PodSecurity: check: runAsNonRoot

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

@@ -0,0 +1,105 @@
+/*
+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 (
+	"strings"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/pod-security-admission/api"
+)
+
+/*
+Containers must be required to run as non-root users.
+
+**Restricted Fields:**
+
+spec.securityContext.runAsNonRoot
+spec.containers[*].securityContext.runAsNonRoot
+spec.initContainers[*].securityContext.runAsNonRoot
+
+**Allowed Values:** true
+*/
+
+func init() {
+	addCheck(CheckRunAsNonRoot)
+}
+
+// CheckRunAsNonRoot returns a restricted level check
+// that requires runAsNonRoot=true in 1.0+
+func CheckRunAsNonRoot() Check {
+	return Check{
+		ID:    "runAsNonRoot",
+		Level: api.LevelRestricted,
+		Versions: []VersionedCheck{
+			{
+				MinimumVersion: api.MajorMinorVersion(1, 0),
+				CheckPod:       runAsNonRoot_1_0,
+			},
+		},
+	}
+}
+
+func runAsNonRoot_1_0(podMetadata *metav1.ObjectMeta, podSpec *corev1.PodSpec) CheckResult {
+	var forbiddenPaths []string
+
+	// TODO: how to check ephemeral containers
+
+	containerCount := 0
+	containerRunAsNonRootCount := 0
+	podRunAsNonRoot := false
+
+	visitContainersWithPath(podSpec, field.NewPath("spec"), func(container *corev1.Container, path *field.Path) {
+		containerCount++
+		if container.SecurityContext != nil && container.SecurityContext.RunAsNonRoot != nil {
+			if !*container.SecurityContext.RunAsNonRoot {
+				forbiddenPaths = append(forbiddenPaths, path.Child("securityContext", "runAsNonRoot").String())
+			} else {
+				containerRunAsNonRootCount++
+			}
+		}
+	})
+
+	if podSpec.SecurityContext != nil && podSpec.SecurityContext.RunAsNonRoot != nil {
+		if !*podSpec.SecurityContext.RunAsNonRoot {
+			forbiddenPaths = append(forbiddenPaths, field.NewPath("spec").Child("securityContext", "runAsNonRoot").String())
+		} else {
+			podRunAsNonRoot = true
+		}
+	}
+
+	// pod or containers explicitly set runAsNonRoot=false
+	if len(forbiddenPaths) > 0 {
+		return CheckResult{
+			Allowed:         false,
+			ForbiddenReason: "runAsNonRoot != false",
+			ForbiddenDetail: strings.Join(forbiddenPaths, ", "),
+		}
+	}
+
+	// pod didn't set runAsNonRoot and not all containers opted into runAsNonRoot
+	if podRunAsNonRoot == false && containerCount > containerRunAsNonRootCount {
+		return CheckResult{
+			Allowed:         false,
+			ForbiddenReason: "runAsNonRoot != false",
+		}
+	}
+
+	return CheckResult{Allowed: true}
+}

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

@@ -0,0 +1,91 @@
+/*
+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 test
+
+import (
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/pod-security-admission/api"
+	"k8s.io/utils/pointer"
+)
+
+/*
+TODO: include field paths in reflect-based unit test
+
+podFields: []string{
+	`securityContext.runAsNonRoot`,
+},
+containerFields: []string{
+	`securityContext.runAsNonRoot`,
+},
+
+*/
+
+func init() {
+
+	fixtureData_1_0 := fixtureGenerator{
+		generatePass: func(p *corev1.Pod) []*corev1.Pod {
+			p = ensureSecurityContext(p)
+			return []*corev1.Pod{
+				// set at pod level
+				tweak(p, func(p *corev1.Pod) {
+					p.Spec.SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+					p.Spec.Containers[0].SecurityContext.RunAsNonRoot = nil
+					p.Spec.InitContainers[0].SecurityContext.RunAsNonRoot = nil
+				}),
+				// set on all containers
+				tweak(p, func(p *corev1.Pod) {
+					p.Spec.SecurityContext.RunAsNonRoot = nil
+					p.Spec.Containers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+					p.Spec.InitContainers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+				}),
+				// set at pod level and containers
+				tweak(p, func(p *corev1.Pod) {
+					p.Spec.SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+					p.Spec.Containers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+					p.Spec.InitContainers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(true)
+				}),
+			}
+		},
+		generateFail: func(p *corev1.Pod) []*corev1.Pod {
+			p = ensureSecurityContext(p)
+			return []*corev1.Pod{
+				// unset everywhere
+				tweak(p, func(p *corev1.Pod) {
+					p.Spec.SecurityContext.RunAsNonRoot = nil
+					p.Spec.Containers[0].SecurityContext.RunAsNonRoot = nil
+					p.Spec.InitContainers[0].SecurityContext.RunAsNonRoot = nil
+				}),
+				// explicit false on pod
+				tweak(p, func(p *corev1.Pod) { p.Spec.SecurityContext.RunAsNonRoot = pointer.BoolPtr(false) }),
+				// explicit false on containers
+				tweak(p, func(p *corev1.Pod) { p.Spec.Containers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(false) }),
+				tweak(p, func(p *corev1.Pod) { p.Spec.InitContainers[0].SecurityContext.RunAsNonRoot = pointer.BoolPtr(false) }),
+				// nil security contexts
+				tweak(p, func(p *corev1.Pod) {
+					p.Spec.SecurityContext = nil
+					p.Spec.Containers[0].SecurityContext = nil
+					p.Spec.InitContainers[0].SecurityContext = nil
+				}),
+			}
+		},
+	}
+
+	registerFixtureGenerator(
+		fixtureKey{level: api.LevelRestricted, version: api.MajorMinorVersion(1, 0), check: "runAsNonRoot"},
+		fixtureData_1_0,
+	)
+}