Enabling automatic TLS certificate provisioning

    Knative supports the following Auto TLS modes:

    1. Using DNS-01 challenge

      In this mode, your cluster needs to be able to talk to your DNS server to verify the ownership of your domain.

      • Provision Certificate per namespace is supported when using DNS-01 challenge mode.

        • This is the recommended mode for faster certificate provision.
        • In this mode, a single Certificate will be provisioned per namespace and is reused across the Knative Services within the same namespace.

      • Provision Certificate per Knative Service is supported when using DNS-01 challenge mode.

        • This is the recommended mode for better certificate islation between Knative Services.
        • In this mode, a Certificate will be provisioned for each Knative Service.
        • The TLS effective time is longer as it needs Certificate provision for each Knative Service creation.

    2. Using HTTP-01 challenge

      • In this type, your cluster does not need to be able to talk to your DNS server. You just need to map your domain to the IP of the cluser ingress.
      • When using HTTP-01 challenge, a certificate will be provisioned per Knative Service. Certificate provision per namespace is not supported when using HTTP-01 challenge.

    You must meet the following prerequisites to enable auto TLS:

    • The following must be installed on your Knative cluter:
    • Your Knative cluster must be configured to use a custom domain.
    • Your DNS provider must be setup and configured to your domain.
    • If you want to use HTTP-01 challenge, you need to configure your custom domain to map to the IP of ingress. You can achieve this by adding a DNS A record to map the domain to the IP according to the instructions of your DNS provider.

    To enable support for Auto TLS in Knative:

    1. Create and add the ClusterIssuer configuration file to your Knative cluster to define who issues the TLS certificates, how requests are validated, and which DNS provider validates those requests.

      ClusterIssuer for DNS-01 challenge

      Use the cert-manager reference to determine how to configure your ClusterIssuer file:

      • See the generic ClusterIssuer example

      • Also see the

        Example: Cloud DNS ClusterIssuer configuration file:

    1. #### ClusterIssuer for HTTP-01 challenge
    3. Run the following command to apply the ClusterIssuer for HTT01 challenge:
    5. ```
    6. kubectl apply -f - <<EOF
    7. apiVersion: cert-manager.io/v1alpha2
    8. kind: ClusterIssuer
    9. metadata:
    10.   name: letsencrypt-http01-issuer
    11. spec:
    12.   acme:
    13.       name: letsencrypt
    14.     server: https://acme-v02.api.letsencrypt.org/directory
    15.     solvers:
    16.     - http01:
    17.        ingress:
    18.          class: istio
    19. EOF
    20. ```

    1. Ensure that the ClusterIssuer is created successfully:

      1. kubectl get clusterissuer <cluster-issuer-name> --output yaml

      Result: The Status.Conditions should include Ready=True.

    Install networking-certmanager deployment

    1. Determine if networking-certmanager is already installed by running the following command:

      1. kubectl get deployment networking-certmanager -n knative-serving

    2. If networking-certmanager is not found, run the following command:

      1. kubectl apply --filename https://github.com/knative/net-certmanager/releases/download/v0.18.0/release.yaml

    If you choose to use the mode of provisioning certificate per namespace, you need to install networking-ns-cert components.

    1. Determine if networking-ns-cert deployment is already installed by running the following command:

      1. kubectl get deployment networking-ns-cert -n knative-serving

    2. If networking-ns-cert deployment is not found, run the following command:

    Configure config-certmanager ConfigMap

    Update your config-certmanager ConfigMap in the knative-serving namespace to reference your new ClusterIssuer.

    1. Run the following command to edit your config-certmanager ConfigMap:

    2. Add the issuerRef within the data section:

      1. ...
      2. data:
      3. ...
      4.   issuerRef: |
      5.     kind: ClusterIssuer
      6.     name: letsencrypt-issuer

      Example:

      1. apiVersion: v1
      2. kind: ConfigMap
      3. metadata:
      4.   name: config-certmanager
      5.   namespace: knative-serving
      6.   labels:
      7.     networking.knative.dev/certificate-provider: cert-manager
      8. data:
      9.   issuerRef: |
      10.     kind: ClusterIssuer
      11.     name: letsencrypt-http01-issuer

      issueRef defines which ClusterIssuer will be used by Knative to issue certificates.

    3. Ensure that the file was updated successfully:

      1. kubectl get configmap config-certmanager --namespace knative-serving --output yaml

    1. Run the following command to edit your config-network ConfigMap:

      1. kubectl edit configmap config-network --namespace knative-serving

    2. Add the autoTLS: Enabled attribute under the data section:

      1. ...
      2. data:
      3.   autoTLS: Enabled
      4. ...

      Example:

      1. apiVersion: v1
      2. kind: ConfigMap
      3. metadata:
      5.   namespace: knative-serving
      6. data:
      7.    ...
      8.    autoTLS: Enabled
      9.    ...

    3. Configure how HTTP and HTTPS requests are handled in the attribute.

      By default, Knative ingress is configured to serve HTTP traffic (httpProtocol: Enabled). Now that your cluster is configured to use TLS certificates and handle HTTPS traffic, you can specify whether or not any HTTP traffic is allowed.

      Supported httpProtocol values:

      • Enabled: Serve HTTP traffic.
      • Disabled: Rejects all HTTP traffic.
      • Redirected: Responds to HTTP request with a 302 redirect to ask the clients to use HTTPS.

      Example:

      1. apiVersion: v1
      2. kind: ConfigMap
      3. metadata:
      4.   name: config-network
      5.   namespace: knative-serving
      6. data:
      7.   ...
      8.   autoTLS: Enabled
      9.   ...
      10.   httpProtocol: Redirected
      11.   ...

      Note: When using HTTP-01 challenge, httpProtocol field has to be set to Enabled to make sure HTTP-01 challenge requests can be accepted by the cluster.

    4. Ensure that the file was updated successfully:

      1. kubectl get configmap config-network --namespace knative-serving --output yaml

    Congratulations! Knative is now configured to obtain and renew TLS certificates. When your TLS certificate is active on your cluster, your Knative services will be able to handle HTTPS traffic.

    Verify Auto TLS

    1. Run the following comand to create a Knative Service:

      1. kubectl apply -f https://raw.githubusercontent.com/knative/docs/master/docs/serving/autoscaling/autoscale-go/service.yaml

    2. When the certificate is provisioned (which could take up to several minutes depending on the challenge type), you should see something like:

      1. NAME               URL                                           LATESTCREATED            LATESTREADY              READY   REASON
      2. autoscale-go       https://autoscale-go.default.{custom-domain}   autoscale-go-6jf85 autoscale-go-6jf85       True

      Note that the URL will be https in this case.

    Using the previous autoscale-go example:

    1. Edit the service using kubectl edit service.serving.knative.dev/autoscale-go -n default and add the annotation:
    1.  apiVersion: serving.knative.dev/v1
    2.  kind: Service
    3.  metadata:
    4.    annotations:
    5.     ...
    6.      networking.knative.dev/disableAutoTLS: "true"
    7.     ...
    1. The service URL should now be http, indicating that AutoTLS is disabled:
    1. NAME           URL                                          LATEST               AGE     CONDITIONS   READY   REASON
    2. autoscale-go   http://autoscale-go.default.1.arenault.dev   autoscale-go-dd42t   8m17s   3 OK / 3     True