kubectl debug: add netadmin profile

Add the netadmin profile from KEP 1441
https://github.com/kubernetes/enhancements/tree/master/keps/sig-cli/1441-kubectl-debug#debugging-profiles

Signed-off-by: Will Daly <widaly@microsoft.com>

staging/src/k8s.io/kubectl/pkg/cmd/debug/debug.go

@@ -190,7 +190,7 @@ func (o *DebugOptions) AddFlags(cmd *cobra.Command) {
 	cmd.Flags().BoolVar(&o.ShareProcesses, "share-processes", o.ShareProcesses, i18n.T("When used with '--copy-to', enable process namespace sharing in the copy."))
 	cmd.Flags().StringVar(&o.TargetContainer, "target", "", i18n.T("When using an ephemeral container, target processes in this container name."))
 	cmd.Flags().BoolVarP(&o.TTY, "tty", "t", o.TTY, i18n.T("Allocate a TTY for the debugging container."))
-	cmd.Flags().StringVar(&o.Profile, "profile", ProfileLegacy, i18n.T(`Debugging profile. Options are "legacy", "general", "baseline", or "restricted".`))
+	cmd.Flags().StringVar(&o.Profile, "profile", ProfileLegacy, i18n.T(`Debugging profile. Options are "legacy", "general", "baseline", "netadmin", or "restricted".`))
 }
 
 // Complete finishes run-time initialization of debug.DebugOptions.

staging/src/k8s.io/kubectl/pkg/cmd/debug/debug_test.go

@@ -294,6 +294,27 @@ func TestGenerateDebugContainer(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "netadmin profile",
+			opts: &DebugOptions{
+				Image:      "busybox",
+				PullPolicy: corev1.PullIfNotPresent,
+				Profile:    ProfileNetadmin,
+			},
+			expected: &corev1.EphemeralContainer{
+				EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+					Name:                     "debugger-1",
+					Image:                    "busybox",
+					ImagePullPolicy:          corev1.PullIfNotPresent,
+					TerminationMessagePolicy: corev1.TerminationMessageReadFile,
+					SecurityContext: &corev1.SecurityContext{
+						Capabilities: &corev1.Capabilities{
+							Add: []corev1.Capability{"NET_ADMIN"},
+						},
+					},
+				},
+			},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			tc.opts.IOStreams = genericclioptions.NewTestIOStreamsDiscard()

staging/src/k8s.io/kubectl/pkg/cmd/debug/profiles.go

@@ -52,6 +52,8 @@ const (
 	// ProfileRestricted is identical to "baseline" but adds configuration that's required
 	// under the restricted security profile, such as requiring a non-root user and dropping all capabilities.
 	ProfileRestricted = "restricted"
+	// ProfileNetadmin offers elevated privileges for network debugging.
+	ProfileNetadmin = "netadmin"
 )
 
 type ProfileApplier interface {
@@ -70,6 +72,8 @@ func NewProfileApplier(profile string) (ProfileApplier, error) {
 		return &baselineProfile{}, nil
 	case ProfileRestricted:
 		return &restrictedProfile{}, nil
+	case ProfileNetadmin:
+		return &netadminProfile{}, nil
 	}
 
 	return nil, fmt.Errorf("unknown profile: %s", profile)
@@ -87,6 +91,9 @@ type baselineProfile struct {
 type restrictedProfile struct {
 }
 
+type netadminProfile struct {
+}
+
 func (p *legacyProfile) Apply(pod *corev1.Pod, containerName string, target runtime.Object) error {
 	switch target.(type) {
 	case *corev1.Pod:
@@ -183,6 +190,26 @@ func (p *restrictedProfile) Apply(pod *corev1.Pod, containerName string, target
 	return nil
 }
 
+func (p *netadminProfile) Apply(pod *corev1.Pod, containerName string, target runtime.Object) error {
+	style, err := getDebugStyle(pod, target)
+	if err != nil {
+		return fmt.Errorf("netadmin profile: %s", err)
+	}
+
+	allowNetadminCapability(pod, containerName)
+
+	switch style {
+	case node:
+		useHostNamespaces(pod)
+		setPrivileged(pod, containerName)
+
+	case podCopy, ephemeral:
+		// no additional modifications needed
+	}
+
+	return nil
+}
+
 // removeLabelsAndProbes removes labels from the pod and remove probes
 // from all containers of the pod.
 func removeLabelsAndProbes(p *corev1.Pod) {
@@ -239,6 +266,20 @@ func clearSecurityContext(p *corev1.Pod, containerName string) {
 	})
 }
 
+// setPrivileged configures the containers as privileged.
+func setPrivileged(p *corev1.Pod, containerName string) {
+	podutils.VisitContainers(&p.Spec, podutils.AllContainers, func(c *corev1.Container, _ podutils.ContainerType) bool {
+		if c.Name != containerName {
+			return true
+		}
+		if c.SecurityContext == nil {
+			c.SecurityContext = &corev1.SecurityContext{}
+		}
+		c.SecurityContext.Privileged = pointer.BoolPtr(true)
+		return false
+	})
+}
+
 // disallowRoot configures the container to run as a non-root user.
 func disallowRoot(p *corev1.Pod, containerName string) {
 	podutils.VisitContainers(&p.Spec, podutils.AllContainers, func(c *corev1.Container, _ podutils.ContainerType) bool {
@@ -274,13 +315,28 @@ func allowProcessTracing(p *corev1.Pod, containerName string) {
 		if c.Name != containerName {
 			return true
 		}
-		if c.SecurityContext == nil {
-			c.SecurityContext = &corev1.SecurityContext{}
-		}
-		if c.SecurityContext.Capabilities == nil {
-			c.SecurityContext.Capabilities = &corev1.Capabilities{}
-		}
-		c.SecurityContext.Capabilities.Add = append(c.SecurityContext.Capabilities.Add, "SYS_PTRACE")
+		addCapability(c, "SYS_PTRACE")
 		return false
 	})
 }
+
+// allowNetadminCapability grants NET_ADMIN capability to the container.
+func allowNetadminCapability(p *corev1.Pod, containerName string) {
+	podutils.VisitContainers(&p.Spec, podutils.AllContainers, func(c *corev1.Container, _ podutils.ContainerType) bool {
+		if c.Name != containerName {
+			return true
+		}
+		addCapability(c, "NET_ADMIN")
+		return false
+	})
+}
+
+func addCapability(c *corev1.Container, capability corev1.Capability) {
+	if c.SecurityContext == nil {
+		c.SecurityContext = &corev1.SecurityContext{}
+	}
+	if c.SecurityContext.Capabilities == nil {
+		c.SecurityContext.Capabilities = &corev1.Capabilities{}
+	}
+	c.SecurityContext.Capabilities.Add = append(c.SecurityContext.Capabilities.Add, capability)
+}

staging/src/k8s.io/kubectl/pkg/cmd/debug/profiles_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package debug
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -430,3 +431,140 @@ func TestRestrictedProfile(t *testing.T) {
 		})
 	}
 }
+
+func TestNetAdminProfile(t *testing.T) {
+	pod := &corev1.Pod{
+		ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+		Spec: corev1.PodSpec{EphemeralContainers: []corev1.EphemeralContainer{
+			{
+				EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+					Name: "dbg", Image: "dbgimage",
+				},
+			},
+		}},
+	}
+
+	tests := []struct {
+		name          string
+		pod           *corev1.Pod
+		containerName string
+		target        runtime.Object
+		expectPod     *corev1.Pod
+		expectErr     error
+	}{
+		{
+			name:          "nil target",
+			pod:           pod,
+			containerName: "dbg",
+			target:        nil,
+			expectErr:     fmt.Errorf("netadmin profile: objects of type <nil> are not supported"),
+		},
+		{
+			name:          "debug by ephemeral container",
+			pod:           pod,
+			containerName: "dbg",
+			target:        pod,
+			expectPod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Spec: corev1.PodSpec{EphemeralContainers: []corev1.EphemeralContainer{
+					{
+						EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+							Name: "dbg", Image: "dbgimage",
+							SecurityContext: &corev1.SecurityContext{
+								Capabilities: &corev1.Capabilities{
+									Add: []corev1.Capability{"NET_ADMIN"},
+								},
+							},
+						},
+					},
+				}},
+			},
+		},
+		{
+			name: "debug by pod copy",
+			pod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "podcopy"},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{Name: "app", Image: "appimage"},
+						{Name: "dbg", Image: "dbgimage"},
+					},
+				},
+			},
+			containerName: "dbg",
+			target: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "podcopy"},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{Name: "app", Image: "appimage"},
+					},
+				},
+			},
+			expectPod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "podcopy"},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{Name: "app", Image: "appimage"},
+						{
+							Name:  "dbg",
+							Image: "dbgimage",
+							SecurityContext: &corev1.SecurityContext{
+								Capabilities: &corev1.Capabilities{
+									Add: []corev1.Capability{"NET_ADMIN"},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "debug by node",
+			pod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{Name: "dbg", Image: "dbgimage"},
+					},
+				},
+			},
+			containerName: "dbg",
+			target:        testNode,
+			expectPod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Spec: corev1.PodSpec{
+					HostNetwork: true,
+					HostPID:     true,
+					HostIPC:     true,
+					Containers: []corev1.Container{
+						{
+							Name:  "dbg",
+							Image: "dbgimage",
+							SecurityContext: &corev1.SecurityContext{
+								Privileged: pointer.BoolPtr(true),
+								Capabilities: &corev1.Capabilities{
+									Add: []corev1.Capability{"NET_ADMIN"},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			err := (&netadminProfile{}).Apply(test.pod, test.containerName, test.target)
+			if (err == nil) != (test.expectErr == nil) || (err != nil && test.expectErr != nil && err.Error() != test.expectErr.Error()) {
+				t.Fatalf("expect error: %v, got error: %v", test.expectErr, err)
+			}
+			if err != nil {
+				return
+			}
+			if diff := cmp.Diff(test.expectPod, test.pod); diff != "" {
+				t.Error("unexpected diff in generated object: (-want +got):\n", diff)
+			}
+		})
+	}
+}