Accept old and new webhook signatures only during a bounded overlap
The supplier rotates signing keys gradually across senders. Switching instantly drops valid traffic; retaining every old key forever defeats retirement.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Key rotation · Validity windows · Input trust boundaries
Estimated field mix
- Security70%
- Integrations30%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional supplier integration signs incoming webhooks and uses an outbound API credential. Operators currently replace environment values by hand. Build with a deterministic secret-store adapter and fabricated keys only; no live provider account or production credential is part of the exercise.
Setup prerequisites
- Cryptographic hash APIs
- HTTP webhook handling
- Access control
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- VAULT-101 · Inventory credential consumers without exporting their values
- VAULT-102 · Move secret lookup behind a version-aware provider
- VAULT-103 · Redact credentials from failed supplier requests
- VAULT-104 · Model credential activation and retirement as explicit transitions
- VAULT-105 · Verify signed webhooks against raw bytes before parsing
Acceptance criteria
- Accept only the configured active and retiring versions during their explicit validity windows.
- Reject retired or revoked versions regardless of timestamp tolerance.
- Record the non-secret verifying version identity for accepted webhook receipts.
Implementation constraints
- Bound the candidate key set; an untrusted key ID cannot trigger arbitrary provider lookups.
Verification to include
- Accept both fixture versions inside overlap and only the new version after retirement.
- Try a revoked version and an unknown attacker-controlled key ID; assert rejection without broad lookup.
Deliverables
- Signing overlap policy and boundary-time tests
Rollout and recovery
Stage the new version, begin bounded overlap, then retire the old version after fixture sender convergence.
Value of the work
For the engineer: Practice credential lifecycle design, overlap windows, authenticated webhooks, and failure recovery without handling real secrets.
For the team: Review whether an engineer can make rotation auditable and fail closed while preserving availability and replay safety.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.