Add protection against large network channel lists

src/main/java/net/minecraftforge/client/ClientCommandHandler.java

@@ -107,7 +107,11 @@ public class ClientCommandHandler {
             new CommandSource() {
                 @Override
                 public void sendSystemMessage(Component message) {
-                    mc.gui.hud.getChat().addClientSystemMessage(message);
+                	var chat = mc.gui.hud.getChat();
+                	if (mc.isSameThread())
+                		chat.addClientSystemMessage(message);
+                	else
+                		mc.execute(() -> chat.addClientSystemMessage(message));
                 }
 
                 @Override

src/main/java/net/minecraftforge/common/ForgeConfig.java

@@ -75,6 +75,7 @@ public class ForgeConfig {
         }
 
         public final ForgeConfigSpec.EnumValue<MigrationHelperMode> migrationHelperMode;
+        public final ForgeConfigSpec.LongValue channelListLimit;
 
         Common(ForgeConfigSpec.Builder builder) {
             builder.comment("General configuration settings")
@@ -85,6 +86,17 @@ public class ForgeConfig {
                     .translation("forge.configgui.migrationHelperMode")
                     .defineEnum("logLegacyTagWarnings", MigrationHelperMode.OFF);
 
+            channelListLimit = builder
+        		.comment(
+    				"Maximum size to use to store the channel list for a network connection.",
+    				"The other end of the connection may send as many channels as it wishes.",
+    				"Some malicious actors may use this to use up all your memory causing OutOfMemoryException",
+    				"A sane default is 1KB (1024), but may need to be expanded for larger modpacks.",
+    				"Forge will auto-adjust this if mods register their channels using our channel manager."
+				)
+        		.translation("forge.configui.channellistlimit")
+        		.defineInRange("channelListLimit", 1024, 1, Long.MAX_VALUE);
+
             builder.pop();
         }
     }

src/main/java/net/minecraftforge/network/ChannelListManager.java

@@ -9,9 +9,11 @@ import com.mojang.logging.LogUtils;
 import net.minecraft.IdentifierException;
 import net.minecraft.network.Connection;
 import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.network.chat.Component;
 import net.minecraft.network.codec.StreamCodec;
 import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
 import net.minecraft.resources.Identifier;
+import net.minecraftforge.common.ForgeConfig;
 import net.minecraftforge.event.ForgeEventFactory;
 import net.minecraftforge.event.network.ChannelRegistrationChangeEvent;
 import net.minecraftforge.event.network.CustomPayloadEvent;
@@ -26,6 +28,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
+import java.util.stream.Collectors;
 
 @ApiStatus.Internal // TODO: Decide what I want to have public, Right now it should just be add/remove channels.
 public class ChannelListManager {
@@ -70,7 +73,7 @@ public class ChannelListManager {
     }
 
     private static void register(Register payload, CustomPayloadEvent.Context ctx) {
-        updateFrom(ctx, payload.channels(), ChannelRegistrationChangeEvent.Type.REGISTER);
+        updateFrom(ctx, payload.channels(), ChannelRegistrationChangeEvent.Type.REGISTER, ctx.isClientSide());
         ctx.setPacketHandled(true);
         // Send the client's channels to the server whenever asked. If we're in the login state then our login wrapper will unwrap for us.
         if (ctx.isClientSide())
@@ -78,7 +81,7 @@ public class ChannelListManager {
     }
 
     private static void unregister(Unregister payload, CustomPayloadEvent.Context ctx) {
-        updateFrom(ctx, payload.channels(), ChannelRegistrationChangeEvent.Type.UNREGISTER);
+        updateFrom(ctx, payload.channels(), ChannelRegistrationChangeEvent.Type.UNREGISTER, ctx.isClientSide());
         ctx.setPacketHandled(true);
     }
 
@@ -145,7 +148,7 @@ public class ChannelListManager {
         return Collections.unmodifiableList(channels);
     }
 
-    private static void updateFrom(CustomPayloadEvent.Context source, List<String> channels, final ChannelRegistrationChangeEvent.Type changeType) {
+    private static void updateFrom(CustomPayloadEvent.Context source, List<String> channels, final ChannelRegistrationChangeEvent.Type changeType, boolean isClient) {
         var changed = new HashSet<Identifier>();
         for (var channel : channels) {
             // It also says nothing about the format of channels so ignore bad channels.
@@ -162,11 +165,20 @@ public class ChannelListManager {
 
         ForgeEventFactory.onChannelRegistrationChange(source.getConnection(), changeType, changed);
 
+        // It is a known issue, that I don't really care about, that we don't get the true in-memory size of each channel due to character encoding.
+        // A sane limit of 1KB will be enough to catch any malicious actors even with non-8-bit strings.
         var list = NetworkContext.get(source.getConnection());
         for (var channel : changed) {
-            boolean fire = changeType == ChannelRegistrationChangeEvent.Type.UNREGISTER
-                ? list.remoteChannels.remove(channel)
-                : list.remoteChannels.add(channel);
+        	boolean fire = false;
+        	if (changeType == ChannelRegistrationChangeEvent.Type.UNREGISTER) {
+        		fire = list.remoteChannels.remove(channel);
+        		if (fire)
+        			list.remoteChannelsSize -= channel.toString().length();
+        	} else {
+        		fire = list.remoteChannels.add(channel);
+        		if (fire)
+        			list.remoteChannelsSize += channel.toString().length();
+        	}
 
             if (fire) {
                 var target = NetworkRegistry.findTarget(channel);
@@ -174,5 +186,21 @@ public class ChannelListManager {
                     target.registrationChange(channel, changeType == ChannelRegistrationChangeEvent.Type.REGISTER);
             }
         }
+
+        if (list.remoteChannelsSize >= NetworkRegistry.getChannelMemorySize() &&  list.remoteChannelsSize >= ForgeConfig.COMMON.channelListLimit.get()) {
+        	LOGGER.warn("Received too many network channels, {} channels using {} bytes, Limit is currently {}, to change edit the Forge {} in config\forge_common.toml",
+    			list.remoteChannels.size(), list.remoteChannelsSize, ForgeConfig.COMMON.channelListLimit.get(), ForgeConfig.COMMON.channelListLimit.getPath().stream().collect(Collectors.joining("."))
+			);
+
+        	if (isClient) {
+        		// We don't want to allow the server to screw with us, so just remove the added channels
+        		for (var channel : changed) {
+        			if (list.remoteChannels.remove(channel))
+        				list.remoteChannelsSize -= channel.toString().length();
+        		}
+        	} else {
+        		source.getSender().connection.disconnect(Component.translatable("forge.server.channellistlimit.kick"));
+        	}
+        }
     }
 }

src/main/java/net/minecraftforge/network/NetworkContext.java

@@ -111,6 +111,8 @@ public class NetworkContext {
 
     @ApiStatus.Internal
     Set<Identifier> remoteChannels = new HashSet<>();
+    @ApiStatus.Internal
+    long remoteChannelsSize = 0;
     private Set<Identifier> remoteChannelsView = Collections.unmodifiableSet(this.remoteChannels);
 
     @ApiStatus.Internal

src/main/java/net/minecraftforge/network/NetworkRegistry.java

@@ -43,6 +43,7 @@ public class NetworkRegistry {
 
     private static Map<Identifier, NetworkInstance> instances = Collections.synchronizedMap(new HashMap<>());
     private static Map<Identifier, NetworkInstance> byName = Collections.synchronizedMap(new HashMap<>());
+    private static long memorySize = 0;
 
     public static boolean acceptsVanillaClientConnections() {
         return listRejectedVanillaMods(n -> n.clientAcceptedVersions).isEmpty() && DataPackRegistriesHooks.getSyncedCustomRegistries().isEmpty();
@@ -199,9 +200,14 @@ public class NetworkRegistry {
         if (NetworkRegistry.byName.containsKey(name))
             error("Payload name " + name + " already registered.");
 
+        memorySize += name.toString().length(); // This can fail if people don't use our api. So this is a best effort.
         byName.put(name, instance);
     }
 
+    static long getChannelMemorySize() {
+        return memorySize;
+    }
+
     static void register(NetworkInstance instance) {
         checkLock(instance);
 

src/main/resources/assets/forge/lang/en_us.json

@@ -200,6 +200,10 @@
   "forge.configgui.stabilizeDirectionGetNearest": "Stabilize Direction Get Nearest",
   "forge.configgui.stabilizeDirectionGetNearest.tooltip": "When enabled, a slightly biased Direction#getNearest calculation will be used to prevent normal fighting on 45 degree angle faces.",
 
+  "forge.configgui.channellistlimit": "Channel List Size Limit",
+  "forge.configgui.channellistlimit.tooltip": "Maximum size to use to store the channel list for a network connection. Some malicious actors may use this to use up all your memory. A sane default is 1KB (1024), but may need to be expanded for larger modpacks.",
+  "forge.server.channellistlimit.kick": "Received too many networking channels",
+
   "forge.controlsgui.shift": "SHIFT + %s",
   "forge.controlsgui.control": "CTRL + %s",
   "forge.controlsgui.control.mac": "CMD + %s",