iot-central-x509-csharp-code.md

author	ms.author	ms.service	ms.topic	ms.date
dominicbetts	dobett	iot-develop	include	12/17/2021

To modify the sample code to use the X.509 certificates:

1. In the IoTHubDeviceSamples Visual Studio solution, open the Parameter.cs file in the TemperatureController project.

2. Add the following two parameter definitions to the class:

   [Option(
       'x',
       "CertificatePath",
       HelpText = "(Required if DeviceSecurityType is \"dps\"). \nThe device PFX file to use during device provisioning." +
       "\nDefaults to environment variable \"IOTHUB_DEVICE_X509_CERT\".")]
   public string CertificatePath { get; set; } = Environment.GetEnvironmentVariable("IOTHUB_DEVICE_X509_CERT");
   
   [Option(
       'p',
       "CertificatePassword",
       HelpText = "(Required if DeviceSecurityType is \"dps\"). \nThe password of the PFX certificate file." +
       "\nDefaults to environment variable \"IOTHUB_DEVICE_X509_PASSWORD\".")]
   public string CertificatePassword { get; set; } = Environment.GetEnvironmentVariable("IOTHUB_DEVICE_X509_PASSWORD");

   Save the changes.

3. In the IoTHubDeviceSamples Visual Studio solution, open the Program.cs file in the TemperatureController project.

4. Add the following using statements:

   using System.Security.Cryptography.X509Certificates;
   using System.IO;

5. Add the following method to the class:

   private static X509Certificate2 LoadProvisioningCertificate(Parameters parameters)
   {
       var certificateCollection = new X509Certificate2Collection();
       certificateCollection.Import(
           parameters.CertificatePath,
           parameters.CertificatePassword,
           X509KeyStorageFlags.UserKeySet);
   
       X509Certificate2 certificate = null;
   
       foreach (X509Certificate2 element in certificateCollection)
       {
           Console.WriteLine($"Found certificate: {element?.Thumbprint} {element?.Subject}; PrivateKey: {element?.HasPrivateKey}");
           if (certificate == null && element.HasPrivateKey)
           {
               certificate = element;
           }
           else
           {
               element.Dispose();
           }
       }
   
       if (certificate == null)
       {
           throw new FileNotFoundException($"{parameters.CertificatePath} did not contain any certificate with a private key.");
       }
   
       Console.WriteLine($"Using certificate {certificate.Thumbprint} {certificate.Subject}");
   
       return certificate;
   }

6. In the SetupDeviceClientAsync method, replace the block of code for case "dps" with the following code:

   case "dps":
       s_logger.LogDebug($"Initializing via DPS");
       Console.WriteLine($"Loading the certificate...");
       X509Certificate2 certificate = LoadProvisioningCertificate(parameters);
       DeviceRegistrationResult dpsRegistrationResult = await ProvisionDeviceAsync(parameters, certificate, cancellationToken);
       var authMethod = new DeviceAuthenticationWithX509Certificate(dpsRegistrationResult.DeviceId, certificate);
       deviceClient = InitializeDeviceClient(dpsRegistrationResult.AssignedHub, authMethod);
       break;

7. Replace the ProvisionDeviceAsync method with the following code:

   private static async Task<DeviceRegistrationResult> ProvisionDeviceAsync(Parameters parameters, X509Certificate2 certificate, CancellationToken cancellationToken)
   {
       SecurityProvider security = new SecurityProviderX509Certificate(certificate);
       ProvisioningTransportHandler mqttTransportHandler = new ProvisioningTransportHandlerMqtt();
       ProvisioningDeviceClient pdc = ProvisioningDeviceClient.Create(parameters.DpsEndpoint, parameters.DpsIdScope, security, mqttTransportHandler);
   
       var pnpPayload = new ProvisioningRegistrationAdditionalData
       {
           JsonData = PnpConvention.CreateDpsPayload(ModelId),
       };
       return await pdc.RegisterAsync(pnpPayload, cancellationToken);
   }

   Save the changes.