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Png- Do not attempt to read data for chunks of length 0. #2561

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Merged
JimBobSquarePants merged 4 commits into from
Nov 29, 2023
Merged

Png- Do not attempt to read data for chunks of length 0. #2561

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df2f698
Do not attempt to read data for chunks of length 0.
JimBobSquarePants Oct 17, 2023
147ca01
Merge branch 'main' into js/faster-png-eof-handling
JimBobSquarePants Oct 31, 2023
74af9f0
Merge branch 'main' into js/faster-png-eof-handling
JimBobSquarePants Nov 7, 2023
2927fcc
Merge branch 'main' into js/faster-png-eof-handling
JimBobSquarePants Nov 29, 2023
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6 changes: 6 additions & 0 deletions src/ImageSharp/Formats/Png/PngDecoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
using SixLabors.ImageSharp.Formats.Png.Filters;
using SixLabors.ImageSharp.IO;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.Memory.Internals;
using SixLabors.ImageSharp.Metadata;
using SixLabors.ImageSharp.Metadata.Profiles.Exif;
using SixLabors.ImageSharp.Metadata.Profiles.Icc;
Expand Down Expand Up @@ -1569,6 +1570,11 @@ private void SkipChunkDataAndCrc(in PngChunk chunk)
[MethodImpl(InliningOptions.ShortMethod)]
private IMemoryOwner<byte> ReadChunkData(int length)
{
if (length == 0)
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@JimBobSquarePants JimBobSquarePants Oct 17, 2023

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We avoid the read here because Png still has to do a CRC check which if does not occur leads to failure during reading of chained Png images within a single stream.

{
return new BasicArrayBuffer<byte>(Array.Empty<byte>());
}

// We rent the buffer here to return it afterwards in Decode()
IMemoryOwner<byte> buffer = this.configuration.MemoryAllocator.Allocate<byte>(length, AllocationOptions.Clean);

Expand Down
10 changes: 9 additions & 1 deletion tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs
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Expand Up @@ -7,7 +7,6 @@
using SixLabors.ImageSharp.Formats.Png;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing.Processors.Quantization;
using SixLabors.ImageSharp.Tests.TestUtilities;
using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
Expand Down Expand Up @@ -612,4 +611,13 @@ static void RunTest(string providerDump, string nonContiguousBuffersStr)
"Disco")
.Dispose();
}

[Fact]
public void Binary_PrematureEof()
{
using EofHitCounter eofHitCounter = EofHitCounter.RunDecoder(TestImages.Png.Bad.FlagOfGermany0000016446);

Assert.True(eofHitCounter.EofHitCount <= 2);
Assert.Equal(new Size(200, 120), eofHitCounter.Image.Size);
}
}
2 changes: 2 additions & 0 deletions tests/ImageSharp.Tests/TestImages.cs
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Expand Up @@ -169,6 +169,8 @@ public static class Bad
// Invalid color type.
public const string ColorTypeOne = "Png/xc1n0g08.png";
public const string ColorTypeNine = "Png/xc9n2c08.png";

public const string FlagOfGermany0000016446 = "Png/issues/flag_of_germany-0000016446.png";
}
}

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3 changes: 3 additions & 0 deletions tests/Images/Input/Png/issues/flag_of_germany-0000016446.png
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