Object-Level Authorization & IDOR Defense Scope actual database lookups by authenticated relationships
Phase 19 - Authorization, Ownership, RBAC & Permissions Volume 05 - Authentication & Security
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Phase 19 transforms verified identity into contextual, server-side authorization decisions.
Object-level authorization prevents IDOR/BOLA Changing /tasks/A to /tasks/B must never grant access simply because B is a syntactically valid ID. The server must scope the actual database lookup by the authenticated user relationship.
const task = await prisma.task.findFirst({ where: { id: taskId, project: { workspace: { memberships: { some: { userId: user.id } }, }, }, }, })
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The query itself helps enforce tenant/resource scope.
Why this is stronger than checking after findUnique A global findUnique first reveals that the object exists and creates more room for accidental authorization omissions. Scoped lookup makes the accessible dataset smaller by construction.
Authorization decides what an authenticated identity may do to a specific resource. UI hiding is never a substitute for server-side enforcement.
Restate the goal of “Object Level Authorization and IDOR Defense” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: trusted identity → requested action → resource scope → policy decision → allow/deny. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: Permission model + guards/policies protecting TaskFlow workspace/task actions with deliberate 401/403/404 semantics.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
const canEdit =
user.role === "ADMIN" ||
(user.role === "MEMBER" && task.ownerId === user.id);
if (!canEdit) throw new ForbiddenException();Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Trace verified identity, role, resource owner/workspace, and policy inputs separately.
Add server-side resource authorization; UI visibility is only experience, never enforcement.
Without copying the final source, create a second small scenario that applies “Object Level Authorization and IDOR Defense” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Decide when 403 reveals too much and when a 404-style response better protects resource existence.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Authorization only in frontend
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.