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Validate LZ41 footer fields before decompression #399

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Merged
Shivansps merged 1 commit into from
May 9, 2026
Merged

Validate LZ41 footer fields before decompression #399

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13 changes: 12 additions & 1 deletion IonKiwi.lz4/LZ4RawUtility.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -293,15 +293,23 @@ public static unsafe int LZ41_Stream_Decompress(Stream inputStream, Stream outpu
/* Num Offsets */
inputStream.Position = initialPosition + compressedFileSize.Value - 12;
int numOffsets = br.ReadInt32();
if (numOffsets <= 0 || numOffsets > (compressedFileSize.Value - 12) / 4)
throw new Exception($"Invalid numOffsets in LZ41 footer: {numOffsets}");

/* File Size */
if(!length.HasValue)
if(!length.HasValue)
{
length = br.ReadInt32();
if (length <= 0)
throw new Exception($"Invalid uncompressed size in LZ41 footer: {length}");
}
else
inputStream.Position += 4;

/* Block Size */
int blockSize = br.ReadInt32();
if (blockSize <= 0)
throw new Exception($"Invalid block size in LZ41 footer: {blockSize}");

/* Read the offsets tail */
inputStream.Position = initialPosition + (compressedFileSize.Value - 12 - (numOffsets * 4));
Expand All @@ -315,6 +323,9 @@ public static unsafe int LZ41_Stream_Decompress(Stream inputStream, Stream outpu
int currentBlock = offset.Value / blockSize;
int endBlock = ((offset.Value + length.Value - 1) / blockSize) + 1;

if (currentBlock < 0 || endBlock >= numOffsets)
throw new Exception($"Requested range exceeds block table (blocks {currentBlock}–{endBlock}, numOffsets={numOffsets})");

/* Seek to the first block to read */
inputStream.Position = initialPosition + offsets[currentBlock];

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