Connection to mosquitto using tls1.3 with only ca.crt

[grzegorzkloc]

I am working on an app which is to connect to a mosquitto broker using tls1.3. I will only get a ca.crt from the broker and no client certificates will be used.
My 1st question is am I doing it in a correct way (code below) as I could not find any example of connection using only a ca.crt.
My 2nd question is, When I use below code and configuration I keep getting the following exception:
"The client and server cannot communicate, because they do not possess a common algorithm". The exception does not change when I downgrade to tls1.2. Also, when I try to connect using a python app it works like a charm.

I am using .NetFramework 4.6.2,

mosquitto.conf

    acl_file ./configs/acl.acl
    password_file ./configs/pwfile
    allow_anonymous false
    listener 8883
    cafile ./certs/ca.crt
    certfile ./certs/root.crt
    keyfile ./certs/root.key
    tls_version tlsv1.3

I am creating the client in the following way:

ServicePointManager.SecurityProtocol = (SecurityProtocolType) 12288;
  var caCert = X509Certificate.CreateFromSignedFile(CertificatePath);
    var mqttFactory = new MqttFactory();
    var tlsOptions = new MqttClientTlsOptions
    			{
    				UseTls = true,
    				Certificates = new List<X509Certificate> { caCert },
    				SslProtocol = (SslProtocols)12288,
    				CertificateValidationHandler = delegate { return true; },
    				IgnoreCertificateChainErrors = true,
    				IgnoreCertificateRevocationErrors = true,
    				AllowUntrustedCertificates = true
    			};
    
    			var options = new MqttClientOptions
    			{
    				ClientId = clientId,
    				ProtocolVersion = MqttProtocolVersion.V311,
    				ChannelOptions = new MqttClientTcpOptions
    				{
    					Server = "localhost",
    					Port = 8883,
    					TlsOptions = tlsOptions
    				}
    			};
    
    			if (options.ChannelOptions == null)
    			{
    				throw new InvalidOperationException();
    			}
    
    			options.Credentials = new MqttClientCredentials
    			{
    				Username = "username",
    				Password = Encoding.UTF8.GetBytes("password")
    			};
    
    			options.CleanSession = true;
    			options.KeepAlivePeriod = TimeSpan.FromSeconds(5);
    			var client = mqttFactory.CreateMqttClient();
    			client.ConnectedHandler = new MqttClientConnectedHandlerDelegate(ShowConnected);
    			client.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(ShowDisConnected);
    
    			await client.ConnectAsync(options);

[Codectory]

I'm also trying to connect to the free emqx broker (https://www.emqx.io/mqtt/public-mqtt5-broker), but I cannot connect using TLS. Even if I download the certificate and add it to the TLSBuilder, it doesn't work.

Here is the code I am using:

public Client(ClientConfiguration configuration) {

  Logger = new MqttNetLogger();
  Logger.LogMessagePublished += Logger_LogMessagePublished;
  _client = _mqttFactory.CreateManagedMqttClient(Logger);
  Configuration = configuration;
  IMqttClientOptions clientOptions;

  MqttClientOptionsBuilder clientOptionsBuilder;
  ManagedMqttClientOptionsBuilder managedOptionsBuilder;
  MqttClientOptionsBuilderTlsParameters tlsBuilder;

  clientOptionsBuilder = new MqttClientOptionsBuilder()
    .WithClientId(Configuration.ClientID)
    .WithTcpServer(Configuration.BrokerAddress, Configuration.BrokerPort)
    .WithCleanSession()
    .WithProtocolVersion(configuration.MqttProtocolVersion);
  if (configuration.EncryptionProtocol != System.Security.Authentication.SslProtocols.None)
  {
    tlsBuilder = new MqttClientOptionsBuilderTlsParameters();
    tlsBuilder.UseTls = true;
    tlsBuilder.AllowUntrustedCertificates = true;
    tlsBuilder.CertificateValidationHandler = CertificateValidationHandler;
    if (!string.IsNullOrEmpty(configuration.CertificateFile))
    {
      tlsBuilder.Certificates = new List<X509Certificate>() { X509Certificate.CreateFromCertFile(configuration.CertificateFile) };
    }
    tlsBuilder.IgnoreCertificateChainErrors = true;
    tlsBuilder.IgnoreCertificateRevocationErrors = true;
    tlsBuilder.SslProtocol = Configuration.EncryptionProtocol;
    clientOptionsBuilder.WithTls(tlsBuilder);
  }

  if (configuration.UseCredentials)
    clientOptionsBuilder.WithCredentials(configuration.LoginName, configuration.LoginPassword);

  clientOptions = clientOptionsBuilder.Build();

  managedOptionsBuilder = new ManagedMqttClientOptionsBuilder()
  .WithClientOptions(clientOptions)
  .WithAutoReconnectDelay(new TimeSpan(0, 0, 0, 0, Configuration.ReconnectDelay))
  .WithPendingMessagesOverflowStrategy(MQTTnet.Server.MqttPendingMessagesOverflowStrategy.DropOldestQueuedMessage);
  if (configuration.UseMessageStorage)
    managedOptionsBuilder.WithStorage(new RetainedClientMessageStorage(configuration.MessageStorageFilePath));
  _managedOptions = managedOptionsBuilder.Build();
  _client.UseConnectedHandler(e => InternalClientConnected(e));
  _client.UseDisconnectedHandler(e => InternalClientDisconnected(e));
  _client.UseApplicationMessageReceivedHandler(e => NewMessage(e));

}

Other applications work the added certificate or with the open CA server signed certificate.

There are the only errors I get:

5/19/2021 3:19:02 PM 32060031: Start client...
5/19/2021 3:19:02 PM 32060031: Cleaning up...
5/19/2021 3:19:02 PM 32060031: Started
5/19/2021 3:19:02 PM 32060031: Trying to connect with server 'broker.emqx.io:8883' (Timeout=00:00:10).
5/19/2021 3:19:02 PM 32060046: Error while connecting with server.
5/19/2021 3:19:02 PM 32060046: Disconnecting [Timeout=00:00:10]
5/19/2021 3:19:02 PM 32060046: Disconnected from adapter.
5/19/2021 3:19:02 PM 32060046: Disconnected.
5/19/2021 3:19:02 PM 32060046: Stopped
5/19/2021 3:19:42 PM 32100062: Initializing...

[alvin1221]

Here's a simple example may help you as a reference: https://github.com/emqx/MQTT-Client-Examples/blob/master/mqtt-client-Csharp-MqttNet/mqtt-client-Csharp-MqttNet/Program.cs