Sampling factor validation

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegComponent.cs

@@ -19,21 +19,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
             this.Frame = frame;
             this.Id = id;
 
-            // Validate sampling factors.
-            if (horizontalFactor == 0 || verticalFactor == 0)
-            {
-                JpegThrowHelper.ThrowBadSampling();
-            }
-
             this.HorizontalSamplingFactor = horizontalFactor;
             this.VerticalSamplingFactor = verticalFactor;
             this.SamplingFactors = new Size(this.HorizontalSamplingFactor, this.VerticalSamplingFactor);
 
-            if (quantizationTableIndex > 3)
-            {
-                JpegThrowHelper.ThrowBadQuantizationTableIndex(quantizationTableIndex);
-            }
-
             this.QuantizationTableIndex = quantizationTableIndex;
             this.Index = index;
         }

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -1022,10 +1022,26 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             int index = 0;
             for (int i = 0; i < componentCount; i++)
             {
+                // 1 byte: component identifier
+                byte componentId = this.temp[index];
+
+                // 1 byte: component sampling factors
                 byte hv = this.temp[index + 1];
                 int h = (hv >> 4) & 15;
                 int v = hv & 15;
 
+                // Validate: 1-4 range
+                if (h is < 1 or > 4)
+                {
+                    JpegThrowHelper.ThrowInvalidImageContentException($"Bad horizontal sampling factor: {h}");
+                }
+
+                // Validate: 1-4 range
+                if (v is < 1 or > 4)
+                {
+                    JpegThrowHelper.ThrowInvalidImageContentException($"Bad vertical sampling factor: {v}");
+                }
+
                 if (maxH < h)
                 {
                     maxH = h;
@@ -1036,10 +1052,19 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                     maxV = v;
                 }
 
-                var component = new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, this.temp[index], h, v, this.temp[index + 2], i);
+                // 1 byte: quantization table destination selector
+                byte quantTableIndex = this.temp[index + 2];
+
+                // Validate: 0-3 range
+                if (quantTableIndex > 3)
+                {
+                    JpegThrowHelper.ThrowBadQuantizationTableIndex(quantTableIndex);
+                }
+
+                var component = new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, componentId, h, v, quantTableIndex, i);
 
                 this.Frame.Components[i] = component;
-                this.Frame.ComponentIds[i] = component.Id;
+                this.Frame.ComponentIds[i] = componentId;
 
                 index += componentBytes;
             }

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Images.cs

@@ -40,9 +40,6 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 // LibJpeg can open this despite incorrect colorspace metadata.
                 TestImages.Jpeg.Issues.IncorrectColorspace855,
 
-                // LibJpeg can open this despite the invalid subsampling units.
-                TestImages.Jpeg.Issues.Fuzz.IndexOutOfRangeException824C,
-
                 // High depth images
                 TestImages.Jpeg.Baseline.Testorig12bit,
             };
@@ -90,7 +87,8 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             TestImages.Jpeg.Issues.Fuzz.AccessViolationException827,
             TestImages.Jpeg.Issues.Fuzz.ExecutionEngineException839,
             TestImages.Jpeg.Issues.Fuzz.IndexOutOfRangeException1693A,
-            TestImages.Jpeg.Issues.Fuzz.IndexOutOfRangeException1693B
+            TestImages.Jpeg.Issues.Fuzz.IndexOutOfRangeException1693B,
+            TestImages.Jpeg.Issues.Fuzz.IndexOutOfRangeException824C,
         };
 
         private static readonly Dictionary<string, float> CustomToleranceValues =