Implement basic admission control framework

cluster/saltbase/salt/kube-apiserver/default

@@ -46,4 +46,9 @@
 {% endif -%}
 {% endif -%}
 
-DAEMON_ARGS="{{daemon_args}} {{address}} {{etcd_servers}} {{ cloud_provider }} --allow_privileged={{pillar['allow_privileged']}} {{portal_net}} {{cert_file}} {{key_file}} {{secure_port}} {{token_auth_file}} {{publicAddressOverride}} {{pillar['log_level']}}"
+{% set admission_control = "" -%}
+{% if grains.admission_control is defined -%}
+ {% set admission_control = "-admission_control=" + grains.admission_control -%}
+{% endif -%}
+
+DAEMON_ARGS="{{daemon_args}} {{address}} {{etcd_servers}} {{ cloud_provider }} {{admission_control}} --allow_privileged={{pillar['allow_privileged']}} {{portal_net}} {{cert_file}} {{key_file}} {{secure_port}} {{token_auth_file}} {{publicAddressOverride}} {{pillar['log_level']}}"

cluster/vagrant/provision-master.sh

@@ -75,6 +75,7 @@ grains:
   cloud_provider: vagrant
   roles:
     - kubernetes-master
+  admission_control: AlwaysAdmit
 EOF
 
 mkdir -p /srv/salt-overlay/pillar

cmd/kube-apiserver/apiserver.go

@@ -27,6 +27,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/apiserver"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/capabilities"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
@@ -63,23 +64,25 @@ var (
 		"File containing x509 Certificate for HTTPS.  (CA cert, if any, concatenated after server cert). "+
 		"If HTTPS serving is enabled, and --tls_cert_file and --tls_private_key_file are not provided, "+
 		"a self-signed certificate and key are generated for the public address and saved to /var/run/kubernetes.")
-	tlsPrivateKeyFile       = flag.String("tls_private_key_file", "", "File containing x509 private key matching --tls_cert_file.")
-	apiPrefix               = flag.String("api_prefix", "/api", "The prefix for API requests on the server. Default '/api'.")
-	storageVersion          = flag.String("storage_version", "", "The version to store resources with. Defaults to server preferred")
-	cloudProvider           = flag.String("cloud_provider", "", "The provider for cloud services.  Empty string for no provider.")
-	cloudConfigFile         = flag.String("cloud_config", "", "The path to the cloud provider configuration file.  Empty string for no configuration file.")
-	healthCheckMinions      = flag.Bool("health_check_minions", true, "If true, health check minions and filter unhealthy ones. Default true.")
-	eventTTL                = flag.Duration("event_ttl", 48*time.Hour, "Amount of time to retain events. Default 2 days.")
-	tokenAuthFile           = flag.String("token_auth_file", "", "If set, the file that will be used to secure the secure port of the API server via token authentication.")
-	authorizationMode       = flag.String("authorization_mode", "AlwaysAllow", "Selects how to do authorization on the secure port.  One of: "+strings.Join(apiserver.AuthorizationModeChoices, ","))
-	authorizationPolicyFile = flag.String("authorization_policy_file", "", "File with authorization policy in csv format, used with --authorization_mode=ABAC, on the secure port.")
-	etcdServerList          util.StringList
-	etcdConfigFile          = flag.String("etcd_config", "", "The config file for the etcd client. Mutually exclusive with -etcd_servers.")
-	corsAllowedOriginList   util.StringList
-	allowPrivileged         = flag.Bool("allow_privileged", false, "If true, allow privileged containers.")
-	portalNet               util.IPNet // TODO: make this a list
-	enableLogsSupport       = flag.Bool("enable_logs_support", true, "Enables server endpoint for log collection")
-	kubeletConfig           = client.KubeletConfig{
+	tlsPrivateKeyFile          = flag.String("tls_private_key_file", "", "File containing x509 private key matching --tls_cert_file.")
+	apiPrefix                  = flag.String("api_prefix", "/api", "The prefix for API requests on the server. Default '/api'.")
+	storageVersion             = flag.String("storage_version", "", "The version to store resources with. Defaults to server preferred")
+	cloudProvider              = flag.String("cloud_provider", "", "The provider for cloud services.  Empty string for no provider.")
+	cloudConfigFile            = flag.String("cloud_config", "", "The path to the cloud provider configuration file.  Empty string for no configuration file.")
+	healthCheckMinions         = flag.Bool("health_check_minions", true, "If true, health check minions and filter unhealthy ones. Default true.")
+	eventTTL                   = flag.Duration("event_ttl", 48*time.Hour, "Amount of time to retain events. Default 2 days.")
+	tokenAuthFile              = flag.String("token_auth_file", "", "If set, the file that will be used to secure the secure port of the API server via token authentication.")
+	authorizationMode          = flag.String("authorization_mode", "AlwaysAllow", "Selects how to do authorization on the secure port.  One of: "+strings.Join(apiserver.AuthorizationModeChoices, ","))
+	authorizationPolicyFile    = flag.String("authorization_policy_file", "", "File with authorization policy in csv format, used with --authorization_mode=ABAC, on the secure port.")
+	admissionControl           = flag.String("admission_control", "AlwaysAdmit", "Ordered list of plug-ins to do admission control of resources into cluster. Comma-delimited list of: "+strings.Join(admission.GetPlugins(), ", "))
+	admissionControlConfigFile = flag.String("admission_control_config_file", "", "File with admission control configuration.")
+	etcdServerList             util.StringList
+	etcdConfigFile             = flag.String("etcd_config", "", "The config file for the etcd client. Mutually exclusive with -etcd_servers.")
+	corsAllowedOriginList      util.StringList
+	allowPrivileged            = flag.Bool("allow_privileged", false, "If true, allow privileged containers.")
+	portalNet                  util.IPNet // TODO: make this a list
+	enableLogsSupport          = flag.Bool("enable_logs_support", true, "Enables server endpoint for log collection")
+	kubeletConfig              = client.KubeletConfig{
 		Port:        10250,
 		EnableHttps: false,
 	}
@@ -164,6 +167,9 @@ func main() {
 		glog.Fatalf("Invalid Authorization Config: %v", err)
 	}
 
+	admissionControlPluginNames := strings.Split(*admissionControl, ",")
+	admissionController := admission.NewAdmissionControl(client, admissionControlPluginNames, *admissionControlConfigFile)
+
 	config := &master.Config{
 		Client:                client,
 		Cloud:                 cloud,
@@ -182,6 +188,7 @@ func main() {
 		PublicAddress:         *publicAddressOverride,
 		Authenticator:         authenticator,
 		Authorizer:            authorizer,
+		AdmissionControl:      admissionController,
 	}
 	m := master.New(config)
 

cmd/kube-apiserver/plugins.go

@@ -25,4 +25,7 @@ import (
 	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/openstack"
 	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/ovirt"
 	_ "github.com/GoogleCloudPlatform/kubernetes/pkg/cloudprovider/vagrant"
+
+	_ "github.com/GoogleCloudPlatform/kubernetes/plugin/pkg/admission/admit"
+	_ "github.com/GoogleCloudPlatform/kubernetes/plugin/pkg/admission/deny"
 )

pkg/admission/admission_control.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2014 Google Inc. 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 admission
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+)
+
+type admissionController struct {
+	client           client.Interface
+	admissionHandler Interface
+}
+
+func NewAdmissionControl(client client.Interface, pluginNames []string, configFilePath string) AdmissionControl {
+	return &admissionController{
+		client:           client,
+		admissionHandler: newInterface(pluginNames, configFilePath),
+	}
+}
+
+func (ac *admissionController) AdmissionControl(operation, kind, namespace string, object runtime.Object) (err error) {
+	return ac.admissionHandler.Admit(NewAttributesRecord(ac.client, object, namespace, kind, operation))
+}

pkg/admission/attributes.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2014 Google Inc. 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 admission
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+)
+
+type attributesRecord struct {
+	client    client.Interface
+	namespace string
+	kind      string
+	operation string
+	object    runtime.Object
+}
+
+func NewAttributesRecord(client client.Interface, object runtime.Object, namespace, kind, operation string) Attributes {
+	return &attributesRecord{
+		client:    client,
+		namespace: namespace,
+		kind:      kind,
+		operation: operation,
+		object:    object,
+	}
+}
+
+func (record *attributesRecord) GetClient() client.Interface {
+	return record.client
+}
+
+func (record *attributesRecord) GetNamespace() string {
+	return record.namespace
+}
+
+func (record *attributesRecord) GetKind() string {
+	return record.kind
+}
+
+func (record *attributesRecord) GetOperation() string {
+	return record.operation
+}
+
+func (record *attributesRecord) GetObject() runtime.Object {
+	return record.object
+}

pkg/admission/chain.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2014 Google Inc. 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 admission
+
+import ()
+
+// chainAdmissionHandler is an instance of admission.Interface that performs admission control using a chain of admission handlers
+type chainAdmissionHandler []Interface
+
+// New returns an admission.Interface that will enforce admission control decisions
+func newInterface(pluginNames []string, configFilePath string) Interface {
+	plugins := []Interface{}
+	for _, pluginName := range pluginNames {
+		plugin := InitPlugin(pluginName, configFilePath)
+		if plugin != nil {
+			plugins = append(plugins, plugin)
+		}
+	}
+	return chainAdmissionHandler(plugins)
+}
+
+// Admit performs an admission control check using a chain of handlers, and returns immediately on first error
+func (admissionHandler chainAdmissionHandler) Admit(a Attributes) (err error) {
+	for _, handler := range admissionHandler {
+		err := handler.Admit(a)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

pkg/admission/interfaces.go

@@ -0,0 +1,43 @@
+/*
+Copyright 2014 Google Inc. 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 admission
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+)
+
+// Attributes is an interface used by AdmissionController to get information about a request
+// that is used to make an admission decision.
+type Attributes interface {
+	GetClient() client.Interface
+	GetNamespace() string
+	GetKind() string
+	GetOperation() string
+	GetObject() runtime.Object
+}
+
+// Interface is an abstract, pluggable interface for Admission Control decisions.
+type Interface interface {
+	// Admit makes an admission decision based on the request attributes
+	Admit(a Attributes) (err error)
+}
+
+// AdmissionControl is responsible for performing Admission control decisions
+type AdmissionControl interface {
+	AdmissionControl(operation, kind, namespace string, object runtime.Object) (err error)
+}

pkg/admission/plugins.go

@@ -0,0 +1,106 @@
+/*
+Copyright 2014 Google Inc. 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 admission
+
+import (
+	"io"
+	"os"
+	"sync"
+
+	"github.com/golang/glog"
+)
+
+// Factory is a function that returns a Interface for admission decisions.
+// The config parameter provides an io.Reader handler to the factory in
+// order to load specific configurations. If no configuration is provided
+// the parameter is nil.
+type Factory func(config io.Reader) (Interface, error)
+
+// All registered admission options.
+var pluginsMutex sync.Mutex
+var plugins = make(map[string]Factory)
+
+// GetPlugins enumerates the
+func GetPlugins() []string {
+	pluginsMutex.Lock()
+	defer pluginsMutex.Unlock()
+	keys := []string{}
+	for k := range plugins {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+// RegisterPlugin registers a plugin Factory by name.  This
+// is expected to happen during app startup.
+func RegisterPlugin(name string, plugin Factory) {
+	pluginsMutex.Lock()
+	defer pluginsMutex.Unlock()
+	_, found := plugins[name]
+	if found {
+		glog.Fatalf("Admission plugin %q was registered twice", name)
+	}
+	glog.V(1).Infof("Registered admission plugin %q", name)
+	plugins[name] = plugin
+}
+
+// GetInterface creates an instance of the named plugin, or nil if
+// the name is not known.  The error return is only used if the named provider
+// was known but failed to initialize. The config parameter specifies the
+// io.Reader handler of the configuration file for the cloud provider, or nil
+// for no configuation.
+func GetPlugin(name string, config io.Reader) (Interface, error) {
+	pluginsMutex.Lock()
+	defer pluginsMutex.Unlock()
+	f, found := plugins[name]
+	if !found {
+		return nil, nil
+	}
+	return f(config)
+}
+
+// InitPlugin creates an instance of the named interface
+func InitPlugin(name string, configFilePath string) Interface {
+	var config *os.File
+
+	if name == "" {
+		glog.Info("No admission plugin specified.")
+		return nil
+	}
+
+	if configFilePath != "" {
+		var err error
+
+		config, err = os.Open(configFilePath)
+		if err != nil {
+			glog.Fatalf("Couldn't open admission plugin configuration %s: %#v",
+				configFilePath, err)
+		}
+
+		defer config.Close()
+	}
+
+	plugin, err := GetPlugin(name, config)
+	if err != nil {
+		glog.Fatalf("Couldn't init admission plugin %q: %v", name, err)
+	}
+	if plugin == nil {
+		glog.Fatalf("Unknown admission plugin: %s", name)
+	}
+
+	return plugin
+}

pkg/apiserver/apiserver.go

@@ -27,6 +27,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/healthz"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
@@ -55,9 +56,9 @@ const (
 // Handle returns a Handler function that exposes the provided storage interfaces
 // as RESTful resources at prefix, serialized by codec, and also includes the support
 // http resources.
-func Handle(storage map[string]RESTStorage, codec runtime.Codec, root string, version string, selfLinker runtime.SelfLinker) http.Handler {
+func Handle(storage map[string]RESTStorage, codec runtime.Codec, root string, version string, selfLinker runtime.SelfLinker, admissionControl admission.AdmissionControl) http.Handler {
 	prefix := root + "/" + version
-	group := NewAPIGroupVersion(storage, codec, prefix, selfLinker)
+	group := NewAPIGroupVersion(storage, codec, prefix, selfLinker, admissionControl)
 	container := restful.NewContainer()
 	mux := container.ServeMux
 	group.InstallREST(container, root, version)
@@ -83,13 +84,14 @@ type APIGroupVersion struct {
 // This is a helper method for registering multiple sets of REST handlers under different
 // prefixes onto a server.
 // TODO: add multitype codec serialization
-func NewAPIGroupVersion(storage map[string]RESTStorage, codec runtime.Codec, canonicalPrefix string, selfLinker runtime.SelfLinker) *APIGroupVersion {
+func NewAPIGroupVersion(storage map[string]RESTStorage, codec runtime.Codec, canonicalPrefix string, selfLinker runtime.SelfLinker, admissionControl admission.AdmissionControl) *APIGroupVersion {
 	return &APIGroupVersion{RESTHandler{
-		storage:         storage,
-		codec:           codec,
-		canonicalPrefix: canonicalPrefix,
-		selfLinker:      selfLinker,
-		ops:             NewOperations(),
+		storage:          storage,
+		codec:            codec,
+		canonicalPrefix:  canonicalPrefix,
+		selfLinker:       selfLinker,
+		ops:              NewOperations(),
+		admissionControl: admissionControl,
 		// Delay just long enough to handle most simple write operations
 		asyncOpWait: time.Millisecond * 25,
 	}}

pkg/apiserver/apiserver_test.go

@@ -30,6 +30,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	apierrs "github.com/GoogleCloudPlatform/kubernetes/pkg/api/errors"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/meta"
@@ -38,6 +39,7 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/version"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
+	"github.com/GoogleCloudPlatform/kubernetes/plugin/pkg/admission/admit"
 )
 
 func convert(obj runtime.Object) (runtime.Object, error) {
@@ -53,6 +55,7 @@ var accessor = meta.NewAccessor()
 var versioner runtime.ResourceVersioner = accessor
 var selfLinker runtime.SelfLinker = accessor
 var mapper meta.RESTMapper
+var admissionHandler admission.Interface
 
 func interfacesFor(version string) (*meta.VersionInterfaces, error) {
 	switch version {
@@ -92,6 +95,7 @@ func init() {
 	)
 	defMapper.Add(api.Scheme, true, versions...)
 	mapper = defMapper
+	admissionHandler = admit.NewAlwaysAdmit()
 }
 
 type Simple struct {
@@ -262,7 +266,7 @@ func TestNotFound(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": &SimpleRESTStorage{},
-	}, codec, "/prefix", testVersion, selfLinker)
+	}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 	client := http.Client{}
@@ -284,7 +288,7 @@ func TestNotFound(t *testing.T) {
 }
 
 func TestVersion(t *testing.T) {
-	handler := Handle(map[string]RESTStorage{}, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(map[string]RESTStorage{}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 	client := http.Client{}
@@ -319,7 +323,7 @@ func TestSimpleList(t *testing.T) {
 		namespace:   "other",
 		expectedSet: "/prefix/version/simple?namespace=other",
 	}
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -342,7 +346,7 @@ func TestErrorList(t *testing.T) {
 		errors: map[string]error{"list": fmt.Errorf("test Error")},
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -368,7 +372,7 @@ func TestNonEmptyList(t *testing.T) {
 		},
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -414,7 +418,7 @@ func TestGet(t *testing.T) {
 		expectedSet: "/prefix/version/simple/id",
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -439,7 +443,7 @@ func TestGetMissing(t *testing.T) {
 		errors: map[string]error{"get": apierrs.NewNotFound("simple", "id")},
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -458,7 +462,7 @@ func TestDelete(t *testing.T) {
 	simpleStorage := SimpleRESTStorage{}
 	ID := "id"
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -481,7 +485,7 @@ func TestDeleteMissing(t *testing.T) {
 		errors: map[string]error{"delete": apierrs.NewNotFound("simple", ID)},
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -506,7 +510,7 @@ func TestUpdate(t *testing.T) {
 		t:           t,
 		expectedSet: "/prefix/version/simple/" + ID,
 	}
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -541,7 +545,7 @@ func TestUpdateMissing(t *testing.T) {
 		errors: map[string]error{"update": apierrs.NewNotFound("simple", ID)},
 	}
 	storage["simple"] = &simpleStorage
-	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(storage, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -576,7 +580,7 @@ func TestCreate(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/prefix", testVersion, selfLinker)
+	}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	handler.(*defaultAPIServer).group.handler.asyncOpWait = 0
 	server := httptest.NewServer(handler)
 	defer server.Close()
@@ -619,7 +623,7 @@ func TestCreateNotFound(t *testing.T) {
 			// See https://github.com/GoogleCloudPlatform/kubernetes/pull/486#discussion_r15037092.
 			errors: map[string]error{"create": apierrs.NewNotFound("simple", "id")},
 		},
-	}, codec, "/prefix", testVersion, selfLinker)
+	}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 	client := http.Client{}
@@ -760,7 +764,7 @@ func TestAsyncDelayReturnsError(t *testing.T) {
 			return nil, apierrs.NewAlreadyExists("foo", "bar")
 		},
 	}
-	handler := Handle(map[string]RESTStorage{"foo": &storage}, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(map[string]RESTStorage{"foo": &storage}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	handler.(*defaultAPIServer).group.handler.asyncOpWait = time.Millisecond / 2
 	server := httptest.NewServer(handler)
 	defer server.Close()
@@ -784,7 +788,7 @@ func TestAsyncCreateError(t *testing.T) {
 		name:        "bar",
 		expectedSet: "/prefix/version/foo/bar",
 	}
-	handler := Handle(map[string]RESTStorage{"foo": &storage}, codec, "/prefix", testVersion, selfLinker)
+	handler := Handle(map[string]RESTStorage{"foo": &storage}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	handler.(*defaultAPIServer).group.handler.asyncOpWait = 0
 	server := httptest.NewServer(handler)
 	defer server.Close()
@@ -884,7 +888,7 @@ func TestSyncCreateTimeout(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": &storage,
-	}, codec, "/prefix", testVersion, selfLinker)
+	}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -916,7 +920,7 @@ func TestCORSAllowedOrigins(t *testing.T) {
 		}
 
 		handler := CORS(
-			Handle(map[string]RESTStorage{}, codec, "/prefix", testVersion, selfLinker),
+			Handle(map[string]RESTStorage{}, codec, "/prefix", testVersion, selfLinker, admissionHandler)
 			allowedOriginRegexps, nil, nil, "true",
 		)
 		server := httptest.NewServer(handler)

pkg/apiserver/operation_test.go

@@ -113,7 +113,7 @@ func TestOperationsList(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/prefix", "version", selfLinker)
+	}, codec, "/prefix", "version", selfLinker, admissionHandler)
 	handler.(*defaultAPIServer).group.handler.asyncOpWait = 0
 	server := httptest.NewServer(handler)
 	defer server.Close()
@@ -170,7 +170,7 @@ func TestOpGet(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/prefix", "version", selfLinker)
+	}, codec, "/prefix", "version", selfLinker, admissionHandler)
 	handler.(*defaultAPIServer).group.handler.asyncOpWait = 0
 	server := httptest.NewServer(handler)
 	defer server.Close()

pkg/apiserver/proxy_test.go

@@ -182,7 +182,7 @@ func TestProxy(t *testing.T) {
 		}
 		handler := Handle(map[string]RESTStorage{
 			"foo": simpleStorage,
-		}, codec, "/prefix", "version", selfLinker)
+		}, codec, "/prefix", "version", selfLinker, admissionHandler)
 		server := httptest.NewServer(handler)
 		defer server.Close()
 

pkg/apiserver/redirect_test.go

@@ -31,7 +31,7 @@ func TestRedirect(t *testing.T) {
 	}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/prefix", "version", selfLinker)
+	}, codec, "/prefix", "version", selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 

pkg/apiserver/resthandler.go

@@ -21,6 +21,7 @@ import (
 	"path"
 	"time"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/httplog"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
@@ -31,12 +32,13 @@ import (
 
 // RESTHandler implements HTTP verbs on a set of RESTful resources identified by name.
 type RESTHandler struct {
-	storage         map[string]RESTStorage
-	codec           runtime.Codec
-	canonicalPrefix string
-	selfLinker      runtime.SelfLinker
-	ops             *Operations
-	asyncOpWait     time.Duration
+	storage          map[string]RESTStorage
+	codec            runtime.Codec
+	canonicalPrefix  string
+	selfLinker       runtime.SelfLinker
+	ops              *Operations
+	asyncOpWait      time.Duration
+	admissionControl admission.AdmissionControl
 }
 
 // ServeHTTP handles requests to all RESTStorage objects.
@@ -205,6 +207,14 @@ func (h *RESTHandler) handleRESTStorage(parts []string, req *http.Request, w htt
 			errorJSON(err, h.codec, w)
 			return
 		}
+
+		// invoke admission control
+		err = h.admissionControl.AdmissionControl("CREATE", parts[0], namespace, obj)
+		if err != nil {
+			errorJSON(err, h.codec, w)
+			return
+		}
+
 		out, err := storage.Create(ctx, obj)
 		if err != nil {
 			errorJSON(err, h.codec, w)
@@ -218,6 +228,14 @@ func (h *RESTHandler) handleRESTStorage(parts []string, req *http.Request, w htt
 			notFound(w, req)
 			return
 		}
+
+		// invoke admission control
+		err := h.admissionControl.AdmissionControl("DELETE", parts[0], namespace, nil)
+		if err != nil {
+			errorJSON(err, h.codec, w)
+			return
+		}
+
 		out, err := storage.Delete(ctx, parts[1])
 		if err != nil {
 			errorJSON(err, h.codec, w)
@@ -242,6 +260,14 @@ func (h *RESTHandler) handleRESTStorage(parts []string, req *http.Request, w htt
 			errorJSON(err, h.codec, w)
 			return
 		}
+
+		// invoke admission control
+		err = h.admissionControl.AdmissionControl("UPDATE", parts[0], namespace, obj)
+		if err != nil {
+			errorJSON(err, h.codec, w)
+			return
+		}
+
 		out, err := storage.Update(ctx, obj)
 		if err != nil {
 			errorJSON(err, h.codec, w)

pkg/apiserver/watch_test.go

@@ -50,7 +50,7 @@ func TestWatchWebsocket(t *testing.T) {
 	_ = ResourceWatcher(simpleStorage) // Give compile error if this doesn't work.
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/api", "version", selfLinker)
+	}, codec, "/api", "version", selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -104,7 +104,7 @@ func TestWatchHTTP(t *testing.T) {
 	simpleStorage := &SimpleRESTStorage{}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/api", "version", selfLinker)
+	}, codec, "/api", "version", selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 	client := http.Client{}
@@ -167,7 +167,7 @@ func TestWatchParamParsing(t *testing.T) {
 	simpleStorage := &SimpleRESTStorage{}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/api", "version", selfLinker)
+	}, codec, "/api", "version", selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 
@@ -239,7 +239,7 @@ func TestWatchProtocolSelection(t *testing.T) {
 	simpleStorage := &SimpleRESTStorage{}
 	handler := Handle(map[string]RESTStorage{
 		"foo": simpleStorage,
-	}, codec, "/api", "version", selfLinker)
+	}, codec, "/api", "version", selfLinker, admissionHandler)
 	server := httptest.NewServer(handler)
 	defer server.Close()
 	defer server.CloseClientConnections()

pkg/master/master.go

@@ -28,6 +28,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/v1beta1"
@@ -75,6 +76,7 @@ type Config struct {
 	CorsAllowedOriginList util.StringList
 	Authenticator         authenticator.Request
 	Authorizer            authorizer.Authorizer
+	AdmissionControl      admission.AdmissionControl
 
 	// If specified, all web services will be registered into this container
 	RestfulContainer *restful.Container
@@ -118,6 +120,7 @@ type Master struct {
 	corsAllowedOriginList util.StringList
 	authenticator         authenticator.Request
 	authorizer            authorizer.Authorizer
+	admissionControl      admission.AdmissionControl
 	masterCount           int
 
 	readOnlyServer  string
@@ -248,6 +251,7 @@ func New(c *Config) *Master {
 		corsAllowedOriginList: c.CorsAllowedOriginList,
 		authenticator:         c.Authenticator,
 		authorizer:            c.Authorizer,
+		admissionControl:      c.AdmissionControl,
 
 		masterCount:     c.MasterCount,
 		readOnlyServer:  net.JoinHostPort(c.PublicAddress, strconv.Itoa(int(c.ReadOnlyPort))),
@@ -462,19 +466,19 @@ func (m *Master) getServersToValidate(c *Config) map[string]apiserver.Server {
 }
 
 // API_v1beta1 returns the resources and codec for API version v1beta1.
-func (m *Master) API_v1beta1() (map[string]apiserver.RESTStorage, runtime.Codec, string, runtime.SelfLinker) {
+func (m *Master) API_v1beta1() (map[string]apiserver.RESTStorage, runtime.Codec, string, runtime.SelfLinker, admission.AdmissionControl) {
 	storage := make(map[string]apiserver.RESTStorage)
 	for k, v := range m.storage {
 		storage[k] = v
 	}
-	return storage, v1beta1.Codec, "/api/v1beta1", latest.SelfLinker
+	return storage, v1beta1.Codec, "/api/v1beta1", latest.SelfLinker, m.admissionControl
 }
 
 // API_v1beta2 returns the resources and codec for API version v1beta2.
-func (m *Master) API_v1beta2() (map[string]apiserver.RESTStorage, runtime.Codec, string, runtime.SelfLinker) {
+func (m *Master) API_v1beta2() (map[string]apiserver.RESTStorage, runtime.Codec, string, runtime.SelfLinker, admission.AdmissionControl) {
 	storage := make(map[string]apiserver.RESTStorage)
 	for k, v := range m.storage {
 		storage[k] = v
 	}
-	return storage, v1beta2.Codec, "/api/v1beta2", latest.SelfLinker
+	return storage, v1beta2.Codec, "/api/v1beta2", latest.SelfLinker, m.admissionControl
 }

plugin/pkg/admission/admit/admission.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2014 Google Inc. 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 admit
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
+	"io"
+)
+
+func init() {
+	admission.RegisterPlugin("AlwaysAdmit", func(config io.Reader) (admission.Interface, error) { return NewAlwaysAdmit(), nil })
+}
+
+// alwaysAdmit is an implementation of admission.Interface which always says yes to an admit request.
+// It is useful in tests and when using kubernetes in an open manner.
+type alwaysAdmit struct{}
+
+func (alwaysAdmit) Admit(a admission.Attributes) (err error) {
+	return nil
+}
+
+func NewAlwaysAdmit() admission.Interface {
+	return new(alwaysAdmit)
+}

plugin/pkg/admission/deny/admission.go

@@ -0,0 +1,39 @@
+/*
+Copyright 2014 Google Inc. 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 deny
+
+import (
+	"errors"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
+	"io"
+)
+
+func init() {
+	admission.RegisterPlugin("AlwaysDeny", func(config io.Reader) (admission.Interface, error) { return NewAlwaysDeny(), nil })
+}
+
+// alwaysDeny is an implementation of admission.Interface which always says no to an admission request.
+// It is useful in unit tests to force an operation to be forbidden.
+type alwaysDeny struct{}
+
+func (alwaysDeny) Admit(a admission.Attributes) (err error) {
+	return errors.New("You shall not pass!")
+}
+
+func NewAlwaysDeny() admission.Interface {
+	return new(alwaysDeny)
+}