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State pdp_digest explicitly; decline to publish a vocabulary mapping

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flex-auth asked whether this engine should publish an action/target
mapping between the claim binding's vocabulary (secrets.kv.destroy,
{"id": "lane-openbao-root"}) and a policy package's (destroy, lane:...),
since their package makes no cross-check that a claim was approved for
the action being decided.

Answered no. A PIP asserting that one vocabulary's action means
another's would author policy semantics it does not own, over
vocabularies it does not own, and the failure mode is asymmetric: a wrong
mapping silently accepts a claim approved for a different action, which
is worse than no mapping. binding.pdp_digest is the correspondence and
sidesteps vocabulary entirely -- it compares the PDP's own digest to the
PDP's own digest, with no translation by anyone.

Implemented the part that was ours. pdp_digest was emitted only when
recorded, so a consumer could not distinguish "not issued against a
decision" from "we forgot to look". It is now always present and null in
that case, required-but-nullable in the schema, and documented as
something a PEP on a privileged lane must refuse. This engine states the
fact; enforcing the lane's policy stays with the consumer.

Both published examples were already contradicting the updated schema by
omitting the field -- the same fixture-versus-contract defect flex-auth
hit twice this week and that secrets-engine implemented. Fixed both, made
them cover the PDP-bound and unbound shapes so neither is inferred from
the other, and added tests/test_examples.py to validate every example
against the schema so the class cannot recur here. jsonschema added as a
dev dependency.

94 tests pass (6 new).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TvyJPAaVCGsVheVhcCwNND

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This commit is contained in:
tegwick 2026-09-06 09:32:11 +02:00
parent 87e55e2bca
commit 6d0dfc8010
8 changed files with 224 additions and 38 deletions
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14
workplans/APPROVAL-WP-0002-production-readiness-and-consumer-adoption.md
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@ -223,3 +223,17 @@ this engine's state transitions and its use outbox row under §9.6. Implemented:
with `approved_at` plus assurance/evidence refs). Tests prove reconstruction
from the use row alone and that the claim still discloses no approver
identities. Documented in `docs/outbox-contract.md`.
2026-09-06 follow-on (T05): flex-auth asked whether this engine should publish
an action/target vocabulary mapping between the claim binding and their policy
package before `SECRETS-WP-0007-T04` makes destroy reachable. Answered no, and
recorded why in `docs/approval-claim.md`: a PIP asserting that one vocabulary's
action *means* another's would author policy semantics it does not own, and a
wrong mapping silently accepts a claim approved for a different action.
`binding.pdp_digest` is the correspondence — it compares the PDP's digest to
the PDP's digest with no translation. Implemented the part that was ours:
`pdp_digest` is now always present on the claim and `null` when the approval
was not issued against a PDP decision, so absence is a stated fact rather than
a missing key, and the schema requires it as nullable. A PEP on a privileged
lane must refuse a null. Both published examples were contradicting the schema;
fixed, and `tests/test_examples.py` now validates every example against it.