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 OKD 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 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 OKD 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
ProtocolPortDescription

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. OKD 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 with a user with cluster-admin privileges.

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

Procedure

  • To enable IPsec encryption, enter the following command:

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

Verifying that IPsec is enabled

As a cluster administrator, you can verify that IPsec is enabled.

Verification

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

    1. $ oc get pods -n openshift-ovn-kubernetes | grep ovnkube-master

    Example output

    1. ovnkube-master-4496s        1/1     Running   0          6h39m
    2. ovnkube-master-d6cht        1/1     Running   0          6h42m
    3. ovnkube-master-skblc        1/1     Running   0          6h51m
    4. ovnkube-master-vf8rf        1/1     Running   0          6h51m
    5. ovnkube-master-w7hjr        1/1     Running   0          6h51m
    6. ovnkube-master-zsk7x        1/1     Running   0          6h42m

  2. Verify that IPsec is enabled on your cluster:

    1. $ oc -n openshift-ovn-kubernetes -c nbdb rsh ovnkube-master-<XXXXX> \
    2.   ovn-nbctl --no-leader-only get nb_global . ipsec

    where:

    <XXXXX>

    Specifies the random sequence of letters for a pod from the previous step.

    Example output

    1. true

Disabling IPsec encryption

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

If you enabled IPsec when you installed your cluster, you cannot disable IPsec with this procedure.

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:

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

  2. 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