Network policy configuration for cert-manager Operator

The cert-manager Operator for Red Hat OpenShift provides predefined NetworkPolicy resources to enhance security by controlling the ingress and egress traffic for its components. By default, this feature is disabled to prevent connectivity issues or breaking changes during an upgrade. To use this feature, you must enable it in the CertManager custom resource (CR).

After enabling the default policies, you must manually configure additional egress rules to allow outbound traffic. These rules are required for cert-manager Operator for Red Hat OpenShift to communicate with external services beyond the API server and internal DNS.

The examples of services that require custom egress rules include the following:

• ACME servers, for example, Let’s Encrypt
• DNS-01 challenge providers, for example, AWS Route53 or Cloudflare
• External CAs, such as HashiCorp Vault

note

Network policies are expected to be enabled by default in a future release, which could cause connectivity failures during an upgrade. To prepare for this change, configure the required egress policies.

Default ingress and egress rules

The default network policy applies the following ingress and egress rules to each component.

Component	Ingress ports	Egress ports	Description
cert-manager	9402	6443, 5353	Allows ingress traffic to metrics server and egress traffic to OpenShift API server.
cert-manager-webhook	9402, 10250	6443	Allows ingress traffic to metrics and webhook servers, and egress traffic to OpenShift API server and internal DNS server.
cert-manager-cainjector	9402	6443	Allows ingress traffic to metrics server and egress traffic to OpenShift API server.
istio-csr	6443, 9402	6443	Allows ingress traffic to the gRPC Istio certificate request API, metrics servers and egress traffic to OpenShift API server.

Network policy configuration parameters

You can enable and configure network policies for the cert-manager Operator components by updating the CertManager custom resource (CR). The CR includes the following parameters for enabling default network policies and defining custom egress rules.

Field	Type	Description
spec.defaultNetworkPolicy	boolean	Specifies whether to enable the default network policy for the cert-manager Operator components. Important Once you enable default network policies, you cannot disable them. This restriction prevents accidental security degradation. Before enabling this setting, ensure that you plan the network policy requirements.
spec.networkPolicies	object	Defines a list of custom network policy configuration. To apply the configuration, you must set spec.defaultNetworkPolicy to true.
spec.networkPolicies.componentName	string	Specifies the component that this network policy targets. The only valid value is CoreController.
spec.networkPolicies.egress	object	Defines the egress rules for the specified component. Set to {} to allow connections to all external providers.
spec.networkPolicies.egress.ports	object	Defines a list of network ports and protocols for the specified providers.
spec.networkPolicies.name	string	Specifies a unique name for the custom network policy, which is used to generate the NetworkPolicy resource name.

Network policy configuration examples

To control traffic flow and enhance cluster security, enable network policies and custom rules for the cert-manager Operator for Red Hat OpenShift.

To enable network policy and custom rules, see the following example:

apiVersion: operator.openshift.io/v1alpha1
kind: CertManager
metadata:
  name: cluster
spec:
  defaultNetworkPolicy: "true"

To allow egress access to all external issuer providers, see the following example:

apiVersion: operator.openshift.io/v1alpha1
kind: CertManager
metadata:
  name: cluster
spec:
  defaultNetworkPolicy: "true"
  networkPolicies:
  - name: allow-egress-to-all
    componentName: CoreController
    egress:
     - {}

To allow the cert-manager Operator controller to perform the ACME challenge self-check, see the following example. This process requires connections to the ACME provider, DNS API endpoints, and recursive DNS servers.

apiVersion: operator.openshift.io/v1alpha1
kind: CertManager
metadata:
  name: cluster
spec:
  defaultNetworkPolicy: "true"
  networkPolicies:
  - name: allow-egress-to-acme-server
    componentName: CoreController
    egress:
    - ports:
      - port: 80
        protocol: TCP
      - port: 443
        protocol: TCP
  - name: allow-egress-to-dns-service
    componentName: CoreController
    egress:
    - ports:
      - port: 53
        protocol: UDP
      - port: 53
        protocol: TCP

Verifying the network policy creation

You can verify that the default and custom NetworkPolicy resources are created.

Prerequisites

• You have enabled network policy for cert-manager Operator for Red Hat OpenShift in the CertManager custom resource.

Procedure

• Verify the list of NetworkPolicy resources in the cert-manager namespace by running the following command:

  $ oc get networkpolicy -n cert-manager

  Example output

  NAME                                             POD-SELECTOR                              AGE
  cert-manager-allow-egress-to-api-server          app.kubernetes.io/instance=cert-manager   7s
  cert-manager-allow-egress-to-dns                 app=cert-manager                          6s
  cert-manager-allow-ingress-to-metrics            app.kubernetes.io/instance=cert-manager   7s
  cert-manager-allow-ingress-to-webhook            app=webhook                               6s
  cert-manager-deny-all                            app.kubernetes.io/instance=cert-manager   8s
  cert-manager-user-allow-egress-to-acme-server    app=cert-manager                          8s
  cert-manager-user-allow-egress-to-dns-service    app=cert-manager                          7s

  The output lists the default policies and any custom policies that you created.