Christian Nennemann
8cf0d8aade
Draft improvements: - Rename ext -> ect_ext, clarify iss/aud requirements per level - Add algorithm agility guidance and RFC 8725 reference - Add HTTP header size constraints and body transport fallback - Add cross-level parent reference semantics - Add emerging agent protocols (A2A, MCP) to Related Work - Fix HTTP error handling (403 not 401), IANA +jwt suffix note - Add workflow consistency check to DAG validation - Add defense-in-depth note for acyclicity check Supporting files: - Fix blog post outdated claim names (par -> pred, ext -> ect_ext) - Update refimpl README with -00 vs -01 migration mapping - Add refimpl IMPROVEMENTS.md section 6 with -01 migration tasks
76 lines
3.9 KiB
Markdown
76 lines
3.9 KiB
Markdown
# Possible Improvements (Go & Python Refimpls)
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Suggestions that could make the implementations more robust, spec-strict, or production-friendly. **All items below have been implemented** in both refimpls unless noted.
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---
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## 1. **Spec alignment** ✅
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- **ext size/depth (Section 4.2.7)**
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**Done.** Both refimpls reject when serialized `ect_ext` exceeds 4096 bytes or JSON depth exceeds 5 (`ValidateExt` / `validate_ext`). Used in create and verify.
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- **jti / wid format**
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**Done.** Optional UUID (RFC 9562) validation: `CreateOptions.ValidateUUIDs` / `VerifyOptions.ValidateUUIDs` (Go), `validate_uuids` (Python). Helpers: `ValidUUID` / `valid_uuid`.
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---
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## 2. **API and safety** ✅
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- **Payload mutation in Create**
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**Done.** Documented in both: Create may set Iat, Exp, Sub, Par when zero/nil. **Go:** comment on `Create()`; **Python:** create works on a deep copy so the caller’s payload is not modified.
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- **Structured errors (Go)**
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**Done.** Sentinel errors in `ect/errors.go`: `ErrExpired`, `ErrReplay`, `ErrInvalidSignature` (wrapped), `ErrInvalidTyp`, `ErrPolPolDecisionPair`, etc. Verify and create return these where applicable.
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---
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## 3. **Production / operations** ✅
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- **Replay cache**
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**Done.** Documented: JTICache is in-memory; for multi-instance deployments a shared store (Redis, DB) is required. See refimpl README and go-lang/README “Replay cache (multi-instance)”.
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- **Observability**
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**Done.** **Go:** `VerifyOptions.LogVerify func(jti string, err error)` called after each verify. **Python:** `VerifyOptions.on_verify_attempt(jti, err)` callback.
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---
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## 4. **Small cleanups** ✅
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- **Python Ledger docstring**
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**Done.** “Lookup by task id (jti)”.
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- **Python `verify`**
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**Done.** Documented that `par` may be set to `[]` when missing; `from_claims` already supplies `[]`, so mutation is defensive only.
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- **par length**
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**Done.** **Go:** `CreateOptions.MaxParLength`, `VerifyOptions.MaxParLength`, `DAGConfig.MaxParLength` (0 = no limit; default 100 in DAG). **Python:** `CreateOptions.max_par_length`, `VerifyOptions.max_par_length`, `DAGConfig.max_par_length`.
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---
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## 5. **Nice-to-have** ✅
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- **inp_hash / out_hash format**
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**Done.** Optional check in create and verify: `algorithm:base64url` with algorithm in allowlist (sha-256, sha-384, sha-512). Helpers: `ValidateHashFormat` / `validate_hash_format`.
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- **Constant-time comparison**
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**Done.** **Go:** `crypto/subtle.ConstantTimeCompare` for `typ` in verify. **Python:** `hmac.compare_digest` for `typ`.
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---
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**Summary:** All listed improvements are implemented. For production, also consider: key rotation, WIT integration, and metrics around verify/create latency and error kinds.
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---
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## 6. **draft-01 migration** (NOT YET IMPLEMENTED)
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The refimpl was built against draft-nennemann-wimse-ect-00. The -01 draft introduced breaking changes that need to be reflected:
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- **Rename `par` to `pred`**: The predecessor claim was renamed. Update struct fields, JSON tags, serialization/deserialization, tests, and testdata.
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- **Remove `pol` and `pol_decision`**: Policy claims were removed from the core spec. Deployments should use `ect_ext` for domain-specific claims like policy decisions.
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- **Remove `sub`**: The `sub` claim is not part of the ECT specification. Remove from types and examples.
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- **Update `typ` default**: Prefer `exec+jwt` over `wimse-exec+jwt`. Both must be accepted for backward compatibility.
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- **Add L1 support**: The -01 draft introduces unsigned JSON ECTs (Level 1). The refimpl currently only supports L2 (signed JWS).
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- **Add L3 support**: The -01 draft introduces audit ledger requirements for Level 3. The existing in-memory ledger needs hash chain and receipt support.
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- **Update `MaxParLength` naming**: Rename to `MaxPredLength` to match the new claim name.
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- **Update hash format**: The -01 draft specifies SHA-256 base64url without algorithm prefix (no `sha-256:` prefix), consistent with RFC 9449.
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