feat(Auth): Unify shared PAM sync across greeter & lockscreen

- Add a neutral `dms auth sync` command and reuse the shared auth flow from:
- Settings auth toggle auto-apply
- `dms greeter sync`
- `dms greeter install`
- greeter auth cleanup paths

- Rework lockscreen PAM so DMS builds /etc/pam.d/dankshell from the system login stack, but removes fingerprint and U2F from that password path. Keep /etc/pam.d/dankshell-u2f separate.

- Preserve custom PAM files in place to avoid adding duplicate greeter auth when the distro already provides it, and keep NixOS on the non-writing path.

core/cmd/dms/commands_auth.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
+	sharedpam "github.com/AvengeMedia/DankMaterialShell/core/internal/pam"
+	"github.com/spf13/cobra"
+)
+
+var authCmd = &cobra.Command{
+	Use:   "auth",
+	Short: "Manage DMS authentication sync",
+	Long:  "Manage shared PAM/authentication setup for DMS greeter and lock screen",
+}
+
+var authSyncCmd = &cobra.Command{
+	Use:   "sync",
+	Short: "Sync DMS authentication configuration",
+	Long:  "Apply shared PAM/authentication changes for the lock screen and greeter based on current DMS settings",
+	Run: func(cmd *cobra.Command, args []string) {
+		yes, _ := cmd.Flags().GetBool("yes")
+		term, _ := cmd.Flags().GetBool("terminal")
+		if term {
+			if err := syncAuthInTerminal(yes); err != nil {
+				log.Fatalf("Error launching auth sync in terminal: %v", err)
+			}
+			return
+		}
+		if err := syncAuth(yes); err != nil {
+			log.Fatalf("Error syncing authentication: %v", err)
+		}
+	},
+}
+
+func init() {
+	authSyncCmd.Flags().BoolP("yes", "y", false, "Non-interactive mode: skip prompts")
+	authSyncCmd.Flags().BoolP("terminal", "t", false, "Run auth sync in a new terminal (for entering sudo password)")
+}
+
+func syncAuth(nonInteractive bool) error {
+	if !nonInteractive {
+		fmt.Println("=== DMS Authentication Sync ===")
+		fmt.Println()
+	}
+
+	logFunc := func(msg string) {
+		fmt.Println(msg)
+	}
+
+	if err := sharedpam.SyncAuthConfig(logFunc, "", sharedpam.SyncAuthOptions{}); err != nil {
+		return err
+	}
+
+	if !nonInteractive {
+		fmt.Println("\n=== Authentication Sync Complete ===")
+		fmt.Println("\nAuthentication changes have been applied.")
+	}
+
+	return nil
+}
+
+func syncAuthInTerminal(nonInteractive bool) error {
+	syncFlags := make([]string, 0, 1)
+	if nonInteractive {
+		syncFlags = append(syncFlags, "--yes")
+	}
+
+	shellSyncCmd := "dms auth sync"
+	if len(syncFlags) > 0 {
+		shellSyncCmd += " " + strings.Join(syncFlags, " ")
+	}
+	shellCmd := shellSyncCmd + `; echo; echo "Authentication sync finished. Closing in 3 seconds..."; sleep 3`
+	return runCommandInTerminal(shellCmd)
+}

core/cmd/dms/commands_greeter.go

@@ -13,6 +13,7 @@ import (
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/distros"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/greeter"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
+	sharedpam "github.com/AvengeMedia/DankMaterialShell/core/internal/pam"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/utils"
 	"github.com/spf13/cobra"
 	"golang.org/x/text/cases"
@@ -25,6 +26,11 @@ var greeterCmd = &cobra.Command{
 	Long:  "Manage DMS greeter (greetd)",
 }
 
+var (
+	greeterConfigSyncFn = greeter.SyncDMSConfigs
+	sharedAuthSyncFn    = sharedpam.SyncAuthConfig
+)
+
 var greeterInstallCmd = &cobra.Command{
 	Use:     "install",
 	Short:   "Install and configure DMS greeter",
@@ -148,6 +154,16 @@ func init() {
 	greeterUninstallCmd.Flags().BoolP("terminal", "t", false, "Run in a new terminal (for entering sudo password)")
 }
 
+func syncGreeterConfigsAndAuth(dmsPath, compositor string, logFunc func(string), options sharedpam.SyncAuthOptions, beforeAuth func()) error {
+	if err := greeterConfigSyncFn(dmsPath, compositor, logFunc, ""); err != nil {
+		return err
+	}
+	if beforeAuth != nil {
+		beforeAuth()
+	}
+	return sharedAuthSyncFn(logFunc, "", options)
+}
+
 func installGreeter(nonInteractive bool) error {
 	fmt.Println("=== DMS Greeter Installation ===")
 
@@ -243,7 +259,9 @@ func installGreeter(nonInteractive bool) error {
 	}
 
 	fmt.Println("\nSynchronizing DMS configurations...")
-	if err := greeter.SyncDMSConfigs(dmsPath, selectedCompositor, logFunc, "", false); err != nil {
+	if err := syncGreeterConfigsAndAuth(dmsPath, selectedCompositor, logFunc, sharedpam.SyncAuthOptions{}, func() {
+		fmt.Println("\nConfiguring authentication...")
+	}); err != nil {
 		return err
 	}
 
@@ -278,7 +296,7 @@ func uninstallGreeter(nonInteractive bool) error {
 	}
 
 	if !nonInteractive {
-		fmt.Print("\nThis will:\n  • Stop and disable greetd\n  • Remove the DMS PAM managed block\n  • Remove the DMS AppArmor profile\n  • Restore the most recent pre-DMS greetd config (if available)\n\nContinue? [y/N]: ")
+		fmt.Print("\nThis will:\n  • Stop and disable greetd\n  • Remove the DMS-managed greeter auth block\n  • Remove the DMS AppArmor profile\n  • Restore the most recent pre-DMS greetd config (if available)\n\nContinue? [y/N]: ")
 		var response string
 		fmt.Scanln(&response)
 		if strings.ToLower(strings.TrimSpace(response)) != "y" {
@@ -297,8 +315,8 @@ func uninstallGreeter(nonInteractive bool) error {
 		fmt.Println("  ✓ greetd disabled")
 	}
 
-	fmt.Println("\nRemoving DMS PAM configuration...")
+	fmt.Println("\nRemoving DMS authentication configuration...")
-	if err := greeter.RemoveGreeterPamManagedBlock(logFunc, ""); err != nil {
+	if err := sharedpam.RemoveManagedGreeterPamBlock(logFunc, ""); err != nil {
 		fmt.Printf("  ⚠ PAM cleanup failed: %v\n", err)
 	}
 
@@ -535,7 +553,7 @@ func resolveLocalWrapperShell() (string, error) {
 
 func syncGreeter(nonInteractive bool, forceAuth bool, local bool) error {
 	if !nonInteractive {
-		fmt.Println("=== DMS Greeter Theme Sync ===")
+		fmt.Println("=== DMS Greeter Sync ===")
 		fmt.Println()
 	}
 
@@ -721,7 +739,11 @@ func syncGreeter(nonInteractive bool, forceAuth bool, local bool) error {
 	}
 
 	fmt.Println("\nSynchronizing DMS configurations...")
-	if err := greeter.SyncDMSConfigs(dmsPath, compositor, logFunc, "", forceAuth); err != nil {
+	if err := syncGreeterConfigsAndAuth(dmsPath, compositor, logFunc, sharedpam.SyncAuthOptions{
+		ForceGreeterAuth: forceAuth,
+	}, func() {
+		fmt.Println("\nConfiguring authentication...")
+	}); err != nil {
 		return err
 	}
 
@@ -734,8 +756,9 @@ func syncGreeter(nonInteractive bool, forceAuth bool, local bool) error {
 
 	fmt.Println("\n=== Sync Complete ===")
 	fmt.Println("\nYour theme, settings, and wallpaper configuration have been synced with the greeter.")
+	fmt.Println("Shared authentication settings were also checked and reconciled where needed.")
 	if forceAuth {
-		fmt.Println("PAM has been configured for fingerprint and U2F (where modules exist).")
+		fmt.Println("Authentication has been configured for fingerprint and U2F (where modules exist).")
 	}
 	fmt.Println("The changes will be visible on the next login screen.")
 
@@ -1297,39 +1320,7 @@ func extractGreeterPathOverrideFromCommand(command string) string {
 }
 
 func parseManagedGreeterPamAuth(pamText string) (managed bool, fingerprint bool, u2f bool, legacy bool) {
-	if pamText == "" {
+	return sharedpam.ParseManagedGreeterPamAuth(pamText)
-		return false, false, false, false
-	}
-
-	lines := strings.Split(pamText, "\n")
-	inManaged := false
-	for _, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		switch trimmed {
-		case greeter.GreeterPamManagedBlockStart:
-			managed = true
-			inManaged = true
-			continue
-		case greeter.GreeterPamManagedBlockEnd:
-			inManaged = false
-			continue
-		}
-
-		if strings.HasPrefix(trimmed, "# DMS greeter fingerprint") || strings.HasPrefix(trimmed, "# DMS greeter U2F") {
-			legacy = true
-		}
-		if !inManaged {
-			continue
-		}
-		if strings.Contains(trimmed, "pam_fprintd") {
-			fingerprint = true
-		}
-		if strings.Contains(trimmed, "pam_u2f") {
-			u2f = true
-		}
-	}
-
-	return managed, fingerprint, u2f, legacy
 }
 
 func packageInstallHint() string {
@@ -1639,29 +1630,29 @@ func checkGreeterStatus() error {
 			fmt.Println("  ℹ No managed auth block present (DMS-managed fingerprint/U2F lines are disabled)")
 		}
 		if legacyManaged {
-			fmt.Println("  ⚠ Legacy unmanaged DMS PAM lines detected. Run 'dms greeter sync' to normalize.")
+			fmt.Println("  ⚠ Legacy unmanaged DMS PAM lines detected. Run 'dms auth sync' to normalize.")
 			allGood = false
 		}
 		enableFprintToggle, enableU2fToggle := false, false
-		if enableFprint, enableU2f, settingsErr := greeter.ReadGreeterAuthToggles(homeDir); settingsErr == nil {
+		if enableFprint, enableU2f, settingsErr := sharedpam.ReadGreeterAuthToggles(homeDir); settingsErr == nil {
 			enableFprintToggle = enableFprint
 			enableU2fToggle = enableU2f
 		} else {
 			fmt.Printf("  ℹ Could not read greeter auth toggles from settings: %v\n", settingsErr)
 		}
 
-		includedFprintFile := greeter.DetectIncludedPamModule(string(pamData), "pam_fprintd.so")
+		includedFprintFile := sharedpam.DetectIncludedPamModule(string(pamData), "pam_fprintd.so")
-		includedU2fFile := greeter.DetectIncludedPamModule(string(pamData), "pam_u2f.so")
+		includedU2fFile := sharedpam.DetectIncludedPamModule(string(pamData), "pam_u2f.so")
-		fprintAvailableForCurrentUser := greeter.FingerprintAuthAvailableForCurrentUser()
+		fprintAvailableForCurrentUser := sharedpam.FingerprintAuthAvailableForCurrentUser()
 
 		if managedFprint && includedFprintFile != "" {
 			fmt.Printf("  ⚠ pam_fprintd found in both DMS managed block and %s.\n", includedFprintFile)
-			fmt.Println("    Double fingerprint auth detected — run 'dms greeter sync' to resolve.")
+			fmt.Println("    Double fingerprint auth detected — run 'dms auth sync' to resolve.")
 			allGood = false
 		}
 		if managedU2f && includedU2fFile != "" {
 			fmt.Printf("  ⚠ pam_u2f found in both DMS managed block and %s.\n", includedU2fFile)
-			fmt.Println("    Double security-key auth detected — run 'dms greeter sync' to resolve.")
+			fmt.Println("    Double security-key auth detected — run 'dms auth sync' to resolve.")
 			allGood = false
 		}
 

core/cmd/dms/commands_greeter_test.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"errors"
+	"reflect"
+	"testing"
+
+	sharedpam "github.com/AvengeMedia/DankMaterialShell/core/internal/pam"
+)
+
+func TestSyncGreeterConfigsAndAuthDelegatesSharedAuth(t *testing.T) {
+	origGreeterConfigSyncFn := greeterConfigSyncFn
+	origSharedAuthSyncFn := sharedAuthSyncFn
+	t.Cleanup(func() {
+		greeterConfigSyncFn = origGreeterConfigSyncFn
+		sharedAuthSyncFn = origSharedAuthSyncFn
+	})
+
+	var calls []string
+	greeterConfigSyncFn = func(dmsPath, compositor string, logFunc func(string), sudoPassword string) error {
+		if dmsPath != "/tmp/dms" {
+			t.Fatalf("unexpected dmsPath %q", dmsPath)
+		}
+		if compositor != "niri" {
+			t.Fatalf("unexpected compositor %q", compositor)
+		}
+		if sudoPassword != "" {
+			t.Fatalf("expected empty sudoPassword, got %q", sudoPassword)
+		}
+		calls = append(calls, "configs")
+		return nil
+	}
+
+	var gotOptions sharedpam.SyncAuthOptions
+	sharedAuthSyncFn = func(logFunc func(string), sudoPassword string, options sharedpam.SyncAuthOptions) error {
+		if sudoPassword != "" {
+			t.Fatalf("expected empty sudoPassword, got %q", sudoPassword)
+		}
+		gotOptions = options
+		calls = append(calls, "auth")
+		return nil
+	}
+
+	err := syncGreeterConfigsAndAuth("/tmp/dms", "niri", func(string) {}, sharedpam.SyncAuthOptions{
+		ForceGreeterAuth: true,
+	}, func() {
+		calls = append(calls, "before-auth")
+	})
+	if err != nil {
+		t.Fatalf("syncGreeterConfigsAndAuth returned error: %v", err)
+	}
+
+	wantCalls := []string{"configs", "before-auth", "auth"}
+	if !reflect.DeepEqual(calls, wantCalls) {
+		t.Fatalf("call order = %v, want %v", calls, wantCalls)
+	}
+	if !gotOptions.ForceGreeterAuth {
+		t.Fatalf("expected ForceGreeterAuth to be true, got %+v", gotOptions)
+	}
+}
+
+func TestSyncGreeterConfigsAndAuthStopsOnConfigError(t *testing.T) {
+	origGreeterConfigSyncFn := greeterConfigSyncFn
+	origSharedAuthSyncFn := sharedAuthSyncFn
+	t.Cleanup(func() {
+		greeterConfigSyncFn = origGreeterConfigSyncFn
+		sharedAuthSyncFn = origSharedAuthSyncFn
+	})
+
+	greeterConfigSyncFn = func(string, string, func(string), string) error {
+		return errors.New("config sync failed")
+	}
+
+	authCalled := false
+	sharedAuthSyncFn = func(func(string), string, sharedpam.SyncAuthOptions) error {
+		authCalled = true
+		return nil
+	}
+
+	err := syncGreeterConfigsAndAuth("/tmp/dms", "niri", func(string) {}, sharedpam.SyncAuthOptions{}, nil)
+	if err == nil || err.Error() != "config sync failed" {
+		t.Fatalf("expected config sync error, got %v", err)
+	}
+	if authCalled {
+		t.Fatal("expected auth sync not to run after config sync failure")
+	}
+}

core/cmd/dms/main.go

@@ -17,11 +17,13 @@ func init() {
 	runCmd.Flags().MarkHidden("daemon-child")
 
 	greeterCmd.AddCommand(greeterInstallCmd, greeterSyncCmd, greeterEnableCmd, greeterStatusCmd, greeterUninstallCmd)
+	authCmd.AddCommand(authSyncCmd)
 	setupCmd.AddCommand(setupBindsCmd, setupLayoutCmd, setupColorsCmd, setupAlttabCmd, setupOutputsCmd, setupCursorCmd, setupWindowrulesCmd)
 	updateCmd.AddCommand(updateCheckCmd)
 	pluginsCmd.AddCommand(pluginsBrowseCmd, pluginsListCmd, pluginsInstallCmd, pluginsUninstallCmd, pluginsUpdateCmd)
 	rootCmd.AddCommand(getCommonCommands()...)
 
+	rootCmd.AddCommand(authCmd)
 	rootCmd.AddCommand(updateCmd)
 
 	rootCmd.SetHelpTemplate(getHelpTemplate())

core/cmd/dms/main_distro.go

@@ -17,9 +17,11 @@ func init() {
 	runCmd.Flags().MarkHidden("daemon-child")
 
 	greeterCmd.AddCommand(greeterInstallCmd, greeterSyncCmd, greeterEnableCmd, greeterStatusCmd, greeterUninstallCmd)
+	authCmd.AddCommand(authSyncCmd)
 	setupCmd.AddCommand(setupBindsCmd, setupLayoutCmd, setupColorsCmd, setupAlttabCmd, setupOutputsCmd, setupCursorCmd, setupWindowrulesCmd)
 	pluginsCmd.AddCommand(pluginsBrowseCmd, pluginsListCmd, pluginsInstallCmd, pluginsUninstallCmd, pluginsUpdateCmd)
 	rootCmd.AddCommand(getCommonCommands()...)
+	rootCmd.AddCommand(authCmd)
 
 	rootCmd.SetHelpTemplate(getHelpTemplate())
 }

core/internal/greeter/installer.go

@@ -16,6 +16,7 @@ import (
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/config"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/distros"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/matugen"
+	sharedpam "github.com/AvengeMedia/DankMaterialShell/core/internal/pam"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/utils"
 	"github.com/sblinch/kdl-go"
 	"github.com/sblinch/kdl-go/document"
@@ -25,26 +26,7 @@ var appArmorProfileData []byte
 
 const appArmorProfileDest = "/etc/apparmor.d/usr.bin.dms-greeter"
 
-const (
+const GreeterCacheDir = "/var/cache/dms-greeter"
-	GreeterCacheDir = "/var/cache/dms-greeter"
-
-	GreeterPamManagedBlockStart = "# BEGIN DMS GREETER AUTH (managed by dms greeter sync)"
-	GreeterPamManagedBlockEnd   = "# END DMS GREETER AUTH"
-
-	legacyGreeterPamFprintComment = "# DMS greeter fingerprint"
-	legacyGreeterPamU2FComment    = "# DMS greeter U2F"
-)
-
-// Common PAM auth stack names referenced by greetd across supported distros.
-var includedPamAuthFiles = []string{
-	"system-auth",
-	"common-auth",
-	"password-auth",
-	"system-login",
-	"system-local-login",
-	"common-auth-pc",
-	"login",
-}
 
 func DetectDMSPath() (string, error) {
 	return config.LocateDMSConfig()
@@ -749,49 +731,6 @@ func InstallAppArmorProfile(logFunc func(string), sudoPassword string) error {
 	return nil
 }
 
-// RemoveGreeterPamManagedBlock strips the DMS managed auth block from /etc/pam.d/greetd
-func RemoveGreeterPamManagedBlock(logFunc func(string), sudoPassword string) error {
-	if IsNixOS() {
-		return nil
-	}
-	const greetdPamPath = "/etc/pam.d/greetd"
-	data, err := os.ReadFile(greetdPamPath)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return fmt.Errorf("failed to read %s: %w", greetdPamPath, err)
-	}
-
-	stripped, removed := stripManagedGreeterPamBlock(string(data))
-	strippedAgain, removedLegacy := stripLegacyGreeterPamLines(stripped)
-	if !removed && !removedLegacy {
-		return nil
-	}
-
-	tmp, err := os.CreateTemp("", "dms-pam-greetd-*")
-	if err != nil {
-		return fmt.Errorf("failed to create temp PAM file: %w", err)
-	}
-	tmpPath := tmp.Name()
-	defer os.Remove(tmpPath)
-
-	if _, err := tmp.WriteString(strippedAgain); err != nil {
-		tmp.Close()
-		return fmt.Errorf("failed to write temp PAM file: %w", err)
-	}
-	tmp.Close()
-
-	if err := runSudoCmd(sudoPassword, "cp", tmpPath, greetdPamPath); err != nil {
-		return fmt.Errorf("failed to write PAM config: %w", err)
-	}
-	if err := runSudoCmd(sudoPassword, "chmod", "644", greetdPamPath); err != nil {
-		return fmt.Errorf("failed to set PAM config permissions: %w", err)
-	}
-	logFunc("  ✓ Removed DMS managed PAM block from " + greetdPamPath)
-	return nil
-}
-
 // UninstallAppArmorProfile removes the DMS AppArmor profile and reloads AppArmor.
 // It is a no-op when AppArmor is not active or the profile does not exist.
 func UninstallAppArmorProfile(logFunc func(string), sudoPassword string) error {
@@ -1322,7 +1261,7 @@ func syncGreeterColorSource(homeDir, cacheDir string, state greeterThemeSyncStat
 	return nil
 }
 
-func SyncDMSConfigs(dmsPath, compositor string, logFunc func(string), sudoPassword string, forceAuth bool) error {
+func SyncDMSConfigs(dmsPath, compositor string, logFunc func(string), sudoPassword string) error {
 	homeDir, err := os.UserHomeDir()
 	if err != nil {
 		return fmt.Errorf("failed to get user home directory: %w", err)
@@ -1387,10 +1326,6 @@ func SyncDMSConfigs(dmsPath, compositor string, logFunc func(string), sudoPasswo
 		return fmt.Errorf("greeter wallpaper override sync failed: %w", err)
 	}
 
-	if err := syncGreeterPamConfig(homeDir, logFunc, sudoPassword, forceAuth); err != nil {
-		return fmt.Errorf("greeter PAM config sync failed: %w", err)
-	}
-
 	if strings.ToLower(compositor) != "niri" {
 		return nil
 	}
@@ -1439,378 +1374,6 @@ func syncGreeterWallpaperOverride(cacheDir string, logFunc func(string), sudoPas
 	return nil
 }
 
-func pamModuleExists(module string) bool {
-	for _, libDir := range []string{
-		"/usr/lib64/security",
-		"/usr/lib/security",
-		"/lib64/security",
-		"/lib/security",
-		"/lib/x86_64-linux-gnu/security",
-		"/usr/lib/x86_64-linux-gnu/security",
-		"/lib/aarch64-linux-gnu/security",
-		"/usr/lib/aarch64-linux-gnu/security",
-		"/run/current-system/sw/lib64/security",
-		"/run/current-system/sw/lib/security",
-	} {
-		if _, err := os.Stat(filepath.Join(libDir, module)); err == nil {
-			return true
-		}
-	}
-	return false
-}
-
-func stripManagedGreeterPamBlock(content string) (string, bool) {
-	lines := strings.Split(content, "\n")
-	filtered := make([]string, 0, len(lines))
-	inManagedBlock := false
-	removed := false
-
-	for _, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		if trimmed == GreeterPamManagedBlockStart {
-			inManagedBlock = true
-			removed = true
-			continue
-		}
-		if trimmed == GreeterPamManagedBlockEnd {
-			inManagedBlock = false
-			removed = true
-			continue
-		}
-		if inManagedBlock {
-			removed = true
-			continue
-		}
-		filtered = append(filtered, line)
-	}
-
-	return strings.Join(filtered, "\n"), removed
-}
-
-func stripLegacyGreeterPamLines(content string) (string, bool) {
-	lines := strings.Split(content, "\n")
-	filtered := make([]string, 0, len(lines))
-	removed := false
-
-	for i := 0; i < len(lines); i++ {
-		trimmed := strings.TrimSpace(lines[i])
-		if strings.HasPrefix(trimmed, legacyGreeterPamFprintComment) || strings.HasPrefix(trimmed, legacyGreeterPamU2FComment) {
-			removed = true
-			if i+1 < len(lines) {
-				nextLine := strings.TrimSpace(lines[i+1])
-				if strings.HasPrefix(nextLine, "auth") &&
-					(strings.Contains(nextLine, "pam_fprintd") || strings.Contains(nextLine, "pam_u2f")) {
-					i++
-				}
-			}
-			continue
-		}
-		filtered = append(filtered, lines[i])
-	}
-
-	return strings.Join(filtered, "\n"), removed
-}
-
-func insertManagedGreeterPamBlock(content string, blockLines []string, greetdPamPath string) (string, error) {
-	lines := strings.Split(content, "\n")
-	for i, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		if trimmed != "" && !strings.HasPrefix(trimmed, "#") && strings.HasPrefix(trimmed, "auth") {
-			block := strings.Join(blockLines, "\n")
-			prefix := strings.Join(lines[:i], "\n")
-			suffix := strings.Join(lines[i:], "\n")
-			switch {
-			case prefix == "":
-				return block + "\n" + suffix, nil
-			case suffix == "":
-				return prefix + "\n" + block, nil
-			default:
-				return prefix + "\n" + block + "\n" + suffix, nil
-			}
-		}
-	}
-	return "", fmt.Errorf("no auth directive found in %s", greetdPamPath)
-}
-
-func PamTextIncludesFile(pamText, filename string) bool {
-	lines := strings.Split(pamText, "\n")
-	for _, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
-			continue
-		}
-		if strings.Contains(trimmed, filename) &&
-			(strings.Contains(trimmed, "include") || strings.Contains(trimmed, "substack") || strings.HasPrefix(trimmed, "@include")) {
-			return true
-		}
-	}
-	return false
-}
-
-func PamFileHasModule(pamFilePath, module string) bool {
-	data, err := os.ReadFile(pamFilePath)
-	if err != nil {
-		return false
-	}
-	lines := strings.Split(string(data), "\n")
-	for _, line := range lines {
-		trimmed := strings.TrimSpace(line)
-		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
-			continue
-		}
-		if strings.Contains(trimmed, module) {
-			return true
-		}
-	}
-	return false
-}
-
-func DetectIncludedPamModule(pamText, module string) string {
-	for _, includedFile := range includedPamAuthFiles {
-		if PamTextIncludesFile(pamText, includedFile) && PamFileHasModule("/etc/pam.d/"+includedFile, module) {
-			return includedFile
-		}
-	}
-	return ""
-}
-
-type greeterAuthSettings struct {
-	GreeterEnableFprint bool `json:"greeterEnableFprint"`
-	GreeterEnableU2f    bool `json:"greeterEnableU2f"`
-}
-
-func readGreeterAuthSettings(homeDir string) (greeterAuthSettings, error) {
-	settingsPath := filepath.Join(homeDir, ".config", "DankMaterialShell", "settings.json")
-	data, err := os.ReadFile(settingsPath)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return greeterAuthSettings{}, nil
-		}
-		return greeterAuthSettings{}, fmt.Errorf("failed to read settings at %s: %w", settingsPath, err)
-	}
-	if strings.TrimSpace(string(data)) == "" {
-		return greeterAuthSettings{}, nil
-	}
-	var settings greeterAuthSettings
-	if err := json.Unmarshal(data, &settings); err != nil {
-		return greeterAuthSettings{}, fmt.Errorf("failed to parse settings at %s: %w", settingsPath, err)
-	}
-	return settings, nil
-}
-
-func ReadGreeterAuthToggles(homeDir string) (enableFprint bool, enableU2f bool, err error) {
-	settings, err := readGreeterAuthSettings(homeDir)
-	if err != nil {
-		return false, false, err
-	}
-	return settings.GreeterEnableFprint, settings.GreeterEnableU2f, nil
-}
-
-func hasEnrolledFingerprintOutput(output string) bool {
-	lower := strings.ToLower(output)
-	if strings.Contains(lower, "no fingers enrolled") ||
-		strings.Contains(lower, "no fingerprints enrolled") ||
-		strings.Contains(lower, "no prints enrolled") {
-		return false
-	}
-	if strings.Contains(lower, "has fingers enrolled") ||
-		strings.Contains(lower, "has fingerprints enrolled") {
-		return true
-	}
-	for _, line := range strings.Split(lower, "\n") {
-		trimmed := strings.TrimSpace(line)
-		if strings.HasPrefix(trimmed, "finger:") {
-			return true
-		}
-		if strings.HasPrefix(trimmed, "- ") && strings.Contains(trimmed, "finger") {
-			return true
-		}
-	}
-	return false
-}
-
-func FingerprintAuthAvailableForUser(username string) bool {
-	username = strings.TrimSpace(username)
-	if username == "" {
-		return false
-	}
-	if !pamModuleExists("pam_fprintd.so") {
-		return false
-	}
-	if _, err := exec.LookPath("fprintd-list"); err != nil {
-		return false
-	}
-	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
-	defer cancel()
-	out, err := exec.CommandContext(ctx, "fprintd-list", username).CombinedOutput()
-	if err != nil {
-		return false
-	}
-	return hasEnrolledFingerprintOutput(string(out))
-}
-
-func FingerprintAuthAvailableForCurrentUser() bool {
-	username := strings.TrimSpace(os.Getenv("SUDO_USER"))
-	if username == "" {
-		username = strings.TrimSpace(os.Getenv("USER"))
-	}
-	if username == "" {
-		out, err := exec.Command("id", "-un").Output()
-		if err == nil {
-			username = strings.TrimSpace(string(out))
-		}
-	}
-	return FingerprintAuthAvailableForUser(username)
-}
-
-func pamManagerHintForCurrentDistro() string {
-	osInfo, err := distros.GetOSInfo()
-	if err != nil {
-		return "Disable it in your PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
-	}
-	config, exists := distros.Registry[osInfo.Distribution.ID]
-	if !exists {
-		return "Disable it in your PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
-	}
-
-	switch config.Family {
-	case distros.FamilyFedora:
-		return "Disable it in authselect to force password-only greeter login."
-	case distros.FamilyDebian, distros.FamilyUbuntu:
-		return "Disable it in pam-auth-update to force password-only greeter login."
-	default:
-		return "Disable it in your distro PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
-	}
-}
-
-func syncGreeterPamConfig(homeDir string, logFunc func(string), sudoPassword string, forceAuth bool) error {
-	var wantFprint, wantU2f bool
-	fprintToggleEnabled := forceAuth
-	u2fToggleEnabled := forceAuth
-	if forceAuth {
-		wantFprint = pamModuleExists("pam_fprintd.so")
-		wantU2f = pamModuleExists("pam_u2f.so")
-	} else {
-		settings, err := readGreeterAuthSettings(homeDir)
-		if err != nil {
-			return err
-		}
-		fprintToggleEnabled = settings.GreeterEnableFprint
-		u2fToggleEnabled = settings.GreeterEnableU2f
-		fprintModule := pamModuleExists("pam_fprintd.so")
-		u2fModule := pamModuleExists("pam_u2f.so")
-		wantFprint = settings.GreeterEnableFprint && fprintModule
-		wantU2f = settings.GreeterEnableU2f && u2fModule
-		if settings.GreeterEnableFprint && !fprintModule {
-			logFunc("⚠ Warning: greeter fingerprint toggle is enabled, but pam_fprintd.so was not found.")
-		}
-		if settings.GreeterEnableU2f && !u2fModule {
-			logFunc("⚠ Warning: greeter security key toggle is enabled, but pam_u2f.so was not found.")
-		}
-	}
-
-	if IsNixOS() {
-		logFunc("ℹ NixOS detected: PAM config is managed by NixOS modules. Skipping DMS PAM block write.")
-		logFunc("  Configure fingerprint/U2F auth via your greetd NixOS module options (e.g. security.pam.services.greetd).")
-		return nil
-	}
-
-	greetdPamPath := "/etc/pam.d/greetd"
-	pamData, err := os.ReadFile(greetdPamPath)
-	if err != nil {
-		return fmt.Errorf("failed to read %s: %w", greetdPamPath, err)
-	}
-	originalContent := string(pamData)
-	content, _ := stripManagedGreeterPamBlock(originalContent)
-	content, _ = stripLegacyGreeterPamLines(content)
-
-	includedFprintFile := DetectIncludedPamModule(content, "pam_fprintd.so")
-	includedU2fFile := DetectIncludedPamModule(content, "pam_u2f.so")
-	fprintAvailableForCurrentUser := FingerprintAuthAvailableForCurrentUser()
-	if wantFprint && includedFprintFile != "" {
-		logFunc("⚠ pam_fprintd already present in included " + includedFprintFile + " (managed by authselect/pam-auth-update). Skipping DMS fprint block to avoid double-fingerprint auth.")
-		wantFprint = false
-	}
-	if wantU2f && includedU2fFile != "" {
-		logFunc("⚠ pam_u2f already present in included " + includedU2fFile + " (managed by authselect/pam-auth-update). Skipping DMS U2F block to avoid double security-key auth.")
-		wantU2f = false
-	}
-	if !wantFprint && includedFprintFile != "" {
-		if fprintToggleEnabled {
-			logFunc("ℹ Fingerprint auth is still enabled via included " + includedFprintFile + ".")
-			if fprintAvailableForCurrentUser {
-				logFunc("  DMS toggle is enabled, and effective auth is provided by the included PAM stack.")
-			} else {
-				logFunc("  No enrolled fingerprints detected for the current user; password auth remains the effective path.")
-			}
-		} else {
-			if fprintAvailableForCurrentUser {
-				logFunc("ℹ Fingerprint auth is active via included " + includedFprintFile + " while DMS fingerprint toggle is off.")
-				logFunc("  Password login will work but may be delayed while the fingerprint module runs first.")
-				logFunc("  To eliminate the delay, " + pamManagerHintForCurrentDistro())
-			} else {
-				logFunc("ℹ pam_fprintd is present via included " + includedFprintFile + ", but no enrolled fingerprints were detected for the current user.")
-				logFunc("  Password auth remains the effective login path.")
-			}
-		}
-	}
-	if !wantU2f && includedU2fFile != "" {
-		if u2fToggleEnabled {
-			logFunc("ℹ Security-key auth is still enabled via included " + includedU2fFile + ".")
-			logFunc("  DMS toggle is enabled, but effective auth is provided by the included PAM stack.")
-		} else {
-			logFunc("⚠ Security-key auth is active via included " + includedU2fFile + " while DMS security-key toggle is off.")
-			logFunc("  " + pamManagerHintForCurrentDistro())
-		}
-	}
-
-	if wantFprint || wantU2f {
-		blockLines := []string{GreeterPamManagedBlockStart}
-		if wantFprint {
-			blockLines = append(blockLines, "auth sufficient pam_fprintd.so max-tries=1 timeout=5")
-		}
-		if wantU2f {
-			blockLines = append(blockLines, "auth sufficient pam_u2f.so cue nouserok timeout=10")
-		}
-		blockLines = append(blockLines, GreeterPamManagedBlockEnd)
-
-		content, err = insertManagedGreeterPamBlock(content, blockLines, greetdPamPath)
-		if err != nil {
-			return err
-		}
-	}
-
-	if content == originalContent {
-		return nil
-	}
-
-	tmpFile, err := os.CreateTemp("", "greetd-pam-*.conf")
-	if err != nil {
-		return err
-	}
-	tmpPath := tmpFile.Name()
-	defer os.Remove(tmpPath)
-	if _, err := tmpFile.WriteString(content); err != nil {
-		tmpFile.Close()
-		return err
-	}
-	if err := tmpFile.Close(); err != nil {
-		return err
-	}
-	if err := runSudoCmd(sudoPassword, "cp", tmpPath, greetdPamPath); err != nil {
-		return fmt.Errorf("failed to install updated PAM config at %s: %w", greetdPamPath, err)
-	}
-	if err := runSudoCmd(sudoPassword, "chmod", "644", greetdPamPath); err != nil {
-		return fmt.Errorf("failed to set permissions on %s: %w", greetdPamPath, err)
-	}
-	if wantFprint || wantU2f {
-		logFunc("✓ Configured greetd PAM for fingerprint/U2F")
-	} else {
-		logFunc("✓ Cleared DMS-managed greeter PAM auth block")
-	}
-	return nil
-}
-
 type niriGreeterSync struct {
 	processed   map[string]bool
 	nodes       []*document.Node
@@ -2484,10 +2047,15 @@ func AutoSetupGreeter(compositor, sudoPassword string, logFunc func(string)) err
 	}
 
 	logFunc("Synchronizing DMS configurations...")
-	if err := SyncDMSConfigs(dmsPath, compositor, logFunc, sudoPassword, false); err != nil {
+	if err := SyncDMSConfigs(dmsPath, compositor, logFunc, sudoPassword); err != nil {
 		logFunc(fmt.Sprintf("⚠ Warning: config sync error: %v", err))
 	}
 
+	logFunc("Configuring authentication...")
+	if err := sharedpam.SyncAuthConfig(logFunc, sudoPassword, sharedpam.SyncAuthOptions{}); err != nil {
+		return fmt.Errorf("failed to sync authentication: %w", err)
+	}
+
 	logFunc("Checking for conflicting display managers...")
 	if err := DisableConflictingDisplayManagers(sudoPassword, logFunc); err != nil {
 		logFunc(fmt.Sprintf("⚠ Warning: %v", err))

core/internal/greeter/installer_test.go

@@ -6,7 +6,7 @@ import (
 	"testing"
 )
 
-func writeTestJSON(t *testing.T, path string, content string) {
+func writeTestFile(t *testing.T, path string, content string) {
 	t.Helper()
 	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
 		t.Fatalf("failed to create parent dir for %s: %v", path, err)
@@ -70,8 +70,8 @@ func TestResolveGreeterThemeSyncState(t *testing.T) {
 			t.Parallel()
 
 			homeDir := t.TempDir()
-			writeTestJSON(t, filepath.Join(homeDir, ".config", "DankMaterialShell", "settings.json"), tt.settingsJSON)
+			writeTestFile(t, filepath.Join(homeDir, ".config", "DankMaterialShell", "settings.json"), tt.settingsJSON)
-			writeTestJSON(t, filepath.Join(homeDir, ".local", "state", "DankMaterialShell", "session.json"), tt.sessionJSON)
+			writeTestFile(t, filepath.Join(homeDir, ".local", "state", "DankMaterialShell", "session.json"), tt.sessionJSON)
 
 			state, err := resolveGreeterThemeSyncState(homeDir)
 			if err != nil {

core/internal/pam/pam.go

@@ -0,0 +1,892 @@
+package pam
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/distros"
+)
+
+const (
+	GreeterPamManagedBlockStart = "# BEGIN DMS GREETER AUTH (managed by dms greeter sync)"
+	GreeterPamManagedBlockEnd   = "# END DMS GREETER AUTH"
+
+	LockscreenPamManagedBlockStart = "# BEGIN DMS LOCKSCREEN AUTH (managed by dms greeter sync)"
+	LockscreenPamManagedBlockEnd   = "# END DMS LOCKSCREEN AUTH"
+
+	LockscreenU2FPamManagedBlockStart = "# BEGIN DMS LOCKSCREEN U2F AUTH (managed by dms auth sync)"
+	LockscreenU2FPamManagedBlockEnd   = "# END DMS LOCKSCREEN U2F AUTH"
+
+	legacyGreeterPamFprintComment = "# DMS greeter fingerprint"
+	legacyGreeterPamU2FComment    = "# DMS greeter U2F"
+
+	GreetdPamPath       = "/etc/pam.d/greetd"
+	DankshellPamPath    = "/etc/pam.d/dankshell"
+	DankshellU2FPamPath = "/etc/pam.d/dankshell-u2f"
+)
+
+var includedPamAuthFiles = []string{
+	"system-auth",
+	"common-auth",
+	"password-auth",
+	"system-login",
+	"system-local-login",
+	"common-auth-pc",
+	"login",
+}
+
+type AuthSettings struct {
+	EnableFprint        bool `json:"enableFprint"`
+	EnableU2f           bool `json:"enableU2f"`
+	GreeterEnableFprint bool `json:"greeterEnableFprint"`
+	GreeterEnableU2f    bool `json:"greeterEnableU2f"`
+}
+
+type SyncAuthOptions struct {
+	HomeDir          string
+	ForceGreeterAuth bool
+}
+
+type syncDeps struct {
+	pamDir                             string
+	greetdPath                         string
+	dankshellPath                      string
+	dankshellU2fPath                   string
+	isNixOS                            func() bool
+	readFile                           func(string) ([]byte, error)
+	stat                               func(string) (os.FileInfo, error)
+	createTemp                         func(string, string) (*os.File, error)
+	removeFile                         func(string) error
+	runSudoCmd                         func(string, string, ...string) error
+	pamModuleExists                    func(string) bool
+	fingerprintAvailableForCurrentUser func() bool
+}
+
+type lockscreenPamIncludeDirective struct {
+	target     string
+	filterType string
+}
+
+type lockscreenPamResolver struct {
+	pamDir   string
+	readFile func(string) ([]byte, error)
+}
+
+func defaultSyncDeps() syncDeps {
+	return syncDeps{
+		pamDir:                             "/etc/pam.d",
+		greetdPath:                         GreetdPamPath,
+		dankshellPath:                      DankshellPamPath,
+		dankshellU2fPath:                   DankshellU2FPamPath,
+		isNixOS:                            IsNixOS,
+		readFile:                           os.ReadFile,
+		stat:                               os.Stat,
+		createTemp:                         os.CreateTemp,
+		removeFile:                         os.Remove,
+		runSudoCmd:                         runSudoCmd,
+		pamModuleExists:                    pamModuleExists,
+		fingerprintAvailableForCurrentUser: FingerprintAuthAvailableForCurrentUser,
+	}
+}
+
+func IsNixOS() bool {
+	_, err := os.Stat("/etc/NIXOS")
+	return err == nil
+}
+
+func ReadAuthSettings(homeDir string) (AuthSettings, error) {
+	settingsPath := filepath.Join(homeDir, ".config", "DankMaterialShell", "settings.json")
+	data, err := os.ReadFile(settingsPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return AuthSettings{}, nil
+		}
+		return AuthSettings{}, fmt.Errorf("failed to read settings at %s: %w", settingsPath, err)
+	}
+	if strings.TrimSpace(string(data)) == "" {
+		return AuthSettings{}, nil
+	}
+
+	var settings AuthSettings
+	if err := json.Unmarshal(data, &settings); err != nil {
+		return AuthSettings{}, fmt.Errorf("failed to parse settings at %s: %w", settingsPath, err)
+	}
+	return settings, nil
+}
+
+func ReadGreeterAuthToggles(homeDir string) (enableFprint bool, enableU2f bool, err error) {
+	settings, err := ReadAuthSettings(homeDir)
+	if err != nil {
+		return false, false, err
+	}
+	return settings.GreeterEnableFprint, settings.GreeterEnableU2f, nil
+}
+
+func SyncAuthConfig(logFunc func(string), sudoPassword string, options SyncAuthOptions) error {
+	return syncAuthConfigWithDeps(logFunc, sudoPassword, options, defaultSyncDeps())
+}
+
+func RemoveManagedGreeterPamBlock(logFunc func(string), sudoPassword string) error {
+	return removeManagedGreeterPamBlockWithDeps(logFunc, sudoPassword, defaultSyncDeps())
+}
+
+func syncAuthConfigWithDeps(logFunc func(string), sudoPassword string, options SyncAuthOptions, deps syncDeps) error {
+	homeDir := strings.TrimSpace(options.HomeDir)
+	if homeDir == "" {
+		var err error
+		homeDir, err = os.UserHomeDir()
+		if err != nil {
+			return fmt.Errorf("failed to get user home directory: %w", err)
+		}
+	}
+
+	settings, err := ReadAuthSettings(homeDir)
+	if err != nil {
+		return err
+	}
+
+	if err := syncLockscreenPamConfigWithDeps(logFunc, sudoPassword, deps); err != nil {
+		return err
+	}
+	if err := syncLockscreenU2FPamConfigWithDeps(logFunc, sudoPassword, settings.EnableU2f, deps); err != nil {
+		return err
+	}
+
+	if _, err := deps.stat(deps.greetdPath); err != nil {
+		if os.IsNotExist(err) {
+			logFunc("ℹ /etc/pam.d/greetd not found. Skipping greeter PAM sync.")
+			return nil
+		}
+		return fmt.Errorf("failed to inspect %s: %w", deps.greetdPath, err)
+	}
+
+	if err := syncGreeterPamConfigWithDeps(logFunc, sudoPassword, settings, options.ForceGreeterAuth, deps); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func removeManagedGreeterPamBlockWithDeps(logFunc func(string), sudoPassword string, deps syncDeps) error {
+	if deps.isNixOS() {
+		return nil
+	}
+
+	data, err := deps.readFile(deps.greetdPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("failed to read %s: %w", deps.greetdPath, err)
+	}
+
+	originalContent := string(data)
+	stripped, removed := stripManagedGreeterPamBlock(originalContent)
+	strippedAgain, removedLegacy := stripLegacyGreeterPamLines(stripped)
+	if !removed && !removedLegacy {
+		return nil
+	}
+
+	if err := writeManagedPamFile(strippedAgain, deps.greetdPath, sudoPassword, deps); err != nil {
+		return fmt.Errorf("failed to write %s: %w", deps.greetdPath, err)
+	}
+
+	logFunc("✓ Removed DMS managed PAM block from " + deps.greetdPath)
+	return nil
+}
+
+func ParseManagedGreeterPamAuth(pamText string) (managed bool, fingerprint bool, u2f bool, legacy bool) {
+	if pamText == "" {
+		return false, false, false, false
+	}
+
+	lines := strings.Split(pamText, "\n")
+	inManaged := false
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		switch trimmed {
+		case GreeterPamManagedBlockStart:
+			managed = true
+			inManaged = true
+			continue
+		case GreeterPamManagedBlockEnd:
+			inManaged = false
+			continue
+		}
+
+		if strings.HasPrefix(trimmed, legacyGreeterPamFprintComment) || strings.HasPrefix(trimmed, legacyGreeterPamU2FComment) {
+			legacy = true
+		}
+		if !inManaged {
+			continue
+		}
+		if strings.Contains(trimmed, "pam_fprintd") {
+			fingerprint = true
+		}
+		if strings.Contains(trimmed, "pam_u2f") {
+			u2f = true
+		}
+	}
+
+	return managed, fingerprint, u2f, legacy
+}
+
+func StripManagedGreeterPamContent(pamText string) (string, bool) {
+	stripped, removed := stripManagedGreeterPamBlock(pamText)
+	stripped, removedLegacy := stripLegacyGreeterPamLines(stripped)
+	return stripped, removed || removedLegacy
+}
+
+func PamTextIncludesFile(pamText, filename string) bool {
+	lines := strings.Split(pamText, "\n")
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		if strings.Contains(trimmed, filename) &&
+			(strings.Contains(trimmed, "include") || strings.Contains(trimmed, "substack") || strings.HasPrefix(trimmed, "@include")) {
+			return true
+		}
+	}
+	return false
+}
+
+func PamFileHasModule(pamFilePath, module string) bool {
+	data, err := os.ReadFile(pamFilePath)
+	if err != nil {
+		return false
+	}
+	return pamContentHasModule(string(data), module)
+}
+
+func DetectIncludedPamModule(pamText, module string) string {
+	return detectIncludedPamModule(pamText, module, defaultSyncDeps())
+}
+
+func detectIncludedPamModule(pamText, module string, deps syncDeps) string {
+	for _, includedFile := range includedPamAuthFiles {
+		if !PamTextIncludesFile(pamText, includedFile) {
+			continue
+		}
+		path := filepath.Join(deps.pamDir, includedFile)
+		data, err := deps.readFile(path)
+		if err != nil {
+			continue
+		}
+		if pamContentHasModule(string(data), module) {
+			return includedFile
+		}
+	}
+	return ""
+}
+
+func pamContentHasModule(content, module string) bool {
+	lines := strings.Split(content, "\n")
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		if strings.Contains(trimmed, module) {
+			return true
+		}
+	}
+	return false
+}
+
+func hasManagedLockscreenPamFile(content string) bool {
+	return strings.Contains(content, LockscreenPamManagedBlockStart) &&
+		strings.Contains(content, LockscreenPamManagedBlockEnd)
+}
+
+func hasManagedLockscreenU2FPamFile(content string) bool {
+	return strings.Contains(content, LockscreenU2FPamManagedBlockStart) &&
+		strings.Contains(content, LockscreenU2FPamManagedBlockEnd)
+}
+
+func pamDirectiveType(line string) string {
+	fields := strings.Fields(line)
+	if len(fields) == 0 {
+		return ""
+	}
+
+	directiveType := strings.TrimPrefix(fields[0], "-")
+	switch directiveType {
+	case "auth", "account", "password", "session":
+		return directiveType
+	default:
+		return ""
+	}
+}
+
+func isExcludedLockscreenPamLine(line string) bool {
+	for _, field := range strings.Fields(line) {
+		if strings.HasPrefix(field, "#") {
+			break
+		}
+		if strings.Contains(field, "pam_u2f") || strings.Contains(field, "pam_fprintd") {
+			return true
+		}
+	}
+	return false
+}
+
+func parseLockscreenPamIncludeDirective(trimmed string, inheritedFilter string) (lockscreenPamIncludeDirective, bool) {
+	fields := strings.Fields(trimmed)
+	if len(fields) >= 2 && fields[0] == "@include" {
+		return lockscreenPamIncludeDirective{
+			target:     fields[1],
+			filterType: inheritedFilter,
+		}, true
+	}
+
+	if len(fields) >= 3 && (fields[1] == "include" || fields[1] == "substack") {
+		lineType := pamDirectiveType(trimmed)
+		if lineType == "" {
+			return lockscreenPamIncludeDirective{}, false
+		}
+		return lockscreenPamIncludeDirective{
+			target:     fields[2],
+			filterType: lineType,
+		}, true
+	}
+
+	if len(fields) >= 3 && fields[1] == "@include" {
+		lineType := pamDirectiveType(trimmed)
+		if lineType == "" {
+			return lockscreenPamIncludeDirective{}, false
+		}
+		return lockscreenPamIncludeDirective{
+			target:     fields[2],
+			filterType: lineType,
+		}, true
+	}
+
+	return lockscreenPamIncludeDirective{}, false
+}
+
+func resolveLockscreenPamIncludePath(pamDir, target string) (string, error) {
+	if strings.TrimSpace(target) == "" {
+		return "", fmt.Errorf("empty PAM include target")
+	}
+
+	cleanPamDir := filepath.Clean(pamDir)
+	if filepath.IsAbs(target) {
+		cleanTarget := filepath.Clean(target)
+		if filepath.Dir(cleanTarget) != cleanPamDir {
+			return "", fmt.Errorf("unsupported PAM include outside %s: %s", cleanPamDir, target)
+		}
+		return cleanTarget, nil
+	}
+
+	cleanTarget := filepath.Clean(target)
+	if cleanTarget == "." || cleanTarget == ".." || strings.HasPrefix(cleanTarget, ".."+string(os.PathSeparator)) {
+		return "", fmt.Errorf("invalid PAM include target: %s", target)
+	}
+
+	return filepath.Join(cleanPamDir, cleanTarget), nil
+}
+
+func (r lockscreenPamResolver) resolveService(serviceName string, filterType string, stack []string) ([]string, error) {
+	path, err := resolveLockscreenPamIncludePath(r.pamDir, serviceName)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, seen := range stack {
+		if seen == path {
+			chain := append(append([]string{}, stack...), path)
+			display := make([]string, 0, len(chain))
+			for _, item := range chain {
+				display = append(display, filepath.Base(item))
+			}
+			return nil, fmt.Errorf("cyclic PAM include detected: %s", strings.Join(display, " -> "))
+		}
+	}
+
+	data, err := r.readFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read PAM file %s: %w", path, err)
+	}
+
+	var resolved []string
+	for _, rawLine := range strings.Split(strings.ReplaceAll(string(data), "\r\n", "\n"), "\n") {
+		rawLine = strings.TrimRight(rawLine, "\r")
+		trimmed := strings.TrimSpace(rawLine)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") || trimmed == "#%PAM-1.0" {
+			continue
+		}
+
+		if include, ok := parseLockscreenPamIncludeDirective(trimmed, filterType); ok {
+			lineType := pamDirectiveType(trimmed)
+			if filterType != "" && lineType != "" && lineType != filterType {
+				continue
+			}
+
+			nested, err := r.resolveService(include.target, include.filterType, append(stack, path))
+			if err != nil {
+				return nil, err
+			}
+			resolved = append(resolved, nested...)
+			continue
+		}
+
+		lineType := pamDirectiveType(trimmed)
+		if lineType == "" {
+			return nil, fmt.Errorf("unsupported PAM directive in %s: %s", filepath.Base(path), trimmed)
+		}
+		if filterType != "" && lineType != filterType {
+			continue
+		}
+		if isExcludedLockscreenPamLine(trimmed) {
+			continue
+		}
+
+		resolved = append(resolved, rawLine)
+	}
+
+	return resolved, nil
+}
+
+func buildManagedLockscreenPamContent(pamDir string, readFile func(string) ([]byte, error)) (string, error) {
+	resolver := lockscreenPamResolver{
+		pamDir:   pamDir,
+		readFile: readFile,
+	}
+
+	resolvedLines, err := resolver.resolveService("login", "", nil)
+	if err != nil {
+		return "", err
+	}
+	if len(resolvedLines) == 0 {
+		return "", fmt.Errorf("no auth directives remained after filtering %s", filepath.Join(pamDir, "login"))
+	}
+
+	hasAuth := false
+	for _, line := range resolvedLines {
+		if pamDirectiveType(strings.TrimSpace(line)) == "auth" {
+			hasAuth = true
+			break
+		}
+	}
+	if !hasAuth {
+		return "", fmt.Errorf("no auth directives remained after filtering %s", filepath.Join(pamDir, "login"))
+	}
+
+	var b strings.Builder
+	b.WriteString("#%PAM-1.0\n")
+	b.WriteString(LockscreenPamManagedBlockStart + "\n")
+	for _, line := range resolvedLines {
+		b.WriteString(line)
+		b.WriteByte('\n')
+	}
+	b.WriteString(LockscreenPamManagedBlockEnd + "\n")
+	return b.String(), nil
+}
+
+func buildManagedLockscreenU2FPamContent() string {
+	var b strings.Builder
+	b.WriteString("#%PAM-1.0\n")
+	b.WriteString(LockscreenU2FPamManagedBlockStart + "\n")
+	b.WriteString("auth    required    pam_u2f.so  cue nouserok timeout=10\n")
+	b.WriteString(LockscreenU2FPamManagedBlockEnd + "\n")
+	return b.String()
+}
+
+func syncLockscreenPamConfigWithDeps(logFunc func(string), sudoPassword string, deps syncDeps) error {
+	if deps.isNixOS() {
+		logFunc("ℹ NixOS detected. DMS continues to use /etc/pam.d/login for lock screen password auth on NixOS unless you declare security.pam.services.dankshell yourself. U2F and fingerprint are handled separately and should not be included in dankshell.")
+		return nil
+	}
+
+	existingData, err := deps.readFile(deps.dankshellPath)
+	if err == nil {
+		if !hasManagedLockscreenPamFile(string(existingData)) {
+			logFunc("ℹ Custom /etc/pam.d/dankshell found (no DMS block). Skipping.")
+			return nil
+		}
+	} else if !os.IsNotExist(err) {
+		return fmt.Errorf("failed to read %s: %w", deps.dankshellPath, err)
+	}
+
+	content, err := buildManagedLockscreenPamContent(deps.pamDir, deps.readFile)
+	if err != nil {
+		return fmt.Errorf("failed to build %s from %s: %w", deps.dankshellPath, filepath.Join(deps.pamDir, "login"), err)
+	}
+
+	if err := writeManagedPamFile(content, deps.dankshellPath, sudoPassword, deps); err != nil {
+		return fmt.Errorf("failed to write %s: %w", deps.dankshellPath, err)
+	}
+
+	logFunc("✓ Created or updated /etc/pam.d/dankshell for lock screen authentication")
+	return nil
+}
+
+func syncLockscreenU2FPamConfigWithDeps(logFunc func(string), sudoPassword string, enabled bool, deps syncDeps) error {
+	if deps.isNixOS() {
+		logFunc("ℹ NixOS detected. DMS does not manage /etc/pam.d/dankshell-u2f on NixOS. Keep using the bundled U2F helper or configure a custom PAM service yourself.")
+		return nil
+	}
+
+	existingData, err := deps.readFile(deps.dankshellU2fPath)
+	if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("failed to read %s: %w", deps.dankshellU2fPath, err)
+	}
+
+	if enabled {
+		if err == nil && !hasManagedLockscreenU2FPamFile(string(existingData)) {
+			logFunc("ℹ Custom /etc/pam.d/dankshell-u2f found (no DMS block). Skipping.")
+			return nil
+		}
+		if err := writeManagedPamFile(buildManagedLockscreenU2FPamContent(), deps.dankshellU2fPath, sudoPassword, deps); err != nil {
+			return fmt.Errorf("failed to write %s: %w", deps.dankshellU2fPath, err)
+		}
+		logFunc("✓ Created or updated /etc/pam.d/dankshell-u2f for lock screen security-key authentication")
+		return nil
+	}
+
+	if os.IsNotExist(err) {
+		return nil
+	}
+	if err == nil && !hasManagedLockscreenU2FPamFile(string(existingData)) {
+		logFunc("ℹ Custom /etc/pam.d/dankshell-u2f found (no DMS block). Leaving it untouched.")
+		return nil
+	}
+
+	if err := deps.runSudoCmd(sudoPassword, "rm", "-f", deps.dankshellU2fPath); err != nil {
+		return fmt.Errorf("failed to remove %s: %w", deps.dankshellU2fPath, err)
+	}
+	logFunc("✓ Removed DMS-managed /etc/pam.d/dankshell-u2f")
+	return nil
+}
+
+func stripManagedGreeterPamBlock(content string) (string, bool) {
+	lines := strings.Split(content, "\n")
+	filtered := make([]string, 0, len(lines))
+	inManagedBlock := false
+	removed := false
+
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == GreeterPamManagedBlockStart {
+			inManagedBlock = true
+			removed = true
+			continue
+		}
+		if trimmed == GreeterPamManagedBlockEnd {
+			inManagedBlock = false
+			removed = true
+			continue
+		}
+		if inManagedBlock {
+			removed = true
+			continue
+		}
+		filtered = append(filtered, line)
+	}
+
+	return strings.Join(filtered, "\n"), removed
+}
+
+func stripLegacyGreeterPamLines(content string) (string, bool) {
+	lines := strings.Split(content, "\n")
+	filtered := make([]string, 0, len(lines))
+	removed := false
+
+	for i := 0; i < len(lines); i++ {
+		trimmed := strings.TrimSpace(lines[i])
+		if strings.HasPrefix(trimmed, legacyGreeterPamFprintComment) || strings.HasPrefix(trimmed, legacyGreeterPamU2FComment) {
+			removed = true
+			if i+1 < len(lines) {
+				nextLine := strings.TrimSpace(lines[i+1])
+				if strings.HasPrefix(nextLine, "auth") &&
+					(strings.Contains(nextLine, "pam_fprintd") || strings.Contains(nextLine, "pam_u2f")) {
+					i++
+				}
+			}
+			continue
+		}
+		filtered = append(filtered, lines[i])
+	}
+
+	return strings.Join(filtered, "\n"), removed
+}
+
+func insertManagedGreeterPamBlock(content string, blockLines []string, greetdPamPath string) (string, error) {
+	lines := strings.Split(content, "\n")
+	for i, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed != "" && !strings.HasPrefix(trimmed, "#") && strings.HasPrefix(trimmed, "auth") {
+			block := strings.Join(blockLines, "\n")
+			prefix := strings.Join(lines[:i], "\n")
+			suffix := strings.Join(lines[i:], "\n")
+			switch {
+			case prefix == "":
+				return block + "\n" + suffix, nil
+			case suffix == "":
+				return prefix + "\n" + block, nil
+			default:
+				return prefix + "\n" + block + "\n" + suffix, nil
+			}
+		}
+	}
+	return "", fmt.Errorf("no auth directive found in %s", greetdPamPath)
+}
+
+func syncGreeterPamConfigWithDeps(logFunc func(string), sudoPassword string, settings AuthSettings, forceAuth bool, deps syncDeps) error {
+	var wantFprint, wantU2f bool
+	fprintToggleEnabled := forceAuth
+	u2fToggleEnabled := forceAuth
+	if forceAuth {
+		wantFprint = deps.pamModuleExists("pam_fprintd.so")
+		wantU2f = deps.pamModuleExists("pam_u2f.so")
+	} else {
+		fprintToggleEnabled = settings.GreeterEnableFprint
+		u2fToggleEnabled = settings.GreeterEnableU2f
+		fprintModule := deps.pamModuleExists("pam_fprintd.so")
+		u2fModule := deps.pamModuleExists("pam_u2f.so")
+		wantFprint = settings.GreeterEnableFprint && fprintModule
+		wantU2f = settings.GreeterEnableU2f && u2fModule
+		if settings.GreeterEnableFprint && !fprintModule {
+			logFunc("⚠ Warning: greeter fingerprint toggle is enabled, but pam_fprintd.so was not found.")
+		}
+		if settings.GreeterEnableU2f && !u2fModule {
+			logFunc("⚠ Warning: greeter security key toggle is enabled, but pam_u2f.so was not found.")
+		}
+	}
+
+	if deps.isNixOS() {
+		logFunc("ℹ NixOS detected: PAM config is managed by NixOS modules. Skipping DMS PAM block write.")
+		logFunc("  Configure fingerprint/U2F auth via your greetd NixOS module options (e.g. security.pam.services.greetd).")
+		return nil
+	}
+
+	pamData, err := deps.readFile(deps.greetdPath)
+	if err != nil {
+		return fmt.Errorf("failed to read %s: %w", deps.greetdPath, err)
+	}
+	originalContent := string(pamData)
+	content, _ := stripManagedGreeterPamBlock(originalContent)
+	content, _ = stripLegacyGreeterPamLines(content)
+
+	includedFprintFile := detectIncludedPamModule(content, "pam_fprintd.so", deps)
+	includedU2fFile := detectIncludedPamModule(content, "pam_u2f.so", deps)
+	fprintAvailableForCurrentUser := deps.fingerprintAvailableForCurrentUser()
+	if wantFprint && includedFprintFile != "" {
+		logFunc("⚠ pam_fprintd already present in included " + includedFprintFile + " (managed by authselect/pam-auth-update). Skipping DMS fprint block to avoid double-fingerprint auth.")
+		wantFprint = false
+	}
+	if wantU2f && includedU2fFile != "" {
+		logFunc("⚠ pam_u2f already present in included " + includedU2fFile + " (managed by authselect/pam-auth-update). Skipping DMS U2F block to avoid double security-key auth.")
+		wantU2f = false
+	}
+	if !wantFprint && includedFprintFile != "" {
+		if fprintToggleEnabled {
+			logFunc("ℹ Fingerprint auth is still enabled via included " + includedFprintFile + ".")
+			if fprintAvailableForCurrentUser {
+				logFunc("  DMS toggle is enabled, and effective auth is provided by the included PAM stack.")
+			} else {
+				logFunc("  No enrolled fingerprints detected for the current user; password auth remains the effective path.")
+			}
+		} else {
+			if fprintAvailableForCurrentUser {
+				logFunc("ℹ Fingerprint auth is active via included " + includedFprintFile + " while DMS fingerprint toggle is off.")
+				logFunc("  Password login will work but may be delayed while the fingerprint module runs first.")
+				logFunc("  To eliminate the delay, " + pamManagerHintForCurrentDistro())
+			} else {
+				logFunc("ℹ pam_fprintd is present via included " + includedFprintFile + ", but no enrolled fingerprints were detected for the current user.")
+				logFunc("  Password auth remains the effective login path.")
+			}
+		}
+	}
+	if !wantU2f && includedU2fFile != "" {
+		if u2fToggleEnabled {
+			logFunc("ℹ Security-key auth is still enabled via included " + includedU2fFile + ".")
+			logFunc("  DMS toggle is enabled, but effective auth is provided by the included PAM stack.")
+		} else {
+			logFunc("⚠ Security-key auth is active via included " + includedU2fFile + " while DMS security-key toggle is off.")
+			logFunc("  " + pamManagerHintForCurrentDistro())
+		}
+	}
+
+	if wantFprint || wantU2f {
+		blockLines := []string{GreeterPamManagedBlockStart}
+		if wantFprint {
+			blockLines = append(blockLines, "auth sufficient pam_fprintd.so max-tries=1 timeout=5")
+		}
+		if wantU2f {
+			blockLines = append(blockLines, "auth sufficient pam_u2f.so cue nouserok timeout=10")
+		}
+		blockLines = append(blockLines, GreeterPamManagedBlockEnd)
+
+		content, err = insertManagedGreeterPamBlock(content, blockLines, deps.greetdPath)
+		if err != nil {
+			return err
+		}
+	}
+
+	if content == originalContent {
+		return nil
+	}
+
+	if err := writeManagedPamFile(content, deps.greetdPath, sudoPassword, deps); err != nil {
+		return fmt.Errorf("failed to install updated PAM config at %s: %w", deps.greetdPath, err)
+	}
+	if wantFprint || wantU2f {
+		logFunc("✓ Configured greetd PAM for fingerprint/U2F")
+	} else {
+		logFunc("✓ Cleared DMS-managed greeter PAM auth block")
+	}
+	return nil
+}
+
+func writeManagedPamFile(content string, destPath string, sudoPassword string, deps syncDeps) error {
+	tmpFile, err := deps.createTemp("", "dms-pam-*.conf")
+	if err != nil {
+		return err
+	}
+	tmpPath := tmpFile.Name()
+	defer func() {
+		_ = deps.removeFile(tmpPath)
+	}()
+
+	if _, err := tmpFile.WriteString(content); err != nil {
+		tmpFile.Close()
+		return err
+	}
+	if err := tmpFile.Close(); err != nil {
+		return err
+	}
+	if err := deps.runSudoCmd(sudoPassword, "cp", tmpPath, destPath); err != nil {
+		return err
+	}
+	if err := deps.runSudoCmd(sudoPassword, "chmod", "644", destPath); err != nil {
+		return fmt.Errorf("failed to set permissions on %s: %w", destPath, err)
+	}
+	return nil
+}
+
+func pamManagerHintForCurrentDistro() string {
+	osInfo, err := distros.GetOSInfo()
+	if err != nil {
+		return "Disable it in your PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
+	}
+	config, exists := distros.Registry[osInfo.Distribution.ID]
+	if !exists {
+		return "Disable it in your PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
+	}
+
+	switch config.Family {
+	case distros.FamilyFedora:
+		return "Disable it in authselect to force password-only greeter login."
+	case distros.FamilyDebian, distros.FamilyUbuntu:
+		return "Disable it in pam-auth-update to force password-only greeter login."
+	default:
+		return "Disable it in your distro PAM manager (authselect/pam-auth-update) or in the included PAM stack to force password-only greeter login."
+	}
+}
+
+func pamModuleExists(module string) bool {
+	for _, libDir := range []string{
+		"/usr/lib64/security",
+		"/usr/lib/security",
+		"/lib64/security",
+		"/lib/security",
+		"/lib/x86_64-linux-gnu/security",
+		"/usr/lib/x86_64-linux-gnu/security",
+		"/lib/aarch64-linux-gnu/security",
+		"/usr/lib/aarch64-linux-gnu/security",
+		"/run/current-system/sw/lib64/security",
+		"/run/current-system/sw/lib/security",
+	} {
+		if _, err := os.Stat(filepath.Join(libDir, module)); err == nil {
+			return true
+		}
+	}
+	return false
+}
+
+func hasEnrolledFingerprintOutput(output string) bool {
+	lower := strings.ToLower(output)
+	if strings.Contains(lower, "no fingers enrolled") ||
+		strings.Contains(lower, "no fingerprints enrolled") ||
+		strings.Contains(lower, "no prints enrolled") {
+		return false
+	}
+	if strings.Contains(lower, "has fingers enrolled") ||
+		strings.Contains(lower, "has fingerprints enrolled") {
+		return true
+	}
+	for _, line := range strings.Split(lower, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if strings.HasPrefix(trimmed, "finger:") {
+			return true
+		}
+		if strings.HasPrefix(trimmed, "- ") && strings.Contains(trimmed, "finger") {
+			return true
+		}
+	}
+	return false
+}
+
+func FingerprintAuthAvailableForCurrentUser() bool {
+	username := strings.TrimSpace(os.Getenv("SUDO_USER"))
+	if username == "" {
+		username = strings.TrimSpace(os.Getenv("USER"))
+	}
+	if username == "" {
+		out, err := exec.Command("id", "-un").Output()
+		if err == nil {
+			username = strings.TrimSpace(string(out))
+		}
+	}
+	return fingerprintAuthAvailableForUser(username)
+}
+
+func fingerprintAuthAvailableForUser(username string) bool {
+	username = strings.TrimSpace(username)
+	if username == "" {
+		return false
+	}
+	if !pamModuleExists("pam_fprintd.so") {
+		return false
+	}
+	if _, err := exec.LookPath("fprintd-list"); err != nil {
+		return false
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+	out, err := exec.CommandContext(ctx, "fprintd-list", username).CombinedOutput()
+	if err != nil {
+		return false
+	}
+	return hasEnrolledFingerprintOutput(string(out))
+}
+
+func runSudoCmd(sudoPassword string, command string, args ...string) error {
+	var cmd *exec.Cmd
+
+	if sudoPassword != "" {
+		fullArgs := append([]string{command}, args...)
+		quotedArgs := make([]string, len(fullArgs))
+		for i, arg := range fullArgs {
+			quotedArgs[i] = "'" + strings.ReplaceAll(arg, "'", "'\\''") + "'"
+		}
+		cmdStr := strings.Join(quotedArgs, " ")
+
+		cmd = distros.ExecSudoCommand(context.Background(), sudoPassword, cmdStr)
+	} else {
+		cmd = exec.Command("sudo", append([]string{command}, args...)...)
+	}
+
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}

core/internal/pam/pam_test.go

@@ -0,0 +1,671 @@
+package pam
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func writeTestFile(t *testing.T, path string, content string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("failed to create parent dir for %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatalf("failed to write %s: %v", path, err)
+	}
+}
+
+type pamTestEnv struct {
+	pamDir               string
+	greetdPath           string
+	dankshellPath        string
+	dankshellU2fPath     string
+	tmpDir               string
+	homeDir              string
+	availableModules     map[string]bool
+	fingerprintAvailable bool
+}
+
+func newPamTestEnv(t *testing.T) *pamTestEnv {
+	t.Helper()
+
+	root := t.TempDir()
+	pamDir := filepath.Join(root, "pam.d")
+	tmpDir := filepath.Join(root, "tmp")
+	homeDir := filepath.Join(root, "home")
+
+	for _, dir := range []string{pamDir, tmpDir, homeDir} {
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			t.Fatalf("failed to create %s: %v", dir, err)
+		}
+	}
+
+	return &pamTestEnv{
+		pamDir:           pamDir,
+		greetdPath:       filepath.Join(pamDir, "greetd"),
+		dankshellPath:    filepath.Join(pamDir, "dankshell"),
+		dankshellU2fPath: filepath.Join(pamDir, "dankshell-u2f"),
+		tmpDir:           tmpDir,
+		homeDir:          homeDir,
+		availableModules: map[string]bool{},
+	}
+}
+
+func (e *pamTestEnv) writePamFile(t *testing.T, name string, content string) {
+	t.Helper()
+	writeTestFile(t, filepath.Join(e.pamDir, name), content)
+}
+
+func (e *pamTestEnv) writeSettings(t *testing.T, content string) {
+	t.Helper()
+	writeTestFile(t, filepath.Join(e.homeDir, ".config", "DankMaterialShell", "settings.json"), content)
+}
+
+func (e *pamTestEnv) deps(isNixOS bool) syncDeps {
+	return syncDeps{
+		pamDir:           e.pamDir,
+		greetdPath:       e.greetdPath,
+		dankshellPath:    e.dankshellPath,
+		dankshellU2fPath: e.dankshellU2fPath,
+		isNixOS:          func() bool { return isNixOS },
+		readFile:         os.ReadFile,
+		stat:             os.Stat,
+		createTemp: func(_ string, pattern string) (*os.File, error) {
+			return os.CreateTemp(e.tmpDir, pattern)
+		},
+		removeFile: os.Remove,
+		runSudoCmd: func(_ string, command string, args ...string) error {
+			switch command {
+			case "cp":
+				if len(args) != 2 {
+					return fmt.Errorf("unexpected cp args: %v", args)
+				}
+				data, err := os.ReadFile(args[0])
+				if err != nil {
+					return err
+				}
+				if err := os.MkdirAll(filepath.Dir(args[1]), 0o755); err != nil {
+					return err
+				}
+				return os.WriteFile(args[1], data, 0o644)
+			case "chmod":
+				if len(args) != 2 {
+					return fmt.Errorf("unexpected chmod args: %v", args)
+				}
+				return nil
+			case "rm":
+				if len(args) != 2 || args[0] != "-f" {
+					return fmt.Errorf("unexpected rm args: %v", args)
+				}
+				if err := os.Remove(args[1]); err != nil && !os.IsNotExist(err) {
+					return err
+				}
+				return nil
+			default:
+				return fmt.Errorf("unexpected sudo command: %s %v", command, args)
+			}
+		},
+		pamModuleExists: func(module string) bool {
+			return e.availableModules[module]
+		},
+		fingerprintAvailableForCurrentUser: func() bool {
+			return e.fingerprintAvailable
+		},
+	}
+}
+
+func readFileString(t *testing.T, path string) string {
+	t.Helper()
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("failed to read %s: %v", path, err)
+	}
+	return string(data)
+}
+
+func TestHasManagedLockscreenPamFile(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		content string
+		want    bool
+	}{
+		{
+			name: "both markers present",
+			content: "#%PAM-1.0\n" +
+				LockscreenPamManagedBlockStart + "\n" +
+				"auth sufficient pam_unix.so\n" +
+				LockscreenPamManagedBlockEnd + "\n",
+			want: true,
+		},
+		{
+			name: "missing end marker is not managed",
+			content: "#%PAM-1.0\n" +
+				LockscreenPamManagedBlockStart + "\n" +
+				"auth sufficient pam_unix.so\n",
+			want: false,
+		},
+		{
+			name:    "custom file is not managed",
+			content: "#%PAM-1.0\nauth sufficient pam_unix.so\n",
+			want:    false,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := hasManagedLockscreenPamFile(tt.content); got != tt.want {
+				t.Fatalf("hasManagedLockscreenPamFile() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestBuildManagedLockscreenPamContent(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name            string
+		files           map[string]string
+		wantContains    []string
+		wantNotContains []string
+		wantCounts      map[string]int
+		wantErr         string
+	}{
+		{
+			name: "preserves custom modules and strips direct u2f and fprint directives",
+			files: map[string]string{
+				"login": "#%PAM-1.0\n" +
+					"auth include system-auth\n" +
+					"account include system-auth\n" +
+					"session include system-auth\n",
+				"system-auth": "auth requisite pam_nologin.so\n" +
+					"auth sufficient pam_unix.so try_first_pass nullok\n" +
+					"auth sufficient pam_u2f.so cue\n" +
+					"auth sufficient pam_fprintd.so max-tries=1\n" +
+					"auth required pam_radius_auth.so conf=/etc/raddb/server\n" +
+					"account required pam_access.so\n" +
+					"session optional pam_lastlog.so silent\n",
+			},
+			wantContains: []string{
+				"#%PAM-1.0",
+				LockscreenPamManagedBlockStart,
+				LockscreenPamManagedBlockEnd,
+				"auth requisite pam_nologin.so",
+				"auth sufficient pam_unix.so try_first_pass nullok",
+				"auth required pam_radius_auth.so conf=/etc/raddb/server",
+				"account required pam_access.so",
+				"session optional pam_lastlog.so silent",
+			},
+			wantNotContains: []string{
+				"pam_u2f",
+				"pam_fprintd",
+			},
+			wantCounts: map[string]int{
+				"auth required pam_radius_auth.so conf=/etc/raddb/server": 1,
+				"account required pam_access.so":                          1,
+			},
+		},
+		{
+			name: "resolves nested include substack and @include transitively",
+			files: map[string]string{
+				"login": "#%PAM-1.0\n" +
+					"auth include system-auth\n" +
+					"account include system-auth\n" +
+					"password include system-auth\n" +
+					"session include system-auth\n",
+				"system-auth": "auth substack custom-auth\n" +
+					"account include custom-auth\n" +
+					"password include custom-auth\n" +
+					"session @include common-session\n",
+				"custom-auth": "auth required pam_custom.so one=two\n" +
+					"account required pam_custom_account.so\n" +
+					"password required pam_custom_password.so\n",
+				"common-session": "session optional pam_fprintd.so max-tries=1\n" +
+					"session optional pam_lastlog.so silent\n",
+			},
+			wantContains: []string{
+				"auth required pam_custom.so one=two",
+				"account required pam_custom_account.so",
+				"password required pam_custom_password.so",
+				"session optional pam_lastlog.so silent",
+			},
+			wantNotContains: []string{
+				"pam_fprintd",
+			},
+			wantCounts: map[string]int{
+				"auth required pam_custom.so one=two":      1,
+				"account required pam_custom_account.so":   1,
+				"password required pam_custom_password.so": 1,
+				"session optional pam_lastlog.so silent":   1,
+			},
+		},
+		{
+			name: "missing include fails",
+			files: map[string]string{
+				"login": "#%PAM-1.0\nauth include missing-auth\n",
+			},
+			wantErr: "failed to read PAM file",
+		},
+		{
+			name: "cyclic include fails",
+			files: map[string]string{
+				"login":       "#%PAM-1.0\nauth include system-auth\n",
+				"system-auth": "auth include login\n",
+			},
+			wantErr: "cyclic PAM include detected",
+		},
+		{
+			name: "no auth directives remain after filtering fails",
+			files: map[string]string{
+				"login":       "#%PAM-1.0\nauth include system-auth\n",
+				"system-auth": "auth sufficient pam_u2f.so cue\n",
+			},
+			wantErr: "no auth directives remained after filtering",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			env := newPamTestEnv(t)
+			for name, content := range tt.files {
+				env.writePamFile(t, name, content)
+			}
+
+			content, err := buildManagedLockscreenPamContent(env.pamDir, os.ReadFile)
+			if tt.wantErr != "" {
+				if err == nil {
+					t.Fatalf("expected error containing %q, got nil", tt.wantErr)
+				}
+				if !strings.Contains(err.Error(), tt.wantErr) {
+					t.Fatalf("error = %q, want substring %q", err.Error(), tt.wantErr)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("buildManagedLockscreenPamContent returned error: %v", err)
+			}
+
+			for _, want := range tt.wantContains {
+				if !strings.Contains(content, want) {
+					t.Errorf("missing expected string %q in output:\n%s", want, content)
+				}
+			}
+			for _, notWant := range tt.wantNotContains {
+				if strings.Contains(content, notWant) {
+					t.Errorf("unexpected string %q found in output:\n%s", notWant, content)
+				}
+			}
+			for want, wantCount := range tt.wantCounts {
+				if gotCount := strings.Count(content, want); gotCount != wantCount {
+					t.Errorf("count for %q = %d, want %d\noutput:\n%s", want, gotCount, wantCount, content)
+				}
+			}
+		})
+	}
+}
+
+func TestSyncLockscreenPamConfigWithDeps(t *testing.T) {
+	t.Parallel()
+
+	t.Run("custom dankshell file is skipped untouched", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		customContent := "#%PAM-1.0\nauth required pam_unix.so\n"
+		env.writePamFile(t, "dankshell", customContent)
+
+		var logs []string
+		err := syncLockscreenPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", env.deps(false))
+		if err != nil {
+			t.Fatalf("syncLockscreenPamConfigWithDeps returned error: %v", err)
+		}
+
+		if got := readFileString(t, env.dankshellPath); got != customContent {
+			t.Fatalf("custom dankshell content changed\ngot:\n%s\nwant:\n%s", got, customContent)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[0], "Custom /etc/pam.d/dankshell found") {
+			t.Fatalf("expected custom-file skip log, got %v", logs)
+		}
+	})
+
+	t.Run("managed dankshell file is rewritten from resolved login stack", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.writePamFile(t, "login", "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n")
+		env.writePamFile(t, "system-auth", "auth sufficient pam_unix.so try_first_pass nullok\nauth sufficient pam_u2f.so cue\naccount required pam_access.so\n")
+		env.writePamFile(t, "dankshell", "#%PAM-1.0\n"+LockscreenPamManagedBlockStart+"\nauth required pam_env.so\n"+LockscreenPamManagedBlockEnd+"\n")
+
+		var logs []string
+		err := syncLockscreenPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", env.deps(false))
+		if err != nil {
+			t.Fatalf("syncLockscreenPamConfigWithDeps returned error: %v", err)
+		}
+
+		output := readFileString(t, env.dankshellPath)
+		for _, want := range []string{
+			LockscreenPamManagedBlockStart,
+			"auth sufficient pam_unix.so try_first_pass nullok",
+			"account required pam_access.so",
+			LockscreenPamManagedBlockEnd,
+		} {
+			if !strings.Contains(output, want) {
+				t.Errorf("missing expected string %q in rewritten dankshell:\n%s", want, output)
+			}
+		}
+		if strings.Contains(output, "pam_u2f") {
+			t.Errorf("rewritten dankshell still contains pam_u2f:\n%s", output)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[len(logs)-1], "Created or updated /etc/pam.d/dankshell") {
+			t.Fatalf("expected success log, got %v", logs)
+		}
+	})
+
+	t.Run("mutable systems fail when login stack cannot be converted safely", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		err := syncLockscreenPamConfigWithDeps(func(string) {}, "", env.deps(false))
+		if err == nil {
+			t.Fatal("expected error when login PAM file is missing, got nil")
+		}
+		if !strings.Contains(err.Error(), "failed to build") {
+			t.Fatalf("error = %q, want substring %q", err.Error(), "failed to build")
+		}
+	})
+
+	t.Run("NixOS remains informational and does not write dankshell", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		var logs []string
+
+		err := syncLockscreenPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", env.deps(true))
+		if err != nil {
+			t.Fatalf("syncLockscreenPamConfigWithDeps returned error on NixOS path: %v", err)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[0], "NixOS detected") || !strings.Contains(logs[0], "/etc/pam.d/login") {
+			t.Fatalf("expected NixOS informational log mentioning /etc/pam.d/login, got %v", logs)
+		}
+		if _, err := os.Stat(env.dankshellPath); !os.IsNotExist(err) {
+			t.Fatalf("expected no dankshell file to be written on NixOS path, stat err = %v", err)
+		}
+	})
+}
+
+func TestSyncLockscreenU2FPamConfigWithDeps(t *testing.T) {
+	t.Parallel()
+
+	t.Run("enabled creates managed file", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		var logs []string
+
+		err := syncLockscreenU2FPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", true, env.deps(false))
+		if err != nil {
+			t.Fatalf("syncLockscreenU2FPamConfigWithDeps returned error: %v", err)
+		}
+
+		got := readFileString(t, env.dankshellU2fPath)
+		if got != buildManagedLockscreenU2FPamContent() {
+			t.Fatalf("unexpected managed dankshell-u2f content:\n%s", got)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[len(logs)-1], "Created or updated /etc/pam.d/dankshell-u2f") {
+			t.Fatalf("expected create log, got %v", logs)
+		}
+	})
+
+	t.Run("enabled rewrites existing managed file", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.writePamFile(t, "dankshell-u2f", "#%PAM-1.0\n"+LockscreenU2FPamManagedBlockStart+"\nauth required pam_u2f.so old\n"+LockscreenU2FPamManagedBlockEnd+"\n")
+
+		if err := syncLockscreenU2FPamConfigWithDeps(func(string) {}, "", true, env.deps(false)); err != nil {
+			t.Fatalf("syncLockscreenU2FPamConfigWithDeps returned error: %v", err)
+		}
+		if got := readFileString(t, env.dankshellU2fPath); got != buildManagedLockscreenU2FPamContent() {
+			t.Fatalf("managed dankshell-u2f was not rewritten:\n%s", got)
+		}
+	})
+
+	t.Run("disabled removes DMS-managed file", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.writePamFile(t, "dankshell-u2f", buildManagedLockscreenU2FPamContent())
+
+		var logs []string
+		err := syncLockscreenU2FPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", false, env.deps(false))
+		if err != nil {
+			t.Fatalf("syncLockscreenU2FPamConfigWithDeps returned error: %v", err)
+		}
+		if _, err := os.Stat(env.dankshellU2fPath); !os.IsNotExist(err) {
+			t.Fatalf("expected managed dankshell-u2f to be removed, stat err = %v", err)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[len(logs)-1], "Removed DMS-managed /etc/pam.d/dankshell-u2f") {
+			t.Fatalf("expected removal log, got %v", logs)
+		}
+	})
+
+	t.Run("disabled preserves custom file", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		customContent := "#%PAM-1.0\nauth required pam_u2f.so cue\n"
+		env.writePamFile(t, "dankshell-u2f", customContent)
+
+		var logs []string
+		err := syncLockscreenU2FPamConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", false, env.deps(false))
+		if err != nil {
+			t.Fatalf("syncLockscreenU2FPamConfigWithDeps returned error: %v", err)
+		}
+		if got := readFileString(t, env.dankshellU2fPath); got != customContent {
+			t.Fatalf("custom dankshell-u2f content changed\ngot:\n%s\nwant:\n%s", got, customContent)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[0], "Custom /etc/pam.d/dankshell-u2f found") {
+			t.Fatalf("expected custom-file log, got %v", logs)
+		}
+	})
+}
+
+func TestSyncGreeterPamConfigWithDeps(t *testing.T) {
+	t.Parallel()
+
+	t.Run("adds managed block for enabled auth modules", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.availableModules["pam_fprintd.so"] = true
+		env.availableModules["pam_u2f.so"] = true
+		env.writePamFile(t, "greetd", "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n")
+		env.writePamFile(t, "system-auth", "auth sufficient pam_unix.so\naccount required pam_unix.so\n")
+
+		settings := AuthSettings{GreeterEnableFprint: true, GreeterEnableU2f: true}
+		if err := syncGreeterPamConfigWithDeps(func(string) {}, "", settings, false, env.deps(false)); err != nil {
+			t.Fatalf("syncGreeterPamConfigWithDeps returned error: %v", err)
+		}
+
+		got := readFileString(t, env.greetdPath)
+		for _, want := range []string{
+			GreeterPamManagedBlockStart,
+			"auth sufficient pam_fprintd.so max-tries=1 timeout=5",
+			"auth sufficient pam_u2f.so cue nouserok timeout=10",
+			GreeterPamManagedBlockEnd,
+		} {
+			if !strings.Contains(got, want) {
+				t.Errorf("missing expected string %q in greetd PAM:\n%s", want, got)
+			}
+		}
+		if strings.Index(got, GreeterPamManagedBlockStart) > strings.Index(got, "auth include system-auth") {
+			t.Fatalf("managed block was not inserted before first auth line:\n%s", got)
+		}
+	})
+
+	t.Run("avoids duplicate fingerprint when included stack already provides it", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.availableModules["pam_fprintd.so"] = true
+		env.fingerprintAvailable = true
+		original := "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n"
+		env.writePamFile(t, "greetd", original)
+		env.writePamFile(t, "system-auth", "auth sufficient pam_fprintd.so max-tries=1\nauth sufficient pam_unix.so\n")
+
+		settings := AuthSettings{GreeterEnableFprint: true}
+		if err := syncGreeterPamConfigWithDeps(func(string) {}, "", settings, false, env.deps(false)); err != nil {
+			t.Fatalf("syncGreeterPamConfigWithDeps returned error: %v", err)
+		}
+
+		got := readFileString(t, env.greetdPath)
+		if got != original {
+			t.Fatalf("greetd PAM changed despite included pam_fprintd stack\ngot:\n%s\nwant:\n%s", got, original)
+		}
+		if strings.Contains(got, GreeterPamManagedBlockStart) {
+			t.Fatalf("managed block should not be inserted when included stack already has pam_fprintd:\n%s", got)
+		}
+	})
+}
+
+func TestRemoveManagedGreeterPamBlockWithDeps(t *testing.T) {
+	t.Parallel()
+
+	env := newPamTestEnv(t)
+	env.writePamFile(t, "greetd", "#%PAM-1.0\n"+
+		legacyGreeterPamFprintComment+"\n"+
+		"auth sufficient pam_fprintd.so max-tries=1\n"+
+		GreeterPamManagedBlockStart+"\n"+
+		"auth sufficient pam_u2f.so cue nouserok timeout=10\n"+
+		GreeterPamManagedBlockEnd+"\n"+
+		"auth include system-auth\n")
+
+	if err := removeManagedGreeterPamBlockWithDeps(func(string) {}, "", env.deps(false)); err != nil {
+		t.Fatalf("removeManagedGreeterPamBlockWithDeps returned error: %v", err)
+	}
+
+	got := readFileString(t, env.greetdPath)
+	if strings.Contains(got, GreeterPamManagedBlockStart) || strings.Contains(got, legacyGreeterPamFprintComment) {
+		t.Fatalf("managed or legacy DMS auth lines remained in greetd PAM:\n%s", got)
+	}
+	if !strings.Contains(got, "auth include system-auth") {
+		t.Fatalf("expected non-DMS greetd auth lines to remain:\n%s", got)
+	}
+}
+
+func TestSyncAuthConfigWithDeps(t *testing.T) {
+	t.Parallel()
+
+	t.Run("creates lockscreen targets and skips greetd when greeter is not installed", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.writeSettings(t, `{"enableU2f":true}`)
+		env.writePamFile(t, "login", "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n")
+		env.writePamFile(t, "system-auth", "auth sufficient pam_unix.so try_first_pass nullok\naccount required pam_access.so\n")
+
+		var logs []string
+		err := syncAuthConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", SyncAuthOptions{HomeDir: env.homeDir}, env.deps(false))
+		if err != nil {
+			t.Fatalf("syncAuthConfigWithDeps returned error: %v", err)
+		}
+
+		if _, err := os.Stat(env.dankshellPath); err != nil {
+			t.Fatalf("expected dankshell to be created: %v", err)
+		}
+		if got := readFileString(t, env.dankshellU2fPath); got != buildManagedLockscreenU2FPamContent() {
+			t.Fatalf("unexpected dankshell-u2f content:\n%s", got)
+		}
+		if len(logs) == 0 || !strings.Contains(logs[len(logs)-1], "greetd not found") {
+			t.Fatalf("expected greetd skip log, got %v", logs)
+		}
+	})
+
+	t.Run("separate greeter and lockscreen toggles are respected", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.availableModules["pam_fprintd.so"] = true
+		env.writeSettings(t, `{"enableU2f":false,"greeterEnableFprint":true,"greeterEnableU2f":false}`)
+		env.writePamFile(t, "login", "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n")
+		env.writePamFile(t, "system-auth", "auth sufficient pam_unix.so try_first_pass nullok\naccount required pam_access.so\n")
+		env.writePamFile(t, "greetd", "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n")
+
+		err := syncAuthConfigWithDeps(func(string) {}, "", SyncAuthOptions{HomeDir: env.homeDir}, env.deps(false))
+		if err != nil {
+			t.Fatalf("syncAuthConfigWithDeps returned error: %v", err)
+		}
+
+		dankshell := readFileString(t, env.dankshellPath)
+		if strings.Contains(dankshell, "pam_fprintd") || strings.Contains(dankshell, "pam_u2f") {
+			t.Fatalf("lockscreen PAM should strip fingerprint and U2F modules:\n%s", dankshell)
+		}
+		if _, err := os.Stat(env.dankshellU2fPath); !os.IsNotExist(err) {
+			t.Fatalf("expected dankshell-u2f to remain absent when enableU2f is false, stat err = %v", err)
+		}
+
+		greetd := readFileString(t, env.greetdPath)
+		if !strings.Contains(greetd, "auth sufficient pam_fprintd.so max-tries=1 timeout=5") {
+			t.Fatalf("expected greetd PAM to receive fingerprint auth block:\n%s", greetd)
+		}
+		if strings.Contains(greetd, "auth sufficient pam_u2f.so cue nouserok timeout=10") {
+			t.Fatalf("did not expect greetd PAM to receive U2F auth block:\n%s", greetd)
+		}
+	})
+
+	t.Run("NixOS remains informational and non-mutating", func(t *testing.T) {
+		t.Parallel()
+
+		env := newPamTestEnv(t)
+		env.availableModules["pam_fprintd.so"] = true
+		env.availableModules["pam_u2f.so"] = true
+		env.writeSettings(t, `{"enableU2f":true,"greeterEnableFprint":true,"greeterEnableU2f":true}`)
+		originalGreetd := "#%PAM-1.0\nauth include system-auth\naccount include system-auth\n"
+		env.writePamFile(t, "greetd", originalGreetd)
+
+		var logs []string
+		err := syncAuthConfigWithDeps(func(msg string) {
+			logs = append(logs, msg)
+		}, "", SyncAuthOptions{HomeDir: env.homeDir}, env.deps(true))
+		if err != nil {
+			t.Fatalf("syncAuthConfigWithDeps returned error: %v", err)
+		}
+
+		if _, err := os.Stat(env.dankshellPath); !os.IsNotExist(err) {
+			t.Fatalf("expected dankshell to remain absent on NixOS path, stat err = %v", err)
+		}
+		if _, err := os.Stat(env.dankshellU2fPath); !os.IsNotExist(err) {
+			t.Fatalf("expected dankshell-u2f to remain absent on NixOS path, stat err = %v", err)
+		}
+		if got := readFileString(t, env.greetdPath); got != originalGreetd {
+			t.Fatalf("expected greetd PAM to remain unchanged on NixOS path\ngot:\n%s\nwant:\n%s", got, originalGreetd)
+		}
+		if len(logs) < 2 || !strings.Contains(strings.Join(logs, "\n"), "NixOS detected") {
+			t.Fatalf("expected informational NixOS logs, got %v", logs)
+		}
+	})
+}

distro/nix/greeter.nix

@@ -139,6 +139,13 @@ in
         '';
       }
     ];
+    # DMS currently relies on /etc/pam.d/login for lock screen password auth on NixOS.
+    # Declare security.pam.services.dankshell only if you want to override that runtime fallback.
+    # U2F and fingerprint are handled separately by DMS — do not add pam_u2f or pam_fprintd here.
+    # security.pam.services.dankshell = {
+    #   # Example: add faillock
+    #   faillock.enable = true;
+    # };
     services.greetd = {
       enable = lib.mkDefault true;
       settings.default_session.command = lib.mkDefault (lib.getExe greeterScript);

quickshell/Common/SettingsData.qml

@@ -1203,13 +1203,23 @@ Singleton {
         Quickshell.execDetached(["sh", "-lc", script]);
     }
 
+    function scheduleAuthApply() {
+        if (isGreeterMode)
+            return;
+        Qt.callLater(() => {
+            Processes.settingsRoot = root;
+            Processes.scheduleAuthApply();
+        });
+    }
+
     readonly property var _hooks: ({
             "applyStoredTheme": applyStoredTheme,
             "regenSystemThemes": regenSystemThemes,
             "updateCompositorLayout": updateCompositorLayout,
             "applyStoredIconTheme": applyStoredIconTheme,
             "updateBarConfigs": updateBarConfigs,
-            "updateCompositorCursor": updateCompositorCursor
+            "updateCompositorCursor": updateCompositorCursor,
+            "scheduleAuthApply": scheduleAuthApply
         })
 
     function set(key, value) {

quickshell/Common/settings/Processes.qml

@@ -4,6 +4,8 @@ pragma ComponentBehavior: Bound
 import QtQuick
 import Quickshell
 import Quickshell.Io
+import qs.Common
+import qs.Services
 
 Singleton {
     id: root
@@ -52,6 +54,14 @@ Singleton {
 
     readonly property var forcedFprintAvailable: envFlag("DMS_FORCE_FPRINT_AVAILABLE")
     readonly property var forcedU2fAvailable: envFlag("DMS_FORCE_U2F_AVAILABLE")
+    property bool authApplyRunning: false
+    property bool authApplyQueued: false
+    property bool authApplyRerunRequested: false
+    property bool authApplyTerminalFallbackFromPrecheck: false
+    property string authApplyStdout: ""
+    property string authApplyStderr: ""
+    property string authApplySudoProbeStderr: ""
+    property string authApplyTerminalFallbackStderr: ""
 
     function detectQtTools() {
         qtToolsDetectionProcess.running = true;
@@ -92,6 +102,50 @@ Singleton {
         pluginSettingsCheckProcess.running = true;
     }
 
+    function scheduleAuthApply() {
+        if (!settingsRoot || settingsRoot.isGreeterMode)
+            return;
+
+        authApplyQueued = true;
+        if (authApplyRunning) {
+            authApplyRerunRequested = true;
+            return;
+        }
+
+        authApplyDebounce.restart();
+    }
+
+    function beginAuthApply() {
+        if (!authApplyQueued || authApplyRunning || !settingsRoot || settingsRoot.isGreeterMode)
+            return;
+
+        authApplyQueued = false;
+        authApplyRerunRequested = false;
+        authApplyStdout = "";
+        authApplyStderr = "";
+        authApplySudoProbeStderr = "";
+        authApplyTerminalFallbackStderr = "";
+        authApplyTerminalFallbackFromPrecheck = false;
+        authApplyRunning = true;
+        authApplySudoProbeProcess.running = true;
+    }
+
+    function launchAuthApplyTerminalFallback(fromPrecheck, details) {
+        authApplyTerminalFallbackFromPrecheck = fromPrecheck;
+        if (details && details !== "")
+            ToastService.showInfo(I18n.tr("Authentication changes need sudo. Opening terminal so you can use password or fingerprint."), details, "", "auth-sync");
+        authApplyTerminalFallbackStderr = "";
+        authApplyTerminalFallbackProcess.running = true;
+    }
+
+    function finishAuthApply() {
+        const shouldRerun = authApplyQueued || authApplyRerunRequested;
+        authApplyRunning = false;
+        authApplyRerunRequested = false;
+        if (shouldRerun)
+            authApplyDebounce.restart();
+    }
+
     function stripPamComment(line) {
         if (!line)
             return "";
@@ -417,6 +471,91 @@ Singleton {
         }
     }
 
+    Timer {
+        id: authApplyDebounce
+        interval: 300
+        repeat: false
+        onTriggered: root.beginAuthApply()
+    }
+
+    property var authApplyProcess: Process {
+        command: ["dms", "auth", "sync", "--yes"]
+        running: false
+
+        stdout: StdioCollector {
+            onStreamFinished: root.authApplyStdout = text || ""
+        }
+
+        stderr: StdioCollector {
+            onStreamFinished: root.authApplyStderr = text || ""
+        }
+
+        onExited: exitCode => {
+            const out = (root.authApplyStdout || "").trim();
+            const err = (root.authApplyStderr || "").trim();
+
+            if (exitCode === 0) {
+                let details = out;
+                if (err !== "")
+                    details = details !== "" ? details + "\n\nstderr:\n" + err : "stderr:\n" + err;
+                ToastService.showInfo(I18n.tr("Authentication changes applied."), details, "", "auth-sync");
+                root.detectAuthCapabilities();
+                root.finishAuthApply();
+                return;
+            }
+
+            let details = "";
+            if (out !== "")
+                details = out;
+            if (err !== "")
+                details = details !== "" ? details + "\n\nstderr:\n" + err : "stderr:\n" + err;
+            ToastService.showWarning(I18n.tr("Background authentication sync failed. Trying terminal mode."), details, "", "auth-sync");
+            root.launchAuthApplyTerminalFallback(false, "");
+        }
+    }
+
+    property var authApplySudoProbeProcess: Process {
+        command: ["sudo", "-n", "true"]
+        running: false
+
+        stderr: StdioCollector {
+            onStreamFinished: root.authApplySudoProbeStderr = text || ""
+        }
+
+        onExited: exitCode => {
+            const err = (root.authApplySudoProbeStderr || "").trim();
+            if (exitCode === 0) {
+                ToastService.showInfo(I18n.tr("Applying authentication changes…"), "", "", "auth-sync");
+                root.authApplyProcess.running = true;
+                return;
+            }
+
+            root.launchAuthApplyTerminalFallback(true, err);
+        }
+    }
+
+    property var authApplyTerminalFallbackProcess: Process {
+        command: ["dms", "auth", "sync", "--terminal", "--yes"]
+        running: false
+
+        stderr: StdioCollector {
+            onStreamFinished: root.authApplyTerminalFallbackStderr = text || ""
+        }
+
+        onExited: exitCode => {
+            if (exitCode === 0) {
+                const message = root.authApplyTerminalFallbackFromPrecheck
+                    ? I18n.tr("Terminal opened. Complete authentication setup there; it will close automatically when done.")
+                    : I18n.tr("Terminal fallback opened. Complete authentication setup there; it will close automatically when done.");
+                ToastService.showInfo(message, "", "", "auth-sync");
+            } else {
+                let details = (root.authApplyTerminalFallbackStderr || "").trim();
+                ToastService.showError(I18n.tr("Terminal fallback failed. Install a supported terminal emulator or run 'dms auth sync' manually.") + " (exit " + exitCode + ")", details, "", "auth-sync");
+            }
+            root.finishAuthApply();
+        }
+    }
+
     FileView {
         id: greetdPamWatcher
         path: "/etc/pam.d/greetd"

quickshell/Common/settings/SettingsSpec.js

@@ -169,8 +169,8 @@ var SPEC = {
     lockDateFormat: { def: "" },
     greeterRememberLastSession: { def: true },
     greeterRememberLastUser: { def: true },
-    greeterEnableFprint: { def: false },
+    greeterEnableFprint: { def: false, onChange: "scheduleAuthApply" },
-    greeterEnableU2f: { def: false },
+    greeterEnableU2f: { def: false, onChange: "scheduleAuthApply" },
     greeterWallpaperPath: { def: "" },
     greeterUse24HourClock: { def: true },
     greeterShowSeconds: { def: false },
@@ -353,7 +353,7 @@ var SPEC = {
     lockScreenShowMediaPlayer: { def: true },
     lockScreenPowerOffMonitorsOnLock: { def: false },
     lockAtStartup: { def: false },
-    enableFprint: { def: false },
+    enableFprint: { def: false, onChange: "scheduleAuthApply" },
     maxFprintTries: { def: 15 },
     fprintdAvailable: { def: false, persist: false },
     lockFingerprintCanEnable: { def: false, persist: false },
@@ -363,7 +363,7 @@ var SPEC = {
     greeterFingerprintReady: { def: false, persist: false },
     greeterFingerprintReason: { def: "probe_failed", persist: false },
     greeterFingerprintSource: { def: "none", persist: false },
-    enableU2f: { def: false },
+    enableU2f: { def: false, onChange: "scheduleAuthApply" },
     u2fMode: { def: "or" },
     u2fAvailable: { def: false, persist: false },
     lockU2fCanEnable: { def: false, persist: false },

quickshell/Modules/Lock/LockScreenContent.qml

@@ -52,6 +52,12 @@ Item {
             return I18n.tr("Touch your security key...");
         if (pam.lockMessage && pam.lockMessage.length > 0)
             return pam.lockMessage;
+        if (root.pamState === "error")
+            return I18n.tr("Authentication error - try again");
+        if (root.pamState === "max")
+            return I18n.tr("Too many attempts - locked out");
+        if (root.pamState === "fail")
+            return I18n.tr("Incorrect password - try again");
         if (pam.fprintState === "error") {
             const detail = (pam.fprint.message || "").trim();
             return detail.length > 0 ? I18n.tr("Fingerprint error: %1").arg(detail) : I18n.tr("Fingerprint error");
@@ -60,12 +66,6 @@ Item {
             return I18n.tr("Maximum fingerprint attempts reached. Please use password.");
         if (pam.fprintState === "fail")
             return I18n.tr("Fingerprint not recognized (%1/%2). Please try again or use password.").arg(pam.fprint.tries).arg(SettingsData.maxFprintTries);
-        if (root.pamState === "error")
-            return I18n.tr("Authentication error - try again");
-        if (root.pamState === "max")
-            return I18n.tr("Too many attempts - locked out");
-        if (root.pamState === "fail")
-            return I18n.tr("Incorrect password - try again");
         return "";
     }
 

quickshell/Modules/Lock/Pam.qml

@@ -91,9 +91,9 @@ Scope {
     }
 
     FileView {
-        id: loginConfigWatcher
+        id: nixosMarker
 
-        path: "/etc/pam.d/login"
+        path: "/etc/NIXOS"
         printErrors: false
     }
 
@@ -108,7 +108,7 @@ Scope {
         id: passwd
 
         config: dankshellConfigWatcher.loaded ? "dankshell" : "login"
-        configDirectory: (dankshellConfigWatcher.loaded || loginConfigWatcher.loaded) ? "/etc/pam.d" : Quickshell.shellDir + "/assets/pam"
+        configDirectory: (dankshellConfigWatcher.loaded || nixosMarker.loaded) ? "/etc/pam.d" : Quickshell.shellDir + "/assets/pam"
 
         onMessageChanged: {
             if (message.startsWith("The account is locked")) {

quickshell/Modules/Settings/GreeterTab.qml

@@ -36,7 +36,7 @@ Item {
 
         switch (reason) {
         case "ready":
-            return SettingsData.greeterEnableFprint ? I18n.tr("Run Sync to apply. Fingerprint-only login may not unlock GNOME Keyring.") : I18n.tr("Only affects DMS-managed PAM. If greetd already includes pam_fprintd, fingerprint stays enabled.");
+            return SettingsData.greeterEnableFprint ? I18n.tr("Authentication changes apply automatically. Fingerprint-only login may not unlock Keyring.") : I18n.tr("Only affects DMS-managed PAM. If greetd already includes pam_fprintd, fingerprint stays enabled.");
         case "missing_enrollment":
             if (SettingsData.greeterEnableFprint)
                 return I18n.tr("Enabled, but no prints are enrolled yet. Enroll fingerprints and run Sync.");
@@ -60,7 +60,7 @@ Item {
 
         switch (reason) {
         case "ready":
-            return SettingsData.greeterEnableU2f ? I18n.tr("Run Sync to apply.") : I18n.tr("Available.");
+            return SettingsData.greeterEnableU2f ? I18n.tr("Authentication changes apply automatically.") : I18n.tr("Available.");
         case "missing_key_registration":
             if (SettingsData.greeterEnableU2f)
                 return I18n.tr("Enabled, but no registered security key was found yet. Register a key and run Sync.");
@@ -448,7 +448,7 @@ Item {
                 settingKey: "greeterStatus"
 
                 StyledText {
-                    text: I18n.tr("Check sync status on demand. Sync copies your theme, settings, PAM config, and wallpaper to the login screen in one step. Must run Sync to apply changes.")
+                    text: I18n.tr("Check sync status on demand. Sync copies your theme, settings, and wallpaper configuration to the login screen. Authentication changes apply automatically.")
                     font.pixelSize: Theme.fontSizeSmall
                     color: Theme.surfaceVariantText
                     width: parent.width
@@ -525,7 +525,7 @@ Item {
                 settingKey: "greeterAuth"
 
                 StyledText {
-                    text: I18n.tr("Enable fingerprint or security key for DMS Greeter. Run Sync to apply and configure PAM.")
+                    text: I18n.tr("Enable fingerprint or security key for DMS Greeter. Authentication changes apply automatically.")
                     font.pixelSize: Theme.fontSizeSmall
                     color: Theme.surfaceVariantText
                     width: parent.width
@@ -754,7 +754,7 @@ Item {
                 settingKey: "greeterDeps"
 
                 StyledText {
-                    text: I18n.tr("DMS greeter needs: greetd, dms-greeter. Fingerprint: fprintd, pam_fprintd. Security keys: pam_u2f. Add your user to the greeter group. Sync checks sudo first and opens a terminal when interactive authentication is required.")
+                    text: I18n.tr("DMS greeter needs: greetd, dms-greeter. Fingerprint: fprintd, pam_fprintd. Security keys: pam_u2f. Add your user to the greeter group. Authentication changes apply automatically and may open a terminal when sudo authentication is required.")
                     font.pixelSize: Theme.fontSizeSmall
                     color: Theme.surfaceVariantText
                     width: parent.width

quickshell/Modules/Settings/LockScreenTab.qml

@@ -15,10 +15,10 @@ Item {
     function lockFingerprintDescription() {
         switch (SettingsData.lockFingerprintReason) {
         case "ready":
-            return I18n.tr("Use fingerprint authentication for the lock screen.");
+            return SettingsData.enableFprint ? I18n.tr("Authentication changes apply automatically.") : I18n.tr("Use fingerprint authentication for the lock screen.");
         case "missing_enrollment":
             if (SettingsData.enableFprint)
-                return I18n.tr("Enabled, but no prints are enrolled yet. Enroll fingerprints to use it.");
+                return I18n.tr("Enabled, but no prints are enrolled yet. Authentication changes apply automatically once you enroll fingerprints.");
             return I18n.tr("Fingerprint reader detected, but no prints are enrolled yet. You can enable this now and enroll later.");
         case "missing_reader":
             return SettingsData.enableFprint ? I18n.tr("Enabled, but no fingerprint reader was detected.") : I18n.tr("No fingerprint reader detected.");
@@ -32,10 +32,10 @@ Item {
     function lockU2fDescription() {
         switch (SettingsData.lockU2fReason) {
         case "ready":
-            return I18n.tr("Use a security key for lock screen authentication.", "lock screen U2F security key setting");
+            return SettingsData.enableU2f ? I18n.tr("Authentication changes apply automatically.") : I18n.tr("Use a security key for lock screen authentication.", "lock screen U2F security key setting");
         case "missing_key_registration":
             if (SettingsData.enableU2f)
-                return I18n.tr("Enabled, but no registered security key was found yet. Register a key or update your U2F config.");
+                return I18n.tr("Enabled, but no registered security key was found yet. Authentication changes apply automatically once your key is registered or your U2F config is updated.");
             return I18n.tr("Security-key support was detected, but no registered key was found yet. You can enable this now and register one later.");
         case "missing_pam_support":
             return I18n.tr("Not available — install or configure pam_u2f.");
@@ -213,6 +213,15 @@ Item {
                     onToggled: checked => SettingsData.set("lockAtStartup", checked)
                 }
 
+                StyledText {
+                    text: I18n.tr("Lock screen authentication changes apply automatically and may open a terminal when sudo authentication is required.")
+                    font.pixelSize: Theme.fontSizeSmall
+                    color: Theme.surfaceVariantText
+                    width: parent.width
+                    wrapMode: Text.Wrap
+                    topPadding: Theme.spacingS
+                }
+
                 SettingsToggleRow {
                     settingKey: "enableFprint"
                     tags: ["lock", "screen", "fingerprint", "authentication", "biometric", "fprint"]