[atiernan]

Stacked on #14, parallel to #15 (both add a section to the new crates/clazel-x509/README.md, so whichever lands second needs a trivial merge). This is the x509-limbo conformance corpus from Phase 3 §3.5b.

Vendored

crates/clazel-x509/tests/data/x509-limbo/ holds:

• limbo.json, byte for byte from C2SP/x509-limbo 1080e565f26e544bbe9cf99953be8a57c08e7e20: 41,791,455 bytes, SHA-256 611e337b…acd4de, re-checked locally;
• upstream's LICENSE (Apache-2.0) as LICENSE.md;
• SOURCE.md, which notes that upstream's README claims Apache-2.0 / MIT but the repo ships only the Apache text.

Derived (ours, reproducible)

The xtask testdata converter xtask/src/testdata/x509_limbo.rs writes:

• tests/generated/x509_limbo.rs, a 3.3 MB index of the testcases;
• tests/generated/x509_limbo_certs.bin, 17.4 MB holding the 30,379 distinct certificate DERs.

It does not turn the 41.8 MB of JSON into Rust literals. testdata.rs gains EXTRA_OUTPUTS, so cargo xtask check also fails on a stale or orphaned binary output. The converter decodes PEM with its own small strict base64 decoder, because clazel-base64 would pull vstd into xtask. It adds no new dependencies.

Harness (tests/conformance_limbo.rs; 0.46 s in debug; ignored under Miri)

• Every one of the 30,379 certificates runs through every existing decoder, with the accepted counts pinned.
• All 927 SERVER testcases that expect SUCCESS for a DNS or IP peer name are accepted by check_leaf_certificate.
• No certificate in any SUCCESS testcase is rejected by any decoder.
• The other 8,875 testcases are listed by id with a reason in tests/limbo/not_yet_supported.rs. Most say "needs path validation (3.5b)"; others need CRL checking, chain-search limits, ML-DSA or client-certificate validation. The test fails if an id appears or disappears, or if a listed case starts passing.

Findings

• No decoder bugs.
• rfc5280::ca-as-leaf and pathlen::validation-ignores-pathlen-in-leaf expect SUCCESS under RFC 5280, but our stricter WebPKI leaf policy rejects a CA:TRUE leaf. They are listed as a policy difference. mozilla::pkix makes the same choice: it rejects a CA certificate used as an end entity.

Local results

I re-ran these:

• cargo xtask check reported STATIC CHECKS PASSED, with both derived files up to date.
• cargo test -p clazel-x509 gives 56 passed, 0 failed.
• cargo fmt --all --check and strict clippy (clazel-x509, xtask) are clean.

No Verus or full verify was run. Intermediate commit e4fe0b2 has a failing test, which 208d884 fixes. The crate stays at tier 0.

🤖 Generated with Claude Code