/
admissionplugins.go
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/
admissionplugins.go
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// Copyright 2022 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 admissionplugins
import (
"fmt"
"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"
"k8s.io/apimachinery/pkg/util/sets"
"k8s.io/apimachinery/pkg/util/validation/field"
admissionapiv1 "k8s.io/pod-security-admission/admission/api/v1"
admissionapiv1alpha1 "k8s.io/pod-security-admission/admission/api/v1alpha1"
admissionapiv1beta1 "k8s.io/pod-security-admission/admission/api/v1beta1"
"k8s.io/utils/ptr"
"github.com/gardener/gardener/pkg/apis/core"
versionutils "github.com/gardener/gardener/pkg/utils/version"
)
var (
// admissionPluginsVersionRanges contains the version ranges for all Kubernetes admission plugins.
// Extracted from https://raw.githubusercontent.com/kubernetes/kubernetes/release-${version}/pkg/kubeapiserver/options/plugins.go
// and https://raw.githubusercontent.com/kubernetes/kubernetes/release-${version}/staging/src/k8s.io/apiserver/pkg/server/plugins.go.
// To maintain this list for each new Kubernetes version:
// - Run hack/compare-k8s-admission-plugins.sh <old-version> <new-version> (e.g. 'hack/compare-k8s-admission-plugins.sh 1.26 1.27').
// It will present 2 lists of admission plugins: those added and those removed in <new-version> compared to <old-version> and
// - Add all added admission plugins to the map with <new-version> as AddedInVersion and no RemovedInVersion.
// - For any removed admission plugin, add <new-version> as RemovedInVersion to the already existing admission plugin in the map.
admissionPluginsVersionRanges = map[string]*AdmissionPluginVersionRange{
"AlwaysAdmit": {},
"AlwaysDeny": {},
"AlwaysPullImages": {},
"CertificateApproval": {},
"CertificateSigning": {},
"CertificateSubjectRestriction": {},
"ClusterTrustBundleAttest": {VersionRange: versionutils.VersionRange{AddedInVersion: "1.27"}},
"DefaultIngressClass": {},
"DefaultStorageClass": {},
"DefaultTolerationSeconds": {},
"DenyServiceExternalIPs": {},
"EventRateLimit": {},
"ExtendedResourceToleration": {},
"ImagePolicyWebhook": {},
"LimitPodHardAntiAffinityTopology": {},
"LimitRanger": {},
"MutatingAdmissionWebhook": {Required: true},
"NamespaceAutoProvision": {},
"NamespaceExists": {},
"NamespaceLifecycle": {Required: true},
"NodeRestriction": {Required: true},
"OwnerReferencesPermissionEnforcement": {},
"PersistentVolumeClaimResize": {},
"PersistentVolumeLabel": {},
"PodNodeSelector": {},
"PodSecurity": {Required: true},
"PodTolerationRestriction": {},
"Priority": {Required: true},
"ResourceQuota": {},
"RuntimeClass": {},
"SecurityContextDeny": {Forbidden: true},
"ServiceAccount": {},
"StorageObjectInUseProtection": {Required: true},
"TaintNodesByCondition": {},
"ValidatingAdmissionPolicy": {VersionRange: versionutils.VersionRange{AddedInVersion: "1.26"}},
"ValidatingAdmissionWebhook": {Required: true},
}
admissionPluginsSupportingExternalKubeconfig = sets.New("ValidatingAdmissionWebhook", "MutatingAdmissionWebhook", "ImagePolicyWebhook")
runtimeScheme *runtime.Scheme
codec runtime.Codec
)
func init() {
runtimeScheme = runtime.NewScheme()
utilruntime.Must(admissionapiv1alpha1.AddToScheme(runtimeScheme))
utilruntime.Must(admissionapiv1beta1.AddToScheme(runtimeScheme))
utilruntime.Must(admissionapiv1.AddToScheme(runtimeScheme))
var (
ser = json.NewSerializerWithOptions(json.DefaultMetaFactory, runtimeScheme, runtimeScheme, json.SerializerOptions{
Yaml: true,
Pretty: false,
Strict: false,
})
versions = schema.GroupVersions([]schema.GroupVersion{
admissionapiv1alpha1.SchemeGroupVersion,
admissionapiv1beta1.SchemeGroupVersion,
admissionapiv1.SchemeGroupVersion,
})
)
codec = serializer.NewCodecFactory(runtimeScheme).CodecForVersions(ser, ser, versions, versions)
}
// IsAdmissionPluginSupported returns true if the given admission plugin is supported for the given Kubernetes version.
// An admission plugin is only supported if it's a known admission plugin and its version range contains the given Kubernetes version.
func IsAdmissionPluginSupported(plugin, version string) (bool, error) {
vr := admissionPluginsVersionRanges[plugin]
if vr == nil {
return false, fmt.Errorf("unknown admission plugin %q", plugin)
}
return vr.Contains(version)
}
// AdmissionPluginVersionRange represents a version range of type [AddedInVersion, RemovedInVersion).
type AdmissionPluginVersionRange struct {
Forbidden bool
Required bool
versionutils.VersionRange
}
func getAllForbiddenPlugins() []string {
var allForbiddenPlugins []string
for name, vr := range admissionPluginsVersionRanges {
if vr.Forbidden {
allForbiddenPlugins = append(allForbiddenPlugins, name)
}
}
return allForbiddenPlugins
}
// ValidateAdmissionPlugins validates the given Kubernetes admission plugins against the given Kubernetes version.
func ValidateAdmissionPlugins(admissionPlugins []core.AdmissionPlugin, version string, fldPath *field.Path) field.ErrorList {
allErrs := field.ErrorList{}
for i, plugin := range admissionPlugins {
idxPath := fldPath.Index(i)
if len(plugin.Name) == 0 {
allErrs = append(allErrs, field.Required(idxPath.Child("name"), "must provide a name"))
return allErrs
}
supported, err := IsAdmissionPluginSupported(plugin.Name, version)
if err != nil {
allErrs = append(allErrs, field.Invalid(idxPath.Child("name"), plugin.Name, err.Error()))
} else if !supported {
allErrs = append(allErrs, field.Forbidden(idxPath.Child("name"), fmt.Sprintf("admission plugin %q is not supported in Kubernetes version %s", plugin.Name, version)))
} else {
if admissionPluginsVersionRanges[plugin.Name].Forbidden {
allErrs = append(allErrs, field.Forbidden(idxPath.Child("name"), fmt.Sprintf("forbidden admission plugin was specified - do not use plugins from the following list: %+v", getAllForbiddenPlugins())))
}
if ptr.Deref(plugin.Disabled, false) && admissionPluginsVersionRanges[plugin.Name].Required {
allErrs = append(allErrs, field.Forbidden(idxPath, fmt.Sprintf("admission plugin %q cannot be disabled", plugin.Name)))
}
if plugin.KubeconfigSecretName != nil && !admissionPluginsSupportingExternalKubeconfig.Has(plugin.Name) {
allErrs = append(allErrs, field.Forbidden(idxPath.Child("kubeconfigSecretName"), fmt.Sprintf("admission plugin %q does not allow specifying external kubeconfig", plugin.Name)))
}
if err := validateAdmissionPluginConfig(plugin, idxPath); err != nil {
allErrs = append(allErrs, err)
}
}
}
return allErrs
}
func validateAdmissionPluginConfig(plugin core.AdmissionPlugin, fldPath *field.Path) *field.Error {
switch plugin.Name {
case "PodSecurity":
if plugin.Config == nil {
return nil
}
_, err := runtime.Decode(codec, plugin.Config.Raw)
if err != nil {
if runtime.IsNotRegisteredError(err) {
return field.Invalid(fldPath.Child("config"), string(plugin.Config.Raw), "expected pod-security.admission.config.k8s.io/v1.PodSecurityConfiguration")
}
return field.Invalid(fldPath.Child("config"), string(plugin.Config.Raw), "cannot decode the given config: "+err.Error())
}
}
return nil
}