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02-certificate-authority.md

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Setting up a Certificate Authority and Creating TLS Certificates

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 to secure the following Kubernetes components:

  • etcd
  • kube-apiserver
  • kubelet
  • kube-proxy

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

admin.pem
admin-key.pem
ca-key.pem
ca.pem
kubelet.pem
kubelet-key.pem
kubernetes-key.pem
kubernetes.pem
kube-proxy.pem
kube-proxy-key.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

Note: On CoreOS the above directory is read only, therefore you might want to use a different path.

sudo mkdir -p /opt/bin/
sudo mv cfssljson_linux-amd64 cfssl_linux-amd64 /opt/bin/
export PATH=$PATH:/opt/bin

Set up a Certificate Authority

Create a CA configuration file:

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

Create a CA certificate signing request:

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

Generate a CA certificate and private key:

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

Results:

ca-key.pem
ca.pem

Generate client and server TLS certificates

In this section we will generate TLS certificates for each Kubernetes component and a client certificate for the admin user.

Create the Admin client certificate

Create the admin client certificate signing request:

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

Generate the admin client 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.pem

Create the kubelet client certificate

Create the kubelet client certificate signing request:

cat > kubelet-csr.json <<EOF
{
  "CN": "system:node:kubelet",
  "hosts": [],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "DE",
      "L": "Berlin",
      "O": "system:nodes",
      "OU": "Cluster",
      "ST": "Berlin"
    }
  ]
}
EOF

Generate the kube-proxy client certificate and private key:

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

Results:

kubelet-key.pem
kubelet.pem

Create the kube-proxy client certificate

Create the kube-proxy client certificate signing request:

cat > kube-proxy-csr.json <<EOF
{
  "CN": "system:kube-proxy",
  "hosts": [],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "DE",
      "L": "Berlin",
      "O": "system:node-proxier",
      "OU": "Cluster",
      "ST": "Berlin"
    }
  ]
}
EOF

Generate the kube-proxy client certificate and private key:

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

Create the kubernetes server certificate

The Kubernetes public IP address will be included in the list of subject alternative names for the Kubernetes server certificate. This will ensure the TLS certificate is valid for remote client access.

Create the Kubernetes server certificate signing request:

cat > kubernetes-csr.json <<EOF
{
  "CN": "kubernetes",
  "hosts": [
    "10.180.1.1",
    "10.180.0.100",
    "10.180.0.101",
    "10.180.0.102",
    "10.180.0.200",
    "10.180.0.201",
    "10.180.0.202",
    "${KUBERNETES_PUBLIC_ADDRESS}",
    "127.0.0.1",
    "localhost",
    "kubernetes.default",
    "master0",
    "master1",
    "master2",
    "minion0",
    "minion1",
    "minion2"
  ],
  "key": {
    "algo": "rsa",
    "size": 2048
  },
  "names": [
    {
      "C": "DE",
      "L": "Berlin",
      "O": "Kubernetes",
      "OU": "Cluster",
      "ST": "Berlin"
    }
  ]
}
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.pem

Distribute the TLS certificates

The following commands will copy the TLS certificates and keys to each Kubernetes host using the gateway we created.

scp -oProxyJump=core@$GATEWAY:22 ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem kubelet.pem kubelet-key.pem [email protected]:~/
scp -oProxyJump=core@$GATEWAY:22 ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem kubelet.pem kubelet-key.pem [email protected]:~/
scp -oProxyJump=core@$GATEWAY:22 ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem kubelet.pem kubelet-key.pem [email protected]:~/
scp -oProxyJump=core@$GATEWAY:22 ca.pem kubernetes-key.pem kubernetes.pem kube-proxy.pem kube-proxy-key.pem [email protected]:~/
scp -oProxyJump=core@$GATEWAY:22 ca.pem kubernetes-key.pem kubernetes.pem kube-proxy.pem kube-proxy-key.pem [email protected]:~/
scp -oProxyJump=core@$GATEWAY:22 ca.pem kubernetes-key.pem kubernetes.pem kube-proxy.pem kube-proxy-key.pem [email protected]:~/