"---
layout: docs
page_title: Configure Certificate Authority (CA) for Consul on Kubernetes
description: >-
  Consul includes a built-in CA, but when bootstrapping a cluster on k8s, you can configure your service mesh to use a custom certificate provider instead. Learn how to configure Vault as an external CA in primary and secondary datacenters and manually rotate Vault tokens.
---"

#  Configure Certificate Authority (CA) for Consul on Kubernetes

~> **NOTE:** The instructions below should only be used for initially bootstrapping a cluster with **Consul K8s 0.38.0+.**
To update the Connect CA provider on an existing cluster or to update any properties, such as tokens, of the CA provider,
please use the [Update CA Configuration Endpoint](/api-docs/connect/ca#update-ca-configuration).

Consul has support for different certificate authority (CA) providers to be used with the Consul Service Mesh.
Please see [Connect Certificate Management](/docs/connect/ca) for the information on the providers
we currently support.

If Connect is enabled, the built-in Consul CA is automatically enabled for the Connect CA.
To configure an external CA provider via the Consul Helm chart, you need to follow three steps:

1. Create a configuration file containing your provider information.
1. Create a Kubernetes secret containing the configuration file.
1. Reference the Kubernetes secret in the [`server.extraVolumes`](/docs/k8s/helm#v-server-extravolumes) value in the Helm chart.

To configure the Vault Connect Provider please see [Vault as the Service Mesh Certificate Provider on Kubernetes](/docs/k8s/deployment-configurations/vault/data-integration/connect-ca).


~> **NOTE:** The following instructions are only valid for Consul-k8s 0.37.0 and prior.

Below we will go over the process for configuring Vault as the Connect CA.
However, other providers can similarly be configured during initial bootstrap of the cluster
by providing the appropriate [`ca_config`] and [`ca_provider`] values for the provider you're using.

## Configuring Vault as a Connect CA (Consul K8s 0.37.0 and earlier)

-> **NOTE:** If using Vault as your Connect CA, it's highly recommended to run a Consul version >= 1.8.5 that supports
token auto-renewal. With this feature, if the Vault token is [renewable](https://www.vaultproject.io/api-docs/auth/token#renewable)
then Consul will automatically renew the token periodically. Without this feature, you
will need to [manually rotate](#manually-rotating-vault-tokens) the Vault
token before it expires.

### Primary Datacenter

To configure Vault as a CA provider for Consul Connect,
first, create a provider configuration JSON file.
Please refer to [Vault as a Connect CA](/docs/connect/ca/vault) for the configuration options.
You will need to provide a Vault token to the `token` property.
Please refer to [these docs](/docs/connect/ca/vault#token) for the permissions that the token needs to have.
This token should be [renewable](https://www.vaultproject.io/api-docs/auth/token#renewable).

To provide a CA, you first need to create a Kubernetes secret containing the CA.
For example, you may create a secret with the Vault CA like so:

```shell-session
kubectl create secret generic vault-ca --from-file vault.ca=/path/to/your/vault/ca
```

And then reference it like this in the provider configuration:

<CodeBlockConfig filename="vault-config.json" highlight="10">

```json
{
  "connect": [
    {
      "ca_config": [
        {
          "address": "https://vault:8200",
          "intermediate_pki_path": "dc1/connect-intermediate",
          "root_pki_path": "connect-root",
          "token": "s.VgQvaXl8xGFO1RUxAPbPbsfN",
          "ca_file": "/consul/userconfig/vault-ca/vault.ca"
        }
      ],
      "ca_provider": "vault"
    }
  ]
}
```

</CodeBlockConfig>

This example configuration file is pointing to a Vault instance running in the same Kubernetes cluster,
which has been deployed with TLS enabled. Note that the `ca_file` is pointing to the file location
based on the Kubernetes secret for the Vault CA that we have created before.
We will provide that secret later in the Helm values for our Consul cluster.

~> NOTE: If you have used Kubernetes CA to sign Vault's certificate,
such as shown in [Standalone Server with TLS](https://www.vaultproject.io/docs/platform/k8s/helm/examples/standalone-tls),
you don't need to create a Kubernetes secret with Vault's CA and can reference the CA directly
by setting `ca_file` to `/var/run/secrets/kubernetes.io/serviceaccount/ca.crt`.

Next, create a Kubernetes secret with this configuration file.

```shell-session
$ kubectl create secret generic vault-config --from-file=config=vault-config.json
```

We will provide this secret and the Vault CA secret, to the Consul server via the
`server.extraVolumes` Helm value.

<CodeBlockConfig filename="values.yaml" highlight="4-13">

  ```yaml
  global:
    name: consul
  server:
    extraVolumes:
      - type: secret
        name: vault-config
        load: true
        items:
          - key: config
            path: vault-config.json
      - type: secret
        name: vault-ca
        load: false
  connectInject:
    enabled: true
  ```

</CodeBlockConfig>

Finally, [install](/docs/k8s/installation/install#installing-consul) the Helm chart using the above config file:

```shell-session
$ helm install consul --values values.yaml hashicorp/consul
```

Verify that the CA provider is set correctly:

```shell-session
$ kubectl exec consul-server-0 -- curl --silent http://localhost:8500/v1/connect/ca/configuration\?pretty
{
  "Provider": "vault",
  "Config": {
    "Address": "https://vault:8200",
    "CAFile": "/consul/userconfig/vault-server-tls/vault.ca",
    "IntermediateCertTTL": "8760h",
    "IntermediatePKIPath": "connect-intermediate",
    "LeafCertTTL": "72h",
    "RootPKIPath": "connect-root",
    "Token": "s.VgQvaXl8xGFO1RUxAPbPbsfN"
  },
  "State": null,
  "ForceWithoutCrossSigning": false,
  "CreateIndex": 5,
  "ModifyIndex": 5
}
```

### Secondary Datacenters

To configure Vault as the Connect CA in secondary datacenters, you need to make sure that the Root CA is the same,
but the intermediate is different for each datacenter. In the `connect` configuration for a secondary datacenter,
you can specify a `intermediate_pki_path` that is, for example, prefixed with the datacenter
for which this configuration is intended.
You will similarly need to create a Vault token and a Kubernetes secret with
Vault's CA in each secondary Kubernetes cluster.

<CodeBlockConfig highlight="7">

```json
{
  "connect": [
    {
      "ca_config": [
        {
          "address": "https://vault:8200",
          "intermediate_pki_path": "dc2/connect-intermediate",
          "root_pki_path": "connect-root",
          "token": "s.VgQvaXl8xGFO1RUxAPbPbsfN",
          "ca_file": "/consul/userconfig/vault-ca/vault.ca"
        }
      ],
      "ca_provider": "vault"
    }
  ]
}
```

</CodeBlockConfig>

Note that all secondary datacenters need to have access to the same Vault instance as the primary.

### Manually Rotating Vault Tokens

If running Consul < 1.8.5 or using a Vault token that is not [renewable](https://www.vaultproject.io/api-docs/auth/token#renewable)
then you will need to manually renew or rotate the Vault token before it expires.

#### Rotating Vault Token

The [`ca_config`] and [`ca_provider`] options defined in the Consul agent
configuration are only used when initially bootstrapping the cluster. Once the
cluster is running, subsequent changes to the [`ca_provider`] config are **ignored**–even if `consul reload` is run or the servers are restarted.

To update any settings under these keys, you must use Consul's [Update CA Configuration](/api-docs/connect/ca#update-ca-configuration) API or the [`consul connect ca set-config`](/commands/connect/ca#set-config) command.

#### Renewing Vault Token

To renew the Vault token, use the [`vault token renew`](https://www.vaultproject.io/docs/commands/token/renew) CLI command
or API.

[`ca_config`]: /docs/agent/config/config-files#connect_ca_config
[`ca_provider`]: /docs/agent/config/config-files#connect_ca_provider
