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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.

This lab will setup a Certificate Authority and 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

Follow the CFSSL installation guide and install cfssl and cfssljson binaries.

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.

echo '{
  "CN": "kubernetes",
  "hosts": [
    "10.240.0.10",
    "10.240.0.11",
    "10.240.0.12",
    "10.240.0.20",
    "10.240.0.21",
    "10.240.0.22",
    "10.240.0.30",
    "10.240.0.31",
    "10.240.0.32",
    "146.148.34.151",
    "127.0.0.1"
  ],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "US",
      "L": "Portland",
      "O": "Kubernetes",
      "OU": "Cluster",
      "ST": "Oregon"
    }
  ]
}' > kubernetes-csr.json

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