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Update kubeadm control-plane to run as non-root.

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This commit is contained in:
Vinayak Goyal 2021-06-09 14:59:03 -07:00
parent f3371ced85
commit 59b4b124df
5 changed files with 364 additions and 0 deletions
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26
cmd/kubeadm/app/phases/controlplane/manifests.go
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@ -34,6 +34,7 @@ import (
certphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
staticpodutil "k8s.io/kubernetes/cmd/kubeadm/app/util/staticpod"
"k8s.io/kubernetes/cmd/kubeadm/app/util/users"
utilsnet "k8s.io/utils/net"
)
@ -96,6 +97,19 @@ func CreateStaticPodFiles(manifestDir, patchesDir string, cfg *kubeadmapi.Cluste
klog.V(1).Infoln("[control-plane] getting StaticPodSpecs")
specs := GetStaticPodSpecs(cfg, endpoint)
var usersAndGroups *users.UsersAndGroups
var err error
if features.Enabled(cfg.FeatureGates, features.RootlessControlPlane) {
if isDryRun {
fmt.Printf("[dryrun] Would create users and groups for %+v to run as non-root\n", componentNames)
} else {
usersAndGroups, err = staticpodutil.GetUsersAndGroups()
if err != nil {
return errors.Wrap(err, "failed to create users and groups")
}
}
}
// creates required static pod specs
for _, componentName := range componentNames {
// retrieves the StaticPodSpec for given component
@ -109,6 +123,18 @@ func CreateStaticPodFiles(manifestDir, patchesDir string, cfg *kubeadmapi.Cluste
klog.V(2).Infof("[control-plane] adding volume %q for component %q", v.Name, componentName)
}
if features.Enabled(cfg.FeatureGates, features.RootlessControlPlane) {
if isDryRun {
fmt.Printf("[dryrun] Would update static pod manifest for %q to run run as non-root\n", componentName)
} else {
if usersAndGroups != nil {
if err := staticpodutil.RunComponentAsNonRoot(componentName, &spec, usersAndGroups, cfg); err != nil {
return errors.Wrapf(err, "failed to run component %q as non-root", componentName)
}
}
}
}
// if patchesDir is defined, patch the static Pod manifest
if patchesDir != "" {
patchedSpec, err := staticpodutil.PatchStaticPod(&spec, patchesDir, os.Stdout)

15
cmd/kubeadm/app/util/staticpod/utils.go
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@ -26,6 +26,7 @@ import (
"os"
"sort"
"strings"
"sync"
"github.com/pkg/errors"
@ -37,6 +38,7 @@ import (
kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
"k8s.io/kubernetes/cmd/kubeadm/app/util/patches"
"k8s.io/kubernetes/cmd/kubeadm/app/util/users"
)
const (
@ -47,6 +49,11 @@ const (
kubeSchedulerBindAddressArg = "bind-address"
)
var (
usersAndGroups *users.UsersAndGroups
usersAndGroupsOnce sync.Once
)
// ComponentPod returns a Pod object from the container, volume and annotations specifications
func ComponentPod(container v1.Container, volumes map[string]v1.Volume, annotations map[string]string) v1.Pod {
return v1.Pod{
@ -378,3 +385,11 @@ func getProbeAddress(addr string) string {
}
return addr
}
func GetUsersAndGroups() (*users.UsersAndGroups, error) {
var err error
usersAndGroupsOnce.Do(func() {
usersAndGroups, err = users.AddUsersAndGroups()
})
return usersAndGroups, err
}

158
cmd/kubeadm/app/util/staticpod/utils_linux.go Normal file
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@ -0,0 +1,158 @@
// +build linux
/*
Copyright 2021 The Kubernetes 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.
*/
package staticpod
import (
"fmt"
"path/filepath"
"github.com/pkg/errors"
v1 "k8s.io/api/core/v1"
kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
certphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
"k8s.io/kubernetes/cmd/kubeadm/app/util/users"
"k8s.io/utils/pointer"
)
type pathOwerAndPermissionsUpdaterFunc func(path string, uid, gid int64, perms uint32) error
// RunComponentAsNonRoot updates the pod manifest and the hostVolume permissions to run as non root.
func RunComponentAsNonRoot(componentName string, pod *v1.Pod, usersAndGroups *users.UsersAndGroups, cfg *kubeadmapi.ClusterConfiguration) error {
switch componentName {
case kubeadmconstants.KubeAPIServer:
return runKubeAPIServerAsNonRoot(
pod,
usersAndGroups.Users.ID(kubeadmconstants.KubeAPIServerUserName),
usersAndGroups.Groups.ID(kubeadmconstants.KubeAPIServerUserName),
usersAndGroups.Groups.ID(kubeadmconstants.ServiceAccountKeyReadersGroupName),
users.UpdatePathOwnerAndPermissions,
cfg,
)
case kubeadmconstants.KubeControllerManager:
return runKubeControllerManagerAsNonRoot(
pod,
usersAndGroups.Users.ID(kubeadmconstants.KubeControllerManagerUserName),
usersAndGroups.Groups.ID(kubeadmconstants.KubeControllerManagerUserName),
usersAndGroups.Groups.ID(kubeadmconstants.ServiceAccountKeyReadersGroupName),
users.UpdatePathOwnerAndPermissions,
cfg,
)
case kubeadmconstants.KubeScheduler:
return runKubeSchedulerAsNonRoot(
pod,
usersAndGroups.Users.ID(kubeadmconstants.KubeControllerManagerUserName),
usersAndGroups.Groups.ID(kubeadmconstants.KubeControllerManagerUserName),
users.UpdatePathOwnerAndPermissions,
)
}
return errors.New(fmt.Sprintf("component name %q is not valid", componentName))
}
// runKubeAPIServerAsNonRoot updates the pod manifest and the hostVolume permissions to run kube-apiserver as non root.
func runKubeAPIServerAsNonRoot(pod *v1.Pod, runAsUser, runAsGroup, supplementalGroup *int64, updatePathOwnerAndPermissions pathOwerAndPermissionsUpdaterFunc, cfg *kubeadmapi.ClusterConfiguration) error {
saPublicKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPublicKeyName)
if err := updatePathOwnerAndPermissions(saPublicKeyFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
saPrivateKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPrivateKeyName)
if err := updatePathOwnerAndPermissions(saPrivateKeyFile, 0, *supplementalGroup, 0640); err != nil {
return err
}
apiServerKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerKeyName)
if err := updatePathOwnerAndPermissions(apiServerKeyFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
apiServerKubeletClientKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerKubeletClientKeyName)
if err := updatePathOwnerAndPermissions(apiServerKubeletClientKeyFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
frontProxyClientKeyName := filepath.Join(cfg.CertificatesDir, kubeadmconstants.FrontProxyClientKeyName)
if err := updatePathOwnerAndPermissions(frontProxyClientKeyName, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
if cfg.Etcd.External == nil {
apiServerEtcdClientKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerEtcdClientKeyName)
if err := updatePathOwnerAndPermissions(apiServerEtcdClientKeyFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
}
pod.Spec.Containers[0].SecurityContext = &v1.SecurityContext{
Capabilities: &v1.Capabilities{
// We drop all capabilities that are added by default.
Drop: []v1.Capability{"ALL"},
// kube-apiserver binary has the file capability cap_net_bind_service applied to it.
// This means that we must add this capability when running as non-root even if the
// capability is not required.
Add: []v1.Capability{"NET_BIND_SERVICE"},
},
}
pod.Spec.SecurityContext.RunAsGroup = runAsGroup
pod.Spec.SecurityContext.RunAsUser = runAsUser
pod.Spec.SecurityContext.SupplementalGroups = []int64{*supplementalGroup}
return nil
}
// runKubeControllerManagerAsNonRoot updates the pod manifest and the hostVolume permissions to run kube-controller-manager as non root.
func runKubeControllerManagerAsNonRoot(pod *v1.Pod, runAsUser, runAsGroup, supplementalGroup *int64, updatePathOwnerAndPermissions pathOwerAndPermissionsUpdaterFunc, cfg *kubeadmapi.ClusterConfiguration) error {
kubeconfigFile := filepath.Join(kubeadmconstants.KubernetesDir, kubeadmconstants.ControllerManagerKubeConfigFileName)
if err := updatePathOwnerAndPermissions(kubeconfigFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
saPrivateKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPrivateKeyName)
if err := updatePathOwnerAndPermissions(saPrivateKeyFile, 0, *supplementalGroup, 0640); err != nil {
return err
}
if res, _ := certphase.UsingExternalCA(cfg); !res {
caKeyFile := filepath.Join(cfg.CertificatesDir, kubeadmconstants.CAKeyName)
err := updatePathOwnerAndPermissions(caKeyFile, *runAsUser, *runAsGroup, 0600)
if err != nil {
return err
}
}
pod.Spec.Containers[0].SecurityContext = &v1.SecurityContext{
AllowPrivilegeEscalation: pointer.Bool(false),
Capabilities: &v1.Capabilities{
// We drop all capabilities that are added by default.
Drop: []v1.Capability{"ALL"},
},
}
pod.Spec.SecurityContext.RunAsUser = runAsUser
pod.Spec.SecurityContext.RunAsGroup = runAsGroup
pod.Spec.SecurityContext.SupplementalGroups = []int64{*supplementalGroup}
return nil
}
// runKubeSchedulerAsNonRoot updates the pod manifest and the hostVolume permissions to run kube-scheduler as non root.
func runKubeSchedulerAsNonRoot(pod *v1.Pod, runAsUser, runAsGroup *int64, updatePathOwnerAndPermissions pathOwerAndPermissionsUpdaterFunc) error {
kubeconfigFile := filepath.Join(kubeadmconstants.KubernetesDir, kubeadmconstants.SchedulerKubeConfigFileName)
if err := updatePathOwnerAndPermissions(kubeconfigFile, *runAsUser, *runAsGroup, 0600); err != nil {
return err
}
pod.Spec.Containers[0].SecurityContext = &v1.SecurityContext{
AllowPrivilegeEscalation: pointer.Bool(false),
// We drop all capabilities that are added by default.
Capabilities: &v1.Capabilities{
Drop: []v1.Capability{"ALL"},
},
}
pod.Spec.SecurityContext.RunAsUser = runAsUser
pod.Spec.SecurityContext.RunAsGroup = runAsGroup
return nil
}

135
cmd/kubeadm/app/util/staticpod/utils_linux_test.go Normal file
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@ -0,0 +1,135 @@
// +build linux
/*
Copyright 2021 The Kubernetes 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.
*/
package staticpod
import (
"path/filepath"
"reflect"
"testing"
v1 "k8s.io/api/core/v1"
"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
"k8s.io/utils/pointer"
)
type ownerAndPermissions struct {
uid int64
gid int64
permissions uint32
}
func verifyPodSecurityContext(t *testing.T, pod *v1.Pod, wantRunAsUser, wantRunAsGroup int64, wantSupGroup []int64) {
t.Helper()
wantPodSecurityContext := &v1.PodSecurityContext{
RunAsUser: pointer.Int64(wantRunAsUser),
RunAsGroup: pointer.Int64(wantRunAsGroup),
SupplementalGroups: wantSupGroup,
SeccompProfile: &v1.SeccompProfile{
Type: v1.SeccompProfileTypeRuntimeDefault,
},
}
if !reflect.DeepEqual(wantPodSecurityContext, pod.Spec.SecurityContext) {
t.Errorf("unexpected diff in PodSecurityContext, want: %+v, got: %+v", wantPodSecurityContext, pod.Spec.SecurityContext)
}
}
func verifyContainerSecurityContext(t *testing.T, container v1.Container, addCaps, dropCaps []v1.Capability, allowPrivielege *bool) {
t.Helper()
wantContainerSecurityContext := &v1.SecurityContext{
AllowPrivilegeEscalation: allowPrivielege,
Capabilities: &v1.Capabilities{
Add: addCaps,
Drop: dropCaps,
},
}
if !reflect.DeepEqual(wantContainerSecurityContext, container.SecurityContext) {
t.Errorf("unexpected diff in container SecurityContext, want: %+v, got: %+v", wantContainerSecurityContext, container.SecurityContext)
}
}
func verifyFilePermissions(t *testing.T, updatedFiles, wantFiles map[string]ownerAndPermissions) {
t.Helper()
if !reflect.DeepEqual(updatedFiles, wantFiles) {
t.Errorf("unexpected diff in file owners and permissions want: %+v, got: %+v", wantFiles, updatedFiles)
}
}
func TestRunKubeAPIServerAsNonRoot(t *testing.T) {
cfg := &kubeadm.ClusterConfiguration{}
pod := ComponentPod(v1.Container{Name: "kube-apiserver"}, nil, nil)
var runAsUser, runAsGroup, supGroup int64 = 1000, 1001, 1002
updatedFiles := map[string]ownerAndPermissions{}
if err := runKubeAPIServerAsNonRoot(&pod, &runAsUser, &runAsGroup, &supGroup, func(path string, uid, gid int64, perms uint32) error {
updatedFiles[path] = ownerAndPermissions{uid: uid, gid: gid, permissions: perms}
return nil
}, cfg); err != nil {
t.Fatal(err)
}
verifyPodSecurityContext(t, &pod, runAsUser, runAsGroup, []int64{supGroup})
verifyContainerSecurityContext(t, pod.Spec.Containers[0], []v1.Capability{"NET_BIND_SERVICE"}, []v1.Capability{"ALL"}, nil)
wantUpdateFiles := map[string]ownerAndPermissions{
filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPublicKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPrivateKeyName): {uid: 0, gid: supGroup, permissions: 0640},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerKubeletClientKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.FrontProxyClientKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.APIServerEtcdClientKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
}
verifyFilePermissions(t, updatedFiles, wantUpdateFiles)
}
func TestRunKubeControllerManagerAsNonRoot(t *testing.T) {
cfg := &kubeadm.ClusterConfiguration{}
pod := ComponentPod(v1.Container{Name: "kube-controller-manager"}, nil, nil)
var runAsUser, runAsGroup, supGroup int64 = 1000, 1001, 1002
updatedFiles := map[string]ownerAndPermissions{}
if err := runKubeControllerManagerAsNonRoot(&pod, &runAsUser, &runAsGroup, &supGroup, func(path string, uid, gid int64, perms uint32) error {
updatedFiles[path] = ownerAndPermissions{uid: uid, gid: gid, permissions: perms}
return nil
}, cfg); err != nil {
t.Fatal(err)
}
verifyPodSecurityContext(t, &pod, runAsUser, runAsGroup, []int64{supGroup})
verifyContainerSecurityContext(t, pod.Spec.Containers[0], nil, []v1.Capability{"ALL"}, pointer.Bool(false))
wantUpdateFiles := map[string]ownerAndPermissions{
filepath.Join(kubeadmconstants.KubernetesDir, kubeadmconstants.ControllerManagerKubeConfigFileName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.ServiceAccountPrivateKeyName): {uid: 0, gid: supGroup, permissions: 0640},
filepath.Join(cfg.CertificatesDir, kubeadmconstants.CAKeyName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
}
verifyFilePermissions(t, updatedFiles, wantUpdateFiles)
}
func TestRunKubeSchedulerAsNonRoot(t *testing.T) {
pod := ComponentPod(v1.Container{Name: "kube-scheduler"}, nil, nil)
var runAsUser, runAsGroup int64 = 1000, 1001
updatedFiles := map[string]ownerAndPermissions{}
if err := runKubeSchedulerAsNonRoot(&pod, &runAsUser, &runAsGroup, func(path string, uid, gid int64, perms uint32) error {
updatedFiles[path] = ownerAndPermissions{uid: uid, gid: gid, permissions: perms}
return nil
}); err != nil {
t.Fatal(err)
}
verifyPodSecurityContext(t, &pod, runAsUser, runAsGroup, nil)
verifyContainerSecurityContext(t, pod.Spec.Containers[0], nil, []v1.Capability{"ALL"}, pointer.Bool(false))
wantUpdateFiles := map[string]ownerAndPermissions{
filepath.Join(kubeadmconstants.KubernetesDir, kubeadmconstants.SchedulerKubeConfigFileName): {uid: runAsUser, gid: runAsGroup, permissions: 0600},
}
verifyFilePermissions(t, updatedFiles, wantUpdateFiles)
}

30
cmd/kubeadm/app/util/staticpod/utils_others.go Normal file
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@ -0,0 +1,30 @@
// +build !linux
/*
Copyright 2021 The Kubernetes 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.
*/
package staticpod
import (
v1 "k8s.io/api/core/v1"
kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
"k8s.io/kubernetes/cmd/kubeadm/app/util/users"
)
// RunComponentAsNonRoot is a NO-OP on non linux.
func RunComponentAsNonRoot(componentName string, pod *v1.Pod, usersAndGroups *users.UsersAndGroups, cfg *kubeadmapi.ClusterConfiguration) error {
return nil
}