Encrypting communication with Etcd

Ondat supports secure communication with an external etcd cluster using mutual TLS (mTLS). With mTLS both Ondat and etcd authenticate each other ensuring that communication only happens between mutually authenticated end points, and that all communication is encrypted.

Ondat uses the certificates and keys from a Secret to cypher and authenticate Etcd traffic.

How to create the certificates Secret

The client auth certificates need the following file names, in the Secret.

  • etcd-client-ca.crt - containing the etcd Certificate Authority certificate
  • etcd-client.crt - containing the etcd Client certificate
  • etcd-client.key - containing the etcd Client key
kubectl create secret -n storageos-etcd generic \
    etcd-client-tls \
    --from-file="etcd-client-ca.crt" \
    --from-file="etcd-client.crt" \
    --from-file="etcd-client.key"

How to use the mTLS certificates Secret with Ondat

Below is an example StorageOSCluster resource that can be used to setup Ondat with etcd using mTLS.

apiVersion: storageos.com/v1
kind: StorageOSCluster
metadata:
  name: storageos-cluster
  namespace: "storageos-operator"
spec:
  # Ondat Pods are in kube-system by default
  secretRefName: "storageos-api"
  secretRefNamespace: "default"
  images:
    nodeContainer: "storageos/node:v2.4.4"
  namespace: "storageos"
  # External mTLS secured etcd cluster specific properties
  tlsEtcdSecretRefName: "etcd-client-tls"                                   # Secret containing etcd client certificates
  tlsEtcdSecretRefNamespace: "etcd"                                         # Namespace of the client certificates secret
  kvBackend:
    address: "https://storageos-etcd-cluster-client.storagos-etcd.svc:2379" # Etcd client service address.
    backend: "etcd"                                                         # Backend type

tlsEtcdSecretRefName and tlsEtcdSecretRefNamespace are used to pass a reference to the Secret.

The Ondat operator uses the etcd secret that contains the client certificates, to build a secret in the Ondat installation namespace. This secret contains the certificate filenames and certificate file contents. The Ondat daemonset that is created by the operator mounts the secret as a volume so that the certificate files are available inside the pod. Environment variables containing the file paths are passed to the Ondat process in order to use the files from the mounted path.

A worked example of setting up Ondat with external etcd using mTLS is available here. For ease of use the example uses the CoreOS etcd operator and the CoreOS guide The example uses the CoreOS etcd operator and follows the CoreOS guide for Cluster TLS.