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Fuzzing and bugfixes for magicless-format decoding (#3976)

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* fuzzing and bugfixes for magicless format

* reset dctx before each decompression

* do not memcmp empty buffers

* nit: decompressor errata
This commit is contained in:
Elliot Gorokhovsky
2024-03-20 19:22:34 -04:00
committed by GitHub
parent 6a0052a409
commit 741b87bbe1
6 changed files with 163 additions and 4 deletions
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doc/decompressor_errata.md
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@ -125,3 +125,24 @@ The total `Block_Content` is `5` bytes, and `Last_Table_Offset` is `2`.
See the compressor workaround code:
https://github.com/facebook/zstd/blob/8814aa5bfa74f05a86e55e9d508da177a893ceeb/lib/compress/zstd_compress.c#L2667-L2682
Magicless format
----------------------
**Last affected version**: v1.5.5
**Affected decompressor component(s)**: Library
**Produced by the reference compressor**: Yes (example: https://gist.github.com/embg/9940726094f4cf2cef162cffe9319232)
**Example Frame**: `27 b5 2f fd 00 03 19 00 00 66 6f 6f 3f ba c4 59`
v1.5.6 fixes several bugs in which the magicless-format decoder rejects valid frames.
These include but are not limited to:
* Valid frames that happen to begin with a legacy magic number (little-endian)
* Valid frames that happen to begin with a skippable magic number (little-endian)
If you are affected by this issue and cannot update to v1.5.6 or later, there is a
workaround to recover affected data. Simply prepend the ZSTD magic number
`0xFD2FB528` (little-endian) to your data and decompress using the standard-format
decoder.