fix: audit LOW fixes — docs, rustdoc, scope, debug gate, lto fat (v0.6.12)

- Update CLAUDE.md and README.md to reflect the blur range [0,200] that
  the code has clamped to since v0.6.8.
- Move the // SYNC: comment above the /// doc on MAX_BLUR_DIMENSION so
  rustdoc renders one coherent paragraph instead of a truncated sentence.
- Narrow check_account visibility to pub(crate) and document the caller
  precondition (username must come from users::get_current_user()).
- Gate MOONLOCK_DEBUG behind #[cfg(debug_assertions)]. Release builds
  always run at LevelFilter::Info so a session script cannot escalate
  journal verbosity to leak fprintd / D-Bus internals.
- Document why pam_setcred is deliberately not called in authenticate().
- Release profile: lto = "fat" instead of "thin" — doubles release build
  time for better cross-crate inlining on the auth + i18n hot paths.

CLAUDE.md

@@ -1,7 +1,5 @@
 # Moonlock
 
-**Name**: Nyx (Göttin der Nacht — passend zum Lockscreen, der den Bildschirm verdunkelt)
-
 ## Projekt
 
 Moonlock ist ein sicherer Wayland-Lockscreen, gebaut mit Rust + gtk4-rs + ext-session-lock-v1.
@@ -42,7 +40,7 @@ LD_PRELOAD=/usr/lib/libgtk4-layer-shell.so ./target/release/moonlock
 - `users.rs` — Aktuellen User via nix getuid, Avatar-Loading mit Symlink-Rejection
 - `power.rs` — Reboot/Shutdown via /usr/bin/systemctl
 - `i18n.rs` — Locale-Erkennung (OnceLock-cached) und String-Tabellen (DE/EN), faillock_warning mit konfigurierbarem max_attempts
-- `config.rs` — TOML-Config (background_path, background_blur clamped [0,100], fingerprint_enabled als Option<bool>) + Wallpaper-Fallback + Symlink-Rejection via symlink_metadata + Parse-Error-Logging
+- `config.rs` — TOML-Config (background_path, background_blur clamped [0,200], fingerprint_enabled als Option<bool>) + Wallpaper-Fallback + Symlink-Rejection via symlink_metadata + Parse-Error-Logging
 - `lockscreen.rs` — GTK4 UI via LockscreenHandles, PAM-Auth via gio::spawn_blocking mit 30s Timeout und Generation Counter, FP-Label/Start separat verdrahtet mit pam_acct_mgmt-Check und auto-resume, Zeroizing<String> für Passwort, Power-Confirm, GPU-Blur via GskBlurNode (Downscale auf max 1920px), Blur/Avatar-Cache für Multi-Monitor
 - `main.rs` — Entry Point, Panic-Hook (vor Logging), Root-Check, ext-session-lock-v1 (Pflicht in Release), Monitor-Hotplug via `connect_monitor`-Signal (v1_2), shared Blur/Avatar-Caches in Rc, systemd-Journal-Logging, Debug-Level per `MOONLOCK_DEBUG` Env-Var, async fprintd-Init nach window.present()
 

Cargo.lock

@@ -575,7 +575,7 @@ dependencies = [
 
 [[package]]
 name = "moonlock"
-version = "0.6.8"
+version = "0.6.12"
 dependencies = [
  "gdk-pixbuf",
  "gdk4",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moonlock"
-version = "0.6.9"
+version = "0.6.12"
 edition = "2024"
 description = "A secure Wayland lockscreen with GTK4, PAM and fingerprint support"
 license = "MIT"
@@ -28,6 +28,6 @@ tempfile = "3"
 glib-build-tools = "0.22"
 
 [profile.release]
-lto = "thin"
+lto = "fat"
 codegen-units = 1
 strip = true

DECISIONS.md

@@ -2,65 +2,86 @@
 
 Architectural and design decisions for Moonlock, in reverse chronological order.
 
+## 2026-04-24 – Audit LOW fixes: docs, rustdoc, check_account scope, debug gating, lto fat (v0.6.12)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Six LOW findings cleared in a single pass. (1) Docs referenced the old `[0,100]` blur range; code clamps `[0,200]` since v0.6.8. (2) The `MAX_BLUR_DIMENSION` doc comment was split by a `// SYNC:` block, producing a truncated sentence in rustdoc. (3) `check_account` was `pub` and relied on callers only ever passing `getuid()`-derived usernames; the contract was not enforced by the type system. (4) `MOONLOCK_DEBUG` env var flipped log verbosity to Debug in release builds, letting a compromised session script escalate journal noise about fprintd / D-Bus. (5) `pam_setcred` absence was undocumented. (6) `[profile.release]` used `lto = "thin"` — fine for most crates, but for a latency-critical auth binary compiled once per release, fat LTO's extra cross-crate inlining is worth the ~1 min build hit.
+- **Tradeoffs**: `lto = "fat"` roughly doubles release build time (~30 s → ~60 s) for slightly better inlining across PAM FFI wrappers and the i18n/status paths. `#[cfg(debug_assertions)]` on the debug-level selector means you have to run a debug build to raise log level — inconvenient for live troubleshooting, but aligned with the security-first posture.
+- **How**: (1) `CLAUDE.md` + `README.md` updated to `[0,200]`. (2) `// SYNC:` block moved above the `///` doc so rustdoc renders one coherent paragraph. (3) `check_account` visibility narrowed to `pub(crate)` with a `Precondition` paragraph explaining the username contract. (4) Debug-level selection wrapped in `#[cfg(debug_assertions)]`; release builds always run at `LevelFilter::Info`. (5) Added a comment block in `authenticate()` documenting why `pam_setcred` is deliberately absent and where it would hook in if needed. (6) `lto = "fat"` in `Cargo.toml`.
+
+## 2026-04-24 – Audit MEDIUM fixes: D-Bus cleanup race, TOCTOU open, FP reset, GTK entry clear (v0.6.11)
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Second round after the HIGH fixes, addressing the four MEDIUM findings. (1) `cleanup_dbus` spawned VerifyStop + Release as fire-and-forget, then `resume_async` called Claim after only a 2 s timeout — shorter than the 3 s D-Bus timeout, so on a slow bus the Claim could race the Release and fprintd would reject it, leaving the FP listener permanently dead. (2) `load_background_texture` relied on the caller's `symlink_metadata` check, re-opening the path via `gdk::Texture::from_file` — a classic TOCTOU window. (3) `resume_async` unconditionally reset `failed_attempts`, allowing an attacker with sensor control to evade the 10-attempt cap by cycling verify-match → `check_account` fail → resume. (4) The GTK `PasswordEntry` buffer was only cleared on timeout or auth failure, leaving the password in GLib malloc'd memory longer than necessary.
+- **Tradeoffs**: The D-Bus cleanup is now split into a synchronous helper (`take_cleanup_proxy` — signal disconnect + flag clear) and an async helper (`perform_dbus_cleanup` — VerifyStop + Release), so `resume_async` can await the release while `stop()` stays fire-and-forget. Dropping the `failed_attempts` reset means a flaky sensor could reach 10 failures faster, but the correct remedy is a new lock session (construction) rather than a reset that also helps attackers.
+- **How**: (1) Split `cleanup_dbus` into `take_cleanup_proxy()` (sync) + `perform_dbus_cleanup(proxy)` (async). `resume_async` now awaits `perform_dbus_cleanup` before `begin_verification`. `stop()` still spawns the cleanup fire-and-forget. (2) `load_background_texture` opens with `O_NOFOLLOW` via `std::fs::OpenOptions::custom_flags`, reads to bytes, and builds the texture via `gdk::Texture::from_bytes`. (3) Removed `listener.borrow_mut().failed_attempts = 0` from `resume_async`. (4) `password_entry.set_text("")` now fires right after the `Zeroizing::new(entry.text().to_string())` extraction, shortening the GTK-side window.
+
+## 2026-04-24 – Audit fixes: RefCell borrow across await, async avatar decode
+
+- **Who**: ClaudeCode, Dom
+- **Why**: Triple audit found two HIGH issues. (1) `init_fingerprint_async` held a `RefCell` immutable borrow across `is_available_async().await` — a concurrent `connect_monitor` signal (hotplug / suspend-resume) invoking `borrow_mut()` during the await would panic. (2) `set_avatar_from_file` decoded avatars synchronously via `Pixbuf::from_file_at_scale`, blocking the GTK main thread inside the `connect_monitor` handler. With `MAX_AVATAR_FILE_SIZE` at 10 MB the worst-case stall was 200–500 ms on monitor hotplug.
+- **Tradeoffs**: Avatar is shown as the symbolic default icon for a brief window while decoding completes. Wallpaper stays synchronous because `connect_monitor` fires during `lock()` and needs the texture already present (see 2026-04-09).
+- **How**: (1) Extract `username` into a local `String` in `init_fingerprint_async`, drop the borrow before the await, re-borrow in a new scope after — no awaits inside the second borrow, so hotplug during signal setup is safe. (2) `set_avatar_from_file` now uses `gio::File::read_future` + `Pixbuf::from_stream_at_scale_future` for async I/O and decode. The default icon is shown immediately; the decoded texture replaces it when ready. `Pixbuf` itself is `!Send`, so `gio::spawn_blocking` does not apply — the GIO async stream loader keeps the `Pixbuf` on the main thread while the kernel does the I/O asynchronously.
+
 ## 2026-04-09 – Monitor hotplug via connect_monitor signal
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: moonlock crashed with segfault in libgtk-4.so after suspend/resume — HDMI monitor disconnect/reconnect invalidated GDK monitor objects, and the statically created windows referenced destroyed surfaces. Crash at consistent GTK4 offset (0x278 NULL dereference), 3x reproduced.
 - **Tradeoffs**: Wallpaper texture now loaded before `lock()` instead of after (connect_monitor fires during lock() and needs the texture). Local JPEG loading is fast enough that the delay is negligible. Shared state moved to Rc's for the signal closure — slightly more indirection but necessary for dynamic window creation.
 - **How**: (1) Bump gtk4-session-lock feature from `v1_1` to `v1_2` to enable `Instance::connect_monitor`. (2) Replace manual monitor iteration with `lock.connect_monitor()` signal handler that creates windows on demand. (3) Signal fires once per existing monitor at `lock()` and again on hotplug. (4) Windows auto-unmap when their monitor disappears (ext-session-lock-v1 guarantee). (5) Fingerprint listener published to shared Rc so hotplugged monitors get FP labels.
 
 ## 2026-03-31 – Fourth audit: peek icon, blur limit, GResource compression, sync markers
 
-- **Who**: Ragnar, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Fourth triple audit found blur limit inconsistency (moonlock 0–100 vs moongreet/moonset 0–200), missing GResource compression, peek icon inconsistency, and duplicated code without sync markers.
 - **Tradeoffs**: Peek icon enabled in lockscreen — user decision favoring UX consistency over shoulder-surfing protection. Acceptable for single-user desktop. Blur limit raised to 200 for ecosystem consistency.
 - **How**: (1) `show_peek_icon(true)` in lockscreen password entry. (2) `clamp(0.0, 200.0)` for blur in config.rs. (3) `compressed="true"` on CSS/SVG GResource entries. (4) SYNC comments on duplicated blur/background functions pointing to moongreet and moonset.
 
 ## 2026-03-30 – Third audit: blur offset, lock-before-IO, FP signal lifecycle, TOCTOU
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Third triple audit (quality, performance, security) found: blur padding offset rendering texture at (0,0) instead of (-pad,-pad) causing edge darkening on left/top (BUG), wallpaper disk I/O blocking before lock() extending the unsecured window (PERF/SEC), signal handler duplication on resume_async (SEC), failed_attempts not reset on FP resume (SEC), unknown VerifyStatus with done=false hanging FP listener (SEC), TOCTOU in is_file+is_symlink checks (SEC), dead code in faillock_warning (QUALITY), unbounded blur sigma (SEC).
 - **Tradeoffs**: Wallpaper loads after lock() — screen briefly shows without wallpaper until texture is ready. Acceptable: security > aesthetics. Blur sigma clamped to [0.0, 100.0] — arbitrary upper bound but prevents GPU memory exhaustion.
 - **How**: (1) Texture offset to (-pad, -pad) in render_blurred_texture. (2) lock.lock() before resolve_background_path. (3) begin_verification disconnects old signal_id before registering new. (4) resume_async resets failed_attempts. (5) Unknown VerifyStatus with done=true triggers restart. (6) symlink_metadata() for atomic file+symlink check. (7) faillock_warning dead code removed, saturating_sub. (8) background_blur clamped. (9) Redundant Zeroizing<Vec<u8>> removed. (10) Default impl for FingerprintListener. (11) on_verify_status restricted to pub(crate). (12) Warn logging for non-UTF-8 GECOS and avatar paths.
 
 ## 2026-03-30 – Second audit: zeroize CString, FP account check, PAM timeout, blur downscale
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Second triple audit (quality, performance, security) found: CString password copy not zeroized (HIGH), fingerprint unlock bypassing pam_acct_mgmt (MEDIUM), no PAM timeout leaving user locked out on hanging modules (MEDIUM), GPU blur on full wallpaper resolution (MEDIUM), no-monitor edge case doing `return` instead of `exit(1)` (MEDIUM).
 - **Tradeoffs**: PAM timeout (30s) uses a generation counter to avoid stale result interference — adds complexity but prevents parallel PAM sessions. FP restart after failed account check re-claims the device, adding a D-Bus round-trip, but prevents permanent FP death on transient failures. Blur downscale to 1920px cap trades negligible quality for ~4x less GPU work on 4K wallpapers.
 - **How**: (1) `Zeroizing<CString>` wraps password in auth.rs, `zeroize/std` feature enabled. (2) `check_account()` calls pam_acct_mgmt after FP match; `resume_async()` restarts FP on transient failure. (3) `auth_generation` counter invalidates stale PAM results; 30s timeout re-enables UI. (4) `MAX_BLUR_DIMENSION` caps blur input at 1920px, sigma scaled proportionally. (5) `exit(1)` on no-monitor after `lock.lock()`.
 
 ## 2026-03-28 – Remove embedded wallpaper from binary
 
-- **Who**: Nyx, Dom
+- **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, lockscreen 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 background picture creation when no texture available.
 
 ## 2026-03-28 – Audit-driven security and lifecycle fixes (v0.6.0)
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Triple audit (quality, performance, security) revealed a critical D-Bus signal spoofing vector, fingerprint lifecycle bugs, and multi-monitor performance issues.
 - **Tradeoffs**: `cleanup_dbus()` extraction adds a method but clarifies the stop/match ownership; `running_flag: Rc<Cell<bool>>` adds a field but prevents race between async restart and stop; sender validation adds a check per signal but closes the only known auth bypass.
 - **How**: (1) Validate D-Bus VerifyStatus sender against fprintd's unique bus name. (2) Extract `cleanup_dbus()` from `stop()`, call it on verify-match. (3) `Rc<Cell<bool>>` running flag checked after await in `restart_verify_async`. (4) Consistent 3s D-Bus timeouts. (5) Panic hook before logging. (6) Blur and avatar caches shared across monitors. (7) Peek icon disabled. (8) Symlink rejection for background_path. (9) TOML parse errors logged.
 
 ## 2026-03-28 – GPU blur via GskBlurNode replaces CPU blur
 
-- **Who**: Nyx, 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 mitigated repeat starts but added ~100 lines of complexity.
 - **Tradeoffs**: GPU blur quality is slightly different (box-blur approximation vs true Gaussian), acceptable for wallpaper. Removes `image` and `dirs` dependencies entirely. 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.
 
 ## 2026-03-28 – Optional background blur via `image` crate (superseded)
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Consistent with moonset/moongreet — blurred wallpaper as lockscreen background is a common UX pattern
 - **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 `gdk::Texture`. Config option `background_blur: Option<f32>` in TOML.
 
 ## 2026-03-28 – Shared wallpaper texture pattern (aligned with moonset/moongreet)
 
-- **Who**: Nyx, Dom
+- **Who**: ClaudeCode, Dom
 - **Why**: Previously loaded wallpaper per-window via `Picture::for_filename()`. Multi-monitor setups decoded the JPEG redundantly. Blur feature requires texture pixel access anyway.
 - **Tradeoffs**: Slightly more code in main.rs (texture loaded before window creation), but avoids redundant decoding and enables the blur feature.
 - **How**: `load_background_texture()` in lockscreen.rs decodes once, `create_background_picture()` wraps shared `gdk::Texture` in `gtk::Picture`. Same pattern as moonset/moongreet.

README.md

@@ -9,7 +9,7 @@ Part of the Moonarch ecosystem.
 - **PAM authentication** — Uses system PAM stack (`/etc/pam.d/moonlock`) with 30s timeout and generation counter
 - **Fingerprint unlock** — fprintd D-Bus integration with sender validation, async init (window appears instantly), `pam_acct_mgmt` check after verify, auto-resume on transient errors
 - **Multi-monitor + hotplug** — Lockscreen on every monitor with shared blur and avatar caches; monitors added after suspend/resume get windows automatically via `connect_monitor` signal
-- **GPU blur** — Background blur via GskBlurNode (downscale to max 1920px, configurable 0–100)
+- **GPU blur** — Background blur via GskBlurNode (downscale to max 1920px, configurable 0–200)
 - **i18n** — German and English (auto-detected)
 - **Faillock warning** — Progressive UI warning after failed attempts, PAM decides lockout
 - **Panic safety** — Panic hook logs but never unlocks (installed before logging)
@@ -48,7 +48,7 @@ Create `/etc/moonlock/moonlock.toml` or `~/.config/moonlock/moonlock.toml`:
 
 ```toml
 background_path = "/usr/share/wallpapers/moon.jpg"
-background_blur = 40.0    # 0.0–100.0, optional
+background_blur = 40.0    # 0.0–200.0, optional
 fingerprint_enabled = true
 ```
 

src/auth.rs

@@ -191,7 +191,12 @@ pub fn authenticate(username: &str, password: &str) -> bool {
         return false;
     }
 
-    // Safety: handle is valid and non-null after successful pam_start
+    // Safety: handle is valid and non-null after successful pam_start.
+    // Note: pam_setcred is intentionally NOT called here. A lockscreen unlocks
+    // an existing session whose credentials were already established at login;
+    // refreshing them would duplicate work done by the session's login manager.
+    // If per-unlock credential refresh (Kerberos tickets, pam_gnome_keyring)
+    // is ever desired, hook it here with PAM_ESTABLISH_CRED.
     let auth_ret = unsafe { pam_authenticate(handle, 0) };
     let acct_ret = if auth_ret == PAM_SUCCESS {
         // Safety: handle is valid, check account restrictions
@@ -211,7 +216,12 @@ pub fn authenticate(username: &str, password: &str) -> bool {
 /// Used after fingerprint unlock to enforce account policies (lockout, expiry)
 /// that would otherwise be bypassed when not going through pam_authenticate.
 /// Returns true if the account is valid and allowed to log in.
-pub fn check_account(username: &str) -> bool {
+///
+/// **Precondition**: `username` must be the authenticated system user, derived
+/// via `users::get_current_user()` (which reads `getuid()`). Calling this with
+/// an attacker-controlled username is unsafe — `pam_acct_mgmt` returns SUCCESS
+/// for any valid unlocked account, giving a trivial unlock bypass.
+pub(crate) fn check_account(username: &str) -> bool {
     let service = match CString::new("moonlock") {
         Ok(c) => c,
         Err(_) => return false,

src/fingerprint.rs

@@ -177,12 +177,24 @@ impl FingerprintListener {
 
     /// Resume fingerprint verification after a transient interruption (e.g. failed
     /// PAM account check). Reuses previously stored callbacks. Re-claims the device
-    /// and restarts verification from scratch.
+    /// and restarts verification from scratch. Awaits any in-flight VerifyStop +
+    /// Release before re-claiming the device so fprintd does not reject the Claim
+    /// while the previous session is still being torn down.
     pub async fn resume_async(
         listener: &Rc<RefCell<FingerprintListener>>,
         username: &str,
     ) {
-        listener.borrow_mut().failed_attempts = 0;
+        // Drain in-flight cleanup so the device is actually released before Claim.
+        // Without this, a fast resume after on_verify_status's fire-and-forget
+        // cleanup races the Release call and fprintd returns "already claimed".
+        let proxy = listener.borrow_mut().take_cleanup_proxy();
+        if let Some(proxy) = proxy {
+            Self::perform_dbus_cleanup(proxy).await;
+        }
+        // Deliberately do NOT reset failed_attempts here. An attacker with sensor
+        // control could otherwise cycle verify-match → check_account fail → resume,
+        // and the 10-attempt cap would never trigger. The counter decays only via
+        // a fresh lock session (listener construction).
         Self::begin_verification(listener, username).await;
     }
 
@@ -352,26 +364,37 @@ impl FingerprintListener {
         }
     }
 
-    /// Disconnect the signal handler and send VerifyStop + Release to fprintd.
-    /// Signal disconnect is synchronous to prevent further callbacks.
-    /// D-Bus cleanup is fire-and-forget to avoid blocking the UI.
-    fn cleanup_dbus(&mut self) {
+    /// Disconnect the signal handler and clear running flags. Returns the proxy
+    /// the caller should use for the async D-Bus cleanup (VerifyStop + Release).
+    ///
+    /// Split into a sync part (signal disconnect, flags) and an async part
+    /// (`perform_dbus_cleanup`) so callers can either spawn the async work
+    /// fire-and-forget (via `cleanup_dbus`) or await it to serialize with a
+    /// subsequent Claim (via `resume_async`).
+    fn take_cleanup_proxy(&mut self) -> Option<gio::DBusProxy> {
         self.running = false;
         self.running_flag.set(false);
 
-        if let Some(ref proxy) = self.device_proxy {
-            if let Some(id) = self.signal_id.take() {
-                proxy.disconnect(id);
-            }
-            let proxy = proxy.clone();
-            glib::spawn_future_local(async move {
-                let _ = proxy
-                    .call_future("VerifyStop", None, gio::DBusCallFlags::NONE, DBUS_TIMEOUT_MS)
-                    .await;
-                let _ = proxy
-                    .call_future("Release", None, gio::DBusCallFlags::NONE, DBUS_TIMEOUT_MS)
-                    .await;
-            });
+        let proxy = self.device_proxy.clone()?;
+        if let Some(id) = self.signal_id.take() {
+            proxy.disconnect(id);
+        }
+        Some(proxy)
+    }
+
+    async fn perform_dbus_cleanup(proxy: gio::DBusProxy) {
+        let _ = proxy
+            .call_future("VerifyStop", None, gio::DBusCallFlags::NONE, DBUS_TIMEOUT_MS)
+            .await;
+        let _ = proxy
+            .call_future("Release", None, gio::DBusCallFlags::NONE, DBUS_TIMEOUT_MS)
+            .await;
+    }
+
+    /// Fire-and-forget cleanup for code paths that cannot await (e.g. drop, stop).
+    fn cleanup_dbus(&mut self) {
+        if let Some(proxy) = self.take_cleanup_proxy() {
+            glib::spawn_future_local(Self::perform_dbus_cleanup(proxy));
         }
     }
 

src/lockscreen.rs

@@ -244,6 +244,10 @@ pub fn create_lockscreen_window(
             if password.is_empty() {
                 return;
             }
+            // Clear the GTK entry's internal buffer as early as possible. GTK allocates
+            // the backing GString via libc malloc, which zeroize cannot reach — the
+            // best we can do is shorten the window during which it resides in memory.
+            entry.set_text("");
 
             entry.set_sensitive(false);
             let username = username.clone();
@@ -518,12 +522,35 @@ pub fn start_fingerprint(
 /// Load the wallpaper as a texture once, for sharing across all windows.
 /// Returns None if no wallpaper path is provided or the file cannot be loaded.
 /// Blur is applied at render time via GPU (GskBlurNode), not here.
+///
+/// Opens the file with O_NOFOLLOW to close the TOCTOU window between the
+/// symlink check in `resolve_background_path_with` and this read. If the path
+/// was swapped for a symlink after the check, `open` fails with ELOOP.
 pub fn load_background_texture(bg_path: &Path) -> Option<gdk::Texture> {
-    let file = gio::File::for_path(bg_path);
-    match gdk::Texture::from_file(&file) {
+    use std::io::Read;
+    use std::os::unix::fs::OpenOptionsExt;
+
+    let mut file = match std::fs::OpenOptions::new()
+        .read(true)
+        .custom_flags(libc::O_NOFOLLOW)
+        .open(bg_path)
+    {
+        Ok(f) => f,
+        Err(e) => {
+            log::warn!("Failed to open wallpaper {}: {e}", bg_path.display());
+            return None;
+        }
+    };
+    let mut bytes = Vec::new();
+    if let Err(e) = file.read_to_end(&mut bytes) {
+        log::warn!("Failed to read wallpaper {}: {e}", bg_path.display());
+        return None;
+    }
+    let glib_bytes = glib::Bytes::from_owned(bytes);
+    match gdk::Texture::from_bytes(&glib_bytes) {
         Ok(texture) => Some(texture),
         Err(e) => {
-            log::warn!("Failed to load wallpaper {}: {e}", bg_path.display());
+            log::warn!("Failed to decode wallpaper {}: {e}", bg_path.display());
             None
         }
     }
@@ -565,11 +592,11 @@ fn create_background_picture(
     background
 }
 
-/// Maximum texture dimension for blur input. Textures larger than this are
 // SYNC: MAX_BLUR_DIMENSION, render_blurred_texture, and create_background_picture
 // are duplicated in moongreet/src/greeter.rs and moonset/src/panel.rs.
 // Changes here must be mirrored to the other two projects.
 
+/// Maximum texture dimension for blur input. Textures larger than this are
 /// downscaled before blurring — the blur destroys detail anyway, so there is
 /// no visible quality loss, but GPU work is reduced significantly.
 const MAX_BLUR_DIMENSION: f32 = 1920.0;
@@ -623,30 +650,41 @@ fn render_blurred_texture(
 }
 
 /// Load an image file and set it as the avatar. Stores the texture in the cache.
+/// Decoding runs via GIO async I/O + async pixbuf stream loader so the GTK main
+/// loop stays responsive — avatars may be loaded inside the `connect_monitor`
+/// signal handler at hotplug time, which must not block. The fallback icon is
+/// shown immediately; the decoded texture replaces it when ready.
 fn set_avatar_from_file(
     image: &gtk::Image,
     path: &Path,
     cache: &Rc<RefCell<Option<gdk::Texture>>>,
 ) {
-    let path_str = match path.to_str() {
-        Some(s) => s,
-        None => {
-            log::warn!("Avatar path is not valid UTF-8: {:?}", path);
-            image.set_icon_name(Some("avatar-default-symbolic"));
-            return;
+    image.set_icon_name(Some("avatar-default-symbolic"));
+
+    let display_path = path.to_path_buf();
+    let file = gio::File::for_path(path);
+    let image_clone = image.clone();
+    let cache_clone = cache.clone();
+
+    glib::spawn_future_local(async move {
+        let stream = match file.read_future(glib::Priority::default()).await {
+            Ok(s) => s,
+            Err(e) => {
+                log::warn!("Failed to open avatar {}: {e}", display_path.display());
+                return;
+            }
+        };
+        match Pixbuf::from_stream_at_scale_future(&stream, AVATAR_SIZE, AVATAR_SIZE, true).await {
+            Ok(pixbuf) => {
+                let texture = gdk::Texture::for_pixbuf(&pixbuf);
+                image_clone.set_paintable(Some(&texture));
+                *cache_clone.borrow_mut() = Some(texture);
+            }
+            Err(e) => {
+                log::warn!("Failed to decode avatar from {}: {e}", display_path.display());
+            }
         }
-    };
-    match Pixbuf::from_file_at_scale(path_str, AVATAR_SIZE, AVATAR_SIZE, true) {
-        Ok(pixbuf) => {
-            let texture = gdk::Texture::for_pixbuf(&pixbuf);
-            image.set_paintable(Some(&texture));
-            *cache.borrow_mut() = Some(texture);
-        }
-        Err(e) => {
-            log::warn!("Failed to load avatar from {:?}: {e}", path);
-            image.set_icon_name(Some("avatar-default-symbolic"));
-        }
-    }
+    });
 }
 
 /// Load the default avatar SVG from GResources, tinted with the foreground color.

src/main.rs

@@ -168,32 +168,38 @@ fn init_fingerprint_async(
         let mut listener = FingerprintListener::new();
         listener.init_async().await;
 
-        let handles = all_handles.borrow();
-        if handles.is_empty() {
-            return;
-        }
+        // Extract username without holding a borrow across the await below —
+        // otherwise a concurrent connect_monitor signal (hotplug / suspend-resume)
+        // that tries to borrow_mut() panics at runtime.
+        let username = {
+            let handles = all_handles.borrow();
+            if handles.is_empty() {
+                return;
+            }
+            let u = handles[0].username.clone();
+            if u.is_empty() {
+                return;
+            }
+            u
+        };
 
-        // Use the first monitor's username to check enrollment
-        let username = &handles[0].username;
-        if username.is_empty() {
-            return;
-        }
-
-        if !listener.is_available_async(username).await {
+        if !listener.is_available_async(&username).await {
             log::debug!("fprintd not available or no enrolled fingers");
             return;
         }
 
         let fp_rc = Rc::new(RefCell::new(listener));
 
-        // Show fingerprint label on all existing monitors
-        for h in handles.iter() {
-            lockscreen::show_fingerprint_label(h, &fp_rc);
+        // Re-borrow after the await — no further awaits in this scope, so it is
+        // safe to hold the borrow briefly while wiring up the labels.
+        {
+            let handles = all_handles.borrow();
+            for h in handles.iter() {
+                lockscreen::show_fingerprint_label(h, &fp_rc);
+            }
+            lockscreen::start_fingerprint(&handles[0], &fp_rc);
         }
 
-        // Start verification listener on the first monitor only
-        lockscreen::start_fingerprint(&handles[0], &fp_rc);
-
         // Publish the listener so hotplugged monitors get FP labels too
         *shared_fp.borrow_mut() = Some(fp_rc);
     });
@@ -244,11 +250,17 @@ fn setup_logging() {
             eprintln!("Failed to create journal logger: {e}");
         }
     }
+    // Debug level is only selectable in debug builds. Release binaries ignore
+    // MOONLOCK_DEBUG so a session script cannot escalate log verbosity to leak
+    // fprintd / D-Bus internals into the journal.
+    #[cfg(debug_assertions)]
     let level = if std::env::var("MOONLOCK_DEBUG").is_ok() {
         log::LevelFilter::Debug
     } else {
         log::LevelFilter::Info
     };
+    #[cfg(not(debug_assertions))]
+    let level = log::LevelFilter::Info;
     log::set_max_level(level);
 }