From 35f7a90d0130fbcf67e3cc11c49c42aaad1f9603 Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Fri, 24 Nov 2017 10:54:06 +0000
Subject: [PATCH] Better PNG chunk length error message

Via drewnoakes/metadata-extractor#272
---
 MetadataExtractor/Formats/Png/PngChunkReader.cs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/MetadataExtractor/Formats/Png/PngChunkReader.cs b/MetadataExtractor/Formats/Png/PngChunkReader.cs
index c682ba6da..328d46465 100644
--- a/MetadataExtractor/Formats/Png/PngChunkReader.cs
+++ b/MetadataExtractor/Formats/Png/PngChunkReader.cs
@@ -88,6 +88,8 @@ public IEnumerable<PngChunk> Extract([NotNull] SequentialReader reader, [CanBeNu
             {
                 // Process the next chunk.
                 var chunkDataLength = reader.GetInt32();
+                if (chunkDataLength < 0)
+                    throw new PngProcessingException("PNG chunk length exceeds maximum");
                 var chunkType = new PngChunkType(reader.GetBytes(4));
                 var willStoreChunk = desiredChunkTypes == null || desiredChunkTypes.Contains(chunkType);
                 var chunkData = reader.GetBytes(chunkDataLength);