Implement set-security-context feature for affinity assistant containers

Ensures that when using Affinity Assistant, one can adhere to restricted pod security standards. Enables users to apply a container level securityContext for Affinity Assistants.
tektoncd · Sep 18, 2024 · 0649270 · 0649270
1 parent 09e4b6d
commit 0649270
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Showing 10 changed files with 185 additions and 44 deletions.
diff --git a/docs/additional-configs.md b/docs/additional-configs.md
@@ -461,7 +461,8 @@ Out-of-the-box, Tekton Pipelines Controller is configured for relatively small-s
 
 To allow TaskRuns and PipelineRuns to run in namespaces with [restricted pod security standards](https://kubernetes.io/docs/concepts/security/pod-security-standards/),
 set the "set-security-context" feature flag to "true" in the [feature-flags configMap](#customizing-the-pipelines-controller-behavior). This configuration option applies a [SecurityContext](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/)
-to any containers injected into TaskRuns by the Pipelines controller. This SecurityContext may not be supported in all Kubernetes implementations (for example, OpenShift).
+to any containers injected into TaskRuns by the Pipelines controller. If the [Affinity Assistants](affinityassistants.md) feature is enabled, the SecurityContext is also applied to those containers.
+This SecurityContext may not be supported in all Kubernetes implementations (for example, OpenShift).
 
 **Note**: running TaskRuns and PipelineRuns in the "tekton-pipelines" namespace is discouraged.
 

diff --git a/pkg/internal/affinityassistant/affinityassistant_types.go b/pkg/internal/affinityassistant/affinityassistant_types.go
@@ -54,3 +54,9 @@ func GetAffinityAssistantBehavior(ctx context.Context) (AffinityAssistantBehavio
 
 	return "", fmt.Errorf("unknown combination of disable-affinity-assistant: %v and coschedule: %v", disableAA, coschedule)
 }
+
+// ContainerConfig defines AffinityAssistant container configuration
+type ContainerConfig struct {
+	Image              string
+	SetSecurityContext bool
+}
diff --git a/pkg/pod/pod.go b/pkg/pod/pod.go
@@ -60,8 +60,8 @@ const (
 	// SpiffeCsiDriver is the CSI storage plugin needed for injection of SPIFFE workload api.
 	SpiffeCsiDriver = "csi.spiffe.io"
 
-	// osSelectorLabel is the label Kubernetes uses for OS-specific workloads (https://kubernetes.io/docs/reference/labels-annotations-taints/#kubernetes-io-os)
-	osSelectorLabel = "kubernetes.io/os"
+	// OsSelectorLabel is the label Kubernetes uses for OS-specific workloads (https://kubernetes.io/docs/reference/labels-annotations-taints/#kubernetes-io-os)
+	OsSelectorLabel = "kubernetes.io/os"
 
 	// TerminationReasonTimeoutExceeded indicates a step execution timed out.
 	TerminationReasonTimeoutExceeded = "TimeoutExceeded"
@@ -132,10 +132,10 @@ var (
 	allowPrivilegeEscalation = false
 	runAsNonRoot             = true
 
-	// The following security contexts allow init containers to run in namespaces
+	// LinuxSecurityContext allow init containers to run in namespaces
 	// with "restricted" pod security admission
 	// See https://kubernetes.io/docs/concepts/security/pod-security-standards/#restricted
-	linuxSecurityContext = &corev1.SecurityContext{
+	LinuxSecurityContext = &corev1.SecurityContext{
 		AllowPrivilegeEscalation: &allowPrivilegeEscalation,
 		Capabilities: &corev1.Capabilities{
 			Drop: []corev1.Capability{"ALL"},
@@ -145,7 +145,7 @@ var (
 			Type: corev1.SeccompProfileTypeRuntimeDefault,
 		},
 	}
-	windowsSecurityContext = &corev1.SecurityContext{
+	WindowsSecurityContext = &corev1.SecurityContext{
 		RunAsNonRoot: &runAsNonRoot,
 	}
 )
@@ -607,9 +607,9 @@ func entrypointInitContainer(image string, steps []v1.Step, setSecurityContext,
 		command = append(command, StepName(s.Name, i))
 	}
 	volumeMounts := []corev1.VolumeMount{binMount, internalStepsMount}
-	securityContext := linuxSecurityContext
+	securityContext := LinuxSecurityContext
 	if windows {
-		securityContext = windowsSecurityContext
+		securityContext = WindowsSecurityContext
 	}
 
 	// Rewrite steps with entrypoint binary. Append the entrypoint init
@@ -679,9 +679,9 @@ func createResultsSidecar(taskSpec v1.TaskSpec, image string, setSecurityContext
 		Image:   image,
 		Command: command,
 	}
-	securityContext := linuxSecurityContext
+	securityContext := LinuxSecurityContext
 	if windows {
-		securityContext = windowsSecurityContext
+		securityContext = WindowsSecurityContext
 	}
 	if setSecurityContext {
 		sidecar.SecurityContext = securityContext
@@ -696,7 +696,7 @@ func usesWindows(tr *v1.TaskRun) bool {
 	if tr.Spec.PodTemplate == nil || tr.Spec.PodTemplate.NodeSelector == nil {
 		return false
 	}
-	osSelector := tr.Spec.PodTemplate.NodeSelector[osSelectorLabel]
+	osSelector := tr.Spec.PodTemplate.NodeSelector[OsSelectorLabel]
 	return osSelector == "windows"
 }
 

diff --git a/pkg/pod/pod_test.go b/pkg/pod/pod_test.go
@@ -2162,7 +2162,7 @@ _EOF_
 						{Name: "tekton-internal-bin", ReadOnly: true, MountPath: "/tekton/bin"},
 						{Name: "tekton-internal-run-0", ReadOnly: true, MountPath: "/tekton/run/0"},
 					}, implicitVolumeMounts...),
-					SecurityContext: linuxSecurityContext,
+					SecurityContext: LinuxSecurityContext,
 				}},
 				Volumes: append(implicitVolumes, binVolume, runVolume(0), downwardVolume, corev1.Volume{
 					Name:         "tekton-creds-init-home-0",
@@ -2403,7 +2403,7 @@ _EOF_
 						{Name: "tekton-internal-bin", ReadOnly: true, MountPath: "/tekton/bin"},
 						{Name: "tekton-internal-run-0", ReadOnly: true, MountPath: "/tekton/run/0"},
 					}, implicitVolumeMounts...),
-					SecurityContext: linuxSecurityContext,
+					SecurityContext: LinuxSecurityContext,
 				}},
 				Volumes: append(implicitVolumes, binVolume, runVolume(0), downwardVolume, corev1.Volume{
 					Name:         "tekton-creds-init-home-0",
@@ -3424,7 +3424,7 @@ func TestPrepareInitContainers(t *testing.T) {
 			WorkingDir:      "/",
 			Command:         []string{"/ko-app/entrypoint", "init", "/ko-app/entrypoint", entrypointBinary, "step-foo", "step-bar"},
 			VolumeMounts:    []corev1.VolumeMount{binMount, internalStepsMount},
-			SecurityContext: linuxSecurityContext,
+			SecurityContext: LinuxSecurityContext,
 		},
 	}, {
 		name: "nothing-special-two-steps-windows",
@@ -3456,7 +3456,7 @@ func TestPrepareInitContainers(t *testing.T) {
 			WorkingDir:      "/",
 			Command:         []string{"/ko-app/entrypoint", "init", "/ko-app/entrypoint", entrypointBinary, "step-foo", "step-bar"},
 			VolumeMounts:    []corev1.VolumeMount{binMount, internalStepsMount},
-			SecurityContext: windowsSecurityContext,
+			SecurityContext: WindowsSecurityContext,
 		},
 	}}
 	for _, tc := range tcs {
@@ -3485,13 +3485,13 @@ func TestUsesWindows(t *testing.T) {
 	}, {
 		name: "uses linux",
 		taskRun: &v1.TaskRun{Spec: v1.TaskRunSpec{PodTemplate: &pod.Template{NodeSelector: map[string]string{
-			osSelectorLabel: "linux",
+			OsSelectorLabel: "linux",
 		}}}},
 		want: false,
 	}, {
 		name: "uses windows",
 		taskRun: &v1.TaskRun{Spec: v1.TaskRunSpec{PodTemplate: &pod.Template{NodeSelector: map[string]string{
-			osSelectorLabel: "windows",
+			OsSelectorLabel: "windows",
 		}}}},
 		want: true,
 	}}

diff --git a/pkg/pod/script.go b/pkg/pod/script.go
@@ -87,13 +87,13 @@ func convertScripts(shellImageLinux string, shellImageWin string, steps []v1.Ste
 	shellImage := shellImageLinux
 	shellCommand := "sh"
 	shellArg := "-c"
-	securityContext := linuxSecurityContext
+	securityContext := LinuxSecurityContext
 	// Set windows variants for Image, Command and Args
 	if requiresWindows {
 		shellImage = shellImageWin
 		shellCommand = "pwsh"
 		shellArg = "-Command"
-		securityContext = windowsSecurityContext
+		securityContext = WindowsSecurityContext
 	}
 
 	placeScriptsInit := corev1.Container{

diff --git a/pkg/pod/script_test.go b/pkg/pod/script_test.go
@@ -159,7 +159,7 @@ _EOF_
 /tekton/bin/entrypoint decode-script "${scriptfile}"
 `},
 		VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount},
-		SecurityContext: linuxSecurityContext,
+		SecurityContext: LinuxSecurityContext,
 	}
 	want := []corev1.Container{{
 		Image:        "step-1",
@@ -465,7 +465,7 @@ fi
 debug-fail-continue-heredoc-randomly-generated-6nl7g
 `},
 				VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount, debugScriptsVolumeMount},
-				SecurityContext: linuxSecurityContext,
+				SecurityContext: LinuxSecurityContext,
 			},
 			wantSteps: []corev1.Container{{
 				Image:   "step-1",
@@ -608,7 +608,7 @@ fi
 debug-beforestep-fail-continue-heredoc-randomly-generated-6nl7g
 `},
 				VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount, debugScriptsVolumeMount},
-				SecurityContext: linuxSecurityContext},
+				SecurityContext: LinuxSecurityContext},
 			wantSteps: []corev1.Container{{
 				Name:    "step-1",
 				Image:   "step-1",
@@ -690,7 +690,7 @@ _EOF_
 /tekton/bin/entrypoint decode-script "${scriptfile}"
 `},
 		VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount},
-		SecurityContext: linuxSecurityContext,
+		SecurityContext: LinuxSecurityContext,
 	}
 	want := []corev1.Container{{
 		Image:        "step-1",
@@ -777,7 +777,7 @@ no-shebang
 "@ | Out-File -FilePath /tekton/scripts/script-3-mssqb.cmd
 `},
 		VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount},
-		SecurityContext: windowsSecurityContext,
+		SecurityContext: WindowsSecurityContext,
 	}
 	want := []corev1.Container{{
 		Image:        "step-1",
@@ -860,7 +860,7 @@ sidecar-1
 "@ | Out-File -FilePath /tekton/scripts/sidecar-script-0-mssqb
 `},
 		VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount},
-		SecurityContext: windowsSecurityContext,
+		SecurityContext: WindowsSecurityContext,
 	}
 	want := []corev1.Container{{
 		Image:        "step-1",
@@ -922,7 +922,7 @@ sidecar-1
 "@ | Out-File -FilePath /tekton/scripts/sidecar-script-0-9l9zj
 `},
 		VolumeMounts:    []corev1.VolumeMount{writeScriptsVolumeMount, binMount},
-		SecurityContext: windowsSecurityContext,
+		SecurityContext: WindowsSecurityContext,
 	}
 	want := []corev1.Container{{
 		Image: "step-1",

diff --git a/pkg/pod/workingdir_init.go b/pkg/pod/workingdir_init.go
@@ -60,9 +60,9 @@ func workingDirInit(workingdirinitImage string, stepContainers []corev1.Containe
 		// There are no workingDirs to initialize.
 		return nil
 	}
-	securityContext := linuxSecurityContext
+	securityContext := LinuxSecurityContext
 	if windows {
-		securityContext = windowsSecurityContext
+		securityContext = WindowsSecurityContext
 	}
 
 	c := &corev1.Container{

diff --git a/pkg/pod/workingdir_init_test.go b/pkg/pod/workingdir_init_test.go
@@ -90,7 +90,7 @@ func TestWorkingDirInit(t *testing.T) {
 			Args:            []string{"/workspace/bbb", "aaa", "zzz"},
 			WorkingDir:      pipeline.WorkspaceDir,
 			VolumeMounts:    implicitVolumeMounts,
-			SecurityContext: linuxSecurityContext,
+			SecurityContext: LinuxSecurityContext,
 		},
 	}, {
 		desc: "workingDirs are unique and sorted, absolute dirs are ignored, uses windows",
@@ -144,7 +144,7 @@ func TestWorkingDirInit(t *testing.T) {
 			Args:            []string{"/workspace/bbb", "aaa", "zzz"},
 			WorkingDir:      pipeline.WorkspaceDir,
 			VolumeMounts:    implicitVolumeMounts,
-			SecurityContext: windowsSecurityContext,
+			SecurityContext: WindowsSecurityContext,
 		},
 	}} {
 		t.Run(c.desc, func(t *testing.T) {

diff --git a/pkg/reconciler/pipelinerun/affinity_assistant.go b/pkg/reconciler/pipelinerun/affinity_assistant.go
@@ -29,6 +29,7 @@ import (
 	v1 "github.com/tektoncd/pipeline/pkg/apis/pipeline/v1"
 	"github.com/tektoncd/pipeline/pkg/internal/affinityassistant"
 	aa "github.com/tektoncd/pipeline/pkg/internal/affinityassistant"
+	pipelinePod "github.com/tektoncd/pipeline/pkg/pod"
 	"github.com/tektoncd/pipeline/pkg/reconciler/volumeclaim"
 	"github.com/tektoncd/pipeline/pkg/workspace"
 	appsv1 "k8s.io/api/apps/v1"
@@ -139,7 +140,12 @@ func (c *Reconciler) createOrUpdateAffinityAssistant(ctx context.Context, affini
 		if err != nil {
 			return []error{err}
 		}
-		affinityAssistantStatefulSet := affinityAssistantStatefulSet(aaBehavior, affinityAssistantName, pr, claimTemplates, claimNames, c.Images.NopImage, cfg.Defaults.DefaultAAPodTemplate)
+		affinityAssistantContainerConfig := aa.ContainerConfig{
+			Image:              c.Images.NopImage,
+			SetSecurityContext: cfg.FeatureFlags.SetSecurityContext,
+		}
+
+		affinityAssistantStatefulSet := affinityAssistantStatefulSet(aaBehavior, affinityAssistantName, pr, claimTemplates, claimNames, affinityAssistantContainerConfig, cfg.Defaults.DefaultAAPodTemplate)
 		_, err = c.KubeClientSet.AppsV1().StatefulSets(pr.Namespace).Create(ctx, affinityAssistantStatefulSet, metav1.CreateOptions{})
 		if err != nil {
 			errs = append(errs, fmt.Errorf("failed to create StatefulSet %s: %w", affinityAssistantName, err))
@@ -281,7 +287,7 @@ func getStatefulSetLabels(pr *v1.PipelineRun, affinityAssistantName string) map[
 // with the given AffinityAssistantTemplate applied to the StatefulSet PodTemplateSpec.
 // The VolumeClaimTemplates and Volume of StatefulSet reference the PipelineRun WorkspaceBinding VolumeClaimTempalte and the PVCs respectively.
 // The PVs created by the StatefulSet are scheduled to the same availability zone which avoids PV scheduling conflict.
-func affinityAssistantStatefulSet(aaBehavior aa.AffinityAssistantBehavior, name string, pr *v1.PipelineRun, claimTemplates []corev1.PersistentVolumeClaim, claimNames []string, affinityAssistantImage string, defaultAATpl *pod.AffinityAssistantTemplate) *appsv1.StatefulSet {
+func affinityAssistantStatefulSet(aaBehavior aa.AffinityAssistantBehavior, name string, pr *v1.PipelineRun, claimTemplates []corev1.PersistentVolumeClaim, claimNames []string, containerConfig aa.ContainerConfig, defaultAATpl *pod.AffinityAssistantTemplate) *appsv1.StatefulSet {
 	// We want a singleton pod
 	replicas := int32(1)
 
@@ -296,9 +302,18 @@ func affinityAssistantStatefulSet(aaBehavior aa.AffinityAssistantBehavior, name
 		mounts = append(mounts, corev1.VolumeMount{Name: claimTemplate.Name, MountPath: claimTemplate.Name})
 	}
 
+	securityContext := &corev1.SecurityContext{}
+	if containerConfig.SetSecurityContext {
+		securityContext = pipelinePod.LinuxSecurityContext
+
+		if tpl.NodeSelector[pipelinePod.OsSelectorLabel] == "windows" {
+			securityContext = pipelinePod.WindowsSecurityContext
+		}
+	}
+
 	containers := []corev1.Container{{
 		Name:  "affinity-assistant",
-		Image: affinityAssistantImage,
+		Image: containerConfig.Image,
 		Args:  []string{"tekton_run_indefinitely"},
 
 		// Set requests == limits to get QoS class _Guaranteed_.
@@ -314,7 +329,8 @@ func affinityAssistantStatefulSet(aaBehavior aa.AffinityAssistantBehavior, name
 				"memory": resource.MustParse("100Mi"),
 			},
 		},
-		VolumeMounts: mounts,
+		SecurityContext: securityContext,
+		VolumeMounts:    mounts,
 	}}
 
 	var volumes []corev1.Volume