The precompiled IDF 4.4 WebSocket transport (libtcp_transport.a) has an
off-by-one in ws_connect(): when a wss:// endpoint answers the upgrade
request with >=1024 bytes of HTTP response before the blank-line
terminator (typical of a down broker behind a proxy serving a large
error page), it writes a NUL one byte past the 1024-byte ws->buffer.
Heap poisoning catches the clobbered tail canary (0xbaad5678 ->
0xbaad5600) only when the block is freed in ws_destroy() during
esp_mqtt_client_destroy() - i.e. MQTTBridge::end() - so a single down
broker made every deferred 'ota update' panic and reboot at teardown,
before the download started. Decoded from a Heltec V3 crash backtrace
on v1.16.0.11; line numbers match ESP-IDF release/v4.4 exactly.
The transport code ships precompiled, so patch at link time instead:
[esp32_base] wraps esp_transport_ws_init and the wrapper swaps the
fresh buffer for a (WS_BUFFER_SIZE + 1)-byte allocation, making the
out-of-bounds index land on owned memory. The oversized handshake then
fails cleanly instead of corrupting the heap. Pass-through on IDF 5.x,
where upstream already fixed it; delete with the Arduino core 3.x move.
Verified: wrap resolves from ESP32WsTransportFix.cpp.o in the observer
firmware.map; observer, room-server observer and plain repeater ESP32
targets build. RAK_4631_repeater failure is pre-existing (reproduced
on the merge base without these changes).
mikecarper