Configuring a custom PKI | Networking | OpenShift Container Platform 4.8

Configuring the cluster-wide proxy during installation
Enabling the cluster-wide proxy
Certificate injection using Operators

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 Red Hat Enterprise Linux CoreOS (RHCOS) 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.

The installer configuration’s additionalTrustBundle field and the proxy resource’s trustedCA field are used to manage the cluster-wide trust bundle; additionalTrustBundle is used at install time and the proxy’s trustedCA is used at runtime.

The trustedCA field is a reference to a ConfigMap containing the custom certificate and key pair used by the cluster component.

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 OpenShift Container Platform 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).

Procedure

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`.
2	A proxy URL to use for creating HTTPS connections outside the cluster.
3	A comma-separated list of destination domain names, IP addresses, or other network CIDRs to exclude from proxying. Preface a domain with `.` to match subdomains only. For example, `.y.com` matches `x.y.com`, but not `y.com`. Use `*` to bypass the 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 to hold the additional CA certificates. If you provide `additionalTrustBundle` and at least one proxy setting, the `Proxy` object is configured to reference the `user-ca-bundle` config map in the `trustedCA` field. The Cluster Network Operator then creates a `trusted-ca-bundle` config map that merges the contents specified for the `trustedCA` parameter with the RHCOS trust bundle. The `additionalTrustBundle` field is required unless the proxy’s identity certificate is signed by an authority from the RHCOS trust bundle.

The installation program does not support the proxy readinessEndpoints field.

Save the file and reference it when installing OpenShift Container Platform.

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.

Only the Proxy object named cluster is supported, and no additional proxies can be created.

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 OpenShift Container Platform by modifying this cluster Proxy object.

Only the Proxy object named cluster is supported, and no additional proxies can be created.

Prerequisites

Cluster administrator permissions
OpenShift Container Platform oc CLI tool installed

Procedure

Create a config map 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.

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 config map name that will be referenced from the `Proxy` object.
4	The config map must be in the `openshift-config` namespace.

Create the config map from this file:
```
$ oc create -f user-ca-bundle.yaml
```

Use the oc edit command to modify the Proxy object:
```
$ oc edit proxy/cluster
```

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: https://<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. The URL scheme must be either `http` or `https`. Specify a URL for the proxy that supports the URL scheme. For example, most proxies will report an error if they are configured to use `https` but they only support `http`. This failure message may not propagate to the logs and can appear to be a network connection failure instead. If using a proxy that listens for `https` connections from the cluster, you may need to configure the cluster to accept the CAs and certificates that the proxy uses.
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 config map in the `openshift-config` namespace that contains additional CA certificates required for proxying HTTPS connections. Note that the config map 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.

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"

An example of the empty ConfigMap:

apiVersion: v1
data: {}
kind: ConfigMap
metadata:
  labels:
    config.openshift.io/inject-trusted-cabundle: "true"
  name: ca-inject (1)
  namespace: apache

1	Specifies the empty ConfigMap name.

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

Adding a trusted CA certificate is only needed if the certificate is not included in the Red Hat Enterprise Linux CoreOS (RHCOS) trust bundle.

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)

1	`ca-bundle.crt` is required as the ConfigMap key.
2	`tls-ca-bundle.pem` is required as the ConfigMap path.