9b5fbc9b5e
- Add decode_page_content_streams() function for per-page lazy decode - Update extract_page_from_dict() to support lazy stream decoding - Modify extract_pdf() and extract_pdf_ndjson() to enable lazy decoding - Fix borrow checker issue in LazyPageIter::next() This ensures content streams are decoded lazily per page and dropped immediately after processing, keeping peak RSS flat across page count. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
52 lines
2.4 KiB
Markdown
52 lines
2.4 KiB
Markdown
# ADR-003: RUSTSEC-2020-0144 Advisory Exception for lzw Crate
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## Status
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Accepted
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## Context
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The lzw crate (v0.10.0) is subject to RUSTSEC-2020-0144, which marks the crate as
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unmaintained. pdftract uses the lzw crate to implement the LZWDecode filter for PDF
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streams, as specified in the PDF 1.7 specification (section 7.4.4).
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## Decision
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RUSTSEC-2020-0144 is explicitly ignored for the lzw crate until a viable alternative
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becomes available.
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## Rationale
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- LZW is a **mandatory PDF filter** - the PDF spec requires LZWDecode support for full compliance
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- The lzw crate is the only Rust LZW implementation compatible with PDF LZW encoding
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- Alternative crate (weezl) is **incompatible** with PDF LZW:
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- PDF LZW uses "early code change" variant (code tables reset at 256 vs 257)
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- weezl only supports standard LZW (GIF/TIFF variants)
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- PDF test fixtures fail to decode correctly with weezl
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- The lzw crate is simple (~400 LOC) and has been stable for years
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- No security vulnerabilities have been reported in the lzw algorithm implementation
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- The "unmaintained" status reflects lack of new features, not security issues
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## Alternatives Considered
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- **weezl crate**: Incompatible with PDF LZW encoding (early code change variant)
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- **Pure Rust implementation**: Would require re-implementing and testing ~400 LOC of complex bit manipulation
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- **C binding (libtiff)**: Violates pdftract's zero-dependency-beyond-libc goal
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## Risk Assessment
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- **Low risk**: The lzw crate is small, stable, and handles a well-defined algorithm
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- **No known CVEs**: RUSTSEC-2020-0144 is about maintenance status, not a specific vulnerability
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- **Contained scope**: LZW decoding is a single, well-tested code path
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- ** fuzzing**: The LZW decoder is covered by the project's fuzzing harness
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## Consequences
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- pdftract can continue using the lzw crate for LZWDecode filter support
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- This exception will be re-evaluated if:
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- A security vulnerability is discovered in lzw
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- A compatible Rust LZW library becomes available
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- PDF spec changes remove the LZW requirement
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## Future Work
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- Monitor the weezl crate for PDF-compatible LZW support
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- Consider contributing PDF LZW variant to weezl
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- Re-evaluate this ADR annually or upon security reports
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## References
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- RUSTSEC-2020-0144: https://rustsec.org/advisories/RUSTSEC-2020-0144
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- lzw crate: https://crates.io/crates/lzw
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- PDF 1.7 spec, section 7.4.4: LZWDecode filter
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