PodSecurity: baseline hostProcess check

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

@@ -0,0 +1,87 @@
+/*
+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 not run as hostProcess.
+
+**Restricted Fields:**
+
+spec.securityContext.windowsOptions.hostProcess
+spec.containers[*].securityContext.windowsOptions.hostProcess
+
+**Allowed Values:** undefined / false
+*/
+
+func init() {
+	addCheck(CheckHostProcess)
+}
+
+// CheckHostProcess returns a baseline level check
+// that forbids hostProcess=true in 1.0+
+func CheckHostProcess() Check {
+	return Check{
+		ID:    "hostProcess",
+		Level: api.LevelBaseline,
+		Versions: []VersionedCheck{
+			{
+				MinimumVersion: api.MajorMinorVersion(1, 0),
+				CheckPod:       hostProcess_1_0,
+			},
+		},
+	}
+}
+
+func hostProcess_1_0(podMetadata *metav1.ObjectMeta, podSpec *corev1.PodSpec) CheckResult {
+	var forbiddenContainers []string
+	visitContainersWithPath(podSpec, field.NewPath("spec"), func(container *corev1.Container, path *field.Path) {
+		if container.SecurityContext != nil &&
+			container.SecurityContext.WindowsOptions != nil &&
+			container.SecurityContext.WindowsOptions.HostProcess != nil &&
+			*container.SecurityContext.WindowsOptions.HostProcess {
+			forbiddenContainers = append(forbiddenContainers, container.Name)
+		}
+	})
+
+	podSpecForbidden := false
+	if podSpec.SecurityContext != nil &&
+		podSpec.SecurityContext.WindowsOptions != nil &&
+		podSpec.SecurityContext.WindowsOptions.HostProcess != nil &&
+		*podSpec.SecurityContext.WindowsOptions.HostProcess {
+		podSpecForbidden = true
+	}
+
+	// pod or containers explicitly set hostProcess=true
+	if len(forbiddenContainers) > 0 || podSpecForbidden {
+		return CheckResult{
+			Allowed:         false,
+			ForbiddenReason: "hostProcess == true",
+			ForbiddenDetail: strings.Join(forbiddenContainers, ", "),
+		}
+	}
+
+	return CheckResult{Allowed: true}
+}

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

@@ -0,0 +1,81 @@
+/*
+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/component-base/featuregate"
+	"k8s.io/pod-security-admission/api"
+	"k8s.io/utils/pointer"
+)
+
+/*
+TODO: include field paths in reflect-based unit test
+
+podFields: []string{
+	`securityContext.windowsOptions.hostProcess`,
+},
+containerFields: []string{
+	`securityContext.windowsOptions.hostProcess`,
+},
+
+*/
+
+func init() {
+
+	fixtureData_1_0 := fixtureGenerator{
+		generatePass: func(p *corev1.Pod) []*corev1.Pod {
+			return []*corev1.Pod{p}
+		},
+		failRequiresFeatures: []featuregate.Feature{"WindowsHostProcessContainers"},
+		generateFail: func(p *corev1.Pod) []*corev1.Pod {
+			p = ensureSecurityContext(p)
+			if p.Spec.SecurityContext.WindowsOptions == nil {
+				p.Spec.SecurityContext.WindowsOptions = &corev1.WindowsSecurityContextOptions{}
+			}
+			if p.Spec.Containers[0].SecurityContext.WindowsOptions == nil {
+				p.Spec.Containers[0].SecurityContext.WindowsOptions = &corev1.WindowsSecurityContextOptions{}
+			}
+			if p.Spec.InitContainers[0].SecurityContext.WindowsOptions == nil {
+				p.Spec.InitContainers[0].SecurityContext.WindowsOptions = &corev1.WindowsSecurityContextOptions{}
+			}
+			return []*corev1.Pod{
+				// true for pod
+				tweak(p, func(p *corev1.Pod) {
+					// HostNetwork is required to be true for HostProcess pods.
+					// Set to true here so we pass API validation and get to admission checks.
+					p.Spec.HostNetwork = true
+					p.Spec.SecurityContext.WindowsOptions.HostProcess = pointer.BoolPtr(true)
+				}),
+				// true for containers
+				tweak(p, func(p *corev1.Pod) {
+					// HostNetwork is required to be true for HostProcess pods.
+					// Set to true here so we pass API validation and get to admission checks.
+					p.Spec.HostNetwork = true
+					p.Spec.Containers[0].SecurityContext.WindowsOptions.HostProcess = pointer.BoolPtr(true)
+					p.Spec.InitContainers[0].SecurityContext.WindowsOptions.HostProcess = pointer.BoolPtr(true)
+				}),
+			}
+		},
+	}
+
+	registerFixtureGenerator(
+		fixtureKey{level: api.LevelBaseline, version: api.MajorMinorVersion(1, 0), check: "hostProcess"},
+		fixtureData_1_0,
+	)
+	// TODO: register another set of fixtures with passing test cases that explicitly set hostProcess=false at pod and container level once hostProcess is GA
+}

test/integration/auth/podsecurity_test.go

@@ -32,6 +32,7 @@ import (
 func TestPodSecurity(t *testing.T) {
 	// Enable all feature gates needed to allow all fields to be exercised
 	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.ProcMountType, true)()
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.WindowsHostProcessContainers, true)()
 	// Ensure the PodSecurity feature is enabled
 	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodSecurity, true)()
 	// Start server