feat(w1 slice-2b/O1): INERT CF Live Output RTMP restream + SSRF-at-connect (wre#287)

[yakimoto]

Summary

• Concrete CfStreamEgressClient adapter (egress-cf-stream-live-output-client.ts): calls CF's real POST /accounts/{accountId}/stream/live_inputs/{liveInputId}/outputs with {url, streamKey}, derived live-input uid from the bridged cfstream:{uid} sessionId, fail-closed typed errors (no throw into media path).
• Closes the "SSRF only at create, not connect" gap: assertDestinationSafeAtConnect (egress-arm.ts) re-runs validateDestinationUrl immediately before any outbound provision/dial.
• New armExternalRtmpRestream arm path: resolveDestinationForArm -> refuse (404) if null -> SSRF-at-connect -> refuse (403) if unsafe -> provisionOutput.
• INERT: requires BOTH EGRESS_ROUTER_ENABLED and EGRESS_DEST_MGMT_ENABLED armed (default OFF). No call site wires it in yet — prod byte-identical.
• Part of Zoom Live Media epic wave-zoom#46. Consumes resolveDestinationForArm from wre#289 (feat(w1): external egress destination mgmt + SSRF guard + key encryption (O3, #17, #18) #316/feat(w1 slice-1b): INERT emitEgressLegUsage egress-leg metering #318, already on main).

Test plan

• npx tsc --noEmit — 0 errors
• npx vitest run — 1445/1445 passing (full suite, no regressions)
• New tests prove: correct CF request shape (mocked fetch), non-2xx CF reply -> typed error, SSRF-at-connect rejects a rebound destination (public IP at create, link-local at connect) with NO provision call, absent/foreign-org destId -> refused with NO provision call, flags-off -> INERT

🤖 Generated with Claude Code

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Note

Medium Risk
Touches egress connect-time SSRF and outbound CF provisioning for user-supplied RTMP URLs, but stays inert without both flags and has no production call site yet.

Overview
Adds inert-by-default wiring to simulcast an already-ingested Cloudflare Stream live input to a customer RTMP destination (YouTube/Twitch/custom), gated on both EGRESS_ROUTER_ENABLED and EGRESS_DEST_MGMT_ENABLED. Nothing in prod calls it yet.

egress-arm.ts introduces assertDestinationSafeAtConnect (re-runs validateDestinationUrl right before dial/provision to close DNS-rebind after create-time checks) and armExternalRtmpRestream: resolve org-scoped destination → SSRF-at-connect → typed provisioned / refused outcomes (404/403/CF errors), no throws into the media path.

egress-cf-stream-live-output-client.ts is the concrete CfStreamEgressClient that POSTs CF Stream live outputs: derives live-input id from cfstream:{32-hex} session ids, splits combined RTMP URLs into CF’s {url, streamKey} body, fail-closed on bad input or API errors.

Vitest covers DNS-rebind refusal, flag-off inert behavior, org/destination failures, and mocked CF request shape.

^{Reviewed by Cursor Bugbot for commit 94e1aae. Configure here.}

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Summary by cubic

Adds external RTMP restreaming via Cloudflare Stream Live Output and closes the DNS-rebind gap by rechecking destinations at connect time, centralized at the CF-output chokepoint. Inert behind EGRESS_ROUTER_ENABLED and EGRESS_DEST_MGMT_ENABLED. Addresses wre#287 and sec-review #320.

• New Features

  • CfStreamEgressLiveOutputClient: calls Cloudflare POST /accounts/{accountId}/stream/live_inputs/{liveInputId}/outputs, derives liveInputId from cfstream:{uid}, splits combined rtmp://.../app/streamKey, returns typed errors on non-2xx.
  • assertDestinationSafeAtConnect: re-runs validateDestinationUrl right before provisioning to block DNS-rebinds.
  • armExternalRtmpRestream: resolves the org-scoped destination, rechecks SSRF, then provisions via the client; typed outcomes; INERT unless both flags are on.

• Bug Fixes

  • Centralized SSRF-at-connect in CfStreamEgressLiveOutputClient.provisionOutput so both passthrough and O1 arm paths cannot provision if the resolved IP is unsafe.
  • Guarded destination kind in armExternalRtmpRestream (non-rtmp refused with 400).
  • Wrapped resolveDestinationForArm in try/catch; failures now refuse with 500 (fail-closed), not throws.

^{Written for commit 06c4207. Summary will update on new commits.}

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📥 Commits

Reviewing files that changed from the base of the PR and between 7386cd5 and 06c4207.

📒 Files selected for processing (5)

• src/egress-arm.ts
• src/egress-cf-stream-live-output-client.ts
• test/egress-arm-o1-restream.test.ts
• test/egress-cf-stream-live-output-client.test.ts
• test/egress-cf-stream-passthrough.test.ts

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