Setting up TLS for Vault

This document describes the two methods to configure TLS on the Vault servers for a Vault cluster.

Using the default TLS assets

If the TLS assets for a cluster are not specified using the custom resource (CR) specification field, spec.TLS, the operator creates a default CA and uses it to generate self-signed certificates for the Vault servers in the cluster.

These default TLS assets are stored in the following secrets:

<vault-cluster-name>-default-vault-client-tls: This secret contains the vault-client-ca.crt file, which is the CA certificate used to sign the Vault server certificate. This CA can be used by the Vault clients to authenticate the certificate presented by the Vault server.
<vault-cluster-name>-default-vault-server-tls: This secret contains the server.crt and server.key files. These are the TLS certificate and key used to configure TLS on the Vault servers.

For example, create a Vault cluster with no TLS secrets specified using the following specification:

apiVersion: "vault.security.coreos.com/v1alpha1"
kind: "VaultService"
metadata:
  name: example
spec:
  nodes: 1

The following default secrets are generated for the above Vault cluster:

$ kubectl get secrets
NAME                                        TYPE                                  DATA      AGE
example-default-vault-client-tls      Opaque                                1         1m
example-default-vault-server-tls      Opaque                                2         1m

Using custom TLS assets

Users may pass in custom TLS assets while creating a cluster. Specify the client and server secrets in the following CR specification fields:

spec.TLS.static.clientSecret: This secret contains the vault-client-ca.crt file, which is the CA certificate used to sign the Vault server certificate. This CA can be used by the Vault clients to authenticate the certificate presented by the Vault server.
spec.TLS.static.serverSecret: This secret contains the server.crt and server.key files. These are the TLS certificate and key for the Vault server. The server.crt certificate allows the following wildcard domains:
- localhost
- *.<namespace>.pod
- <vault-cluster-name>.<namespace>.svc

The final CR specification is given below:

apiVersion: "vault.security.coreos.com/v1alpha1"
kind: "VaultService"
metadata:
  name: <vault-cluster-name>
spec:
  nodes: 1
  TLS:
    static:
      serverSecret: <server-secret-name>
      clientSecret: <client-secret-name>

Generating TLS assets

Use the hack/tls-gen.sh script to generate the necessary TLS assets and bundle them into required secrets.

Prerequisites

kubectl installed
cfssl tools installed
jq tool installed

Using tls-gen script

Run the following command by providing the environment variable values as necessary:

$ KUBE_NS=<namespace> SERVER_SECRET=<server-secret-name> CLIENT_SECRET=<client-secret-name> hack/tls-gen.sh

Successful execution generates the required secrets in the desired namespace.

For example:

$ KUBE_NS=default SERVER_SECRET=vault-server-tls CLIENT_SECRET=vault-client-tls hack/tls-gen.sh
$ kubectl -n default get secrets
NAME                  TYPE                                  DATA      AGE
vault-client-tls      Opaque                                1         1m
vault-server-tls      Opaque                                2         1m

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