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.
Broque Thomas