Add new admission controller: image policy webhook

hack/.linted_packages

@@ -169,6 +169,7 @@ plugin/pkg/admission/admit
 plugin/pkg/admission/alwayspullimages
 plugin/pkg/admission/deny
 plugin/pkg/admission/exec
+plugin/pkg/admission/imagepolicy
 plugin/pkg/admission/namespace/autoprovision
 plugin/pkg/admission/namespace/exists
 plugin/pkg/admission/securitycontext/scdeny
@@ -202,4 +203,4 @@ pkg/util/maps
 pkg/volume/quobyte
 test/integration/discoverysummarizer
 test/integration/examples
-test/integration/federation
+test/integration/federation
\ No newline at end of file

plugin/pkg/admission/imagepolicy/admission.go

+/*
+Copyright 2016 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 imagepolicy contains an admission controller that configures a webhook to which policy
+// decisions are delegated.
+package imagepolicy
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/golang/glog"
+
+	"k8s.io/kubernetes/pkg/api"
+	apierrors "k8s.io/kubernetes/pkg/api/errors"
+	"k8s.io/kubernetes/pkg/api/unversioned"
+	"k8s.io/kubernetes/pkg/apis/imagepolicy/v1alpha1"
+	clientset "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
+	"k8s.io/kubernetes/pkg/util/yaml"
+
+	"k8s.io/kubernetes/pkg/client/restclient"
+	"k8s.io/kubernetes/pkg/util/cache"
+	"k8s.io/kubernetes/plugin/pkg/webhook"
+
+	"k8s.io/kubernetes/pkg/admission"
+)
+
+var (
+	groupVersions = []unversioned.GroupVersion{v1alpha1.SchemeGroupVersion}
+)
+
+func init() {
+	admission.RegisterPlugin("ImagePolicyWebhook", func(client clientset.Interface, config io.Reader) (admission.Interface, error) {
+		newImagePolicyWebhook, err := NewImagePolicyWebhook(client, config)
+		if err != nil {
+			return nil, err
+		}
+		return newImagePolicyWebhook, nil
+	})
+}
+
+// imagePolicyWebhook is an implementation of admission.Interface.
+type imagePolicyWebhook struct {
+	*admission.Handler
+	webhook       *webhook.GenericWebhook
+	responseCache *cache.LRUExpireCache
+	allowTTL      time.Duration
+	denyTTL       time.Duration
+	retryBackoff  time.Duration
+	defaultAllow  bool
+}
+
+func (a *imagePolicyWebhook) statusTTL(status v1alpha1.ImageReviewStatus) time.Duration {
+	if status.Allowed {
+		return a.allowTTL
+	}
+	return a.denyTTL
+}
+
+// Filter out annotations that don't match *.image-policy.k8s.io/*
+func (a *imagePolicyWebhook) filterAnnotations(allAnnotations map[string]string) map[string]string {
+	annotations := make(map[string]string)
+	for k, v := range allAnnotations {
+		if strings.Contains(k, ".image-policy.k8s.io/") {
+			annotations[k] = v
+		}
+	}
+	return annotations
+}
+
+// Function to call on webhook failure; behavior determined by defaultAllow flag
+func (a *imagePolicyWebhook) webhookError(attributes admission.Attributes, err error) error {
+	if err != nil {
+		glog.V(2).Infof("error contacting webhook backend: %s")
+		if a.defaultAllow {
+			glog.V(2).Infof("resource allowed in spite of webhook backend failure")
+			return nil
+		}
+		glog.V(2).Infof("resource not allowed due to webhook backend failure ")
+		return admission.NewForbidden(attributes, err)
+	}
+	return nil
+}
+
+func (a *imagePolicyWebhook) Admit(attributes admission.Attributes) (err error) {
+	// Ignore all calls to subresources or resources other than pods.
+	allowedResources := map[unversioned.GroupResource]bool{
+		api.Resource("pods"): true,
+	}
+
+	if len(attributes.GetSubresource()) != 0 || !allowedResources[attributes.GetResource().GroupResource()] {
+		return nil
+	}
+
+	pod, ok := attributes.GetObject().(*api.Pod)
+	if !ok {
+		return apierrors.NewBadRequest("Resource was marked with kind Pod but was unable to be converted")
+	}
+
+	// Build list of ImageReviewContainerSpec
+	var imageReviewContainerSpecs []v1alpha1.ImageReviewContainerSpec
+	containers := make([]api.Container, 0, len(pod.Spec.Containers)+len(pod.Spec.InitContainers))
+	containers = append(containers, pod.Spec.Containers...)
+	containers = append(containers, pod.Spec.InitContainers...)
+	for _, c := range containers {
+		imageReviewContainerSpecs = append(imageReviewContainerSpecs, v1alpha1.ImageReviewContainerSpec{
+			Image: c.Image,
+		})
+	}
+	imageReview := v1alpha1.ImageReview{
+		Spec: v1alpha1.ImageReviewSpec{
+			Containers:  imageReviewContainerSpecs,
+			Annotations: a.filterAnnotations(pod.Annotations),
+			Namespace:   attributes.GetNamespace(),
+		},
+	}
+	if err := a.admitPod(attributes, &imageReview); err != nil {
+		return admission.NewForbidden(attributes, err)
+	}
+	return nil
+}
+
+func (a *imagePolicyWebhook) admitPod(attributes admission.Attributes, review *v1alpha1.ImageReview) error {
+	cacheKey, err := json.Marshal(review.Spec)
+	if err != nil {
+		return err
+	}
+	if entry, ok := a.responseCache.Get(string(cacheKey)); ok {
+		review.Status = entry.(v1alpha1.ImageReviewStatus)
+	} else {
+		result := a.webhook.WithExponentialBackoff(func() restclient.Result {
+			return a.webhook.RestClient.Post().Body(review).Do()
+		})
+
+		if err := result.Error(); err != nil {
+			return a.webhookError(attributes, err)
+		}
+		var statusCode int
+		if result.StatusCode(&statusCode); statusCode < 200 || statusCode >= 300 {
+			return a.webhookError(attributes, fmt.Errorf("Error contacting webhook: %d", statusCode))
+		}
+
+		if err := result.Into(review); err != nil {
+			return a.webhookError(attributes, err)
+		}
+
+		a.responseCache.Add(string(cacheKey), review.Status, a.statusTTL(review.Status))
+	}
+
+	if !review.Status.Allowed {
+		if len(review.Status.Reason) > 0 {
+			return fmt.Errorf("image policy webook backend denied one or more images: %s", review.Status.Reason)
+		}
+		return errors.New("one or more images rejected by webhook backend")
+	}
+
+	return nil
+}
+
+// NewImagePolicyWebhook a new imagePolicyWebhook from the provided config file.
+// The config file is specified by --admission-controller-config-file and has the
+// following format for a webhook:
+//
+//   {
+//     "imagePolicy": {
+//        "kubeConfigFile": "path/to/kubeconfig/for/backend",
+//        "allowTTL": 30,           # time in s to cache approval
+//        "denyTTL": 30,            # time in s to cache denial
+//        "retryBackoff": 500,      # time in ms to wait between retries
+//        "defaultAllow": true      # determines behavior if the webhook backend fails
+//     }
+//   }
+//
+// The config file may be json or yaml.
+//
+// The kubeconfig property refers to another file in the kubeconfig format which
+// specifies how to connect to the webhook backend.
+//
+// The kubeconfig's cluster field is used to refer to the remote service, user refers to the returned authorizer.
+//
+//     # clusters refers to the remote service.
+//     clusters:
+//     - name: name-of-remote-imagepolicy-service
+//       cluster:
+//         certificate-authority: /path/to/ca.pem      # CA for verifying the remote service.
+//         server: https://images.example.com/policy # URL of remote service to query. Must use 'https'.
+//
+//     # users refers to the API server's webhook configuration.
+//     users:
+//     - name: name-of-api-server
+//       user:
+//         client-certificate: /path/to/cert.pem # cert for the webhook plugin to use
+//         client-key: /path/to/key.pem          # key matching the cert
+//
+// For additional HTTP configuration, refer to the kubeconfig documentation
+// http://kubernetes.io/v1.1/docs/user-guide/kubeconfig-file.html.
+func NewImagePolicyWebhook(client clientset.Interface, configFile io.Reader) (admission.Interface, error) {
+	var config AdmissionConfig
+	d := yaml.NewYAMLOrJSONDecoder(configFile, 4096)
+	err := d.Decode(&config)
+	if err != nil {
+		return nil, err
+	}
+
+	whConfig := config.ImagePolicyWebhook
+	if err := normalizeWebhookConfig(&whConfig); err != nil {
+		return nil, err
+	}
+
+	gw, err := webhook.NewGenericWebhook(whConfig.KubeConfigFile, groupVersions, whConfig.RetryBackoff)
+	if err != nil {
+		return nil, err
+	}
+	return &imagePolicyWebhook{
+		Handler:       admission.NewHandler(admission.Create, admission.Update),
+		webhook:       gw,
+		responseCache: cache.NewLRUExpireCache(1024),
+		allowTTL:      whConfig.AllowTTL,
+		denyTTL:       whConfig.DenyTTL,
+		defaultAllow:  whConfig.DefaultAllow,
+	}, nil
+}

plugin/pkg/admission/imagepolicy/config.go

+/*
+Copyright 2016 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 imagepolicy contains an admission controller that configures a webhook to which policy
+// decisions are delegated.
+package imagepolicy
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/golang/glog"
+)
+
+const (
+	defaultRetryBackoff = time.Duration(500) * time.Millisecond
+	minRetryBackoff     = time.Duration(1)
+	maxRetryBackoff     = time.Duration(5) * time.Minute
+	defaultAllowTTL     = time.Duration(5) * time.Minute
+	defaultDenyTTL      = time.Duration(30) * time.Second
+	minAllowTTL         = time.Duration(1) * time.Second
+	maxAllowTTL         = time.Duration(30) * time.Minute
+	minDenyTTL          = time.Duration(1) * time.Second
+	maxDenyTTL          = time.Duration(30) * time.Minute
+	useDefault          = time.Duration(0)  //sentinel for using default TTL
+	disableTTL          = time.Duration(-1) //sentinel for disabling a TTL
+)
+
+// imagePolicyWebhookConfig holds config data for imagePolicyWebhook
+type imagePolicyWebhookConfig struct {
+	KubeConfigFile string        `json:"kubeConfigFile"`
+	AllowTTL       time.Duration `json:"allowTTL"`
+	DenyTTL        time.Duration `json:"denyTTL"`
+	RetryBackoff   time.Duration `json:"retryBackoff"`
+	DefaultAllow   bool          `json:"defaultAllow"`
+}
+
+// AdmissionConfig holds config data for admission controllers
+type AdmissionConfig struct {
+	ImagePolicyWebhook imagePolicyWebhookConfig `json:"imagePolicy"`
+}
+
+func normalizeWebhookConfig(config *imagePolicyWebhookConfig) (err error) {
+	config.RetryBackoff, err = normalizeConfigDuration("backoff", time.Millisecond, config.RetryBackoff, minRetryBackoff, maxRetryBackoff, defaultRetryBackoff)
+	if err != nil {
+		return err
+	}
+	config.AllowTTL, err = normalizeConfigDuration("allow cache", time.Second, config.AllowTTL, minAllowTTL, maxAllowTTL, defaultAllowTTL)
+	if err != nil {
+		return err
+	}
+	config.DenyTTL, err = normalizeConfigDuration("deny cache", time.Second, config.DenyTTL, minDenyTTL, maxDenyTTL, defaultDenyTTL)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func normalizeConfigDuration(name string, scale, value, min, max, defaultValue time.Duration) (time.Duration, error) {
+	// disable with -1 sentinel
+	if value == disableTTL {
+		glog.V(2).Infof("image policy webhook %s disabled", name)
+		return time.Duration(0), nil
+	}
+
+	// use defualt with 0 sentinel
+	if value == useDefault {
+		glog.V(2).Infof("image policy webhook %s using default value", name)
+		return defaultValue, nil
+	}
+
+	// convert to s; unmarshalling gives ns
+	value *= scale
+
+	// check value is within range
+	if value <= min || value > max {
+		return value, fmt.Errorf("valid value is between %v and %v, got %v", min, max, value)
+	}
+	return value, nil
+}

plugin/pkg/admission/imagepolicy/config_test.go

+/*
+Copyright 2016 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 imagepolicy
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestConfigNormalization(t *testing.T) {
+	tests := []struct {
+		test             string
+		config           imagePolicyWebhookConfig
+		normalizedConfig imagePolicyWebhookConfig
+		wantErr          bool
+	}{
+		{
+			test: "config within normal ranges",
+			config: imagePolicyWebhookConfig{
+				AllowTTL:     ((minAllowTTL + maxAllowTTL) / 2) / time.Second,
+				DenyTTL:      ((minDenyTTL + maxDenyTTL) / 2) / time.Second,
+				RetryBackoff: ((minRetryBackoff + maxRetryBackoff) / 2) / time.Millisecond,
+			},
+			normalizedConfig: imagePolicyWebhookConfig{
+				AllowTTL:     ((minAllowTTL + maxAllowTTL) / 2) / time.Second * time.Second,
+				DenyTTL:      ((minDenyTTL + maxDenyTTL) / 2) / time.Second * time.Second,
+				RetryBackoff: (minRetryBackoff + maxRetryBackoff) / 2,
+			},
+			wantErr: false,
+		},
+		{
+			test: "config below normal ranges, error",
+			config: imagePolicyWebhookConfig{
+				AllowTTL:     minAllowTTL - time.Duration(1),
+				DenyTTL:      minDenyTTL - time.Duration(1),
+				RetryBackoff: minRetryBackoff - time.Duration(1),
+			},
+			wantErr: true,
+		},
+		{
+			test: "config above normal ranges, error",
+			config: imagePolicyWebhookConfig{
+				AllowTTL:     time.Duration(1) + maxAllowTTL,
+				DenyTTL:      time.Duration(1) + maxDenyTTL,
+				RetryBackoff: time.Duration(1) + maxRetryBackoff,
+			},
+			wantErr: true,
+		},
+		{
+			test: "config wants default values",
+			config: imagePolicyWebhookConfig{
+				AllowTTL:     useDefault,
+				DenyTTL:      useDefault,
+				RetryBackoff: useDefault,
+			},
+			normalizedConfig: imagePolicyWebhookConfig{
+				AllowTTL:     defaultAllowTTL,
+				DenyTTL:      defaultDenyTTL,
+				RetryBackoff: defaultRetryBackoff,
+			},
+			wantErr: false,
+		},
+		{
+			test: "config wants disabled values",
+			config: imagePolicyWebhookConfig{
+				AllowTTL:     disableTTL,
+				DenyTTL:      disableTTL,
+				RetryBackoff: disableTTL,
+			},
+			normalizedConfig: imagePolicyWebhookConfig{
+				AllowTTL:     time.Duration(0),
+				DenyTTL:      time.Duration(0),
+				RetryBackoff: time.Duration(0),
+			},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		err := normalizeWebhookConfig(&tt.config)
+		if err == nil && tt.wantErr == true {
+			t.Errorf("%s: expected error from normalization and didn't have one", tt.test)
+		}
+		if err != nil && tt.wantErr == false {
+			t.Errorf("%s: unexpected error from normalization: %v", tt.test, err)
+		}
+		if err == nil && !reflect.DeepEqual(tt.config, tt.normalizedConfig) {
+			t.Errorf("%s: expected config to be normalized. got: %v expected: %v", tt.test, tt.config, tt.normalizedConfig)
+		}
+	}
+}

plugin/pkg/admission/imagepolicy/doc.go

+/*
+Copyright 2016 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 imagepolicy checks a webhook for image admission
+package imagepolicy // import "k8s.io/kubernetes/plugin/pkg/admission/imagepolicy"

plugin/pkg/admission/imagepolicy/gencerts.sh

+#!/bin/bash
+
+# Copyright 2016 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.
+
+set -e
+
+# gencerts.sh generates the certificates for the webhook authz plugin tests.
+#
+# It is not expected to be run often (there is no go generate rule), and mainly
+# exists for documentation purposes.
+
+cat > server.conf << EOF
+[req]
+req_extensions = v3_req
+distinguished_name = req_distinguished_name
+[req_distinguished_name]
+[ v3_req ]
+basicConstraints = CA:FALSE
+keyUsage = nonRepudiation, digitalSignature, keyEncipherment
+extendedKeyUsage = serverAuth
+subjectAltName = @alt_names
+[alt_names]
+IP.1 = 127.0.0.1
+EOF
+
+cat > client.conf << EOF
+[req]
+req_extensions = v3_req
+distinguished_name = req_distinguished_name
+[req_distinguished_name]
+[ v3_req ]
+basicConstraints = CA:FALSE
+keyUsage = nonRepudiation, digitalSignature, keyEncipherment
+extendedKeyUsage = clientAuth
+EOF
+
+# Create a certificate authority
+openssl genrsa -out caKey.pem 2048
+openssl req -x509 -new -nodes -key caKey.pem -days 100000 -out caCert.pem -subj "/CN=webhook_imagepolicy_ca"
+
+# Create a second certificate authority
+openssl genrsa -out badCAKey.pem 2048
+openssl req -x509 -new -nodes -key badCAKey.pem -days 100000 -out badCACert.pem -subj "/CN=webhook_imagepolicy_ca"
+
+# Create a server certiticate
+openssl genrsa -out serverKey.pem 2048
+openssl req -new -key serverKey.pem -out server.csr -subj "/CN=webhook_imagepolicy_server" -config server.conf
+openssl x509 -req -in server.csr -CA caCert.pem -CAkey caKey.pem -CAcreateserial -out serverCert.pem -days 100000 -extensions v3_req -extfile server.conf
+
+# Create a client certiticate
+openssl genrsa -out clientKey.pem 2048
+openssl req -new -key clientKey.pem -out client.csr -subj "/CN=webhook_imagepolicy_client" -config client.conf
+openssl x509 -req -in client.csr -CA caCert.pem -CAkey caKey.pem -CAcreateserial -out clientCert.pem -days 100000 -extensions v3_req -extfile client.conf
+
+outfile=certs_test.go
+
+cat > $outfile << EOF
+/*
+Copyright 2016 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.
+*/
+
+EOF
+
+echo "// This file was generated using openssl by the gencerts.sh script" >> $outfile
+echo "// and holds raw certificates for the imagepolicy webhook tests." >> $outfile
+echo "" >> $outfile
+echo "package imagepolicy" >> $outfile
+for file in caKey caCert badCAKey badCACert serverKey serverCert clientKey clientCert; do
+	data=$(cat ${file}.pem)
+	echo "" >> $outfile
+	echo "var $file = []byte(\`$data\`)" >> $outfile
+done
+
+# Clean up after we're done.
+rm *.pem
+rm *.csr
+rm *.srl
+rm *.conf