Level level, BlockPos blockPos) {
+        BlockState blockState = level.getBlockStateIfLoaded(blockPos);
+
+        if (blockState != null && obfuscateGlobal[GLOBAL_BLOCKSTATE_PALETTE.idFor(blockState)]) {
+            ((ServerLevel) level).getChunkSource().blockChanged(blockPos);
+        }
+    }
+
+    @FunctionalInterface
+    private interface LayeredIntSupplier extends IntSupplier {
+        default void nextLayer() {
+
+        }
+    }
+}

paper-server/src/main/java/io/papermc/paper/antixray/ChunkPacketInfo.java

@@ -0,0 +1,80 @@
+package io.papermc.paper.antixray;
+
+import net.minecraft.network.protocol.game.ClientboundLevelChunkWithLightPacket;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.Palette;
+
+public class ChunkPacketInfo<T> {
+
+    private final ClientboundLevelChunkWithLightPacket chunkPacket;
+    private final LevelChunk chunk;
+    private final int[] bits;
+    private final Object[] palettes;
+    private final int[] indexes;
+    private final Object[][] presetValues;
+    private byte[] buffer;
+
+    public ChunkPacketInfo(ClientboundLevelChunkWithLightPacket chunkPacket, LevelChunk chunk) {
+        this.chunkPacket = chunkPacket;
+        this.chunk = chunk;
+        int sections = chunk.getSectionsCount();
+        bits = new int[sections];
+        palettes = new Object[sections];
+        indexes = new int[sections];
+        presetValues = new Object[sections][];
+    }
+
+    public ClientboundLevelChunkWithLightPacket getChunkPacket() {
+        return chunkPacket;
+    }
+
+    public LevelChunk getChunk() {
+        return chunk;
+    }
+
+    public byte[] getBuffer() {
+        return buffer;
+    }
+
+    public void setBuffer(byte[] buffer) {
+        this.buffer = buffer;
+    }
+
+    public int getBits(int chunkSectionIndex) {
+        return bits[chunkSectionIndex];
+    }
+
+    public void setBits(int chunkSectionIndex, int bits) {
+        this.bits[chunkSectionIndex] = bits;
+    }
+
+    @SuppressWarnings("unchecked")
+    public Palette<T> getPalette(int chunkSectionIndex) {
+        return (Palette<T>) palettes[chunkSectionIndex];
+    }
+
+    public void setPalette(int chunkSectionIndex, Palette<T> palette) {
+        palettes[chunkSectionIndex] = palette;
+    }
+
+    public int getIndex(int chunkSectionIndex) {
+        return indexes[chunkSectionIndex];
+    }
+
+    public void setIndex(int chunkSectionIndex, int index) {
+        indexes[chunkSectionIndex] = index;
+    }
+
+    @SuppressWarnings("unchecked")
+    public T[] getPresetValues(int chunkSectionIndex) {
+        return (T[]) presetValues[chunkSectionIndex];
+    }
+
+    public void setPresetValues(int chunkSectionIndex, T[] presetValues) {
+        this.presetValues[chunkSectionIndex] = presetValues;
+    }
+
+    public boolean isWritten(int chunkSectionIndex) {
+        return bits[chunkSectionIndex] != 0;
+    }
+}

paper-server/src/main/java/io/papermc/paper/antixray/ChunkPacketInfoAntiXray.java

@@ -0,0 +1,29 @@
+package io.papermc.paper.antixray;
+
+import net.minecraft.network.protocol.game.ClientboundLevelChunkWithLightPacket;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.LevelChunk;
+
+public final class ChunkPacketInfoAntiXray extends ChunkPacketInfo<BlockState> implements Runnable {
+
+    private final ChunkPacketBlockControllerAntiXray chunkPacketBlockControllerAntiXray;
+    private LevelChunk[] nearbyChunks;
+
+    public ChunkPacketInfoAntiXray(ClientboundLevelChunkWithLightPacket chunkPacket, LevelChunk chunk, ChunkPacketBlockControllerAntiXray chunkPacketBlockControllerAntiXray) {
+        super(chunkPacket, chunk);
+        this.chunkPacketBlockControllerAntiXray = chunkPacketBlockControllerAntiXray;
+    }
+
+    public LevelChunk[] getNearbyChunks() {
+        return nearbyChunks;
+    }
+
+    public void setNearbyChunks(LevelChunk... nearbyChunks) {
+        this.nearbyChunks = nearbyChunks;
+    }
+
+    @Override
+    public void run() {
+        chunkPacketBlockControllerAntiXray.obfuscate(this);
+    }
+}