Normalize forwarded headers without accepting client spoofing
A client-provided forwarded host changes generated callback URLs.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Header security
Estimated field mix
- Security70%
- Networking30%
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 reporting API sits behind a reverse proxy. Clients see intermittent disconnects and incorrect origins after changes to keep-alive and forwarding headers.
Setup prerequisites
- Create two loopback HTTP services and a local proxy with synthetic requests; no public scanning or external traffic.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Discard untrusted incoming forwarding fields.
- Set canonical forwarding metadata at the trusted boundary.
- Reject malformed or conflicting host values.
Implementation constraints
- Use an explicit allowed-origin list.
Verification to include
- Generate a callback for the allowed origin.
- Inject a spoofed forwarded host and verify rejection.
Deliverables
- Forwarding-header guard.
Rollout and recovery
Enable alongside the reviewed proxy chain; retain safe fixed-origin fallback.
Value of the work
For the engineer: Practice HTTP intermediaries, connection lifetimes, and network failure isolation.
For the team: Provide a proxy contract that preserves request identity and releases resources predictably.
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.