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admission.go
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admission.go
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// Copyright 2023 SAP SE or an SAP affiliate company. All rights reserved. This file is licensed under the Apache Software License, v. 2 except as noted otherwise in the LICENSE file
//
// 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 apiserver
import (
"context"
"fmt"
"strings"
appsv1 "k8s.io/api/apps/v1"
corev1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/runtime/schema"
"k8s.io/apimachinery/pkg/runtime/serializer"
"k8s.io/apimachinery/pkg/runtime/serializer/json"
utilruntime "k8s.io/apimachinery/pkg/util/runtime"
webhookadmissionv1 "k8s.io/apiserver/pkg/admission/plugin/webhook/config/apis/webhookadmission/v1"
webhookadmissionv1alpha1 "k8s.io/apiserver/pkg/admission/plugin/webhook/config/apis/webhookadmission/v1alpha1"
apiserverv1alpha1 "k8s.io/apiserver/pkg/apis/apiserver/v1alpha1"
"sigs.k8s.io/controller-runtime/pkg/client"
"sigs.k8s.io/yaml"
kubernetesutils "github.com/gardener/gardener/pkg/utils/kubernetes"
)
var admissionCodec runtime.Codec
func init() {
admissionScheme := runtime.NewScheme()
utilruntime.Must(apiserverv1alpha1.AddToScheme(admissionScheme))
utilruntime.Must(webhookadmissionv1.AddToScheme(admissionScheme))
utilruntime.Must(webhookadmissionv1alpha1.AddToScheme(admissionScheme))
var (
ser = json.NewSerializerWithOptions(json.DefaultMetaFactory, admissionScheme, admissionScheme, json.SerializerOptions{
Yaml: true,
Pretty: false,
Strict: false,
})
versions = schema.GroupVersions([]schema.GroupVersion{
apiserverv1alpha1.SchemeGroupVersion,
webhookadmissionv1.SchemeGroupVersion,
webhookadmissionv1alpha1.SchemeGroupVersion,
})
)
admissionCodec = serializer.NewCodecFactory(admissionScheme).CodecForVersions(ser, ser, versions, versions)
}
const (
configMapAdmissionDataKey = "admission-configuration.yaml"
volumeNameAdmissionConfiguration = "admission-config"
volumeNameAdmissionKubeconfigSecrets = "admission-kubeconfigs"
volumeMountPathAdmissionConfiguration = "/etc/kubernetes/admission"
volumeMountPathAdmissionKubeconfigSecrets = "/etc/kubernetes/admission-kubeconfigs"
)
// ReconcileSecretAdmissionKubeconfigs reconciles the secret containing the kubeconfig for admission plugins.
func ReconcileSecretAdmissionKubeconfigs(ctx context.Context, c client.Client, secret *corev1.Secret, values Values) error {
secret.Data = make(map[string][]byte)
for _, plugin := range values.EnabledAdmissionPlugins {
if len(plugin.Kubeconfig) != 0 {
secret.Data[admissionPluginsKubeconfigFilename(plugin.Name)] = plugin.Kubeconfig
}
}
utilruntime.Must(kubernetesutils.MakeUnique(secret))
return client.IgnoreAlreadyExists(c.Create(ctx, secret))
}
// ReconcileConfigMapAdmission reconciles the ConfigMap containing the configs for the admission plugins.
func ReconcileConfigMapAdmission(ctx context.Context, c client.Client, configMap *corev1.ConfigMap, values Values) error {
configMap.Data = map[string]string{}
admissionConfig := &apiserverv1alpha1.AdmissionConfiguration{}
for _, plugin := range values.EnabledAdmissionPlugins {
rawConfig, err := computeRelevantAdmissionPluginRawConfig(plugin)
if err != nil {
return err
}
if rawConfig != nil {
admissionConfig.Plugins = append(admissionConfig.Plugins, apiserverv1alpha1.AdmissionPluginConfiguration{
Name: plugin.Name,
Path: volumeMountPathAdmissionConfiguration + "/" + admissionPluginsConfigFilename(plugin.Name),
})
configMap.Data[admissionPluginsConfigFilename(plugin.Name)] = string(rawConfig)
}
}
data, err := runtime.Encode(admissionCodec, admissionConfig)
if err != nil {
return err
}
configMap.Data[configMapAdmissionDataKey] = string(data)
utilruntime.Must(kubernetesutils.MakeUnique(configMap))
return client.IgnoreAlreadyExists(c.Create(ctx, configMap))
}
func computeRelevantAdmissionPluginRawConfig(plugin AdmissionPluginConfig) ([]byte, error) {
var (
nothingToMutate = (plugin.Config == nil || plugin.Config.Raw == nil) && len(plugin.Kubeconfig) == 0
mustDefaultConfig = (plugin.Config == nil || plugin.Config.Raw == nil) && len(plugin.Kubeconfig) > 0
kubeconfigFilePath = volumeMountPathAdmissionKubeconfigSecrets + "/" + admissionPluginsKubeconfigFilename(plugin.Name)
)
if len(plugin.Kubeconfig) == 0 {
// This makes sure that the path to the kubeconfig is overwritten if specified in case no kubeconfig was
// provided. It prevents that users can access arbitrary files in the kube-apiserver pods and disguise them as
// kubeconfigs for their admission plugin configs.
kubeconfigFilePath = ""
}
switch plugin.Name {
case "ValidatingAdmissionWebhook", "MutatingAdmissionWebhook":
if nothingToMutate {
return nil, nil
}
if mustDefaultConfig {
if plugin.Config == nil {
plugin.Config = &runtime.RawExtension{}
}
if len(plugin.Config.Raw) == 0 {
plugin.Config.Raw = []byte(fmt.Sprintf(`apiVersion: %s
kind: WebhookAdmissionConfiguration`, webhookadmissionv1.SchemeGroupVersion.String()))
}
}
configObj, err := runtime.Decode(admissionCodec, plugin.Config.Raw)
if err != nil {
return nil, fmt.Errorf("cannot decode config for admission plugin %s: %w", plugin.Name, err)
}
switch config := configObj.(type) {
case *webhookadmissionv1.WebhookAdmission:
config.KubeConfigFile = kubeconfigFilePath
return runtime.Encode(admissionCodec, config)
case *webhookadmissionv1alpha1.WebhookAdmission:
config.KubeConfigFile = kubeconfigFilePath
return runtime.Encode(admissionCodec, config)
default:
return nil, fmt.Errorf("expected apiserver.config.k8s.io/{v1alpha1.WebhookAdmission,v1.WebhookAdmissionConfiguration} in %s plugin configuration but got %T", plugin.Name, config)
}
case "ImagePolicyWebhook":
// The configuration for this admission plugin is not backed by the API machinery, hence we have to use
// regular marshalling.
if nothingToMutate {
return nil, nil
}
if mustDefaultConfig {
if plugin.Config == nil {
plugin.Config = &runtime.RawExtension{}
}
if len(plugin.Config.Raw) == 0 {
plugin.Config.Raw = []byte("imagePolicy: {}")
}
}
config := map[string]interface{}{}
if err := yaml.Unmarshal(plugin.Config.Raw, &config); err != nil {
return nil, fmt.Errorf("failed to unmarshal plugin configuration for %s: %w", plugin.Name, err)
}
if config["imagePolicy"] == nil {
return nil, fmt.Errorf(`expected "imagePolicy" key in configuration but it does not exist`)
}
config["imagePolicy"].(map[string]interface{})["kubeConfigFile"] = kubeconfigFilePath
return yaml.Marshal(config)
default:
// For all other plugins, we do not need to mutate anything, hence we only return the provided config if set.
if plugin.Config != nil && plugin.Config.Raw != nil {
return plugin.Config.Raw, nil
}
}
return nil, nil
}
func admissionPluginsConfigFilename(name string) string {
return strings.ToLower(name) + ".yaml"
}
func admissionPluginsKubeconfigFilename(name string) string {
return strings.ToLower(name) + "-kubeconfig.yaml"
}
// InjectAdmissionSettings injects the admission settings into `gardener-apiserver` and `kube-apiserver` deployments.
func InjectAdmissionSettings(deployment *appsv1.Deployment, configMapAdmissionConfigs *corev1.ConfigMap, secretAdmissionKubeconfigs *corev1.Secret, values Values) {
if len(values.EnabledAdmissionPlugins) > 0 {
deployment.Spec.Template.Spec.Containers[0].Args = append(deployment.Spec.Template.Spec.Containers[0].Args, "--enable-admission-plugins="+strings.Join(admissionPluginNames(values), ","))
}
if len(values.DisabledAdmissionPlugins) > 0 {
deployment.Spec.Template.Spec.Containers[0].Args = append(deployment.Spec.Template.Spec.Containers[0].Args, "--disable-admission-plugins="+strings.Join(disabledAdmissionPluginNames(values), ","))
}
deployment.Spec.Template.Spec.Containers[0].Args = append(deployment.Spec.Template.Spec.Containers[0].Args, fmt.Sprintf("--admission-control-config-file=%s/%s", volumeMountPathAdmissionConfiguration, configMapAdmissionDataKey))
deployment.Spec.Template.Spec.Containers[0].VolumeMounts = append(deployment.Spec.Template.Spec.Containers[0].VolumeMounts,
corev1.VolumeMount{
Name: volumeNameAdmissionConfiguration,
MountPath: volumeMountPathAdmissionConfiguration,
},
corev1.VolumeMount{
Name: volumeNameAdmissionKubeconfigSecrets,
MountPath: volumeMountPathAdmissionKubeconfigSecrets,
},
)
deployment.Spec.Template.Spec.Volumes = append(deployment.Spec.Template.Spec.Volumes,
corev1.Volume{
Name: volumeNameAdmissionConfiguration,
VolumeSource: corev1.VolumeSource{
ConfigMap: &corev1.ConfigMapVolumeSource{
LocalObjectReference: corev1.LocalObjectReference{
Name: configMapAdmissionConfigs.Name,
},
},
},
},
corev1.Volume{
Name: volumeNameAdmissionKubeconfigSecrets,
VolumeSource: corev1.VolumeSource{
Secret: &corev1.SecretVolumeSource{
SecretName: secretAdmissionKubeconfigs.Name,
},
},
},
)
}
func admissionPluginNames(values Values) []string {
var out []string
for _, plugin := range values.EnabledAdmissionPlugins {
out = append(out, plugin.Name)
}
return out
}
func disabledAdmissionPluginNames(values Values) []string {
var out []string
for _, plugin := range values.DisabledAdmissionPlugins {
out = append(out, plugin.Name)
}
return out
}