metaUtils: require Z_STREAM_END when validating uncompressed data#145
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dzenanz merged 1 commit intoJul 23, 2026
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MET_PerformUncompression validated the number of bytes produced but not that the zlib stream terminated with Z_STREAM_END. When the output fills the destination buffer exactly, the next inflate() returns Z_BUF_ERROR (deliberately excluded from the diagnostic), the loop exits, and the byte-count check passes -- so a stream truncated at the size boundary is accepted without validating its trailing Adler-32 checksum. Reject the data unless inflate reported Z_STREAM_END, in addition to the existing byte-count check. This closes the exact-size truncation gap left by the byte-count check added in Kitware#142. Fixes Kitware#144.
hjmjohnson
marked this pull request as ready for review
July 23, 2026 22:17
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@dzenanz I don't have merge capabilities here. This was a possible failure case found by GrepTile. |
dzenanz
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Jul 23, 2026
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Require
Z_STREAM_ENDinMET_PerformUncompression, not just the expected byte count, so a compressed stream truncated exactly at the declared output size is rejected instead of silently accepted. Fixes #144; hardens the byte-count check from #142.Root cause
When the decompressed data fills the destination buffer exactly, the last
inflate()returnsZ_OKand the next call (withavail_out == 0) returnsZ_BUF_ERROR. That is< 0, so the loop exits — butZ_BUF_ERRORis deliberately excluded from the "Uncompress failed" diagnostic (treated as non-fatal "buffer full"). Control reaches the final check withdest_pos == uncompressedDataSizeand the function returnstrue, even thoughZ_STREAM_ENDwas never reached and the trailing Adler-32 checksum was never validated.Adding an explicit
err != Z_STREAM_ENDrejection guarantees the entire stream (including its trailer) was consumed, closing the exact-size-truncation gap while keeping the informative byte-count message for the short-read case.