Encrypting communication with Etcd

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

StorageOS uses environment variables to specify the location of the necessary certificates and keys. This allows Kubernetes secrets to be mounted as volumes, directly into pods.

Setting up mTLS with Etcd

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

apiVersion: storageos.com/v1
kind: StorageOSCluster
metadata:
  name: storageos-cluster
  namespace: "default"
spec:
  images:
    nodeContainer: "storageos/node:v2.1.0"
  secretRefName: "storageos-api"
  secretRefNamespace: "default"
  namespace: "storageos"
  csi:
    enable: true
    deploymentStrategy: "deployment"
    enableControllerPublishCreds: true
    enableNodePublishCreds: true
    enableProvisionCreds: true
  # 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.etcd.svc:2379" # Etcd client service address.
    backend: "etcd"                                                # Backend type

tlsEtcdSecretRefName and tlsEtcdSecretRefNamespace are used to pass a reference to a secret that should contain the following key:values:

• etcd-client-ca.crt - containing the etcd Certificate Authority certificate
• etcd-client.crt - containing the etcd Client certificate
• etcd-client.key - cotaining the etcd Client key

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

A worked example of settings up StorageOS with external etcd using mTLS is avaliable here. For ease of use the example uses the CoreOS etcd operator and the CoreOS guide for Cluster TLS is followed.