mirror of https://github.com/SixLabors/ImageSharp
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Use ulong arithmetic in CalculateBytesPerRow and block size calculations to prevent integer overflow. Add validation for DataWindow dimensions, block size limits, and row offsets outside stream bounds. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>pull/3126/head
Sven Claesson
2 months ago
4 changed files with 269 additions and 16 deletions
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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using System.Buffers.Binary; |
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using SixLabors.ImageSharp.Formats; |
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using SixLabors.ImageSharp.Formats.Exr; |
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using SixLabors.ImageSharp.PixelFormats; |
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namespace SixLabors.ImageSharp.Tests.Formats.Exr; |
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/// <summary>
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/// Security regression tests for the EXR decoder (Findings EXR-1, EXR-2, EXR-3).
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/// The EXR decoder was merged to main but not yet included in a tagged NuGet release.
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/// Each test demonstrates a crafted-input crash present in the unfixed code.
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/// </summary>
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public class ExrDecoderSecurityTests |
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{ |
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/// <summary>
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/// EXR-1 — EXR DataWindow Integer Overflow Produces Negative Image Dimensions (DoS)
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///
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/// Width and Height are computed from attacker-controlled DataWindow attributes
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/// using unchecked int subtraction:
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/// this.Width = XMax - XMin + 1 // overflows to -2147483647
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///
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/// The negative Width is then passed to the Image<TPixel> constructor, which calls
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/// Guard.MustBeGreaterThan(width, 0) → ArgumentOutOfRangeException.
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///
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/// After a fix this should throw InvalidImageContentException instead.
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///
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/// Affected file:
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/// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 600–601
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/// </summary>
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[Fact] |
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public void Decode_DataWindowOverflow_NegativeWidth_Throws() |
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{ |
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// XMin = -1073741825, XMax = 1073741823
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// Width = 1073741823 - (-1073741825) + 1 = 2^31 + 1 → wraps to -2147483647
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byte[] data = BuildMinimalExr(xMin: -1073741825, yMin: 0, xMax: 1073741823, yMax: 0); |
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using var stream = new MemoryStream(data); |
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Assert.Throws<InvalidImageContentException>( |
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() => ExrDecoder.Instance.Decode<Rgba32>(DecoderOptions.Default, stream)); |
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} |
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/// <summary>
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/// EXR-2 — EXR Row Offset Table Unvalidated Seek (DoS / data integrity)
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///
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/// Row offsets are read from the file and used unconditionally to seek the stream:
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/// ulong rowOffset = this.ReadUnsignedLong(stream);
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/// stream.Position = (long)rowOffset; // no bounds check
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///
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/// A crafted offset of 0xFFFFFFFFFFFFFFFF casts to −1 as long, causing
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/// an ArgumentOutOfRangeException when setting stream.Position.
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///
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/// After a fix this should throw InvalidImageContentException instead.
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///
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/// Affected file:
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/// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 170–175 (scanline)
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/// lines 243–248 (tile)
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/// </summary>
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[Fact] |
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public void Decode_CraftedRowOffsets_OutOfBounds_Throws() |
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{ |
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// Valid 2×2 image (XMin=0,YMin=0,XMax=1,YMax=1 → Width=2,Height=2).
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// Row offset table immediately follows the header null byte:
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// 2 rows × 8 bytes each, all set to 0xFFFFFFFFFFFFFFFF.
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byte[] invalidOffsets = new byte[16]; |
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BinaryPrimitives.WriteUInt64LittleEndian(invalidOffsets, 0xFFFFFFFFFFFFFFFF); |
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BinaryPrimitives.WriteUInt64LittleEndian(invalidOffsets.AsSpan(8), 0xFFFFFFFFFFFFFFFF); |
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byte[] data = BuildMinimalExr( |
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xMin: 0, yMin: 0, xMax: 1, yMax: 1, |
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rowOffsetTableAppend: invalidOffsets); |
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using var stream = new MemoryStream(data); |
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Assert.Throws<InvalidImageContentException>( |
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() => ExrDecoder.Instance.Decode<Rgba32>(DecoderOptions.Default, stream)); |
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} |
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/// <summary>
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/// EXR-3 — EXR bytesPerBlock uint Overflow Chain (DoS)
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///
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/// CalculateBytesPerRow is computed in ulong (fixed), and if the result exceeds
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/// int.MaxValue the decoder throws InvalidImageContentException. With 4 RGBA HALF
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/// channels and Width = 2^29:
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/// bytesPerRow = 4 × 2 × 2^29 = 2^32 (> int.MaxValue)
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/// → InvalidImageContentException before any allocation
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///
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/// Affected file:
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/// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 142–150, 215–223
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/// src/ImageSharp/Formats/Exr/ExrUtils.cs CalculateBytesPerRow
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/// </summary>
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[Fact] |
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public void Decode_BytesPerBlockUintOverflow_Throws() |
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{ |
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// 4 RGBA HALF channels, Width = 2^29:
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// bytesPerRow = 4 × 2 × 536870912 = 4294967296 > int.MaxValue
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// → InvalidImageContentException from the block-size guard
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byte[] data = BuildMinimalRgbaExr(xMin: 0, yMin: 0, xMax: 536870911, yMax: 0); |
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using var stream = new MemoryStream(data); |
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Assert.Throws<InvalidImageContentException>( |
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() => ExrDecoder.Instance.Decode<Rgba32>(DecoderOptions.Default, stream)); |
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} |
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// -------------------------------------------------------------------------
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// Helpers: construct minimal valid-enough EXR scanline files.
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//
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// Required attributes per ParseHeaderAttributes validation:
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// channels, compression, dataWindow, displayWindow,
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// lineOrder, pixelAspectRatio, screenWindowCenter, screenWindowWidth
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// -------------------------------------------------------------------------
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private static byte[] BuildMinimalExr( |
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int xMin, int yMin, int xMax, int yMax, |
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byte[]? rowOffsetTableAppend = null) |
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{ |
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// channels: single "R" HALF channel with xSampling=1, ySampling=1
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// Layout per ReadChannelInfo: name\0 (2) + pixelType (4) + pLinear+reserved (4)
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// + xSampling (4) + ySampling (4) = 18 bytes/channel
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// + list-null (1) = 19 total
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byte[] channelData = |
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[ |
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0x52, 0x00, // "R\0"
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0x01, 0x00, 0x00, 0x00, // pixelType = Half (1)
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0x00, 0x00, 0x00, 0x00, // pLinear + 3 reserved bytes
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0x01, 0x00, 0x00, 0x00, // xSampling = 1
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0x01, 0x00, 0x00, 0x00, // ySampling = 1
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0x00, // channel-list null terminator
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]; |
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return BuildExrWithChannels(xMin, yMin, xMax, yMax, channelData, rowOffsetTableAppend); |
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} |
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private static byte[] BuildMinimalRgbaExr(int xMin, int yMin, int xMax, int yMax) |
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{ |
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// 4 HALF channels in alphabetical order (A, B, G, R) per EXR spec.
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// 18 bytes per channel × 4 channels + 1 list-null = 73 bytes total.
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byte[] channelData = |
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[ |
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0x41, 0x00, // "A\0"
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0x01, 0x00, 0x00, 0x00, // pixelType = Half (1)
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0x00, 0x00, 0x00, 0x00, // pLinear + 3 reserved bytes
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0x01, 0x00, 0x00, 0x00, // xSampling = 1
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0x01, 0x00, 0x00, 0x00, // ySampling = 1
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0x42, 0x00, // "B\0"
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0x01, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x47, 0x00, // "G\0"
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0x01, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x52, 0x00, // "R\0"
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0x01, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x01, 0x00, 0x00, 0x00, |
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0x00, // channel-list null terminator
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]; |
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return BuildExrWithChannels(xMin, yMin, xMax, yMax, channelData); |
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} |
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private static byte[] BuildExrWithChannels( |
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int xMin, int yMin, int xMax, int yMax, |
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byte[] channelData, |
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byte[]? rowOffsetTableAppend = null) |
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{ |
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using var ms = new MemoryStream(); |
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using var bw = new BinaryWriter(ms, System.Text.Encoding.ASCII, leaveOpen: true); |
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// Magic (0x01312F76 LE) + version 2, scanline (flags = 0x00)
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bw.Write(new byte[] { 0x76, 0x2F, 0x31, 0x01, 0x02, 0x00, 0x00, 0x00 }); |
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void WriteAttr(string name, string type, byte[] payload) |
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{ |
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foreach (char c in name) bw.Write((byte)c); |
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bw.Write((byte)0); |
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foreach (char c in type) bw.Write((byte)c); |
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bw.Write((byte)0); |
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bw.Write(payload.Length); |
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bw.Write(payload); |
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} |
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WriteAttr("channels", "chlist", channelData); |
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WriteAttr("compression", "compression", [0x00]); // None
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byte[] dw = new byte[16]; |
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BinaryPrimitives.WriteInt32LittleEndian(dw, xMin); |
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BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(4), yMin); |
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BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(8), xMax); |
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BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(12), yMax); |
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WriteAttr("dataWindow", "box2i", dw); |
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WriteAttr("displayWindow", "box2i", new byte[16]); // all zeros (0,0,0,0)
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WriteAttr("lineOrder", "lineOrder", [0x00]); // IncreasingY
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byte[] aspect = new byte[4]; |
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BinaryPrimitives.WriteSingleLittleEndian(aspect, 1.0f); |
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WriteAttr("pixelAspectRatio", "float", aspect); |
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WriteAttr("screenWindowCenter", "v2f", new byte[8]); // (0f, 0f)
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byte[] sww = new byte[4]; |
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BinaryPrimitives.WriteSingleLittleEndian(sww, 1.0f); |
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WriteAttr("screenWindowWidth", "float", sww); |
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bw.Write((byte)0x00); // end-of-header sentinel
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if (rowOffsetTableAppend is not null) |
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bw.Write(rowOffsetTableAppend); |
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return ms.ToArray(); |
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} |
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} |
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