Jpeg sampling factor validation #1894

src/ImageSharp/Common/Helpers/Numerics.cs

@@ -963,5 +963,14 @@ public static uint RotateRight(uint value, int offset)
         public static uint RotateRightSoftwareFallback(uint value, int offset)
             => (value >> offset) | (value << (32 - offset));
 #endif
+
+        /// <summary>
+        /// Tells whether input value is outside of the given range.
+        /// </summary>
+        /// <param name="value">Value.</param>
+        /// <param name="min">Mininum value, inclusive.</param>
+        /// <param name="max">Maximum value, inclusive.</param>
+        public static bool IsOutOfRange(int value, int min, int max)
+            => (uint)(value - min) > (uint)(max - min);
     }
 }

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -1031,13 +1031,13 @@ private void ProcessStartOfFrameMarker(BufferedReadStream stream, int remaining,
                 int v = hv & 15;
 
                 // Validate: 1-4 range
-                if (h is < 1 or > 4)
+                if (Numerics.IsOutOfRange(h, 1, 4))
                 {
                     JpegThrowHelper.ThrowBadSampling(h);
                 }
 
                 // Validate: 1-4 range
-                if (v is < 1 or > 4)
+                if (Numerics.IsOutOfRange(v, 1, 4))
                 {
                     JpegThrowHelper.ThrowBadSampling(v);
                 }

tests/ImageSharp.Tests/Common/NumericsTests.cs

@@ -97,5 +97,25 @@ public void DivideCeil_RandomValues(int seed, int count)
                 Assert.True(expected == actual, $"Expected: {expected}\nActual: {actual}\n{value} / {divisor} = {expected}");
             }
         }
+
+        private static bool IsOutOfRange_ReferenceImplementation(int value, int min, int max) => value < min || value > max;
+
+        [Theory]
+        [InlineData(1, 100)]
+        public void IsOutOfRange(int seed, int count)
+        {
+            var rng = new Random(seed);
+            for (int i = 0; i < count; i++)
+            {
+                int value = rng.Next();
+                int min = rng.Next();
+                int max = rng.Next(min, int.MaxValue);
+
+                bool expected = IsOutOfRange_ReferenceImplementation(value, min, max);
+                bool actual = Numerics.IsOutOfRange(value, min, max);
+
+                Assert.True(expected == actual, $"IsOutOfRange({value}, {min}, {max})");
+            }
+        }
     }
 }