test: preventing serviceaccount privilege escalation

Author: prometherion

e2e/sa_prevent_privilege_escalation_test.go

@@ -0,0 +1,146 @@
+//go:build e2e
+
+// Copyright 2020-2021 Clastix Labs
+// SPDX-License-Identifier: Apache-2.0
+
+package e2e
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	rbacv1 "k8s.io/api/rbac/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/uuid"
+	"k8s.io/client-go/kubernetes"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
+
+	capsulev1beta1 "github.com/clastix/capsule/api/v1beta1"
+)
+
+var _ = Describe("trying to escalate from a Tenant Namespace ServiceAccount", func() {
+	tnt := &capsulev1beta1.Tenant{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "sa-privilege-escalation",
+		},
+		Spec: capsulev1beta1.TenantSpec{
+			Owners: capsulev1beta1.OwnerListSpec{
+				{
+					Name: "mario",
+					Kind: "User",
+				},
+			},
+			NodeSelector: map[string]string{
+				"kubernetes.io/os": "linux",
+			},
+		},
+	}
+
+	ns := NewNamespace("attack")
+
+	JustBeforeEach(func() {
+		EventuallyCreation(func() error {
+			return k8sClient.Create(context.TODO(), tnt)
+		}).Should(Succeed())
+
+		NamespaceCreation(ns, tnt.Spec.Owners[0], defaultTimeoutInterval).Should(Succeed())
+		TenantNamespaceList(tnt, defaultTimeoutInterval).Should(ContainElement(ns.GetName()))
+	})
+
+	JustAfterEach(func() {
+		Expect(k8sClient.Delete(context.TODO(), tnt)).Should(Succeed())
+	})
+
+	It("should block Namespace changes", func() {
+		role := rbacv1.Role{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "ns-update-role",
+				Namespace: ns.GetName(),
+			},
+			Rules: []rbacv1.PolicyRule{
+				{
+					Verbs:         []string{"update"},
+					APIGroups:     []string{""},
+					Resources:     []string{"namespaces"},
+					ResourceNames: []string{ns.GetName()},
+				},
+			},
+		}
+
+		EventuallyCreation(func() error {
+			return k8sClient.Create(context.Background(), &role)
+		}).Should(Succeed())
+
+		rolebinding := rbacv1.RoleBinding{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "attacker-rolebinding",
+				Namespace: ns.GetName(),
+			},
+			Subjects: []rbacv1.Subject{
+				{
+					Kind:      "ServiceAccount",
+					Name:      "attacker",
+					Namespace: ns.GetName(),
+				},
+			},
+			RoleRef: rbacv1.RoleRef{
+				APIGroup: "rbac.authorization.k8s.io",
+				Kind:     "Role",
+				Name:     role.GetName(),
+			},
+		}
+
+		EventuallyCreation(func() error {
+			return k8sClient.Create(context.Background(), &rolebinding)
+		}).Should(Succeed())
+
+		c, err := config.GetConfig()
+		Expect(err).ToNot(HaveOccurred())
+		c.Impersonate.Groups = []string{"system:serviceaccounts"}
+		c.Impersonate.UserName = fmt.Sprintf("system:serviceaccount:%s:%s", rolebinding.Subjects[0].Namespace, rolebinding.Subjects[0].Name)
+		saClient, err := kubernetes.NewForConfig(c)
+		Expect(err).ToNot(HaveOccurred())
+		// Changing Owner Reference is forbidden
+		Consistently(func() error {
+			if err := k8sClient.Get(context.Background(), types.NamespacedName{Name: ns.GetName()}, ns); err != nil {
+				return err
+			}
+
+			ns.OwnerReferences[0].UID = uuid.NewUUID()
+
+			_, err = saClient.CoreV1().Namespaces().Update(context.Background(), ns, metav1.UpdateOptions{})
+
+			return err
+		}, 10*time.Second, time.Second).ShouldNot(Succeed())
+		// Removing Owner Reference is forbidden
+		Consistently(func() error {
+			if err := k8sClient.Get(context.Background(), types.NamespacedName{Name: ns.GetName()}, ns); err != nil {
+				return err
+			}
+
+			ns.SetOwnerReferences(nil)
+
+			_, err = saClient.CoreV1().Namespaces().Update(context.Background(), ns, metav1.UpdateOptions{})
+
+			return err
+		}, 10*time.Second, time.Second).ShouldNot(Succeed())
+		// Breaking nodeSelector is forbidden
+		Consistently(func() error {
+			if err := k8sClient.Get(context.Background(), types.NamespacedName{Name: ns.GetName()}, ns); err != nil {
+				return err
+			}
+
+			ns.SetAnnotations(map[string]string{
+				"scheduler.alpha.kubernetes.io/node-selector": "kubernetes.io/os=forbidden",
+			})
+
+			_, err = saClient.CoreV1().Namespaces().Update(context.Background(), ns, metav1.UpdateOptions{})
+
+			return err
+		}, 10*time.Second, time.Second).ShouldNot(Succeed())
+	})
+})