kubernetes/cmd/kubeadm/app/phases/kubelet/config.go

/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package kubelet

import (
	"fmt"
	"io"
	"os"
	"path/filepath"

	"github.com/pkg/errors"

	v1 "k8s.io/api/core/v1"
	rbac "k8s.io/api/rbac/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	clientset "k8s.io/client-go/kubernetes"
	kubeletconfig "k8s.io/kubelet/config/v1beta1"
	"sigs.k8s.io/yaml"

	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
	"k8s.io/kubernetes/cmd/kubeadm/app/componentconfigs"
	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
	"k8s.io/kubernetes/cmd/kubeadm/app/util/patches"
)

// WriteConfigToDisk writes the kubelet config object down to a file
// Used at "kubeadm init" and "kubeadm upgrade" time
func WriteConfigToDisk(cfg *kubeadmapi.ClusterConfiguration, kubeletDir, patchesDir string, output io.Writer) error {
	kubeletCfg, ok := cfg.ComponentConfigs[componentconfigs.KubeletGroup]
	if !ok {
		return errors.New("no kubelet component config found")
	}

	if err := kubeletCfg.Mutate(); err != nil {
		return err
	}

	kubeletBytes, err := kubeletCfg.Marshal()
	if err != nil {
		return err
	}

	// Apply patches to the KubeletConfiguration
	if len(patchesDir) != 0 {
		kubeletBytes, err = applyKubeletConfigPatches(kubeletBytes, patchesDir, output)
		if err != nil {
			return errors.Wrap(err, "could not apply patches to the KubeletConfiguration")
		}
	}

	return writeConfigBytesToDisk(kubeletBytes, kubeletDir)
}

// CreateConfigMap creates a ConfigMap with the generic kubelet configuration.
// Used at "kubeadm init" and "kubeadm upgrade" time
func CreateConfigMap(cfg *kubeadmapi.ClusterConfiguration, patchesDir string, client clientset.Interface) error {
	kubeletCfg, ok := cfg.ComponentConfigs[componentconfigs.KubeletGroup]
	if !ok {
		return errors.New("no kubelet component config found in the active component config set")
	}

	kubeletBytes, err := kubeletCfg.Marshal()
	if err != nil {
		return err
	}

	// Apply patches to the KubeletConfiguration
	if len(patchesDir) != 0 {
		kubeletBytes, err = applyKubeletConfigPatches(kubeletBytes, patchesDir, os.Stdout)
		if err != nil {
			return errors.Wrap(err, "could not apply patches to the KubeletConfiguration")
		}
	}

	configMapName := kubeadmconstants.KubeletBaseConfigurationConfigMap
	fmt.Printf("[kubelet] Creating a ConfigMap %q in namespace %s with the configuration for the kubelets in the cluster\n", configMapName, metav1.NamespaceSystem)

	configMap := &v1.ConfigMap{
		ObjectMeta: metav1.ObjectMeta{
			Name:      configMapName,
			Namespace: metav1.NamespaceSystem,
		},
		Data: map[string]string{
			kubeadmconstants.KubeletBaseConfigurationConfigMapKey: string(kubeletBytes),
		},
	}

	if !kubeletCfg.IsUserSupplied() {
		componentconfigs.SignConfigMap(configMap)
	}

	if err := apiclient.CreateOrUpdateConfigMap(client, configMap); err != nil {
		return err
	}

	if err := createConfigMapRBACRules(client); err != nil {
		return errors.Wrap(err, "error creating kubelet configuration configmap RBAC rules")
	}
	return nil
}

// createConfigMapRBACRules creates the RBAC rules for exposing the base kubelet ConfigMap in the kube-system namespace to unauthenticated users
func createConfigMapRBACRules(client clientset.Interface) error {
	if err := apiclient.CreateOrUpdateRole(client, &rbac.Role{
		ObjectMeta: metav1.ObjectMeta{
			Name:      kubeadmconstants.KubeletBaseConfigMapRole,
			Namespace: metav1.NamespaceSystem,
		},
		Rules: []rbac.PolicyRule{
			{
				Verbs:         []string{"get"},
				APIGroups:     []string{""},
				Resources:     []string{"configmaps"},
				ResourceNames: []string{kubeadmconstants.KubeletBaseConfigurationConfigMap},
			},
		},
	}); err != nil {
		return err
	}

	return apiclient.CreateOrUpdateRoleBinding(client, &rbac.RoleBinding{
		ObjectMeta: metav1.ObjectMeta{
			Name:      kubeadmconstants.KubeletBaseConfigMapRole,
			Namespace: metav1.NamespaceSystem,
		},
		RoleRef: rbac.RoleRef{
			APIGroup: rbac.GroupName,
			Kind:     "Role",
			Name:     kubeadmconstants.KubeletBaseConfigMapRole,
		},
		Subjects: []rbac.Subject{
			{
				Kind: rbac.GroupKind,
				Name: kubeadmconstants.NodesGroup,
			},
			{
				Kind: rbac.GroupKind,
				Name: kubeadmconstants.NodeBootstrapTokenAuthGroup,
			},
		},
	})
}

// writeConfigBytesToDisk writes a byte slice down to disk at the specific location of the kubelet config file
func writeConfigBytesToDisk(b []byte, kubeletDir string) error {
	configFile := filepath.Join(kubeletDir, kubeadmconstants.KubeletConfigurationFileName)
	fmt.Printf("[kubelet-start] Writing kubelet configuration to file %q\n", configFile)

	// creates target folder if not already exists
	if err := os.MkdirAll(kubeletDir, 0700); err != nil {
		return errors.Wrapf(err, "failed to create directory %q", kubeletDir)
	}

	if err := os.WriteFile(configFile, b, 0644); err != nil {
		return errors.Wrapf(err, "failed to write kubelet configuration to the file %q", configFile)
	}
	return nil
}

// applyKubeletConfigPatches reads patches from a directory and applies them over the input kubeletBytes
func applyKubeletConfigPatches(kubeletBytes []byte, patchesDir string, output io.Writer) ([]byte, error) {
	patchManager, err := patches.GetPatchManagerForPath(patchesDir, patches.KnownTargets(), output)
	if err != nil {
		return nil, err
	}

	patchTarget := &patches.PatchTarget{
		Name:                      patches.KubeletConfiguration,
		StrategicMergePatchObject: kubeletconfig.KubeletConfiguration{},
		Data:                      kubeletBytes,
	}
	if err := patchManager.ApplyPatchesToTarget(patchTarget); err != nil {
		return nil, err
	}

	kubeletBytes, err = yaml.JSONToYAML(patchTarget.Data)
	if err != nil {
		return nil, err
	}
	return kubeletBytes, nil
}