provides RequestHeaderAuthRequestController for dynamically filling RequestHeaderConfig struct

Author: p0lyn0mial

staging/src/k8s.io/apiserver/pkg/authentication/request/headerrequest/requestheader_controller.go

@@ -0,0 +1,319 @@
+/*
+Copyright 2020 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 headerrequest
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/equality"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	coreinformers "k8s.io/client-go/informers/core/v1"
+	"k8s.io/client-go/kubernetes"
+	corev1listers "k8s.io/client-go/listers/core/v1"
+	"k8s.io/client-go/tools/cache"
+	"k8s.io/client-go/util/workqueue"
+	"k8s.io/klog"
+	"sync/atomic"
+)
+
+const (
+	authenticationRoleName = "extension-apiserver-authentication-reader"
+)
+
+type requestHeaderBundle struct {
+	UsernameHeaders     []string
+	GroupHeaders        []string
+	ExtraHeaderPrefixes []string
+	AllowedClientNames  []string
+}
+
+// RequestHeaderAuthRequestController a controller that exposes a set of methods for dynamically filling RequestHeaderConfig struct.
+// The methods are sourced from the config map which is being monitored by this controller.
+// The controller is primed from the server at the construction time for components that don't want to dynamically react to changes
+// in the config map.
+type RequestHeaderAuthRequestController struct {
+	name string
+
+	configmapName      string
+	configmapNamespace string
+
+	configmapLister         corev1listers.ConfigMapNamespaceLister
+	configmapInformerSynced cache.InformerSynced
+
+	queue workqueue.RateLimitingInterface
+
+	// exportedRequestHeaderBundle is a requestHeaderBundle that contains the last read, non-zero length content of the configmap
+	exportedRequestHeaderBundle atomic.Value
+
+	usernameHeadersKey     string
+	groupHeadersKey        string
+	extraHeaderPrefixesKey string
+	allowedClientNamesKey  string
+}
+
+// NewRequestHeaderAuthRequestController creates a new controller that implements RequestHeaderAuthRequestController
+func NewRequestHeaderAuthRequestController(
+	cmName string,
+	cmNamespace string,
+	client kubernetes.Interface,
+	cmInformer coreinformers.ConfigMapInformer,
+	usernameHeadersKey, groupHeadersKey, extraHeaderPrefixesKey, allowedClientNamesKey string) (*RequestHeaderAuthRequestController, error) {
+	c := &RequestHeaderAuthRequestController{
+		name: "RequestHeaderAuthRequestController",
+
+		configmapName:      cmName,
+		configmapNamespace: cmNamespace,
+
+		usernameHeadersKey:     usernameHeadersKey,
+		groupHeadersKey:        groupHeadersKey,
+		extraHeaderPrefixesKey: extraHeaderPrefixesKey,
+		allowedClientNamesKey:  allowedClientNamesKey,
+
+		queue: workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "RequestHeaderAuthRequestController"),
+	}
+
+	// use the live client to prime the controller
+	if err := c.syncOnce(client); err != nil {
+		return nil, err
+	}
+
+	cmInformer.Informer().AddEventHandler(cache.FilteringResourceEventHandler{
+		FilterFunc: func(obj interface{}) bool {
+			if cast, ok := obj.(*corev1.ConfigMap); ok {
+				return cast.Name == c.configmapName && cast.Namespace == c.configmapNamespace
+			}
+			if tombstone, ok := obj.(cache.DeletedFinalStateUnknown); ok {
+				if cast, ok := tombstone.Obj.(*corev1.ConfigMap); ok {
+					return cast.Name == c.configmapName && cast.Namespace == c.configmapNamespace
+				}
+			}
+			return true // always return true just in case.  The checks are fairly cheap
+		},
+		Handler: cache.ResourceEventHandlerFuncs{
+			// we have a filter, so any time we're called, we may as well queue. We only ever check one configmap
+			// so we don't have to be choosy about our key.
+			AddFunc: func(obj interface{}) {
+				c.queue.Add(c.keyFn())
+			},
+			UpdateFunc: func(oldObj, newObj interface{}) {
+				c.queue.Add(c.keyFn())
+			},
+			DeleteFunc: func(obj interface{}) {
+				c.queue.Add(c.keyFn())
+			},
+		},
+	})
+
+	c.configmapLister = cmInformer.Lister().ConfigMaps(c.configmapNamespace)
+	c.configmapInformerSynced = cmInformer.Informer().HasSynced
+
+	return c, nil
+}
+
+func (c *RequestHeaderAuthRequestController) UsernameHeaders() []string {
+	return c.loadRequestHeaderFor(c.usernameHeadersKey)
+}
+
+func (c *RequestHeaderAuthRequestController) GroupHeaders() []string {
+	return c.loadRequestHeaderFor(c.groupHeadersKey)
+}
+
+func (c *RequestHeaderAuthRequestController) ExtraHeaderPrefixes() []string {
+	return c.loadRequestHeaderFor(c.extraHeaderPrefixesKey)
+}
+
+func (c *RequestHeaderAuthRequestController) AllowedClientNames() []string {
+	return c.loadRequestHeaderFor(c.allowedClientNamesKey)
+}
+
+// Run starts RequestHeaderAuthRequestController controller and blocks until stopCh is closed.
+func (c *RequestHeaderAuthRequestController) Run(workers int, stopCh <-chan struct{}) {
+	defer utilruntime.HandleCrash()
+	defer c.queue.ShutDown()
+
+	klog.Infof("Starting %s", c.name)
+	defer klog.Infof("Shutting down %s", c.name)
+
+	// wait for caches to fill before starting your work
+	if !cache.WaitForNamedCacheSync(c.name, stopCh, c.configmapInformerSynced) {
+		return
+	}
+
+	// doesn't matter what workers say, only start one.
+	go wait.Until(c.runWorker, time.Second, stopCh)
+
+	<-stopCh
+}
+
+func (c *RequestHeaderAuthRequestController) runWorker() {
+	for c.processNextWorkItem() {
+	}
+}
+
+func (c *RequestHeaderAuthRequestController) processNextWorkItem() bool {
+	dsKey, quit := c.queue.Get()
+	if quit {
+		return false
+	}
+	defer c.queue.Done(dsKey)
+
+	err := c.sync()
+	if err == nil {
+		c.queue.Forget(dsKey)
+		return true
+	}
+
+	utilruntime.HandleError(fmt.Errorf("%v failed with : %v", dsKey, err))
+	c.queue.AddRateLimited(dsKey)
+
+	return true
+}
+
+func (c *RequestHeaderAuthRequestController) syncOnce(client kubernetes.Interface) error {
+	configMap, err := client.CoreV1().ConfigMaps(c.configmapNamespace).Get(context.TODO(), c.configmapName, metav1.GetOptions{})
+	switch {
+	case errors.IsNotFound(err):
+		// ignore, authConfigMap is nil now
+		return nil
+	case errors.IsForbidden(err):
+		klog.Warningf("Unable to get configmap/%s in %s.  Usually fixed by "+
+			"'kubectl create rolebinding -n %s ROLEBINDING_NAME --role=%s --serviceaccount=YOUR_NS:YOUR_SA'",
+			c.configmapName, c.configmapNamespace, c.configmapNamespace, authenticationRoleName)
+		return err
+	case err != nil:
+		return err
+	}
+	return c.syncConfigMap(configMap)
+}
+
+// sync reads the config and propagates the changes to exportedRequestHeaderBundle
+// which is exposed by the set of methods that are used to fill RequestHeaderConfig struct
+func (c *RequestHeaderAuthRequestController) sync() error {
+	configMap, err := c.configmapLister.Get(c.configmapName)
+	if err != nil {
+		return err
+	}
+	return c.syncConfigMap(configMap)
+}
+
+func (c *RequestHeaderAuthRequestController) syncConfigMap(configMap *corev1.ConfigMap) error {
+	hasChanged, newRequestHeaderBundle, err := c.hasRequestHeaderBundleChanged(configMap)
+	if err != nil {
+		return err
+	}
+	if hasChanged {
+		c.exportedRequestHeaderBundle.Store(newRequestHeaderBundle)
+	}
+	return nil
+}
+
+func (c *RequestHeaderAuthRequestController) hasRequestHeaderBundleChanged(cm *corev1.ConfigMap) (bool, *requestHeaderBundle, error) {
+	currentHeadersBundle, err := c.getRequestHeaderBundleFromConfigMap(cm)
+	if err != nil {
+		return false, nil, err
+	}
+
+	rawHeaderBundle := c.exportedRequestHeaderBundle.Load()
+	if rawHeaderBundle == nil {
+		return true, currentHeadersBundle, nil
+	}
+
+	// check to see if we have a change. If the values are the same, do nothing.
+	loadedHeadersBundle, ok := rawHeaderBundle.(*requestHeaderBundle)
+	if !ok {
+		return true, currentHeadersBundle, nil
+	}
+
+	if !equality.Semantic.DeepEqual(loadedHeadersBundle, currentHeadersBundle) {
+		return true, currentHeadersBundle, nil
+	}
+	return false, nil, nil
+}
+
+func (c *RequestHeaderAuthRequestController) getRequestHeaderBundleFromConfigMap(cm *corev1.ConfigMap) (*requestHeaderBundle, error) {
+	usernameHeaderCurrentValue, err := deserializeStrings(cm.Data[c.usernameHeadersKey])
+	if err != nil {
+		return nil, err
+	}
+
+	groupHeadersCurrentValue, err := deserializeStrings(cm.Data[c.groupHeadersKey])
+	if err != nil {
+		return nil, err
+	}
+
+	extraHeaderPrefixesCurrentValue, err := deserializeStrings(cm.Data[c.extraHeaderPrefixesKey])
+	if err != nil {
+		return nil, err
+
+	}
+
+	allowedClientNamesCurrentValue, err := deserializeStrings(cm.Data[c.allowedClientNamesKey])
+	if err != nil {
+		return nil, err
+	}
+
+	return &requestHeaderBundle{
+		UsernameHeaders:     usernameHeaderCurrentValue,
+		GroupHeaders:        groupHeadersCurrentValue,
+		ExtraHeaderPrefixes: extraHeaderPrefixesCurrentValue,
+		AllowedClientNames:  allowedClientNamesCurrentValue,
+	}, nil
+}
+
+func (c *RequestHeaderAuthRequestController) loadRequestHeaderFor(key string) []string {
+	rawHeaderBundle := c.exportedRequestHeaderBundle.Load()
+	if rawHeaderBundle == nil {
+		return nil // this can happen if we've been unable load data from the apiserver for some reason
+	}
+	headerBundle := rawHeaderBundle.(*requestHeaderBundle)
+
+	switch key {
+	case c.usernameHeadersKey:
+		return headerBundle.UsernameHeaders
+	case c.groupHeadersKey:
+		return headerBundle.GroupHeaders
+	case c.extraHeaderPrefixesKey:
+		return headerBundle.ExtraHeaderPrefixes
+	case c.allowedClientNamesKey:
+		return headerBundle.AllowedClientNames
+	default:
+		return nil
+	}
+}
+
+func (c *RequestHeaderAuthRequestController) keyFn() string {
+	// this format matches DeletionHandlingMetaNamespaceKeyFunc for our single key
+	return c.configmapNamespace + "/" + c.configmapName
+}
+
+func deserializeStrings(in string) ([]string, error) {
+	if len(in) == 0 {
+		return nil, nil
+	}
+	var ret []string
+	if err := json.Unmarshal([]byte(in), &ret); err != nil {
+		return nil, err
+	}
+	return ret, nil
+}