PaperMC/patches/server/Improve-tag-parser-handling.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Nassim Jahnke <nassim@njahnke.dev>
Date: Mon, 5 Feb 2024 11:54:04 +0100
Subject: [PATCH] Improve tag parser handling


diff --git a/src/main/java/com/mojang/brigadier/CommandDispatcher.java b/src/main/java/com/mojang/brigadier/CommandDispatcher.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/com/mojang/brigadier/CommandDispatcher.java
+++ b/src/main/java/com/mojang/brigadier/CommandDispatcher.java
@@ -0,0 +0,0 @@ public class CommandDispatcher<S> {
             try {
                 try {
                     child.parse(reader, context);
+                    // Paper start - Handle non-reoverable exceptions; Rethrow NbtAccounterException so it can be caught properly and immediately
+                } catch (final net.minecraft.nbt.NbtAccounterException e) {
+                    throw e;
+                    // Paper end - Handle non-reoverable exceptions
                 } catch (final RuntimeException ex) {
                     throw CommandSyntaxException.BUILT_IN_EXCEPTIONS.dispatcherParseException().createWithContext(reader, ex.getMessage());
                 }
diff --git a/src/main/java/net/minecraft/nbt/TagParser.java b/src/main/java/net/minecraft/nbt/TagParser.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/nbt/TagParser.java
+++ b/src/main/java/net/minecraft/nbt/TagParser.java
@@ -0,0 +0,0 @@ public class TagParser {
         }
     }, CompoundTag::toString);
     private final StringReader reader;
+    private int depth; // Paper
 
     public static CompoundTag parseTag(String string) throws CommandSyntaxException {
         return (new TagParser(new StringReader(string))).readSingleStruct();
@@ -0,0 +0,0 @@ public class TagParser {
 
     public CompoundTag readStruct() throws CommandSyntaxException {
         this.expect('{');
+        this.increaseDepth(); // Paper
         CompoundTag compoundTag = new CompoundTag();
         this.reader.skipWhitespace();
 
@@ -0,0 +0,0 @@ public class TagParser {
         }
 
         this.expect('}');
+        this.depth--; // Paper
         return compoundTag;
     }
 
@@ -0,0 +0,0 @@ public class TagParser {
         if (!this.reader.canRead()) {
             throw ERROR_EXPECTED_VALUE.createWithContext(this.reader);
         } else {
+            this.increaseDepth(); // Paper
             ListTag listTag = new ListTag();
             TagType<?> tagType = null;
 
@@ -0,0 +0,0 @@ public class TagParser {
             }
 
             this.expect(']');
+            this.depth--; // Paper
             return listTag;
         }
     }
@@ -0,0 +0,0 @@ public class TagParser {
                 }
 
                 if (typeReader == ByteTag.TYPE) {
-                    list.add((T)((NumericTag)tag).getAsByte());
+                    list.add((T)((NumericTag)tag).getAsNumber()); // Paper - decompile fix
                 } else if (typeReader == LongTag.TYPE) {
-                    list.add((T)((NumericTag)tag).getAsLong());
+                    list.add((T)((NumericTag)tag).getAsNumber()); // Paper - decompile fix
                 } else {
-                    list.add((T)((NumericTag)tag).getAsInt());
+                    list.add((T)((NumericTag)tag).getAsNumber()); // Paper - decompile fix
                 }
 
                 if (this.hasElementSeparator()) {
@@ -0,0 +0,0 @@ public class TagParser {
         this.reader.skipWhitespace();
         this.reader.expect(c);
     }
+
+    private void increaseDepth() {
+        this.depth++;
+        if (this.depth > 512) {
+            throw new net.minecraft.nbt.NbtAccounterException("NBT tag is too complex, depth > 512");
+        }
+    }
 }
diff --git a/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java b/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java
@@ -0,0 +0,0 @@ public class ServerboundCommandSuggestionPacket implements Packet<ServerGamePack
 
     public ServerboundCommandSuggestionPacket(FriendlyByteBuf buf) {
         this.id = buf.readVarInt();
-        this.command = buf.readUtf(32500);
+        this.command = buf.readUtf(2048); // Paper
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -0,0 +0,0 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             return;
         }
         // Paper end - Don't suggest if tab-complete is disabled
+        // Paper start
+        final int index;
+        if (packet.getCommand().length() > 64 && ((index = packet.getCommand().indexOf(' ')) == -1 || index >= 64)) {
+            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM);
+            return;
+        }
+        // Paper end
         // Paper start - AsyncTabCompleteEvent
         TAB_COMPLETE_EXECUTOR.execute(() -> this.handleCustomCommandSuggestions0(packet));
     }
@@ -0,0 +0,0 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
     private void sendServerSuggestions(final ServerboundCommandSuggestionPacket packet, final StringReader stringreader) {
         // Paper end - AsyncTabCompleteEvent
-        ParseResults<CommandSourceStack> parseresults = this.server.getCommands().getDispatcher().parse(stringreader, this.player.createCommandSourceStack());
+        // Paper start - Handle non-reoverable exceptions
+        ParseResults<CommandSourceStack> parseresults;
+        try {
+            parseresults = this.server.getCommands().getDispatcher().parse(stringreader, this.player.createCommandSourceStack());
+        } catch (final Throwable e) { // This is fine:tm:
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.error("Exception parsing command", e);
+            }
+            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM);
+            return;
+        }
+        // Paper end - Handle non-reoverable exceptions
 
         this.server.getCommands().getDispatcher().getCompletionSuggestions(parseresults).thenAccept((suggestions) -> {
             // Paper start - Don't tab-complete namespaced commands if send-namespaced is false