create-kube-config.sh

#!/bin/bash
set -e
set -o pipefail
# Add user to k8s using service account, no RBAC (must create RBAC after this script)
if [[ -z "$1" ]] || [[ -z "$2" ]]; then
 echo "usage: $0 <service_account_name> <namespace>"
 exit 1
fi
SERVICE_ACCOUNT_NAME=$1
NAMESPACE="$2"
KUBECFG_FILE_NAME="/tmp/kube/k8s-${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-conf"
TARGET_FOLDER="/tmp/kube"
create_target_folder() {
    echo -n "Creating target directory to hold files in ${TARGET_FOLDER}..."
    mkdir -p "${TARGET_FOLDER}"
    printf "done"
}
create_service_account() {
    echo -e "\\nCreating a service account in ${NAMESPACE} namespace: ${SERVICE_ACCOUNT_NAME}"
    kubectl create sa "${SERVICE_ACCOUNT_NAME}" --namespace "${NAMESPACE}"
}
get_secret_name_from_service_account() {
    echo -e "\\nGetting secret of service account ${SERVICE_ACCOUNT_NAME} on ${NAMESPACE}"
    SECRET_NAME=$(kubectl get sa "${SERVICE_ACCOUNT_NAME}" --namespace="${NAMESPACE}" -o jsonpath="{.secrets[].name}")
    if [ -z "$SECRET_NAME" ]
    then
        echo "Secret not found."
        create_secret_token
    else
        echo "Secret name: ${SECRET_NAME}"
    fi
}
create_secret_token() {
    SECRET_NAME=${SERVICE_ACCOUNT_NAME}-token
    echo -e "\\nCreating secret of service account ${SERVICE_ACCOUNT_NAME} on ${NAMESPACE}"
    cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Secret
metadata:
  name: ${SERVICE_ACCOUNT_NAME}-token
  namespace: ${NAMESPACE}
  annotations:
    kubernetes.io/service-account.name: ${SERVICE_ACCOUNT_NAME}
type: kubernetes.io/service-account-token
EOF
    echo "Secret name: ${SECRET_NAME}"
}
extract_ca_crt_from_secret() {
    echo -e -n "\\nExtracting ca.crt from secret..."
    kubectl get secret --namespace "${NAMESPACE}" "${SECRET_NAME}" -o json | jq \
    -r '.data["ca.crt"]' | base64 -d > "${TARGET_FOLDER}/ca.crt"
    printf "done"
}
get_user_token_from_secret() {
    echo -e -n "\\nGetting user token from secret..."
    USER_TOKEN=$(kubectl get secret --namespace "${NAMESPACE}" "${SECRET_NAME}" -o json | jq -r '.data["token"]' | base64 -d)
    printf "done"
}
set_kube_config_values() {
    context=$(kubectl config current-context)
    echo -e "\\nSetting current context to: $context"
    CLUSTER_NAME=$(kubectl config get-contexts "$context" | awk '{print $3}' | tail -n 1)
    echo "Cluster name: ${CLUSTER_NAME}"
    ENDPOINT=$(kubectl config view \
    -o jsonpath="{.clusters[?(@.name == \"${CLUSTER_NAME}\")].cluster.server}")
    echo "Endpoint: ${ENDPOINT}"
    # Set up the config
    echo -e "\\nPreparing k8s-${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-conf"
    echo -n "Setting a cluster entry in kubeconfig..."
    kubectl config set-cluster "${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --server="${ENDPOINT}" \
    --certificate-authority="${TARGET_FOLDER}/ca.crt" \
    --embed-certs=true
    echo -n "Setting token credentials entry in kubeconfig..."
    kubectl config set-credentials \
    "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --token="${USER_TOKEN}"
    echo -n "Setting a context entry in kubeconfig..."
    kubectl config set-context \
    "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}" \
    --cluster="${CLUSTER_NAME}" \
    --user="${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --namespace="${NAMESPACE}"
    echo -n "Setting the current-context in the kubeconfig file..."
    kubectl config use-context "${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-${CLUSTER_NAME}" \
    --kubeconfig="${KUBECFG_FILE_NAME}"
}
add_admin_clusterrole() {
    cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: management-cluster-admin
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: management-cluster
  namespace: default
EOF

    echo "Add admin permission.."
}

create_target_folder
create_service_account
get_secret_name_from_service_account
extract_ca_crt_from_secret
get_user_token_from_secret
set_kube_config_values
add_admin_clusterrole
echo -e "\\nAll done! Test with:"
echo "KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods"
KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods