Add client auth plugin framework for kubectl with GCP auth plugin.

plugin/pkg/client/auth/gcp/gcp.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+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 gcp
+
+import (
+	"net/http"
+
+	"github.com/golang/glog"
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
+
+	"k8s.io/kubernetes/pkg/client/restclient"
+)
+
+func init() {
+	if err := restclient.RegisterAuthProviderPlugin("gcp", newGCPAuthProvider); err != nil {
+		glog.Fatalf("Failed to register gcp auth plugin: %v", err)
+	}
+}
+
+type gcpAuthProvider struct {
+	tokenSource oauth2.TokenSource
+}
+
+func newGCPAuthProvider() (restclient.AuthProvider, error) {
+	ts, err := google.DefaultTokenSource(context.TODO(), "https://www.googleapis.com/auth/cloud-platform")
+	if err != nil {
+		return nil, err
+	}
+	return &gcpAuthProvider{ts}, nil
+}
+
+func (g *gcpAuthProvider) WrapTransport(rt http.RoundTripper) http.RoundTripper {
+	return &oauth2.Transport{
+		Source: g.tokenSource,
+		Base:   rt,
+	}
+}

plugin/pkg/client/auth/plugins.go

@@ -0,0 +1,22 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+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 plugins
+
+import (
+	// Initialize all known client auth plugins.
+	_ "k8s.io/kubernetes/plugin/pkg/client/auth/gcp"
+)