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115 lines
3.2 KiB
Go
115 lines
3.2 KiB
Go
/*
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Copyright 2020 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package denyserviceexternalips
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import (
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"context"
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"fmt"
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"io"
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"k8s.io/apimachinery/pkg/api/errors"
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"k8s.io/apiserver/pkg/admission"
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"k8s.io/klog/v2"
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"k8s.io/kubernetes/pkg/apis/core"
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)
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const (
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// PluginName is the name of this admission controller plugin
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PluginName = "DenyServiceExternalIPs"
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)
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// Register registers a plugin
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func Register(plugins *admission.Plugins) {
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plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
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plugin := newPlugin()
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return plugin, nil
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})
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}
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// externalIPsDenierPlugin holds state for and implements the admission plugin.
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type externalIPsDenierPlugin struct {
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*admission.Handler
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}
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var _ admission.Interface = &externalIPsDenierPlugin{}
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var _ admission.ValidationInterface = &externalIPsDenierPlugin{}
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// newPlugin creates a new admission plugin.
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func newPlugin() *externalIPsDenierPlugin {
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return &externalIPsDenierPlugin{
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Handler: admission.NewHandler(admission.Create, admission.Update),
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}
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}
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// Admit ensures that modifications of the Service.Spec.ExternalIPs field are
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// denied
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func (plug *externalIPsDenierPlugin) Validate(ctx context.Context, attr admission.Attributes, o admission.ObjectInterfaces) error {
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if attr.GetResource().GroupResource() != core.Resource("services") {
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return nil
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}
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if len(attr.GetSubresource()) != 0 {
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return nil
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}
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// if we can't convert then we don't handle this object so just return
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newSvc, ok := attr.GetObject().(*core.Service)
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if !ok {
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klog.V(3).Infof("Expected Service resource, got: %v", attr.GetKind())
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return errors.NewInternalError(fmt.Errorf("Expected Service resource, got: %v", attr.GetKind()))
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}
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var oldSvc *core.Service
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if old := attr.GetOldObject(); old != nil {
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tmp, ok := old.(*core.Service)
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if !ok {
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klog.V(3).Infof("Expected Service resource, got: %v", attr.GetKind())
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return errors.NewInternalError(fmt.Errorf("Expected Service resource, got: %v", attr.GetKind()))
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}
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oldSvc = tmp
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}
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if isSubset(newSvc, oldSvc) {
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return nil
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}
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klog.V(4).Infof("Denying new use of ExternalIPs on Service %s/%s", newSvc.Namespace, newSvc.Name)
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return admission.NewForbidden(attr, fmt.Errorf("Use of external IPs is denied by admission control"))
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}
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func isSubset(newSvc, oldSvc *core.Service) bool {
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// If new has none, it's a subset.
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if len(newSvc.Spec.ExternalIPs) == 0 {
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return true
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}
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// If we have some but it's not an update, it's not a subset.
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if oldSvc == nil {
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return false
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}
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oldIPs := map[string]bool{}
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for _, ip := range oldSvc.Spec.ExternalIPs {
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oldIPs[ip] = true
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}
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// Every IP in newSvc must be in oldSvc
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for _, ip := range newSvc.Spec.ExternalIPs {
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if oldIPs[ip] == false {
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return false
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}
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}
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return true
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}
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