Configure workloads to trust a custom CA

This topic tells you how to configure workloads to trust a custom Certificate Authority (commonly called CA) for Application Single Sign-On (commonly called AppSSO).

Overview

If your ClientRegistration selects an AuthServer that serves a certificate from a custom CA, your Workload does not trust it by default. This is because the certificate is not issued by a trusted certificate authority from the Workload’s perspective.

To establish trust between a Workload and an AuthServer:

Step	Task	Link
1.	Service Operator exports the custom CA certificate Secret resource from the namespace in which it is issued.	Exporting custom CA certificate Secret
2.	Service Operator imports the custom CA certificate Secret to the namespace in which the Workload is created.	Importing custom CA certificate Secret
3.	Append the deployed Workload as a service resource claim, denoting the custom CA certificate Secret in the workload namespace.	Appending custom CA certificate Secret reference to Workload

Important

These steps are mandatory if Tanzu Application Platform is installed with the default self-signed ClusterIssuer resource, in which the CA is custom.

Exporting custom CA certificate Secret

A ca-certificates service binding Secret allows to configure trust for custom CAs.

For more information about exporting CA certificate Secrets, see Allow Workloads to trust a custom CA AuthServer.

Example: Create a ca-certificates-type ServiceBinding Secret from template and offer Tanzu Application Platform’s default self-signed CA certificate Secret to workloads namespace.

---
apiVersion: secretgen.carvel.dev/v1alpha1
kind: SecretTemplate
metadata:
  name: tap-ca-cert
  namespace: cert-manager                     # The namespace in which your custom CA Secret resides.
spec:
  inputResources:
    - name: tap-ingress-selfsigned-root-ca
      ref:
        apiVersion: v1                        # The custom CA certificate Secret.
        kind: Secret                          # ^^
        name: tap-ingress-selfsigned-root-ca  # ^^
  template:
    data:
      ca.crt: $(.tap-ingress-selfsigned-root-ca.data.tls\.crt)
    stringData:
      type: ca-certificates
---
apiVersion: secretgen.carvel.dev/v1alpha1
kind: SecretExport
metadata:
  name: tap-ca-cert           # The name of the SecretTemplate that created the "ca-certificates" Secret.
  namespace: cert-manager     # The namespace in which Tanzu Application Platform's self-signed ClusterIssuer stores its CA cert Secret.
spec:
  toNamespace: my-apps        # The namespace in which Workloads are deployed.

Importing custom CA certificate Secret

After the custom CA certificate Secret is exported from its original namespace, you can import it into the workloads’ namespace.

Example: Accept Tanzu Application Platform’s default self-signed CA certificate Secret offer.

---
apiVersion: secretgen.carvel.dev/v1alpha1
kind: SecretImport
metadata:
  name: tap-ca-cert
  namespace: my-apps            # The namespace in which Workloads are deployed.
spec:
  fromNamespace: cert-manager   # The namespace in which your custom CA certificate Secret resides.

Appending custom CA certificate Secret reference to Workload

With custom CA certificate available in the workloads’ namespace, you can append it to the Workload as a service resource claim:

Example: Appending custom CA certificate Secret as a resource claim.

---
apiVersion: carto.run/v1alpha1
kind: Workload
# ...
spec:
  serviceClaims:
    - name: ca-cert
      ref:
        apiVersion: v1    # The custom CA Secret template that is imported into the workloads' namespace.
        kind: Secret      # ^^
        name: tap-ca-cert # ^^
    # ...

Alternatively, you can provide the workload with a --service-ref parameter for the same effect:

--service-ref "ca-cert=v1:Secret:tap-ca-cert"

For more information about secretgen-controller and its APIs, see secretgen-controller documentation in GitHub.