73 lines
2.6 KiB
Go
73 lines
2.6 KiB
Go
/*
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Copyright 2015 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 alwayspullimages contains an admission controller that modifies every new Pod to force
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// the image pull policy to Always. This is useful in a multitenant cluster so that users can be
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// assured that their private images can only be used by those who have the credentials to pull
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// them. Without this admission controller, once an image has been pulled to a node, any pod from
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// any user can use it simply by knowing the image's name (assuming the Pod is scheduled onto the
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// right node), without any authorization check against the image. With this admission controller
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// enabled, images are always pulled prior to starting containers, which means valid credentials are
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// required.
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package alwayspullimages
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import (
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"io"
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apierrors "k8s.io/apimachinery/pkg/api/errors"
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"k8s.io/apiserver/pkg/admission"
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"k8s.io/kubernetes/pkg/api"
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)
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func init() {
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admission.RegisterPlugin("AlwaysPullImages", func(config io.Reader) (admission.Interface, error) {
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return NewAlwaysPullImages(), nil
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})
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}
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// alwaysPullImages is an implementation of admission.Interface.
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// It looks at all new pods and overrides each container's image pull policy to Always.
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type alwaysPullImages struct {
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*admission.Handler
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}
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func (a *alwaysPullImages) Admit(attributes admission.Attributes) (err error) {
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// Ignore all calls to subresources or resources other than pods.
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if len(attributes.GetSubresource()) != 0 || attributes.GetResource().GroupResource() != api.Resource("pods") {
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return nil
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}
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pod, ok := attributes.GetObject().(*api.Pod)
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if !ok {
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return apierrors.NewBadRequest("Resource was marked with kind Pod but was unable to be converted")
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}
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for i := range pod.Spec.InitContainers {
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pod.Spec.InitContainers[i].ImagePullPolicy = api.PullAlways
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}
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for i := range pod.Spec.Containers {
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pod.Spec.Containers[i].ImagePullPolicy = api.PullAlways
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}
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return nil
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}
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// NewAlwaysPullImages creates a new always pull images admission control handler
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func NewAlwaysPullImages() admission.Interface {
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return &alwaysPullImages{
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Handler: admission.NewHandler(admission.Create, admission.Update),
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}
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}
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