Starting from few weeks ago, all my Mongoose OS based IoT devices fail connecting to the local Mosquitto MQTT broker. Everything worked fine since a couple of weeks ago.

This is my WEMOS D1 Mini board yml configuration:

config_schema: 
  - ["mqtt.enable", true]
  - ["mqtt.user", "<my_username>"]
  - ["mqtt.pass", "<my_password>"]
  - ["mqtt.server", "<my_loacal_IP_address>:8883"]
  - ["mqtt.ssl_ca_cert", "ca.pem"]

This is the error log of my WEMOS D1 Mini board:

[Sep 15 08:54:05.996] mgos_mqtt_conn.c:471    MQTT0 connecting to 192.168.1.254:8883
[Sep 15 08:54:06.020] mongoose.c:4912         0x3fff1574 is a fatal alert message (msg 40)
[Sep 15 08:54:06.025] mongoose.c:4912         0x3fff1574 mbedtls_ssl_handle_message_type() returned -30592 (-0x7780)
[Sep 15 08:54:06.034] mongoose.c:4912         0x3fff1574 mbedtls_ssl_read_record() returned -30592 (-0x7780)
[Sep 15 08:54:06.040] mongoose.c:5088         0x3fff1574 mbedTLS error: -0x7780
[Sep 15 08:54:06.050] mgos_mqtt_conn.c:229    MQTT0 TCP connect error (-3)
[Sep 15 08:54:06.050] mgos_mqtt_conn.c:256    MQTT0 Disconnect

This is the error log of my local Mosquitto MQTT broker:

1631689879: New connection from 192.168.1.15 on port 8883.
1631689879: OpenSSL Error[0]: error:1417A0C1:SSL routines:tls_post_process_client_hello:no shared cipher
1631689879: Socket error on client <unknown>, disconnecting.

When I try to build firmware, it dies, saying this library contains neither sources nor prebuilt binaries.

Error: /private/tmp/mos-20191105-57219-1rk8su4/mos-adcad3f2ca90789fc5426dc8c6302383effaa415/src/cesanta.com/go/src/github.com/mongoose-os/mos/mos/manifest_parser/manifest_parser.go:353: neither sources nor prebuilt binary exists for the lib "mbedtls" (or, if a library doesn't have any code by design, its mos.yml shouldn't contain "sources"). Fetch error was: [failed to download libmbedtls-eps8266.a: mongoose-os-libs/mbedtls: no asset libmbedtls-eps8266.a found in release 2.16.0: file does not exist]
/private/tmp/mos-20191105-57219-1rk8su4/mos-adcad3f2ca90789fc5426dc8c6302383effaa415/src/cesanta.com/go/src/github.com/mongoose-os/mos/mos/build_local.go:142:
/private/tmp/mos-20191105-57219-1rk8su4/mos-adcad3f2ca90789fc5426dc8c6302383effaa415/src/cesanta.com/go/src/github.com/mongoose-os/mos/mos/build.go:220:
/private/tmp/mos-20191105-57219-1rk8su4/mos-adcad3f2ca90789fc5426dc8c6302383effaa415/src/cesanta.com/go/src/github.com/mongoose-os/mos/mos/build.go:163:
/private/tmp/mos-20191105-57219-1rk8su4/mos-adcad3f2ca90789fc5426dc8c6302383effaa415/src/cesanta.com/go/src/github.com/mongoose-os/mos/mos/main.go:196: build failed

It would be very helpful to be able to enable mbedtls_platform_set_calloc_free by setting CONFIG_MBEDTLS_PLATFORM_MEMORY=y in build vars, to align with this commit of the main mbedtls library in ESP-IDF.

espressif/esp-idf@d7a17ac

This would allow us to specify that mbedtls should use SPIRAM rather than internal RAM, as described in this post:
espressif/esp-idf#2184

mbedtls has this feature. I guess it would be trivial (I might be wrong) to port to this.

I'm trying to use mbedtls with mongoose OS compiled with different cflags for the mbedtls library.

However, the library sources ("mbedtls/library") and the "src" directory referenced in the mos.yml file are not present in this repo. I tried copying the "library" directory from ARMmbed/mbedtls version 2.16.0, but it seems like there are changes to the header files which makes the sources incompatible with the headers in this repo.

Can you provide instructions on how to compile this library from sources instead of using the pre-compiled version?