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Certificate management for Azure IoT Operations internal communication

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All communication within Azure IoT Operations is encrypted using TLS. To help you get started, Azure IoT Operations is deployed with a default root CA and issuer for TLS server certificates. You can use the default setup for development and testing purposes. For a production deployment, we recommend using your own CA issuer and an enterprise PKI solution.

Default self-signed issuer and root CA certificate for TLS server certificates

To help you get started, Azure IoT Operations is deployed with a default self-signed issuer and root CA certificate for TLS server certificates. You can use this issuer for development and testing. Azure IoT Operations uses cert-manager to manage TLS certificates, and trust-manager to distribute trust bundles to components.

  • The CA certificate is self-signed and not trusted by any clients outside of Azure IoT Operations. The subject of the CA certificate is CN=Azure IoT Operations Quickstart Root CA - Not for Production. The CA certificate is automatically rotated by cert-manager.

  • The root CA certificate is stored in a Kubernetes secret called azure-iot-operations-aio-ca-certificate under the cert-manager namespace.

  • The public portion of the root CA certificate is stored in a ConfigMap called azure-iot-operations-aio-ca-trust-bundle under the azure-iot-operations namespace. You can retrieve the CA certificate from the ConfigMap and inspect it with kubectl and openssl. The ConfigMap is kept updated by trust-manager when the CA certificate is rotated by cert-manager.

    kubectl get configmap azure-iot-operations-aio-ca-trust-bundle -n azure-iot-operations -o "jsonpath={.data['ca\.crt']}" | openssl x509 -text -noout

    Certificate: 
    Data: 
        Version: 3 (0x2) 
        Serial Number: 
            <SERIAL-NUMBER> 
        Signature Algorithm: sha256WithRSAEncryption 
        Issuer: O=Microsoft, CN=Azure IoT Operations Quickstart Root CA - Not for Production 
        Validity 
            Not Before: Sep 18 20:42:19 2024 GMT 
            Not After : Sep 18 20:42:19 2025 GMT 
        Subject: O=Microsoft, CN=Azure IoT Operations Quickstart Root CA - Not for Production 
        Subject Public Key Info: 
            Public Key Algorithm: rsaEncryption 
                Public-Key: (2048 bit) 
                Modulus: <MODULUS> 
                                    Exponent: 65537 (0x10001) 
        X509v3 extensions: 
            X509v3 Key Usage: critical 
                Certificate Sign, CRL Sign 
            X509v3 Basic Constraints: critical 
                CA:TRUE 
            X509v3 Subject Key Identifier: 
                <SUBJECT-KEY-IDENTIFIER> 
    Signature Algorithm: sha256WithRSAEncryption 
[Signature]

  • By default, there's already an issuer configured in the azure-iot-operations namespace called azure-iot-operations-aio-certificate-issuer. It's used as the common issuer for all TLS server certificates for IoT Operations. MQTT broker uses an issuer created from the same CA certificate which is signed by the self-signed issuer to issue TLS server certificates for the default TLS listener on port 18883. You can inspect the issuer with the following command:

    kubectl get clusterissuer azure-iot-operations-aio-certificate-issuer -o yaml

    apiVersion: cert-manager.io/v1 
kind: ClusterIssuer 
metadata: 
  creationTimestamp: "2024-09-18T20:42:17Z" 
  generation: 1 
  name: azure-iot-operations-aio-certificate-issuer 
  resourceVersion: "36665" 
  uid: 592700a6-95e0-4788-99e4-ea93934bd330 
spec: 
  ca: 
    secretName: azure-iot-operations-aio-ca-certificate 
status: 
  conditions: 
  - lastTransitionTime: "2024-09-18T20:42:22Z" 
    message: Signing CA verified 
    observedGeneration: 1 
    reason: KeyPairVerified 
    status: "True" 
    type: Ready

Bring your own issuer

For production deployments, we recommend that you set up Azure IoT Operations with an enterprise PKI to manage certificates and that you bring your own issuer which works with your enterprise PKI instead of using the default self-signed issuer to issue TLS certificates for internal communication.

To set up Azure IoT Operations with your own issuer, use the following steps before deploying an instance to your cluster:

  1. Follow the steps in Prepare your cluster to set up your cluster.

  2. Install cert-manager. Cert-manager manages TLS certificates.

  3. Install trust-manager. While installing trust manager, set the trust namespace to cert-manager. For example:

    helm upgrade trust-manager jetstack/trust-manager --install --namespace cert-manager --set app.trust.namespace=cert-manager --wait

    Trust-manager is used to distribute a trust bundle to components.

  4. Create the Azure IoT Operations namespace.

    kubectl create namespace azure-iot-operations

  5. Deploy an issuer that works with cert-manager. For a list of all supported issuers, see cert-manager issuers.

    The issuer can be of type ClusterIssuer or Issuer. If using Issuer, the issuer resource must be created in the Azure IoT Operations namespace.

  6. Set up trust bundle in the Azure IoT Operations namespace.

    1. To set up trust bundle, create a ConfigMap in the Azure IoT Operations namespace. Place the public key portion of your CA certificate into the config map with a key name of your choice.

    2. Get the public key portion of your CA certificate. The steps to acquire the public key depend on the issuer you choose.

    3. Create the ConfigMap. For example:

      kubectl create configmap -n azure-iot-operations <YOUR_CONFIGMAP_NAME> --from-file=<CA_CERTIFICATE_FILENAME_PEM_OR_DER>

  7. Follow steps in Deploy Azure IoT Operations to deploy, with a few changes.

    1. Add the --user-trust parameter while preparing cluster. For example:

      az iot ops init --subscription <SUBSCRIPTION_ID> --cluster <CLUSTER_NAME>  -g <RESOURCE_GROUP> --user-trust

    2. Add the --trust-settings parameter with the necessary information while deploying Azure IoT Operations. For example:

    az iot ops create --subscription <SUBSCRIPTION_ID> -g <RESOURCE_GROUP> --cluster <CLUSTER_NAME> --custom-location <CUSTOM_LOCATION> -n <INSTANCE_NAME> --sr-resource-id <SCHEMAREGISTRY_RESOURCE_ID> --trust-settings configMapName=<CONFIGMAP_NAME> configMapKey=<CONFIGMAP_KEY_WITH_PUBLICKEY_VALUE> issuerKind=<CLUSTERISSUER_OR_ISSUER> issuerName=<ISSUER_NAME>