kubernetes-the-hard-way/docs/04-certificate-authority.md

# Provisioning a CA and Generating TLS Certificates

In this lab you will provision a [public key infrastructure (PKI)](https://en.wikipedia.org/wiki/Public_key_infrastructure) using [CloudFlare's PKI/TLS toolkit](https://github.com/cloudflare/cfssl), then use it to bootstrap a Certificate Authority (CA), and generate TLS certificates for the following components: etcd, kube-apiserver, kube-controller-manager, kube-scheduler, kubelet, and kube-proxy.

## Certificate Authority

In this section you will provision a CA that can be used to generate additional TLS certificates.

Generate the CA configuration file, certificate, and private key:

```
cat <<EOF >ca-config.json
{
  "signing": {
    "default": {
      "expiry": "8760h"
    },
    "profiles": {
      "kubernetes": {
        "usages": ["signing", "key encipherment", "server auth", "client auth"],
        "expiry": "8760h"
      }
    }
  }
}
EOF

cat <<EOF >ca-csr.json
{
  "CN": "Kubernetes",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "Kubernetes",
      "OU": "CA",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert -initca ca-csr.json \
  | cfssljson -bare ca
```

Results:

```
ca-key.pem
ca.pem
```

## Client and Server Certificates

In this section you will generate client and server certificates for each Kubernetes component and a client certificate for the Kubernetes `admin` user.

### The Admin Client Certificate

Generate the `admin` client certificate and private key:

```
cat <<EOF >admin-csr.json
{
  "CN": "admin",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:masters",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -profile kubernetes \
  admin-csr.json \
  | cfssljson -bare admin
```

Results:

```
admin-key.pem
admin.pem
```

### The Kubelet Client Certificates

Kubernetes uses a [special-purpose authorization mode](https://kubernetes.io/docs/reference/access-authn-authz/node/) called Node Authorizer, that specifically authorizes API requests made by [Kubelets](https://kubernetes.io/docs/concepts/overview/components/#kubelet). In order to be authorized by the Node Authorizer, Kubelets must use a credential that identifies them as being in the `system:nodes` group, with a username of `system:node:<nodeName>`. In this section you will create a certificate for each Kubernetes worker node that meets the Node Authorizer requirements.

Generate a certificate and private key for each Kubernetes worker node:

```
for instance in worker-0 worker-1 worker-2; do
  cat <<EOF >"${instance}-csr.json"
{
  "CN": "system:node:${instance}",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:nodes",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

  EXTERNAL_IP="$(gcloud compute instances describe ${instance} \
    --format 'value(networkInterfaces[0].accessConfigs[0].natIP)')"

  INTERNAL_IP="$(gcloud compute instances describe ${instance} \
    --format 'value(networkInterfaces[0].networkIP)')"

  cfssl gencert \
    -ca ca.pem \
    -ca-key ca-key.pem \
    -config ca-config.json \
    -hostname "${instance},${EXTERNAL_IP},${INTERNAL_IP}" \
    -profile kubernetes \
    "${instance}-csr.json" \
    | cfssljson -bare "${instance}"
done
```

Results:

```
worker-0-key.pem
worker-0.pem
worker-1-key.pem
worker-1.pem
worker-2-key.pem
worker-2.pem
```

### The Controller Manager Client Certificate

Generate the `kube-controller-manager` client certificate and private key:

```
cat <<EOF >kube-controller-manager-csr.json
{
  "CN": "system:kube-controller-manager",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:kube-controller-manager",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -profile kubernetes \
  kube-controller-manager-csr.json \
  | cfssljson -bare kube-controller-manager
```

Results:

```
kube-controller-manager-key.pem
kube-controller-manager.pem
```

### The Kube Proxy Client Certificate

Generate the `kube-proxy` client certificate and private key:

```
cat <<EOF >kube-proxy-csr.json
{
  "CN": "system:kube-proxy",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:node-proxier",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -profile kubernetes \
  kube-proxy-csr.json \
  | cfssljson -bare kube-proxy
```

Results:

```
kube-proxy-key.pem
kube-proxy.pem
```

### The Scheduler Client Certificate

Generate the `kube-scheduler` client certificate and private key:

```
cat <<EOF >kube-scheduler-csr.json
{
  "CN": "system:kube-scheduler",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:kube-scheduler",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -profile kubernetes \
  kube-scheduler-csr.json \
  | cfssljson -bare kube-scheduler
```

Results:

```
kube-scheduler-key.pem
kube-scheduler.pem
```

### The Kubernetes API Server Certificate

The `kubernetes-the-hard-way` static IP address will be included in the list of subject alternative names for the Kubernetes API Server certificate. This will ensure the certificate can be validated by remote clients.

Generate the Kubernetes API Server certificate and private key:

```
KUBERNETES_PUBLIC_ADDRESS="$(gcloud compute addresses describe kubernetes-the-hard-way \
  --format 'value(address)')"

KUBERNETES_HOSTNAMES='kubernetes,kubernetes.default,kubernetes.default.svc,kubernetes.default.svc.cluster,kubernetes.svc.cluster.local'

cat <<EOF >kubernetes-csr.json
{
  "CN": "kubernetes",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "Kubernetes",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -hostname "10.32.0.1,10.240.0.10,10.240.0.11,10.240.0.12,${KUBERNETES_PUBLIC_ADDRESS},127.0.0.1,${KUBERNETES_HOSTNAMES}" \
  -profile kubernetes \
  kubernetes-csr.json \
  | cfssljson -bare kubernetes
```

> The Kubernetes API server is automatically assigned the `kubernetes` internal dns name, which will be linked to the first IP address (`10.32.0.1`) from the address range (`10.32.0.0/24`) reserved for internal cluster services during the [control plane bootstrapping](08-bootstrapping-kubernetes-controllers.md#configure-the-kubernetes-api-server) lab.

Results:

```
kubernetes-key.pem
kubernetes.pem
```

## The Service Account Key Pair

The Kubernetes Controller Manager leverages a key pair to generate and sign service account tokens as described in the [managing service accounts](https://kubernetes.io/docs/reference/access-authn-authz/service-accounts-admin/) documentation.

Generate the `service-account` certificate and private key:

```
cat <<EOF >service-account-csr.json
{
  "CN": "service-accounts",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "Kubernetes",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

cfssl gencert \
  -ca ca.pem \
  -ca-key ca-key.pem \
  -config ca-config.json \
  -profile kubernetes \
  service-account-csr.json \
  | cfssljson -bare service-account
```

Results:

```
service-account-key.pem
service-account.pem
```

## Distribute the Client and Server Certificates

Copy the appropriate certificates and private keys to each worker instance:

```
for instance in worker-0 worker-1 worker-2; do
  gcloud compute scp \
    ca.pem \
    "${instance}-key.pem" "${instance}.pem" \
    "${instance}:"
done
```

Copy the appropriate certificates and private keys to each controller instance:

```
for instance in controller-0 controller-1 controller-2; do
  gcloud compute scp \
    ca-key.pem ca.pem \
    kubernetes-key.pem kubernetes.pem \
    service-account-key.pem service-account.pem \
    "${instance}:"
done
```

> The `kube-proxy`, `kube-controller-manager`, `kube-scheduler`, and `kubelet` client certificates will be used to generate client authentication configuration files in the next lab.

Next: [Generating Kubernetes Configuration Files for Authentication](./05-kubernetes-configuration-files.md)