Add example program for SubjectAccessReviews

Author: rfranzke

examples/subjectaccessreview/main.go

@@ -0,0 +1,58 @@
+/*
+Copyright 2021 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 main
+
+import (
+	"os"
+
+	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
+	"sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/log/zap"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+	"sigs.k8s.io/controller-runtime/pkg/manager/signals"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/authorization"
+)
+
+func init() {
+	log.SetLogger(zap.New())
+}
+
+func main() {
+	entryLog := log.Log.WithName("entrypoint")
+
+	// Setup a Manager
+	entryLog.Info("setting up manager")
+	mgr, err := manager.New(config.GetConfigOrDie(), manager.Options{})
+	if err != nil {
+		entryLog.Error(err, "unable to set up overall controller manager")
+		os.Exit(1)
+	}
+
+	// Setup webhooks
+	entryLog.Info("setting up webhook server")
+	hookServer := mgr.GetWebhookServer()
+
+	entryLog.Info("registering webhooks to the webhook server")
+	hookServer.Register("/validate-v1-subjectaccessreview", &authorization.Webhook{Handler: &authorizer{}})
+
+	entryLog.Info("starting manager")
+	if err := mgr.Start(signals.SetupSignalHandler()); err != nil {
+		entryLog.Error(err, "unable to run manager")
+		os.Exit(1)
+	}
+}

examples/subjectaccessreview/subjectaccessreview.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2021 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 main
+
+import (
+	"context"
+
+	"sigs.k8s.io/controller-runtime/pkg/webhook/authorization"
+)
+
+// authorizer validates subjectaccessreviews
+type authorizer struct {
+}
+
+// authorizer admits a request by the token.
+func (a *authorizer) Handle(ctx context.Context, req authorization.Request) authorization.Response {
+	if req.Spec.User == "system:anonymous" {
+		return authorization.Denied("anonymous users are not allowed")
+	}
+	if req.Spec.User == "foo" {
+		return authorization.NoOpinion("I don't care if foo is authorized or not")
+	}
+	return authorization.Allowed()
+}