consul/website/content/docs/k8s/installation/vault/server-tls.mdx

---
layout: docs
page_title: Storing Server TLS certificates in Vault
description: >-
  Configuring the Consul Helm chart to use TLS certificates issued by Vault for the Consul server.
---

# Storing Server TLS certificates in Vault

To use Vault to issue Server TLS certificates the following will be needed:

1. Bootstrap the Vault PKI engine and boostrap it with any configuration required for your infrastructure.
1. Create Vault Policies that will allow the Consul server to access the certificate issuing url.
1. Create Vault Policies that will allow the Consul components, e.g. ingress gateways, controller, to access the CA url.
1. Create Kubernetes auth roles that link these policies to the Kubernetes service accounts of the Consul components.


### Bootstrapping the PKI Engine
First, we need to bootstrap the Vault cluster by enabling and configuring the PKI Secrets Engine to be able to serve
TLS certificates to Consul. The process can be as simple as the following, or more complicated such as in this [example](https://learn.hashicorp.com/tutorials/consul/vault-pki-consul-secure-tls)
which also uses an intermediate signing authority.

* Enable the PKI Secrets Engine:
```shell-session
vault secrets enable pki
```
* Tune the engine to enable longer TTL:
```shell-session
vault secrets tune -max-lease-ttl=87600h pki
```
* Generate the root CA
```shell-session
vault write -field=certificate pki/root/generate/internal \
        common_name="dc1.consul" \
        ttl=87600h
```
-> **Note:** Where `common_name` is comprised of combining `global.datacenter` dot `global.domain`.

### Create Vault Policies for the Server TLS Certificates

Next we will create a policy that allows `["create", "update"]` access to the
[certificate issuing URL](https://www.vaultproject.io/api/secret/pki#generate-certificate) so the Consul servers can
fetch a new certificate/key pair.

```shell-session
# consul-server-policy.hcl
path "pki/issue/consul-server" {
  capabilities = ["create", "update"]
}
```

```shell-session
vault policy write consul-server consul-server-policy.hcl
```
-> **Note:** The PKI secret path referenced by the above Policy will be your `server.serverCert.secretName` Helm value.

### Create Vault Policies for the CA URL

Next, we will create a policy that allows `["read"]` access to the [CA URL](https://www.vaultproject.io/api/secret/pki#read-certificate),
this is required for the Consul components to communicate with the Consul servers in order to fetch their auto-encryption certificates.

```shell-session
# ca-policy.hcl
path "pki/cert/ca" {
  capabilities = ["read"]
}
```

```shell-session
vault policy write ca-policy ca-policy.hcl
```
-> **Note:** The PKI secret path referenced by the above Policy will be your `global.tls.caCert.secretName` Helm value.

### Create Vault Roles for the PKI engine, Consul servers and components

Next, a Vault role for the PKI engine will set the default certificate issuance parameters:

```shell-session
vault write pki/roles/consul-server \
  allowed_domains="<Allowed-domains-string>" \
  allow_subdomains=true \
  allow_bare_domains=true \
  allow_localhost=true \
  generate_lease=true \
  max_ttl="720h"
```

To generate the `<Allowed-domains-string>` use the following script as a template:

```shell-session
#!/bin/sh

# NAME is set to either the value from `global.name` from your Consul K8s value file, or your $HELM_RELEASE_NAME-consul
export NAME=consulk8s
# NAMESPACE is where the Consul on Kubernetes is installed
export NAMESPACE=consul
# DATACENTER is the value of `global.datacenter` from your Helm values config file
export DATACENTER=dc1

echo allowed_domains=\"$DATACENTER.consul, $NAME-server, $NAME-server.$NAMESPACE, $NAME-server.$NAMESPACE.svc\"
```

Prior to creating the Kubernetes auth roles required for Consul to securely access Vault, ensure that the Vault Kubernetes Auth method is enabled:

```shell-session
vault auth enable kubernetes
```

Finally, two Kubernetes auth roles need to be created, one for the Consul servers and one for the Consul components:

```shell-session
vault write auth/kubernetes/role/consul-server \
    bound_service_account_names=<Consul server service account> \
    bound_service_account_namespaces=<Consul installation namespace> \
    policies=consul-server \
    ttl=1h
```

To find out the service account name of the Consul server,
you can run:
```shell-session
 helm template --release-name <your release name> -s templates/server-serviceaccount.yaml hashicorp/consul
```

-> **Note:** Should you enable other supported features such as gossip-encryption be sure to append additional policies to
the Kube auth role in a comma separated value e.g.  `policies=consul-server,consul-gossip`

```shell-session
vault write auth/kubernetes/role/consul-ca \
    bound_service_account_names="*" \
    bound_service_account_namespaces=<Consul installation namespace> \
    policies=consul-ca \
    ttl=1h
```

The above Vault Roles will now be your Helm values for `global.secretsBackend.vault.consulServerRole` and
`global.secretsBAckend.vault.consulCARole` respectively.


## Deploying the Consul Helm chart

Now that we've configured Vault, you can configure the Consul Helm chart to
use the Server TLS certificates from Vault:

```yaml
global:
  secretsBackend:
    vault:
      enabled: true
      consulServerRole: consul-server
      consulClientRole: consul-client
      consulCARole: consul-ca
  tls:
    enabled: true
    caCert:
      secretName: "pki/cert/ca"
server:
  serverCert:
    secretName: "pki/issue/consul-server"
  extraVolumes:
  - type: "secret"
    name: <vaultCASecret>
    load: "false"
```

The `vaultCASecret` is the Kubernetes secret that stores the CA Certificate that is used for Vault communication. 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:

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