Clean dist/ before wheel build to prevent stale artifacts

Security:
- Fix path traversal in _save/_load_last_session by rejecting usernames
  starting with dot (blocks '..' and hidden file creation)
- Add avatar file size limit (10 MB) to prevent DoS via large ~/.face
- Add session_name length validation on write (symmetric with read)
- Add payload size check to send_message (symmetric with recv_message)
- Set log level to INFO in production (was DEBUG)

Quality:
- Eliminate main-thread blocking on user switch: _cancel_pending_session
  now sets a cancellation event and closes the socket instead of doing
  blocking IPC. The login worker checks the event after each step.
- Move power actions (reboot/shutdown) to background threads
- Catch TimeoutExpired in addition to CalledProcessError for power actions
- Consolidate socket cleanup in _login_worker via finally block, remove
  redundant _close_greetd_sock calls from error callbacks
- Fix _select_initial_user to return False for GLib.idle_add deregistration
- Fix context manager leak in resolve_wallpaper_path on exception
- Pass Config object to GreeterWindow instead of loading it twice

.gitignore

@@ -8,3 +8,9 @@ build/
 .pytest_cache/
 .pyright/
 *.egg
+
+# makepkg build artifacts
+pkg/src/
+pkg/pkg/
+pkg/*.pkg.tar*
+pkg/greetd-moongreet/

config/greetd.conf

@@ -5,5 +5,7 @@
 vt = 1
 
 [default_session]
-command = "moongreet"
+# Moongreet braucht einen Wayland-Compositor — niri stellt diesen bereit.
+# Siehe niri-greeter.kdl fuer die Compositor-Konfiguration.
+command = "niri -c /etc/greetd/niri-greeter.kdl"
 user = "greeter"

config/moongreet.toml

@@ -4,3 +4,5 @@
 [appearance]
 # Absolute path to wallpaper image
 background = "/usr/share/backgrounds/wallpaper.jpg"
+# GTK theme for the greeter UI
+gtk-theme = "catppuccin-mocha-lavender-standard+default"

config/niri-greeter.kdl

@@ -0,0 +1,59 @@
+// ABOUTME: Niri-Konfiguration fuer den Moongreet Login-Greeter.
+// ABOUTME: Wird von greetd gestartet — minimale Config ohne Keybinds fuer Sicherheit.
+
+input {
+    keyboard {
+        xkb {
+            layout "de"
+        }
+        numlock
+    }
+
+    touchpad {
+        tap
+        natural-scroll
+    }
+
+    mouse {
+        accel-profile "flat"
+    }
+}
+
+cursor {
+    xcursor-theme "Sweet-cursors"
+}
+
+layout {
+    gaps 0
+
+    focus-ring {
+        off
+    }
+
+    border {
+        off
+    }
+}
+
+// Moongreet starten und niri beenden, sobald moongreet sich schliesst.
+// Retry-Loop stellt sicher, dass niri auch bei fruehen Crashes von moongreet beendet wird.
+spawn-sh-at-startup "moongreet; while ! niri msg action quit --skip-confirmation 2>/dev/null; do sleep 0.5; done"
+
+// Greeter-Fenster maximiert darstellen
+window-rule {
+    open-maximized true
+}
+
+hotkey-overlay {
+    skip-at-startup
+}
+
+prefer-no-csd
+
+animations {
+    off
+}
+
+binds {
+    // Keine Keybinds — verhindert Zugriff auf Terminals oder andere Aktionen
+}

pkg/PKGBUILD

@@ -1,10 +1,10 @@
-# ABOUTME: AUR PKGBUILD for Moongreet — greetd greeter for Wayland.
-# ABOUTME: Builds from git source, installs config and cache directory.
+# ABOUTME: PKGBUILD for Moongreet — greetd greeter for Wayland.
+# ABOUTME: Builds from git source with automatic version detection.
 
 # Maintainer: Dominik Kressler
 
-pkgname=moongreet
-pkgver=0.1.0
+pkgname=moongreet-git
+pkgver=0.2.0.r0.g64f08d7
 pkgrel=1
 pkgdesc="A greetd greeter for Wayland, built with Python + GTK4 + gtk4-layer-shell"
 arch=('any')
@@ -23,12 +23,20 @@ makedepends=(
     'python-installer'
     'python-hatchling'
 )
+provides=('moongreet')
+conflicts=('moongreet')
 install=moongreet.install
-source=("git+${url}.git#tag=v${pkgver}")
+source=("git+${url}.git")
 sha256sums=('SKIP')
 
+pkgver() {
+    cd "$srcdir/greetd-moongreet"
+    git describe --long --tags | sed 's/^v//;s/-/.r/;s/-/./'
+}
+
 build() {
     cd "$srcdir/greetd-moongreet"
+    rm -rf dist/
     python -m build --wheel --no-isolation
 }
 
@@ -36,9 +44,10 @@ package() {
     cd "$srcdir/greetd-moongreet"
     python -m installer --destdir="$pkgdir" dist/*.whl
 
-    # Example config
+    # Greeter config
     install -Dm644 config/moongreet.toml "$pkgdir/etc/moongreet/moongreet.toml"
 
-    # Cache directory
+    # Cache directories
     install -dm755 "$pkgdir/var/cache/moongreet"
+    install -dm755 "$pkgdir/var/cache/moongreet/last-session"
 }

pkg/moongreet.install

@@ -1,16 +1,15 @@
 # ABOUTME: pacman install hooks for Moongreet.
-# ABOUTME: Sets ownership on cache directory for the greeter user.
+# ABOUTME: Sets ownership on cache directory and prints setup instructions.
 
 post_install() {
     if getent passwd greeter > /dev/null 2>&1; then
         chown greeter:greeter /var/cache/moongreet
+        chown greeter:greeter /var/cache/moongreet/last-session
     fi
 
-    echo "==> Copy /etc/moongreet/moongreet.toml and adjust the wallpaper path."
-    echo "==> Configure greetd to use moongreet:"
-    echo "    [default_session]"
-    echo "    command = \"moongreet\""
-    echo "    user = \"greeter\""
+    echo "==> Moongreet installed."
+    echo "==> Add moongreet to your greeter compositor command in /etc/greetd/config.toml."
+    echo "==> Adjust wallpaper: /etc/moongreet/moongreet.toml"
 }
 
 post_upgrade() {

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "moongreet"
-version = "0.1.0"
+version = "0.2.0"
 description = "A greetd greeter for Wayland with GTK4"
 requires-python = ">=3.11"
 license = "MIT"

src/moongreet/config.py

@@ -17,6 +17,7 @@ class Config:
     """Greeter configuration loaded from moongreet.toml."""
 
     background: Path | None = None
+    gtk_theme: str | None = None
 
 
 def load_config(config_path: Path | None = None) -> Config:
@@ -51,6 +52,10 @@ def load_config(config_path: Path | None = None) -> Config:
             bg_path = config_path.parent / bg_path
         config.background = bg_path
 
+    gtk_theme = appearance.get("gtk-theme")
+    if gtk_theme:
+        config.gtk_theme = gtk_theme
+
     return config
 
 
@@ -71,5 +76,9 @@ def resolve_wallpaper_path(
         return config.background, None
 
     ctx = as_file(_DEFAULT_WALLPAPER_PATH)
-    path = ctx.__enter__()
+    try:
+        path = ctx.__enter__()
+    except Exception:
+        ctx.__exit__(None, None, None)
+        raise
     return path, ctx

src/moongreet/greeter.py

@@ -18,22 +18,24 @@ 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, resolve_wallpaper_path
+from moongreet.config import Config, 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.users import User, get_users, get_avatar_path
 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")
+LAST_SESSION_DIR = Path("/var/cache/moongreet/last-session")
 FAILLOCK_MAX_ATTEMPTS = 3
-VALID_USERNAME = re.compile(r"^[a-zA-Z0-9_.-]+$")
+VALID_USERNAME = re.compile(r"^[a-zA-Z0-9_][a-zA-Z0-9_.-]*$")
 MAX_USERNAME_LENGTH = 256
 PACKAGE_DATA = files("moongreet") / "data"
 DEFAULT_AVATAR_PATH = PACKAGE_DATA / "default-avatar.svg"
 AVATAR_SIZE = 128
+MAX_AVATAR_FILE_SIZE = 10 * 1024 * 1024  # 10 MB
 
 
 def faillock_warning(attempt_count: int, strings: Strings | None = None) -> str | None:
@@ -76,23 +78,25 @@ class WallpaperWindow(Gtk.ApplicationWindow):
 class GreeterWindow(Gtk.ApplicationWindow):
     """The main greeter window with login UI."""
 
-    def __init__(self, bg_path: Path | None = None, **kwargs) -> None:
+    def __init__(self, bg_path: Path | None = None, config: Config | None = None, **kwargs) -> None:
         super().__init__(**kwargs)
         self.add_css_class("greeter")
         self.set_default_size(1920, 1080)
 
-        self._config = load_config()
+        self._config = config if config is not None else load_config()
         self._strings = load_strings()
         self._users = get_users()
         self._sessions = get_sessions()
         self._selected_user: User | None = None
         self._greetd_sock: socket.socket | None = None
         self._greetd_sock_lock = threading.Lock()
+        self._login_cancelled = threading.Event()
         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._apply_global_theme()
         self._build_ui()
         self._setup_keyboard_navigation()
         # Defer initial user selection until the window is realized,
@@ -245,10 +249,13 @@ class GreeterWindow(Gtk.ApplicationWindow):
 
         return bar
 
-    def _select_initial_user(self) -> None:
-        """Select the last user or the first available user."""
+    def _select_initial_user(self) -> bool:
+        """Select the last user or the first available user.
+
+        Returns False to deregister from GLib.idle_add after a single invocation.
+        """
         if not self._users:
-            return
+            return False
 
         # Try to load last user
         last_username = self._load_last_user()
@@ -264,6 +271,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
             target_user = self._users[0]
 
         self._switch_to_user(target_user)
+        return False
 
     def _switch_to_user(self, user: User) -> None:
         """Update the UI to show the selected user."""
@@ -286,26 +294,23 @@ class GreeterWindow(Gtk.ApplicationWindow):
                 # 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)
+        # Pre-select last used session for this user
+        self._select_last_session(user)
 
         # Focus password entry
         self._password_entry.grab_focus()
 
-    def _apply_user_theme(self, user: User) -> None:
-        """Load the user's preferred GTK theme from their settings.ini."""
-        gtk_config_dir = user.home / ".config" / "gtk-4.0"
-        theme_name = get_user_gtk_theme(config_dir=gtk_config_dir)
+    def _apply_global_theme(self) -> None:
+        """Apply the GTK theme from moongreet.toml configuration."""
+        theme_name = self._config.gtk_theme
+        if not theme_name:
+            return
 
         settings = Gtk.Settings.get_default()
         if settings is None:
             return
 
-        current = settings.get_property("gtk-theme-name")
-        if theme_name and current != theme_name:
-            settings.set_property("gtk-theme-name", theme_name)
-        elif not theme_name and current:
-            settings.reset_property("gtk-theme-name")
+        settings.set_property("gtk-theme-name", theme_name)
 
     def _get_foreground_color(self) -> str:
         """Get the current GTK theme foreground color as a hex string."""
@@ -339,6 +344,9 @@ class GreeterWindow(Gtk.ApplicationWindow):
     def _set_avatar_from_file(self, path: Path, username: str | None = None) -> None:
         """Load an image file and set it as the avatar, scaled to AVATAR_SIZE."""
         try:
+            if path.stat().st_size > MAX_AVATAR_FILE_SIZE:
+                self._avatar_image.set_from_icon_name("avatar-default-symbolic")
+                return
             pixbuf = GdkPixbuf.Pixbuf.new_from_file_at_scale(
                 str(path), AVATAR_SIZE, AVATAR_SIZE, True
             )
@@ -428,6 +436,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
             return
 
         # Disable UI while authenticating — the IPC runs in a background thread
+        self._login_cancelled.clear()
         self._set_login_sensitive(False)
         thread = threading.Thread(
             target=self._login_worker,
@@ -439,26 +448,41 @@ class GreeterWindow(Gtk.ApplicationWindow):
     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:
+            if self._login_cancelled.is_set():
+                return
+
             sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
             sock.settimeout(10.0)
             sock.connect(sock_path)
             with self._greetd_sock_lock:
                 self._greetd_sock = sock
 
-            # Step 1: Create session
+            # Step 1: Create session — if a stale session exists, cancel it and retry
             response = create_session(sock, user.username)
 
-            if response.get("type") == "error":
-                GLib.idle_add(self._on_login_error, response, self._strings.auth_failed)
+            if self._login_cancelled.is_set():
                 return
 
+            if response.get("type") == "error":
+                cancel_session(sock)
+                response = create_session(sock, user.username)
+                if self._login_cancelled.is_set():
+                    return
+                if response.get("type") == "error":
+                    GLib.idle_add(self._on_login_error, response, self._strings.auth_failed)
+                    return
+
             # Step 2: Send password if auth message received
             if response.get("type") == "auth_message":
                 response = post_auth_response(sock, password)
 
+                if self._login_cancelled.is_set():
+                    return
+
                 if response.get("type") == "error":
                     self._failed_attempts[user.username] = self._failed_attempts.get(user.username, 0) + 1
                     warning = faillock_warning(self._failed_attempts[user.username], self._strings)
+                    cancel_session(sock)
                     GLib.idle_add(self._on_login_auth_error, response, warning)
                     return
 
@@ -477,32 +501,36 @@ class GreeterWindow(Gtk.ApplicationWindow):
                     return
                 response = start_session(sock, cmd)
 
+                if self._login_cancelled.is_set():
+                    return
+
                 if response.get("type") == "success":
                     self._save_last_user(user.username)
-                    self._close_greetd_sock()
+                    self._save_last_session(user.username, session.name)
                     GLib.idle_add(self.get_application().quit)
                     return
                 else:
                     GLib.idle_add(self._on_login_error, response, self._strings.session_start_failed)
+                    return
 
+        except (ConnectionError, OSError, ValueError) as e:
+            if self._login_cancelled.is_set():
+                # Socket was closed by _cancel_pending_session — exit silently
+                return
+            logger.error("greetd IPC error: %s", e)
+            if isinstance(e, ConnectionError):
+                GLib.idle_add(self._on_login_error, None, self._strings.connection_error)
+            else:
+                GLib.idle_add(self._on_login_error, None, self._strings.socket_error)
+        finally:
             self._close_greetd_sock()
 
-        except ConnectionError as e:
-            logger.error("greetd connection error: %s", e)
-            self._close_greetd_sock()
-            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()
-            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:
@@ -511,17 +539,16 @@ class GreeterWindow(Gtk.ApplicationWindow):
         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."""
-        with self._greetd_sock_lock:
-            if self._greetd_sock:
-                try:
-                    cancel_session(self._greetd_sock)
-                except (ConnectionError, OSError):
-                    pass
+        """Cancel any in-progress greetd session.
+
+        Sets the cancellation event and closes the socket to interrupt
+        any blocking I/O in the login worker. The worker checks the
+        event and exits silently instead of showing an error.
+        """
+        self._login_cancelled.set()
         self._close_greetd_sock()
 
     def _get_selected_session(self) -> Session | None:
@@ -533,6 +560,18 @@ class GreeterWindow(Gtk.ApplicationWindow):
             return self._sessions[idx]
         return None
 
+    def _select_last_session(self, user: User) -> None:
+        """Pre-select the last used session for a user in the dropdown."""
+        if not self._sessions:
+            return
+        last_session_name = self._load_last_session(user.username)
+        if not last_session_name:
+            return
+        for i, session in enumerate(self._sessions):
+            if session.name == last_session_name:
+                self._session_dropdown.set_selected(i)
+                return
+
     MAX_GREETD_ERROR_LENGTH = 200
 
     def _show_greetd_error(self, response: dict, fallback: str) -> None:
@@ -552,17 +591,26 @@ class GreeterWindow(Gtk.ApplicationWindow):
 
     def _on_reboot_clicked(self, button: Gtk.Button) -> None:
         """Handle reboot button click."""
-        try:
-            reboot()
-        except subprocess.CalledProcessError:
-            self._show_error(self._strings.reboot_failed)
+        button.set_sensitive(False)
+        threading.Thread(
+            target=self._power_worker, args=(reboot, self._strings.reboot_failed),
+            daemon=True,
+        ).start()
 
     def _on_shutdown_clicked(self, button: Gtk.Button) -> None:
         """Handle shutdown button click."""
+        button.set_sensitive(False)
+        threading.Thread(
+            target=self._power_worker, args=(shutdown, self._strings.shutdown_failed),
+            daemon=True,
+        ).start()
+
+    def _power_worker(self, action, error_msg: str) -> None:
+        """Run a power action in a background thread to avoid blocking the GTK main loop."""
         try:
-            shutdown()
-        except subprocess.CalledProcessError:
-            self._show_error(self._strings.shutdown_failed)
+            action()
+        except (subprocess.CalledProcessError, subprocess.TimeoutExpired):
+            GLib.idle_add(self._show_error, error_msg)
 
     @staticmethod
     def _load_last_user() -> str | None:
@@ -585,3 +633,32 @@ class GreeterWindow(Gtk.ApplicationWindow):
             LAST_USER_PATH.write_text(username)
         except OSError:
             pass  # Non-critical — cache dir may not be writable
+
+    MAX_SESSION_NAME_LENGTH = 256
+
+    @staticmethod
+    def _save_last_session(username: str, session_name: str) -> None:
+        """Save the last used session name for a user to cache."""
+        if not VALID_USERNAME.match(username) or len(username) > MAX_USERNAME_LENGTH:
+            return
+        if not session_name or len(session_name) > GreeterWindow.MAX_SESSION_NAME_LENGTH:
+            return
+        try:
+            LAST_SESSION_DIR.mkdir(parents=True, exist_ok=True)
+            (LAST_SESSION_DIR / username).write_text(session_name)
+        except OSError:
+            pass  # Non-critical — cache dir may not be writable
+
+    @staticmethod
+    def _load_last_session(username: str) -> str | None:
+        """Load the last used session name for a user from cache."""
+        session_file = LAST_SESSION_DIR / username
+        if not session_file.exists():
+            return None
+        try:
+            name = session_file.read_text().strip()
+        except OSError:
+            return None
+        if not name or len(name) > GreeterWindow.MAX_SESSION_NAME_LENGTH:
+            return None
+        return name

src/moongreet/ipc.py

@@ -22,14 +22,16 @@ def _recvall(sock: Any, n: int) -> bytes:
 def send_message(sock: Any, msg: dict) -> None:
     """Send a length-prefixed JSON message to the greetd socket."""
     payload = json.dumps(msg).encode("utf-8")
-    header = struct.pack("!I", len(payload))
+    if len(payload) > MAX_PAYLOAD_SIZE:
+        raise ValueError(f"Payload too large: {len(payload)} bytes (max {MAX_PAYLOAD_SIZE})")
+    header = struct.pack("=I", len(payload))
     sock.sendall(header + payload)
 
 
 def recv_message(sock: Any) -> dict:
     """Receive a length-prefixed JSON message from the greetd socket."""
     header = _recvall(sock, 4)
-    length = struct.unpack("!I", header)[0]
+    length = struct.unpack("=I", header)[0]
 
     if length > MAX_PAYLOAD_SIZE:
         raise ConnectionError(f"Payload too large: {length} bytes (max {MAX_PAYLOAD_SIZE})")

src/moongreet/main.py

@@ -4,6 +4,7 @@
 import logging
 import sys
 from importlib.resources import files
+from pathlib import Path
 
 import gi
 gi.require_version("Gtk", "4.0")
@@ -21,9 +22,38 @@ try:
 except (ValueError, ImportError):
     HAS_LAYER_SHELL = False
 
+LOG_DIR = Path("/var/cache/moongreet")
+LOG_FILE = LOG_DIR / "moongreet.log"
+
 logger = logging.getLogger(__name__)
 
 
+def _setup_logging() -> None:
+    """Configure logging to file and stderr."""
+    root = logging.getLogger()
+    root.setLevel(logging.INFO)
+
+    formatter = logging.Formatter(
+        "%(asctime)s %(levelname)s %(name)s: %(message)s"
+    )
+
+    # Always log to stderr
+    stderr_handler = logging.StreamHandler(sys.stderr)
+    stderr_handler.setLevel(logging.INFO)
+    stderr_handler.setFormatter(formatter)
+    root.addHandler(stderr_handler)
+
+    # Log to file if the directory is writable
+    if LOG_DIR.is_dir():
+        try:
+            file_handler = logging.FileHandler(LOG_FILE)
+            file_handler.setLevel(logging.INFO)
+            file_handler.setFormatter(formatter)
+            root.addHandler(file_handler)
+        except PermissionError:
+            logger.warning("Cannot write to %s", LOG_FILE)
+
+
 class MoongreetApp(Gtk.Application):
     """GTK Application for the Moongreet greeter."""
 
@@ -34,14 +64,18 @@ class MoongreetApp(Gtk.Application):
 
     def do_activate(self) -> None:
         """Create and present greeter windows on all monitors."""
-        self._register_icons()
-        self._load_css()
+        display = Gdk.Display.get_default()
+        if display is None:
+            logger.error("No display available — cannot start greeter UI")
+            return
+
+        self._register_icons(display)
+        self._load_css(display)
 
         # 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
 
@@ -55,7 +89,7 @@ class MoongreetApp(Gtk.Application):
             primary_monitor = monitors.get_item(0)
 
         # Main greeter window (login UI) on primary monitor
-        greeter = GreeterWindow(bg_path=bg_path, application=self)
+        greeter = GreeterWindow(bg_path=bg_path, config=config, application=self)
         if HAS_LAYER_SHELL:
             self._setup_layer_shell(greeter, keyboard=True)
             if primary_monitor is not None:
@@ -81,19 +115,19 @@ class MoongreetApp(Gtk.Application):
             self._wallpaper_ctx = None
         Gtk.Application.do_shutdown(self)
 
-    def _register_icons(self) -> None:
+    def _register_icons(self, display: Gdk.Display) -> None:
         """Register custom icons from the package data/icons directory."""
         icons_dir = files("moongreet") / "data" / "icons"
-        icon_theme = Gtk.IconTheme.get_for_display(Gdk.Display.get_default())
+        icon_theme = Gtk.IconTheme.get_for_display(display)
         icon_theme.add_search_path(str(icons_dir))
 
-    def _load_css(self) -> None:
+    def _load_css(self, display: Gdk.Display) -> None:
         """Load the CSS stylesheet for the greeter."""
         css_provider = Gtk.CssProvider()
         css_path = files("moongreet") / "style.css"
         css_provider.load_from_path(str(css_path))
         Gtk.StyleContext.add_provider_for_display(
-            Gdk.Display.get_default(),
+            display,
             css_provider,
             Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION,
         )
@@ -118,6 +152,8 @@ class MoongreetApp(Gtk.Application):
 
 def main() -> None:
     """Run the Moongreet application."""
+    _setup_logging()
+    logger.info("Moongreet starting")
     app = MoongreetApp()
     app.run(sys.argv)
 

src/moongreet/users.py

@@ -2,12 +2,9 @@
 # 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
@@ -106,8 +103,7 @@ def get_user_gtk_theme(config_dir: Path | None = None) -> str | None:
 
     if config.has_option("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):
+        if theme:
             return theme
 
     return None

tests/test_config.py

@@ -43,6 +43,26 @@ class TestLoadConfig:
 
         assert config.background is None
 
+    def test_loads_gtk_theme(self, tmp_path: Path) -> None:
+        toml_file = tmp_path / "moongreet.toml"
+        toml_file.write_text(
+            "[appearance]\n"
+            'gtk-theme = "Catppuccin-Mocha-Standard-Blue-Dark"\n'
+        )
+
+        config = load_config(toml_file)
+
+        assert config.gtk_theme == "Catppuccin-Mocha-Standard-Blue-Dark"
+
+    def test_returns_none_gtk_theme_when_missing(self, tmp_path: Path) -> None:
+        toml_file = tmp_path / "moongreet.toml"
+        toml_file.write_text("[appearance]\n")
+
+        config = load_config(toml_file)
+
+        assert config.gtk_theme 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(

tests/test_integration.py

@@ -10,7 +10,7 @@ from pathlib import Path
 
 import pytest
 
-from moongreet.greeter import faillock_warning, FAILLOCK_MAX_ATTEMPTS
+from moongreet.greeter import faillock_warning, FAILLOCK_MAX_ATTEMPTS, LAST_SESSION_DIR
 from moongreet.i18n import load_strings
 from moongreet.ipc import create_session, post_auth_response, start_session, cancel_session
 
@@ -59,14 +59,14 @@ class MockGreetd:
                 header = self._recvall(conn, 4)
                 if len(header) < 4:
                     break
-                length = struct.unpack("!I", header)[0]
+                length = struct.unpack("=I", header)[0]
                 payload = self._recvall(conn, length)
                 msg = json.loads(payload.decode("utf-8"))
                 self._received.append(msg)
 
                 # Send response
                 resp_payload = json.dumps(response).encode("utf-8")
-                conn.sendall(struct.pack("!I", len(resp_payload)) + resp_payload)
+                conn.sendall(struct.pack("=I", len(resp_payload)) + resp_payload)
         finally:
             conn.close()
 
@@ -112,12 +112,13 @@ class TestLoginFlow:
         assert mock.received[1] == {"type": "post_auth_message_response", "response": "geheim"}
         assert mock.received[2] == {"type": "start_session", "cmd": ["Hyprland"]}
 
-    def test_wrong_password(self, tmp_path: Path) -> None:
-        """Simulate a failed login due to wrong password."""
+    def test_wrong_password_sends_cancel(self, tmp_path: Path) -> None:
+        """After a failed login, cancel_session must be sent to free the greetd session."""
         sock_path = tmp_path / "greetd.sock"
         mock = MockGreetd(sock_path)
         mock.expect({"type": "auth_message", "auth_message_type": "secret", "auth_message": "Password:"})
         mock.expect({"type": "error", "error_type": "auth_error", "description": "Authentication failed"})
+        mock.expect({"type": "success"})  # Response to cancel_session
         mock.start()
 
         try:
@@ -131,10 +132,64 @@ class TestLoginFlow:
             assert response["type"] == "error"
             assert response["description"] == "Authentication failed"
 
+            # The greeter must cancel the session after auth failure
+            response = cancel_session(sock)
+            assert response["type"] == "success"
+
             sock.close()
         finally:
             mock.stop()
 
+        assert mock.received[2] == {"type": "cancel_session"}
+
+    def test_stale_session_cancel_and_retry(self, tmp_path: Path) -> None:
+        """When create_session fails due to a stale session, cancel and retry."""
+        sock_path = tmp_path / "greetd.sock"
+        mock = MockGreetd(sock_path)
+        # First create_session → error (stale session)
+        mock.expect({"type": "error", "error_type": "error", "description": "a session is already being configured"})
+        # cancel_session → success
+        mock.expect({"type": "success"})
+        # Second create_session → auth_message (retry succeeds)
+        mock.expect({"type": "auth_message", "auth_message_type": "secret", "auth_message": "Password:"})
+        # post_auth_response → success
+        mock.expect({"type": "success"})
+        # start_session → success
+        mock.expect({"type": "success"})
+        mock.start()
+
+        try:
+            sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+            sock.connect(str(sock_path))
+
+            # Step 1: Create session fails
+            response = create_session(sock, "dominik")
+            assert response["type"] == "error"
+
+            # Step 2: Cancel stale session
+            response = cancel_session(sock)
+            assert response["type"] == "success"
+
+            # Step 3: Retry create session
+            response = create_session(sock, "dominik")
+            assert response["type"] == "auth_message"
+
+            # Step 4: Send password
+            response = post_auth_response(sock, "geheim")
+            assert response["type"] == "success"
+
+            # Step 5: Start session
+            response = start_session(sock, ["niri-session"])
+            assert response["type"] == "success"
+
+            sock.close()
+        finally:
+            mock.stop()
+
+        assert mock.received[0] == {"type": "create_session", "username": "dominik"}
+        assert mock.received[1] == {"type": "cancel_session"}
+        assert mock.received[2] == {"type": "create_session", "username": "dominik"}
+
     def test_multi_stage_auth_sends_cancel(self, tmp_path: Path) -> None:
         """When greetd sends a second auth_message after password, cancel the session."""
         sock_path = tmp_path / "greetd.sock"
@@ -190,6 +245,101 @@ class TestLoginFlow:
         assert mock.received[1] == {"type": "cancel_session"}
 
 
+class TestSessionCancellation:
+    """Tests for cancelling an in-progress greetd session during user switch."""
+
+    def test_cancel_closes_socket_and_sets_event(self, tmp_path: Path) -> None:
+        """_cancel_pending_session should close the socket and set the cancelled event."""
+        from moongreet.greeter import GreeterWindow
+
+        win = GreeterWindow.__new__(GreeterWindow)
+        win._greetd_sock_lock = threading.Lock()
+        win._login_cancelled = threading.Event()
+
+        # Create a real socket pair to verify close
+        server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        sock_path = tmp_path / "test.sock"
+        server.bind(str(sock_path))
+        server.listen(1)
+        client = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        client.connect(str(sock_path))
+        server.close()
+
+        win._greetd_sock = client
+        win._cancel_pending_session()
+
+        assert win._login_cancelled.is_set()
+        assert win._greetd_sock is None
+
+    def test_cancel_is_noop_without_socket(self) -> None:
+        """_cancel_pending_session should be safe to call when no socket exists."""
+        from moongreet.greeter import GreeterWindow
+
+        win = GreeterWindow.__new__(GreeterWindow)
+        win._greetd_sock_lock = threading.Lock()
+        win._login_cancelled = threading.Event()
+        win._greetd_sock = None
+
+        win._cancel_pending_session()
+
+        assert win._login_cancelled.is_set()
+        assert win._greetd_sock is None
+
+    def test_cancel_does_not_block_main_thread(self, tmp_path: Path) -> None:
+        """_cancel_pending_session must not do blocking I/O — only close the socket."""
+        from moongreet.greeter import GreeterWindow
+
+        win = GreeterWindow.__new__(GreeterWindow)
+        win._greetd_sock_lock = threading.Lock()
+        win._login_cancelled = threading.Event()
+
+        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        win._greetd_sock = sock
+
+        # Should complete nearly instantly (no IPC calls)
+        import time
+        start = time.monotonic()
+        win._cancel_pending_session()
+        elapsed = time.monotonic() - start
+
+        assert elapsed < 0.1  # No blocking I/O
+
+    def test_worker_exits_silently_when_cancelled(self, tmp_path: Path) -> None:
+        """_login_worker should exit without showing an error when cancelled mid-flight."""
+        from unittest.mock import MagicMock, patch
+        from moongreet.greeter import GreeterWindow
+        from moongreet.users import User
+
+        win = GreeterWindow.__new__(GreeterWindow)
+        win._greetd_sock_lock = threading.Lock()
+        win._login_cancelled = threading.Event()
+        win._greetd_sock = None
+        win._failed_attempts = {}
+        win._strings = MagicMock()
+
+        # Set cancelled before the worker runs
+        win._login_cancelled.set()
+
+        # Create a socket that will fail (simulating closed socket)
+        sock_path = tmp_path / "greetd.sock"
+        server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        server.bind(str(sock_path))
+        server.listen(1)
+
+        user = User(username="dom", uid=1000, gecos="Dominik", home=Path("/home/dom"), shell="/bin/zsh")
+
+        with patch("moongreet.greeter.GLib.idle_add") as mock_idle:
+            win._login_worker(user, "pw", MagicMock(exec_cmd="niri-session"), str(sock_path))
+
+            # Should NOT have scheduled any error callback
+            for call in mock_idle.call_args_list:
+                func = call[0][0]
+                assert func != win._on_login_error, "Worker should not show error when cancelled"
+                assert func != win._on_login_auth_error, "Worker should not show auth error when cancelled"
+
+        server.close()
+
+
 class TestFaillockWarning:
     """Tests for the faillock warning message logic."""
 
@@ -264,3 +414,65 @@ class TestLastUser:
         from moongreet.greeter import GreeterWindow
         result = GreeterWindow._load_last_user()
         assert result is None
+
+
+class TestLastSession:
+    """Tests for saving and loading the last session per user."""
+
+    def test_save_and_load_last_session(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr("moongreet.greeter.LAST_SESSION_DIR", tmp_path)
+
+        from moongreet.greeter import GreeterWindow
+        GreeterWindow._save_last_session("dominik", "Niri")
+
+        session_file = tmp_path / "dominik"
+        assert session_file.exists()
+        assert session_file.read_text() == "Niri"
+
+        result = GreeterWindow._load_last_session("dominik")
+        assert result == "Niri"
+
+    def test_load_last_session_missing_file(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr("moongreet.greeter.LAST_SESSION_DIR", tmp_path)
+
+        from moongreet.greeter import GreeterWindow
+        result = GreeterWindow._load_last_session("nobody")
+        assert result is None
+
+    def test_load_last_session_rejects_oversized_name(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr("moongreet.greeter.LAST_SESSION_DIR", tmp_path)
+        (tmp_path / "dominik").write_text("A" * 300)
+
+        from moongreet.greeter import GreeterWindow
+        result = GreeterWindow._load_last_session("dominik")
+        assert result is None
+
+    def test_save_last_session_validates_username(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        """Usernames with path traversal should not create files outside the cache dir."""
+        monkeypatch.setattr("moongreet.greeter.LAST_SESSION_DIR", tmp_path)
+
+        from moongreet.greeter import GreeterWindow
+        GreeterWindow._save_last_session("../../etc/evil", "Niri")
+
+        # Should not have created any file
+        assert not (tmp_path / "../../etc/evil").exists()
+
+    def test_regex_rejects_dot_dot_username(self) -> None:
+        """Username '..' must not pass VALID_USERNAME validation."""
+        from moongreet.greeter import VALID_USERNAME
+        assert VALID_USERNAME.match("..") is None
+
+    def test_regex_rejects_dot_username(self) -> None:
+        """Username '.' must not pass VALID_USERNAME validation."""
+        from moongreet.greeter import VALID_USERNAME
+        assert VALID_USERNAME.match(".") is None
+
+    def test_regex_allows_dot_in_middle(self) -> None:
+        """Usernames like 'first.last' must still be valid."""
+        from moongreet.greeter import VALID_USERNAME
+        assert VALID_USERNAME.match("first.last") is not None
+
+    def test_regex_rejects_leading_dot(self) -> None:
+        """Usernames starting with '.' are rejected (hidden files)."""
+        from moongreet.greeter import VALID_USERNAME
+        assert VALID_USERNAME.match(".hidden") is None

tests/test_ipc.py

@@ -38,7 +38,7 @@ class FakeSocket:
     def with_response(cls, response: dict) -> "FakeSocket":
         """Create a FakeSocket pre-loaded with a length-prefixed JSON response."""
         payload = json.dumps(response).encode("utf-8")
-        data = struct.pack("!I", len(payload)) + payload
+        data = struct.pack("=I", len(payload)) + payload
         return cls(recv_data=data)
 
 
@@ -73,7 +73,7 @@ class TestSendMessage:
         send_message(sock, msg)
 
         payload = json.dumps(msg).encode("utf-8")
-        expected = struct.pack("!I", len(payload)) + payload
+        expected = struct.pack("=I", len(payload)) + payload
         assert bytes(sock.sent) == expected
 
     def test_sends_empty_dict(self) -> None:
@@ -82,7 +82,7 @@ class TestSendMessage:
         send_message(sock, {})
 
         payload = json.dumps({}).encode("utf-8")
-        expected = struct.pack("!I", len(payload)) + payload
+        expected = struct.pack("=I", len(payload)) + payload
         assert bytes(sock.sent) == expected
 
     def test_sends_nested_message(self) -> None:
@@ -93,12 +93,20 @@ class TestSendMessage:
 
         # Verify the payload is correctly length-prefixed
         length_bytes = bytes(sock.sent[:4])
-        length = struct.unpack("!I", length_bytes)[0]
+        length = struct.unpack("=I", length_bytes)[0]
         decoded = json.loads(sock.sent[4:])
         assert length == len(json.dumps(msg).encode("utf-8"))
         assert decoded == msg
 
 
+    def test_rejects_oversized_payload(self) -> None:
+        sock = FakeSocket()
+        msg = {"type": "huge", "data": "x" * 100000}
+
+        with pytest.raises(ValueError, match="Payload too large"):
+            send_message(sock, msg)
+
+
 class TestRecvMessage:
     """Tests for receiving and decoding length-prefixed JSON messages."""
 
@@ -132,7 +140,7 @@ class TestRecvMessage:
         """recv() may return fewer bytes than requested — must loop."""
         response = {"type": "success"}
         payload = json.dumps(response).encode("utf-8")
-        data = struct.pack("!I", len(payload)) + payload
+        data = struct.pack("=I", len(payload)) + payload
         sock = FragmentingSocket(data, chunk_size=3)
 
         result = recv_message(sock)
@@ -141,7 +149,7 @@ class TestRecvMessage:
 
     def test_rejects_oversized_payload(self) -> None:
         """Payloads exceeding the size limit must be rejected."""
-        header = struct.pack("!I", 10_000_000)
+        header = struct.pack("=I", 10_000_000)
         sock = FakeSocket(recv_data=header)
 
         with pytest.raises(ConnectionError, match="too large"):
@@ -162,7 +170,7 @@ class TestCreateSession:
         result = create_session(sock, "dominik")
 
         # Verify sent message
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {"type": "create_session", "username": "dominik"}
         assert result == response
@@ -177,7 +185,7 @@ class TestPostAuthResponse:
 
         result = post_auth_response(sock, "mypassword")
 
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {
             "type": "post_auth_message_response",
@@ -192,7 +200,7 @@ class TestPostAuthResponse:
 
         result = post_auth_response(sock, None)
 
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {
             "type": "post_auth_message_response",
@@ -209,7 +217,7 @@ class TestStartSession:
 
         result = start_session(sock, ["Hyprland"])
 
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {"type": "start_session", "cmd": ["Hyprland"]}
         assert result == response
@@ -220,7 +228,7 @@ class TestStartSession:
 
         result = start_session(sock, ["sway", "--config", "/etc/sway/config"])
 
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {
             "type": "start_session",
@@ -237,7 +245,7 @@ class TestCancelSession:
 
         result = cancel_session(sock)
 
-        length = struct.unpack("!I", bytes(sock.sent[:4]))[0]
+        length = struct.unpack("=I", bytes(sock.sent[:4]))[0]
         sent_msg = json.loads(sock.sent[4 : 4 + length])
         assert sent_msg == {"type": "cancel_session"}
         assert result == response

tests/test_power.py

@@ -27,6 +27,13 @@ class TestReboot:
         with pytest.raises(subprocess.CalledProcessError):
             reboot()
 
+    @patch("moongreet.power.subprocess.run")
+    def test_raises_on_timeout(self, mock_run) -> None:
+        mock_run.side_effect = subprocess.TimeoutExpired("loginctl", POWER_TIMEOUT)
+
+        with pytest.raises(subprocess.TimeoutExpired):
+            reboot()
+
 
 class TestShutdown:
     """Tests for the shutdown power action."""
@@ -45,3 +52,10 @@ class TestShutdown:
 
         with pytest.raises(subprocess.CalledProcessError):
             shutdown()
+
+    @patch("moongreet.power.subprocess.run")
+    def test_raises_on_timeout(self, mock_run) -> None:
+        mock_run.side_effect = subprocess.TimeoutExpired("loginctl", POWER_TIMEOUT)
+
+        with pytest.raises(subprocess.TimeoutExpired):
+            shutdown()

tests/test_users.py

@@ -186,27 +186,18 @@ class TestGetUserGtkTheme:
 
         assert result is None
 
-    def test_handles_interpolation_characters(self, tmp_path: Path) -> None:
-        """Theme names with % characters are rejected by validation."""
+    def test_passes_theme_with_special_characters(self, tmp_path: Path) -> None:
+        """Theme names with special characters are passed through to GTK."""
         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=My%Theme\n")
+        settings.write_text(
+            "[Settings]\ngtk-theme-name=catppuccin-mocha-lavender-standard+default\n"
+        )
 
         result = get_user_gtk_theme(config_dir=gtk_dir)
 
-        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
+        assert result == "catppuccin-mocha-lavender-standard+default"
 
     def test_ignores_symlinked_accountsservice_icon(self, tmp_path: Path) -> None:
         """AccountsService icon as symlink should be ignored to prevent traversal."""