add user management flow

app.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"os/user"
 	"path/filepath"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -51,6 +52,14 @@ type App struct {
 	writer     *bufio.Writer
 }
 
+type PasswdEntry struct {
+	Name  string
+	UID   int
+	GID   int
+	Home  string
+	Shell string
+}
+
 func NewApp(configPath string, users UserManager, runner CommandRunner, lookPath LookPathFunc) *App {
 	return &App{
 		configPath: configPath,
@@ -94,6 +103,7 @@ loaded:
 		a.println("[a] add share")
 		a.println("[e] edit share")
 		a.println("[d] delete share")
+		a.println("[u] manage users")
 		a.println("[w] write config and exit")
 		a.println("[q] quit without saving")
 		a.flush()
@@ -116,6 +126,10 @@ loaded:
 			if err := a.deleteShare(doc); err != nil {
 				return err
 			}
+		case "u", "users":
+			if err := a.manageUsers(doc); err != nil {
+				return err
+			}
 		case "w", "write":
 			return a.writeConfig(doc)
 		case "q", "quit":
@@ -126,6 +140,200 @@ loaded:
 	}
 }
 
+func (a *App) manageUsers(doc *Document) error {
+	for {
+		a.println("")
+		a.println("User management")
+		a.println("===============")
+		a.println("[c] check share accounts")
+		a.println("[p] change a Samba password")
+		a.println("[x] delete an unused account")
+		a.println("[b] back")
+		a.flush()
+
+		choice, err := a.prompt("Select an action")
+		if err != nil {
+			return err
+		}
+
+		switch strings.ToLower(choice) {
+		case "c", "check":
+			if err := a.checkShareAccounts(doc); err != nil {
+				return err
+			}
+		case "p", "password":
+			if err := a.changeSambaPassword(doc); err != nil {
+				return err
+			}
+		case "x", "delete":
+			if err := a.deleteUnusedAccount(doc); err != nil {
+				return err
+			}
+		case "b", "back":
+			return nil
+		default:
+			a.println("Unknown choice.")
+		}
+	}
+}
+
+func (a *App) checkShareAccounts(doc *Document) error {
+	references := shareUserReferences(doc)
+	if len(references) == 0 {
+		a.println("No accounts are listed in any share.")
+		return nil
+	}
+
+	a.println("")
+	a.println("Accounts used by the current shares:")
+	for _, ref := range references {
+		status := "missing"
+		if a.users.UserExists(ref.User) {
+			status = "present"
+		}
+		a.printf("  %s [%s] used by: %s\n", ref.User, status, strings.Join(ref.Shares, ", "))
+	}
+
+	var missing []string
+	for _, ref := range references {
+		if !a.users.UserExists(ref.User) {
+			missing = append(missing, ref.User)
+		}
+	}
+
+	if len(missing) == 0 {
+		a.println("")
+		a.println("All listed share accounts already exist.")
+		return nil
+	}
+
+	a.println("")
+	a.println("Some accounts are missing and those users may not be able to sign in.")
+	if err := a.ensureUsers(missing); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (a *App) deleteUnusedAccount(doc *Document) error {
+	entries, err := readPasswdEntries()
+	if err != nil {
+		return fmt.Errorf("read local users: %w", err)
+	}
+
+	candidates := unusedAccountCandidates(entries, shareUsers(doc))
+	if len(candidates) == 0 {
+		a.println("I couldn't find any obvious unused share accounts to delete.")
+		a.println("For safety, system accounts are excluded from this list.")
+		return nil
+	}
+
+	a.println("")
+	a.println("Accounts that look unused by the current shares:")
+	for i, entry := range candidates {
+		a.printf("  %d. %s (shell: %s)\n", i+1, entry.Name, entry.Shell)
+	}
+	a.println("Only accounts that are not listed in any share are shown here.")
+	a.flush()
+
+	raw, err := a.prompt("Account number to delete")
+	if err != nil {
+		return err
+	}
+
+	index, err := strconv.Atoi(raw)
+	if err != nil || index < 1 || index > len(candidates) {
+		a.println("Invalid selection.")
+		return nil
+	}
+
+	entry := candidates[index-1]
+	a.println("")
+	a.printf("This will remove the local account %q.\n", entry.Name)
+	a.println("This is only safe if nobody needs this account for Samba or anything else.")
+	a.flush()
+
+	confirm, err := a.confirm("Delete this account now", false)
+	if err != nil {
+		return err
+	}
+	if !confirm {
+		a.println("Delete cancelled.")
+		return nil
+	}
+
+	if err := a.deleteUser(entry.Name); err != nil {
+		return err
+	}
+
+	a.printf("Deleted account %s\n", entry.Name)
+	return nil
+}
+
+func (a *App) changeSambaPassword(doc *Document) error {
+	if a.lookPath != nil {
+		if _, err := a.lookPath("smbpasswd"); err != nil {
+			a.println("I couldn't find the smbpasswd tool yet.")
+			a.println("Install Samba first, then try this again.")
+			return nil
+		}
+	}
+
+	references := shareUserReferences(doc)
+	if len(references) == 0 {
+		a.println("No accounts are listed in any share.")
+		return nil
+	}
+
+	a.println("")
+	a.println("Accounts used by the current shares:")
+	for i, ref := range references {
+		status := "missing"
+		if a.users.UserExists(ref.User) {
+			status = "present"
+		}
+		a.printf("  %d. %s [%s] used by: %s\n", i+1, ref.User, status, strings.Join(ref.Shares, ", "))
+	}
+	a.flush()
+
+	raw, err := a.prompt("Account number to update")
+	if err != nil {
+		return err
+	}
+
+	index, err := strconv.Atoi(raw)
+	if err != nil || index < 1 || index > len(references) {
+		a.println("Invalid selection.")
+		return nil
+	}
+
+	ref := references[index-1]
+	if !a.users.UserExists(ref.User) {
+		a.println("")
+		a.printf("The local account %q does not exist yet.\n", ref.User)
+		a.println("I can create it first so a Samba password can be set.")
+		a.flush()
+
+		create, promptErr := a.confirm("Create this account now", true)
+		if promptErr != nil {
+			return promptErr
+		}
+		if !create {
+			return nil
+		}
+
+		if err := a.createUser(ref.User); err != nil {
+			return err
+		}
+	}
+
+	a.println("")
+	a.printf("I’ll open the password setup for %q now.\n", ref.User)
+	a.println("You’ll be asked to type the new Samba password.")
+	a.flush()
+	return a.setSambaPassword(ref.User)
+}
+
 func (a *App) handleMissingConfig() (*Document, error) {
 	a.println("")
 	a.println("Samba is not set up yet on this computer.")
@@ -516,6 +724,28 @@ func (a *App) setSambaPassword(name string) error {
 	}
 }
 
+func (a *App) deleteUser(name string) error {
+	if err := a.runPrivilegedOrLocal("userdel", []string{name}, "Deleting a Linux user needs administrator permission."); err != nil {
+		return fmt.Errorf("delete user %s: %w", name, err)
+	}
+
+	if a.lookPath != nil {
+		if _, err := a.lookPath("smbpasswd"); err == nil {
+			removeSamba, promptErr := a.confirm("Also remove the Samba password for this account", true)
+			if promptErr != nil {
+				return promptErr
+			}
+			if removeSamba {
+				if err := a.runPrivilegedOrLocal("smbpasswd", []string{"-x", name}, "Removing the Samba password needs administrator permission."); err != nil {
+					return fmt.Errorf("remove Samba password for %s: %w", name, err)
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
 func (a *App) prompt(label string) (string, error) {
 	a.printf("%s: ", label)
 	a.flush()
@@ -823,3 +1053,103 @@ func friendlyWriteError(action, path string, err error) error {
 	}
 	return fmt.Errorf("%s %s: %w", action, path, err)
 }
+
+type ShareUserReference struct {
+	User   string
+	Shares []string
+}
+
+func shareUsers(doc *Document) map[string]struct{} {
+	users := make(map[string]struct{})
+	for _, section := range doc.ShareSections() {
+		cfg := ShareFromSection(section)
+		for _, user := range cfg.ValidUsers {
+			users[user] = struct{}{}
+		}
+	}
+	return users
+}
+
+func shareUserReferences(doc *Document) []ShareUserReference {
+	refs := map[string][]string{}
+	for _, section := range doc.ShareSections() {
+		cfg := ShareFromSection(section)
+		for _, user := range cfg.ValidUsers {
+			refs[user] = append(refs[user], cfg.Name)
+		}
+	}
+
+	var out []ShareUserReference
+	for user, shares := range refs {
+		out = append(out, ShareUserReference{User: user, Shares: shares})
+	}
+	slices.SortFunc(out, func(a, b ShareUserReference) int {
+		return strings.Compare(a.User, b.User)
+	})
+	return out
+}
+
+func readPasswdEntries() ([]PasswdEntry, error) {
+	data, err := os.ReadFile("/etc/passwd")
+	if err != nil {
+		return nil, err
+	}
+
+	var entries []PasswdEntry
+	for _, line := range strings.Split(string(data), "\n") {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+
+		parts := strings.Split(line, ":")
+		if len(parts) < 7 {
+			continue
+		}
+
+		uid, err := strconv.Atoi(parts[2])
+		if err != nil {
+			continue
+		}
+		gid, err := strconv.Atoi(parts[3])
+		if err != nil {
+			continue
+		}
+
+		entries = append(entries, PasswdEntry{
+			Name:  parts[0],
+			UID:   uid,
+			GID:   gid,
+			Home:  parts[5],
+			Shell: parts[6],
+		})
+	}
+
+	return entries, nil
+}
+
+func unusedAccountCandidates(entries []PasswdEntry, active map[string]struct{}) []PasswdEntry {
+	var candidates []PasswdEntry
+	for _, entry := range entries {
+		if _, ok := active[entry.Name]; ok {
+			continue
+		}
+		if !looksLikeSafeShareAccount(entry) {
+			continue
+		}
+		candidates = append(candidates, entry)
+	}
+
+	slices.SortFunc(candidates, func(a, b PasswdEntry) int {
+		return strings.Compare(a.Name, b.Name)
+	})
+	return candidates
+}
+
+func looksLikeSafeShareAccount(entry PasswdEntry) bool {
+	if entry.UID < 1000 {
+		return false
+	}
+
+	shell := strings.TrimSpace(entry.Shell)
+	return strings.HasSuffix(shell, "/nologin") || strings.HasSuffix(shell, "/false")
+}