From 3a8e5a216fdf1f698e568cb159d1b74f36d04e73 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Mon, 10 Jan 2022 11:12:48 +1100
Subject: [PATCH] Only decode App0 1x. Fix #1932

---
 .../Formats/Jpeg/Components/Decoder/JFifMarker.cs      | 10 +++-------
 src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs         |  4 +++-
 .../Formats/Jpg/JpegDecoderTests.Metadata.cs           |  9 +++++----
 tests/ImageSharp.Tests/TestImages.cs                   |  1 +
 .../Input/Jpg/issues/issue-1932-app0-resolution.jpg    |  3 +++
 5 files changed, 15 insertions(+), 12 deletions(-)
 create mode 100644 tests/Images/Input/Jpg/issues/issue-1932-app0-resolution.jpg

diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs
index c7b71f75a8..a95e6c16c2 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
@@ -103,26 +103,22 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         /// <inheritdoc/>
         public bool Equals(JFifMarker other)
-        {
-            return this.MajorVersion == other.MajorVersion
+            => this.MajorVersion == other.MajorVersion
                 && this.MinorVersion == other.MinorVersion
                 && this.DensityUnits == other.DensityUnits
                 && this.XDensity == other.XDensity
                 && this.YDensity == other.YDensity;
-        }
 
         /// <inheritdoc/>
         public override bool Equals(object obj) => obj is JFifMarker other && this.Equals(other);
 
         /// <inheritdoc/>
         public override int GetHashCode()
-        {
-            return HashCode.Combine(
+            => HashCode.Combine(
                 this.MajorVersion,
                 this.MinorVersion,
                 this.DensityUnits,
                 this.XDensity,
                 this.YDensity);
-        }
     }
 }
diff --git a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
index a21f1a71d7..5f01c04688 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
@@ -625,7 +625,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         private void ProcessApplicationHeaderMarker(BufferedReadStream stream, int remaining)
         {
             // We can only decode JFif identifiers.
-            if (remaining < JFifMarker.Length)
+            // Some bad images contain multiple App0 markers (Issue 1932) so we check to see
+            // if it's already been read.
+            if (remaining < JFifMarker.Length || (!this.jFif.Equals(default)))
             {
                 // Skip the application header length
                 stream.Skip(remaining);
diff --git a/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs b/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs
index 7b3e20aa2a..0ef5090cc8 100644
--- a/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs
+++ b/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs
@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
         // TODO: A JPEGsnoop & metadata expert should review if the Exif/Icc expectations are correct.
         // I'm seeing several entries with Exif-related names in images where we do not decode an exif profile. (- Anton)
         public static readonly TheoryData<bool, string, int, bool, bool> MetadataTestData =
-        new TheoryData<bool, string, int, bool, bool>
+        new()
         {
             { false, TestImages.Jpeg.Progressive.Progress, 24, false, false },
             { false, TestImages.Jpeg.Progressive.Fb, 24, false, true },
@@ -42,15 +42,16 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
         };
 
         public static readonly TheoryData<string, int, int, PixelResolutionUnit> RatioFiles =
-        new TheoryData<string, int, int, PixelResolutionUnit>
+        new()
         {
             { TestImages.Jpeg.Baseline.Ratio1x1, 1, 1, PixelResolutionUnit.AspectRatio },
             { TestImages.Jpeg.Baseline.Snake, 300, 300, PixelResolutionUnit.PixelsPerInch },
-            { TestImages.Jpeg.Baseline.GammaDalaiLamaGray, 72, 72, PixelResolutionUnit.PixelsPerInch }
+            { TestImages.Jpeg.Baseline.GammaDalaiLamaGray, 72, 72, PixelResolutionUnit.PixelsPerInch },
+            { TestImages.Jpeg.Issues.MultipleApp01932, 400, 400, PixelResolutionUnit.PixelsPerInch }
         };
 
         public static readonly TheoryData<string, int> QualityFiles =
-        new TheoryData<string, int>
+        new()
         {
             { TestImages.Jpeg.Baseline.Calliphora, 80 },
             { TestImages.Jpeg.Progressive.Fb, 75 },
diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs
index deed0b2404..3c3c12c91d 100644
--- a/tests/ImageSharp.Tests/TestImages.cs
+++ b/tests/ImageSharp.Tests/TestImages.cs
@@ -257,6 +257,7 @@ namespace SixLabors.ImageSharp.Tests
                 public const string IdentifyMultiFrame1211 = "Jpg/issues/issue-1221-identify-multi-frame.jpg";
                 public const string WrongColorSpace = "Jpg/issues/Issue1732-WrongColorSpace.jpg";
                 public const string MalformedUnsupportedComponentCount = "Jpg/issues/issue-1900-malformed-unsupported-255-components.jpg";
+                public const string MultipleApp01932 = "Jpg/issues/issue-1932-app0-resolution.jpg";
 
                 public static class Fuzz
                 {
diff --git a/tests/Images/Input/Jpg/issues/issue-1932-app0-resolution.jpg b/tests/Images/Input/Jpg/issues/issue-1932-app0-resolution.jpg
new file mode 100644
index 0000000000..42a90c68c2
--- /dev/null
+++ b/tests/Images/Input/Jpg/issues/issue-1932-app0-resolution.jpg
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b9d1a583e5c8c0a1a7362d06befd82883e1dc4231129ddb11d11d8c428691ff5
+size 1126332