Issue with Auto Approve Certificate signing request

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Cluster information:

Kubernetes version: 1.14
Cloud being used: (put bare-metal if not on a public cloud) bare-metal
Installation method: Hard Way
Host OS: ubuntu
CNI and version: weave
CRI and version:

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We are using the hard way to configure and I don’t see the CSRs being auto approved. What am I missing. We used mmumshad’s git hub kubernetes-the-hard-way. Here are the exact steps.

TLS Bootstrapping

Copy the ca certificate to the worker node:

scp ca.crt worker-2:~/

Step 1 Configure the Binaries on the Worker node

Download and Install Worker Binaries

worker-2$ wget -q --show-progress --https-only --timestamping \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubectl \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kube-proxy \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubelet

Create the installation directories:

worker-2$ sudo mkdir -p \
  /etc/cni/net.d \
  /opt/cni/bin \
  /var/lib/kubelet \
  /var/lib/kube-proxy \
  /var/lib/kubernetes \
  /var/run/kubernetes

Install the worker binaries:

worker-2$
{
  chmod +x kubectl kube-proxy kubelet
  sudo mv kubectl kube-proxy kubelet /usr/local/bin/
}

Move the ca certificate

sudo mv ca.crt /var/lib/kubernetes/

Step 2 Create the Boostrap Token to be used by Nodes(Kubelets) to invoke Certificate API

Bootstrap Tokens are created as a secret in the kube-system namespace.

master-1$
cat > bootstrap-token-07401b.yaml <<EOF
apiVersion: v1
kind: Secret
metadata:
  # Name MUST be of form "bootstrap-token-<token id>"
  name: bootstrap-token-07401b
  namespace: kube-system

# Type MUST be 'bootstrap.kubernetes.io/token'
type: bootstrap.kubernetes.io/token
stringData:
  # Human readable description. Optional.
  description: "The default bootstrap token generated by 'kubeadm init'."

  # Token ID and secret. Required.
  token-id: 07401b
  token-secret: f395accd246ae52d

  # Expiration. Optional.
  expiration: 2021-03-10T03:22:11Z

  # Allowed usages.
  usage-bootstrap-authentication: "true"
  usage-bootstrap-signing: "true"

  # Extra groups to authenticate the token as. Must start with "system:bootstrappers:"
  auth-extra-groups: system:bootstrappers:worker
EOF

kubectl create -f bootstrap-token-07401b.yaml

Step 3 Authorize workers(kubelets) to create CSR

master-1$ kubectl create clusterrolebinding create-csrs-for-bootstrapping --clusterrole=system:node-bootstrapper --group=system:bootstrappers

--------------- OR ---------------

master-1$ cat > csrs-for-bootstrapping.yaml <<EOF
# enable bootstrapping nodes to create CSR
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: create-csrs-for-bootstrapping
subjects:
- kind: Group
  name: system:bootstrappers
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: system:node-bootstrapper
  apiGroup: rbac.authorization.k8s.io
EOF


master-1$ kubectl create -f csrs-for-bootstrapping.yaml

Step 4 Authorize workers(kubelets) to approve CSR

master-1$ kubectl create clusterrolebinding auto-approve-csrs-for-group --clusterrole=system:certificates.k8s.io:certificatesigningrequests:nodeclient --group=system:bootstrappers

 --------------- OR ---------------

master-1$ cat > auto-approve-csrs-for-group.yaml <<EOF
# Approve all CSRs for the group "system:bootstrappers"
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: auto-approve-csrs-for-group
subjects:
- kind: Group
  name: system:bootstrappers
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: system:certificates.k8s.io:certificatesigningrequests:nodeclient
  apiGroup: rbac.authorization.k8s.io
EOF


master-1$ kubectl create -f auto-approve-csrs-for-group.yaml

Step 5 Authorize workers(kubelets) to Auto Renew Certificates on expiration

We now create the Cluster Role Binding required for the nodes to automatically renew the certificates on expiry. Note that we are NOT using the system:bootstrappers group here any more. Since by the renewal period, we believe the node would be bootstrapped and part of the cluster already. All nodes are part of the system:nodes group.

master-1$ kubectl create clusterrolebinding auto-approve-renewals-for-nodes --clusterrole=system:certificates.k8s.io:certificatesigningrequests:selfnodeclient --group=system:nodes

--------------- OR ---------------

master-1$ cat > auto-approve-renewals-for-nodes.yaml <<EOF
# Approve renewal CSRs for the group "system:nodes"
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: auto-approve-renewals-for-nodes
subjects:
- kind: Group
  name: system:nodes
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: system:certificates.k8s.io:certificatesigningrequests:selfnodeclient
  apiGroup: rbac.authorization.k8s.io
EOF

master-1$ kubectl create -f auto-approve-renewals-for-nodes.yaml

Step 6 Configure Kubelet to TLS Bootstrap

This is to be done on the worker-2 node.

worker-2$ sudo kubectl config --kubeconfig=/var/lib/kubelet/bootstrap-kubeconfig set-cluster bootstrap --server='https://192.168.5.30:6443' --certificate-authority=/var/lib/kubernetes/ca.crt
worker-2$ sudo kubectl config --kubeconfig=/var/lib/kubelet/bootstrap-kubeconfig set-credentials kubelet-bootstrap --token=07401b.f395accd246ae52d
worker-2$ sudo kubectl config --kubeconfig=/var/lib/kubelet/bootstrap-kubeconfig set-context bootstrap --user=kubelet-bootstrap --cluster=bootstrap
worker-2$ sudo kubectl config --kubeconfig=/var/lib/kubelet/bootstrap-kubeconfig use-context bootstrap

Or

worker-2$ cat <<EOF | sudo tee /var/lib/kubelet/bootstrap-kubeconfig
apiVersion: v1
clusters:
- cluster:
    certificate-authority: /var/lib/kubernetes/ca.crt
    server: https://192.168.5.30:6443
  name: bootstrap
contexts:
- context:
    cluster: bootstrap
    user: kubelet-bootstrap
  name: bootstrap
current-context: bootstrap
kind: Config
preferences: {}
users:
- name: kubelet-bootstrap
  user:
    token: 07401b.f395accd246ae52d
EOF

Step 7 Create Kubelet Config File

Create the kubelet-config.yaml configuration file:

worker-2$ cat <<EOF | sudo tee /var/lib/kubelet/kubelet-config.yaml
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
  anonymous:
    enabled: false
  webhook:
    enabled: true
  x509:
    clientCAFile: "/var/lib/kubernetes/ca.crt"
authorization:
  mode: Webhook
clusterDomain: "cluster.local"
clusterDNS:
  - "10.96.0.10"
resolvConf: "/run/systemd/resolve/resolv.conf"
runtimeRequestTimeout: "15m"
EOF

Note: We are not specifying the certificate details - tlsCertFile and tlsPrivateKeyFile - in this file

Step 8 Configure Kubelet Service

Create the kubelet.service systemd unit file:

worker-2$ cat <<EOF | sudo tee /etc/systemd/system/kubelet.service
[Unit]
Description=Kubernetes Kubelet
Documentation=https://github.com/kubernetes/kubernetes
After=docker.service
Requires=docker.service

[Service]
ExecStart=/usr/local/bin/kubelet \\
  --bootstrap-kubeconfig="/var/lib/kubelet/bootstrap-kubeconfig" \\
  --config=/var/lib/kubelet/kubelet-config.yaml \\
  --image-pull-progress-deadline=2m \\
  --kubeconfig=/var/lib/kubelet/kubeconfig \\
  --cert-dir=/var/lib/kubelet/pki/ \\
  --rotate-certificates=true \\
  --rotate-server-certificates=true \\
  --network-plugin=cni \\
  --register-node=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Things to note here:

  • bootstrap-kubeconfig : Location of the bootstrap-kubeconfig file.
  • cert-dir : The directory where the generated certificates are stored.
  • rotate-certificates : Rotates client certificates when they expire.
  • rotate-server-certificates : Requests for server certificates on bootstrap and rotates them when they expire.

Step 9 Configure the Kubernetes Proxy

worker-2$ sudo mv kube-proxy.kubeconfig /var/lib/kube-proxy/kubeconfig

Create the kube-proxy-config.yaml configuration file:

worker-2$ cat <<EOF | sudo tee /var/lib/kube-proxy/kube-proxy-config.yaml
kind: KubeProxyConfiguration
apiVersion: kubeproxy.config.k8s.io/v1alpha1
clientConnection:
  kubeconfig: "/var/lib/kube-proxy/kubeconfig"
mode: "iptables"
clusterCIDR: "192.168.5.0/24"
EOF

Create the kube-proxy.service systemd unit file:

worker-2$ cat <<EOF | sudo tee /etc/systemd/system/kube-proxy.service
[Unit]
Description=Kubernetes Kube Proxy
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-proxy \\
  --config=/var/lib/kube-proxy/kube-proxy-config.yaml
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Step 10 Start the Worker Services

worker-2$ 
{
  sudo systemctl daemon-reload
  sudo systemctl enable kubelet kube-proxy
  sudo systemctl start kubelet kube-proxy
}

Step 11 Approve Server CSR

Run on Master
kubectl get csr

NAME                                                   AGE   REQUESTOR                 CONDITION
csr-95bv6                                              20s   system:node:worker-2      Pending

Approve

kubectl certificate approve csr-95bv6

Verification

List the registered Kubernetes nodes from the master node:

master-1$ kubectl get nodes --kubeconfig admin.kubeconfig

–cgroup-driver=systemd

Add following flag --controllers=*,bootstrapsigner,tokencleaner to the controller manager service file. So service file should look like following:

cat <<EOF | sudo tee /etc/systemd/system/kube-controller-manager.service
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-controller-manager \\
  --address=0.0.0.0 \\
  --cluster-cidr=10.200.0.0/16 \\
  --cluster-name=kubernetes \\
  --cluster-signing-cert-file=/var/lib/kubernetes/ca.pem \\
  --cluster-signing-key-file=/var/lib/kubernetes/ca-key.pem \\
  --controllers=*,bootstrapsigner,tokencleaner \\
  --kubeconfig=/var/lib/kubernetes/kube-controller-manager.kubeconfig \\
  --leader-elect=true \\
  --root-ca-file=/var/lib/kubernetes/ca.pem \\
  --service-account-private-key-file=/var/lib/kubernetes/service-account-key.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --use-service-account-credentials=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

First of all you need to generate token.

Create bootstrap token
echo (openssl rand -hex 3).$(openssl rand -hex 8)
Output

07401b.f395accd246ae52d

Have you completed prerequisite mentioned in article.

Pre-Requisite

kube-apiserver - Ensure bootstrap token based authentication is enabled on the kube-apiserver.

–enable-bootstrap-token-auth=true

kube-controller-manager - The certificate requests are signed by the kube-controller-manager ultimately. The kube-controller-manager requires the CA Certificate and Key to perform these operations.

–cluster-signing-cert-file=/var/lib/kubernetes/ca.crt \
–cluster-signing-key-file=/var/lib/kubernetes/ca.key

Copy the ca certificate to the worker node:

scp ca.crt worker-2:~/