From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 16 Nov 2018 23:08:50 -0500
Subject: [PATCH] Book size limits

Puts some limits on the size of books.

diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 2e35c6cfdf0cded5adc9f512612faaa68876961c..d69b678b2611f3d1b1ef64541863256868969671 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -1043,6 +1043,40 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
     @Override
     public void handleEditBook(ServerboundEditBookPacket packet) {
+        // Paper start - Book size limits
+        if (!this.cserver.isPrimaryThread()) {
+            List<String> pageList = packet.pages();
+            long byteTotal = 0;
+            int maxBookPageSize = io.papermc.paper.configuration.GlobalConfiguration.get().itemValidation.bookSize.pageMax;
+            double multiplier = Math.clamp(io.papermc.paper.configuration.GlobalConfiguration.get().itemValidation.bookSize.totalMultiplier, 0.3D, 1D);
+            long byteAllowed = maxBookPageSize;
+            for (String testString : pageList) {
+                int byteLength = testString.getBytes(java.nio.charset.StandardCharsets.UTF_8).length;
+                byteTotal += byteLength;
+                int length = testString.length();
+                int multibytes = 0;
+                if (byteLength != length) {
+                    for (char c : testString.toCharArray()) {
+                        if (c > 127) {
+                            multibytes++;
+                        }
+                    }
+                }
+                byteAllowed += maxBookPageSize * Math.clamp((double) length / 255D, 0.1D, 1) * multiplier;
+
+                if (multibytes > 1) {
+                    // penalize MB
+                    byteAllowed -= multibytes;
+                }
+            }
+
+            if (byteTotal > byteAllowed) {
+                ServerGamePacketListenerImpl.LOGGER.warn("{} tried to send a book too large. Book size: {} - Allowed: {} - Pages: {}", this.player.getScoreboardName(), byteTotal, byteAllowed, pageList.size());
+                this.disconnect(Component.literal("Book too large!"));
+                return;
+            }
+        }
+        // Paper end - Book size limits
         // CraftBukkit start
         if (this.lastBookTick + 20 > MinecraftServer.currentTick) {
             this.disconnect(Component.literal("Book edited too quickly!"));