79 lines
3.7 KiB
Markdown
79 lines
3.7 KiB
Markdown
---
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id: review-002-ws13-idle-progress
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name: Idle deadline off demux progress + slow-legitimate-stream decision (WS-13)
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status: completed
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depends_on: []
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scope: moderate
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risk: high
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impact: component
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level: implementation
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tags: [websocket, review-002]
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---
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## Description
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Review 002 WS-13 [major]. The WS-01 remediation's idle timer
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(`byte_adapter.rs:229-244`) wraps only the next-message await, so it
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fails in both directions:
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1. **The attack it exists for defeats it.** WS-01's dribble (declare a
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16 MiB chunk, deliver one byte per WS message per minute) keeps
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arriving messages → the deadline resets on every dribble → the demux
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still parks forever with the partial chunk. The doc (:117) claims
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"a peer that drips bytes cannot park the single demux loop longer
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than this without traffic" — under the actual attack the peer
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supplies traffic forever.
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2. **Legitimate slowness is killed.** A >60 s-silent-but-alive session
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(long handler compute, quiet subscription) is disconnected with
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1001 mid-flight — no ping/pong keepalive exists, and chunk progress
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does not reset the timer.
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The existing test (`idle_read_timeout_resets_on_traffic`) enshrines
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reset-on-message as correct — it codifies the gap.
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## Acceptance Criteria
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- [ ] Decide + implement the progress semantics: the deadline resets
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on **demux progress** (bytes actually forwarded into `read_tx`),
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not message arrival — a peer that dribbles a chunk forever hits
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the deadline; a peer delivering complete chunks (even slowly
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per-message but productively) keeps the connection
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- [ ] Decide + document the legitimate-silence stance (choose one and
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record it in the module doc + http-server/websocket.md):
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(a) add WS ping/pong keepalive so app-silence ≠ transport-silence,
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or (b) document that 60 s of *no progress* is an intentional
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eviction line even for silent subscriptions
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- [ ] Acceptance test 1: chunk header `[ch][len=N]` dribbled in small
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messages with per-message gaps < timeout → connection closed
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(progress deadline fires)
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- [ ] Acceptance test 2: scaled-down silent-but-alive session with a
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pending response is NOT disconnected when the knob's spirit says
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it should survive (e.g. messages flowing that make progress)
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- [ ] The WS-01 knob surface (`with_ws_idle_timeout`) is unchanged;
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the semantics change is doc'd against it
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- [ ] `cargo test`, `cargo clippy --all-targets -- -D warnings`,
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`cargo fmt --check` pass (tungstenite-path unit tests + one axum
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integration mirror)
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## References
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- docs/reviews/002-post-remediation-review.md (Part B', WS-13; Part G', COV-11b — the knob is currently untested on the axum path too)
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- src/websocket/byte_adapter.rs:117 (doc claim), :229-253 (the timer), :782-1206 (tests)
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- tasks/websocket/review-001-ws-session-limits.md (the WS-01 knob work)
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- docs/architecture/websocket.md
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## Notes
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Highest-risk task in the batch (touching the shared pump's read loop —
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the same loop the cap logic lives in). Slice suggestion: (1) progress
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tracking + tests on the tungstenite path, (2) doc/keepalive decision,
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(3) axum integration mirror. Coordinate with
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review-002-con18b-ws-polish (same file) — sequence, don't parallelize.
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If (a)-keepalive is chosen, note it interacts with FWD-15's
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server-side keep-alives on the *HTTP* SSE path — different layers, but
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document both in the same doc pass.
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## Summary
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Idle deadline resets on completed inbound chunks (InboundChunkProgress observer), not message arrival; decision (b) documented - no WS keepalive, 60s no-progress eviction is intentional (pong is attacker-equivalent traffic). Tungstenite unit + axum integration tests; knob surface unchanged.
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