From aab91a25230e8cbd5e591e289ef32fa0f3b67a32 Mon Sep 17 00:00:00 2001
From: BodgeMaster <>
Date: Sun, 11 Sep 2022 09:14:32 +0200
Subject: [PATCH] lib/nbt: Fix NBT::validateRawNBTData() and
 NBT::validateRawListContents closing #52 and #53

---
 src/lib/nbt.cpp | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/src/lib/nbt.cpp b/src/lib/nbt.cpp
index 2bd8840..ba80d7e 100644
--- a/src/lib/nbt.cpp
+++ b/src/lib/nbt.cpp
@@ -595,18 +595,20 @@ namespace NBT {
         }
     }
 
-    bool validateRawList(uint8_t data[], uint64_t dataSize, uint64_t initialPosition, uint64_t* processedDataSize) {
-        ErrorOr<int32_t> elementCount = helper::containedDataLength(data, dataSize, initialPosition);
+    bool validateRawListContents(uint8_t data[], uint64_t dataSize, uint64_t initialPosition, uint64_t* processedDataSize) {
+        // get contained data length by reading it manually because
+        // the function that does it normally can't deal with
+        // headerless tags
+        //
+        // add one byte to position to skip the type byte
+        ErrorOr<int32_t> elementCount = helper::readInt32(data, dataSize, initialPosition+1);
         if (elementCount.isError) {
             return false;
         }
-        // there is no way this is an error bc it gets checked while trying
-        // to get the element count
-        int16_t nameSize = helper::readInt16(data, dataSize, initialPosition+1).value;
-        // type byte + two name size bytes = 3
-        uint8_t contentType = data[initialPosition + nameSize + 3];
-        // type byte + two name size bytes + contained type byte + 4 length bytes = 8
-        *processedDataSize = (uint64_t) nameSize + 8;
+
+        uint8_t contentType = data[initialPosition];
+        // contained type byte + 4 length bytes = 5
+        *processedDataSize = 5;
         switch (contentType) {
             case TagType::END:
                 // everything except content has been touched at this point
@@ -656,7 +658,8 @@ namespace NBT {
                 uint64_t* containedDataSize = new uint64_t;
                 for (int32_t i=0; i<elementCount.value; i++) {
                     *containedDataSize = 0;
-                    if (validateRawList(data, dataSize, initialPosition+*processedDataSize, containedDataSize)) {
+
+                    if (validateRawListContents(data, dataSize, initialPosition+*processedDataSize, containedDataSize)) {
                         *processedDataSize += *containedDataSize;
                     } else {
                         delete containedDataSize;
@@ -670,7 +673,7 @@ namespace NBT {
                 uint64_t* containedDataSize = new uint64_t;
                 for (int32_t i=0; i<elementCount.value; i++) {
                     *containedDataSize = 0;
-                    if (validateRawNBTData(data, dataSize, initialPosition, containedDataSize)) {
+                    if (validateRawNBTData(data, dataSize, initialPosition+*processedDataSize, containedDataSize)) {
                         *processedDataSize += *containedDataSize;
                     } else {
                         delete containedDataSize;
@@ -743,22 +746,24 @@ namespace NBT {
                         return false;
                     }
 
+                    // used seek to the start of the list's/compound’s contents
+                    //
+                    // there is no way this is an error bc it gets
+                    // checked while trying to parse the string above
+                    int16_t nameSize = helper::readInt16(data, dataSize, currentPosition+1).value;
+
                     uint64_t* processedTagSize = new uint64_t;
                     *processedTagSize = 0;
 
                     if (data[currentPosition]==TagType::LIST) {
-                        if (!validateRawList(data, dataSize, currentPosition, processedTagSize)) {
+                        // type byte + two name size bytes = 3
+                        if (!validateRawListContents(data, dataSize, currentPosition + (uint64_t) nameSize + 3, processedTagSize)) {
                             delete processedTagSize;
                             return false;
                         }
+                        *processedTagSize += (uint64_t) nameSize + 3;
                     }
                     if (data[currentPosition]==TagType::COMPOUND) {
-                        // seek to the start of the compound's contents
-                        //
-                        // there is no way this is an error bc it gets
-                        // checked while trying to parse the string above
-                        int16_t nameSize = helper::readInt16(data, dataSize, currentPosition+1).value;
-
                         // type byte + two name size bytes = 3
                         if (!validateRawNBTData(data, dataSize, currentPosition + (uint64_t) nameSize + 3, processedTagSize)) {
                             delete processedTagSize;