PaperMC/patches/server/1039-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 92848b64a78fce7a92e1657c2da6fc5ee53eea44..5d5562676a77259b875e15b744b53258533851a7 100644
--- a/src/main/java/com/mojang/brigadier/CommandDispatcher.java
+++ b/src/main/java/com/mojang/brigadier/CommandDispatcher.java
@@ -304,9 +304,15 @@ public class CommandDispatcher<S> {
             }
             final CommandContextBuilder<S> context = contextSoFar.copy();
             final StringReader reader = new StringReader(originalReader);
+            boolean stop = false; // Paper - Handle non-recoverable exceptions
             try {
                 try {
                     child.parse(reader, context);
+                    // Paper start - Handle non-recoverable exceptions
+                } catch (final com.mojang.brigadier.exceptions.TagParseCommandSyntaxException e) {
+                    stop = true;
+                    throw e;
+                    // Paper end - Handle non-recoverable exceptions
                 } catch (final RuntimeException ex) {
                     throw CommandSyntaxException.BUILT_IN_EXCEPTIONS.dispatcherParseException().createWithContext(reader, ex.getMessage());
                 }
@@ -321,6 +327,7 @@ public class CommandDispatcher<S> {
                 }
                 errors.put(child, ex);
                 reader.setCursor(cursor);
+                if (stop) return new ParseResults<>(contextSoFar, originalReader, errors); // Paper - Handle non-recoverable exceptions
                 continue;
             }
 
diff --git a/src/main/java/com/mojang/brigadier/exceptions/TagParseCommandSyntaxException.java b/src/main/java/com/mojang/brigadier/exceptions/TagParseCommandSyntaxException.java
new file mode 100644
index 0000000000000000000000000000000000000000..bf248a215dc69bb303c836112309471aab687e23
--- /dev/null
+++ b/src/main/java/com/mojang/brigadier/exceptions/TagParseCommandSyntaxException.java
@@ -0,0 +1,13 @@
+package com.mojang.brigadier.exceptions;
+
+import com.mojang.brigadier.LiteralMessage;
+import net.minecraft.network.chat.Component;
+
+public final class TagParseCommandSyntaxException extends CommandSyntaxException {
+
+    private static final SimpleCommandExceptionType EXCEPTION_TYPE = new SimpleCommandExceptionType(new LiteralMessage("Error parsing NBT"));
+
+    public TagParseCommandSyntaxException(final String message) {
+        super(EXCEPTION_TYPE, Component.literal(message));
+    }
+}
diff --git a/src/main/java/net/minecraft/nbt/TagParser.java b/src/main/java/net/minecraft/nbt/TagParser.java
index 5bec54239a2b185284c10d58854e5a13e33daae5..94cb73e7f60171aa57bd1dbe7e91ef4db94e70b7 100644
--- a/src/main/java/net/minecraft/nbt/TagParser.java
+++ b/src/main/java/net/minecraft/nbt/TagParser.java
@@ -48,6 +48,7 @@ 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();
@@ -156,6 +157,7 @@ public class TagParser {
 
     public CompoundTag readStruct() throws CommandSyntaxException {
         this.expect('{');
+        this.increaseDepth(); // Paper
         CompoundTag compoundTag = new CompoundTag();
         this.reader.skipWhitespace();
 
@@ -179,6 +181,7 @@ public class TagParser {
         }
 
         this.expect('}');
+        this.depth--; // Paper
         return compoundTag;
     }
 
@@ -188,6 +191,7 @@ 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;
 
@@ -213,6 +217,7 @@ public class TagParser {
             }
 
             this.expect(']');
+            this.depth--; // Paper
             return listTag;
         }
     }
@@ -251,11 +256,11 @@ 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()) {
@@ -286,4 +291,11 @@ public class TagParser {
         this.reader.skipWhitespace();
         this.reader.expect(c);
     }
+
+    private void increaseDepth() throws CommandSyntaxException {
+        this.depth++;
+        if (this.depth > 512) {
+            throw new com.mojang.brigadier.exceptions.TagParseCommandSyntaxException("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 a5e438a834826161c52ca9db57d234d9ff80a591..4766994cce060564370b0d24836a7da8b5e4a8a1 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ServerboundCommandSuggestionPacket.java
@@ -14,7 +14,7 @@ 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 2f9c62f2c4c4356a896f7004b77f12a595f9c6dc..ab5b259d8f72022c875cae73be25fe2da346c6b3 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -777,6 +777,13 @@ 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));
     }
@@ -824,6 +831,13 @@ 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-recoverable exceptions
+        if (!parseresults.getExceptions().isEmpty()
+            && parseresults.getExceptions().values().stream().anyMatch(e -> e instanceof com.mojang.brigadier.exceptions.TagParseCommandSyntaxException)) {
+            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM);
+            return;
+        }
+        // Paper end - Handle non-recoverable exceptions
 
         this.server.getCommands().getDispatcher().getCompletionSuggestions(parseresults).thenAccept((suggestions) -> {
             // Paper start - Don't tab-complete namespaced commands if send-namespaced is false