Connect to MQTT Broker using cacert,clientcert and key using MQTTNet

I am using MQTTNet with .Net 6 . My MQTT Broker provides 3 certificates as follows

• CA Cert
• Client Cert
• Client Key

These certificates are valid and work if i use them with a software like MQTTExplorer.

Now I am trying to use MqttNet (latest version) to connect to the broker. I have read the documentation and accordingly tried by converting clientCert and Key to pfx file using following command.

openssl pkcs12 -export -out certificate.pfx -inkey clientkey.pem -in clientCert.crt

Now I have two certificates

• certificate.pfx (with password)
• ca cert

I am trying to use MQTTNet as follows in console app:

var factory = new MqttFactory();
var mqttClient = factory.CreateMqttClient();

var caCert = X509Certificate.CreateFromCertFile(@"certificates\cacert.cer");

var clientCert = new X509Certificate2(@"certificates\mycertificate.pfx", "mypassword");

var options = new MqttClientOptionsBuilder()
            .WithClientId(clientId)
            .WithTcpServer(mqttUri, mqttPort)
            .WithTls(new MqttClientOptionsBuilderTlsParameters
            {
                UseTls = true,
                SslProtocol = System.Security.Authentication.SslProtocols.Tls12,
                Certificates = new List<X509Certificate>()
                {
                    caCert,clientCert
                }
            }).Build();

await mqttClient.ConnectAsync(options, CancellationToken.None);

On connectAsync I get an error, "Unknown error occured while processing certificates. Not sure what is wrong here ? I have tried to follow the documentation as well

https://github.com/dotnet/MQTTnet/wiki/Client#certificate-based-authentication -- TLS using client Certificate

Error Message

An unknown error occurred while processing the certificate.

Stack Trace:

       at System.Net.Security.SslStream.<ForceAuthenticationAsync>d__175`1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MQTTnet.Implementations.MqttTcpChannel.<ConnectAsync>d__17.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at MQTTnet.Implementations.MqttTcpChannel.<ConnectAsync>d__17.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MQTTnet.Adapter.MqttChannelAdapter.<ConnectAsync>d__28.MoveNext()