Configuring a custom PKI

Some platform components, such as the web console, use Routes for communication and must trust other components’ certificates to interact with them. If you are using a custom public key infrastructure (PKI), you must configure it so its privately signed CA certificates are recognized across the cluster.

You can leverage the Proxy API to add cluster-wide trusted CA certificates. You must do this either during installation or at runtime.

• During installation, configure the cluster-wide proxy. You must define your privately signed CA certificates in the install-config.yaml file’s additionalTrustBundle setting.

  The installation program generates a ConfigMap that is named user-ca-bundle that contains the additional CA certificates you defined. The Cluster Network Operator then creates a trusted-ca-bundle ConfigMap that merges these CA certificates with the Fedora CoreOS (FCOS) trust bundle; this ConfigMap is referenced in the Proxy object’s trustedCA field.

• At runtime, modify the default Proxy object to include your privately signed CA certificates (part of cluster’s proxy enablement workflow). This involves creating a ConfigMap that contains the privately signed CA certificates that should be trusted by the cluster, and then modifying the proxy resource with the trustedCA referencing the privately signed certificates’ ConfigMap.

Configuring the cluster-wide proxy during installation

Production environments can deny direct access to the Internet and instead have an HTTP or HTTPS proxy available. You can configure a new OKD cluster to use a proxy by configuring the proxy settings in the install-config.yaml file.

Prerequisites

• You have an existing install-config.yaml file.

• You reviewed the sites that your cluster requires access to and determined whether any of them need to bypass the proxy. By default, all cluster egress traffic is proxied, including calls to hosting cloud provider APIs. You added sites to the Proxy object’s spec.noProxy field to bypass the proxy if necessary.

  The Proxy object status.noProxy field is populated with the values of the networking.machineNetwork[].cidr, networking.clusterNetwork[].cidr, and networking.serviceNetwork[] fields from your installation configuration. For installations on Amazon Web Services (AWS), Google Cloud Platform (GCP), Microsoft Azure, and Red Hat OpenStack Platform (RHOSP), the Proxy object status.noProxy field is also populated with the instance metadata endpoint (169.254.169.254).

• If your cluster is on AWS, you added the ec2.<region>.amazonaws.com, elasticloadbalancing.<region>.amazonaws.com, and s3.<region>.amazonaws.com endpoints to your VPC endpoint. These endpoints are required to complete requests from the nodes to the AWS EC2 API. Because the proxy works on the container level, not the node level, you must route these requests to the AWS EC2 API through the AWS private network. Adding the public IP address of the EC2 API to your allowlist in your proxy server is not sufficient.

Procedure

1. Edit your install-config.yaml file and add the proxy settings. For example:

   apiVersion: v1
   baseDomain: my.domain.com
   proxy:
     httpProxy: http://<username>:<pswd>@<ip>:<port> (1)
     httpsProxy: https://<username>:<pswd>@<ip>:<port> (2)
     noProxy: example.com (3)
   additionalTrustBundle: | (4)
       -----BEGIN CERTIFICATE-----
       <MY_TRUSTED_CA_CERT>
       -----END CERTIFICATE-----
   ...

   1	A proxy URL to use for creating HTTP connections outside the cluster. The URL scheme must be http. If you use an MITM transparent proxy network that does not require additional proxy configuration but requires additional CAs, you must not specify an httpProxy value.
   2	A proxy URL to use for creating HTTPS connections outside the cluster. If you use an MITM transparent proxy network that does not require additional proxy configuration but requires additional CAs, you must not specify an httpsProxy value.
   3	A comma-separated list of destination domain names, domains, IP addresses, or other network CIDRs to exclude proxying. Preface a domain with . to match subdomains only. For example, .y.com matches x.y.com, but not y.com. Use * to bypass proxy for all destinations.
   4	If provided, the installation program generates a config map that is named user-ca-bundle in the openshift-config namespace that contains one or more additional CA certificates that are required for proxying HTTPS connections. The Cluster Network Operator then creates a trusted-ca-bundle config map that merges these contents with the Fedora CoreOS (FCOS) trust bundle, and this config map is referenced in the Proxy object’s trustedCA field. The additionalTrustBundle field is required unless the proxy’s identity certificate is signed by an authority from the FCOS trust bundle. If you use an MITM transparent proxy network that does not require additional proxy configuration but requires additional CAs, you must provide the MITM CA certificate.

   The installation program does not support the proxy readinessEndpoints field.

2. Save the file and reference it when installing OKD.

The installation program creates a cluster-wide proxy that is named cluster that uses the proxy settings in the provided install-config.yaml file. If no proxy settings are provided, a cluster Proxy object is still created, but it will have a nil spec.

Enabling the cluster-wide proxy

The Proxy object is used to manage the cluster-wide egress proxy. When a cluster is installed or upgraded without the proxy configured, a Proxy object is still generated but it will have a nil spec. For example:

apiVersion: config.openshift.io/v1
kind: Proxy
metadata:
  name: cluster
spec:
  trustedCA:
    name: ""
status:

A cluster administrator can configure the proxy for OKD by modifying this cluster Proxy object.

Prerequisites

• Cluster administrator permissions

• OKD oc CLI tool installed

Procedure

1. Create a ConfigMap that contains any additional CA certificates required for proxying HTTPS connections.

   You can skip this step if the proxy’s identity certificate is signed by an authority from the RHCOS trust bundle.

   1. Create a file called user-ca-bundle.yaml with the following contents, and provide the values of your PEM-encoded certificates:

      apiVersion: v1
      data:
        ca-bundle.crt: | (1)
          <MY_PEM_ENCODED_CERTS> (2)
      kind: ConfigMap
      metadata:
        name: user-ca-bundle (3)
        namespace: openshift-config (4)

      1	This data key must be named ca-bundle.crt.
      2	One or more PEM-encoded X.509 certificates used to sign the proxy’s identity certificate.
      3	The ConfigMap name that will be referenced from the Proxy object.
      4	The ConfigMap must be in the openshift-config namespace.

   2. Create the ConfigMap from this file:

      $ oc create -f user-ca-bundle.yaml

2. Use the oc edit command to modify the Proxy object:

   $ oc edit proxy/cluster

3. Configure the necessary fields for the proxy:

   apiVersion: config.openshift.io/v1
   kind: Proxy
   metadata:
     name: cluster
   spec:
     httpProxy: http://<username>:<pswd>@<ip>:<port> (1)
     httpsProxy: http://<username>:<pswd>@<ip>:<port> (2)
     noProxy: example.com (3)
     readinessEndpoints:
     - http://www.google.com (4)
     - https://www.google.com
     trustedCA:
       name: user-ca-bundle (5)

   1	A proxy URL to use for creating HTTP connections outside the cluster. The URL scheme must be http.
   2	A proxy URL to use for creating HTTPS connections outside the cluster.
   3	A comma-separated list of destination domain names, domains, IP addresses or other network CIDRs to exclude proxying. Preface a domain with . to match subdomains only. For example, .y.com matches x.y.com, but not y.com. Use * to bypass proxy for all destinations. If you scale up workers that are not included in the network defined by the networking.machineNetwork[].cidr field from the installation configuration, you must add them to this list to prevent connection issues. This field is ignored if neither the httpProxy or httpsProxy fields are set.
   4	One or more URLs external to the cluster to use to perform a readiness check before writing the httpProxy and httpsProxy values to status.
   5	A reference to the ConfigMap in the openshift-config namespace that contains additional CA certificates required for proxying HTTPS connections. Note that the ConfigMap must already exist before referencing it here. This field is required unless the proxy’s identity certificate is signed by an authority from the RHCOS trust bundle.

4. Save the file to apply the changes.

Certificate injection using Operators

Once your custom CA certificate is added to the cluster via ConfigMap, the Cluster Network Operator merges the user-provided and system CA certificates into a single bundle and injects the merged bundle into the Operator requesting the trust bundle injection.

Operators request this injection by creating an empty ConfigMap with the following label:

config.openshift.io/inject-trusted-cabundle="true"

The Operator mounts this ConfigMap into the container’s local trust store.

Certificate injection is not limited to Operators. The Cluster Network Operator injects certificates across any namespace when an empty ConfigMap is created with the config.openshift.io/inject-trusted-cabundle=true label.

The ConfigMap can reside in any namespace, but the ConfigMap must be mounted as a volume to each container within a Pod that requires a custom CA. For example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-example-custom-ca-deployment
  namespace: my-example-custom-ca-ns
spec:
  ...
    spec:
      ...
      containers:
        - name: my-container-that-needs-custom-ca
          volumeMounts:
          - name: trusted-ca
            mountPath: /etc/pki/ca-trust/extracted/pem
            readOnly: true
      volumes:
      - name: trusted-ca
        configMap:
          name: trusted-ca
          items:
            - key: ca-bundle.crt (1)
              path: tls-ca-bundle.pem (2)