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Setting up a Certificate Authority and TLS Cert Generation

In this lab you will setup the necessary PKI infrastructure to secure the Kubernetes components. This lab will leverage CloudFlare's PKI toolkit, cfssl, to bootstrap a Certificate Authority and generate TLS certificates.

In this lab you will generate a single set of TLS certificates that can be used to secure the following Kubernetes components:

etcd
Kubernetes API Server
Kubernetes Kubelet

In production you should strongly consider generating individual TLS certificates for each component.

After completing this lab you should have the following TLS keys and certificates:

ca-key.pem
ca.pem
kubernetes-key.pem
kubernetes.pem

Install CFSSL

This lab requires the cfssl and cfssljson binaries. Download them from the cfssl repository.

OS X

wget https://pkg.cfssl.org/R1.2/cfssl_darwin-amd64
chmod +x cfssl_darwin-amd64
sudo mv cfssl_darwin-amd64 /usr/local/bin/cfssl

wget https://pkg.cfssl.org/R1.2/cfssljson_darwin-amd64
chmod +x cfssljson_darwin-amd64
sudo mv cfssljson_darwin-amd64 /usr/local/bin/cfssljson

Linux

wget https://pkg.cfssl.org/R1.2/cfssl_linux-amd64
chmod +x cfssl_linux-amd64
sudo mv cfssl_linux-amd64 /usr/local/bin/cfssl

wget https://pkg.cfssl.org/R1.2/cfssljson_linux-amd64
chmod +x cfssljson_linux-amd64
sudo mv cfssljson_linux-amd64 /usr/local/bin/cfssljson

Setting up a Certificate Authority

Create the CA configuration file

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

Generate the CA certificate and private key

Create the CA CSR:

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

Generate the CA certificate and private key:

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

Results:

ca-key.pem
ca.csr
ca.pem

Verification

openssl x509 -in ca.pem -text -noout

Generate the single Kubernetes TLS Cert

In this section we will generate a TLS certificate that will be valid for all Kubernetes components. This is being done for ease of use. In production you should strongly consider generating individual TLS certificates for each component. (But all replicas of a given component must share the same certificate.)

Set the Kubernetes Public Address

GCE

KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes \
  --format 'value(address)')

AWS

KUBERNETES_PUBLIC_ADDRESS=$(aws elb describe-load-balancers \
  --load-balancer-name kubernetes | \
  jq -r '.LoadBalancerDescriptions[].DNSName')

Create the admin-csr.json file:

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

Generate the admin certificate and private key:

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.csr
admin.pem

Create the kubernetes-csr.json file:

cat > kubernetes-csr.json <<EOF
{
  "CN": "kubernetes",
  "hosts": [
    "10.32.0.1",
    "10.240.0.10",
    "10.240.0.11",
    "10.240.0.12",
    "ip-10-240-0-20",
    "ip-10-240-0-21",
    "ip-10-240-0-22",
    "${KUBERNETES_PUBLIC_ADDRESS}",
    "127.0.0.1",
    "kubernetes.default"
  ],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "Kubernetes",
      "OU": "Cluster",
      "ST": "Oregon"
    }
  ]
}
EOF

Generate the Kubernetes certificate and private key:

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

Results:

kubernetes-key.pem
kubernetes.csr
kubernetes.pem

Verification

openssl x509 -in kubernetes.pem -text -noout

Copy TLS Certs

Set the list of Kubernetes hosts where the certs should be copied to:

KUBERNETES_HOSTS=(controller0 controller1 controller2 worker0 worker1 worker2)

KUBERNETES_CONTROLLERS=(controller0 controller1 controller2)

GCE

The following command will:

Copy the TLS certificates and keys to each Kubernetes host using the gcloud compute copy-files command.

for host in ${KUBERNETES_HOSTS[*]}; do
  gcloud compute copy-files ca.pem ${host}:~/
done

for host in ${KUBERNETES_CONTROLLERS[*]}; do
  gcloud compute copy-files ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem ${host}:~/
done

AWS

The following command will:

Extract the public IP address for each Kubernetes host
Copy the TLS certificates and keys to each Kubernetes host using scp

for host in ${KUBERNETES_HOSTS[*]}; do
  PUBLIC_IP_ADDRESS=$(aws ec2 describe-instances \
    --filters "Name=tag:Name,Values=${host}" | \
    jq -r '.Reservations[].Instances[].PublicIpAddress')
  scp -o "StrictHostKeyChecking no" ca.pem \
    ubuntu@${PUBLIC_IP_ADDRESS}:~/
done

for host in ${KUBERNETES_HOSTS[*]}; do
  PUBLIC_IP_ADDRESS=$(aws ec2 describe-instances \
    --filters "Name=tag:Name,Values=${host}" | \
    jq -r '.Reservations[].Instances[].PublicIpAddress')
  scp -o "StrictHostKeyChecking no" ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
    ubuntu@${PUBLIC_IP_ADDRESS}:~/
done