Fix #2953

Author: JimBobSquarePants

.gitattributes

@@ -115,7 +115,6 @@
 *.jpg               filter=lfs diff=lfs merge=lfs -text
 *.jpeg              filter=lfs diff=lfs merge=lfs -text
 *.bmp               filter=lfs diff=lfs merge=lfs -text
-*.BMP               filter=lfs diff=lfs merge=lfs -text
 *.gif               filter=lfs diff=lfs merge=lfs -text
 *.png               filter=lfs diff=lfs merge=lfs -text
 *.tif               filter=lfs diff=lfs merge=lfs -text

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -402,6 +402,11 @@ private void ReadComments(BufferedReadStream stream)
                     GifThrowHelper.ThrowInvalidImageContentException($"Gif comment length '{length}' exceeds max '{GifConstants.MaxCommentSubBlockLength}' of a comment data block");
                 }
 
+                if (length == -1)
+                {
+                    GifThrowHelper.ThrowInvalidImageContentException("Unexpected end of stream while reading gif comment");
+                }
+
                 if (this.skipMetadata)
                 {
                     stream.Seek(length, SeekOrigin.Current);

tests/ImageSharp.Tests/Formats/Gif/GifDecoderTests.cs

@@ -183,16 +183,16 @@ public void Issue1530_BadDescriptorDimensions<TPixel>(TestImageProvider<TPixel>
             image.CompareToReferenceOutputMultiFrame(provider, ImageComparer.Exact);
         }
 
-    // https://github.com/SixLabors/ImageSharp/issues/2758
-    [Theory]
-    [WithFile(TestImages.Gif.Issues.Issue2758, PixelTypes.Rgba32)]
-    public void Issue2758_BadDescriptorDimensions<TPixel>(TestImageProvider<TPixel> provider)
-        where TPixel : unmanaged, IPixel<TPixel>
-    {
-        using Image<TPixel> image = provider.GetImage();
-        image.DebugSaveMultiFrame(provider);
-        image.CompareToReferenceOutputMultiFrame(provider, ImageComparer.Exact);
-    }
+        // https://github.com/SixLabors/ImageSharp/issues/2758
+        [Theory]
+        [WithFile(TestImages.Gif.Issues.Issue2758, PixelTypes.Rgba32)]
+        public void Issue2758_BadDescriptorDimensions<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using Image<TPixel> image = provider.GetImage();
+            image.DebugSaveMultiFrame(provider);
+            image.CompareToReferenceOutputMultiFrame(provider, ImageComparer.Exact);
+        }
 
         // https://github.com/SixLabors/ImageSharp/issues/405
         [Theory]
@@ -329,5 +329,18 @@ public void Issue2859_LZWPixelStackOverflow<TPixel>(TestImageProvider<TPixel> pr
             image.DebugSaveMultiFrame(provider);
             image.CompareToReferenceOutputMultiFrame(provider, ImageComparer.Exact);
         }
+
+        // https://github.com/SixLabors/ImageSharp/issues/2953
+        [Theory]
+        [WithFile(TestImages.Gif.Issues.Issue2953, PixelTypes.Rgba32)]
+        public void Issue2953<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            // We should throw a InvalidImageContentException when trying to identify or load an invalid GIF file.
+            var testFile = TestFile.Create(provider.SourceFileOrDescription);
+
+            Assert.Throws<InvalidImageContentException>(() => Image.Identify(testFile.FullPath));
+            Assert.Throws<InvalidImageContentException>(() => Image.Load(testFile.FullPath));
+        }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -468,6 +468,7 @@ public static class Issues
                 public const string Issue2758 = "Gif/issues/issue_2758.gif";
                 public const string Issue2859_A = "Gif/issues/issue_2859_A.gif";
                 public const string Issue2859_B = "Gif/issues/issue_2859_B.gif";
+                public const string Issue2953 = "Gif/issues/issue_2953.gif";
             }
 
             public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin, Leo, Ratio4x1, Ratio1x4 };