kubernetes/pkg/volume/secret/secret.go
Tero Saarni 96306f144a Set permissions on volume before publishing update
This change fixes a race condition that was caused by setting the file owner,
group and mode non-atomically, after the updated files had been published.

Users who were running non-root containers, without GID 0 permissions, and
had removed read permissions from other users by setting defaultMode: 0440 or
similar, were getting intermittent permission denied errors when accessing
files on secret or configmap volumes or service account tokens on projected
volumes during update.
2022-12-24 07:59:41 +02:00

336 lines
9.2 KiB
Go

/*
Copyright 2015 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 secret
import (
"fmt"
"k8s.io/klog/v2"
"k8s.io/mount-utils"
utilstrings "k8s.io/utils/strings"
v1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/types"
"k8s.io/kubernetes/pkg/volume"
volumeutil "k8s.io/kubernetes/pkg/volume/util"
)
// ProbeVolumePlugins is the entry point for plugin detection in a package.
func ProbeVolumePlugins() []volume.VolumePlugin {
return []volume.VolumePlugin{&secretPlugin{}}
}
const (
secretPluginName = "kubernetes.io/secret"
)
// secretPlugin implements the VolumePlugin interface.
type secretPlugin struct {
host volume.VolumeHost
getSecret func(namespace, name string) (*v1.Secret, error)
}
var _ volume.VolumePlugin = &secretPlugin{}
func wrappedVolumeSpec() volume.Spec {
return volume.Spec{
Volume: &v1.Volume{VolumeSource: v1.VolumeSource{EmptyDir: &v1.EmptyDirVolumeSource{Medium: v1.StorageMediumMemory}}},
}
}
func getPath(uid types.UID, volName string, host volume.VolumeHost) string {
return host.GetPodVolumeDir(uid, utilstrings.EscapeQualifiedName(secretPluginName), volName)
}
func (plugin *secretPlugin) Init(host volume.VolumeHost) error {
plugin.host = host
plugin.getSecret = host.GetSecretFunc()
return nil
}
func (plugin *secretPlugin) GetPluginName() string {
return secretPluginName
}
func (plugin *secretPlugin) GetVolumeName(spec *volume.Spec) (string, error) {
volumeSource, _ := getVolumeSource(spec)
if volumeSource == nil {
return "", fmt.Errorf("Spec does not reference a Secret volume type")
}
return volumeSource.SecretName, nil
}
func (plugin *secretPlugin) CanSupport(spec *volume.Spec) bool {
return spec.Volume != nil && spec.Volume.Secret != nil
}
func (plugin *secretPlugin) RequiresRemount(spec *volume.Spec) bool {
return true
}
func (plugin *secretPlugin) SupportsMountOption() bool {
return false
}
func (plugin *secretPlugin) SupportsBulkVolumeVerification() bool {
return false
}
func (plugin *secretPlugin) SupportsSELinuxContextMount(spec *volume.Spec) (bool, error) {
return false, nil
}
func (plugin *secretPlugin) NewMounter(spec *volume.Spec, pod *v1.Pod, opts volume.VolumeOptions) (volume.Mounter, error) {
return &secretVolumeMounter{
secretVolume: &secretVolume{
spec.Name(),
pod.UID,
plugin,
plugin.host.GetMounter(plugin.GetPluginName()),
volume.NewCachedMetrics(volume.NewMetricsDu(getPath(pod.UID, spec.Name(), plugin.host))),
},
source: *spec.Volume.Secret,
pod: *pod,
opts: &opts,
getSecret: plugin.getSecret,
}, nil
}
func (plugin *secretPlugin) NewUnmounter(volName string, podUID types.UID) (volume.Unmounter, error) {
return &secretVolumeUnmounter{
&secretVolume{
volName,
podUID,
plugin,
plugin.host.GetMounter(plugin.GetPluginName()),
volume.NewCachedMetrics(volume.NewMetricsDu(getPath(podUID, volName, plugin.host))),
},
}, nil
}
func (plugin *secretPlugin) ConstructVolumeSpec(volName, mountPath string) (volume.ReconstructedVolume, error) {
secretVolume := &v1.Volume{
Name: volName,
VolumeSource: v1.VolumeSource{
Secret: &v1.SecretVolumeSource{
SecretName: volName,
},
},
}
return volume.ReconstructedVolume{
Spec: volume.NewSpecFromVolume(secretVolume),
}, nil
}
type secretVolume struct {
volName string
podUID types.UID
plugin *secretPlugin
mounter mount.Interface
volume.MetricsProvider
}
var _ volume.Volume = &secretVolume{}
func (sv *secretVolume) GetPath() string {
return getPath(sv.podUID, sv.volName, sv.plugin.host)
}
// secretVolumeMounter handles retrieving secrets from the API server
// and placing them into the volume on the host.
type secretVolumeMounter struct {
*secretVolume
source v1.SecretVolumeSource
pod v1.Pod
opts *volume.VolumeOptions
getSecret func(namespace, name string) (*v1.Secret, error)
}
var _ volume.Mounter = &secretVolumeMounter{}
func (sv *secretVolume) GetAttributes() volume.Attributes {
return volume.Attributes{
ReadOnly: true,
Managed: true,
SELinuxRelabel: true,
}
}
func (b *secretVolumeMounter) SetUp(mounterArgs volume.MounterArgs) error {
return b.SetUpAt(b.GetPath(), mounterArgs)
}
func (b *secretVolumeMounter) SetUpAt(dir string, mounterArgs volume.MounterArgs) error {
klog.V(3).Infof("Setting up volume %v for pod %v at %v", b.volName, b.pod.UID, dir)
// Wrap EmptyDir, let it do the setup.
wrapped, err := b.plugin.host.NewWrapperMounter(b.volName, wrappedVolumeSpec(), &b.pod, *b.opts)
if err != nil {
return err
}
optional := b.source.Optional != nil && *b.source.Optional
secret, err := b.getSecret(b.pod.Namespace, b.source.SecretName)
if err != nil {
if !(errors.IsNotFound(err) && optional) {
klog.Errorf("Couldn't get secret %v/%v: %v", b.pod.Namespace, b.source.SecretName, err)
return err
}
secret = &v1.Secret{
ObjectMeta: metav1.ObjectMeta{
Namespace: b.pod.Namespace,
Name: b.source.SecretName,
},
}
}
totalBytes := totalSecretBytes(secret)
klog.V(3).Infof("Received secret %v/%v containing (%v) pieces of data, %v total bytes",
b.pod.Namespace,
b.source.SecretName,
len(secret.Data),
totalBytes)
payload, err := MakePayload(b.source.Items, secret, b.source.DefaultMode, optional)
if err != nil {
return err
}
setupSuccess := false
if err := wrapped.SetUpAt(dir, mounterArgs); err != nil {
return err
}
if err := volumeutil.MakeNestedMountpoints(b.volName, dir, b.pod); err != nil {
return err
}
defer func() {
// Clean up directories if setup fails
if !setupSuccess {
unmounter, unmountCreateErr := b.plugin.NewUnmounter(b.volName, b.podUID)
if unmountCreateErr != nil {
klog.Errorf("error cleaning up mount %s after failure. Create unmounter failed with %v", b.volName, unmountCreateErr)
return
}
tearDownErr := unmounter.TearDown()
if tearDownErr != nil {
klog.Errorf("error tearing down volume %s with : %v", b.volName, tearDownErr)
}
}
}()
writerContext := fmt.Sprintf("pod %v/%v volume %v", b.pod.Namespace, b.pod.Name, b.volName)
writer, err := volumeutil.NewAtomicWriter(dir, writerContext)
if err != nil {
klog.Errorf("Error creating atomic writer: %v", err)
return err
}
setPerms := func(_ string) error {
// This may be the first time writing and new files get created outside the timestamp subdirectory:
// change the permissions on the whole volume and not only in the timestamp directory.
return volume.SetVolumeOwnership(b, mounterArgs.FsGroup, nil /*fsGroupChangePolicy*/, volumeutil.FSGroupCompleteHook(b.plugin, nil))
}
err = writer.Write(payload, setPerms)
if err != nil {
klog.Errorf("Error writing payload to dir: %v", err)
return err
}
setupSuccess = true
return nil
}
// MakePayload function is exported so that it can be called from the projection volume driver
func MakePayload(mappings []v1.KeyToPath, secret *v1.Secret, defaultMode *int32, optional bool) (map[string]volumeutil.FileProjection, error) {
if defaultMode == nil {
return nil, fmt.Errorf("no defaultMode used, not even the default value for it")
}
payload := make(map[string]volumeutil.FileProjection, len(secret.Data))
var fileProjection volumeutil.FileProjection
if len(mappings) == 0 {
for name, data := range secret.Data {
fileProjection.Data = []byte(data)
fileProjection.Mode = *defaultMode
payload[name] = fileProjection
}
} else {
for _, ktp := range mappings {
content, ok := secret.Data[ktp.Key]
if !ok {
if optional {
continue
}
errMsg := fmt.Sprintf("references non-existent secret key: %s", ktp.Key)
klog.Errorf(errMsg)
return nil, fmt.Errorf(errMsg)
}
fileProjection.Data = []byte(content)
if ktp.Mode != nil {
fileProjection.Mode = *ktp.Mode
} else {
fileProjection.Mode = *defaultMode
}
payload[ktp.Path] = fileProjection
}
}
return payload, nil
}
func totalSecretBytes(secret *v1.Secret) int {
totalSize := 0
for _, bytes := range secret.Data {
totalSize += len(bytes)
}
return totalSize
}
// secretVolumeUnmounter handles cleaning up secret volumes.
type secretVolumeUnmounter struct {
*secretVolume
}
var _ volume.Unmounter = &secretVolumeUnmounter{}
func (c *secretVolumeUnmounter) TearDown() error {
return c.TearDownAt(c.GetPath())
}
func (c *secretVolumeUnmounter) TearDownAt(dir string) error {
return volumeutil.UnmountViaEmptyDir(dir, c.plugin.host, c.volName, wrappedVolumeSpec(), c.podUID)
}
func getVolumeSource(spec *volume.Spec) (*v1.SecretVolumeSource, bool) {
var readOnly bool
var volumeSource *v1.SecretVolumeSource
if spec.Volume != nil && spec.Volume.Secret != nil {
volumeSource = spec.Volume.Secret
readOnly = spec.ReadOnly
}
return volumeSource, readOnly
}