feat: Multi-Monitor-Support — Wallpaper auf Sekundärmonitoren

- WallpaperWindow für Sekundärmonitore (nur Hintergrundbild)
- GreeterWindow bekommt bg_path als Parameter
- resolve_wallpaper_path() aus config.py extrahiert (wiederverwendbar)
- main.py: Monitor-Enumeration, Layer-Shell pro Monitor
- Keyboard-Exclusive nur auf dem primären Monitor
- CSS: ungültige max-width/max-height Properties entfernt

CLAUDE.md

@@ -42,5 +42,10 @@ uv run moongreet
 - `sessions.py` — Wayland/X11 Sessions aus .desktop Files
 - `power.py` — Reboot/Shutdown via loginctl
 - `i18n.py` — Locale-Erkennung (LANG / /etc/locale.conf) und String-Tabellen (DE/EN)
-- `greeter.py` — GTK4 UI (Overlay-Layout), Faillock-Warnung nach 2 Fehlversuchen
-- `main.py` — Entry Point, GTK App, Layer Shell Setup
+- `greeter.py` — GTK4 UI (Overlay-Layout), Faillock-Warnung nach 2 Fehlversuchen, WallpaperWindow für Sekundärmonitore
+- `main.py` — Entry Point, GTK App, Layer Shell Setup, Multi-Monitor-Orchestrierung
+
+## Design Decisions
+
+- **Synchrones I/O im GTK-Konstruktor**: `load_config`, `load_strings`, `get_users` und `get_sessions` laufen synchron in `GreeterWindow.__init__`. Async Loading mit Placeholder-UI wäre möglich, erhöht aber die Komplexität erheblich. Der Greeter startet 1x pro Boot auf lokaler Hardware — die Daten sind klein (passwd, locale.conf, wenige .desktop-Files), die Latenz im Normalfall vernachlässigbar.
+- **Synchrones Avatar-Decoding**: `GdkPixbuf.Pixbuf.new_from_file_at_scale` läuft synchron auf dem Main Thread. Bei großen Bildern als `.face`-Datei kann die UI kurz stocken. Der Avatar-Cache (`_avatar_cache`) federt das nach dem ersten Laden ab. Async Decoding per Worker-Thread + `GLib.idle_add` wäre die Alternative, rechtfertigt aber den Aufwand nicht für einen Single-User-Greeter.

config/moongreet.toml

@@ -4,7 +4,3 @@
 [appearance]
 # Absolute path to wallpaper image
 background = "/usr/share/backgrounds/wallpaper.jpg"
-
-[behavior]
-# show_user_list = true
-# default_session = "Hyprland"

src/moongreet/config.py

@@ -1,8 +1,10 @@
 # ABOUTME: Configuration loading from moongreet.toml.
-# ABOUTME: Parses appearance and behavior settings for the greeter.
+# ABOUTME: Parses appearance and behavior settings with wallpaper path resolution.
 
 import tomllib
+from contextlib import AbstractContextManager
 from dataclasses import dataclass
+from importlib.resources import as_file, files
 from pathlib import Path
 
 DEFAULT_CONFIG_PATHS = [
@@ -33,8 +35,11 @@ def load_config(config_path: Path | None = None) -> Config:
     if not config_path.exists():
         return Config()
 
-    with open(config_path, "rb") as f:
-        data = tomllib.load(f)
+    try:
+        with open(config_path, "rb") as f:
+            data = tomllib.load(f)
+    except (tomllib.TOMLDecodeError, OSError):
+        return Config()
 
     config = Config()
     appearance = data.get("appearance", {})
@@ -47,3 +52,24 @@ def load_config(config_path: Path | None = None) -> Config:
         config.background = bg_path
 
     return config
+
+
+_PACKAGE_DATA = files("moongreet") / "data"
+_DEFAULT_WALLPAPER_PATH = _PACKAGE_DATA / "wallpaper.jpg"
+
+
+def resolve_wallpaper_path(
+    config: Config,
+) -> tuple[Path, AbstractContextManager | None]:
+    """Resolve the wallpaper path from config or fall back to the package default.
+
+    Returns (path, context_manager). The context_manager is non-None when a
+    package resource was extracted to a temporary file — the caller must keep
+    it alive and call __exit__ when done.
+    """
+    if config.background and config.background.exists():
+        return config.background, None
+
+    ctx = as_file(_DEFAULT_WALLPAPER_PATH)
+    path = ctx.__enter__()
+    return path, ctx

src/moongreet/greeter.py

@@ -1,11 +1,15 @@
 # ABOUTME: Main greeter window — builds the GTK4 UI layout for the Moongreet greeter.
 # ABOUTME: Handles user selection, session choice, password entry, and power actions.
 
+import logging
 import os
+import re
 import shlex
+import shutil
 import socket
 import stat
 import subprocess
+import threading
 from importlib.resources import files
 from pathlib import Path
 
@@ -14,18 +18,21 @@ gi.require_version("Gtk", "4.0")
 gi.require_version("Gdk", "4.0")
 from gi.repository import Gtk, Gdk, GLib, GdkPixbuf
 
-from moongreet.config import load_config
+from moongreet.config import load_config, resolve_wallpaper_path
 from moongreet.i18n import load_strings, Strings
 from moongreet.ipc import create_session, post_auth_response, start_session, cancel_session
 from moongreet.users import User, get_users, get_avatar_path, get_user_gtk_theme
 from moongreet.sessions import Session, get_sessions
 from moongreet.power import reboot, shutdown
 
+logger = logging.getLogger(__name__)
+
 LAST_USER_PATH = Path("/var/cache/moongreet/last-user")
 FAILLOCK_MAX_ATTEMPTS = 3
+VALID_USERNAME = re.compile(r"^[a-zA-Z0-9_.-]+$")
+MAX_USERNAME_LENGTH = 256
 PACKAGE_DATA = files("moongreet") / "data"
 DEFAULT_AVATAR_PATH = PACKAGE_DATA / "default-avatar.svg"
-DEFAULT_WALLPAPER_PATH = PACKAGE_DATA / "wallpaper.jpg"
 AVATAR_SIZE = 128
 
 
@@ -41,10 +48,35 @@ def faillock_warning(attempt_count: int, strings: Strings | None = None) -> str
     return None
 
 
+def _build_wallpaper_widget(bg_path: Path | None) -> Gtk.Widget:
+    """Create a wallpaper widget that fills the available space."""
+    if bg_path and bg_path.exists():
+        background = Gtk.Picture()
+        background.set_filename(str(bg_path))
+        background.set_content_fit(Gtk.ContentFit.COVER)
+        background.set_hexpand(True)
+        background.set_vexpand(True)
+        return background
+    background = Gtk.Box()
+    background.set_hexpand(True)
+    background.set_vexpand(True)
+    return background
+
+
+class WallpaperWindow(Gtk.ApplicationWindow):
+    """A window that shows only the wallpaper — used for secondary monitors."""
+
+    def __init__(self, bg_path: Path | None = None, **kwargs) -> None:
+        super().__init__(**kwargs)
+        self.add_css_class("greeter")
+        self.set_default_size(1920, 1080)
+        self.set_child(_build_wallpaper_widget(bg_path))
+
+
 class GreeterWindow(Gtk.ApplicationWindow):
     """The main greeter window with login UI."""
 
-    def __init__(self, **kwargs) -> None:
+    def __init__(self, bg_path: Path | None = None, **kwargs) -> None:
         super().__init__(**kwargs)
         self.add_css_class("greeter")
         self.set_default_size(1920, 1080)
@@ -55,13 +87,26 @@ class GreeterWindow(Gtk.ApplicationWindow):
         self._sessions = get_sessions()
         self._selected_user: User | None = None
         self._greetd_sock: socket.socket | None = None
+        self._greetd_sock_lock = threading.Lock()
         self._default_avatar_pixbuf: GdkPixbuf.Pixbuf | None = None
         self._avatar_cache: dict[str, GdkPixbuf.Pixbuf] = {}
         self._failed_attempts: dict[str, int] = {}
+        self._bg_path = bg_path
 
         self._build_ui()
-        self._select_initial_user()
         self._setup_keyboard_navigation()
+        # Defer initial user selection until the window is realized,
+        # so get_color() returns the actual theme foreground for SVG tinting
+        self.connect("realize", self._on_realize)
+
+    def _on_realize(self, widget: Gtk.Widget) -> None:
+        """Called when the window is realized — select initial user.
+
+        Deferred from __init__ so get_color() returns actual theme values
+        for SVG tinting. Uses idle_add so the first frame renders before
+        avatar loading blocks the main loop.
+        """
+        GLib.idle_add(self._select_initial_user)
 
     def _build_ui(self) -> None:
         """Build the complete greeter UI layout."""
@@ -69,21 +114,8 @@ class GreeterWindow(Gtk.ApplicationWindow):
         overlay = Gtk.Overlay()
         self.set_child(overlay)
 
-        # Background wallpaper (blurred and darkened)
-        bg_path = self._config.background
-        if not bg_path or not bg_path.exists():
-            bg_path = Path(str(DEFAULT_WALLPAPER_PATH))
-        if bg_path.exists():
-            background = Gtk.Picture()
-            background.set_filename(str(bg_path))
-            background.set_content_fit(Gtk.ContentFit.COVER)
-            background.set_hexpand(True)
-            background.set_vexpand(True)
-        else:
-            background = Gtk.Box()
-            background.set_hexpand(True)
-            background.set_vexpand(True)
-        overlay.set_child(background)
+        # Background wallpaper
+        overlay.set_child(_build_wallpaper_widget(self._bg_path))
 
         # Main layout: 3 rows (top spacer, center login, bottom bar)
         main_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
@@ -249,10 +281,10 @@ class GreeterWindow(Gtk.ApplicationWindow):
             )
             if avatar_path and avatar_path.exists():
                 self._set_avatar_from_file(avatar_path, user.username)
-            elif DEFAULT_AVATAR_PATH.exists():
-                self._set_default_avatar()
             else:
-                self._avatar_image.set_from_icon_name("avatar-default-symbolic")
+                # Default avatar — _set_default_avatar uses Traversable.read_text()
+                # which works in ZIP wheels too, no exists() check needed
+                self._set_default_avatar()
 
         # Apply user's GTK theme if available
         self._apply_user_theme(user)
@@ -372,12 +404,18 @@ class GreeterWindow(Gtk.ApplicationWindow):
 
     def _close_greetd_sock(self) -> None:
         """Close the greetd socket and reset the reference."""
-        if self._greetd_sock:
-            try:
-                self._greetd_sock.close()
-            except OSError:
-                pass
-            self._greetd_sock = None
+        with self._greetd_sock_lock:
+            if self._greetd_sock:
+                try:
+                    self._greetd_sock.close()
+                except OSError:
+                    pass
+                self._greetd_sock = None
+
+    def _set_login_sensitive(self, sensitive: bool) -> None:
+        """Enable or disable login controls during authentication."""
+        self._password_entry.set_sensitive(sensitive)
+        self._session_dropdown.set_sensitive(sensitive)
 
     def _attempt_login(self, user: User, password: str, session: Session) -> None:
         """Attempt to authenticate and start a session via greetd IPC."""
@@ -389,18 +427,29 @@ class GreeterWindow(Gtk.ApplicationWindow):
         if not self._validate_greetd_sock(sock_path):
             return
 
+        # Disable UI while authenticating — the IPC runs in a background thread
+        self._set_login_sensitive(False)
+        thread = threading.Thread(
+            target=self._login_worker,
+            args=(user, password, session, sock_path),
+            daemon=True,
+        )
+        thread.start()
+
+    def _login_worker(self, user: User, password: str, session: Session, sock_path: str) -> None:
+        """Run greetd IPC in a background thread to avoid blocking the GTK main loop."""
         try:
             sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
             sock.settimeout(10.0)
             sock.connect(sock_path)
-            self._greetd_sock = sock
+            with self._greetd_sock_lock:
+                self._greetd_sock = sock
 
             # Step 1: Create session
             response = create_session(sock, user.username)
 
             if response.get("type") == "error":
-                self._show_greetd_error(response, self._strings.auth_failed)
-                self._close_greetd_sock()
+                GLib.idle_add(self._on_login_error, response, self._strings.auth_failed)
                 return
 
             # Step 2: Send password if auth message received
@@ -409,56 +458,71 @@ class GreeterWindow(Gtk.ApplicationWindow):
 
                 if response.get("type") == "error":
                     self._failed_attempts[user.username] = self._failed_attempts.get(user.username, 0) + 1
-                    self._show_greetd_error(response, self._strings.wrong_password)
                     warning = faillock_warning(self._failed_attempts[user.username], self._strings)
-                    if warning:
-                        current = self._error_label.get_text()
-                        self._error_label.set_text(f"{current}\n{warning}")
-                    self._close_greetd_sock()
+                    GLib.idle_add(self._on_login_auth_error, response, warning)
                     return
 
                 if response.get("type") == "auth_message":
                     # Multi-stage auth (e.g. TOTP) is not supported
                     cancel_session(sock)
-                    self._close_greetd_sock()
-                    self._show_error(self._strings.multi_stage_unsupported)
+                    GLib.idle_add(self._on_login_error, None, self._strings.multi_stage_unsupported)
                     return
 
             # Step 3: Start session
             if response.get("type") == "success":
                 cmd = shlex.split(session.exec_cmd)
-                if not cmd or not Path(cmd[0]).is_absolute():
-                    self._show_error(self._strings.invalid_session_command)
+                if not cmd or not shutil.which(cmd[0]):
                     cancel_session(sock)
-                    self._close_greetd_sock()
+                    GLib.idle_add(self._on_login_error, None, self._strings.invalid_session_command)
                     return
                 response = start_session(sock, cmd)
 
                 if response.get("type") == "success":
                     self._save_last_user(user.username)
                     self._close_greetd_sock()
-                    self.get_application().quit()
+                    GLib.idle_add(self.get_application().quit)
                     return
                 else:
-                    self._show_greetd_error(response, self._strings.session_start_failed)
+                    GLib.idle_add(self._on_login_error, response, self._strings.session_start_failed)
 
             self._close_greetd_sock()
 
         except ConnectionError as e:
+            logger.error("greetd connection error: %s", e)
             self._close_greetd_sock()
-            self._show_error(self._strings.connection_error.format(error=e))
-        except OSError as e:
+            GLib.idle_add(self._on_login_error, None, self._strings.connection_error)
+        except (OSError, ValueError) as e:
+            logger.error("greetd socket error: %s", e)
             self._close_greetd_sock()
-            self._show_error(self._strings.socket_error.format(error=e))
+            GLib.idle_add(self._on_login_error, None, self._strings.socket_error)
+
+    def _on_login_error(self, response: dict | None, message: str) -> None:
+        """Handle login error on the GTK main thread."""
+        if response:
+            self._show_greetd_error(response, message)
+        else:
+            self._show_error(message)
+        self._close_greetd_sock()
+        self._set_login_sensitive(True)
+
+    def _on_login_auth_error(self, response: dict, warning: str | None) -> None:
+        """Handle authentication failure with optional faillock warning on the GTK main thread."""
+        self._show_greetd_error(response, self._strings.wrong_password)
+        if warning:
+            current = self._error_label.get_text()
+            self._error_label.set_text(f"{current}\n{warning}")
+        self._close_greetd_sock()
+        self._set_login_sensitive(True)
 
     def _cancel_pending_session(self) -> None:
         """Cancel any in-progress greetd session."""
-        if self._greetd_sock:
-            try:
-                cancel_session(self._greetd_sock)
-            except (ConnectionError, OSError):
-                pass
-            self._close_greetd_sock()
+        with self._greetd_sock_lock:
+            if self._greetd_sock:
+                try:
+                    cancel_session(self._greetd_sock)
+                except (ConnectionError, OSError):
+                    pass
+        self._close_greetd_sock()
 
     def _get_selected_session(self) -> Session | None:
         """Get the currently selected session from the dropdown."""
@@ -505,9 +569,12 @@ class GreeterWindow(Gtk.ApplicationWindow):
         """Load the last logged-in username from cache."""
         if LAST_USER_PATH.exists():
             try:
-                return LAST_USER_PATH.read_text().strip()
+                username = LAST_USER_PATH.read_text().strip()
             except OSError:
                 return None
+            if len(username) > MAX_USERNAME_LENGTH or not VALID_USERNAME.match(username):
+                return None
+            return username
         return None
 
     @staticmethod

src/moongreet/i18n.py

@@ -31,9 +31,11 @@ class Strings:
     reboot_failed: str
     shutdown_failed: str
 
-    # Templates (use .format())
+    # Error messages (continued)
     connection_error: str
     socket_error: str
+
+    # Templates (use .format())
     faillock_attempts_remaining: str
     faillock_locked: str
 
@@ -54,8 +56,8 @@ _STRINGS_DE = Strings(
     session_start_failed="Session konnte nicht gestartet werden",
     reboot_failed="Neustart fehlgeschlagen",
     shutdown_failed="Herunterfahren fehlgeschlagen",
-    connection_error="Verbindungsfehler: {error}",
-    socket_error="Socket-Fehler: {error}",
+    connection_error="Verbindungsfehler",
+    socket_error="Socket-Fehler",
     faillock_attempts_remaining="Noch {n} Versuch(e) vor Kontosperrung!",
     faillock_locked="Konto ist möglicherweise gesperrt",
 )
@@ -76,8 +78,8 @@ _STRINGS_EN = Strings(
     session_start_failed="Failed to start session",
     reboot_failed="Reboot failed",
     shutdown_failed="Shutdown failed",
-    connection_error="Connection error: {error}",
-    socket_error="Socket error: {error}",
+    connection_error="Connection error",
+    socket_error="Socket error",
     faillock_attempts_remaining="{n} attempt(s) remaining before lockout!",
     faillock_locked="Account may be locked",
 )
@@ -102,7 +104,9 @@ def detect_locale(locale_conf_path: Path = DEFAULT_LOCALE_CONF) -> str:
         return "en"
 
     # Extract language prefix: "de_DE.UTF-8" → "de"
-    lang = lang.split("_")[0].split(".")[0]
+    lang = lang.split("_")[0].split(".")[0].lower()
+    if not lang.isalpha():
+        return "en"
     return lang
 
 

src/moongreet/main.py

@@ -1,6 +1,7 @@
 # ABOUTME: Entry point for Moongreet — sets up GTK Application and Layer Shell.
-# ABOUTME: Handles CLI invocation and initializes the greeter window.
+# ABOUTME: Handles multi-monitor setup: login UI on primary, wallpaper on secondary monitors.
 
+import logging
 import sys
 from importlib.resources import files
 
@@ -9,7 +10,8 @@ gi.require_version("Gtk", "4.0")
 gi.require_version("Gdk", "4.0")
 from gi.repository import Gtk, Gdk
 
-from moongreet.greeter import GreeterWindow
+from moongreet.config import load_config, resolve_wallpaper_path
+from moongreet.greeter import GreeterWindow, WallpaperWindow
 
 # gtk4-layer-shell is optional for development/testing
 try:
@@ -19,23 +21,65 @@ try:
 except (ValueError, ImportError):
     HAS_LAYER_SHELL = False
 
+logger = logging.getLogger(__name__)
+
 
 class MoongreetApp(Gtk.Application):
     """GTK Application for the Moongreet greeter."""
 
     def __init__(self) -> None:
         super().__init__(application_id="dev.moonarch.moongreet")
+        self._wallpaper_ctx = None
+        self._secondary_windows: list[WallpaperWindow] = []
 
     def do_activate(self) -> None:
-        """Create and present the greeter window."""
+        """Create and present greeter windows on all monitors."""
         self._register_icons()
         self._load_css()
-        window = GreeterWindow(application=self)
 
+        # Resolve wallpaper once, share across all windows
+        config = load_config()
+        bg_path, self._wallpaper_ctx = resolve_wallpaper_path(config)
+
+        display = Gdk.Display.get_default()
+        monitors = display.get_monitors()
+        primary_monitor = None
+
+        # Find primary monitor — fall back to first available
+        for i in range(monitors.get_n_items()):
+            monitor = monitors.get_item(i)
+            if hasattr(monitor, 'is_primary') and monitor.is_primary():
+                primary_monitor = monitor
+                break
+        if primary_monitor is None and monitors.get_n_items() > 0:
+            primary_monitor = monitors.get_item(0)
+
+        # Main greeter window (login UI) on primary monitor
+        greeter = GreeterWindow(bg_path=bg_path, application=self)
         if HAS_LAYER_SHELL:
-            self._setup_layer_shell(window)
+            self._setup_layer_shell(greeter, keyboard=True)
+            if primary_monitor is not None:
+                Gtk4LayerShell.set_monitor(greeter, primary_monitor)
+        greeter.present()
 
-        window.present()
+        # Wallpaper-only windows on secondary monitors
+        for i in range(monitors.get_n_items()):
+            monitor = monitors.get_item(i)
+            if monitor == primary_monitor:
+                continue
+            wallpaper_win = WallpaperWindow(bg_path=bg_path, application=self)
+            if HAS_LAYER_SHELL:
+                self._setup_layer_shell(wallpaper_win, keyboard=False)
+                Gtk4LayerShell.set_monitor(wallpaper_win, monitor)
+            wallpaper_win.present()
+            self._secondary_windows.append(wallpaper_win)
+
+    def do_shutdown(self) -> None:
+        """Clean up wallpaper context manager on exit."""
+        if self._wallpaper_ctx is not None:
+            self._wallpaper_ctx.__exit__(None, None, None)
+            self._wallpaper_ctx = None
+        Gtk.Application.do_shutdown(self)
 
     def _register_icons(self) -> None:
         """Register custom icons from the package data/icons directory."""
@@ -54,13 +98,14 @@ class MoongreetApp(Gtk.Application):
             Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION,
         )
 
-    def _setup_layer_shell(self, window: Gtk.Window) -> None:
-        """Configure gtk4-layer-shell for fullscreen greeter display."""
+    def _setup_layer_shell(self, window: Gtk.Window, keyboard: bool = False) -> None:
+        """Configure gtk4-layer-shell for fullscreen display."""
         Gtk4LayerShell.init_for_window(window)
         Gtk4LayerShell.set_layer(window, Gtk4LayerShell.Layer.TOP)
-        Gtk4LayerShell.set_keyboard_mode(
-            window, Gtk4LayerShell.KeyboardMode.EXCLUSIVE
-        )
+        if keyboard:
+            Gtk4LayerShell.set_keyboard_mode(
+                window, Gtk4LayerShell.KeyboardMode.EXCLUSIVE
+            )
         # Anchor to all edges for fullscreen
         for edge in [
             Gtk4LayerShell.Edge.TOP,

src/moongreet/power.py

@@ -4,11 +4,14 @@
 import subprocess
 
 
+POWER_TIMEOUT = 30
+
+
 def reboot() -> None:
     """Reboot the system via loginctl."""
-    subprocess.run(["loginctl", "reboot"], check=True)
+    subprocess.run(["loginctl", "reboot"], check=True, timeout=POWER_TIMEOUT)
 
 
 def shutdown() -> None:
     """Shut down the system via loginctl."""
-    subprocess.run(["loginctl", "poweroff"], check=True)
+    subprocess.run(["loginctl", "poweroff"], check=True, timeout=POWER_TIMEOUT)

src/moongreet/sessions.py

@@ -2,6 +2,7 @@
 # ABOUTME: Parses .desktop files from standard session directories.
 
 import configparser
+from collections.abc import Sequence
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -37,8 +38,8 @@ def _parse_desktop_file(path: Path, session_type: str) -> Session | None:
 
 
 def get_sessions(
-    wayland_dirs: tuple[Path, ...] = DEFAULT_WAYLAND_DIRS,
-    xsession_dirs: tuple[Path, ...] = DEFAULT_XSESSION_DIRS,
+    wayland_dirs: Sequence[Path] = DEFAULT_WAYLAND_DIRS,
+    xsession_dirs: Sequence[Path] = DEFAULT_XSESSION_DIRS,
 ) -> list[Session]:
     """Discover available sessions from .desktop files."""
     sessions: list[Session] = []

src/moongreet/style.css

@@ -15,13 +15,11 @@ window.greeter {
     background-color: alpha(@theme_bg_color, 0.7);
 }
 
-/* Round avatar image */
+/* Round avatar image — size is set via set_size_request() in code */
 .avatar {
     border-radius: 50%;
     min-width: 128px;
     min-height: 128px;
-    max-width: 128px;
-    max-height: 128px;
     background-color: @theme_selected_bg_color;
     border: 3px solid alpha(white, 0.3);
 }

src/moongreet/users.py

@@ -2,9 +2,12 @@
 # ABOUTME: Provides User dataclass and helper functions for the greeter UI.
 
 import configparser
+import re
 from dataclasses import dataclass
 from pathlib import Path
 
+VALID_THEME_NAME = re.compile(r"^[A-Za-z0-9_-]+$")
+
 NOLOGIN_SHELLS = {"/usr/sbin/nologin", "/sbin/nologin", "/bin/false", "/usr/bin/nologin"}
 MIN_UID = 1000
 MAX_UID = 65533
@@ -102,6 +105,9 @@ def get_user_gtk_theme(config_dir: Path | None = None) -> str | None:
         return None
 
     if config.has_option("Settings", "gtk-theme-name"):
-        return config.get("Settings", "gtk-theme-name")
+        theme = config.get("Settings", "gtk-theme-name")
+        # Validate against path traversal — only allow safe theme names
+        if theme and VALID_THEME_NAME.match(theme):
+            return theme
 
     return None

tests/test_config.py

@@ -5,7 +5,7 @@ from pathlib import Path
 
 import pytest
 
-from moongreet.config import load_config, Config
+from moongreet.config import load_config, resolve_wallpaper_path, Config
 
 
 class TestLoadConfig:
@@ -35,6 +35,14 @@ class TestLoadConfig:
 
         assert config.background is None
 
+    def test_returns_defaults_for_corrupt_toml(self, tmp_path: Path) -> None:
+        toml_file = tmp_path / "moongreet.toml"
+        toml_file.write_text("this is not valid [[[ toml !!!")
+
+        config = load_config(toml_file)
+
+        assert config.background is None
+
     def test_resolves_relative_path_against_config_dir(self, tmp_path: Path) -> None:
         toml_file = tmp_path / "moongreet.toml"
         toml_file.write_text(
@@ -45,3 +53,38 @@ class TestLoadConfig:
         config = load_config(toml_file)
 
         assert config.background == tmp_path / "wallpaper.jpg"
+
+
+class TestResolveWallpaperPath:
+    """Tests for resolving the wallpaper path from config or package default."""
+
+    def test_uses_configured_path_when_exists(self, tmp_path: Path) -> None:
+        wallpaper = tmp_path / "custom.jpg"
+        wallpaper.write_bytes(b"fake-image")
+        config = Config(background=wallpaper)
+
+        path, ctx = resolve_wallpaper_path(config)
+
+        assert path == wallpaper
+        assert ctx is None
+
+    def test_falls_back_to_package_default(self) -> None:
+        config = Config(background=None)
+
+        path, ctx = resolve_wallpaper_path(config)
+
+        assert path is not None
+        assert path.exists()
+        assert ctx is not None
+        # Clean up context manager
+        ctx.__exit__(None, None, None)
+
+    def test_falls_back_when_configured_path_missing(self, tmp_path: Path) -> None:
+        config = Config(background=tmp_path / "nonexistent.jpg")
+
+        path, ctx = resolve_wallpaper_path(config)
+
+        assert path is not None
+        assert path.exists()
+        assert ctx is not None
+        ctx.__exit__(None, None, None)

tests/test_i18n.py

@@ -63,6 +63,13 @@ class TestDetectLocale:
 
         assert result == "en"
 
+    def test_rejects_non_alpha_lang(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "../../etc")
+
+        result = detect_locale()
+
+        assert result == "en"
+
 
 class TestLoadStrings:
     """Tests for loading the correct string table."""
@@ -111,8 +118,9 @@ class TestLoadStrings:
         result = strings.faillock_attempts_remaining.format(n=1)
         assert "1" in result
 
-    def test_connection_error_template(self) -> None:
+    def test_connection_error_is_generic(self) -> None:
         strings = load_strings("en")
 
-        result = strings.connection_error.format(error="timeout")
-        assert "timeout" in result
+        # Error messages should not contain format placeholders (no info leakage)
+        assert "{" not in strings.connection_error
+        assert "{" not in strings.socket_error

tests/test_integration.py

@@ -11,6 +11,7 @@ from pathlib import Path
 import pytest
 
 from moongreet.greeter import faillock_warning, FAILLOCK_MAX_ATTEMPTS
+from moongreet.i18n import load_strings
 from moongreet.ipc import create_session, post_auth_response, start_session, cancel_session
 
 
@@ -39,16 +40,27 @@ class MockGreetd:
         self._thread = threading.Thread(target=self._serve, daemon=True)
         self._thread.start()
 
+    @staticmethod
+    def _recvall(conn: socket.socket, n: int) -> bytes:
+        """Receive exactly n bytes from a socket, handling fragmented reads."""
+        buf = bytearray()
+        while len(buf) < n:
+            chunk = conn.recv(n - len(buf))
+            if not chunk:
+                break
+            buf.extend(chunk)
+        return bytes(buf)
+
     def _serve(self) -> None:
         conn, _ = self._server.accept()
         try:
             for response in self._responses:
                 # Receive a message
-                header = conn.recv(4)
+                header = self._recvall(conn, 4)
                 if len(header) < 4:
                     break
                 length = struct.unpack("!I", header)[0]
-                payload = conn.recv(length)
+                payload = self._recvall(conn, length)
                 msg = json.loads(payload.decode("utf-8"))
                 self._received.append(msg)
 
@@ -181,23 +193,31 @@ class TestLoginFlow:
 class TestFaillockWarning:
     """Tests for the faillock warning message logic."""
 
+    def test_no_warning_on_zero_attempts(self) -> None:
+        strings = load_strings("de")
+        assert faillock_warning(0, strings) is None
+
     def test_no_warning_on_first_attempt(self) -> None:
-        assert faillock_warning(1) is None
+        strings = load_strings("de")
+        assert faillock_warning(1, strings) is None
 
     def test_warning_on_second_attempt(self) -> None:
-        warning = faillock_warning(2)
+        strings = load_strings("de")
+        warning = faillock_warning(2, strings)
         assert warning is not None
         assert "1" in warning  # 1 Versuch übrig
 
     def test_warning_on_third_attempt(self) -> None:
-        warning = faillock_warning(3)
+        strings = load_strings("de")
+        warning = faillock_warning(3, strings)
         assert warning is not None
-        assert "gesperrt" in warning.lower()
+        assert warning == strings.faillock_locked
 
     def test_warning_beyond_max_attempts(self) -> None:
-        warning = faillock_warning(4)
+        strings = load_strings("de")
+        warning = faillock_warning(4, strings)
         assert warning is not None
-        assert "gesperrt" in warning.lower()
+        assert warning == strings.faillock_locked
 
     def test_max_attempts_constant_is_three(self) -> None:
         assert FAILLOCK_MAX_ATTEMPTS == 3
@@ -226,3 +246,21 @@ class TestLastUser:
         from moongreet.greeter import GreeterWindow
         result = GreeterWindow._load_last_user()
         assert result is None
+
+    def test_load_last_user_rejects_oversized_username(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        cache_path = tmp_path / "last-user"
+        cache_path.write_text("a" * 300)
+        monkeypatch.setattr("moongreet.greeter.LAST_USER_PATH", cache_path)
+
+        from moongreet.greeter import GreeterWindow
+        result = GreeterWindow._load_last_user()
+        assert result is None
+
+    def test_load_last_user_rejects_invalid_characters(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        cache_path = tmp_path / "last-user"
+        cache_path.write_text("../../etc/passwd")
+        monkeypatch.setattr("moongreet.greeter.LAST_USER_PATH", cache_path)
+
+        from moongreet.greeter import GreeterWindow
+        result = GreeterWindow._load_last_user()
+        assert result is None

tests/test_power.py

@@ -6,7 +6,7 @@ from unittest.mock import patch, call
 
 import pytest
 
-from moongreet.power import reboot, shutdown
+from moongreet.power import reboot, shutdown, POWER_TIMEOUT
 
 
 class TestReboot:
@@ -17,7 +17,7 @@ class TestReboot:
         reboot()
 
         mock_run.assert_called_once_with(
-            ["loginctl", "reboot"], check=True
+            ["loginctl", "reboot"], check=True, timeout=POWER_TIMEOUT
         )
 
     @patch("moongreet.power.subprocess.run")
@@ -36,7 +36,7 @@ class TestShutdown:
         shutdown()
 
         mock_run.assert_called_once_with(
-            ["loginctl", "poweroff"], check=True
+            ["loginctl", "poweroff"], check=True, timeout=POWER_TIMEOUT
         )
 
     @patch("moongreet.power.subprocess.run")

tests/test_users.py

@@ -187,7 +187,7 @@ class TestGetUserGtkTheme:
         assert result is None
 
     def test_handles_interpolation_characters(self, tmp_path: Path) -> None:
-        """Theme names with % characters should not trigger interpolation errors."""
+        """Theme names with % characters are rejected by validation."""
         gtk_dir = tmp_path / ".config" / "gtk-4.0"
         gtk_dir.mkdir(parents=True)
         settings = gtk_dir / "settings.ini"
@@ -195,7 +195,18 @@ class TestGetUserGtkTheme:
 
         result = get_user_gtk_theme(config_dir=gtk_dir)
 
-        assert result == "My%Theme"
+        assert result is None
+
+    def test_rejects_path_traversal_theme_name(self, tmp_path: Path) -> None:
+        """Theme names with path traversal characters should be rejected."""
+        gtk_dir = tmp_path / ".config" / "gtk-4.0"
+        gtk_dir.mkdir(parents=True)
+        settings = gtk_dir / "settings.ini"
+        settings.write_text("[Settings]\ngtk-theme-name=../../../../etc/evil\n")
+
+        result = get_user_gtk_theme(config_dir=gtk_dir)
+
+        assert result is None
 
     def test_ignores_symlinked_accountsservice_icon(self, tmp_path: Path) -> None:
         """AccountsService icon as symlink should be ignored to prevent traversal."""