From f754a4dee31455a0d7fc0f51cb85348af9ea5e1f Mon Sep 17 00:00:00 2001
From: Rita Zhang <rita.z.zhang@gmail.com>
Date: Tue, 30 May 2023 20:35:33 +0000
Subject: [PATCH] Add ephemeralcontainer to imagepolicy securityaccount
 admission plugin

Signed-off-by: Rita Zhang <rita.z.zhang@gmail.com>
---
 plugin/pkg/admission/imagepolicy/admission.go |  28 ++--
 .../admission/imagepolicy/admission_test.go   | 148 +++++++++++++++++-
 .../pkg/admission/serviceaccount/admission.go |  57 ++++++-
 .../serviceaccount/admission_test.go          |  88 +++++++++++
 4 files changed, 297 insertions(+), 24 deletions(-)

diff --git a/plugin/pkg/admission/imagepolicy/admission.go b/plugin/pkg/admission/imagepolicy/admission.go
index 80bd4852..34290671 100644
--- a/plugin/pkg/admission/imagepolicy/admission.go
+++ b/plugin/pkg/admission/imagepolicy/admission.go
@@ -46,6 +46,7 @@ import (
 
 // PluginName indicates name of admission plugin.
 const PluginName = "ImagePolicyWebhook"
+const ephemeralcontainers = "ephemeralcontainers"
 
 // AuditKeyPrefix is used as the prefix for all audit keys handled by this
 // pluggin. Some well known suffixes are listed below.
@@ -132,8 +133,9 @@ func (a *Plugin) webhookError(pod *api.Pod, attributes admission.Attributes, err
 
 // Validate makes an admission decision based on the request attributes
 func (a *Plugin) Validate(ctx context.Context, attributes admission.Attributes, o admission.ObjectInterfaces) (err error) {
-	// Ignore all calls to subresources or resources other than pods.
-	if attributes.GetSubresource() != "" || attributes.GetResource().GroupResource() != api.Resource("pods") {
+	// Ignore all calls to subresources other than ephemeralcontainers or calls to resources other than pods.
+	subresource := attributes.GetSubresource()
+	if (subresource != "" && subresource != ephemeralcontainers) || attributes.GetResource().GroupResource() != api.Resource("pods") {
 		return nil
 	}
 
@@ -144,13 +146,21 @@ func (a *Plugin) Validate(ctx context.Context, attributes admission.Attributes,
 
 	// 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,
-		})
+	if subresource == "" {
+		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,
+			})
+		}
+	} else if subresource == ephemeralcontainers {
+		for _, c := range pod.Spec.EphemeralContainers {
+			imageReviewContainerSpecs = append(imageReviewContainerSpecs, v1alpha1.ImageReviewContainerSpec{
+				Image: c.Image,
+			})
+		}
 	}
 	imageReview := v1alpha1.ImageReview{
 		Spec: v1alpha1.ImageReviewSpec{
diff --git a/plugin/pkg/admission/imagepolicy/admission_test.go b/plugin/pkg/admission/imagepolicy/admission_test.go
index d1f81d51..a9188462 100644
--- a/plugin/pkg/admission/imagepolicy/admission_test.go
+++ b/plugin/pkg/admission/imagepolicy/admission_test.go
@@ -37,7 +37,6 @@ import (
 	api "k8s.io/kubernetes/pkg/apis/core"
 
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"text/template"
@@ -67,7 +66,7 @@ imagePolicy:
 `
 
 func TestNewFromConfig(t *testing.T) {
-	dir, err := ioutil.TempDir("", "")
+	dir, err := os.MkdirTemp("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -92,7 +91,7 @@ func TestNewFromConfig(t *testing.T) {
 		{data.Key, clientKey},
 	}
 	for _, file := range files {
-		if err := ioutil.WriteFile(file.name, file.data, 0400); err != nil {
+		if err := os.WriteFile(file.name, file.data, 0400); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -196,7 +195,7 @@ current-context: default
 		// Use a closure so defer statements trigger between loop iterations.
 		t.Run(tt.msg, func(t *testing.T) {
 			err := func() error {
-				tempfile, err := ioutil.TempFile("", "")
+				tempfile, err := os.CreateTemp("", "")
 				if err != nil {
 					return err
 				}
@@ -211,7 +210,7 @@ current-context: default
 					return fmt.Errorf("failed to execute test template: %v", err)
 				}
 
-				tempconfigfile, err := ioutil.TempFile("", "")
+				tempconfigfile, err := os.CreateTemp("", "")
 				if err != nil {
 					return err
 				}
@@ -359,7 +358,7 @@ func (m *mockService) HTTPStatusCode() int { return m.statusCode }
 // newImagePolicyWebhook creates a temporary kubeconfig file from the provided arguments and attempts to load
 // a new newImagePolicyWebhook from it.
 func newImagePolicyWebhook(callbackURL string, clientCert, clientKey, ca []byte, cacheTime time.Duration, defaultAllow bool) (*Plugin, error) {
-	tempfile, err := ioutil.TempFile("", "")
+	tempfile, err := os.CreateTemp("", "")
 	if err != nil {
 		return nil, err
 	}
@@ -381,7 +380,7 @@ func newImagePolicyWebhook(callbackURL string, clientCert, clientKey, ca []byte,
 		return nil, err
 	}
 
-	tempconfigfile, err := ioutil.TempFile("", "")
+	tempconfigfile, err := os.CreateTemp("", "")
 	if err != nil {
 		return nil, err
 	}
@@ -595,17 +594,23 @@ func TestContainerCombinations(t *testing.T) {
 		test                 string
 		pod                  *api.Pod
 		wantAllowed, wantErr bool
+		subresource          string
+		operation            admission.Operation
 	}{
 		{
 			test:        "Single container allowed",
 			pod:         goodPod("good"),
 			wantAllowed: true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test:        "Single container denied",
 			pod:         goodPod("bad"),
 			wantAllowed: false,
 			wantErr:     true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "One good container, one bad",
@@ -627,6 +632,8 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: false,
 			wantErr:     true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "Multiple good containers",
@@ -648,6 +655,8 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: true,
 			wantErr:     false,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "Multiple bad containers",
@@ -669,6 +678,8 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: false,
 			wantErr:     true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "Good container, bad init container",
@@ -692,6 +703,8 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: false,
 			wantErr:     true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "Bad container, good init container",
@@ -715,6 +728,8 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: false,
 			wantErr:     true,
+			subresource: "",
+			operation:   admission.Create,
 		},
 		{
 			test: "Good container, good init container",
@@ -738,6 +753,123 @@ func TestContainerCombinations(t *testing.T) {
 			},
 			wantAllowed: true,
 			wantErr:     false,
+			subresource: "",
+			operation:   admission.Create,
+		},
+		{
+			test: "Good container, good init container, bad ephemeral container when updating ephemeralcontainers subresource",
+			pod: &api.Pod{
+				Spec: api.PodSpec{
+					ServiceAccountName: "default",
+					SecurityContext:    &api.PodSecurityContext{},
+					Containers: []api.Container{
+						{
+							Image:           "good",
+							SecurityContext: &api.SecurityContext{},
+						},
+					},
+					InitContainers: []api.Container{
+						{
+							Image:           "good",
+							SecurityContext: &api.SecurityContext{},
+						},
+					},
+					EphemeralContainers: []api.EphemeralContainer{
+						{
+							EphemeralContainerCommon: api.EphemeralContainerCommon{
+								Image:           "bad",
+								SecurityContext: &api.SecurityContext{},
+							},
+						},
+					},
+				},
+			},
+			wantAllowed: false,
+			wantErr:     true,
+			subresource: "ephemeralcontainers",
+			operation:   admission.Update,
+		},
+		{
+			test: "Good container, good init container, bad ephemeral container when updating subresource=='' which sets initContainer and container only",
+			pod: &api.Pod{
+				Spec: api.PodSpec{
+					ServiceAccountName: "default",
+					SecurityContext:    &api.PodSecurityContext{},
+					Containers: []api.Container{
+						{
+							Image:           "good",
+							SecurityContext: &api.SecurityContext{},
+						},
+					},
+					InitContainers: []api.Container{
+						{
+							Image:           "good",
+							SecurityContext: &api.SecurityContext{},
+						},
+					},
+					EphemeralContainers: []api.EphemeralContainer{
+						{
+							EphemeralContainerCommon: api.EphemeralContainerCommon{
+								Image:           "bad",
+								SecurityContext: &api.SecurityContext{},
+							},
+						},
+					},
+				},
+			},
+			wantAllowed: true,
+			wantErr:     false,
+			subresource: "",
+			operation:   admission.Update,
+		},
+
+		{
+			test: "Bad container, good ephemeral container when updating subresource=='ephemeralcontainers' which sets ephemeralcontainers only",
+			pod: &api.Pod{
+				Spec: api.PodSpec{
+					ServiceAccountName: "default",
+					SecurityContext:    &api.PodSecurityContext{},
+					Containers: []api.Container{
+						{
+							Image:           "bad",
+							SecurityContext: &api.SecurityContext{},
+						},
+					},
+					EphemeralContainers: []api.EphemeralContainer{
+						{
+							EphemeralContainerCommon: api.EphemeralContainerCommon{
+								Image:           "good",
+								SecurityContext: &api.SecurityContext{},
+							},
+						},
+					},
+				},
+			},
+			wantAllowed: true,
+			wantErr:     false,
+			subresource: "ephemeralcontainers",
+			operation:   admission.Update,
+		},
+		{
+			test: "Good ephemeral container",
+			pod: &api.Pod{
+				Spec: api.PodSpec{
+					ServiceAccountName: "default",
+					SecurityContext:    &api.PodSecurityContext{},
+					EphemeralContainers: []api.EphemeralContainer{
+						{
+							EphemeralContainerCommon: api.EphemeralContainerCommon{
+								Image:           "good",
+								SecurityContext: &api.SecurityContext{},
+							},
+						},
+					},
+				},
+			},
+			wantAllowed: true,
+			wantErr:     false,
+			subresource: "ephemeralcontainers",
+			operation:   admission.Update,
 		},
 	}
 	for _, tt := range tests {
@@ -759,7 +891,7 @@ func TestContainerCombinations(t *testing.T) {
 				return
 			}
 
-			attr := admission.NewAttributesRecord(tt.pod, nil, api.Kind("Pod").WithVersion("version"), "namespace", "", api.Resource("pods").WithVersion("version"), "", admission.Create, &metav1.CreateOptions{}, false, &user.DefaultInfo{})
+			attr := admission.NewAttributesRecord(tt.pod, nil, api.Kind("Pod").WithVersion("version"), "namespace", "", api.Resource("pods").WithVersion("version"), tt.subresource, tt.operation, &metav1.CreateOptions{}, false, &user.DefaultInfo{})
 
 			err = wh.Validate(context.TODO(), attr, nil)
 			if tt.wantAllowed {
diff --git a/plugin/pkg/admission/serviceaccount/admission.go b/plugin/pkg/admission/serviceaccount/admission.go
index 6a003f75..38ac66ab 100644
--- a/plugin/pkg/admission/serviceaccount/admission.go
+++ b/plugin/pkg/admission/serviceaccount/admission.go
@@ -109,7 +109,7 @@ var _ = genericadmissioninitializer.WantsExternalKubeInformerFactory(&Plugin{})
 // 5. If MountServiceAccountToken is true, it adds a VolumeMount with the pod's ServiceAccount's api token secret to containers
 func NewServiceAccount() *Plugin {
 	return &Plugin{
-		Handler: admission.NewHandler(admission.Create),
+		Handler: admission.NewHandler(admission.Create, admission.Update),
 		// TODO: enable this once we've swept secret usage to account for adding secret references to service accounts
 		LimitSecretReferences: false,
 		// Auto mount service account API token secrets
@@ -163,7 +163,10 @@ func (s *Plugin) Admit(ctx context.Context, a admission.Attributes, o admission.
 	if shouldIgnore(a) {
 		return nil
 	}
-
+	if a.GetOperation() != admission.Create {
+		// we only mutate pods during create requests
+		return nil
+	}
 	pod := a.GetObject().(*api.Pod)
 
 	// Don't modify the spec of mirror pods.
@@ -180,7 +183,7 @@ func (s *Plugin) Admit(ctx context.Context, a admission.Attributes, o admission.
 
 	serviceAccount, err := s.getServiceAccount(a.GetNamespace(), pod.Spec.ServiceAccountName)
 	if err != nil {
-		return admission.NewForbidden(a, fmt.Errorf("error looking up service account %s/%s: %v", a.GetNamespace(), pod.Spec.ServiceAccountName, err))
+		return admission.NewForbidden(a, fmt.Errorf("error looking up service account %s/%s: %w", a.GetNamespace(), pod.Spec.ServiceAccountName, err))
 	}
 	if s.MountServiceAccountToken && shouldAutomount(serviceAccount, pod) {
 		if err := s.mountServiceAccountToken(serviceAccount, pod); err != nil {
@@ -208,6 +211,15 @@ func (s *Plugin) Validate(ctx context.Context, a admission.Attributes, o admissi
 
 	pod := a.GetObject().(*api.Pod)
 
+	if a.GetOperation() == admission.Update && a.GetSubresource() == "ephemeralcontainers" {
+		return s.limitEphemeralContainerSecretReferences(pod, a)
+	}
+
+	if a.GetOperation() != admission.Create {
+		// we only validate pod specs during create requests
+		return nil
+	}
+
 	// Mirror pods have restrictions on what they can reference
 	if _, isMirrorPod := pod.Annotations[api.MirrorPodAnnotationKey]; isMirrorPod {
 		if len(pod.Spec.ServiceAccountName) != 0 {
@@ -233,6 +245,10 @@ func (s *Plugin) Validate(ctx context.Context, a admission.Attributes, o admissi
 		return nil
 	}
 
+	// Require container pods to have service accounts
+	if len(pod.Spec.ServiceAccountName) == 0 {
+		return admission.NewForbidden(a, fmt.Errorf("no service account specified for pod %s/%s", a.GetNamespace(), pod.Name))
+	}
 	// Ensure the referenced service account exists
 	serviceAccount, err := s.getServiceAccount(a.GetNamespace(), pod.Spec.ServiceAccountName)
 	if err != nil {
@@ -249,10 +265,7 @@ func (s *Plugin) Validate(ctx context.Context, a admission.Attributes, o admissi
 }
 
 func shouldIgnore(a admission.Attributes) bool {
-	if a.GetResource().GroupResource() != api.Resource("pods") {
-		return true
-	}
-	if a.GetSubresource() != "" {
+	if a.GetResource().GroupResource() != api.Resource("pods") || (a.GetSubresource() != "" && a.GetSubresource() != "ephemeralcontainers") {
 		return true
 	}
 	obj := a.GetObject()
@@ -424,6 +437,36 @@ func (s *Plugin) limitSecretReferences(serviceAccount *corev1.ServiceAccount, po
 	return nil
 }
 
+func (s *Plugin) limitEphemeralContainerSecretReferences(pod *api.Pod, a admission.Attributes) error {
+	// Require ephemeral container pods to have service accounts
+	if len(pod.Spec.ServiceAccountName) == 0 {
+		return admission.NewForbidden(a, fmt.Errorf("no service account specified for pod %s/%s", a.GetNamespace(), pod.Name))
+	}
+	// Ensure the referenced service account exists
+	serviceAccount, err := s.getServiceAccount(a.GetNamespace(), pod.Spec.ServiceAccountName)
+	if err != nil {
+		return admission.NewForbidden(a, fmt.Errorf("error looking up service account %s/%s: %w", a.GetNamespace(), pod.Spec.ServiceAccountName, err))
+	}
+	if !s.enforceMountableSecrets(serviceAccount) {
+		return nil
+	}
+	// Ensure all secrets the ephemeral containers reference are allowed by the service account
+	mountableSecrets := sets.NewString()
+	for _, s := range serviceAccount.Secrets {
+		mountableSecrets.Insert(s.Name)
+	}
+	for _, container := range pod.Spec.EphemeralContainers {
+		for _, env := range container.Env {
+			if env.ValueFrom != nil && env.ValueFrom.SecretKeyRef != nil {
+				if !mountableSecrets.Has(env.ValueFrom.SecretKeyRef.Name) {
+					return fmt.Errorf("ephemeral container %s with envVar %s referencing secret.secretName=\"%s\" is not allowed because service account %s does not reference that secret", container.Name, env.Name, env.ValueFrom.SecretKeyRef.Name, serviceAccount.Name)
+				}
+			}
+		}
+	}
+	return nil
+}
+
 func (s *Plugin) mountServiceAccountToken(serviceAccount *corev1.ServiceAccount, pod *api.Pod) error {
 	var (
 		// serviceAccountToken holds the name of a secret containing a legacy service account token
diff --git a/plugin/pkg/admission/serviceaccount/admission_test.go b/plugin/pkg/admission/serviceaccount/admission_test.go
index 77ef50c6..6489b391 100644
--- a/plugin/pkg/admission/serviceaccount/admission_test.go
+++ b/plugin/pkg/admission/serviceaccount/admission_test.go
@@ -630,6 +630,34 @@ func TestAllowsReferencedSecret(t *testing.T) {
 	if err := admissiontesting.WithReinvocationTesting(t, admit).Admit(context.TODO(), attrs, nil); err != nil {
 		t.Errorf("Unexpected error: %v", err)
 	}
+
+	pod2 = &api.Pod{
+		Spec: api.PodSpec{
+			ServiceAccountName: DefaultServiceAccountName,
+			EphemeralContainers: []api.EphemeralContainer{
+				{
+					EphemeralContainerCommon: api.EphemeralContainerCommon{
+						Name: "container-2",
+						Env: []api.EnvVar{
+							{
+								Name: "env-1",
+								ValueFrom: &api.EnvVarSource{
+									SecretKeyRef: &api.SecretKeySelector{
+										LocalObjectReference: api.LocalObjectReference{Name: "foo"},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+	// validate enforces restrictions on secret mounts when operation==create and subresource=='' or operation==update and subresource==ephemeralcontainers"
+	attrs = admission.NewAttributesRecord(pod2, nil, api.Kind("Pod").WithVersion("version"), ns, "myname", api.Resource("pods").WithVersion("version"), "ephemeralcontainers", admission.Update, &metav1.UpdateOptions{}, false, nil)
+	if err := admit.Validate(context.TODO(), attrs, nil); err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
 }
 
 func TestRejectsUnreferencedSecretVolumes(t *testing.T) {
@@ -708,6 +736,66 @@ func TestRejectsUnreferencedSecretVolumes(t *testing.T) {
 	if err := admissiontesting.WithReinvocationTesting(t, admit).Admit(context.TODO(), attrs, nil); err == nil || !strings.Contains(err.Error(), "with envVar") {
 		t.Errorf("Unexpected error: %v", err)
 	}
+
+	pod2 = &api.Pod{
+		Spec: api.PodSpec{
+			ServiceAccountName: DefaultServiceAccountName,
+			InitContainers: []api.Container{
+				{
+					Name: "container-1",
+					Env: []api.EnvVar{
+						{
+							Name: "env-1",
+							ValueFrom: &api.EnvVarSource{
+								SecretKeyRef: &api.SecretKeySelector{
+									LocalObjectReference: api.LocalObjectReference{Name: "foo"},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+	attrs = admission.NewAttributesRecord(pod2, nil, api.Kind("Pod").WithVersion("version"), ns, "myname", api.Resource("pods").WithVersion("version"), "", admission.Update, &metav1.UpdateOptions{}, false, nil)
+	if err := admissiontesting.WithReinvocationTesting(t, admit).Admit(context.TODO(), attrs, nil); err != nil {
+		t.Errorf("admit only enforces restrictions on secret mounts when operation==create. Unexpected error: %v", err)
+	}
+	attrs = admission.NewAttributesRecord(pod2, nil, api.Kind("Pod").WithVersion("version"), ns, "myname", api.Resource("pods").WithVersion("version"), "", admission.Create, &metav1.CreateOptions{}, false, nil)
+	if err := admit.Validate(context.TODO(), attrs, nil); err == nil || !strings.Contains(err.Error(), "with envVar") {
+		t.Errorf("validate only enforces restrictions on secret mounts when operation==create and subresource==''. Unexpected error: %v", err)
+	}
+
+	pod2 = &api.Pod{
+		Spec: api.PodSpec{
+			ServiceAccountName: DefaultServiceAccountName,
+			EphemeralContainers: []api.EphemeralContainer{
+				{
+					EphemeralContainerCommon: api.EphemeralContainerCommon{
+						Name: "container-2",
+						Env: []api.EnvVar{
+							{
+								Name: "env-1",
+								ValueFrom: &api.EnvVarSource{
+									SecretKeyRef: &api.SecretKeySelector{
+										LocalObjectReference: api.LocalObjectReference{Name: "foo"},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+	attrs = admission.NewAttributesRecord(pod2, nil, api.Kind("Pod").WithVersion("version"), ns, "myname", api.Resource("pods").WithVersion("version"), "", admission.Update, &metav1.UpdateOptions{}, false, nil)
+	if err := admissiontesting.WithReinvocationTesting(t, admit).Admit(context.TODO(), attrs, nil); err != nil {
+		t.Errorf("admit only enforces restrictions on secret mounts when operation==create and subresource==''. Unexpected error: %v", err)
+	}
+	attrs = admission.NewAttributesRecord(pod2, nil, api.Kind("Pod").WithVersion("version"), ns, "myname", api.Resource("pods").WithVersion("version"), "ephemeralcontainers", admission.Update, &metav1.UpdateOptions{}, false, nil)
+	if err := admit.Validate(context.TODO(), attrs, nil); err == nil || !strings.Contains(err.Error(), "with envVar") {
+		t.Errorf("validate enforces restrictions on secret mounts when operation==update and subresource==ephemeralcontainers. Unexpected error: %v", err)
+	}
 }
 
 func TestAllowUnreferencedSecretVolumesForPermissiveSAs(t *testing.T) {
-- 
2.25.1

