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Installation Guide
Cert-Manager is a native Kubernetes certificate management controller. It can help with issuing certificates from a variety of sources, such as Let’s Encrypt, HashiCorp Vault, Venafi, a simple signing key pair, or self signed. It will ensure certificates are valid and up to date, and attempt to renew certificates at a configured time before expiry.
The Kubespray out-of-the-box cert-manager deployment uses a TLS Root CA certificate and key stored as the Kubernetes ca-key-pair secret consisting of tls.crt and tls.key, which are the base64 encode values of the TLS Root CA certificate and key respectively.
Integration with other PKI/Certificate management solutions, such as HashiCorp Vault will require some further development changes to the current cert-manager deployment and may be introduced in the future.
Kubernetes TLS Root CA Certificate/Key Secret
If you're planning to secure your ingress resources using TLS client certificates, you'll need to create and deploy the Kubernetes ca-key-pair secret consisting of the Root CA certificate and key to your K8s cluster.
If these are already available, simply update templates\secret-cert-manager.yml.j2 with the base64 encoded values of your TLS Root CA certificate and key prior to enabling and deploying cert-manager.
e.g.
$ cat ca.pem | base64 -w 0
LS0tLS1CRUdJTiBDRVJU...
$ cat ca-key.pem | base64 -w 0
LS0tLS1CRUdJTiBSU0Eg...
For further information, read the official Cert-Manager CA Configuration doc.
Once the base64 encoded values have been added to templates\secret-cert-manager.yml.j2, cert-manager can now be enabled by editing your K8s cluster addons inventory e.g. inventory\sample\group_vars\k8s-cluster\addons.yml and setting cert_manager_enabled to true.
# Cert manager deployment
cert_manager_enabled: true
If you don't have a TLS Root CA certificate and key available, you can create these by following the steps outlined in section Create New TLS Root CA Certificate and Key using the Cloudflare PKI/TLS cfssl toolkit. TLS Root CA certificates and keys can also be created using ssh-keygen and OpenSSL, if cfssl is not available.
Securing Ingress Resources
A common use-case for cert-manager is requesting TLS signed certificates to secure your ingress resources. This can be done by simply adding annotations to your Ingress resources and cert-manager will facilitate creating the Certificate resource for you. A small sub-component of cert-manager, ingress-shim, is responsible for this.
To enable the Nginx Ingress controller as part of your Kubespray deployment, simply edit your K8s cluster addons inventory e.g. inventory\sample\group_vars\k8s-cluster\addons.yml and set ingress_nginx_enabled to true.
# Nginx ingress controller deployment
ingress_nginx_enabled: true
For example, if you're using the Nginx ingress controller, you can secure the Prometheus ingress by adding the annotation cert-manager.io/cluster-issuer: ca-issuer and the spec.tls section to the Ingress resource definition.
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: prometheus-k8s
namespace: monitoring
labels:
prometheus: k8s
annotations:
kubernetes.io/ingress.class: "nginx"
cert-manager.io/cluster-issuer: ca-issuer
spec:
tls:
- hosts:
- prometheus.example.com
secretName: prometheus-dashboard-certs
rules:
- host: prometheus.example.com
http:
paths:
- path: /
backend:
serviceName: prometheus-k8s
servicePort: web
Once deployed to your K8s cluster, every 3 months cert-manager will automatically rotate the Prometheus prometheus.example.com TLS client certificate and key, and store these as the Kubernetes prometheus-dashboard-certs secret.
For further information, read the official Cert-Manager Ingress doc.
Create New TLS Root CA Certificate and Key
Install Cloudflare PKI/TLS cfssl Toolkit.
e.g. For Ubuntu/Debian distibutions, the toolkit is part of the golang-cfssl package.
$ sudo apt-get install -y golang-cfssl
Create Root Certificate Authority (CA) Configuration File
The default TLS certificate expiry time period is 8760h which is 5 years from the date the certificate is created.
$ cat > ca-config.json <<EOF
{
"signing": {
"default": {
"expiry": "8760h"
},
"profiles": {
"kubernetes": {
"usages": ["signing", "key encipherment", "server auth", "client auth"],
"expiry": "8760h"
}
}
}
}
EOF
Create Certficate Signing Request (CSR) Configuration File
The TLS certificate names details can be updated to your own specific requirements.
$ cat > ca-csr.json <<EOF
{
"CN": "Kubernetes",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "Kubernetes",
"OU": "CA",
"ST": "Oregon"
}
]
}
EOF
Create TLS Root CA Certificate and Key
$ cfssl gencert -initca ca-csr.json | cfssljson -bare ca
ca.pem
ca-key.pem
Check the TLS Root CA certificate has the correct Not Before and Not After dates, and ensure it is indeed a valid Certificate Authority with the X509v3 extension CA:TRUE.
$ openssl x509 -text -noout -in ca.pem
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
6a:d4:d8:48:7f:98:4f:54:68:9a:e1:73:02:fa:d0:41:79:25:08:49
Signature Algorithm: sha256WithRSAEncryption
Issuer: C = US, ST = Oregon, L = Portland, O = Kubernetes, OU = CA, CN = Kubernetes
Validity
Not Before: Jul 10 15:21:00 2020 GMT
Not After : Jul 9 15:21:00 2025 GMT
Subject: C = US, ST = Oregon, L = Portland, O = Kubernetes, OU = CA, CN = Kubernetes
Subject Public Key Info:
...
X509v3 extensions:
X509v3 Key Usage: critical
Certificate Sign, CRL Sign
X509v3 Basic Constraints: critical
CA:TRUE
X509v3 Subject Key Identifier:
D4:38:B5:E2:26:49:5E:0D:E3:DC:D9:70:73:3B:C4:19:6A:43:4A:F2
...