Check the cluster ID (kube-system UID) when updating the cluster (#5299)

* Add an admission webhook to check cluster ID (kube-system UID) before updating

* Add an admission webhook to check cluster ID (kube-system UID) before updating

pkg/controller/cluster/cluster_webhook.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2020 The KubeSphere 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 cluster
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	v1 "k8s.io/api/admission/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/tools/clientcmd"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	clusterv1alpha1 "kubesphere.io/api/cluster/v1alpha1"
+)
+
+type ValidatingHandler struct {
+	Client  client.Client
+	decoder *admission.Decoder
+}
+
+var _ admission.DecoderInjector = &ValidatingHandler{}
+
+// InjectDecoder injects the decoder into a ValidatingHandler.
+func (h *ValidatingHandler) InjectDecoder(d *admission.Decoder) error {
+	h.decoder = d
+	return nil
+}
+
+// Handle handles admission requests.
+func (h *ValidatingHandler) Handle(ctx context.Context, req admission.Request) admission.Response {
+
+	if req.Operation != v1.Update {
+		return admission.Allowed("")
+	}
+
+	newCluster := &clusterv1alpha1.Cluster{}
+	err := h.decoder.DecodeRaw(req.Object, newCluster)
+	if err != nil {
+		return admission.Errored(http.StatusBadRequest, err)
+	}
+
+	oldCluster := &clusterv1alpha1.Cluster{}
+	err = h.decoder.DecodeRaw(req.OldObject, oldCluster)
+	if err != nil {
+		return admission.Errored(http.StatusBadRequest, err)
+	}
+
+	clusterConfig, err := clientcmd.RESTConfigFromKubeConfig(newCluster.Spec.Connection.KubeConfig)
+	if err != nil {
+		return admission.Denied(fmt.Sprintf("failed to load cluster config for %s: %s", newCluster.Name, err))
+	}
+
+	clusterClient, err := kubernetes.NewForConfig(clusterConfig)
+	if err != nil {
+		return admission.Denied(err.Error())
+	}
+	kubeSystem, err := clusterClient.CoreV1().Namespaces().Get(ctx, metav1.NamespaceSystem, metav1.GetOptions{})
+	if err != nil {
+		return admission.Denied(err.Error())
+	}
+
+	if oldCluster.Status.UID != kubeSystem.UID {
+		return admission.Denied("this kubeconfig corresponds to a different cluster than the previous one, you need to make sure that kubeconfig is not from another cluster")
+	}
+
+	return admission.Allowed("")
+}