api-authorization-testing
Skill0 starsChanged 11 days agoMITView on GitHub
Test API authorization defensively — broken object-level authorization (BOLA/IDOR), broken function-level authorization, broken object property level authorization (mass assignment, excessive data exposure) and tenant isolation — with multi-user test matrices in authorized environments. Use when validating an API before release, investigating a suspected IDOR, or building automated authorization regression tests.
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- Distinctive: line 45
Only in environments and accounts you are authorized to test.
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Files
API Authorization Testing
OWASP API Top 10 2023: API1 BOLA, API3 Broken Object Property Level Authorization, API5 Broken Function Level Authorization — the most common serious API flaws.
Test setup (staging or authorized test tenant)
- At least two users per role in two different tenants:
userA@tenant1,userB@tenant1,userC@tenant2, plus an admin and an unauthenticated client. - Objects owned by each user (orders, documents, profiles).
- Capture requests from the app/spec (Burp/ZAP proxy, OpenAPI).
Test matrix
| Test | Method | Expected |
| BOLA | Replay GET/PUT/DELETE /orders/{idOfUserA} with userB and userC tokens | 403/404, no data, logged |
| ID guessability | Are IDs sequential? UUIDs don't fix BOLA but reduce enumeration | Authorization still enforced |
| Function level | Call admin endpoints (/admin/*, POST /users/{id}/roles) with user token; try HTTP method switching (GET→DELETE) | 403 |
| Mass assignment | Add fields to updates ("role":"admin", "tenantId":"other", "price":0, "isVerified":true) | Ignored or rejected |
| Excessive data exposure | Inspect responses for fields not shown in UI (password hashes, tokens, other users' PII) | Only necessary fields |
| Tenant isolation | Use tenant-scoped IDs across tenants; filter params (?tenant=) manipulation | Denied |
| GraphQL | Query objects by ID via nested resolvers; introspection in prod | Per-resolver authorization |
Example with curl:
curl -s -H "Authorization: Bearer $TOKEN_USER_B" https://staging.example.com/api/v2/orders/1001 -o /dev/null -w '%{http_code}\n'Automate as integration tests in CI (parametrized over user × object × endpoint) so regressions are caught.
Fix guidance
Enforce authorization in a central layer using the authenticated principal (never IDs from the client to determine ownership), deny by default, response DTO allow-lists, schema validation rejecting unknown fields.
Safety
Only in environments and accounts you are authorized to test; do not access real customer data — if a production IDOR is found during incident work, stop, record minimal evidence, and escalate.
Related skills
api-schema-security, secure-code-review, dast-baseline, api-abuse-detection
References
- OWASP API Security Top 10 2023: https://owasp.org/API-Security/editions/2023/en/0x11-t10/
- OWASP Authorization Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Authorization_Cheat_Sheet.html
- OWASP WSTG Authorization Testing: https://owasp.org/www-project-web-security-testing-guide/
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