kubeconfig generator script for service account with RBAC.

1_sa-kubeconfig-gen.sh

#!/bin/bash
set -e
set -o pipefail

# Add user to k8s using service account, RBAC role file needed
if [[ -z "$1" ]] || [[ -z "$2" ]] || [[ -z "$3" ]]; then
 echo "usage: $0 <service_account_name> <namespace> [rbac-role-yaml]"
 exit 1
fi

SERVICE_ACCOUNT_NAME=$1
NAMESPACE="$2"
RBAC_ROLE_YAML=$3
KUBECFG_FILE_NAME="./kube/k8s-${SERVICE_ACCOUNT_NAME}-${NAMESPACE}-conf"
TARGET_FOLDER="./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}"
}

create_rbac_role() {
    echo -e "\\nCreating a rbac role in ${NAMESPACE} namespace: ${RBAC_ROLE_YAML}"
    kubectl create -f $RBAC_ROLE_YAML --namespace "${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 json | jq -r .secrets[].name)
    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}"
}

create_target_folder
create_service_account
create_rbac_role
get_secret_name_from_service_account
extract_ca_crt_from_secret
get_user_token_from_secret
set_kube_config_values

echo -e "\\nAll done! Test with:"
echo "KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods"
KUBECONFIG=${KUBECFG_FILE_NAME} kubectl get pods

2_rbac-user-role.yaml

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: user-role
rules:
- apiGroups: ["extensions", "apps"]
  resources: ["deployments"]
  verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "list", "watch"]
- apiGroups: [""]
  resources: ["services"]
  verbs: ["create", "get", "list", "patch", "update", "delete"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: user-rolebinding
subjects:
- kind: ServiceAccount
  name: user-sa
roleRef:
  kind: Role
  name: user-role
  apiGroup: rbac.authorization.k8s.io

3_Instruction.md

Script Usage instruction.

chmod +x sa-kubeconfig-gen.sh
./sa-kubeconfig-gen.sh user-sa staging rbac-user-role.yaml