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M9: more signature validation algorithms (SHA-3, RIPEMD-160, Ed25519, P-521, brainpool, PSS, rsa_sha1) (#386)

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* M9: more signature validation algorithms

Validation now reads what real signers write, and says when it is weak:

- Digests SHA-224, SHA-512/224, SHA-512/256, SHA3-224/256/384/512 and
  RIPEMD-160, beside SHA-1 and SHA-2.
- RSA PKCS#1 v1.5 for every digest, in `rsa_pad`: the one expected encoding
  is built and compared byte for byte, with or without the DigestInfo's NULL
  (RFC 8017 App. B.1). A signature over the bare digest, which doesn't say
  which hash it uses, is refused. The signature value must be below the
  modulus (RFC 8017 §5.2.2); s and s + n both verified before.
- RSA-PSS with the hash, MGF1 hash and salt length the signature declares.
- ECDSA as DER, non-minimal DER or raw r||s on P-256, P-384, P-521 and
  brainpoolP256r1/P384r1/P512r1 (BSI "plain" ECDSA OIDs too); brainpoolP512r1
  is hand-written on crypto-bigint because no RustCrypto crate has it.
- Ed25519 (RFC 8419), and the legacy adbe.x509.rsa_sha1 format.
- An algorithm PdfCraft can't check is Unknown, never Invalid.
- SHA-1 and RIPEMD-160 signatures validate, but the signature's details say
  the algorithm is weak (wording pinned by tests).
- Encoding irregularities that were tolerated are listed in the details
  (`verify_noting`; `verify` keeps its signature).

Found while testing, each with a regression test that failed before the fix:
a brainpoolP512r1 public key with a coordinate >= p panicked inside
crypto-bigint's `sub_mod` (the certificate comes from the PDF); it is refused
now, and the point at infinity is an invalid signature, not an error.

Vectors were made with OpenSSL (tests/data/README.md has the commands).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

* Update comment to clarify MAC digest restrictions

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* M9: a legacy x509.rsa_sha1 signature whose key the verifier rejects is Invalid; only unsupported keys are "can't check yet"

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
This commit is contained in:
Thorsten Hirsch
2026-10-09 18:44:38 -04:00
committed by GitHub
co-authored by Claude Sonnet 5.5 Copilot Autofix powered by AI Brandon Thomas
parent c957288d3b
commit 56f85f76df
21 changed files with 1508 additions and 106 deletions
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ATTRIBUTION.md
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@@ -4,7 +4,7 @@
Every asset PdfCraft includes, bundles or uses to build its published material, with its author, source and licence. The policy is in [AGENTS.md](AGENTS.md) §1. The machine-readable list, with SHA-256 hashes, is [ATTRIBUTION.toml](ATTRIBUTION.toml). Licence texts are kept beside the assets and summarised in [NOTICE](NOTICE).
## In this repository (257)
## In this repository (258)
| Asset | Title | Author | Licence | Source | Used for |
|---|---|---|---|---|---|
@@ -265,6 +265,7 @@ Every asset PdfCraft includes, bundles or uses to build its published material,
| `assets/fonts/DancingScript.ttf` | Dancing Script (variable) | The Dancing Script Project Authors (Pablo Impallari) | OFL-1.1 | https://github.com/google/fonts/blob/9710da1eacb3be272583c3224dcb70f9da6eadbb/ofl/dancingscript/DancingScript%5Bwght%5D.ttf | Fill & Sign typed signatures and initials: the typed name's glyph outlines, drawn as filled paths (the font file itself is not embedded in PDFs) |
| `packaging/macos/dmg/background.svg` | PdfCraft macOS DMG window background | @XusBadia | MIT OR Apache-2.0 | Original work for this repository, derived from the PdfCraft app icon (assets/app-icon/pdfcraft.svg, referenced via an SVG image element, not copied) | Finder window of the macOS DMG; rendered to background.tiff by packaging/macos/dmg/generate.py |
| `packaging/macos/dmg/background.tiff` | PdfCraft macOS DMG window background (rendered) | @XusBadia | MIT OR Apache-2.0 | Rendered from packaging/macos/dmg/background.svg by packaging/macos/dmg/generate.py | 1x + 2x HiDPI 16-colour palette TIFF copied into the macOS DMG by packaging/macos/package.sh; includes the app icon and the free LittleCMS built-in sRGB profile |
| `crates/sign/tests/data/x509-rsa-sha1.pdf` | One-page PDF with a legacy adbe.x509.rsa_sha1 signature by the RSA test key | PdfCraft contributors | MIT OR Apache-2.0 | Contributor-original: hand-written PDF objects; signature made with `openssl dgst -sha1 -sign` over its byte ranges (see crates/sign/tests/data/README.md) | Signature validation tests (crates/sign/tests/pdf.rs): the legacy adbe.x509.rsa_sha1 format |
## Compiled in through dependencies (6)