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04-certificate-authority.md

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Provisioning a CA and Generating TLS Certificates

In this lab you will provision a PKI Infrastructure using CloudFlare's PKI toolkit, cfssl, then use it to bootstrap a Certificate Authority, and generate TLS certificates for the following components: etcd, kube-apiserver, kube-controller-manager, kube-scheduler & kubelet.

The kube-proxy in this lab is replaced by kube-router instead.

Certificate Authority

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

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

{

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

cat > ca-csr.json <<EOF
{
  "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 > admin-csr.json <<EOF
{
  "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 called Node Authorizer, that specifically authorizes API requests made by Kubelets. 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.

The will use the FQDN.

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

DOMAIN="k8s.lan"
for instance in worker-0 worker-1 worker-2; do
cat > ${instance}-csr.json <<EOF
{
  "CN": "system:node:${instance}.${DOMAIN}",
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "system:nodes",
      "OU": "Kubernetes The Hard Way",
      "ST": "Oregon"
    }
  ]
}
EOF

EXTERNAL_IP=$(openstack server show ${instance}.${DOMAIN} -f value -c addresses | awk '{ print $2 }')
INTERNAL_IP=$(openstack server show ${instance}.${DOMAIN} -f value -c addresses | awk -F'[=,]' '{print $2}')

cfssl gencert \
  -ca=ca.pem \
  -ca-key=ca-key.pem \
  -config=ca-config.json \
  -hostname=${instance}.${DOMAIN},${instance},${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 > kube-controller-manager-csr.json <<EOF
{
  "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 Scheduler Client Certificate

Generate the kube-scheduler client certificate and private key:

{

cat > kube-scheduler-csr.json <<EOF
{
  "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=$(openstack server show k8sosp.${DOMAIN} -f value -c addresses | awk '{ print $2 }')
KUBERNETES_HOSTNAMES=kubernetes,kubernetes.default,kubernetes.default.svc,kubernetes.default.svc.cluster,kubernetes.svc.cluster.local

cat > kubernetes-csr.json <<EOF
{
  "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=k8sosp.${DOMAIN},10.240.0.200,10.32.0.1,10.240.0.10,10.240.0.11,10.240.0.12,${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 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 describe in the managing service accounts documentation.

Generate the service-account certificate and private key:

{

cat > service-account-csr.json <<EOF
{
  "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
  scp -i ~/.ssh/k8s.pem ca.pem ${instance}-key.pem ${instance}.pem centos@${instance}.${DOMAIN}:
done

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

for instance in controller-0 controller-1 controller-2; do
  scp -i ~/.ssh/k8s.pem ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
    service-account-key.pem service-account.pem centos@${instance}.${DOMAIN}:
done

The 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