parse: Add set_verify_checksums API; improve fuzz coverage#11
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parse: Add set_verify_checksums API; improve fuzz coverage#11
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The parse.rs and differential.rs fuzz targets were getting almost zero coverage of deeper parser logic (PAX extensions, GNU long name/link, sparse files, etc.) because random fuzz input almost never has valid tar header checksums. The parser's verify_checksum() call at the top of parse_header() rejects ~100% of random inputs immediately. For the parse.rs fuzzer, add a Parser::set_verify_checksums(bool) API that allows skipping checksum verification entirely. The fuzzer uses this ~90% of the time (determined by the first byte of input), letting the fuzzer exercise all the parsing code paths beyond the checksum gate. For the differential fuzzer, since both tar-core and tar-rs must see identical data with valid checksums, use a fixup_checksums() approach that rewrites checksum fields in-place before passing to both parsers. Assisted-by: OpenCode (Claude claude-opus-4-6)
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Summary
The
parse.rsanddifferential.rsfuzz targets were getting almost zero coverage of deeper parser logic (PAX extensions, GNU long name/link, sparse files, etc.) because random fuzz input almost never has valid tar header checksums. The parser'sverify_checksum()call at the top ofparse_header()rejects ~100% of random inputs immediately.Changes
Library (
src/parse.rs): AddParser::set_verify_checksums(bool)API that controls whether header checksums are verified during parsing. Default istrue(safe by default). This follows the same pattern as the existingset_allow_empty_path(bool)API.parse.rsfuzzer: Use the new API to skip checksum verification ~90% of the time (determined by the first byte of input), letting the fuzzer exercise all parsing code paths beyond the checksum gate. The remaining 10% still tests checksum validation itself.differential.rsfuzzer: Since both tar-core and tar-rs must see identical data with valid checksums, use afixup_checksums()approach that rewrites checksum fields in-place before passing to both parsers. Also minor cleanup: extractcompare_entries()helper, use idiomaticzip+enumerate.