Check chunk data index and no longer panic

level/chunk.go

@@ -143,6 +143,9 @@ func ChunkFromSave(c *save.Chunk) (*Chunk, error) {
 	sections := make([]Section, secs)
 	for _, v := range c.Sections {
 		i := int32(v.Y) - c.YPos
+		if i < 0 || i >= int32(secs) {
+			return nil, fmt.Errorf("section Y value %d out of bounds", v.Y)
+		}
 		var err error
 		sections[i].BlockCount, sections[i].States, err = readStatesPalette(v.BlockStates.Palette, v.BlockStates.Data)
 		if err != nil {

save/chunk.go

@@ -16,7 +16,7 @@ type Chunk struct {
 	XPos          int32            `nbt:"xPos"`
 	YPos          int32            `nbt:"yPos"`
 	ZPos          int32            `nbt:"zPos"`
-	BlockEntities nbt.RawMessage `nbt:"block_entities"`
+	BlockEntities []nbt.RawMessage `nbt:"block_entities"`
 	Structures    nbt.RawMessage   `nbt:"structures"`
 	Heightmaps    struct {
 		MotionBlocking         []uint64 `nbt:"MOTION_BLOCKING"`