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Configuring IPsec encryption

With IPsec enabled, all pod-to-pod network traffic between nodes on the OVN-Kubernetes cluster network is encrypted with IPsec Transport mode.

IPsec is disabled by default. It can be enabled either during or after installing the cluster. For information about cluster installation, see OpenShift Container Platform installation overview. If you need to enable IPsec after cluster installation, you must first resize your cluster MTU to account for the overhead of the IPsec ESP IP header.

The following support limitations exist for IPsec on a OpenShift Container Platform cluster:

  • You must disable IPsec before updating to OpenShift Container Platform 4.15. After disabling IPsec, you must also delete the associated IPsec daemonsets. There is a known issue that can cause interruptions in pod-to-pod communication if you update without disabling IPsec. (OCPBUGS-43323)

The following documentation describes how to enable and disable IPSec after cluster installation.

Prerequisites

  • You have decreased the size of the cluster MTU by 46 bytes to allow for the additional overhead of the IPsec ESP header. For more information on resizing the MTU that your cluster uses, see Changing the MTU for the cluster network.

Types of network traffic flows encrypted by IPsec

With IPsec enabled, only the following network traffic flows between pods are encrypted:

  • Traffic between pods on different nodes on the cluster network

  • Traffic from a pod on the host network to a pod on the cluster network

The following traffic flows are not encrypted:

  • Traffic between pods on the same node on the cluster network

  • Traffic between pods on the host network

  • Traffic from a pod on the cluster network to a pod on the host network

The encrypted and unencrypted flows are illustrated in the following diagram:

IPsec encrypted and unencrypted traffic flows

Network connectivity requirements when IPsec is enabled

You must configure the network connectivity between machines to allow OpenShift Container Platform cluster components to communicate. Each machine must be able to resolve the hostnames of all other machines in the cluster.

Table 1. Ports used for all-machine to all-machine communications
Protocol Port Description

UDP

500

IPsec IKE packets

4500

IPsec NAT-T packets

ESP

N/A

IPsec Encapsulating Security Payload (ESP)

Encryption protocol and IPsec mode

The encrypt cipher used is AES-GCM-16-256. The integrity check value (ICV) is 16 bytes. The key length is 256 bits.

The IPsec mode used is Transport mode, a mode that encrypts end-to-end communication by adding an Encapsulated Security Payload (ESP) header to the IP header of the original packet and encrypts the packet data. OpenShift Container Platform does not currently use or support IPsec Tunnel mode for pod-to-pod communication.

Security certificate generation and rotation

The Cluster Network Operator (CNO) generates a self-signed X.509 certificate authority (CA) that is used by IPsec for encryption. Certificate signing requests (CSRs) from each node are automatically fulfilled by the CNO.

The CA is valid for 10 years. The individual node certificates are valid for 5 years and are automatically rotated after 4 1/2 years elapse.

Enabling IPsec encryption

As a cluster administrator, you can enable IPsec encryption after cluster installation.

Prerequisites

  • Install the OpenShift CLI (oc).

  • Log in to the cluster as a user with cluster-admin privileges.

  • You have reduced the size of your cluster maximum transmission unit (MTU) by 46 bytes to allow for the overhead of the IPsec ESP header.

Procedure

  • To enable IPsec encryption, enter the following command:

    $ oc patch networks.operator.openshift.io cluster --type=merge \
-p '{"spec":{"defaultNetwork":{"ovnKubernetesConfig":{"ipsecConfig":{ }}}}}'
Verification

  1. To find the names of the OVN-Kubernetes control plane pods, enter the following command:

    $ oc get pods -l app=ovnkube-master -n openshift-ovn-kubernetes
    Example output
    NAME                   READY   STATUS    RESTARTS   AGE
ovnkube-master-fvtnh   6/6     Running   0          122m
ovnkube-master-hsgmm   6/6     Running   0          122m
ovnkube-master-qcmdc   6/6     Running   0          122m

  2. Verify that IPsec is enabled on your cluster by entering the following command. The command output must state true to indicate that the node has IPsec enabled.

    $ oc -n openshift-ovn-kubernetes rsh ovnkube-master-<pod_number_sequence> \ (1)
  ovn-nbctl --no-leader-only get nb_global . ipsec
    1 Replace <pod_number_sequence> with the random sequence of letters, fvtnh, for a data plane pod from the previous step.

Disabling IPsec encryption

As a cluster administrator, you can disable IPsec encryption only if you enabled IPsec after cluster installation.

After disabling IPsec, you must delete the associated IPsec daemonsets pods. If you do not delete these pods, you might experience issues with your cluster.
Prerequisites

  • Install the OpenShift CLI (oc).

  • Log in to the cluster with a user with cluster-admin privileges.

Procedure

  1. To disable IPsec encryption, enter the following command:

    $ oc patch networks.operator.openshift.io/cluster --type=json \
  -p='[{"op":"remove", "path":"/spec/defaultNetwork/ovnKubernetesConfig/ipsecConfig"}]'

  2. To find the name of the OVN-Kubernetes data plane pod that exists on the master node in your cluster, enter the following command:

    $ oc get pods -n openshift-ovn-kubernetes -l=app=ovnkube-master
    Example output
    ovnkube-master-5xqbf                      8/8     Running   0              28m
...

  3. Verify that the master node in your cluster has IPsec disabled by entering the following command. The command output must state false to indicate that the node has IPsec disabled.

    $ oc -n openshift-ovn-kubernetes -c nbdb rsh ovnkube-master-<pod_number_sequence> \(1)
  ovn-nbctl --no-leader-only get nb_global . ipsec
    1 Replace <pod_number_sequence> with the random sequence of letters, such as 5xqbf, for the data plane pod from the previous step.

  4. To remove the IPsec ovn-ipsec daemonset pod from the openshift-ovn-kubernetes namespace on the node, enter the following command:

    $ oc delete daemonset ovn-ipsec -n openshift-ovn-kubernetes (1)
    1 The ovn-ipsec daemonset configures IPsec connections for east-west traffic on the node.

  5. Verify that the ovn-ipsec daemonset pod was removed from the all nodes in your cluster by entering the following command. If the command output does not list the pod, the removal operation is successful.

    $ oc get pods -n openshift-ovn-kubernetes -l=app=ovn-ipsec

    You might need to re-run the command for deleting the pod because sometimes the initial command attempt might not delete the pod.

  6. Optional: You can increase the size of your cluster MTU by 46 bytes because there is no longer any overhead from the IPsec ESP header in IP packets.

Additional resources