Self-review pass on the security fix uncovered five issues, all fixed
here:
1. will_reject scheme handling. Engineio compares full {scheme}://{host}
strings, not just hostnames. A TLS-terminating proxy can leave the
backend seeing http while the browser's Origin is https — engineio
rejects, but the original predictor said "allow" → no helpful log
line. Added request_scheme + forwarded_proto params, build full
candidate strings to match engineio.
2. EITHER-forwarded-header rule. Engineio adds the forwarded candidate
when EITHER X-Forwarded-Proto OR X-Forwarded-Host is present (it
falls back to HTTP_HOST for the missing one). The original predictor
only added it when forwarded_host was set — false negative for
misconfigs sending only X-Forwarded-Proto. Now mirrors engineio.
3. will_reject incorrectly rejected missing-Origin requests. Engineio
(server.py:207: `if origin: validate`) skips CORS validation when
no Origin header is sent — non-browser clients (curl etc.) are
intentionally permitted. The original code rejected them. Test was
asserting the wrong behavior. Both fixed.
4. RejectionLogger had unbounded dedup set growth. A hostile actor
opening connections from many distinct fake origins would fill
memory unboundedly. Capped at 100 unique origins (configurable);
when cap hit, one overflow notice is emitted and further rejections
are silently dropped until restart.
5. Lock pattern: the overflow log path called logger.warning() while
holding the dedup lock, inconsistent with the normal path. Fixed
to pick the message under the lock and log after release. Critical
section is now minimal and uniform.
Plus polish:
- Stale module docstring fixed (said "empty list" instead of "None").
- settings.js validates each cors_origins line against a URL regex on
save; toasts a one-shot warning if entries are malformed (resolver
silently filters them, but user gets feedback now).
- web_server.py wiring passes request.scheme + X-Forwarded-Proto so
the predictor has full proxy info.
Tests:
- 51 unit tests in tests/test_socketio_cors.py (was 45). New cases:
* scheme comparison (5 cases including TLS-terminating proxies)
* forwarded_proto-alone misconfig
* missing-origin matches engineio (was asserting wrong behavior)
* dedup cap with overflow + reset
* default cap is reasonable (uses public DEFAULT_DEDUP_CAP constant)
Engineio behavior independently verified by reading engineio/server.py
and engineio/base_server.py source. Predictor mirrors both files.
604 tests pass.
Closes#366 (reported by JohnBaumb).
Socket.IO was initialized with `cors_allowed_origins='*'`, accepting
WebSocket connections from any origin. A malicious site could open a
WS to a user's local SoulSync instance and exfiltrate live progress /
toast / activity events.
This commit:
- Defaults to engineio's same-origin behavior (`cors_allowed_origins=None`),
which automatically honors X-Forwarded-Host so reverse proxies that
send that header (Caddy / Traefik by default, properly-configured
Nginx) work transparently.
- Adds a `security.cors_origins` config setting + Settings → Security
textarea where users behind unusual proxies / Electron wrappers /
cross-origin integrations can whitelist their origin. Accepts comma
or newline separated values; `*` on its own line opts back into the
legacy wildcard with a startup-warning log.
- Logs a clear warning the first time engineio rejects each unique
origin, naming the rejected Origin and request Host and pointing
users to the settings field. Without this, engineio silently 403s
the upgrade and the user just sees a half-broken UI with no clue
why. Threadsafe dedup so a hostile origin can't spam logs.
Logic lives in `core/socketio_cors.py` (resolver, rejection
predictor, dedup logger class, startup-status emitter) — pure
functions, no Flask dependency. `web_server.py` adds 23 lines of
wiring and imports.
Important catch during review: my first pass used `cors_allowed_origins=[]`
as the "secure default." Reading engineio's source revealed `[]` actually
means "DISABLE CORS HANDLING" (engineio/server.py:202: `if cors_allowed_origins != []:`)
— identical security to `'*'`. Fixed to use `None` (engineio's actual
same-origin sentinel) and pinned with a regression test that asserts
the resolver never returns `[]` for any input shape.
Tests:
- tests/test_socketio_cors.py — 45 unit tests covering 19 resolver shape
cases (None, empty, whitespace, comma, newline, garbage types, lists),
the `[]`-must-never-be-returned security regression, 12 rejection
prediction cases, X-Forwarded-Host handling, dedup logger behavior,
threadsafe race (8 threads × 50 hammers → exactly 1 warning), and
startup-status emitter outputs.
Frontend:
- Settings → Security gains an "Allowed WebSocket Origins" textarea
with help text explaining same-origin default + when to add a domain
+ the `*` opt-out.
- helper.js — new '2.4.1' WHATS_NEW block (hidden until version bump)
with a chill-voice entry describing the change.
Conftest.py left at `'*'` — test environment, no security concern.
598 tests pass.
Broque Thomas