SSL Error [004C]

[ResistorCat]

Hi!, i'm having an issue with SSL when doing sync tasks in a FreeRTOS task (ESP32CAM). I'm getting:

[E][ssl_client.cpp:37] _handle_error(): [data_to_read():361]: (-76) UNKNOWN ERROR CODE (004C)
[V][ssl_client.cpp:321] stop_ssl_socket(): Cleaning SSL connection.

after some time running tasks. It works normally for a minute and then this happens. The ESP doesn't crash but after this error, the firebase task doesn't work until a reset.

This is my freeRTOS task for firebase (i wrote this based on another question in this discussions):

void task_firebase(void* param) {
    for (;;) {
        app.loop();
        Database.loop();
        Bucket.loop();

        if (app.ready()) {
            // Check for new firmware
            if (check_fota) do_fota();
            // Upload photos
            upload_photos();
            // Update status
           update_status(status);
            // Check commands
            check_commands();
        }
        vTaskDelay(INTERVAL_TASK_FIREBASE / portTICK_PERIOD_MS);  // 10 ms
    }
}

It works fine for a minute, and then the SSL error happens. I can share more code if you need to debug this.

[mobizt]

AS you will see the WiFiClientSecure is not a part of library and defined by user.

The issue is not related to library in anyway. You have to debug your code instead.

[mobizt]

You should try to increase the stack for your FreeRTOS task.

And please make sure the WiFiClientSecure used with library was not shared usage with your other code.

[ResistorCat]

Hi, thank you for your answer. I don't touch the ssl_client nowhere. I just defined it like in the examples. Also, i'm connecting to wifi normally with WiFi.h, but i'm also opening a ESP-NOW connection (could this be a problem?). I just tested removing the firebase tasks from a freeRTOS task and i put all the firebase logic in the main loop(), and i'm printing the available heap and no errors so far. The ssl error still happens, and sometimes i also get [data_to_read():361]: (-80) UNKNOWN ERROR CODE (0050)

[mobizt]

May be WiFi conflicts which you should test your code with internet access before applying to use with library.

[mobizt]

Related issue https://forum.dronebotworkshop.com/esp32-esp8266/using-espnow-and-wifi-at-the-same-time-on-an-esp32/

[ResistorCat]

Thanks! I have done some research and a lot of testing. It doesn't seem to be the ESP-NOW interference. I found that doing too many sync operations crashes the ssl client. When limiting the amount of operations to, i found that ssl client cleans the SSL connection like this:

[340046][V][ssl_client.cpp:369] send_ssl_data(): Writing HTTP request with 1044 bytes...
[340454][V][ssl_client.cpp:321] stop_ssl_socket(): Cleaning SSL connection.
[340467][V][ssl_client.cpp:62] start_ssl_client(): Free internal heap before TLS 139416
[340467][V][ssl_client.cpp:68] start_ssl_client(): Starting socket
[340528][V][ssl_client.cpp:146] start_ssl_client(): Seeding the random number generator
[340529][V][ssl_client.cpp:155] start_ssl_client(): Setting up the SSL/TLS structure...
[340533][D][ssl_client.cpp:176] start_ssl_client(): WARNING: Skipping SSL Verification. INSECURE!
[340541][V][ssl_client.cpp:254] start_ssl_client(): Setting hostname for TLS session...
[340549][V][ssl_client.cpp:269] start_ssl_client(): Performing the SSL/TLS handshake...
[341876][V][ssl_client.cpp:290] start_ssl_client(): Verifying peer X.509 certificate...
[341877][V][ssl_client.cpp:298] start_ssl_client(): Certificate verified.
[341879][V][ssl_client.cpp:313] start_ssl_client(): Free internal heap after TLS 96388
[341887][V][ssl_client.cpp:369] send_ssl_data(): Writing HTTP request with 1044 bytes...
[342298][V][ssl_client.cpp:369] send_ssl_data(): Writing HTTP request with 1044 bytes...

This happens every ~40 seconds and with more operations, the SSL Client doesn't have enough time to refresh de connection before it collapses. I think there is a limit of bytes that can be written every 40 seconds, and maybe i was doing too many requests that it didn't have time to reset and free its internal heap. So, it is working now with less operations per second, I have set up a time interval between different operations with firebase, so it doesn't collapses before it needs to clean. Thanks for all your help, and I hope this can be useful for someone else having this same problem.

[mobizt]

I don't know you have read the library documentation or not.

Running Many Tasks Concurrency Using Different Async Clients (In Different SSL Clients)

It is user problem in memory management.

This is not a something new, if you familiar to the ESP32 WiFiClientSecure usage, you should know how much memory it takes.

[ResistorCat]

I have read that part of the documentation, but it isn't my case (I think), i'm only running 1 ssl_client with WiFiClientSecure. Additionally, al my requests are Sync and not Async, and i dont call any other requests until the last sync request is done (with the same async client). I couldn't find something in the docs that says it's wrong to call sync requests this way. (I'm assuming that when I use sync, the code stops until a response or error exists).

Pd: my code isn't having memory or heap errors, only the ssl error.

[mobizt]

the SSL Client doesn't have enough time to refresh de connection

The problem is your device is out of memory because of opening multiple SSL connection simultaneously as you prefer to use sync function but still opening the server connection in another FreeRTOS task.

When free Heap less than 100k in ESP32, the mbedTLS memory allocation will during TLS handshake and WiFiClientSecure will not be able to connect to the server.

If this happens in ESP8266 as free Heap is less than 7-8 k, your device will crash because of system task fails to feed the watch dog timer.

You will lose some memory used by stack in FreeRTOS tasks, then avoid using it as possible when memory is the constraint of your application.

You do not need to do multi-threading operation for server connection than time scheduling multi-tasking.

[mobizt]

You still don't get what I mean about memory management.

If you do something properly, it should not be a problem.

Do you check or monitor your memory leaks all the time? It is very essential.

[mobizt]

I don't mention that wrong library usage, but you don't manage your code for memory usage well and you don't know why WiFiClientSecure fail, and you still mentioned the library operation causes the faults which is not true.

[mobizt]

Additionally, you never shared your code and let me guess many possibilities and you are summarizing the problem based on your understanding with trial errors which is not the real root cause.

[ResistorCat]

Oh, I'm sorry, I'm not saying that the FirebaseClient library is the problem, I'm just looking to debug the issue. Thank you very much for your help, I had no idea about the heap issue when it's less than 100k on the ESP32. That's probably the cause of the error, as debugging the memory, the available heap is less than 100k (around 80k when the SSL client stops working). Also, I apologize for the misunderstanding, I've only been studying the operation of the ESP32 for a university project for 4 months and I still don't know much, so your contribution is very useful! I'm going to clean up my code and move the logic from a FreeRTOS task to the main loop. Thank you very much!