key-cape/docs/tenant-claim-contract.md
tegwick 329e48f64a
All checks were successful
Build and Publish Container Image / build-and-push (push) Successful in 46s
Let a human token carry the zone it is issued into, without relabelling anyone
KEY-WP-0013-T05's tenant blocker did not need the decision it was waiting on. The
two proposed resolutions differ in where a human's tenant comes from -- the
directory record, or the client registration -- and an implementation exists that
is correct under either, so the choice can be made later without another
migration.

A client registration may now declare a tenant. humanTenant() resolves it by four
rules: no declaration keeps the directory answer unchanged; a declared zone
applies where the directory has placed the user nowhere; agreement passes; and a
declared zone conflicting with a directory assignment refuses issuance rather
than relabelling the user.

The refusal is the design, not an edge case. A registration can bind a zone for
unplaced users and can never move a placed one, so this gets the approval chain
its tenant:platform without writing a general cross-tenant override into the
issuer. It fails closed rather than picking a winner, because either answer would
be a silent cross-tenant assertion, and it reports 403 with
error_type: tenant_binding so an operator can tell a misconfigured registration
from a rejected login. If the owners later populate directory tenants, the same
code stops supplying the zone and starts enforcing agreement with it.

Safe only because client registrations are static and deployment-owned. The
tenant contract records that this rule must be revisited if dynamic client
registration is ever admitted.

Tests cover all four rules; neutering the conflict check fails the relabel test
rather than passing silently.

T05 now waits on one thing only: the client_id and callback URI from
informed-decision once it has a deployed origin.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016uV8zoCKpA1WRAxsKRYbdH

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1182213@bnt-lap001
Assistant-Session: 966597b9-ae61-46a4-8b9e-1594ab3ec4ad
2026-09-09 14:40:36 +02:00

129 lines
6.8 KiB
Markdown

# Tenant claim contract
States what KeyCape owns and emits for the `tenant` claim. Raised by glas-harness
message `356f6977-d361-4e3b-83ab-b2c7f4759286` (GLAS-WP-0015) and resolved by
operator decision `5ed3fb35-eca9-413a-82b9-95171ba85bf6` — "Use tenant:platform
for the Glas approval dependency chain", recorded in
`glas-harness/docs/platform-tenant-decision.md`.
`tenant:platform` is the platform management, administration and services tenant
(the landlord zone). KeyCape emits it verbatim for the two approval clients and
still creates no mapping between tenant vocabularies: no alias to `platform` or
`tenant:coulomb`, and no implicit cross-tenant grant.
## What KeyCape emits
The `tenant` claim is bound at registration or directory-resolution time and is
never influenced by request parameters.
| Principal | Source of `tenant` | Value in the reviewed registrations |
| --- | --- | --- |
| Service (`client_credentials`) | The client's `tenant` field. Required by config validation — a `client_credentials` client without `serviceSubject` and `tenant` fails startup validation. | In `config/service-clients.example.yaml`: `tenant:platform` for `secrets-engine-approval` and `approval-engine-operator`; `tenant:coulomb` for `codex-railiance-platform` and `secrets-engine-openbao`. |
| Human (`authorization_code`) | The directory user's tenant, falling back to the platform default when unset. | Directory value, else `tenant:coulomb`. |
`tenant`, `tenant_hint`, `audience` and `resource` request parameters cannot
change the claim. `tenant_hint` on `/authorize` reaches registration/enrollment
handoffs only; it is not a claim input.
## The approval chain, after the decision
All three layers now use one exact spelling, `tenant:platform`:
| Layer | Value | Owner |
| --- | --- | --- |
| Approval store tenant | `tenant:platform` | approval-engine |
| Service-client JWT `tenant` claim | `tenant:platform` | KeyCape (this repo) |
| Lifecycle CheckRequest tenant | `tenant:platform` | flex-auth |
KeyCape performs **no** normalization, prefix-stripping or aliasing, so a
resource server compares `tenant` as an exact string. The previously observed
`platform` and `tenant:coulomb` spellings are **not** accepted aliases for
`tenant:platform`; a token carrying either must be denied by the resource server.
## Scope of the alignment
The decision changed the `tenant` field on exactly two registrations,
`secrets-engine-approval` and `approval-engine-operator`, plus the matching
entries in `docs/approval-engine-provisioning-request.yaml`. Deliberately
unchanged:
- `codex-railiance-platform` and `secrets-engine-openbao` keep `tenant:coulomb`.
- Human directory resolution keeps its `tenant:coulomb` default.
- No cross-tenant grant is implied: a `tenant:platform` token conveys no reach
into `tenant:coulomb` resources, and audiences, scopes, subjects, roles,
lifetimes and MFA requirements are untouched.
This resolves the *choice* of tenant only. Live provisioning of the two clients
remains gated on deployment-owned custody and the separate verification gates in
KEY-WP-0013-T02; KeyCape changed no live registration or policy subject.
## Evidence
`src/internal/server/oidc/tenant_test.go`:
- `TestServiceTenantIsBoundToRegistrationAndIgnoresRequestParameters` — a request
supplying `tenant=tenant:platform` and `tenant_hint=platform` still yields the
registered `tenant`, signature-verified against `/jwks`.
- `TestServiceTenantsAreDistinctPerRegistration` — two registrations with
different tenants yield their own values and never each other's; this is the
wrong-tenant denial basis for an exact-comparison resource server.
- `TestHumanTenantClaimUsesDirectoryValueThenPlatformDefault` — human tokens carry
the directory tenant, defaulting to `tenant:coulomb` rather than an empty claim.
- `TestApprovalClientIssuesExactPlatformTenantAndRejectsAliases` — the
approval-client shape issues `tenant:platform` exactly, with
`aud=approval-engine`, even when the caller asks for `platform`,
`tenant:coulomb` or `TENANT:PLATFORM`.
- `TestUnrelatedServiceClientKeepsCoulombTenant` — the OpenBao login client keeps
`tenant:coulomb` even when the request asks for `tenant:platform`, so the
alignment grants no cross-tenant reach.
`src/cmd/keycape/clients_test.go`:
- `TestServiceRegistrationTenantsAreExactPerDecision` — loads the real
registration fixture and pins the exact tenant of every reviewed client, so
drift or an alias reintroduced into `config/service-clients.example.yaml` fails
the build.
## How a human token's tenant is resolved (KEY-WP-0013-T05)
A human's tenant is normally a property of the person, read from the directory
record. That alone could not serve the approval chain: decision
`5ed3fb35-eca9-413a-82b9-95171ba85bf6` binds it to the landlord zone,
approval-engine compares the claim by exact string equality, and no adapter
populates `domain.User.Tenant` — so every human token fell back to
`tenant:coulomb` and an approver token would have been refused downstream. It
would have presented as a failed approval rather than as a registration defect.
A client registration may therefore declare a `tenant`, and `humanTenant` in
`src/internal/server/oidc/token.go` resolves it by these four rules:
| Client declares | Directory assigns | Result |
| --- | --- | --- |
| nothing | anything | the directory answer, or `tenant:coulomb` — unchanged |
| a zone | nothing | the declared zone |
| a zone | the same zone | that zone; client and directory agree |
| a zone | a **different** zone | **issuance is refused** |
The last row is the point. A registration can bind a zone for users the
directory has not placed, and can never relabel a user it *has* placed. That
case fails closed rather than picking a winner, because either answer would be a
silent cross-tenant assertion. The refusal is a `403` with
`error_type: tenant_binding`, distinct from an authentication failure, so an
operator can tell a misconfigured registration from a rejected login.
This also means the design survives the other resolution. If the directory later
carries tenants, the same code stops supplying the zone and starts enforcing
agreement with it — no second migration, and no window in which a stale
registration silently wins.
It is safe only because client registrations are static and deployment-owned.
KeyCape excludes dynamic client registration by design; a self-service client
able to name its users' tenant would be a straightforward escalation, and this
rule must be revisited if that exclusion is ever lifted.
Covered by `src/internal/server/oidc/human_tenant_test.go`, including the
relabel refusal.
These are local issuance proofs. They are not live-rollout evidence; see
`docs/approval-engine-auth-contract.md` and KEY-WP-0013-T02 for the deployment
boundary. No token or secret values appear in this document or in test output.