[zshenker]

Stacked on #6 (base: alg-confusion-fix). It only rebased onto #6 to avoid test-file conflicts; it doesn't depend on #6's API.

Problem

RFC 8392 §3.1 fixes the types of the registered claims. RegisteredClaims::from_map, which Token::from_bytes used, skipped any value of the wrong type and cast NumericDates with as u64. On the verification path that meant:

• A negative exp became a far-future time, so the token never expired.
• An iss, sub or aud of the wrong type was dropped, so the token passed expected_issuer / expected_audience unless require_iss / require_aud was also set.
• An array-valued aud was dropped too. Such a token passed any expected audience.

Change

• Token::from_bytes decodes registered claims with the new strict RegisteredClaims::try_from_map / Claims::try_from_map. A claim that is present but malformed fails with the new Error::InvalidRegisteredClaim.
• The required types are:
  • iss, sub: text
  • aud: text, or an array of text
  • exp, nbf, iat: non-negative integer NumericDates
  • cti: byte string
• An array-valued aud is kept and readable through the new Token::audiences(). expected_audience must match one of its entries.
• RegisteredClaims::from_map stays lenient, but it now skips negative dates instead of casting them.

Behavior change: a text cti used to be tolerated (test_cti_as_text_verifies_and_roundtrips) and is now rejected. RFC 8392 §3.1.7 defines cti as a byte string, and silently dropping it can defeat replay caches keyed on cti.

Non-integer NumericDates are rejected. RFC 8392 §2 permits floating-point NumericDates, and accepting them, rounding up, is a possible follow-up once #8 adds CborValue::Float. Until then, rejecting them fails closed. With #8 merged, a float exp is rejected rather than dropped, which is covered by a probe.

Tests

• New inline tests in src/claims.rs cover:
  • negative and non-integer dates
  • wrong-type iss, sub, aud and cti
  • an array aud with a non-text entry
  • matching against an array aud
  • leniency of from_map
• The cti-as-text test is converted to a rejection test.
• The aud-as-array test now also checks audiences().
• cargo fmt --check, cargo clippy --all-targets -- -D warnings and cargo test pass: 66 unit tests and 74 doctests.
• A local merge with Add Media over QUIC (MoQ) CAT support (draft-ietf-moq-c4m) #8, Gate PS256 and the rsa dependency behind a default-on ps256 feature #9, Reject COSE structure tags that disagree with the algorithm on decode #10 and Allow injecting the clock and a clock-skew leeway for exp/nbf verification #11 has no conflicts and passes with and without default features.

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