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group_monitor.go
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/
group_monitor.go
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package norduser
import (
"fmt"
"log"
"os/user"
"regexp"
"strconv"
"strings"
"github.com/NordSecurity/nordvpn-linux/internal"
"github.com/NordSecurity/nordvpn-linux/norduser/service"
"github.com/NordSecurity/nordvpn-linux/snapconf"
"github.com/fsnotify/fsnotify"
)
const (
groupfilePath = "/etc/group"
)
type userSet map[string]bool
func findGroupEntry(groups string, groupName string) string {
r, _ := regexp.Compile(fmt.Sprintf("^%s:", groupName))
for _, groupEntry := range strings.Split(groups, "\n") {
if r.MatchString(groupEntry) {
return groupEntry
}
}
return ""
}
func getGroupEntry(groupName string) (string, error) {
file, err := internal.FileRead(groupfilePath)
if err != nil {
return "", fmt.Errorf("failed to read group file: %w", err)
}
groupEntry := findGroupEntry(string(file), groupName)
if groupEntry == "" {
return "", fmt.Errorf("group entry not found: %w", err)
}
return groupEntry, nil
}
func getGroupMembers(groupEntry string) userSet {
groupEntry = strings.TrimSuffix(groupEntry, "\n")
sepIndex := strings.LastIndex(groupEntry, ":")
groupMembers := groupEntry[sepIndex+1:]
members := make(userSet)
if groupMembers == "" {
return members
}
for _, member := range strings.Split(groupMembers, ",") {
members[member] = false
}
return members
}
func getNordvpnGroupMembers() (userSet, error) {
const nordvpnGroupName = "nordvpn"
groupEntry, err := getGroupEntry(nordvpnGroupName)
if err != nil {
return nil, fmt.Errorf("getting group entry: %w", err)
}
groupMembers := getGroupMembers(groupEntry)
return groupMembers, nil
}
type userIDs struct {
uid uint32
gid uint32
home string
}
func getUID(username string) (userIDs, error) {
user, err := user.Lookup(username)
if err != nil {
return userIDs{}, fmt.Errorf("looking up user: %w", err)
}
uid, err := strconv.Atoi(user.Uid)
if err != nil {
return userIDs{}, fmt.Errorf("converting uid string to int: %w", err)
}
gid, err := strconv.Atoi(user.Gid)
if err != nil {
return userIDs{}, fmt.Errorf("converting uid string to int: %w", err)
}
return userIDs{
uid: uint32(uid),
gid: uint32(gid),
home: user.HomeDir,
}, nil
}
func (n *NordvpnGroupMonitor) handleGroupUpdate(currentGroupMembers userSet, newGroupMembers userSet) {
for member := range currentGroupMembers {
// member not modified, do nothing
if _, ok := newGroupMembers[member]; ok {
newGroupMembers[member] = true
continue
}
userIDs, err := getUID(member)
if err != nil {
log.Println("failed to look up UID/GID of deleted group member: ", err)
continue
}
if err := n.norduserd.Stop(userIDs.uid); err != nil {
log.Println("disabling norduserd for user:", err.Error())
}
}
if n.isSnap {
// in snap environment norduser is enabled on the cli side
return
}
// enable norduserd for new members
for member, norduserdEnabled := range newGroupMembers {
if norduserdEnabled {
continue
}
userID, err := getUID(member)
if err != nil {
log.Println("failed to lookup UID/GID for new group member:", err)
continue
}
if err := n.norduserd.Enable(userID.uid, userID.gid, userID.home); err != nil {
log.Println("enabling norduserd for member:", err)
}
newGroupMembers[member] = true
}
}
func (n *NordvpnGroupMonitor) startForEveryGroupMember(groupMembers userSet) {
for member := range groupMembers {
user, err := getUID(member)
if err != nil {
log.Println("failed to get UID/GID for group member:", err)
continue
}
if err := n.norduserd.Enable(user.uid, user.gid, user.home); err != nil {
log.Println("failed to start norduser for group member:", err)
}
groupMembers[member] = true
}
}
// NordvpnGroupMonitor monitors the nordvpn system group and starts/stops norduserd for users added/removed from the
// group.
type NordvpnGroupMonitor struct {
norduserd service.NorduserService
isSnap bool
}
func NewNordvpnGroupMonitor(service service.NorduserService) NordvpnGroupMonitor {
return NordvpnGroupMonitor{
norduserd: service,
isSnap: snapconf.IsUnderSnap(),
}
}
// Start blocks the thread and starts monitoring for changes in the nordvpn group.
func (n *NordvpnGroupMonitor) Start() error {
const etcPath = "/etc"
watcher, err := fsnotify.NewWatcher()
if err != nil {
return fmt.Errorf("creating new watcher: %w", err)
}
if err := watcher.Add(etcPath); err != nil {
return fmt.Errorf("adding file to watcher: %w", err)
}
currentGrupMembers, err := getNordvpnGroupMembers()
if err != nil {
return fmt.Errorf("getting initial group members: %w", err)
} else if !n.isSnap { // in snap environment norduser is enabled on the cli side
n.startForEveryGroupMember(currentGrupMembers)
}
defer watcher.Close()
for {
select {
case event, ok := <-watcher.Events:
if !ok {
return fmt.Errorf("groupfile monitor channel closed")
}
// Because utilities used to modify the group do so atomically, we also need to monitor for creation of
// the file instead of modifications.
if (event.Has(fsnotify.Create) || event.Has(fsnotify.Write)) && event.Name == groupfilePath {
newGroupMembers, err := getNordvpnGroupMembers()
if err == nil {
n.handleGroupUpdate(currentGrupMembers, newGroupMembers)
currentGrupMembers = newGroupMembers
} else {
log.Println("Failed to get new group members:", err)
}
}
case err, ok := <-watcher.Errors:
if !ok {
return fmt.Errorf("groupfile monitor error channel closed")
}
log.Println(internal.ErrorPrefix, "group monitor error:", err)
}
}
}