I am attempting to establish an MQTT connection with mutual TLS authentication to a AWS IoT Endpoint.
The command I use is AT+S.MQTTCONN=#####.iot.eu-west-1.amazonaws.com,443,,2,,,,,,,, (I only paste the hostname partially for security reasons).
There seems to be some issue validating the server-side certificate, since we always receive the following error:
According to UM2114, the error means Parsing the signature failed, but I fail to understand which certificate (client, server or ca) is failing.
I have already added the AWS IoT root certificate, client certificate and client private key into the filesystem, according to the convention specified in AN4963 (tls.cert, tls.key and <auth-id>.ca files).
It may be worth mentioning that even if no certificates are loaded, the same error is still shown; this leads me to believe the failure should occur when parsing the server certificate.
Is the problem caused by my wrong usage? Or is it a failure of the module?
Attached I send the certificate chain the endpoint sends and a screenshot with the result of AT+S.STS, hoping they may be useful.