87 lines
3.6 KiB
Markdown
87 lines
3.6 KiB
Markdown
---
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id: fix/add-code-comments
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name: Add clarifying code comments for correct-but-non-obvious behaviors
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status: completed
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depends_on: [fix/remove-health-and-hardcode-https]
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scope: narrow
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risk: trivial
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impact: component
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level: implementation
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review_findings: [C3, W8, W10, W11, S9]
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---
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## Description
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Several review findings identified behaviors that are correct but need clarifying comments to prevent future "fixes" that would change correct behavior. This task adds documentation comments to these code locations.
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### Comments to Add
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**C3 — X-Forwarded-For replace semantics** (`src/proxy/headers.rs`):
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Add a comment above `headers.insert(HeaderName::from_static("x-forwarded-for"), ip_value)`:
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```rust
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// X-Forwarded-For is SET (not appended) because this proxy is the outermost
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// edge proxy. Any existing X-Forwarded-For from the client is untrusted and
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// must be replaced with the actual client IP from ConnectInfo.
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// See ADR-021 for the edge proxy model rationale.
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```
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**W8 — Server header removal** (`src/proxy/handler.rs`):
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Add a comment above `parts.headers.remove("server")`:
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```rust
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// The upstream Server header is intentionally removed. As a security-focused
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// reverse proxy, we hide upstream server identity as a defense-in-depth measure.
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// The proxy does not add its own Server header either. See W8 in review #002.
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```
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**W10 — Body limit two-layer defense** (`src/proxy/body_limit.rs`):
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Add a comment above the Content-Length check:
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```rust
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// Early rejection: if Content-Length is present and exceeds the limit, reject
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// immediately without reading the body. For requests without Content-Length
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// (chunked, HTTP/2), the Limited body wrapper below enforces the limit during
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// streaming. This is a two-layer defense.
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```
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**W11 — Health check port conflict conservatism** (`src/config/validation.rs`):
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Add a comment above the health check port conflict check:
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```rust
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// Health check always binds to 127.0.0.1 (hardcoded in src/health.rs), so this
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// conflict check is conservative — it warns even when the health check port
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// wouldn't actually conflict (e.g., health check on 127.0.0.1:80 vs listener
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// on 203.0.113.10:80). This is acceptable for Phase 1.
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```
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**S9 — Rate limit bypass when no IP** (`src/rate_limit/mod.rs`):
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Add a comment above the `return next.run(req).await` in the `None` branch:
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```rust
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// If no client IP can be identified, the request passes through without rate
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// limiting. In practice, ConnectInfo is always set by the server's
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// ConnectInfoService, so this branch is unreachable. If the proxy were ever
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// deployed without ConnectInfo propagation, rate limiting would silently become
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// a no-op. Consider adding a warning log or returning 429 in a future phase.
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```
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## Acceptance Criteria
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- [ ] All five comments are added at the specified locations
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- [ ] Comments reference the relevant ADRs or review findings where applicable
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- [ ] Code behavior is unchanged (comments only)
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- [ ] `cargo clippy` passes with no warnings
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## References
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- docs/reviews/002-implementation-review.md — C3, W8, W10, W11, S9 findings
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- docs/architecture/decisions/021-x-forwarded-for-edge-proxy.md — ADR-021
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- src/proxy/headers.rs — X-Forwarded-For insert
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- src/proxy/handler.rs — Server header removal
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- src/proxy/body_limit.rs — Content-Length check
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- src/config/validation.rs — Health check port conflict
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- src/rate_limit/mod.rs — No IP fallback
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## Notes
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> This task depends on fix/remove-health-and-hardcode-https because the X-Forwarded-Proto comment (W14) is being addressed in that task. The remaining comments here are independent.
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## Summary
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> To be filled on completion |