fix(greeter): update NixOS declarative configuration

- Report NixOS greeter state from `var/lib/dms-greeter`
- Allows `dms greeter status` use
- Prevent imperative greeter changes on module-managed NixOS systems
- Preserve immutable-distro sync policy
- Closes #2728

core/cmd/dms/commands_greeter.go

@@ -32,13 +32,14 @@ var greeterCmd = &cobra.Command{
 var (
 	greeterConfigSyncFn = greeter.SyncDMSConfigs
 	sharedAuthSyncFn    = sharedpam.SyncAuthConfig
+	greeterIsNixOSFn    = greeter.IsNixOS
 )
 
 var greeterInstallCmd = &cobra.Command{
 	Use:     "install",
 	Short:   "Install and configure DMS greeter",
 	Long:    "Install greetd and configure it to use DMS as the greeter interface",
-	PreRunE: preRunPrivileged,
+	PreRunE: preRunGreeterMutation,
 	Run: func(cmd *cobra.Command, args []string) {
 		yes, _ := cmd.Flags().GetBool("yes")
 		term, _ := cmd.Flags().GetBool("terminal")
@@ -64,6 +65,9 @@ var greeterSyncCmd = &cobra.Command{
 	Short: "Sync DMS theme and settings with greeter",
 	Long:  "Synchronize your current user's DMS theme, settings, and wallpaper configuration with the login greeter screen. Also updates a per-user cache slot at users/<username>/ for multi-account greeter theme preview.\n\nUse --profile on secondary accounts to sync only your own users/<username>/ slot without sudo or greetd changes.",
 	PreRunE: func(cmd *cobra.Command, args []string) error {
+		if err := rejectNixOSGreeterMutation(cmd); err != nil {
+			return err
+		}
 		profile, _ := cmd.Flags().GetBool("profile")
 		if profile {
 			return nil
@@ -140,7 +144,7 @@ var greeterEnableCmd = &cobra.Command{
 	Use:     "enable",
 	Short:   "Enable DMS greeter in greetd config",
 	Long:    "Configure greetd to use DMS as the greeter",
-	PreRunE: preRunPrivileged,
+	PreRunE: preRunGreeterMutation,
 	Run: func(cmd *cobra.Command, args []string) {
 		yes, _ := cmd.Flags().GetBool("yes")
 		term, _ := cmd.Flags().GetBool("terminal")
@@ -176,7 +180,7 @@ var greeterUninstallCmd = &cobra.Command{
 	Use:     "uninstall",
 	Short:   "Remove DMS greeter configuration and restore previous display manager",
 	Long:    "Disable greetd, remove DMS managed configs, and restore the system to its pre-DMS-greeter state",
-	PreRunE: preRunPrivileged,
+	PreRunE: preRunGreeterMutation,
 	Run: func(cmd *cobra.Command, args []string) {
 		yes, _ := cmd.Flags().GetBool("yes")
 		term, _ := cmd.Flags().GetBool("terminal")
@@ -206,6 +210,21 @@ func init() {
 	greeterUninstallCmd.Flags().BoolP("terminal", "t", false, "Run in a new terminal (for entering sudo password)")
 }
 
+func rejectNixOSGreeterMutation(cmd *cobra.Command) error {
+	if !greeterIsNixOSFn() {
+		return nil
+	}
+
+	return fmt.Errorf("dms %s is disabled on NixOS because the greeter is managed declaratively\nConfigure the DMS greeter in your NixOS module, then apply the change with your normal nixos-rebuild workflow", normalizeCommandSpec(cmd.CommandPath()))
+}
+
+func preRunGreeterMutation(cmd *cobra.Command, args []string) error {
+	if err := rejectNixOSGreeterMutation(cmd); err != nil {
+		return err
+	}
+	return preRunPrivileged(cmd, args)
+}
+
 func syncGreeterConfigsAndAuth(dmsPath, compositor string, logFunc func(string), options sharedpam.SyncAuthOptions, beforeAuth func()) error {
 	if err := greeterConfigSyncFn(dmsPath, compositor, logFunc, ""); err != nil {
 		return err
@@ -1415,24 +1434,36 @@ func readDefaultSessionCommand(configPath string) string {
 	return ""
 }
 
-func extractGreeterCacheDirFromCommand(command string) string {
-	if command == "" {
-		return greeter.GreeterCacheDir
-	}
+func explicitGreeterCacheDirFromCommand(command string) (string, bool) {
 	tokens := strings.Fields(command)
 	for i := 0; i < len(tokens); i++ {
 		token := strings.Trim(tokens[i], "\"")
 		if token == "--cache-dir" && i+1 < len(tokens) {
-			return strings.Trim(tokens[i+1], "\"")
+			value := strings.Trim(tokens[i+1], "\"")
+			if value != "" {
+				return value, true
+			}
 		}
 		if strings.HasPrefix(token, "--cache-dir=") {
 			value := strings.TrimPrefix(token, "--cache-dir=")
 			value = strings.Trim(value, "\"")
 			if value != "" {
-				return value
+				return value, true
 			}
 		}
 	}
+	return "", false
+}
+
+const nixOSGreeterStateDir = "/var/lib/dms-greeter"
+
+func greeterStatusStateDir(command string, isNixOS bool) string {
+	if cacheDir, ok := explicitGreeterCacheDirFromCommand(command); ok {
+		return cacheDir
+	}
+	if isNixOS {
+		return nixOSGreeterStateDir
+	}
 	return greeter.GreeterCacheDir
 }
 
@@ -1569,6 +1600,10 @@ func checkGreeterStatus() error {
 	fmt.Println("=== DMS Greeter Status ===")
 	fmt.Println()
 
+	if greeterIsNixOSFn() {
+		return checkNixOSGreeterStatus()
+	}
+
 	homeDir, err := os.UserHomeDir()
 	if err != nil {
 		return fmt.Errorf("failed to get user home directory: %w", err)
@@ -1632,7 +1667,7 @@ func checkGreeterStatus() error {
 		fmt.Println("    Run 'dms greeter sync' to set up group membership and permissions")
 	}
 
-	cacheDir := extractGreeterCacheDirFromCommand(configuredCommand)
+	cacheDir := greeterStatusStateDir(configuredCommand, false)
 	fmt.Println("\nGreeter Cache Directory:")
 	fmt.Printf("  Effective cache dir: %s\n", cacheDir)
 	if cacheDir != greeter.GreeterCacheDir {
@@ -1895,6 +1930,85 @@ func checkGreeterStatus() error {
 	return nil
 }
 
+func checkNixOSGreeterStatus() error {
+	const configPath = "/etc/greetd/config.toml"
+
+	configuredCommand := readDefaultSessionCommand(configPath)
+	allGood := true
+
+	fmt.Println("Greeter Configuration:")
+	switch {
+	case strings.Contains(configuredCommand, "dms-greeter"):
+		fmt.Println("  ✓ DMS greeter command found")
+		if wrapper := extractGreeterWrapperFromCommand(configuredCommand); wrapper != "" {
+			fmt.Printf("  Wrapper: %s\n", wrapper)
+		}
+	case configuredCommand != "":
+		fmt.Println("  ⚠ greetd default session does not reference dms-greeter")
+		allGood = false
+	default:
+		fmt.Printf("  ℹ No readable DMS command found in %s\n", configPath)
+	}
+	fmt.Println("  ℹ NixOS manages greeter configuration declaratively; apply changes through your NixOS module.")
+
+	stateDir := greeterStatusStateDir(configuredCommand, true)
+	fmt.Println("\nGreeter State Directory:")
+	fmt.Printf("  Effective state dir: %s\n", stateDir)
+	if stateDir == nixOSGreeterStateDir {
+		fmt.Println("  ✓ Using the NixOS module state path")
+	}
+	if stat, err := os.Stat(stateDir); err == nil && stat.IsDir() {
+		fmt.Printf("  ✓ %s exists\n", stateDir)
+	} else if os.IsNotExist(err) {
+		fmt.Printf("  ✗ %s not found\n", stateDir)
+		fmt.Println("    Rebuild your NixOS configuration after enabling the DMS greeter module.")
+		allGood = false
+	} else if err != nil {
+		fmt.Printf("  ✗ Could not inspect %s: %v\n", stateDir, err)
+		allGood = false
+	} else {
+		fmt.Printf("  ✗ %s is not a directory\n", stateDir)
+		allGood = false
+	}
+
+	fmt.Println("\nDeclarative Configuration Files:")
+	configFiles := []struct {
+		name string
+		path string
+	}{
+		{name: "Settings", path: filepath.Join(stateDir, "settings.json")},
+		{name: "Session state", path: filepath.Join(stateDir, "session.json")},
+		{name: "Color theme", path: filepath.Join(stateDir, "colors.json")},
+	}
+	for _, configFile := range configFiles {
+		if stat, err := os.Stat(configFile.path); err == nil && !stat.IsDir() {
+			fmt.Printf("  ✓ %s: %s\n", configFile.name, configFile.path)
+		} else if os.IsNotExist(err) {
+			fmt.Printf("  ℹ %s not present (optional; configure configHome/configFiles in the NixOS module)\n", configFile.name)
+		} else if err != nil {
+			fmt.Printf("  ⚠ %s could not be inspected: %v\n", configFile.name, err)
+		} else {
+			fmt.Printf("  ⚠ %s path is not a regular file: %s\n", configFile.name, configFile.path)
+		}
+	}
+
+	fmt.Println("\nGroup Membership:")
+	fmt.Println("  ℹ User group membership is managed by NixOS and is not required for declarative theme copies.")
+
+	fmt.Println("\nGreeter PAM Authentication:")
+	fmt.Println("  ℹ PAM is managed by NixOS modules.")
+	fmt.Println("    Configure fingerprint/U2F through security.pam.services.greetd.")
+
+	fmt.Println()
+	if allGood {
+		fmt.Println("✓ NixOS greeter state looks healthy and is managed declaratively.")
+	} else {
+		fmt.Println("⚠ Some issues detected. Update the DMS greeter module and rebuild NixOS; do not run 'dms greeter sync'.")
+	}
+
+	return nil
+}
+
 func recentAppArmorGreeterDenials(sampleLimit int) (int, []string, error) {
 	if sampleLimit <= 0 {
 		sampleLimit = 3

core/cmd/dms/commands_greeter_test.go

@@ -3,9 +3,11 @@ package main
 import (
 	"errors"
 	"reflect"
+	"strings"
 	"testing"
 
 	sharedpam "github.com/AvengeMedia/DankMaterialShell/core/internal/pam"
+	"github.com/spf13/cobra"
 )
 
 func TestSyncGreeterConfigsAndAuthDelegatesSharedAuth(t *testing.T) {
@@ -85,3 +87,57 @@ func TestSyncGreeterConfigsAndAuthStopsOnConfigError(t *testing.T) {
 		t.Fatal("expected auth sync not to run after config sync failure")
 	}
 }
+
+func TestGreeterStatusStateDirUsesNixOSDefault(t *testing.T) {
+	if got := greeterStatusStateDir("", true); got != nixOSGreeterStateDir {
+		t.Fatalf("greeterStatusStateDir() = %q, want %q", got, nixOSGreeterStateDir)
+	}
+}
+
+func TestGreeterStatusStateDirHonorsExplicitOverrideOnNixOS(t *testing.T) {
+	command := "dms-greeter --cache-dir /srv/dms-greeter --command niri"
+	if got := greeterStatusStateDir(command, true); got != "/srv/dms-greeter" {
+		t.Fatalf("greeterStatusStateDir() = %q, want %q", got, "/srv/dms-greeter")
+	}
+}
+
+func TestRejectNixOSGreeterMutationBlocksImperativeCommands(t *testing.T) {
+	origGreeterIsNixOSFn := greeterIsNixOSFn
+	greeterIsNixOSFn = func() bool { return true }
+	t.Cleanup(func() {
+		greeterIsNixOSFn = origGreeterIsNixOSFn
+	})
+
+	for _, commandName := range []string{"install", "enable", "sync", "uninstall"} {
+		t.Run(commandName, func(t *testing.T) {
+			root := &cobra.Command{Use: "dms"}
+			greeterCommand := &cobra.Command{Use: "greeter"}
+			mutationCommand := &cobra.Command{Use: commandName}
+			root.AddCommand(greeterCommand)
+			greeterCommand.AddCommand(mutationCommand)
+
+			err := rejectNixOSGreeterMutation(mutationCommand)
+			if err == nil {
+				t.Fatalf("expected NixOS greeter %s to be rejected", commandName)
+			}
+			if !strings.Contains(err.Error(), "dms greeter "+commandName+" is disabled on NixOS") {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if strings.Contains(err.Error(), "/var/cache/dms-greeter") {
+				t.Fatalf("NixOS remediation should not recommend the non-NixOS cache path: %v", err)
+			}
+		})
+	}
+}
+
+func TestRejectNixOSGreeterMutationAllowsOtherDistros(t *testing.T) {
+	origGreeterIsNixOSFn := greeterIsNixOSFn
+	greeterIsNixOSFn = func() bool { return false }
+	t.Cleanup(func() {
+		greeterIsNixOSFn = origGreeterIsNixOSFn
+	})
+
+	if err := rejectNixOSGreeterMutation(&cobra.Command{Use: "sync"}); err != nil {
+		t.Fatalf("expected non-NixOS greeter command to be allowed, got %v", err)
+	}
+}

core/cmd/dms/immutable_policy_test.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestDefaultImmutablePolicyAllowsSyncButBlocksEnable(t *testing.T) {
+	var policyFile cliPolicyFile
+	if err := json.Unmarshal(defaultCLIPolicyJSON, &policyFile); err != nil {
+		t.Fatalf("failed to parse embedded CLI policy: %v", err)
+	}
+	if policyFile.BlockedCommands == nil {
+		t.Fatal("embedded CLI policy has no blocked_commands")
+	}
+
+	blocked := normalizeBlockedCommands(*policyFile.BlockedCommands)
+	if !commandBlockedByPolicy("greeter enable", blocked) {
+		t.Fatal("expected greeter enable to remain blocked on immutable/image-based systems")
+	}
+	if commandBlockedByPolicy("greeter sync", blocked) {
+		t.Fatal("expected greeter sync to remain available on immutable/image-based systems")
+	}
+}