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cluster_tls.md

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Cluster TLS policy

Cluster TLS policy is configured on a per-cluster basis through the CR spec provided to etcd operator.

For etcd's TLS support and requirements, see the etcd security model. To learn about generating self-signed TLS certs, see Generate self-signed certificates.

Static cluster TLS policy

Static TLS means keys/certs are generated by the user and passed to an operator.

This section will use the following YAML manifest to describe the spec. The example cluster manifest and certs can be found in the example/tls/ directory.

apiVersion: "etcd.database.coreos.com/v1beta2"
kind: "EtcdCluster"
metadata:
  name: example
  namespace: default
spec:
  ...
  TLS:
    static:
      member:
        peerSecret: etcd-peer-tls
        serverSecret: etcd-server-tls
      operatorSecret: etcd-client-tls

member.peerSecret

member.peerSecret contains pem-encoded private keys and x509 certificates for etcd peer communication.

The peer TLS assets should have the following:

  • peer.crt: peer communication cert. The certificate should allow wildcard domain *.${clusterName}.${namespace}.svc and *.${clusterName}.${namespace}.svc.${cluster_domain}. The example shown above uses *.example.default.svc and *.example.default.svc.cluster.local.
  • peer.key: peer communication key.
  • peer-ca.crt: CA cert for this peer key-cert pair.

Create a secret using the peer.key, peer.crt, and peer-ca.crt:

$ kubectl create secret generic etcd-peer-tls --from-file=peer-ca.crt --from-file=peer.crt --from-file=peer.key

Once passed, etcd operator will mount this secret at /etc/etcdtls/member/peer-tls/ for each etcd member pod in the cluster.

member.serverSecret

member.serverSecret contains pem-encoded private keys and x509 certificates for etcd client communication on server side.

The client TLS assets should have the following:

  • server.crt: etcd server's client communication cert. The certificate should allow wildcard domain *.${clusterName}.${namespace}.svc, ${clusterName}-client.${namespace}.svc, and localhost. The example shown above uses *.example.default.svc, example-client.default.svc, and localhost. To use more DNS name or IP to access etcd server, please add it here.
  • server.key: etcd server's client communication key.
  • server-ca.crt: CA cert for validating the certs of etcd clients.

Create a secret using server.key, server.crt, and server-ca.crt:

$ kubectl create secret generic etcd-server-tls --from-file=server-ca.crt --from-file=server.crt --from-file=server.key

etcd operator will mount this secret at /etc/etcdtls/member/server-tls/ for each etcd member pod in the cluster.

operatorSecret

The operator must send client requests (such as snapshot, healthy check, add/remove member) to maintain this cluster.

operatorSecret contains pem-encoded private keys and x509 certificates for communicating with etcd server via client URL.

The operator's etcd TLS assets should have the following:

  • etcd-client.crt: operator's etcd x509 client cert.
  • etcd-client.key: operator's etcd x509 client key.
  • etcd-client-ca.crt: CA cert for validating the certs of etcd members. They correspond to the --cert,--key, and --cacert arguments of etcdctl.

Create a secret containing the etcd-client.crt, etcd-client.key, and etcd-client-ca.crt:

$ kubectl create secret generic etcd-client-tls --from-file=etcd-client-ca.crt --from-file=etcd-client.crt --from-file=etcd-client.key

Pass etcd-client-tls to the operatorSecret field.

Access a secure etcd cluster

Assume a secure etcd cluster example is up and running.

To access the cluster, use the service example-client.default.svc, which matches the SAN of its certificates.

Assume the following certs are used:

etcd-client.crt
etcd-client.key
etcd-client-ca.crt

etcd-client.crt and etcd-client.key should be trusted by the etcd server's client CA server-ca.crt.

server.crt and server.key should be trusted by the etcd client CA etcd-client-ca.crt.

The following example etcdctl command will list members from the secure etcd cluster. Run this command from within a Kubernetes Pod to access the service name:

$ ETCDCTL_API=3 etcdctl --endpoints=https://example-client.default.svc:2379 \
    --cert=etcd-client.crt --key=etcd-client.key --cacert=etcd-client-ca.crt \
    member list -w table