DisableServiceLinks admission controller

pkg/kubeapiserver/options/plugins.go

@@ -31,6 +31,7 @@ import (
 	certsubjectrestriction "k8s.io/kubernetes/plugin/pkg/admission/certificates/subjectrestriction"
 	"k8s.io/kubernetes/plugin/pkg/admission/defaulttolerationseconds"
 	"k8s.io/kubernetes/plugin/pkg/admission/deny"
+	"k8s.io/kubernetes/plugin/pkg/admission/disableservicelinks"
 	"k8s.io/kubernetes/plugin/pkg/admission/eventratelimit"
 	"k8s.io/kubernetes/plugin/pkg/admission/extendedresourcetoleration"
 	"k8s.io/kubernetes/plugin/pkg/admission/gc"
@@ -93,6 +94,7 @@ var AllOrderedPlugins = []string{
 	certsubjectrestriction.PluginName,       // CertificateSubjectRestriction
 	defaultingressclass.PluginName,          // DefaultIngressClass
 	denyserviceexternalips.PluginName,       // DenyServiceExternalIPs
+	disableservicelinks.PluginName,          // DisableServiceLinks
 
 	// new admission plugins should generally be inserted above here
 	// webhook, resourcequota, and deny plugins must go at the end
@@ -114,6 +116,7 @@ func RegisterAllAdmissionPlugins(plugins *admission.Plugins) {
 	defaultingressclass.Register(plugins)
 	denyserviceexternalips.Register(plugins)
 	deny.Register(plugins) // DEPRECATED as no real meaning
+	disableservicelinks.Register(plugins)
 	eventratelimit.Register(plugins)
 	extendedresourcetoleration.Register(plugins)
 	gc.Register(plugins)

plugin/pkg/admission/disableservicelinks/admission.go

@@ -0,0 +1,76 @@
+/*
+Copyright 2024 The Kubernetes 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 disableservicelinks
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apiserver/pkg/admission"
+	"k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/utils/ptr"
+)
+
+// PluginName indicates name of admission plugin.
+const PluginName = "DisableServiceLinks"
+
+// Register is called by the apiserver to register the plugin factory.
+func Register(plugins *admission.Plugins) {
+	plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
+		return newDisableServiceLinks(), nil
+	})
+}
+
+// newDisableServiceLinks creates a new instance of the DisableServiceLinks admission controller.
+func newDisableServiceLinks() *plugin {
+	return &plugin{
+		Handler: admission.NewHandler(admission.Create, admission.Update),
+	}
+}
+
+// Make sure we are implementing the interface.
+var _ admission.MutationInterface = &plugin{}
+
+type plugin struct {
+	*admission.Handler
+}
+
+// Admit updates the EnableServiceLinks of a pod and set it to false.
+func (p *plugin) Admit(ctx context.Context, attributes admission.Attributes, o admission.ObjectInterfaces) error {
+	op := attributes.GetOperation()
+
+	// noop admission.Update for future support
+	if op == admission.Update {
+		return nil
+	}
+
+	// Ignore all calls to subresources or resources other than pods.
+	if len(attributes.GetSubresource()) != 0 || attributes.GetResource().GroupResource() != core.Resource("pods") {
+		return nil
+	}
+
+	pod, ok := attributes.GetObject().(*core.Pod)
+	if !ok {
+		return errors.NewBadRequest(fmt.Sprintf("expected *core.Pod but got %T", attributes.GetObject()))
+	}
+
+	pod.Spec.EnableServiceLinks = ptr.To(false)
+
+	return nil
+}

plugin/pkg/admission/disableservicelinks/admission_test.go

@@ -0,0 +1,101 @@
+/*
+Copyright 2024 The Kubernetes 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 disableservicelinks
+
+import (
+	"context"
+	"testing"
+
+	"k8s.io/apiserver/pkg/admission"
+	admissiontesting "k8s.io/apiserver/pkg/admission/testing"
+	"k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/apis/core/helper"
+	"k8s.io/utils/ptr"
+)
+
+func TestAdmit(t *testing.T) {
+
+	plugin := admissiontesting.WithReinvocationTesting(t, newDisableServiceLinks())
+
+	tests := []struct {
+		description  string
+		requestedPod core.Pod
+		expectedPod  core.Pod
+		operation    admission.Operation
+	}{
+		{
+			description: "Create empty pod with default value of Spec.EnableServiceLinks",
+			requestedPod: core.Pod{
+				Spec: core.PodSpec{},
+			},
+			expectedPod: core.Pod{
+				Spec: core.PodSpec{EnableServiceLinks: ptr.To(false)},
+			},
+			operation: admission.Create,
+		},
+		{
+			description: "Create empty pod with Spec.EnableServiceLinks set to true",
+			requestedPod: core.Pod{
+				Spec: core.PodSpec{EnableServiceLinks: ptr.To(true)},
+			},
+			expectedPod: core.Pod{
+				Spec: core.PodSpec{EnableServiceLinks: ptr.To(false)},
+			},
+			operation: admission.Create,
+		},
+		{
+			description: "Update empty pod with Spec.EnableServiceLinks set to true",
+			requestedPod: core.Pod{
+				Spec: core.PodSpec{EnableServiceLinks: ptr.To(true)},
+			},
+			expectedPod: core.Pod{
+				Spec: core.PodSpec{EnableServiceLinks: ptr.To(true)},
+			},
+			operation: admission.Update,
+		},
+	}
+	for i, test := range tests {
+		err := plugin.Admit(context.TODO(), admission.NewAttributesRecord(&test.requestedPod, nil,
+			core.Kind("Pod").WithVersion("version"), "foo", "name",
+			core.Resource("pods").WithVersion("version"), "", test.operation,
+			nil, false, nil), nil)
+
+		if err != nil {
+			t.Errorf("[%d: %s] unexpected error %v for pod %+v", i, test.description, err, test.requestedPod)
+		}
+
+		if !helper.Semantic.DeepEqual(test.expectedPod.Spec, test.requestedPod.Spec) {
+			t.Errorf("[%d: %s] expected %t got %t", i, test.description, *test.expectedPod.Spec.EnableServiceLinks, *test.requestedPod.Spec.EnableServiceLinks)
+		}
+	}
+}
+
+func TestHandles(t *testing.T) {
+	plugin := newDisableServiceLinks()
+	tests := map[admission.Operation]bool{
+		admission.Create:  true,
+		admission.Update:  true,
+		admission.Delete:  false,
+		admission.Connect: false,
+	}
+	for op, expected := range tests {
+		result := plugin.Handles(op)
+		if result != expected {
+			t.Errorf("Unexpected result for operation %s: %v\n", op, result)
+		}
+	}
+}