Ownership Authorization

Ownership Authorization

Purpose

Design the resource-bound authorization layers: ownership (this caller's resource), organization/tenant scope (inside the caller's org), and object-level rules (sharing, state-dependent access). These sit after role/permission checks and prevent IDOR/BOLA — the most common real-world authorization failure.

When to Use

• Whenever resources belong to users or organizations, or have per-object access rules.
• Not for action-class gating — that's role-permission-design.

Inputs

• Domain model: which entities have owners/orgs; sharing rules.
• Authorization matrix (backend-authorization); data layer (../../database/).

Discovery Questions

• For each entity: owned by a user, scoped to an org/tenant, both, or global?
• Are resources ever shared (explicit grants, links, public flags)? State-dependent access (draft vs published)?
• Where does the caller's user/org context come from at request time (session/claims — never the payload)?
• On unauthorized access to an existing ID: 403, or 404 to hide existence?

Responsibilities

• Map each entity to its scope model (owner / tenant / owner-within-tenant / shared / global-read).
• Enforce in the query: filter by owner/tenant from session context (WHERE user_id = session.userId / org_id = session.orgId) so unauthorized rows are never loaded — not fetch-then-check (which invites forgotten checks and leaks via error variance).
• Route derivation of scope from the session only: client-supplied userId/orgId in body/query/params are for locating within the caller's scope at most, never for widening it.
• Design object-level rules (grants tables, share links, status-based visibility) as explicit policy checks alongside the scope filter.
• Fix failure semantics (403 vs 404) per entity class with backend-error-handling.
• Require negative tests:
  • User A requests User B's resource ID → rejected (403/404 per policy).
  • Cross-tenant ID access → rejected, even with a valid guessed/enumerated ID.
  • Payload userId/orgId pointing elsewhere → ignored; scope stays the session's.
  • Shared-resource rules: non-grantee rejected, revoked grant rejected.

Required Workflow

1. Build the entity × scope-model table.
2. Define query-level filters and where session context enters the data layer (e.g. repository helpers that require a scope).
3. Define object-level policies for shared/stateful access.
4. Fix 403-vs-404 semantics per entity.
5. Specify the negative-test suite; wire into backend-integration-testing.

Decision Rules

• Scope in the query beats check-after-load; make unscoped queries on scoped entities impossible-by-default (scoped repository methods) where the data layer allows.
• Multi-tenant: every query on tenant data carries the tenant filter — including background jobs, exports, and admin tooling (admin cross-tenant access is its own audited permission, not a missing filter).
• Creation is scoped too: new resources take owner/tenant from the session, not the payload.
• Prefer 404 for existence-hiding on private resources; 403 where existence is already known (own-org objects without permission).

Rules

• No endpoint or job touches scoped data without a scope derivation recorded.
• Client-supplied ownership IDs are never trusted (backend-validation validates shape; this skill removes trust).
• Every scoped entity ships with cross-user/cross-tenant negative tests.

Anti-Patterns

• findById(params.id) with no owner/tenant filter (classic IDOR).
• Trusting body.orgId because "the client sends the right one."
• Scoping reads but not updates/deletes — or HTTP but not background jobs.
• Sequential integer IDs plus 403/404 variance leaking existence.
• Assuming role checks made ownership checks unnecessary.

Validation Checklist

• Entity × scope-model table recorded.
• Scope enforced in queries from session context.
• Object-level/sharing policies explicit.
• Creation takes scope from session.
• 403/404 semantics fixed per entity.
• Negative tests: cross-user, cross-tenant, payload-ID-ignored, revoked-grant.

Definition of Done

A recorded scope model per entity with query-level enforcement from session context, explicit object-level policies, fixed failure semantics, and a negative-test suite proving cross-user and cross-tenant access is rejected and client-supplied IDs are not trusted.

Related Skills

backend-authorization, role-permission-design, backend-validation, backend-error-handling, backend-integration-testing, ../../database/database-security, ../../security-review.

Related Knowledge

../../../knowledge/ (tenancy model, sharing rules).

Related References

../../../references/backend/auth/ (scope-model table, when populated).

Context Loading Guidance

• Requires: entity/ownership model, session context shape, authorization matrix.
• Does not require: role taxonomy detail, login flows.
• May load: backend-authorization, ../../database/database-security.
• Stop when: scope models, enforcement points, and negative tests are recorded.

Token Efficiency Guidance

The entity × scope table plus the negative-test list is the deliverable; keep enforcement description to where the filter lives, not repeated query code.