ESP8266 AT MQTT SSL Certificates not working

[bluscape]

I've asked the same question on stackoverflow: https://stackoverflow.com/questions/764 ... 1_76433285

I'm using the ESP8266 (WROOM-02D) for MQTT over WIFI. I'm using AT commands for MQTT. I'm currently using ESP8266-IDF-AT_V2.2.1.0 firmware on the WROOM-02D. My broker has been configured to use both client and server certificates for authentication.

I flashed my certifactes to the module at the following addresses as per the partition table:

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0xF8000 - client_cert.bin
0xFA000 - client_key.bin
0xFC000 - client_ca.bin
0x106000 - mqtt_key.bin
0x104000 - mqtt_cert.bin
0x108000 - mqtt_ca.bin

I configure the module with the following AT commands:

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AT+CWMODE=1 // Station mode
AT+CWJAP="SSID","Password" // Connect to AP
AT+CIPMUX=0 // Single connection
AT+CIPSNTPCFG=1,8,"ntp1.aliyun.com" // Configure and enable SNTP
AT+CIPSNTPTIME? // Query the SNTP time
AT+CIPSSLCCONF=3,0,0 // Set the SSL clients (mutual authentication)
AT+MQTTUSERCFG=0,5,"ClientID","","",0,0,"" // MQTT user configuration
AT+MQTTCONNCFG=0,30,0,"topic","message",0,0 // MQTT connection configuration
AT+MQTTCONN=0,"BrokerAddress",BrokerPort,0 // Connect to the MQTT broker

THE PROBLEM

Whenever I execute the command

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AT+MQTTCONN

, the module will reset. The module will reset even if use the default provided certicates. I found that the module will reset whenever MQTT scheme uses TLS (with or without certificates).

When I set the scheme to 0 (TCP and no TLS), there is no issue.

I've tried several things and even different firmwares but cannot get it to work.

When looking at the AT command manual, the MQTT user configuration has a "path" parameter.

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AT+MQTTUSERCFG=<LinkID>,<scheme>,<"client_id">,<"username">,<"password">,<cert_key_ID>,<CA_ID>,<"path">

I'm not sure if this could be the problem, but I cannot find any documentation on specifying the path.

[esp-at]

hello, you are right. ESP8266-AT does not support MQTT over TLS due to memory limit.

And the doc described here: https://docs.espressif.com/projects/esp ... parameters, please know.

[banjoluck]

Call me crazy if you like.

Wouldn't it be a low-cost feature to simply report an error instead of crashing?

[esp-at]

Sorry for the inconvenience. For a well-designed firmware, it shouldn't crash anyhow. However, memory issues are a global problem, and if any component does not handle memory allocation properly, it can lead to crash situations. As the ESP8266 SDK will not undergo significant updates, it is unlikely that the current behavior will be changed.

If you wish to use MQTT over TLS, we recommend considering ESP32-C3/ESP32-C2/ESP32 chips as a priority.

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