fix: audit LOW fixes — stdout null, utf-8 path, debug value, hidden sessions (v0.8.6)

- power::run_command: .stdout(Stdio::null()) — the pipe was never drained,
  structurally fragile even if no current caller hits it.
- config: replace to_string_lossy() on relative wallpaper paths with
  to_str() + log::warn, so non-UTF-8 paths are dropped cleanly instead
  of being mangled into unopenable U+FFFD strings.
- main: require MOONGREET_DEBUG=1 to raise verbosity. Mere presence of
  the var must not leak socket paths, usernames, and auth round counts
  into the journal.
- sessions: parse Hidden= and NoDisplay= keys, skip entries marked true.
  Keeps disabled or stub .desktop files out of the session dropdown.

.gitea/workflows/update-pkgver.yaml

@@ -0,0 +1,43 @@
+# ABOUTME: Updates pkgver in moonarch-pkgbuilds after a push to main.
+# ABOUTME: Ensures paru detects new versions of this package.
+
+name: Update PKGBUILD version
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  update-pkgver:
+    runs-on: moonarch
+    steps:
+      - name: Checkout source repo
+        run: |
+          git clone --bare http://gitea:3000/nevaforget/greetd-moongreet.git source.git
+          cd source.git
+          PKGVER=$(git describe --long --tags | sed 's/^v//;s/-/.r/;s/-/./')
+          echo "New pkgver: $PKGVER"
+          echo "$PKGVER" > /tmp/pkgver
+
+      - name: Update PKGBUILD
+        run: |
+          PKGVER=$(cat /tmp/pkgver)
+          git clone http://gitea:3000/nevaforget/moonarch-pkgbuilds.git pkgbuilds
+          cd pkgbuilds
+
+          OLD_VER=$(grep '^pkgver=' moongreet-git/PKGBUILD | cut -d= -f2)
+          if [ "$OLD_VER" = "$PKGVER" ]; then
+            echo "pkgver already up to date ($PKGVER)"
+            exit 0
+          fi
+
+          sed -i "s/^pkgver=.*/pkgver=$PKGVER/" moongreet-git/PKGBUILD
+          sed -i "s/^\tpkgver = .*/\tpkgver = $PKGVER/" moongreet-git/.SRCINFO
+          echo "Updated pkgver: $OLD_VER → $PKGVER"
+
+          git config user.name "pkgver-bot"
+          git config user.email "gitea@moonarch.de"
+          git add moongreet-git/PKGBUILD moongreet-git/.SRCINFO
+          git commit -m "chore(moongreet-git): bump pkgver to $PKGVER"
+          git -c http.extraHeader="Authorization: token ${{ secrets.PKGBUILD_TOKEN }}" push

CLAUDE.md

@@ -1,7 +1,5 @@
 # Moongreet
 
-**Name**: Selene (Mondgöttin — passend zu Moon-greet)
-
 ## Projekt
 
 Moongreet ist ein greetd-Greeter für Wayland, gebaut mit Rust + gtk4-rs + gtk4-layer-shell.
@@ -17,7 +15,7 @@ Teil des Moonarch-Ökosystems.
 ## Projektstruktur
 
 - `src/` — Rust-Quellcode (main.rs, greeter.rs, ipc.rs, config.rs, users.rs, sessions.rs, i18n.rs, power.rs)
-- `resources/` — GResource-Assets (style.css, wallpaper.jpg, default-avatar.svg)
+- `resources/` — GResource-Assets (style.css, default-avatar.svg)
 - `config/` — Beispiel-Konfigurationsdateien für `/etc/moongreet/` und `/etc/greetd/`
 - `pkg/` — PKGBUILD für Arch-Linux-Paketierung (`makepkg -sf`)
 
@@ -44,9 +42,10 @@ cd pkg && makepkg -sf && sudo pacman -U moongreet-git-<version>-x86_64.pkg.tar.z
 - `sessions.rs` — Wayland/X11 Sessions aus .desktop Files
 - `power.rs` — Reboot/Shutdown via loginctl
 - `i18n.rs` — Locale-Erkennung (LANG / /etc/locale.conf) und String-Tabellen (DE/EN), alle UI- und Login-Fehlermeldungen
-- `config.rs` — TOML-Config ([appearance] background, gtk-theme) + Wallpaper-Fallback
-- `greeter.rs` — GTK4 UI (Overlay-Layout), Login-Flow via greetd IPC, Faillock-Warnung, Avatar-Cache, Last-User/Last-Session Persistence (0o600 Permissions)
-- `main.rs` — Entry Point, GTK App, Layer Shell Setup, Multi-Monitor, systemd-journal-logger
+- `fingerprint.rs` — fprintd D-Bus Probe (gio::DBusProxy) — Geräteerkennung und Enrollment-Check für UI-Feedback
+- `config.rs` — TOML-Config ([appearance] background, gtk-theme, fingerprint-enabled) + Wallpaper-Fallback + Blur-Validierung (finite, clamp 0–200)
+- `greeter.rs` — GTK4 UI (Overlay-Layout), Login-Flow via greetd IPC (Multi-Stage-Auth für fprintd), Faillock-Warnung, Avatar-Cache, Last-User/Last-Session Persistence (0o700 Dirs, 0o600 Files)
+- `main.rs` — Entry Point, GTK App, Layer Shell Setup, Multi-Monitor mit Hotplug via `items-changed` auf Monitor-ListModel (one greeter window per monitor, first gets keyboard), systemd-journal-logger
 - `resources/style.css` — Catppuccin-inspiriertes Theme
 
 ## Design Decisions
@@ -56,12 +55,13 @@ cd pkg && makepkg -sf && sudo pacman -U moongreet-git-<version>-x86_64.pkg.tar.z
 - **Async Login**: `glib::spawn_future_local` + `gio::spawn_blocking` statt raw Threads
 - **Socket-Cancellation**: `Arc<Mutex<Option<UnixStream>>>` + `AtomicBool` für saubere Abbrüche
 - **Avatar-Cache**: `HashMap<String, gdk::Texture>` in `Rc<RefCell<GreeterState>>`
-- **GPU-Blur via GskBlurNode**: `Snapshot::push_blur()` + `GskRenderer::render_texture()` im `connect_realize` Callback — kein CPU-Blur, kein Disk-Cache, kein `image`-Crate
+- **GPU-Blur via GskBlurNode**: `Snapshot::push_blur()` + `GskRenderer::render_texture()` im `connect_realize` Callback — kein CPU-Blur, kein Disk-Cache, kein `image`-Crate. Blurred Texture wird per `Rc<RefCell<Option<gdk::Texture>>>` über alle Monitore gecacht (1x GPU-Renderpass statt N).
+- **Fingerprint via greetd Multi-Stage PAM**: fprintd D-Bus nur als Probe (Gerät/Enrollment), eigentliche Verifizierung läuft über PAM im greetd-Auth-Loop. `auth_message_type: "secret"` → Passwort, alles andere → `None` (PAM entscheidet). 60s Socket-Timeout bei fprintd. Device-Proxy in `GreeterState` gecacht, Generation-Counter gegen Race Conditions bei schnellem User-Switch.
 - **Symmetrie mit moonlock/moonset**: Gleiche Patterns (i18n, config, users, power, GResource, GPU-Blur)
 - **Session-Validierung**: Relative Pfade erlaubt (greetd löst PATH auf), nur `..`/Null-Bytes werden abgelehnt
 - **GTK-Theme-Validierung**: Nur alphanumerisch + `_-+.` erlaubt, verhindert Path-Traversal über Config
 - **Journal-Logging**: `systemd-journal-logger` statt File-Logging — `journalctl -t moongreet`, Debug-Level per `MOONGREET_DEBUG` Env-Var
-- **File Permissions**: Cache-Dateien 0o600
+- **File Permissions**: Cache-Verzeichnisse 0o700 via `DirBuilder::mode()`, Cache-Dateien 0o600
 - **Testbare Persistence**: `save_*_to`/`load_*_from` Varianten mit konfigurierbarem Pfad für Unit-Tests
 - **Shared Wallpaper Texture**: `gdk::Texture` wird einmal in `load_background_texture()` dekodiert und per Ref-Count an alle Fenster geteilt — vermeidet redundante JPEG-Dekodierung pro Monitor
 - **Wallpaper-Validierung**: GResource-Zweig via `resources_lookup_data()` + `from_bytes()` (kein Abort bei fehlendem Pfad), Dateigröße-Limit 50 MB, non-UTF-8-Pfade → `None`

Cargo.lock

@@ -59,6 +59,12 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
+[[package]]
+name = "cfg_aliases"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
+
 [[package]]
 name = "equivalent"
 version = "1.0.2"
@@ -569,7 +575,7 @@ dependencies = [
 
 [[package]]
 name = "moongreet"
-version = "0.5.0"
+version = "0.8.6"
 dependencies = [
  "gdk-pixbuf",
  "gdk4",
@@ -580,11 +586,25 @@ dependencies = [
  "gtk4",
  "gtk4-layer-shell",
  "log",
+ "nix",
  "serde",
  "serde_json",
  "systemd-journal-logger",
  "tempfile",
  "toml 0.8.23",
+ "zeroize",
+]
+
+[[package]]
+name = "nix"
+version = "0.29.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "71e2746dc3a24dd78b3cfcb7be93368c6de9963d30f43a6a73998a9cf4b17b46"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "cfg_aliases",
+ "libc",
 ]
 
 [[package]]
@@ -1124,6 +1144,12 @@ version = "0.8.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3ae8337f8a065cfc972643663ea4279e04e7256de865aa66fe25cec5fb912d3f"
 
+[[package]]
+name = "zeroize"
+version = "1.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+
 [[package]]
 name = "zmij"
 version = "1.0.21"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moongreet"
-version = "0.5.1"
+version = "0.8.6"
 edition = "2024"
 description = "A greetd greeter for Wayland with GTK4 and Layer Shell"
 license = "MIT"
@@ -16,11 +16,18 @@ toml = "0.8"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 graphene-rs = { version = "0.22", package = "graphene-rs" }
+nix = { version = "0.29", features = ["signal"] }
+zeroize = { version = "1", features = ["std"] }
 log = "0.4"
 systemd-journal-logger = "2.2"
 
 [dev-dependencies]
 tempfile = "3"
 
+[profile.release]
+lto = "thin"
+codegen-units = 1
+strip = true
+
 [build-dependencies]
 glib-build-tools = "0.22"

DECISIONS.md

@@ -1,21 +1,105 @@
 # Decisions
 
+## 2026-04-24 – Audit LOW fixes: stdout null, utf-8 path, debug value, hidden sessions (v0.8.6)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Four LOW findings cleared in a single pass. (1) `power::run_command` piped stdout it never read — structurally fragile even though current callers stay well under the pipe buffer. (2) Relative wallpaper paths were resolved via `to_string_lossy`, silently substituting `U+FFFD` for non-UTF-8 bytes and producing a path that cannot be opened. (3) `MOONGREET_DEBUG` escalated log verbosity on mere presence, so an empty variable leaked auth metadata into the journal. (4) `Hidden=true` and `NoDisplay=true` `.desktop` entries appeared in the session dropdown even though they mark disabled or stub sessions.
+- **Tradeoffs**: Gating debug on the literal value `"1"` is slightly stricter than most tools but matches the security-first posture. Filtering Hidden/NoDisplay means legitimately hidden but functional sessions are now unselectable from the greeter — acceptable, that is the convention these keys signal.
+- **How**: (1) `.stdout(Stdio::null())` replaces the unused pipe. (2) `to_string_lossy().to_string()` replaced by `to_str().map(|s| s.to_string())` with a `log::warn!` fallback for non-UTF-8 paths. (3) `match std::env::var("MOONGREET_DEBUG").ok().as_deref()` → `Some("1")` selects Debug, everything else Info. (4) `parse_desktop_file` reads `Hidden=` and `NoDisplay=`, returns `None` if either is `true`.
+
+## 2026-04-24 – Audit MEDIUM fixes: FP double-init, async avatar, symlink, FD leak (v0.8.5)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Six MEDIUM findings: (1) i18n test `all_string_fields_nonempty` missed four string fields — future locales could ship empty strings unnoticed. (2) Fast user-switch could spawn two parallel fprintd `init_async` calls because both coroutines saw `fingerprint_probe = None` before either stored its probe. (3) Synchronous avatar decode via `Pixbuf::from_file_at_scale` on the GTK main thread, stalling clicks. (4) Wallpaper `MAX_WALLPAPER_FILE_SIZE = 50 MB` bounded decode at up to ~2 s. (5) Fallback wallpaper path used `is_file()` which follows symlinks, inconsistent with the symlink-rejecting user-config path. (6) After a failed login the cloned `greetd_sock` descriptor remained in shared state until the next user switch, accumulating stale FDs across retries.
+- **Tradeoffs**: The init-race guard uses a bool flag on `GreeterState` + a 25 ms polling yield — cheap and race-free, but introduces a very short latency when a second probe waits. Lowering `MAX_WALLPAPER_FILE_SIZE` to 10 MB and `MAX_AVATAR_FILE_SIZE` to 5 MB caps worst-case decode but rejects legitimately huge (4K raw) wallpapers; acceptable for a greeter. Async avatar decode shows the default icon for a frame or two on cache miss.
+- **How**: (1) Four new `assert!` lines in `i18n::tests::all_string_fields_nonempty`. (2) New `fingerprint_probe_initializing: bool` on `GreeterState`, atomic check-and-set under `borrow_mut`, losing coroutines yield via `glib::timeout_future` until the winning init completes. (3) `set_avatar_from_file` uses `gio::File::read_future` + `Pixbuf::from_stream_at_scale_future` inside a `glib::spawn_future_local`, sets the default icon first, swaps on success. (4) Lower both size constants. (5) `resolve_background_path_with` now applies the same `symlink_metadata` + `!is_symlink` check to the Moonarch fallback. (6) After the login worker returns, `state.greetd_sock.lock().take()` drops the stale clone regardless of login outcome.
+
+## 2026-04-24 – Audit fix: shrink password-in-memory window (v0.8.4)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Security audit flagged the GTK password path as holding more copies of the plaintext password in memory than necessary. `attempt_login` wrapped the already-`Zeroizing<String>` caller value into a second `Zeroizing<String>` (`password.to_string()`), and the GTK `GString` backing `entry.text()` persisted in libc malloc'd memory until the allocator reused the page.
+- **Tradeoffs**: The GTK `GString` and the libc `strdup` copy on the PAM FFI boundary remain non-zeroizable — this is an inherent GTK/libc limitation, already documented in CLAUDE.md. This change reduces the Rust-owned copies to one and clears the `PasswordEntry` text field immediately after extraction to shorten the GTK-side window.
+- **How**: (1) `attempt_login` now takes `password: Zeroizing<String>` by value instead of `&str`, moving ownership into the `spawn_blocking` closure. (2) The redundant `Zeroizing::new(password.to_string())` inside `attempt_login` is removed. (3) `password_entry.set_text("")` is called right after the password is extracted from the activate handler, shortening the lifetime of the GTK-internal buffer.
+
+## 2026-04-21 – Ship polkit rule in moongreet instead of moonarch (v0.8.3)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Reboot/shutdown from the greeter silently failed on a fresh install. The polkit rule that grants the `greeter` user `org.freedesktop.login1.{reboot,power-off}` lived in the moonarch repo but was never installed by any PKGBUILD. The laptop worked only because the rule had been hand-deployed once.
+- **Tradeoffs**: Rule ownership moves from moonarch (system defaults) to moongreet (greeter-specific auth). Cleaner boundary — moonarch no longer needs to know about the greeter's auth requirements — but it means moongreet is now responsible for a system polkit rule that ties it to a fixed username (`greeter`).
+- **How**: Source file moved to `moongreet/config/polkit/50-moongreet-power.rules`, installed to `/etc/polkit-1/rules.d/` by `moongreet-git/PKGBUILD`. Old file removed from the moonarch repo.
+
+## 2026-04-09 – Monitor hotplug via ListModel items-changed
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Greeter windows were only created at startup. If a monitor was hotplugged (e.g. HDMI reconnect), it would show no greeter UI. Aligned with moonlock's hotplug fix (same day).
+- **Tradeoffs**: Hotplugged monitors get greeter windows without keyboard input (keyboard stays on the primary monitor). Acceptable — user can still interact on the primary screen.
+- **How**: Connect to `display.monitors().connect_items_changed()` and create new greeter windows for added monitors. Shared state (config, texture, blur_cache) moved to Rc for the closure.
+
+## 2026-04-08 – Show greeter UI on all monitors instead of just one
+
+- **Who**: ClaudeCode, Dom
+- **Why**: moonlock showed its UI on all monitors via ext-session-lock-v1, but moongreet only showed the login UI on one monitor (compositor-picked) with wallpaper-only windows on the rest. Inconsistent UX across the ecosystem.
+- **Tradeoffs**: Each monitor gets its own full greeter widget tree (slightly more memory), but the UI is lightweight. Screen mirroring (e.g., wl-mirror/screencopy) was considered and rejected — it requires an external process, compositor screencopy support, adds latency, and fights Wayland's per-output model. One-window-per-monitor is the established Wayland pattern (swaylock, hyprlock, moonlock all do this).
+- **How**: Create one `create_greeter_window()` per monitor with `set_monitor()`, only the first gets `KeyboardMode::Exclusive`. Removed `create_wallpaper_window()` (no longer needed). No layer shell fallback keeps single-window mode for development.
+
+## 2026-04-06 – Restore explicit gtk-theme in moongreet config
+
+- **Who**: ClaudeCode, Dom
+- **Why**: GTK4 under greetd does not reliably read `/etc/xdg/gtk-4.0/settings.ini` — likely requires a settings daemon that doesn't run in the greeter session. moongreet fell back to Adwaita/Colloid-default (blue accent) instead of Colloid-Grey-Dark-Catppuccin.
+- **Tradeoffs**: Reverts `094878f` ("Remove gtk-theme from app config, use system-wide GTK settings instead"). Duplicates the theme name between settings.ini and moongreet.toml, but the explicit set via `set_gtk_theme_name()` is the only reliable path in a greetd context.
+- **How**: Added `gtk-theme = "Colloid-Grey-Dark-Catppuccin"` to example config and deployed `/etc/moongreet/moongreet.toml`.
+
+## 2026-04-02 – Replace hardcoded CSS colors with GTK theme variables
+
+- **Who**: ClaudeCode, Dom
+- **Why**: moongreet used hardcoded colors (#1a1a2e, white, #ff6b6b) while moonset already used @theme_bg_color, @theme_fg_color, @error_color etc. Inconsistent across the ecosystem and broke theme flexibility.
+- **Tradeoffs**: Depends on the active GTK theme defining standard color variables. Catppuccin Colloid provides all needed vars (@theme_bg_color, @theme_fg_color, @error_color, @success_color, @theme_selected_bg_color). Fallback behavior if a theme lacks vars is GTK's default colors — acceptable.
+- **How**: Replaced all hardcoded hex/named colors with GTK theme variables. Coordinated change across moongreet, moonlock, and moonset (all three now use identical pattern).
+
+## 2026-03-31 – Fourth audit: power timeout, timing mitigation, release profile, GREETD_SOCK caching
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Fourth triple audit found moongreet power.rs had no timeout on loginctl (greeter could freeze), username enumeration via timing differential, GREETD_SOCK re-read on every login, missing release profile, and missing GResource compression.
+- **Tradeoffs**: 500ms minimum login response time adds slight delay on fast auth but prevents timing-based username enumeration. Power timeout (30s + SIGKILL) matches moonset pattern — aggressive but prevents greeter freeze.
+- **How**: (1) power.rs adapted from moonset with 30s timeout + SIGKILL (nix dependency added). (2) 500ms min response floor in attempt_login via Instant + glib::timeout_future. (3) GREETD_SOCK cached in GreeterState at startup. (4) `[profile.release]` with LTO, codegen-units=1, strip. (5) `compressed="true"` on GResource entries. (6) SYNC comments on duplicated blur/background functions.
+
+## 2026-03-30 – Full audit fix: security, quality, performance (v0.6.2)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Three parallel audits (security, code quality, performance) identified 10 actionable findings across the codebase — from world-readable cache dirs to a GPU blur geometry bug to a race condition in fingerprint probing.
+- **Tradeoffs**: `too_many_arguments` Clippy warnings suppressed with `#[allow]` rather than introducing a `UiWidgets` struct — GTK's `clone!` macro with `#[weak]` refs requires individual widget parameters, a struct would fight the idiom. Async avatar loading skipped because `Pixbuf` is `!Send`; cache already prevents repeat loads. TOCTOU socket pre-check removed entirely — `connect()` in login_worker already handles errors, the `metadata()` check gave false security guarantees.
+- **How**: Cache dirs use `DirBuilder::mode(0o700)` instead of `create_dir_all`. Blur config clamped to `0.0..=200.0` with `is_finite()` guard. Blur texture cached in `Rc<RefCell<Option<gdk::Texture>>>` across monitors. FingerprintProbe device proxy cached in `GreeterState` with generation counter to prevent stale async writes. GPU blur geometry fixed (`-pad` origin shift instead of texture stretching). `is_valid_gtk_theme` extracted as testable function. 9 new tests.
+
+## 2026-03-29 – Fingerprint authentication via greetd multi-stage PAM
+
+- **Who**: ClaudeCode, Dom
+- **Why**: moonlock supports fprintd but moongreet rejected multi-stage auth. Users with enrolled fingerprints couldn't use them at the login screen.
+- **Tradeoffs**: Direct fprintd D-Bus verification (like moonlock) can't start a greetd session — greetd controls session creation via PAM. Using greetd multi-stage means PAM decides the auth order (fingerprint first, then password fallback), not truly parallel. Acceptable — matches standard pam_fprintd behavior.
+- **How**: Replace single-pass auth with a loop over auth_message rounds. Secret prompts get the password, non-secret prompts (fprintd) get None and block until PAM resolves. fprintd D-Bus probe (gio::DBusProxy) only for UI — detecting device availability and enrolled fingers. 60s socket timeout when fingerprint available. Config option `fingerprint-enabled` (default true).
+
+## 2026-03-28 – Remove embedded wallpaper from binary
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Wallpaper is installed by moonarch to /usr/share/moonarch/wallpaper.jpg. Embedding a 374K JPEG in the binary is redundant. GTK background color (Catppuccin Mocha base) is a clean fallback.
+- **Tradeoffs**: Without moonarch installed AND without config, greeter shows plain dark background instead of wallpaper. Acceptable — that's the expected minimal state.
+- **How**: Remove wallpaper.jpg from GResources, return None from resolve_background_path when no file found, skip wallpaper window creation and background picture when no path available.
+
 ## 2026-03-28 – GPU blur via GskBlurNode replaces CPU blur
 
-- **Who**: Ragnar, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: CPU-side Gaussian blur (`image` crate) blocked the GTK main thread for 500ms–2s on 4K wallpapers at cold cache. Disk cache and async orchestration added significant complexity.
 - **Tradeoffs**: GPU blur quality is slightly different (box-blur approximation vs true Gaussian), acceptable for wallpaper backgrounds. Removes `image` crate dependency entirely (~15 transitive crates eliminated). No disk cache needed.
 - **How**: `Snapshot::push_blur()` + `GskRenderer::render_texture()` on `connect_realize`. Blur happens once on the GPU when the widget gets its renderer, producing a concrete `gdk::Texture`. Zero startup latency. Symmetric with moonlock and moonset.
 
 ## 2026-03-28 – Optional background blur via `image` crate (superseded)
 
-- **Who**: Selene, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Blurred wallpaper as greeter background is a common UX pattern for login screens
 - **Tradeoffs**: Adds `image` crate dependency (~15 transitive crates); CPU-side Gaussian blur at load time adds startup latency proportional to image size and sigma. Acceptable because blur runs once and the texture is shared across monitors.
 - **How**: `load_background_texture(bg_path, blur_radius)` loads texture, optionally applies `imageops::blur()`, returns blurred `gdk::Texture`. Config option `background-blur: Option<f32>` in `[appearance]` TOML section.
 
 ## 2026-03-28 – Audit fixes for shared wallpaper texture (v0.4.1)
-- **Who**: Selene, Dominik
+- **Who**: ClaudeCode, Dominik
 - **Why**: Quality, performance, and security audits flagged issues in `load_background_texture()`, debug logging, and greetd error handling
 - **Tradeoffs**: GResource path now requires UTF-8 (returns `None` for non-UTF-8 instead of aborting); 50 MB wallpaper limit is generous but prevents OOM; debug logging off by default trades observability for security
 - **How**: GResource branch via `resources_lookup_data()` + `from_bytes()` (no abort), file size limit, error details only at debug level, `MOONGREET_DEBUG` env var for log level, greetd retry path truncation matching `show_greetd_error()`

README.md

@@ -12,9 +12,13 @@ Part of the Moonarch ecosystem.
 - **Last user/session** — Remembered in `/var/cache/moongreet/`
 - **Power actions** — Reboot / Shutdown via `loginctl`
 - **Layer Shell** — Fullscreen via gtk4-layer-shell (TOP layer)
-- **Multi-monitor** — Greeter on primary, wallpaper on all monitors
+- **Multi-monitor + hotplug** — Full greeter UI on all monitors (keyboard input on first), hotplugged monitors get windows automatically
+- **GPU blur** — Background blur via GskBlurNode (shared cache across monitors)
 - **i18n** — German and English (auto-detected from system locale)
 - **Faillock warning** — Warns after 2 failed attempts, locked message after 3
+- **Fingerprint** — fprintd support via greetd multi-stage PAM (configurable)
+- **Journal logging** — `journalctl -t moongreet`, debug level via `MOONGREET_DEBUG` env var
+- **Password wiping** — Zeroize on drop
 
 ## Requirements
 
@@ -56,6 +60,14 @@ sudo cp config/moongreet.toml /etc/moongreet/moongreet.toml
    user = "greeter"
    ```
 
+4. Install the polkit rule so the greeter user can reboot / power off:
+   ```bash
+   sudo install -Dm644 config/polkit/50-moongreet-power.rules \
+       /etc/polkit-1/rules.d/50-moongreet-power.rules
+   ```
+   Without this rule, `loginctl reboot` / `loginctl poweroff` fail because
+   greetd's greeter session is inactive in logind.
+
 ## Development
 
 ```bash
@@ -65,8 +77,8 @@ cargo test
 # Build release
 cargo build --release
 
-# Run locally (without greetd, needs LD_PRELOAD for layer-shell)
-LD_PRELOAD=/usr/lib/libgtk4-layer-shell.so ./target/release/moongreet
+# Run locally (without greetd, disables layer-shell)
+MOONGREET_NO_LAYER_SHELL=1 ./target/release/moongreet
 ```
 
 ## License

build.rs

@@ -1,5 +1,5 @@
 // ABOUTME: Build script for compiling GResource bundle.
-// ABOUTME: Bundles style.css, wallpaper.jpg, and default-avatar.svg into the binary.
+// ABOUTME: Bundles style.css and default-avatar.svg into the binary.
 
 fn main() {
     glib_build_tools::compile_resources(

config/moongreet.toml

@@ -4,5 +4,7 @@
 [appearance]
 # Absolute path to wallpaper image
 background = "/usr/share/backgrounds/wallpaper.jpg"
-# GTK theme for the greeter UI
-gtk-theme = "Colloid-Catppuccin"
+
+# GTK theme name — must match a directory in /usr/share/themes/
+# Required because GTK4 under greetd does not reliably read settings.ini
+gtk-theme = "Colloid-Grey-Dark-Catppuccin"

config/polkit/50-moongreet-power.rules

@@ -0,0 +1,12 @@
+// ABOUTME: Allow the greeter user to reboot and power off without authentication.
+// ABOUTME: Required because greetd's greeter session is inactive in logind.
+
+polkit.addRule(function(action, subject) {
+    if (subject.user === "greeter" &&
+        (action.id === "org.freedesktop.login1.reboot" ||
+         action.id === "org.freedesktop.login1.reboot-multiple-sessions" ||
+         action.id === "org.freedesktop.login1.power-off" ||
+         action.id === "org.freedesktop.login1.power-off-multiple-sessions")) {
+        return polkit.Result.YES;
+    }
+});

pkg/PKGBUILD

@@ -4,7 +4,7 @@
 # Maintainer: Dominik Kressler
 
 pkgname=moongreet-git
-pkgver=0.3.1.r5.g4c9b436
+pkgver=0.4.0.r7.g77b94a5
 pkgrel=1
 pkgdesc="A greetd greeter for Wayland with GTK4 and Layer Shell"
 arch=('x86_64')

resources/resources.gresource.xml

@@ -1,8 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <gresources>
   <gresource prefix="/dev/moonarch/moongreet">
-    <file>style.css</file>
-    <file>wallpaper.jpg</file>
-    <file>default-avatar.svg</file>
+    <file compressed="true">style.css</file>
+    <file compressed="true">default-avatar.svg</file>
   </gresource>
 </gresources>

resources/style.css

@@ -1,16 +1,16 @@
 /* ABOUTME: GTK4 CSS stylesheet for the Moongreet greeter. */
-/* ABOUTME: Defines styling for the login screen layout. */
+/* ABOUTME: Uses GTK theme colors for consistency with the active desktop theme. */
 
 /* Main window background */
 window.greeter {
-    background-color: #1a1a2e;
+    background-color: @theme_bg_color;
     background-size: cover;
     background-position: center;
 }
 
 /* Wallpaper-only window for secondary monitors */
 window.wallpaper {
-    background-color: #1a1a2e;
+    background-color: @theme_bg_color;
 }
 
 /* Central login area */
@@ -22,18 +22,18 @@ window.wallpaper {
 
 /* Round avatar image — size is set via set_size_request() in code */
 .avatar {
-    border-radius: 50%;
+    border-radius: 9999px;
     min-width: 128px;
     min-height: 128px;
     background-color: @theme_selected_bg_color;
-    border: 3px solid alpha(white, 0.3);
+    border: 3px solid alpha(@theme_fg_color, 0.3);
 }
 
 /* Username label */
 .username-label {
     font-size: 24px;
     font-weight: bold;
-    color: white;
+    color: @theme_fg_color;
     margin-top: 12px;
     margin-bottom: 40px;
 }
@@ -50,10 +50,17 @@ window.wallpaper {
 
 /* Error message label */
 .error-label {
-    color: #ff6b6b;
+    color: @error_color;
     font-size: 14px;
 }
 
+/* Fingerprint prompt label */
+.fingerprint-label {
+    color: alpha(@theme_fg_color, 0.6);
+    font-size: 13px;
+    margin-top: 8px;
+}
+
 /* User list on the bottom left */
 .user-list {
     background-color: transparent;
@@ -63,16 +70,16 @@ window.wallpaper {
 .user-list-item {
     padding: 8px 16px;
     border-radius: 8px;
-    color: white;
+    color: @theme_fg_color;
     font-size: 14px;
 }
 
 .user-list-item:hover {
-    background-color: alpha(white, 0.15);
+    background-color: alpha(@theme_fg_color, 0.15);
 }
 
 .user-list-item:selected {
-    background-color: alpha(white, 0.2);
+    background-color: alpha(@theme_fg_color, 0.2);
 }
 
 /* Power buttons on the bottom right */
@@ -81,12 +88,12 @@ window.wallpaper {
     min-height: 48px;
     padding: 0px;
     border-radius: 24px;
-    background-color: alpha(white, 0.1);
-    color: white;
+    background-color: alpha(@theme_fg_color, 0.1);
+    color: @theme_fg_color;
     border: none;
     margin: 4px;
 }
 
 .power-button:hover {
-    background-color: alpha(white, 0.25);
+    background-color: alpha(@theme_fg_color, 0.25);
 }

src/config.rs

@@ -6,7 +6,6 @@ use std::fs;
 use std::path::{Path, PathBuf};
 
 const MOONARCH_WALLPAPER: &str = "/usr/share/moonarch/wallpaper.jpg";
-const GRESOURCE_PREFIX: &str = "/dev/moonarch/moongreet";
 
 /// Default config search path: system-wide config.
 fn default_config_paths() -> Vec<PathBuf> {
@@ -26,14 +25,28 @@ struct Appearance {
     background_blur: Option<f32>,
     #[serde(rename = "gtk-theme")]
     gtk_theme: Option<String>,
+    #[serde(rename = "fingerprint-enabled")]
+    fingerprint_enabled: Option<bool>,
 }
 
 /// Greeter configuration.
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone)]
 pub struct Config {
     pub background_path: Option<String>,
     pub background_blur: Option<f32>,
     pub gtk_theme: Option<String>,
+    pub fingerprint_enabled: bool,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Config {
+            background_path: None,
+            background_blur: None,
+            gtk_theme: None,
+            fingerprint_enabled: true,
+        }
+    }
 }
 
 /// Load config from TOML files. Later paths override earlier ones.
@@ -55,16 +68,29 @@ pub fn load_config(config_paths: Option<&[PathBuf]>) -> Config {
                                 if bg_path.is_absolute() {
                                     merged.background_path = Some(bg);
                                 } else if let Some(parent) = path.parent() {
-                                    merged.background_path =
-                                        Some(parent.join(&bg).to_string_lossy().to_string());
+                                    let joined = parent.join(&bg);
+                                    match joined.to_str() {
+                                        Some(s) => merged.background_path = Some(s.to_string()),
+                                        None => log::warn!(
+                                            "Ignoring non-UTF-8 background path: {}",
+                                            joined.display()
+                                        ),
                                     }
                                 }
-                            if appearance.background_blur.is_some() {
-                                merged.background_blur = appearance.background_blur;
+                            }
+                            if let Some(blur) = appearance.background_blur {
+                                if blur.is_finite() {
+                                    merged.background_blur = Some(blur.clamp(0.0, 200.0));
+                                } else {
+                                    log::warn!("Ignoring non-finite background-blur value");
+                                }
                             }
                             if appearance.gtk_theme.is_some() {
                                 merged.gtk_theme = appearance.gtk_theme;
                             }
+                            if let Some(fp) = appearance.fingerprint_enabled {
+                                merged.fingerprint_enabled = fp;
+                            }
                         }
                     }
                     Err(e) => {
@@ -78,38 +104,43 @@ pub fn load_config(config_paths: Option<&[PathBuf]>) -> Config {
         }
     }
 
-    log::debug!("Config result: background={:?}, blur={:?}, gtk_theme={:?}", merged.background_path, merged.background_blur, merged.gtk_theme);
+    log::debug!("Config result: background={:?}, blur={:?}, gtk_theme={:?}, fingerprint={}", merged.background_path, merged.background_blur, merged.gtk_theme, merged.fingerprint_enabled);
     merged
 }
 
 /// Resolve the wallpaper path using the fallback hierarchy.
 ///
-/// Priority: config background_path > Moonarch system default > gresource fallback.
-pub fn resolve_background_path(config: &Config) -> PathBuf {
+/// Priority: config background_path > Moonarch system default > None (GTK background color).
+pub fn resolve_background_path(config: &Config) -> Option<PathBuf> {
     resolve_background_path_with(config, Path::new(MOONARCH_WALLPAPER))
 }
 
 /// Resolve with configurable moonarch wallpaper path (for testing).
-pub fn resolve_background_path_with(config: &Config, moonarch_wallpaper: &Path) -> PathBuf {
-    // User-configured path
+pub fn resolve_background_path_with(config: &Config, moonarch_wallpaper: &Path) -> Option<PathBuf> {
+    // User-configured path — reject symlinks to prevent path traversal
     if let Some(ref bg) = config.background_path {
         let path = PathBuf::from(bg);
-        if path.is_file() {
+        if let Ok(meta) = path.symlink_metadata() {
+            if meta.is_file() && !meta.file_type().is_symlink() {
                 log::debug!("Wallpaper: using config path {}", path.display());
-            return path;
+                return Some(path);
             }
-        log::debug!("Wallpaper: config path {} not found, trying fallbacks", path.display());
+        }
+        log::debug!("Wallpaper: config path {} not usable, trying fallbacks", path.display());
     }
 
-    // Moonarch ecosystem default
-    if moonarch_wallpaper.is_file() {
+    // Moonarch ecosystem default — apply the same symlink rejection as the
+    // user-configured path for defense in depth. The fallback target is a
+    // system file, but the caller consumes the result via the same path.
+    if let Ok(meta) = moonarch_wallpaper.symlink_metadata() {
+        if meta.is_file() && !meta.file_type().is_symlink() {
             log::debug!("Wallpaper: using moonarch default {}", moonarch_wallpaper.display());
-        return moonarch_wallpaper.to_path_buf();
+            return Some(moonarch_wallpaper.to_path_buf());
+        }
     }
 
-    // GResource fallback path (loaded from compiled resources at runtime)
-    log::debug!("Wallpaper: using GResource fallback");
-    PathBuf::from(format!("{GRESOURCE_PREFIX}/wallpaper.jpg"))
+    log::debug!("Wallpaper: no wallpaper found, using GTK background color");
+    None
 }
 
 #[cfg(test)]
@@ -122,6 +153,7 @@ mod tests {
         assert!(config.background_path.is_none());
         assert!(config.background_blur.is_none());
         assert!(config.gtk_theme.is_none());
+        assert!(config.fingerprint_enabled);
     }
 
     #[test]
@@ -218,7 +250,7 @@ mod tests {
         };
         assert_eq!(
             resolve_background_path_with(&config, Path::new("/nonexistent")),
-            wallpaper
+            Some(wallpaper)
         );
     }
 
@@ -229,7 +261,7 @@ mod tests {
             ..Config::default()
         };
         let result = resolve_background_path_with(&config, Path::new("/nonexistent"));
-        assert!(result.to_str().unwrap().contains("moongreet"));
+        assert!(result.is_none());
     }
 
     #[test]
@@ -240,14 +272,72 @@ mod tests {
         let config = Config::default();
         assert_eq!(
             resolve_background_path_with(&config, &moonarch_wp),
-            moonarch_wp
+            Some(moonarch_wp)
         );
     }
 
     #[test]
-    fn resolve_uses_gresource_fallback_as_last_resort() {
+    fn resolve_returns_none_when_no_wallpaper_found() {
         let config = Config::default();
         let result = resolve_background_path_with(&config, Path::new("/nonexistent"));
-        assert!(result.to_str().unwrap().contains("wallpaper.jpg"));
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn load_config_fingerprint_enabled_default_true() {
+        let paths = vec![PathBuf::from("/nonexistent/moongreet.toml")];
+        let config = load_config(Some(&paths));
+        assert!(config.fingerprint_enabled);
+    }
+
+    #[test]
+    fn load_config_fingerprint_disabled() {
+        let dir = tempfile::tempdir().unwrap();
+        let conf = dir.path().join("moongreet.toml");
+        fs::write(&conf, "[appearance]\nfingerprint-enabled = false\n").unwrap();
+        let paths = vec![conf];
+        let config = load_config(Some(&paths));
+        assert!(!config.fingerprint_enabled);
+    }
+
+    // -- Blur validation tests --
+
+    #[test]
+    fn load_config_blur_clamped_to_max() {
+        let dir = tempfile::tempdir().unwrap();
+        let conf = dir.path().join("moongreet.toml");
+        fs::write(&conf, "[appearance]\nbackground-blur = 999.0\n").unwrap();
+        let config = load_config(Some(&[conf]));
+        assert_eq!(config.background_blur, Some(200.0));
+    }
+
+    #[test]
+    fn load_config_blur_negative_clamped_to_zero() {
+        let dir = tempfile::tempdir().unwrap();
+        let conf = dir.path().join("moongreet.toml");
+        fs::write(&conf, "[appearance]\nbackground-blur = -5.0\n").unwrap();
+        let config = load_config(Some(&[conf]));
+        assert_eq!(config.background_blur, Some(0.0));
+    }
+
+    #[test]
+    fn load_config_blur_nan_rejected() {
+        let dir = tempfile::tempdir().unwrap();
+        let conf = dir.path().join("moongreet.toml");
+        // TOML doesn't support NaN literals, but the parser may return NaN for nan
+        fs::write(&conf, "[appearance]\nbackground-blur = nan\n").unwrap();
+        let config = load_config(Some(&[conf]));
+        // nan is not valid TOML float, so the whole config parse fails → no blur
+        assert!(config.background_blur.is_none());
+    }
+
+    #[test]
+    fn load_config_blur_inf_rejected() {
+        let dir = tempfile::tempdir().unwrap();
+        let conf = dir.path().join("moongreet.toml");
+        fs::write(&conf, "[appearance]\nbackground-blur = inf\n").unwrap();
+        let config = load_config(Some(&[conf]));
+        // inf is valid TOML → parsed as f32::INFINITY → rejected by is_finite() guard
+        assert!(config.background_blur.is_none());
     }
 }

src/fingerprint.rs

@@ -0,0 +1,142 @@
+// ABOUTME: fprintd D-Bus probe for fingerprint device availability.
+// ABOUTME: Checks if fprintd is running and the user has enrolled fingerprints.
+
+use gio::prelude::*;
+use gtk4::gio;
+
+const FPRINTD_BUS_NAME: &str = "net.reactivated.Fprint";
+const FPRINTD_MANAGER_PATH: &str = "/net/reactivated/Fprint/Manager";
+const FPRINTD_MANAGER_IFACE: &str = "net.reactivated.Fprint.Manager";
+const FPRINTD_DEVICE_IFACE: &str = "net.reactivated.Fprint.Device";
+
+const DBUS_TIMEOUT_MS: i32 = 3000;
+const FPRINTD_DEVICE_PREFIX: &str = "/net/reactivated/Fprint/Device/";
+
+/// Lightweight fprintd probe — detects device availability and finger enrollment.
+/// Does NOT perform verification (that happens through greetd/PAM).
+pub struct FingerprintProbe {
+    device_proxy: Option<gio::DBusProxy>,
+}
+
+impl FingerprintProbe {
+    /// Create a probe without any D-Bus connections.
+    /// Call `init_async().await` to connect to fprintd.
+    pub fn new() -> Self {
+        FingerprintProbe {
+            device_proxy: None,
+        }
+    }
+
+    /// Connect to fprintd on the system bus and discover the default device.
+    pub async fn init_async(&mut self) {
+        let manager = match gio::DBusProxy::for_bus_future(
+            gio::BusType::System,
+            gio::DBusProxyFlags::NONE,
+            None,
+            FPRINTD_BUS_NAME,
+            FPRINTD_MANAGER_PATH,
+            FPRINTD_MANAGER_IFACE,
+        )
+        .await
+        {
+            Ok(m) => m,
+            Err(e) => {
+                log::debug!("fprintd manager not available: {e}");
+                return;
+            }
+        };
+
+        let result = match manager
+            .call_future("GetDefaultDevice", None, gio::DBusCallFlags::NONE, DBUS_TIMEOUT_MS)
+            .await
+        {
+            Ok(r) => r,
+            Err(e) => {
+                log::debug!("fprintd GetDefaultDevice failed: {e}");
+                return;
+            }
+        };
+
+        let device_path = match result.child_value(0).get::<String>() {
+            Some(p) => p,
+            None => {
+                log::debug!("fprintd: unexpected GetDefaultDevice response type");
+                return;
+            }
+        };
+        if device_path.is_empty() {
+            return;
+        }
+        if !device_path.starts_with(FPRINTD_DEVICE_PREFIX) {
+            log::warn!("Unexpected fprintd device path: {device_path}");
+            return;
+        }
+
+        match gio::DBusProxy::for_bus_future(
+            gio::BusType::System,
+            gio::DBusProxyFlags::NONE,
+            None,
+            FPRINTD_BUS_NAME,
+            &device_path,
+            FPRINTD_DEVICE_IFACE,
+        )
+        .await
+        {
+            Ok(proxy) => {
+                self.device_proxy = Some(proxy);
+            }
+            Err(e) => {
+                log::debug!("fprintd device proxy failed: {e}");
+            }
+        }
+    }
+
+    /// Check if the user has enrolled fingerprints on the default device.
+    /// Returns false if fprintd is unavailable or the user has no enrollments.
+    pub async fn is_available_async(&self, username: &str) -> bool {
+        let proxy = match &self.device_proxy {
+            Some(p) => p,
+            None => return false,
+        };
+
+        let args = glib::Variant::from((&username,));
+        match proxy
+            .call_future(
+                "ListEnrolledFingers",
+                Some(&args),
+                gio::DBusCallFlags::NONE,
+                DBUS_TIMEOUT_MS,
+            )
+            .await
+        {
+            Ok(result) => match result.child_value(0).get::<Vec<String>>() {
+                Some(fingers) => !fingers.is_empty(),
+                None => {
+                    log::debug!("fprintd: unexpected ListEnrolledFingers response type");
+                    false
+                }
+            },
+            Err(_) => false,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn new_probe_has_no_device() {
+        let probe = FingerprintProbe::new();
+        assert!(probe.device_proxy.is_none());
+    }
+
+    #[test]
+    fn constants_are_defined() {
+        assert!(!FPRINTD_BUS_NAME.is_empty());
+        assert!(!FPRINTD_MANAGER_PATH.is_empty());
+        assert!(!FPRINTD_MANAGER_IFACE.is_empty());
+        assert!(!FPRINTD_DEVICE_IFACE.is_empty());
+        assert!(DBUS_TIMEOUT_MS > 0);
+    }
+}

src/i18n.rs

@@ -4,6 +4,7 @@
 use std::env;
 use std::fs;
 use std::path::Path;
+use std::sync::OnceLock;
 
 const DEFAULT_LOCALE_CONF: &str = "/etc/locale.conf";
 
@@ -19,11 +20,9 @@ pub struct Strings {
     pub no_session_selected: &'static str,
     pub greetd_sock_not_set: &'static str,
     pub greetd_sock_not_absolute: &'static str,
-    pub greetd_sock_not_socket: &'static str,
-    pub greetd_sock_unreachable: &'static str,
     pub auth_failed: &'static str,
     pub wrong_password: &'static str,
-    pub multi_stage_unsupported: &'static str,
+    pub fingerprint_prompt: &'static str,
     pub invalid_session_command: &'static str,
     pub session_start_failed: &'static str,
     pub reboot_failed: &'static str,
@@ -43,11 +42,9 @@ const STRINGS_DE: Strings = Strings {
     no_session_selected: "Keine Session ausgewählt",
     greetd_sock_not_set: "GREETD_SOCK nicht gesetzt",
     greetd_sock_not_absolute: "GREETD_SOCK ist kein absoluter Pfad",
-    greetd_sock_not_socket: "GREETD_SOCK zeigt nicht auf einen Socket",
-    greetd_sock_unreachable: "GREETD_SOCK nicht erreichbar",
     auth_failed: "Authentifizierung fehlgeschlagen",
     wrong_password: "Falsches Passwort",
-    multi_stage_unsupported: "Mehrstufige Authentifizierung wird nicht unterstützt",
+    fingerprint_prompt: "Fingerabdruck auflegen oder Passwort eingeben",
     invalid_session_command: "Ungültiger Session-Befehl",
     session_start_failed: "Session konnte nicht gestartet werden",
     reboot_failed: "Neustart fehlgeschlagen",
@@ -65,11 +62,9 @@ const STRINGS_EN: Strings = Strings {
     no_session_selected: "No session selected",
     greetd_sock_not_set: "GREETD_SOCK not set",
     greetd_sock_not_absolute: "GREETD_SOCK is not an absolute path",
-    greetd_sock_not_socket: "GREETD_SOCK does not point to a socket",
-    greetd_sock_unreachable: "GREETD_SOCK unreachable",
     auth_failed: "Authentication failed",
     wrong_password: "Wrong password",
-    multi_stage_unsupported: "Multi-stage authentication is not supported",
+    fingerprint_prompt: "Place finger on reader or enter password",
     invalid_session_command: "Invalid session command",
     session_start_failed: "Failed to start session",
     reboot_failed: "Reboot failed",
@@ -135,14 +130,17 @@ pub fn detect_locale() -> String {
     result
 }
 
+/// Cached locale — detected once, reused for the lifetime of the process.
+static CACHED_LOCALE: OnceLock<String> = OnceLock::new();
+
 /// Return the string table for the given locale, defaulting to English.
 pub fn load_strings(locale: Option<&str>) -> &'static Strings {
     let locale = match locale {
-        Some(l) => l.to_string(),
-        None => detect_locale(),
+        Some(l) => l,
+        None => CACHED_LOCALE.get_or_init(detect_locale),
     };
 
-    match locale.as_str() {
+    match locale {
         "de" => &STRINGS_DE,
         _ => &STRINGS_EN,
     }
@@ -282,11 +280,16 @@ mod tests {
             assert!(!s.greetd_sock_not_set.is_empty(), "{locale}: greetd_sock_not_set");
             assert!(!s.auth_failed.is_empty(), "{locale}: auth_failed");
             assert!(!s.wrong_password.is_empty(), "{locale}: wrong_password");
+            assert!(!s.fingerprint_prompt.is_empty(), "{locale}: fingerprint_prompt");
             assert!(!s.reboot_failed.is_empty(), "{locale}: reboot_failed");
             assert!(!s.shutdown_failed.is_empty(), "{locale}: shutdown_failed");
             assert!(!s.faillock_attempts_remaining.is_empty(), "{locale}: faillock_attempts_remaining");
             assert!(!s.faillock_locked.is_empty(), "{locale}: faillock_locked");
             assert!(!s.unexpected_greetd_response.is_empty(), "{locale}: unexpected_greetd_response");
+            assert!(!s.greetd_sock_not_absolute.is_empty(), "{locale}: greetd_sock_not_absolute");
+            assert!(!s.invalid_session_command.is_empty(), "{locale}: invalid_session_command");
+            assert!(!s.session_start_failed.is_empty(), "{locale}: session_start_failed");
+            assert!(!s.socket_error.is_empty(), "{locale}: socket_error");
         }
     }
 

src/main.rs

@@ -2,6 +2,7 @@
 // ABOUTME: Sets up GTK Application, Layer Shell, CSS, and multi-monitor windows.
 
 mod config;
+mod fingerprint;
 mod greeter;
 mod i18n;
 mod ipc;
@@ -10,16 +11,18 @@ mod sessions;
 mod users;
 
 use gdk4 as gdk;
+use glib::clone;
 use gtk4::prelude::*;
 use gtk4::{self as gtk, gio};
 use gtk4_layer_shell::LayerShell;
+use std::rc::Rc;
 fn load_css(display: &gdk::Display) {
     let css_provider = gtk::CssProvider::new();
     css_provider.load_from_resource("/dev/moonarch/moongreet/style.css");
     gtk::style_context_add_provider_for_display(
         display,
         &css_provider,
-        gtk::STYLE_PROVIDER_PRIORITY_APPLICATION,
+        gtk::STYLE_PROVIDER_PRIORITY_USER,
     );
 }
 
@@ -51,43 +54,65 @@ fn activate(app: &gtk::Application) {
 
     // Load config and resolve wallpaper
     let config = config::load_config(None);
-    let bg_path = config::resolve_background_path(&config);
-    log::debug!("Background path: {}", bg_path.display());
+    let bg_texture = config::resolve_background_path(&config)
+        .and_then(|path| {
+            log::debug!("Background path: {}", path.display());
+            greeter::load_background_texture(&path)
+        });
 
-    // Load background texture once — shared across all windows
-    // Blur is applied on the GPU via GskBlurNode at widget realization time.
-    let bg_texture = greeter::load_background_texture(&bg_path);
-    if bg_texture.is_none() {
-        log::error!("Failed to load background texture — greeter will start without wallpaper");
-    }
+    let blur_cache = std::rc::Rc::new(std::cell::RefCell::new(None));
 
     let use_layer_shell = std::env::var("MOONGREET_NO_LAYER_SHELL").is_err();
     log::debug!("Layer shell: {use_layer_shell}");
 
-    // Main greeter window (login UI) — compositor picks focused monitor
-    let greeter_window = greeter::create_greeter_window(bg_texture.as_ref(), &config, app);
     if use_layer_shell {
-        setup_layer_shell(&greeter_window, true, gtk4_layer_shell::Layer::Top);
-    }
-    greeter_window.present();
-
-    // Wallpaper-only windows on all monitors (only with layer shell)
-    if use_layer_shell
-        && let Some(ref texture) = bg_texture
-    {
+        // One greeter window per monitor — only the first gets keyboard input
         let monitors = display.monitors();
         log::debug!("Monitor count: {}", monitors.n_items());
+        let mut first = true;
         for i in 0..monitors.n_items() {
             if let Some(monitor) = monitors
                 .item(i)
                 .and_then(|obj| obj.downcast::<gdk::Monitor>().ok())
             {
-                let wallpaper = greeter::create_wallpaper_window(texture, config.background_blur, app);
-                setup_layer_shell(&wallpaper, false, gtk4_layer_shell::Layer::Bottom);
-                wallpaper.set_monitor(Some(&monitor));
-                wallpaper.present();
+                let window = greeter::create_greeter_window(bg_texture.as_ref(), &config, &blur_cache, app);
+                setup_layer_shell(&window, first, gtk4_layer_shell::Layer::Top);
+                window.set_monitor(Some(&monitor));
+                window.present();
+                first = false;
             }
         }
+
+        // Handle monitor hotplug — create greeter windows for newly added monitors
+        // (without keyboard, since the primary monitor already has it)
+        let bg_texture = Rc::new(bg_texture);
+        let config = Rc::new(config);
+        monitors.connect_items_changed(clone!(
+            #[weak]
+            app,
+            #[strong]
+            blur_cache,
+            move |list, position, _removed, added| {
+                for i in position..position + added {
+                    if let Some(monitor) = list
+                        .item(i)
+                        .and_then(|obj| obj.downcast::<gdk::Monitor>().ok())
+                    {
+                        log::debug!("Monitor hotplug: creating greeter window");
+                        let window = greeter::create_greeter_window(
+                            bg_texture.as_ref().as_ref(), &config, &blur_cache, &app,
+                        );
+                        setup_layer_shell(&window, false, gtk4_layer_shell::Layer::Top);
+                        window.set_monitor(Some(&monitor));
+                        window.present();
+                    }
+                }
+            }
+        ));
+    } else {
+        // No layer shell — single window for development
+        let greeter_window = greeter::create_greeter_window(bg_texture.as_ref(), &config, &blur_cache, app);
+        greeter_window.present();
     }
 }
 
@@ -102,10 +127,12 @@ fn setup_logging() {
             eprintln!("Failed to create journal logger: {e}");
         }
     }
-    let level = if std::env::var("MOONGREET_DEBUG").is_ok() {
-        log::LevelFilter::Debug
-    } else {
-        log::LevelFilter::Info
+    // Require MOONGREET_DEBUG=1 to raise verbosity. Mere presence (e.g. an
+    // empty value in a session-setup script) must not escalate the journal
+    // to Debug, which leaks socket paths, usernames, and auth round counts.
+    let level = match std::env::var("MOONGREET_DEBUG").ok().as_deref() {
+        Some("1") => log::LevelFilter::Debug,
+        _ => log::LevelFilter::Info,
     };
     log::set_max_level(level);
 }

src/power.rs

@@ -2,11 +2,18 @@
 // ABOUTME: Wrappers around system commands for the greeter UI.
 
 use std::fmt;
-use std::process::Command;
+use std::io::Read;
+use std::process::{Command, Stdio};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+
+const POWER_TIMEOUT: Duration = Duration::from_secs(30);
 
 #[derive(Debug)]
 pub enum PowerError {
     CommandFailed { action: &'static str, message: String },
+    Timeout { action: &'static str },
 }
 
 impl fmt::Display for PowerError {
@@ -15,41 +22,81 @@ impl fmt::Display for PowerError {
             PowerError::CommandFailed { action, message } => {
                 write!(f, "{action} failed: {message}")
             }
+            PowerError::Timeout { action } => {
+                write!(f, "{action} timed out")
+            }
         }
     }
 }
 
 impl std::error::Error for PowerError {}
 
-/// Run a command and return a PowerError on failure.
+/// Run a command with timeout and return a PowerError on failure.
+///
+/// Uses blocking `child.wait()` with a separate timeout thread that sends
+/// SIGKILL after POWER_TIMEOUT. This runs inside `gio::spawn_blocking`,
+/// so blocking is expected.
 fn run_command(action: &'static str, program: &str, args: &[&str]) -> Result<(), PowerError> {
     log::debug!("Power action: {action} ({program} {args:?})");
-    let child = Command::new(program)
+    let mut child = Command::new(program)
         .args(args)
+        // stdout is never read; piping without draining would deadlock on any
+        // command that writes more than one OS pipe buffer before wait() returns.
+        .stdout(Stdio::null())
+        .stderr(Stdio::piped())
         .spawn()
         .map_err(|e| PowerError::CommandFailed {
             action,
             message: e.to_string(),
         })?;
 
-    let output = child
-        .wait_with_output()
-        .map_err(|e| PowerError::CommandFailed {
+    let child_pid = nix::unistd::Pid::from_raw(child.id() as i32);
+    let done = Arc::new(AtomicBool::new(false));
+    let done_clone = done.clone();
+
+    let timeout_thread = std::thread::spawn(move || {
+        let interval = Duration::from_millis(100);
+        let mut elapsed = Duration::ZERO;
+        while elapsed < POWER_TIMEOUT {
+            std::thread::sleep(interval);
+            if done_clone.load(Ordering::Relaxed) {
+                return;
+            }
+            elapsed += interval;
+        }
+        // ESRCH if the process already exited — harmless
+        let _ = nix::sys::signal::kill(child_pid, nix::sys::signal::Signal::SIGKILL);
+    });
+
+    let status = child.wait().map_err(|e| PowerError::CommandFailed {
         action,
         message: e.to_string(),
     })?;
 
-    if output.status.success() {
-        log::debug!("Power action {action} completed successfully");
+    done.store(true, Ordering::Relaxed);
+    let _ = timeout_thread.join();
+
+    if status.success() {
+        log::debug!("Power action {action} completed");
+        Ok(())
     } else {
-        let stderr = String::from_utf8_lossy(&output.stderr);
-        return Err(PowerError::CommandFailed {
-            action,
-            message: format!("exit code {}: {}", output.status, stderr.trim()),
-        });
+        #[cfg(unix)]
+        {
+            use std::os::unix::process::ExitStatusExt;
+            if status.signal() == Some(9) {
+                return Err(PowerError::Timeout { action });
+            }
         }
 
-    Ok(())
+        let mut stderr_buf = String::new();
+        if let Some(mut stderr) = child.stderr.take() {
+            let _ = stderr.read_to_string(&mut stderr_buf);
+        }
+        Err(PowerError::CommandFailed {
+            action,
+            message: format!("exit code {}: {}", status, stderr_buf.trim()),
+        })
+    }
 }
 
 /// Reboot the system via loginctl.
@@ -75,6 +122,12 @@ mod tests {
         assert_eq!(err.to_string(), "reboot failed: No such file or directory");
     }
 
+    #[test]
+    fn power_error_timeout_display() {
+        let err = PowerError::Timeout { action: "shutdown" };
+        assert_eq!(err.to_string(), "shutdown timed out");
+    }
+
     #[test]
     fn run_command_returns_error_for_missing_binary() {
         let result = run_command("test", "nonexistent-binary-xyz", &[]);
@@ -99,7 +152,7 @@ mod tests {
 
     #[test]
     fn run_command_passes_args() {
-        let result = run_command("test", "true", &["--ignored-arg"]);
+        let result = run_command("test", "echo", &["hello", "world"]);
         assert!(result.is_ok());
     }
 }

src/sessions.rs

@@ -23,6 +23,8 @@ fn parse_desktop_file(path: &Path, session_type: &str) -> Option<Session> {
     let mut in_section = false;
     let mut name: Option<String> = None;
     let mut exec_cmd: Option<String> = None;
+    let mut hidden = false;
+    let mut no_display = false;
 
     for line in content.lines() {
         let line = line.trim();
@@ -36,15 +38,24 @@ fn parse_desktop_file(path: &Path, session_type: &str) -> Option<Session> {
             continue;
         }
 
-        if let Some(value) = line.strip_prefix("Name=") {
-            if name.is_none() {
+        if let Some(value) = line.strip_prefix("Name=")
+            && name.is_none()
+        {
             name = Some(value.to_string());
-            }
-        } else if let Some(value) = line.strip_prefix("Exec=") {
-            if exec_cmd.is_none() {
+        } else if let Some(value) = line.strip_prefix("Exec=")
+            && exec_cmd.is_none()
+        {
             exec_cmd = Some(value.to_string());
+        } else if let Some(value) = line.strip_prefix("Hidden=") {
+            hidden = value.eq_ignore_ascii_case("true");
+        } else if let Some(value) = line.strip_prefix("NoDisplay=") {
+            no_display = value.eq_ignore_ascii_case("true");
         }
     }
+
+    if hidden || no_display {
+        log::debug!("Skipping {}: Hidden/NoDisplay entry", path.display());
+        return None;
     }
 
     let name = name.filter(|s| !s.is_empty());

src/users.rs

@@ -70,7 +70,7 @@ pub fn get_users(passwd_path: Option<&Path>) -> Vec<User> {
             Err(_) => continue,
         };
 
-        if uid < MIN_UID || uid > MAX_UID {
+        if !(MIN_UID..=MAX_UID).contains(&uid) {
             continue;
         }
         if NOLOGIN_SHELLS.contains(&shell) {
@@ -94,7 +94,7 @@ pub fn get_users(passwd_path: Option<&Path>) -> Vec<User> {
     users
 }
 
-/// Find avatar for a user: AccountsService icon > ~/.face > None.
+/// Find avatar for a user: ~/.face > AccountsService icon > None.
 /// Rejects symlinks to prevent path traversal.
 pub fn get_avatar_path(username: &str, home: &Path) -> Option<PathBuf> {
     get_avatar_path_with(username, home, Path::new(DEFAULT_ACCOUNTSSERVICE_DIR))
@@ -106,30 +106,30 @@ pub fn get_avatar_path_with(
     home: &Path,
     accountsservice_dir: &Path,
 ) -> Option<PathBuf> {
-    // AccountsService icon takes priority
+    // ~/.face takes priority (consistent with moonlock/moonset)
+    let face = home.join(".face");
+    if let Ok(meta) = face.symlink_metadata() {
+        if meta.file_type().is_symlink() {
+            log::warn!("Rejecting symlink avatar for {username}: {}", face.display());
+        } else if meta.is_file() {
+            log::debug!("Avatar for {username}: ~/.face {}", face.display());
+            return Some(face);
+        }
+    }
+
+    // AccountsService icon fallback
     if accountsservice_dir.exists() {
         let icon = accountsservice_dir.join(username);
         if let Ok(meta) = icon.symlink_metadata() {
             if meta.file_type().is_symlink() {
                 log::warn!("Rejecting symlink avatar for {username}: {}", icon.display());
-            } else {
+            } else if meta.is_file() {
                 log::debug!("Avatar for {username}: AccountsService {}", icon.display());
                 return Some(icon);
             }
         }
     }
 
-    // ~/.face fallback
-    let face = home.join(".face");
-    if let Ok(meta) = face.symlink_metadata() {
-        if meta.file_type().is_symlink() {
-            log::warn!("Rejecting symlink avatar for {username}: {}", face.display());
-        } else {
-            log::debug!("Avatar for {username}: ~/.face {}", face.display());
-            return Some(face);
-        }
-    }
-
     log::debug!("No avatar found for {username}");
     None
 }
@@ -248,7 +248,7 @@ mod tests {
     }
 
     #[test]
-    fn accountsservice_icon_takes_priority() {
+    fn face_file_takes_priority_over_accountsservice() {
         let dir = tempfile::tempdir().unwrap();
         let icons_dir = dir.path().join("icons");
         fs::create_dir(&icons_dir).unwrap();
@@ -261,7 +261,7 @@ mod tests {
         fs::write(&face, "fake face").unwrap();
 
         let path = get_avatar_path_with("testuser", &home, &icons_dir);
-        assert_eq!(path, Some(icon));
+        assert_eq!(path, Some(face));
     }
 
     #[test]