---
layout: 'docs'
page_title: 'Vault Agent Injector TLS with Cert-Manager'
sidebar_current: 'docs-platform-k8s-examples-injector-tls-cert-manager'
description: |-
  Describes how to set up the Vault Agent Injector with certificates and keys generated by cert-manager.
---

# Vault agent injector TLS with Cert-Manager

The following instructions demonstrate how to configure the Vault Agent Injector to use certificates generated by [cert-manager](https://cert-manager.io/). This allows you to run multiple replicas of the Vault Agent Injector in a Kubernetes cluster.

## Prerequisites

Install cert-manager if not already installed (see the [cert-manager documentation](https://cert-manager.io/docs/installation/)). For example, with helm:

```shell
$ helm repo add jetstack https://charts.jetstack.io
$ helm repo update
$ helm install cert-manager jetstack/cert-manager \
  --namespace cert-manager \
  --create-namespace \
  --set installCRDs=true
```

## Create a certificate authority (CA)

For this example we will bootstrap a self-signed certificate authority (CA) [Issuer](https://cert-manager.io/docs/configuration/). If you already have a [ClusterIssuer](https://cert-manager.io/docs/concepts/issuer/) configured for your cluster, you may skip this step.

```yaml
apiVersion: cert-manager.io/v1
kind: Issuer
metadata:
  name: selfsigned
spec:
  selfSigned: {}
---
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: injector-selfsigned-ca
spec:
  isCA: true
  commonName: Agent Inject CA
  secretName: injector-ca-secret
  duration: 87660h  # 10 years
  privateKey:
    algorithm: ECDSA
    size: 256
  issuerRef:
    name: selfsigned
    kind: Issuer
    group: cert-manager.io
---
apiVersion: cert-manager.io/v1
kind: Issuer
metadata:
  name: injector-ca-issuer
spec:
  ca:
    secretName: injector-ca-secret
```

Save that to a file named `ca-issuer.yaml`, and apply to your Kubernetes cluster:

```console
$ kubectl apply -n vault -f ca-issuer.yaml
issuer.cert-manager.io/selfsigned created
certificate.cert-manager.io/injector-selfsigned-ca created
issuer.cert-manager.io/injector-ca-issuer created

$ kubectl -n vault get issuers -o wide
NAME                 READY   STATUS                AGE
injector-ca-issuer   True    Signing CA verified   7s
selfsigned           True                          7s

$ kubectl -n vault get certificates injector-selfsigned-ca -o wide
NAME                     READY   SECRET               ISSUER       STATUS                                          AGE
injector-selfsigned-ca   True    injector-ca-secret   selfsigned   Certificate is up to date and has not expired   32s
```

## Create the Vault agent injector certificate

Next we can create a request for cert-manager to generate a certificate and key
signed by the certificate authority above. This certificate and key will be used
by the Vault Agent Injector for TLS communications with the Kubernetes API. 

The Certificate request object references the CA issuer created above, and specifies the name of the Secret where the CA, Certificate, and Key will be stored by cert-manager.

```yaml
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: injector-certificate
spec:
  secretName: injector-tls
  duration: 24h
  renewBefore: 144m  # roughly 10% of 24h
  dnsNames:
  - vault-agent-injector-svc
  - vault-agent-injector-svc.vault
  - vault-agent-injector-svc.vault.svc
  issuerRef:
    name: injector-ca-issuer
  commonName: Agent Inject Cert
```

~> **Important Note:** The dnsNames for the certificate must be configured to use the name
of the Vault Agent Injector Kubernetes service and namespace where it is deployed.

In this example the Vault Agent Injector service name is `vault-agent-injector-svc` in the `vault` namespace.
This uses the pattern `<k8s service name>.<k8s namespace>.svc`.

Save the Certificate yaml to a file and apply to your cluster:

```shell
$ kubectl -n vault apply -f injector-certificate.yaml
certificate.cert-manager.io/injector-certificate created

$ kubectl -n vault get certificates injector-certificate -o wide
NAME                   READY   SECRET         ISSUER               STATUS                                          AGE
injector-certificate   True    injector-tls   injector-ca-issuer   Certificate is up to date and has not expired   41s

$ kubectl -n vault get secret injector-tls
NAME           TYPE                DATA   AGE
injector-tls   kubernetes.io/tls   3      6m59s
```

## Configuration

Now that a certificate authority and a signed certificate have been created, we can now configure
Helm and the Vault Agent Injector to use them.

Install the Vault Agent Injector with the following custom values:

```shell
$ helm install vault hashicorp/vault \
  --namespace=vault \
  --set injector.replicas=2 \
  --set injector.leaderElector.enabled=false \
  --set injector.certs.secretName=injector-tls \
  --set injector.webhook.annotations="cert-manager.io/inject-ca-from: {{ .Release.Namespace }}/injector-certificate"
```
