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Repair cross-linked chains and bad directory links under Permissive validation - #97
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…alidation Permissive validation already repairs a FAT entry that points past the end of the file by ending the chain there, but several other spec violations that Word and LibreOffice tolerate were still fatal in both modes. Under Permissive validation they are now repaired the same way: - A FAT longer than the file is truncated to the file's sectors. - A FAT or MiniFAT sector pointed to twice ends the later chain there, so only that chain is truncated. - A MiniFAT entry pointing past the end of the MiniFAT ends its chain. - A directory entry's sibling or child that is out of range, or a child on a stream entry, is read as no link. Strict validation still rejects all of these. In a sample of about 2,300 real-world .doc files (Govdocs1 and the LibreOffice bug tracker), these were the reasons 6 genuine Word documents failed to open.
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…hains or bad directory links, through a cfb fork until mdsteele/rust-cfb#97 lands Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Permissive validation already repairs a FAT entry that points past the end of the file by ending the chain there, but several other spec violations that Word and LibreOffice tolerate were still fatal in both modes. Under Permissive validation this repairs them the same way:
END_OF_CHAIN), or a child on a stream entry, is read as no link.Strict validation still rejects all of these, and each repair has a
_permissivetest next to the existing or new_strictone, checking that the repaired result then passes Strict validation.In a sample of about 2,300 real-world
.docfiles (Govdocs1 and attachments from the LibreOffice bug tracker), these were the reasons 6 genuine Word documents failed to open: "mini sector 0 pointed to twice" (4 files), "invalid left sibling: 4294967294" and "non-empty stream child". All six open with this change.