Don't mount default ServiceAccount in pods

- Add security to components and default namespace by preventing user to
  mount default ServiceAccount to their pods.

- Add test for components.

Fixes #669

Signed-off-by: knrt10 <kautilya@kinvolk.io>

Author: knrt10

cli/cmd/cluster-apply.go

@@ -22,6 +22,7 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 
+	"github.com/kinvolk/lokomotive/pkg/components/util"
 	"github.com/kinvolk/lokomotive/pkg/install"
 	"github.com/kinvolk/lokomotive/pkg/k8sutil"
 	"github.com/kinvolk/lokomotive/pkg/lokomotive"
@@ -107,6 +108,10 @@ func runClusterApply(cmd *cobra.Command, args []string) {
 		}
 	}
 
+	if err := util.DisableAutomountServiceAccountToken("default", kubeconfigPath); err != nil {
+		ctxLogger.Fatalf("Applying patch to default service account failed: %v", err)
+	}
+
 	if skipComponents {
 		return
 	}

cli/cmd/component-apply.go

@@ -84,7 +84,12 @@ func applyComponents(lokoConfig *config.Config, kubeconfig string, componentName
 			return diags
 		}
 
-		if err := util.InstallComponent(component, kubeconfig); err != nil {
+		if err = util.InstallComponent(component, kubeconfig); err != nil {
+			return err
+		}
+
+		ns := component.Metadata().Namespace
+		if err = util.DisableAutomountServiceAccountToken(ns, kubeconfig); err != nil {
 			return err
 		}
 

pkg/components/util/install.go

@@ -16,6 +16,7 @@ package util
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 
@@ -29,6 +30,7 @@ import (
 
 	"github.com/kinvolk/lokomotive/pkg/components"
 	"github.com/kinvolk/lokomotive/pkg/k8sutil"
+	types "k8s.io/apimachinery/pkg/types"
 )
 
 func ensureNamespaceExists(name string, kubeconfigPath string) error {
@@ -59,6 +61,46 @@ func ensureNamespaceExists(name string, kubeconfigPath string) error {
 	return nil
 }
 
+// DisableAutomountServiceAccountToken updates default Service Account to not mount it in pods by default.
+func DisableAutomountServiceAccountToken(ns, kubeconfigPath string) error {
+	if ns == "" {
+		return fmt.Errorf("namespace name can't be empty")
+	}
+
+	kubeconfig, err := ioutil.ReadFile(kubeconfigPath) // #nosec G304
+	if err != nil {
+		return fmt.Errorf("reading kubeconfig file: %w", err)
+	}
+
+	cs, err := k8sutil.NewClientset(kubeconfig)
+	if err != nil {
+		return fmt.Errorf("creating clientset: %w", err)
+	}
+
+	payload := []patchUInt32Value{{
+		Op:    "add",
+		Path:  "/automountServiceAccountToken",
+		Value: false,
+	}}
+
+	payloadBytes, _ := json.Marshal(payload)
+
+	ctx := context.TODO()
+	sa, _ := cs.CoreV1().ServiceAccounts(ns).Get(ctx, "default", metav1.GetOptions{})
+
+	automountServiceAccountToken := sa.AutomountServiceAccountToken
+
+	if automountServiceAccountToken == nil {
+		//nolint:lll
+		_, err = cs.CoreV1().ServiceAccounts(ns).Patch(ctx, "default", types.JSONPatchType, payloadBytes, metav1.PatchOptions{})
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // InstallComponent installs given component using given kubeconfig as a Helm release using a Helm client.
 func InstallComponent(c components.Component, kubeconfig string) error {
 	name := c.Metadata().Name

pkg/components/util/types.go

@@ -78,3 +78,10 @@ func (n *NodeSelector) Render() (string, error) {
 
 	return string(b), nil
 }
+
+// patchUInt32Value specifies a patch operation for a uint32.
+type patchUInt32Value struct {
+	Op    string `json:"op"`
+	Path  string `json:"path"`
+	Value bool   `json:"value"`
+}

test/components/patch_serviceaccount_test.go

@@ -0,0 +1,101 @@
+// Copyright 2020 The Lokomotive 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.
+
+// +build aks aws aws_edge packet
+// +build e2e
+
+//nolint
+package components
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	_ "github.com/kinvolk/lokomotive/pkg/components/flatcar-linux-update-operator"
+	testutil "github.com/kinvolk/lokomotive/test/components/util"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/client-go/kubernetes"
+)
+
+const (
+	retryInterval  = time.Second * 5
+	timeout        = time.Minute * 5
+	contextTimeout = 10
+)
+
+type componentTestCase struct {
+	namespace string
+}
+
+func TestDisableAutomountServiceAccountToken(t *testing.T) {
+	client := testutil.CreateKubeClient(t)
+	ns, _ := client.CoreV1().Namespaces().List(context.TODO(), metav1.ListOptions{})
+
+	items := ns.Items
+
+	var componentTestCases []componentTestCase
+
+	for _, val := range items {
+		if !isSpecialNamespace(val.Name) {
+			componentTestCases = append(componentTestCases, componentTestCase{
+				namespace: val.Name,
+			})
+		}
+	}
+
+	for _, tc := range componentTestCases {
+		tc := tc
+		t.Run(tc.namespace, func(t *testing.T) {
+			t.Parallel()
+
+			if err := wait.PollImmediate(
+				retryInterval, timeout, checkDefaultServiceAccountPatch(client, tc),
+			); err != nil {
+				t.Fatalf("%v", err)
+			}
+		})
+	}
+}
+
+func checkDefaultServiceAccountPatch(client kubernetes.Interface, tc componentTestCase) wait.ConditionFunc {
+	return func() (done bool, err error) {
+		ctx, cancel := context.WithTimeout(context.Background(), contextTimeout*time.Second)
+		defer cancel()
+
+		sa, err := client.CoreV1().ServiceAccounts(tc.namespace).Get(ctx, "default", metav1.GetOptions{})
+		if err != nil {
+			return false, fmt.Errorf("error getting service account: %v", err)
+		}
+
+		automountServiceAccountToken := *sa.AutomountServiceAccountToken
+
+		if automountServiceAccountToken != false {
+			//nolint:lll
+			return false, fmt.Errorf("service account for namespace %q was not patched. Expected %v got %v", tc.namespace, false, automountServiceAccountToken)
+		}
+
+		return true, nil
+	}
+}
+
+func isSpecialNamespace(ns string) bool {
+	if ns == "kube-system" || ns == "kube-public" || ns == "kube-node-lease" {
+		return true
+	}
+
+	return false
+}