PodSecurity: allowPrivilegeEscalation: cleanup

Make forbidden details more compact
Add unit test exercising forbidden message/details
Consolidate fixtures

staging/src/k8s.io/pod-security-admission/policy/check_allowPrivilegeEscalation.go

@@ -17,7 +17,7 @@ limitations under the License.
 package policy
 
 import (
-	"strings"
+	"fmt"
 
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -58,18 +58,22 @@ func CheckAllowPrivilegeEscalation() Check {
 }
 
 func allowPrivilegeEscalation_1_8(podMetadata *metav1.ObjectMeta, podSpec *corev1.PodSpec) CheckResult {
-	var forbiddenPaths []string
+	var badContainers []string
 	visitContainersWithPath(podSpec, field.NewPath("spec"), func(container *corev1.Container, path *field.Path) {
 		if container.SecurityContext == nil || container.SecurityContext.AllowPrivilegeEscalation == nil || *container.SecurityContext.AllowPrivilegeEscalation {
-			forbiddenPaths = append(forbiddenPaths, path.Child("securityContext", "allowPrivilegeEscalation").String())
+			badContainers = append(badContainers, container.Name)
 		}
 	})
 
-	if len(forbiddenPaths) > 0 {
+	if len(badContainers) > 0 {
 		return CheckResult{
 			Allowed:         false,
 			ForbiddenReason: "allowPrivilegeEscalation != false",
-			ForbiddenDetail: strings.Join(forbiddenPaths, ", "),
+			ForbiddenDetail: fmt.Sprintf(
+				"%s %s must set securityContext.allowPrivilegeEscalation=false",
+				pluralize("container", "containers", len(badContainers)),
+				joinQuote(badContainers),
+			),
 		}
 	}
 	return CheckResult{Allowed: true}

staging/src/k8s.io/pod-security-admission/policy/check_allowPrivilegeEscalation_test.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2021 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 policy
+
+import (
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+	utilpointer "k8s.io/utils/pointer"
+)
+
+func TestAllowPrivilegeEscalation(t *testing.T) {
+	tests := []struct {
+		name         string
+		pod          *corev1.Pod
+		expectReason string
+		expectDetail string
+	}{
+		{
+			name: "multiple containers",
+			pod: &corev1.Pod{Spec: corev1.PodSpec{
+				Containers: []corev1.Container{
+					{Name: "a"},
+					{Name: "b", SecurityContext: &corev1.SecurityContext{AllowPrivilegeEscalation: nil}},
+					{Name: "c", SecurityContext: &corev1.SecurityContext{AllowPrivilegeEscalation: utilpointer.Bool(true)}},
+					{Name: "d", SecurityContext: &corev1.SecurityContext{AllowPrivilegeEscalation: utilpointer.Bool(false)}},
+				}}},
+			expectReason: `allowPrivilegeEscalation != false`,
+			expectDetail: `containers "a", "b", "c" must set securityContext.allowPrivilegeEscalation=false`,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			result := allowPrivilegeEscalation_1_8(&tc.pod.ObjectMeta, &tc.pod.Spec)
+			if result.Allowed {
+				t.Fatal("expected disallowed")
+			}
+			if e, a := tc.expectReason, result.ForbiddenReason; e != a {
+				t.Errorf("expected\n%s\ngot\n%s", e, a)
+			}
+			if e, a := tc.expectDetail, result.ForbiddenDetail; e != a {
+				t.Errorf("expected\n%s\ngot\n%s", e, a)
+			}
+		})
+	}
+}

staging/src/k8s.io/pod-security-admission/test/fixtures_allowPrivilegeEscalation.go

@@ -43,15 +43,14 @@ func init() {
 				tweak(p, func(p *corev1.Pod) {
 					p.Spec.Containers[0].SecurityContext.AllowPrivilegeEscalation = pointer.BoolPtr(true)
 				}),
+				// ensure initContainers are checked
 				tweak(p, func(p *corev1.Pod) {
 					p.Spec.InitContainers[0].SecurityContext.AllowPrivilegeEscalation = pointer.BoolPtr(true)
 				}),
 				// nil AllowPrivilegeEscalation
 				tweak(p, func(p *corev1.Pod) { p.Spec.Containers[0].SecurityContext.AllowPrivilegeEscalation = nil }),
-				tweak(p, func(p *corev1.Pod) { p.Spec.InitContainers[0].SecurityContext.AllowPrivilegeEscalation = nil }),
 				// nil security context
 				tweak(p, func(p *corev1.Pod) { p.Spec.Containers[0].SecurityContext = nil }),
-				tweak(p, func(p *corev1.Pod) { p.Spec.InitContainers[0].SecurityContext = nil }),
 			}
 		},
 	}