kuberuntime: check the value of RunAsNonRoot when verifying

The verification function is fixed to check the value of RunAsNonRoot,
not just the existence of it. Also adds unit tests to verify the correct
behavior.

pkg/kubelet/kuberuntime/kuberuntime_container_test.go

@@ -228,7 +228,7 @@ func TestGenerateContainerConfig(t *testing.T) {
 	assert.Equal(t, expectedConfig, containerConfig, "generate container config for kubelet runtime v1.")
 
 	runAsUser := types.UnixUserID(0)
-	RunAsNonRoot := false
+	runAsNonRootTrue := true
 	podWithContainerSecurityContext := &v1.Pod{
 		ObjectMeta: metav1.ObjectMeta{
 			UID:       "12345678",
@@ -244,7 +244,7 @@ func TestGenerateContainerConfig(t *testing.T) {
 					Command:         []string{"testCommand"},
 					WorkingDir:      "testWorkingDir",
 					SecurityContext: &v1.SecurityContext{
-						RunAsNonRoot: &RunAsNonRoot,
+						RunAsNonRoot: &runAsNonRootTrue,
 						RunAsUser:    &runAsUser,
 					},
 				},

pkg/kubelet/kuberuntime/security_context.go

@@ -72,7 +72,8 @@ func (m *kubeGenericRuntimeManager) determineEffectiveSecurityContext(pod *v1.Po
 // verifyRunAsNonRoot verifies RunAsNonRoot.
 func verifyRunAsNonRoot(pod *v1.Pod, container *v1.Container, uid int64) error {
 	effectiveSc := securitycontext.DetermineEffectiveSecurityContext(pod, container)
-	if effectiveSc == nil || effectiveSc.RunAsNonRoot == nil {
+	// If the option is not set, or if running as root is allowed, return nil.
+	if effectiveSc == nil || effectiveSc.RunAsNonRoot == nil || !*effectiveSc.RunAsNonRoot {
 		return nil
 	}
 

pkg/kubelet/kuberuntime/security_context_test.go

@@ -45,60 +45,57 @@ func TestVerifyRunAsNonRoot(t *testing.T) {
 		},
 	}
 
+	rootUser := types.UnixUserID(0)
+	runAsNonRootTrue := true
+	runAsNonRootFalse := false
+
+	for _, test := range []struct {
+		desc   string
+		sc     *v1.SecurityContext
+		errStr string
+	}{
+		{
+			desc:   "Pass if SecurityContext is not set",
+			sc:     nil,
+			errStr: "",
+		},
+		{
+			desc: "Pass if RunAsNonRoot is not set",
+			sc: &v1.SecurityContext{
+				RunAsUser: &rootUser,
+			},
+			errStr: "",
+		},
+		{
+			desc: "Pass if RunAsNonRoot is false",
+			sc: &v1.SecurityContext{
+				RunAsNonRoot: &runAsNonRootFalse,
+				RunAsUser:    &rootUser,
+			},
+			errStr: "",
+		},
+		{
+			desc: "Fail if container's RunAsUser is root and RunAsNonRoot is true",
+			sc: &v1.SecurityContext{
+				RunAsNonRoot: &runAsNonRootTrue,
+				RunAsUser:    &rootUser,
+			},
+			errStr: "container's runAsUser breaks non-root policy",
+		},
+		{
+			desc: "Fail if image's user is root and RunAsNonRoot is true",
+			sc: &v1.SecurityContext{
+				RunAsNonRoot: &runAsNonRootTrue,
+			},
+			errStr: "container has runAsNonRoot and image will run as root",
+		},
+	} {
+		pod.Spec.Containers[0].SecurityContext = test.sc
 		err := verifyRunAsNonRoot(pod, &pod.Spec.Containers[0], int64(0))
-	assert.NoError(t, err)
+		if len(test.errStr) == 0 {
-
+			assert.NoError(t, err, test.desc)
-	runAsUser := types.UnixUserID(0)
+		} else {
-	RunAsNonRoot := false
+			assert.EqualError(t, err, test.errStr, test.desc)
-	podWithContainerSecurityContext := &v1.Pod{
-		ObjectMeta: metav1.ObjectMeta{
-			UID:       "12345678",
-			Name:      "bar",
-			Namespace: "new",
-		},
-		Spec: v1.PodSpec{
-			Containers: []v1.Container{
-				{
-					Name:            "foo",
-					Image:           "busybox",
-					ImagePullPolicy: v1.PullIfNotPresent,
-					Command:         []string{"testCommand"},
-					WorkingDir:      "testWorkingDir",
-					SecurityContext: &v1.SecurityContext{
-						RunAsNonRoot: &RunAsNonRoot,
-						RunAsUser:    &runAsUser,
-					},
-				},
-			},
-		},
 		}
-
-	err2 := verifyRunAsNonRoot(podWithContainerSecurityContext, &podWithContainerSecurityContext.Spec.Containers[0], int64(0))
-	assert.EqualError(t, err2, "container's runAsUser breaks non-root policy")
-
-	RunAsNonRoot = false
-	podWithContainerSecurityContext = &v1.Pod{
-		ObjectMeta: metav1.ObjectMeta{
-			UID:       "12345678",
-			Name:      "bar",
-			Namespace: "new",
-		},
-		Spec: v1.PodSpec{
-			Containers: []v1.Container{
-				{
-					Name:            "foo",
-					Image:           "busybox",
-					ImagePullPolicy: v1.PullIfNotPresent,
-					Command:         []string{"testCommand"},
-					WorkingDir:      "testWorkingDir",
-					SecurityContext: &v1.SecurityContext{
-						RunAsNonRoot: &RunAsNonRoot,
-					},
-				},
-			},
-		},
 	}
-
-	err3 := verifyRunAsNonRoot(podWithContainerSecurityContext, &podWithContainerSecurityContext.Spec.Containers[0], int64(0))
-	assert.EqualError(t, err3, "container has runAsNonRoot and image will run as root")
 }