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Chris LuandGitHub
fbd85d31b0
A decode ends by deleting the shards it read, and the only thing standing between that and a bad reconstruction is verifyDecodedVolumeBeforeDelete, which asks whether .dat and .idx are non-empty. A .dat truncated to a single byte passes, and the shards -- the only other copy of everything past the cut -- are deleted on the strength of it. The server already knows the answer it never checks: FindDatFileSize returns the extent the EC index references, and WriteDatFile rebuilds to it. Compare the two once the file is written and fail the decode instead of reporting a short volume as a good one. Longer than the extent still verifies -- padding is not missing data -- so only a genuinely short rebuild is rejected. Needle counts cannot answer this: .idx is written from .ecx, so the count matches by construction and a truncated .dat still reports every needle.