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

pkg/client/restclient/plugin.go

@@ -0,0 +1,60 @@
+/*
+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 restclient
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+
+	"github.com/golang/glog"
+
+	clientcmdapi "k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
+)
+
+type AuthProvider interface {
+	// WrapTransport allows the plugin to create a modified RoundTripper that
+	// attaches authorization headers (or other info) to requests.
+	WrapTransport(http.RoundTripper) http.RoundTripper
+}
+
+type Factory func() (AuthProvider, error)
+
+// All registered auth provider plugins.
+var pluginsLock sync.Mutex
+var plugins = make(map[string]Factory)
+
+func RegisterAuthProviderPlugin(name string, plugin Factory) error {
+	pluginsLock.Lock()
+	defer pluginsLock.Unlock()
+	if _, found := plugins[name]; found {
+		return fmt.Errorf("Auth Provider Plugin %q was registered twice", name)
+	}
+	glog.V(4).Infof("Registered Auth Provider Plugin %q", name)
+	plugins[name] = plugin
+	return nil
+}
+
+func GetAuthProvider(apc *clientcmdapi.AuthProviderConfig) (AuthProvider, error) {
+	pluginsLock.Lock()
+	defer pluginsLock.Unlock()
+	p, ok := plugins[apc.Name]
+	if !ok {
+		return nil, fmt.Errorf("No Auth Provider found for name %q", apc.Name)
+	}
+	return p()
+}