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Threat Model

What we defend

The action-ref conformance harness produces verdicts (PASS/FAIL/CONFORMANT/NON-CONFORMANT) that other implementations may rely on to validate their action_ref derivations. A wrong verdict has real consequences: an implementation marked PASS may be deployed into production with an incorrect hash, or an implementation marked FAIL may be rejected when it is actually correct.

Adversary classes

1. Malicious vector submitter

Goal: Submit a vector designed to produce a false PASS, making the harness endorse an incorrect implementation. Controls: Schema validation, 4-field extraction (extra fields ignored), vendored canonicalization with integrity check, self-test canary. Vectors are run deterministically; the submitter cannot influence the verifier logic.

2. Supply chain attacker

Goal: Compromise the canonicalization dependency to silently alter hash output. Controls: canonicalize@3.0.0 is vendored (not fetched from npm at runtime). SHA-256 integrity hash checked in CI. Self-test canary runs against a known-good vector before every verification. Any canonicalization drift fails the build.

3. Spec drift attacker

Goal: Evolve the spec in a way that invalidates existing conformance verdicts without detection. Controls: Every verdict is anchored to a spec version and harness commit. Historical verdicts are immutable. CONFORMANCE_INTAKE.md requires vectors to declare the spec version they target.

4. Dispute gaming attacker

Goal: Exploit the dispute process to force removal of a legitimate FAIL verdict. Controls: Dispute process (see CONFORMANCE_INTAKE.md) requires reproduction evidence. Verdicts are not removed; they are superseded by new verdicts with updated spec/harness references.

5. Canonicalization edge case attacker

Goal: Find a JSON input where our JCS implementation diverges from RFC 8785, producing a silently wrong hash. Controls: Vendored implementation tested against RFC 8785 Appendix B reference vectors. Adversarial vectors targeting known JCS edge cases (negative zero, Unicode sorting, number serialization, key ordering). CI matrix runs on Node 18/20/22 to catch runtime-specific behavior.

Out of scope

  • Network attacks on hosted endpoints (the CLI is the source of truth, not any API)
  • Compromise of the GitHub account (standard GitHub security practices apply)
  • Attacks on the x402 protocol itself (we verify conformance to the spec, not the spec's correctness)

Open risks

  • The vendored JCS implementation has not been formally audited against the complete RFC 8785 test suite (Appendix B has 18 test groups; we cover the most critical ones)
  • No memory-safe implementation exists; the Node.js runtime is the trust boundary
  • The conformance page is manually maintained; automated generation from CI artifacts is planned