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access_credentials.go
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access_credentials.go
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/*
* This file is part of the KubeVirt project
*
* 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.
*
* Copyright 2020 Red Hat, Inc.
*
*/
package accesscredentials
import (
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"os"
"path/filepath"
"strings"
"sync"
"time"
"libvirt.org/go/libvirt"
"kubevirt.io/kubevirt/pkg/virt-launcher/metadata"
"github.com/fsnotify/fsnotify"
v1 "kubevirt.io/api/core/v1"
"kubevirt.io/client-go/log"
"kubevirt.io/kubevirt/pkg/config"
"kubevirt.io/kubevirt/pkg/virt-launcher/virtwrap/agent"
"kubevirt.io/kubevirt/pkg/virt-launcher/virtwrap/api"
"kubevirt.io/kubevirt/pkg/virt-launcher/virtwrap/cli"
"kubevirt.io/kubevirt/pkg/virt-launcher/virtwrap/util"
)
type openReturn struct {
Return int `json:"return"`
}
type readReturnData struct {
Count int `json:"count"`
BufB64 string `json:"buf-b64"`
}
type readReturn struct {
Return readReturnData `json:"return"`
}
type AccessCredentialManager struct {
virConn cli.Connection
// access credential propagation watchLock
watchLock sync.Mutex
secretWatcherStarted bool
stopCh chan struct{}
doneCh chan struct{}
resyncCheckIntervalSeconds int
watcher *fsnotify.Watcher
domainModifyLock *sync.Mutex
metadataCache *metadata.Cache
}
func NewManager(connection cli.Connection, domainModifyLock *sync.Mutex, metadataCache *metadata.Cache) *AccessCredentialManager {
return &AccessCredentialManager{
virConn: connection,
resyncCheckIntervalSeconds: 15,
domainModifyLock: domainModifyLock,
metadataCache: metadataCache,
}
}
// only set during unit tests
var unitTestSecretDir string
func getSecretDirs(vmi *v1.VirtualMachineInstance) []string {
var dirs []string
for _, accessCred := range vmi.Spec.AccessCredentials {
secretName := ""
if accessCred.SSHPublicKey != nil && accessCred.SSHPublicKey.PropagationMethod.QemuGuestAgent != nil {
if accessCred.SSHPublicKey.Source.Secret != nil {
secretName = accessCred.SSHPublicKey.Source.Secret.SecretName
}
} else if accessCred.UserPassword != nil && accessCred.UserPassword.PropagationMethod.QemuGuestAgent != nil {
if accessCred.UserPassword.Source.Secret != nil {
secretName = accessCred.UserPassword.Source.Secret.SecretName
}
}
if secretName == "" {
continue
}
dirs = append(dirs, getSecretDir(secretName))
}
return dirs
}
func getSecretDir(secretName string) string {
return filepath.Join(getSecretBaseDir(), secretName+"-access-cred")
}
func getSecretBaseDir() string {
if unitTestSecretDir != "" {
return unitTestSecretDir
}
return config.SecretSourceDir
}
func (l *AccessCredentialManager) writeGuestFile(contents string, domName string, filePath string, owner string, fileExists bool) error {
// ensure the directory exists with the correct permissions
err := l.agentCreateDirectory(domName, filepath.Dir(filePath), "700", owner)
if err != nil {
return err
}
if fileExists {
// ensure the file has the correct permissions for writing
l.agentSetFilePermissions(domName, filePath, "600", owner)
}
// write the file
base64Str := base64.StdEncoding.EncodeToString([]byte(contents))
cmdOpenFile := fmt.Sprintf(`{"execute": "guest-file-open", "arguments": { "path": "%s", "mode":"w" } }`, filePath)
output, err := l.virConn.QemuAgentCommand(cmdOpenFile, domName)
if err != nil {
return err
}
openRes := &openReturn{}
err = json.Unmarshal([]byte(output), openRes)
if err != nil {
return err
}
cmdWriteFile := fmt.Sprintf(`{"execute": "guest-file-write", "arguments": { "handle": %d, "buf-b64": "%s" } }`, openRes.Return, base64Str)
_, err = l.virConn.QemuAgentCommand(cmdWriteFile, domName)
if err != nil {
return err
}
cmdCloseFile := fmt.Sprintf(`{"execute": "guest-file-close", "arguments": { "handle": %d } }`, openRes.Return)
_, err = l.virConn.QemuAgentCommand(cmdCloseFile, domName)
if err != nil {
return err
}
if !fileExists {
// ensure the file has the correct permissions and ownership after creating new file
l.agentSetFilePermissions(domName, filePath, "600", owner)
}
return nil
}
func (l *AccessCredentialManager) readGuestFile(domName string, filePath string) (string, error) {
contents := ""
cmdOpenFile := fmt.Sprintf(`{"execute": "guest-file-open", "arguments": { "path": "%s", "mode":"r" } }`, filePath)
output, err := l.virConn.QemuAgentCommand(cmdOpenFile, domName)
if err != nil {
return contents, err
}
openRes := &openReturn{}
err = json.Unmarshal([]byte(output), openRes)
if err != nil {
return contents, err
}
cmdReadFile := fmt.Sprintf(`{"execute": "guest-file-read", "arguments": { "handle": %d } }`, openRes.Return)
readOutput, err := l.virConn.QemuAgentCommand(cmdReadFile, domName)
if err != nil {
return contents, err
}
readRes := &readReturn{}
err = json.Unmarshal([]byte(readOutput), readRes)
if err != nil {
return contents, err
}
if readRes.Return.Count > 0 {
readBytes, err := base64.StdEncoding.DecodeString(readRes.Return.BufB64)
if err != nil {
return contents, err
}
contents = string(readBytes)
}
cmdCloseFile := fmt.Sprintf(`{"execute": "guest-file-close", "arguments": { "handle": %d } }`, openRes.Return)
_, err = l.virConn.QemuAgentCommand(cmdCloseFile, domName)
if err != nil {
return contents, err
}
return contents, nil
}
func (l *AccessCredentialManager) agentGuestExec(domName string, command string, args []string) (string, error) {
return agent.GuestExec(l.virConn, domName, command, args, 10)
}
// Requires usage of mkdir, chown, chmod
func (l *AccessCredentialManager) agentCreateDirectory(domName string, dir string, permissions string, owner string) error {
// Ensure the directory exists
_, err := l.agentGuestExec(domName, "mkdir", []string{"-p", dir})
if err != nil {
return err
}
// set ownership/permissions of directory using parent directory owner
_, err = l.agentGuestExec(domName, "chown", []string{owner, dir})
if err != nil {
return err
}
_, err = l.agentGuestExec(domName, "chmod", []string{permissions, dir})
if err != nil {
return err
}
return nil
}
func (l *AccessCredentialManager) agentGetUserInfo(domName string, user string) (string, string, string, error) {
passwdEntryStr, err := l.agentGuestExec(domName, "getent", []string{"passwd", user})
if err != nil {
return "", "", "", fmt.Errorf("Unable to detect home directory of user %s: %s", user, err.Error())
}
passwdEntryStr = strings.TrimSpace(passwdEntryStr)
entries := strings.Split(passwdEntryStr, ":")
if len(entries) < 6 {
return "", "", "", fmt.Errorf("Unable to detect home directory of user %s", user)
}
filePath := entries[5]
uid := entries[2]
gid := entries[3]
log.Log.Infof("Detected home directory %s for user %s", filePath, user)
return filePath, uid, gid, nil
}
func (l *AccessCredentialManager) agentGetFileOwnership(domName string, filePath string) (string, error) {
ownerStr, err := l.agentGuestExec(domName, "stat", []string{"-c", "%U:%G", filePath})
if err != nil {
return "", fmt.Errorf("Unable to detect ownership of access credential at %s: %s", filePath, err.Error())
}
ownerStr = strings.TrimSpace(ownerStr)
if ownerStr == "" {
return "", fmt.Errorf("Unable to detect ownership of access credential at %s", filePath)
}
log.Log.Infof("Detected owner %s for quest path %s", ownerStr, filePath)
return ownerStr, nil
}
// Requires usage of chown, chmod
func (l *AccessCredentialManager) agentSetFilePermissions(domName string, filePath string, permissions string, owner string) error {
// set ownership/permissions of directory using parent directory owner
_, err := l.agentGuestExec(domName, "chown", []string{owner, filePath})
if err != nil {
return err
}
_, err = l.agentGuestExec(domName, "chmod", []string{permissions, filePath})
if err != nil {
return err
}
return nil
}
func (l *AccessCredentialManager) agentSetUserPassword(domName string, user string, password string) error {
base64Str := base64.StdEncoding.EncodeToString([]byte(password))
cmdSetPassword := fmt.Sprintf(`{"execute":"guest-set-user-password", "arguments": {"username":"%s", "password": "%s", "crypted": false }}`, user, base64Str)
_, err := l.virConn.QemuAgentCommand(cmdSetPassword, domName)
if err != nil {
return err
}
return nil
}
func (l *AccessCredentialManager) pingAgent(domName string) error {
cmdPing := `{"execute":"guest-ping"}`
_, err := l.virConn.QemuAgentCommand(cmdPing, domName)
return err
}
func (l *AccessCredentialManager) agentSetAuthorizedKeys(domName string, user string, authorizedKeys []string) error {
err := func() error {
domain, err := l.virConn.LookupDomainByName(domName)
if err != nil {
return err
}
defer domain.Free()
// Zero flags argument means that the authorized_keys file is overwritten with the authorizedKeys
return domain.AuthorizedSSHKeysSet(user, authorizedKeys, 0)
}()
if errors.Is(err, libvirt.ERR_NO_SUPPORT) {
// If AuthorizedSSHKeysSet method is not supported, use the old method
desiredAuthorizedKeys := strings.Join(authorizedKeys, "\n")
return l.agentWriteAuthorizedKeysFile(domName, user, desiredAuthorizedKeys)
}
return err
}
func (l *AccessCredentialManager) agentWriteAuthorizedKeysFile(domName string, user string, desiredAuthorizedKeys string) (err error) {
curAuthorizedKeys := ""
fileExists := true
// ######
// Step 1. Get home directory for user.
// ######
homeDir, uid, gid, err := l.agentGetUserInfo(domName, user)
if err != nil {
return err
}
// ######
// Step 2. Read file on guest to determine if change is required
// ######
filePath := fmt.Sprintf("%s/.ssh/authorized_keys", homeDir)
curAuthorizedKeys, err = l.readGuestFile(domName, filePath)
if err != nil && strings.Contains(err.Error(), "No such file or directory") {
fileExists = false
} else if err != nil {
return err
}
// ######
// Step 3. Write authorized_keys file if changes exist
// ######
// only update if the updated string is not equal to the current contents on the guest.
if curAuthorizedKeys != desiredAuthorizedKeys {
err = l.writeGuestFile(desiredAuthorizedKeys, domName, filePath, fmt.Sprintf("%s:%s", uid, gid), fileExists)
if err != nil {
return err
}
}
return nil
}
func isSSHPublicKey(accessCred *v1.AccessCredential) bool {
if accessCred.SSHPublicKey != nil && accessCred.SSHPublicKey.PropagationMethod.QemuGuestAgent != nil {
return true
}
return false
}
func isUserPassword(accessCred *v1.AccessCredential) bool {
if accessCred.UserPassword != nil && accessCred.UserPassword.PropagationMethod.QemuGuestAgent != nil {
return true
}
return false
}
func getSecret(accessCred *v1.AccessCredential) string {
secretName := ""
if accessCred.SSHPublicKey != nil && accessCred.SSHPublicKey.PropagationMethod.QemuGuestAgent != nil {
if accessCred.SSHPublicKey.Source.Secret != nil {
secretName = accessCred.SSHPublicKey.Source.Secret.SecretName
}
} else if accessCred.UserPassword != nil && accessCred.UserPassword.PropagationMethod.QemuGuestAgent != nil {
if accessCred.UserPassword.Source.Secret != nil {
secretName = accessCred.UserPassword.Source.Secret.SecretName
}
}
return secretName
}
func (l *AccessCredentialManager) reportAccessCredentialResult(succeeded bool, message string) {
acMetadata := api.AccessCredentialMetadata{
Succeeded: succeeded,
Message: message,
}
l.metadataCache.AccessCredential.Store(acMetadata)
log.Log.V(4).Infof("Access credential set in metadata: %v", acMetadata)
return
}
func (l *AccessCredentialManager) watchSecrets(vmi *v1.VirtualMachineInstance) {
logger := log.Log.Object(vmi)
reload := true
fileChangeDetected := true
domName := util.VMINamespaceKeyFunc(vmi)
// guest agent will force a resync of changes every 'x' minutes
forceResyncTicker := time.NewTicker(5 * time.Minute)
defer forceResyncTicker.Stop()
// guest agent will aggregate all changes to secrets and apply them
// every 'x' seconds. This could help prevent making multiple qemu
// execution calls in the event multiple secret changes are landing within
// a small timeframe.
handleChangesTicker := time.NewTicker(time.Duration(l.resyncCheckIntervalSeconds) * time.Second)
defer handleChangesTicker.Stop()
for {
select {
case <-l.watcher.Events:
fileChangeDetected = true
case err := <-l.watcher.Errors:
logger.Reason(err).Errorf("Error encountered while watching downward api secret")
case <-forceResyncTicker.C:
reload = true
logger.Info("Resyncing access credentials due to recurring resync period")
case <-handleChangesTicker.C:
if fileChangeDetected {
reload = true
logger.Info("Reloading access credentials because secret changed")
}
case <-l.stopCh:
logger.Info("Signalled to stop watching access credential secrets")
return
}
if !reload {
continue
}
fileChangeDetected = false
reload = false
reportedErr := false
err := l.pingAgent(domName)
if err != nil {
reload = true
reportedErr = true
l.reportAccessCredentialResult(false, "Guest agent is offline")
continue
}
credentialInfo := newAccessCredentialsInfo()
// Step 1. Populate access credential info
for i := range vmi.Spec.AccessCredentials {
err := credentialInfo.addAccessCredential(&vmi.Spec.AccessCredentials[i])
if err != nil {
// if reading failed, reset reload to true so this change will be retried again
reload = true
reportedErr = true
logger.Reason(err).Errorf("Error encountered")
l.reportAccessCredentialResult(false, err.Error())
}
}
// Step 2. Update Authorized keys
for user, secretNames := range credentialInfo.userSSHMap {
var allAuthorizedKeys []string
for _, secretName := range secretNames {
pubKeys := credentialInfo.secretMap[secretName]
allAuthorizedKeys = append(allAuthorizedKeys, pubKeys...)
}
err := l.agentSetAuthorizedKeys(domName, user, allAuthorizedKeys)
if err != nil {
// if writing failed, reset reload to true so this change will be retried again
reload = true
reportedErr = true
logger.Reason(err).Errorf("Error encountered writing access credentials using guest agent")
l.reportAccessCredentialResult(false, fmt.Sprintf("Error encountered writing ssh pub key access credentials for user [%s]: %v", user, err))
continue
}
}
// Step 3. update UserPasswords
for user, password := range credentialInfo.userPasswordMap {
err := l.agentSetUserPassword(domName, user, password)
if err != nil {
// if setting password failed, reset reload to true so this will be tried again
reload = true
reportedErr = true
logger.Reason(err).Errorf("Error encountered setting password for user [%s]", user)
l.reportAccessCredentialResult(false, fmt.Sprintf("Error encountered setting password for user [%s]: %v", user, err))
continue
}
}
if !reportedErr {
l.reportAccessCredentialResult(true, "")
}
}
}
func (l *AccessCredentialManager) HandleQemuAgentAccessCredentials(vmi *v1.VirtualMachineInstance) error {
l.watchLock.Lock()
defer l.watchLock.Unlock()
if l.secretWatcherStarted {
// already started
return nil
}
secretDirs := getSecretDirs(vmi)
if len(secretDirs) == 0 {
// nothing to watch
return nil
}
var err error
l.watcher, err = fsnotify.NewWatcher()
if err != nil {
return err
}
for _, dir := range secretDirs {
err = l.watcher.Add(dir)
if err != nil {
// Ignoring error returned by watcher.Close(),
// because another error will be returned.
_ = l.watcher.Close()
return err
}
}
l.stopCh = make(chan struct{})
l.doneCh = make(chan struct{})
go func() {
defer close(l.doneCh)
// Ignoring the error, because the watch has stopped.
defer func() { _ = l.watcher.Close() }()
l.watchSecrets(vmi)
}()
l.secretWatcherStarted = true
return nil
}
func (l *AccessCredentialManager) Stop() {
l.watchLock.Lock()
defer l.watchLock.Unlock()
if !l.secretWatcherStarted {
return
}
close(l.stopCh)
<-l.doneCh
l.secretWatcherStarted = false
}
type accessCredentialsInfo struct {
// secret name mapped to authorized_keys in that secret
secretMap map[string][]string
// filepath mapped to secretNames
userSSHMap map[string][]string
// maps users to passwords
userPasswordMap map[string]string
}
func (a *accessCredentialsInfo) addAccessCredential(accessCred *v1.AccessCredential) error {
secretName := getSecret(accessCred)
if secretName == "" {
return nil
}
secretDir := getSecretDir(secretName)
files, err := os.ReadDir(secretDir)
if err != nil {
return fmt.Errorf("error occurred while reading the list of secrets files from the base directory %s: %w", secretDir, err)
}
if isSSHPublicKey(accessCred) {
for _, user := range accessCred.SSHPublicKey.PropagationMethod.QemuGuestAgent.Users {
a.userSSHMap[user] = append(a.userSSHMap[user], secretName)
}
var authorizedKeys []string
for _, file := range files {
if file.IsDir() || strings.HasPrefix(file.Name(), "..") {
continue
}
pubKeyBytes, err := os.ReadFile(filepath.Join(secretDir, file.Name()))
if err != nil {
return fmt.Errorf("error occurred while reading the access credential secret file [%s]: %w", filepath.Join(secretDir, file.Name()), err)
}
for _, pubKey := range strings.Split(string(pubKeyBytes), "\n") {
trimmedKey := strings.TrimSpace(pubKey)
if trimmedKey != "" {
authorizedKeys = append(authorizedKeys, trimmedKey)
}
}
}
if len(authorizedKeys) > 0 {
a.secretMap[secretName] = authorizedKeys
}
} else if isUserPassword(accessCred) {
for _, file := range files {
// Mounted secret directory contains directories prefixed by "..".
// They are used by k8s to atomically swap all files when the secret is updated.
if file.IsDir() || strings.HasPrefix(file.Name(), "..") {
continue
}
passwordBytes, err := os.ReadFile(filepath.Join(secretDir, file.Name()))
if err != nil {
return fmt.Errorf("error occurred while reading the access credential secret file [%s]: %w", filepath.Join(secretDir, file.Name()), err)
}
password := strings.TrimSpace(string(passwordBytes))
if password == "" {
continue
}
a.userPasswordMap[file.Name()] = password
}
}
return nil
}
func newAccessCredentialsInfo() *accessCredentialsInfo {
return &accessCredentialsInfo{
secretMap: make(map[string][]string),
userSSHMap: make(map[string][]string),
userPasswordMap: make(map[string]string),
}
}