Enforce Gui limit for books

Limits books to 50 pages with 255 characters for each. Anything outside of the limits will be automatically removed
Reference: SpongePowered/Sponge#2156

src/main/java/io/github/lxgaming/sledgehammer/Sledgehammer.java

@@ -71,6 +71,8 @@ private void registerMappings() {
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.block.MixinBlockIce", MixinCategory::isBlockIce);
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.entity.MixinEntity_Teleport", MixinCategory::isItemTeleport);
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.item.MixinItemStack_Exploit", MixinCategory::isItemstackExploit);
+        getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.item.MixinItemWritableBook", MixinCategory::isLimitBooks);
+        getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.network.MixinNetHandlerPlayServer_Book", MixinCategory::isLimitBooks);
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.network.MixinNetHandlerPlayServer_Event", MixinCategory::isInteractEvents);
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.network.MixinNetworkManager", MixinCategory::isFlushNetworkOnTick);
         getMixinMappings().put("io.github.lxgaming.sledgehammer.mixin.core.network.MixinNetworkSystem", MixinCategory::isNetworkSystem);

src/main/java/io/github/lxgaming/sledgehammer/configuration/category/MixinCategory.java

@@ -52,6 +52,9 @@ public class MixinCategory {
     @Setting(value = "itemstack-exploit", comment = "Fixes MC-134716")
     private boolean itemstackExploit = false;
 
+    @Setting(value = "limit-books", comment = "Limits books to 50 pages with 255 characters for each")
+    private boolean limitBooks = false;
+
     @Setting(value = "network-system", comment = "Fixes potential deadlock on shutdown")
     private boolean networkSystem = false;
 
@@ -103,6 +106,10 @@ public boolean isItemstackExploit() {
         return itemstackExploit;
     }
 
+    public boolean isLimitBooks() {
+        return limitBooks;
+    }
+
     public boolean isNetworkSystem() {
         return networkSystem;
     }

src/main/java/io/github/lxgaming/sledgehammer/mixin/core/item/MixinItemWritableBook.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2019 Alex Thomson
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.lxgaming.sledgehammer.mixin.core.item;
+
+import net.minecraft.item.ItemWritableBook;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.nbt.NBTTagList;
+import net.minecraft.nbt.NBTTagString;
+import org.apache.commons.lang3.StringUtils;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+
+@Mixin(value = ItemWritableBook.class, priority = 1337)
+public abstract class MixinItemWritableBook {
+
+    /**
+     * @param compound NBTTagCompound
+     * @author LX_Gaming
+     * @reason Limit books based on {@link net.minecraft.client.gui.GuiScreenBook GuiScreenBook} values.
+     */
+    @Overwrite
+    public static boolean isNBTValid(NBTTagCompound compound) {
+        // TAG_LIST
+        if (compound == null || !compound.hasKey("pages", 9)) {
+            return false;
+        }
+
+        // TAG_STRING
+        NBTTagList pages = compound.getTagList("pages", 8);
+
+        // net.minecraft.item.ItemWrittenBook#resolveContents(ItemStack, EntityPlayer)
+        if (compound.getBoolean("resolved")) {
+            for (int index = 0; index < pages.tagCount(); index++) {
+                if (pages.getStringTagAt(index).length() > 32767) {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        for (int index = 0; index < pages.tagCount(); index++) {
+            if (index >= 50) {
+                pages.removeTag(index);
+                index--;
+                continue;
+            }
+
+            String page = pages.getStringTagAt(index);
+            if (page.length() >= 256) {
+                pages.set(index, new NBTTagString(StringUtils.truncate(page, 252) + "..."));
+            }
+        }
+
+        return true;
+    }
+}

src/main/java/io/github/lxgaming/sledgehammer/mixin/core/network/MixinNetHandlerPlayServer_Book.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2019 Alex Thomson
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.lxgaming.sledgehammer.mixin.core.network;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.network.NetHandlerPlayServer;
+import net.minecraft.network.PacketBuffer;
+import net.minecraft.network.play.client.CPacketCustomPayload;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
+
+@Mixin(value = NetHandlerPlayServer.class, priority = 137)
+public abstract class MixinNetHandlerPlayServer_Book {
+
+    @Inject(method = "processCustomPayload",
+            at = @At(value = "INVOKE",
+                    target = "Lnet/minecraft/item/ItemWritableBook;isNBTValid(Lnet/minecraft/nbt/NBTTagCompound;)Z"
+            ),
+            locals = LocalCapture.CAPTURE_FAILHARD
+    )
+    private void onIsNBTValid(CPacketCustomPayload packet, CallbackInfo callbackInfo,
+                              String channelName, PacketBuffer packetBuffer, ItemStack itemStack) {
+        NBTTagCompound compound = itemStack.getTagCompound();
+        if (compound != null) {
+            // Prevents maliciously crafted packets from bypassing our custom book validation.
+            compound.removeTag("resolved");
+        }
+    }
+
+    @Inject(method = "processCustomPayload",
+            at = @At(value = "INVOKE",
+                    target = "Lnet/minecraft/item/ItemWrittenBook;validBookTagContents(Lnet/minecraft/nbt/NBTTagCompound;)Z"
+            ),
+            locals = LocalCapture.CAPTURE_FAILHARD
+    )
+    private void onValidBookTagContents(CPacketCustomPayload packet, CallbackInfo callbackInfo,
+                                        String channelName, PacketBuffer packetBuffer, ItemStack itemStack) {
+        NBTTagCompound compound = itemStack.getTagCompound();
+        if (compound != null) {
+            // Prevents maliciously crafted packets from bypassing our custom book validation.
+            compound.removeTag("resolved");
+        }
+    }
+}

src/main/resources/mixins.sledgehammer.core.json

@@ -12,6 +12,8 @@
     "block.MixinBlockIce",
     "entity.MixinEntity_Teleport",
     "item.MixinItemStack_Exploit",
+    "item.MixinItemWritableBook",
+    "network.MixinNetHandlerPlayServer_Book",
     "network.MixinNetHandlerPlayServer_Event",
     "network.MixinNetworkManager",
     "network.MixinNetworkSystem",