flex-auth/docs/decision-record-contract.md
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fix: the address we published was a misdirection, and the channel is unauthenticated
secrets-engine probed the Service DNS name handed over in FLEX-WP-0021-T05
and found it resolves, from the workstation, to an unrelated public host.
Reproduced here: search ad.binect.de answers wildcard, so
flex-auth-secrets-engine.flex-auth.svc.cluster.local and
this-service-does-not-exist.flex-auth.svc.cluster.local both resolve to
80.158.43.29, while the trailing-dot FQDN correctly fails. A bare Service
name in a handover is not merely unreachable from there, it is a live
misdirection, and the handover was ours.

Had a deployment pointed at it, the CheckRequest body would have gone to
that host: subject, tenant, lane and resource ids, stage, field names,
purpose, plus the caller's bearer token.

Trailing-dot FQDN and "in-cluster only" now replace the bare name in the
example README, SCOPE.md, and the T05 note.

Their real question was how the response channel is authenticated, and
they declined to answer it locally because choosing a transport control
for our service is not a consumer's call. Right boundary, so the answer
is recorded here as FLEX-DEC-2026-010: it is not authenticated. Pins
serve plain HTTP, the envelope carries no signature, and a responder that
knows the package id and version can return a well-formed allow that
passes every check a consumer performs.

The part worth stating in the contract is that the digests do not help
and look like they do. Every input to request_digest,
policy_package_digest and registry_snapshot_digest is either sent by the
caller or published in this repo, so a forger reproduces all three
exactly. They establish integrity of the binding, never authenticity of
the source — and publishing more digests makes a forged envelope look
more authenticated, not less.

For secrets-engine specifically: fail-closed protects against a PDP that
is absent, not against one that lies. An unreachable PDP denies; a lying
PDP allows.

Third instance of one seam in three decisions. 008: a tenant carried
into the digest and never compared — visible, not enforced. 009: a caller
authenticated and never recorded — enforced, not visible. 010: a record
verifiable and unauthentic — checkable, but not evidence.

One nuance that changes the operator recommendation: kubectl port-forward
does authenticate the responder, transitively — no DNS name, one named
pod, API-server TLS. That is the exact reverse of the caller direction,
where it bypasses the NetworkPolicy. Independent properties pointing
opposite ways, so neither can be summarised as "the network protects it".

FLEX-WP-0024 carries signing; key custody routes through warden/OpenBao
rather than minting a key here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014aQMM1dPXaPiXVn6DwwtLd

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 715613@bnt-lap001
Assistant-Session: fabd95c1-4c9e-4080-8849-8707ae025f80
2026-09-06 22:44:45 +02:00

4.1 KiB

Decision-record contract

Status: published Contract: flex-auth.decision-record.v1 Schema: ../schemas/decision_envelope.schema.json Date: 2026-09-02

This is flex-auth's output artifact under the NetKingdom Security Layer Model v0.7 §17. Taxonomy holds only the shared field vocabulary. Consumers may rely on this schema.

A decision record is a DecisionEnvelope returned by POST /v1/check and the CLI check / batch-check / list-allowed commands. Standalone evaluation and every delegated adapter (Topaz, relationship, rule, Keycloak) emit the same shape.

Required fields

Field Meaning
id Deterministic decision identifier
effect allow, deny, redact, audit_only, or not_applicable
subject / resource Normalized refs the evaluator used
provenance Who evaluated, over which policy and facts

Contract fields consumers may rely on

Field Meaning
contract_version flex-auth.decision-record.v1
binding Structured subject, action, resource, context, and request_digest
binding.approval_binding_digest Present only when the request carried context.approval. The digest an approval's pdp_digest must equal — see canonical-request-digest.md. Not a replay identity
lifetime Required on every allow. A TTL with not_before and expires_at
provenance.policy_package / policy_version Named package pin
provenance.policy_package_digest SHA-256 of package metadata plus compiled Rego
provenance.registry_snapshot_digest SHA-256 of the canonical registry snapshot
provenance.directory_etag Directory consistency token when a delegated directory was joined
provenance.input_claim_digests SHA-256 per request-time claim class (context, caring_context)
provenance.decision_time UTC timestamp used to compute lifetime

reason, diagnostics, and CARING prose are not an authorization contract.

Allow lifetime

Every allow carries lifetime.kind = ttl. The duration comes from the policy package allow_ttl field, or from the engine default of 15m when the package omits it. A package that declares allow_ttl: none (or 0s) produces a deny with reason allow_lifetime_unstated instead of a standing grant.

Replay is permitted only while lifetime.expires_at is still in the future. See canonical-request-digest.md and decision-input-freshness.md.

Versioning

This is contract version 1. Additive optional fields may appear. Removing or redefining a required field requires a new contract_version value and a new schema id.

What this record does not prove: who answered

A consumer must not read digest recomputation as verification of the responder. Recomputing binding.request_digest, provenance.policy_package_digest, and provenance.registry_snapshot_digest and finding all three correct says nothing about who produced the envelope.

Every input to those digests is either sent by the caller or published: the request material is what the caller just transmitted, and both the package and registry digests are computable from files in this repo. A responder that knows the package id and version can reproduce all three exactly. The digests establish integrity of the binding, never authenticity of the source.

flex-auth.decision-record.v1 carries no signature today, and pins serve plain HTTP. So the response channel is unauthenticated, stated as a stance rather than left as an assumption (FLEX-DEC-2026-010). For a fail-closed consumer the distinction that matters is this: fail-closed protects against a PDP that is absent, not against one that lies. An unreachable PDP denies; a lying PDP allows.

A detached signature over the canonical envelope is the intended fix (FLEX-WP-0024). Until it lands, responder authenticity comes from the channel alone — and of the available channels only kubectl port-forward supplies it, by targeting one named pod over the API server's TLS with no DNS name resolved.