fix(ws): add Origin allowlist to browser WebSocket upgrade (CSWSH hardening)
Closes Draco-Lunaris/Linux-Patch-Manager#10 The browser WebSocket endpoint at GET /api/v1/ws/jobs previously authenticated solely via a single-use, 60-second ticket passed as a query parameter. A leaked ticket (browser history, Referer, proxy logs, support bundles) could be redeemed from any origin, enabling Cross-Site WebSocket Hijacking (CSWSH). This change adds a second gate: the Origin header must match an explicit allowlist. The check runs BEFORE ticket validation so that rejected cross-origin probes do not consume the legitimate users ticket. Changes: - pm-core: new security.allowed_origins config field; default derived from sso_callback_url; startup warning if both are unparseable - pm-web: ws_handler extracts HeaderMap and calls check_origin first; returns 403 on missing/malformed/disallowed origins - config: documented allowed_origins key in config.example.toml - docs: security-review.md section 1.4 (WebSocket Origin Allowlist) - tests: 40 unit tests (7 pm-core, 33 pm-web)
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Draco Lunaris
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tasks/ws-origin-check-spec.md
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tasks/ws-origin-check-spec.md
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# WS Origin Allowlist — Specification
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**Issue:** [#10](https://github.com/Draco-Lunaris/Linux-Patch-Manager/issues/10)
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**Component:** `crates/pm-web/src/routes/ws.rs`
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**Spec version:** 0.1.0 (draft)
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**Status:** Awaiting Kelly sign-off
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---
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## 1. Goal
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Harden the browser-facing WebSocket upgrade endpoint (`GET /api/v1/ws/jobs`) against
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Cross-Site WebSocket Hijacking (CSWSH) by validating the `Origin` header against a
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configured allowlist. The existing single-use, 60-second ticket mechanism is retained
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as the first credential factor; the Origin check is the second factor.
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## 2. Non-Goals
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- Replacing or weakening the ticket mechanism.
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- Binding the ticket to a specific WebSocket connection at issuance time (separate,
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larger change).
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- Origin/CORS checks on the JWT-authenticated ticket-issuance endpoint
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(`POST /api/v1/ws/ticket`) — it is already protected by JWT + RBAC middleware and is
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not a browser-only entry point.
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- Changes to `pm-worker/ws_relay.rs` — that module is an outbound mTLS WS *client* to
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agents, not a server, and is not reachable from a browser.
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## 3. Design
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### 3.1 Handler change (`crates/pm-web/src/routes/ws.rs`)
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The `ws_handler` function (lines 96–137) gains a new `HeaderMap` extractor and
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performs an Origin allowlist check **before** ticket validation.
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Order of operations in the new handler:
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1. Extract `HeaderMap` (new).
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2. Read `Origin` header. If absent → reject `403 forbidden_origin` (`"Origin header
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required"`).
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3. Normalize and compare against the configured allowlist. If not matched → reject
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`403 forbidden_origin` (`"Origin not allowed"`).
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4. Existing ticket validation (lines 101–127) runs unchanged.
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5. Existing upgrade (line 136) runs unchanged.
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Rationale for Origin-first ordering: a CSWSH probe from a malicious page will not
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have a valid ticket. If we validated the ticket first and then checked Origin, an
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attacker who has obtained a leaked ticket (from logs, `Referer`, history, support
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bundle) could mount a denial-of-service against the legitimate user by burning their
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tickets with `403` responses. Origin-first means rejected cross-origin attempts do
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not consume the user's ticket.
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### 3.2 Origin parsing and comparison
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- Read the raw `Origin` header value as a string.
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- Strip any trailing `/`.
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- Use a hand-rolled parser (no new dependency) to extract `scheme`, `host`, and
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optional `port`:
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- `scheme` must be `http` or `https` (lowercased).
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- `host` must be non-empty and contain no whitespace.
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- `port`, if present, must parse as `u16`.
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- Apply default-port normalization: `https` implies port `443`; `http` implies port
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`80`. If the explicit port equals the default for the scheme, drop it from the
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comparison. This matches browser behavior (browsers do not include default ports
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in `Origin`).
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- Case-insensitive host comparison; case-sensitive scheme and port.
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- Match each configured allowlist entry against the parsed Origin. **Exact match
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only** — no subdomain wildcards, no regex, no path.
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- If the `Origin` header is malformed (does not parse) → reject
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`403 forbidden_origin` (`"Malformed Origin header"`).
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### 3.3 Config schema (`crates/pm-core/src/config.rs`)
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Add a new field to `SecurityConfig`:
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```rust
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/// Allowlist of browser `Origin` values permitted to open the
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/// `/api/v1/ws/jobs` WebSocket. Entries are exact `scheme://host[:port]`
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/// strings. If empty, the server derives the default from `sso_callback_url`.
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#[serde(default = "default_allowed_origins")]
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pub allowed_origins: Vec<String>,
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```
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Default value (`default_allowed_origins`): a single-element vector containing the
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`scheme://host[:port]` form of `sso_callback_url` parsed at config-load time. This
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keeps the default config secure out of the box — a fresh install will only accept
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WS upgrades from the same origin the SSO callback redirects to.
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If `sso_callback_url` cannot be parsed (e.g., a custom dev value), fall back to
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`vec![]` and emit a `tracing::warn!` at startup. An empty allowlist with no
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parseable default would make the WS endpoint reject all upgrades; this is the safe
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direction (fail-closed), but the warning makes it loud.
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Add a corresponding `ConfigError` if `allowed_origins` is manually set to an empty
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vector and `sso_callback_url` is also unparseable, since that combination produces a
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non-functional WS endpoint. The user must explicitly opt in to "no origins allowed"
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by providing a list.
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### 3.4 Logging
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- On allowed upgrade: existing `tracing::info!` continues (lines 129–133), augmented
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with `origin = %origin_str` for audit context.
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- On rejected upgrade: new `tracing::warn!` with `origin = %origin_str` and
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`reason = %reason`. **Never log the ticket value**.
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### 3.5 Response shape
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Reuse the existing `err` helper (lines 48–58):
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```json
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{ "error": { "code": "forbidden_origin", "message": "…" } }
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```
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Status: `403 Forbidden` for all Origin rejections. Do not differentiate between
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"missing", "malformed", and "not in allowlist" in the response — they all map to the
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same code, and the specific reason is logged server-side only.
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## 4. Acceptance Criteria
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- [ ] A WS upgrade request with a missing `Origin` header is rejected with `403`
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and code `forbidden_origin`. The ticket is **not** consumed.
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- [ ] A WS upgrade request with a malformed `Origin` header is rejected with `403`
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and code `forbidden_origin`. The ticket is **not** consumed.
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- [ ] A WS upgrade request with an `Origin` not in the allowlist is rejected with
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`403` and code `forbidden_origin`. The ticket is **not** consumed.
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- [ ] A WS upgrade request with an allowlisted `Origin` and a valid, unconsumed
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ticket succeeds (101 Switching Protocols / upgrade accepted) and the ticket is
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consumed atomically (existing behavior preserved).
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- [ ] A WS upgrade request with an allowlisted `Origin` and an invalid/expired/
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already-used ticket is rejected with the existing `401 invalid_ticket` /
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`401 ticket_expired` (existing behavior preserved).
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- [ ] The allowlist is configurable via `security.allowed_origins` in
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`config/config.example.toml` and is documented in that file.
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- [ ] When `allowed_origins` is not set, the default is derived from
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`sso_callback_url` and the service starts cleanly.
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- [ ] `cargo check` and `cargo clippy --all-targets` pass.
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- [ ] `cargo test -p pm-web` passes with the new integration tests added.
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- [ ] `docs/security-review.md` documents the new control with an evidence row
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pointing to `crates/pm-web/src/routes/ws.rs`.
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## 5. Test Plan
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Unit tests in `crates/pm-web/src/routes/ws.rs` (cfg(test) module) — 33 tests
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covering the security-critical logic. The end-to-end wiring (HeaderMap
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extractor, axum handler, response shape) is verified by `cargo check`,
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`cargo clippy --all-targets`, and the manual `scripts/integration-test.sh`
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end-to-end check.
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**Why unit tests instead of `tests/ws_origin.rs` integration tests:** the
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handler is wired to `State<AppState>`, and `AppState` contains a
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`sqlx::PgPool` and a `pm_ca::CertAuthority` that cannot be cheaply
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constructed in a test (the CA requires a real Postgres connection and
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on-disk key material, both unavailable in `cargo test`). Refactoring
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`ws_handler` to take a smaller state struct is out of scope for this
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hardening change.
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### 5.1 pm-core unit tests (`crates/pm-core/src/config.rs`, 7 tests)
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`derive_allowed_origins` — the sso_callback_url → allowlist derivation:
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1. `derive_strips_default_https_port` — `https://x:443/...` → `https://x`
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2. `derive_keeps_non_default_port` — `https://x:8443/...` → `https://x:8443`
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3. `derive_strips_default_http_port` — `http://x:80/x` → `http://x`
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4. `derive_handles_trailing_slash` — `https://x/` → `https://x`
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5. `derive_handles_no_path` — `https://x` → `https://x`
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6. `derive_returns_empty_for_garbage` — rejects "not a url", "", "ftp://x"
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7. `derive_lowercases_scheme` — `HTTPS://...` → `https://...`
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### 5.2 pm-web unit tests (`crates/pm-web/src/routes/ws.rs`, 33 tests)
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`parse_origin_header` (14 tests): basic, with-port, scheme/host lowercasing,
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path/query/fragment ignored, trailing-slash stripped, empty/whitespace
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rejected, unsupported schemes rejected, empty host rejected, host with
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whitespace rejected, malformed port rejected, IPv6 literal rejected, no
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scheme separator rejected.
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`Origin::canonical` (3 tests): default-port normalization in both directions
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(http:80, https:443), non-default port kept.
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`is_origin_allowed` (11 tests): exact match, default-port normalization in
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both directions, case-insensitive host, different host rejected, different
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scheme rejected, different port rejected, empty allowlist rejected,
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unparseable allowlist entry rejected, multi-entry allowlist.
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`check_origin` (7 tests): missing header, malformed header, disallowed
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origin, empty allowlist, allowed origin, default-port normalization allowed,
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case-insensitive host allowed. This function returns the `(StatusCode, Json)`
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error tuple used by the handler, so these tests cover the response shape.
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## 6. Risk Analysis
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- **Risk: a config that breaks the WS endpoint in production.** Mitigation: default
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is derived from `sso_callback_url` (already required for SSO to function), and
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startup logs a warning if the allowlist ends up empty.
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- **Risk: legitimate cross-origin frontend (e.g., SPA on `app.foo.com` talking to
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API on `api.foo.com`).** Out of scope for this fix — the WS endpoint is on the
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same origin as the SPA. If a future deployment splits them, the operator adds
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the API origin to `allowed_origins`. Documented in `config/config.example.toml`.
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- **Risk: a non-browser caller (CLI, integration test) cannot connect.** Such
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callers should use the REST API for state mutations; the WS is documented as the
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browser job-stream channel. If a non-browser WS client is needed, document it in
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`docs/REST_API.md` and tell the operator to add its origin.
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- **Risk: false sense of security.** The Origin check is defense-in-depth, not a
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replacement for the ticket. Documented as such in the security review update.
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## 7. Files Touched
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- `crates/pm-web/src/routes/ws.rs` — handler change.
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- `crates/pm-core/src/config.rs` — new field + default.
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- `config/config.example.toml` — new field documented.
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- `crates/pm-web/tests/ws_origin.rs` — new integration tests (and harness).
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- `docs/security-review.md` — control documentation row.
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- `tasks/todo.md` — plan section (added by the orchestrator).
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## 8. Out of Scope (Future Work)
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- Bind ticket issuance to the WS upgrade in a single round-trip (eliminates
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query-string ticket leakage from logs/history).
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- Per-message MAC on WS frames (defense against in-process tampering).
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- Rate limiting on the WS endpoint itself.
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