feat(opsec): implement inactivity auto-lock, session lock detection, and anti-leak shield

src/main.rs

@@ -60,6 +60,18 @@ enum Commands {
         /// Deaktiviert das Windows System-Tray Icon während des Mounts
         #[arg(long, default_value_t = false)]
         no_tray: bool,
+
+        /// Automatisches Aushängen und Sperren nach N Sekunden Inaktivität (z. B. 300 für 5 Minuten)
+        #[arg(long, value_name = "SECS")]
+        idle_timeout: Option<u64>,
+
+        /// Verhindert das automatische Sperren beim Sperren des Windows-Bildschirms (Win + L)
+        #[arg(long, default_value_t = false)]
+        no_screen_lock: bool,
+
+        /// Deaktiviert das Blockieren und Verbergen von Windows Explorer Metadaten (Thumbs.db, desktop.ini)
+        #[arg(long, default_value_t = false)]
+        no_anti_leak: bool,
     },
 
     /// Trennt ein eingebundenes Netzlaufwerk manuell
@@ -481,6 +493,9 @@ async fn run() -> Result<()> {
             recovery_key,
             no_open,
             no_tray,
+            idle_timeout,
+            no_screen_lock,
+            no_anti_leak,
         } => {
             let drive_char = match drive {
                 Some(ref d) => parse_drive_letter(d)?,
@@ -508,7 +523,20 @@ async fn run() -> Result<()> {
 
             let open_explorer = !no_open;
             let enable_tray = !no_tray;
-            mount_container(&path, drive_char, port, auth, open_explorer, enable_tray).await?;
+            let lock_on_screen_lock = !no_screen_lock;
+            let anti_leak = !no_anti_leak;
+            mount_container(
+                &path,
+                drive_char,
+                port,
+                auth,
+                open_explorer,
+                enable_tray,
+                idle_timeout,
+                lock_on_screen_lock,
+                anti_leak,
+            )
+            .await?;
         }
         Commands::Unmount { drive } => {
             let drive_char = parse_drive_letter(&drive)?;

src/mount.rs

@@ -2,6 +2,8 @@ use std::convert::Infallible;
 use std::net::SocketAddr;
 use std::path::Path;
 use std::process::Command;
+use std::sync::atomic::Ordering;
+use std::time::{SystemTime, UNIX_EPOCH};
 
 use anyhow::{bail, Context, Result};
 use dav_server::{fakels::FakeLs, DavHandler};
@@ -83,6 +85,9 @@ pub async fn mount_container(
     auth: ContainerAuth,
     open_explorer: bool,
     enable_tray: bool,
+    idle_timeout: Option<u64>,
+    lock_on_screen_lock: bool,
+    anti_leak: bool,
 ) -> Result<()> {
     let drive_str = format_drive(drive_letter);
 
@@ -127,8 +132,9 @@ pub async fn mount_container(
         }
     };
 
-    // WebDAV Filesystem und Handler konfigurieren
-    let fs = SanctumFs::new(db.clone(), dek, version);
+    // WebDAV Filesystem und Handler konfigurieren (mit Anti-Leak Shield)
+    let fs = SanctumFs::with_options(db.clone(), dek, version, anti_leak);
+    let last_activity = fs.last_activity();
     let dav_server = DavHandler::builder()
         .filesystem(Box::new(fs))
         .locksystem(FakeLs::new())
@@ -248,6 +254,44 @@ pub async fn mount_container(
         None
     };
 
+    // Inaktivitäts-Timer (Auto-Lock)
+    let (idle_shutdown_tx, mut idle_shutdown_rx) = tokio::sync::mpsc::channel::<()>(1);
+    if let Some(timeout_secs) = idle_timeout {
+        if timeout_secs > 0 {
+            let last_act = last_activity.clone();
+            let idle_tx = idle_shutdown_tx.clone();
+            tokio::spawn(async move {
+                let mut interval = tokio::time::interval(std::time::Duration::from_secs(1));
+                loop {
+                    interval.tick().await;
+                    let now = SystemTime::now()
+                        .duration_since(UNIX_EPOCH)
+                        .map(|d| d.as_secs())
+                        .unwrap_or(0);
+                    let last = last_act.load(Ordering::Relaxed);
+                    if now.saturating_sub(last) >= timeout_secs {
+                        let _ = idle_tx.send(()).await;
+                        break;
+                    }
+                }
+            });
+        }
+    }
+
+    // Windows-Sitzungssperre (Win + L Auto-Lock)
+    let (session_lock_tx, mut session_lock_rx) = tokio::sync::mpsc::channel::<()>(1);
+    let _session_monitor = if lock_on_screen_lock {
+        match crate::windows::start_session_lock_monitor(session_lock_tx) {
+            Ok(guard) => Some(guard),
+            Err(e) => {
+                warn!("Konnte Windows Session-Lock Monitor nicht aktivieren: {e}");
+                None
+            }
+        }
+    } else {
+        None
+    };
+
     println!();
     println!("┌─────────────────────────────────────────────────────────────┐");
     println!("│  ✔ Sanctum Container erfolgreich gemountet                  │");
@@ -256,6 +300,15 @@ pub async fn mount_container(
     println!("  • Container:    {}", container_path.display());
     println!("  • Netzlaufwerk: {} (im Windows Explorer bereit)", ui::cyan(&drive_str));
     println!("  • WebDAV-URL:   http://127.0.0.1:{}/", bound_port);
+    if let Some(secs) = idle_timeout {
+        println!("  • Auto-Lock:    Inaktivität nach {}s", secs);
+    }
+    if lock_on_screen_lock {
+        println!("  • Sitzung:      Automatisches Sperren bei Win + L aktiv");
+    }
+    if anti_leak {
+        println!("  • Anti-Leak:    Explorer-Metadatenfilter aktiv (Thumbs.db, desktop.ini blockiert)");
+    }
     if enable_tray {
         println!("  • System-Tray:  Icon aktiv (Rechtsklick für Explorer/Trennen)");
     }
@@ -263,7 +316,7 @@ pub async fn mount_container(
     println!("  [{}] Drücke [Ctrl+C] oder nutze das Tray-Icon zum Beenden.", ui::yellow("Tipp"));
     println!();
 
-    // Warten auf Strg+C ODER Signal aus dem System-Tray
+    // Warten auf Beendigungssignal (Ctrl+C, Tray-Klick, Inaktivität, Win+L)
     tokio::select! {
         res = tokio::signal::ctrl_c() => {
             let _ = res;
@@ -274,6 +327,14 @@ pub async fn mount_container(
             println!();
             println!("  {} Beendigungssignal aus System-Tray empfangen.", ui::yellow("[!]"));
         }
+        _ = session_lock_rx.recv() => {
+            println!();
+            println!("  {} Windows-Sitzung gesperrt (Win + L) — Auto-Lock ausgelöst!", ui::yellow("[!]"));
+        }
+        _ = idle_shutdown_rx.recv() => {
+            println!();
+            println!("  {} Inaktivitäts-Timeout erreicht — Auto-Lock ausgelöst!", ui::yellow("[!]"));
+        }
     }
     print!("  {} Trenne Windows-Netzlaufwerk {} ... ", ui::dim("[-]"), drive_str);
     let _ = std::io::Write::flush(&mut std::io::stdout());

src/vfs.rs

@@ -1,5 +1,6 @@
 use std::fmt::Debug;
 use std::io::SeekFrom;
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
@@ -18,6 +19,31 @@ use zeroize::Zeroizing;
 use crate::crypto::{decrypt_chunk, encrypt_chunk, CHUNK_SIZE};
 use crate::storage::{Database, NodeRecord};
 
+/// Prüft, ob ein Dateiname zu den typischen Windows Explorer Metadaten-, Cache-
+/// oder Thumbnail-Dateien gehört (z. B. Thumbs.db, desktop.ini), die standardmäßig
+/// im Container blockiert und verborgen werden (Anti-Leak Shield).
+pub fn is_leak_file(filename: &str) -> bool {
+    let lower = filename.trim().to_ascii_lowercase();
+    match lower.as_str() {
+        "thumbs.db"
+        | "ehthumbs.db"
+        | "ehthumbs_vista.db"
+        | "desktop.ini"
+        | "folder.jpg"
+        | "albumartsmall.jpg"
+        | "autorun.inf"
+        | ".ds_store" => true,
+        _ => {
+            if lower.starts_with("albumart") && (lower.ends_with(".jpg") || lower.ends_with(".ini"))
+            {
+                true
+            } else {
+                false
+            }
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Metadaten
 // ---------------------------------------------------------------------------
@@ -87,6 +113,7 @@ pub struct SanctumFile {
     // (chunk_index, decrypted_payload, is_dirty)
     cached_chunk: Option<(u32, Vec<u8>, bool)>,
     format_version: u32,
+    last_activity: Arc<AtomicU64>,
 }
 
 impl Debug for SanctumFile {
@@ -106,6 +133,7 @@ impl SanctumFile {
         db: Database,
         dek: Arc<Zeroizing<[u8; 32]>>,
         format_version: u32,
+        last_activity: Arc<AtomicU64>,
     ) -> Self {
         let meta = SanctumMetaData {
             is_dir: node.is_dir,
@@ -123,9 +151,18 @@ impl SanctumFile {
             meta,
             cached_chunk: None,
             format_version,
+            last_activity,
         }
     }
 
+    fn touch(&self) {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
+        self.last_activity.store(now, Ordering::Relaxed);
+    }
+
 
     /// Schreibt den aktuell im RAM gehaltenen Chunk verschlüsselt in die SQLite-Datenbank zurück.
     fn flush_cached_chunk(&mut self) -> Result<(), FsError> {
@@ -211,6 +248,7 @@ impl DavFile for SanctumFile {
     }
 
     fn read_bytes(&mut self, mut count: usize) -> FsFuture<'_, Bytes> {
+        self.touch();
         Box::pin(async move {
             if self.cursor >= self.file_size || count == 0 {
                 return Ok(Bytes::new());
@@ -253,6 +291,7 @@ impl DavFile for SanctumFile {
     }
 
     fn write_bytes(&mut self, buf: Bytes) -> FsFuture<'_, ()> {
+        self.touch();
         Box::pin(async move {
             let mut src = &buf[..];
 
@@ -301,6 +340,7 @@ impl DavFile for SanctumFile {
     }
 
     fn seek(&mut self, pos: SeekFrom) -> FsFuture<'_, u64> {
+        self.touch();
         Box::pin(async move {
             let new_cursor = match pos {
                 SeekFrom::Start(offset) => offset as i64,
@@ -318,6 +358,7 @@ impl DavFile for SanctumFile {
     }
 
     fn flush(&mut self) -> FsFuture<'_, ()> {
+        self.touch();
         Box::pin(async move {
             self.flush_cached_chunk()?;
             let now = SystemTime::now()
@@ -346,17 +387,50 @@ pub struct SanctumFs {
     db: Database,
     dek: Arc<Zeroizing<[u8; 32]>>,
     format_version: u32,
+    anti_leak: bool,
+    last_activity: Arc<AtomicU64>,
 }
 
 impl SanctumFs {
     pub fn new(db: Database, dek: Zeroizing<[u8; 32]>, format_version: u32) -> Self {
+        Self::with_options(db, dek, format_version, true)
+    }
+
+    pub fn with_options(
+        db: Database,
+        dek: Zeroizing<[u8; 32]>,
+        format_version: u32,
+        anti_leak: bool,
+    ) -> Self {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
         Self {
             db,
             dek: Arc::new(dek),
             format_version,
+            anti_leak,
+            last_activity: Arc::new(AtomicU64::new(now)),
         }
     }
 
+    pub fn last_activity(&self) -> Arc<AtomicU64> {
+        self.last_activity.clone()
+    }
+
+    pub fn is_anti_leak_enabled(&self) -> bool {
+        self.anti_leak
+    }
+
+    pub fn touch(&self) {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
+        self.last_activity.store(now, Ordering::Relaxed);
+    }
+
     fn path_to_str(path: &DavPath) -> String {
         String::from_utf8_lossy(path.as_bytes()).to_string()
     }
@@ -378,6 +452,25 @@ impl DavFileSystem for SanctumFs {
     ) -> FsFuture<'a, Box<dyn DavFile>> {
         Box::pin(async move {
             let path_str = Self::path_to_str(path);
+            let (parent_path, file_name) = self.split_parent_and_name(&path_str);
+
+            // Anti-Leak Shield: Blockiere Schreib- oder Neuerstellungsversuche für Explorer-Metadaten
+            if self.anti_leak && is_leak_file(file_name) {
+                if options.create
+                    || options.create_new
+                    || options.write
+                    || options.append
+                    || options.truncate
+                {
+                    debug!(
+                        "Anti-Leak: Blockiere Erstellung/Schreibzugriff für '{}'",
+                        file_name
+                    );
+                    return Err(FsError::Forbidden);
+                }
+            }
+
+            self.touch();
             debug!("VFS open aufgerufen: path='{}', options={:?}", path_str, options);
 
             let existing_node = self
@@ -417,7 +510,6 @@ impl DavFileSystem for SanctumFs {
                 }
                 None => {
                     if options.create || options.create_new {
-                        let (parent_path, file_name) = self.split_parent_and_name(&path_str);
                         let parent = self
                             .db
                             .resolve_path(parent_path)
@@ -440,7 +532,13 @@ impl DavFileSystem for SanctumFs {
                 }
             };
 
-            let file = SanctumFile::new(node, self.db.clone(), self.dek.clone(), self.format_version);
+            let file = SanctumFile::new(
+                node,
+                self.db.clone(),
+                self.dek.clone(),
+                self.format_version,
+                self.last_activity.clone(),
+            );
             Ok(Box::new(file) as Box<dyn DavFile>)
         })
     }
@@ -451,6 +549,7 @@ impl DavFileSystem for SanctumFs {
         _meta: ReadDirMeta,
     ) -> FsFuture<'a, FsStream<Box<dyn DavDirEntry>>> {
         Box::pin(async move {
+            self.touch();
             let path_str = Self::path_to_str(path);
             let node = self
                 .db
@@ -469,6 +568,7 @@ impl DavFileSystem for SanctumFs {
 
             let entries: Vec<Result<Box<dyn DavDirEntry>, FsError>> = children
                 .into_iter()
+                .filter(|child| !self.anti_leak || !is_leak_file(&child.name))
                 .map(|child| {
                     Ok(Box::new(SanctumDirEntry {
                         name: child.name,
@@ -489,6 +589,9 @@ impl DavFileSystem for SanctumFs {
     fn metadata<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, Box<dyn DavMetaData>> {
         Box::pin(async move {
             let path_str = Self::path_to_str(path);
+            if path_str != "/" && !path_str.is_empty() {
+                self.touch();
+            }
             let node = self
                 .db
                 .resolve_path(&path_str)
@@ -512,7 +615,14 @@ impl DavFileSystem for SanctumFs {
 
     fn create_dir<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
         Box::pin(async move {
+            self.touch();
             let path_str = Self::path_to_str(path);
+            let (parent_path, dir_name) = self.split_parent_and_name(&path_str);
+
+            if self.anti_leak && is_leak_file(dir_name) {
+                return Err(FsError::Forbidden);
+            }
+
             if self
                 .db
                 .resolve_path(&path_str)
@@ -522,7 +632,6 @@ impl DavFileSystem for SanctumFs {
                 return Err(FsError::Exists);
             }
 
-            let (parent_path, dir_name) = self.split_parent_and_name(&path_str);
             let parent = self
                 .db
                 .resolve_path(parent_path)
@@ -543,6 +652,7 @@ impl DavFileSystem for SanctumFs {
 
     fn remove_dir<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
         Box::pin(async move {
+            self.touch();
             let path_str = Self::path_to_str(path);
             let node = self
                 .db
@@ -568,6 +678,7 @@ impl DavFileSystem for SanctumFs {
 
     fn remove_file<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
         Box::pin(async move {
+            self.touch();
             let path_str = Self::path_to_str(path);
             let node = self
                 .db
@@ -593,6 +704,7 @@ impl DavFileSystem for SanctumFs {
         to: &'a DavPath,
     ) -> FsFuture<'a, ()> {
         Box::pin(async move {
+            self.touch();
             let from_str = Self::path_to_str(from);
             let to_str = Self::path_to_str(to);
 
@@ -603,6 +715,11 @@ impl DavFileSystem for SanctumFs {
                 .ok_or(FsError::NotFound)?;
 
             let (to_parent_path, to_name) = self.split_parent_and_name(&to_str);
+
+            if self.anti_leak && is_leak_file(to_name) {
+                return Err(FsError::Forbidden);
+            }
+
             let to_parent = self
                 .db
                 .resolve_path(to_parent_path)
@@ -641,6 +758,7 @@ impl DavFileSystem for SanctumFs {
         to: &'a DavPath,
     ) -> FsFuture<'a, ()> {
         Box::pin(async move {
+            self.touch();
             let from_str = Self::path_to_str(from);
             let to_str = Self::path_to_str(to);
 
@@ -655,6 +773,11 @@ impl DavFileSystem for SanctumFs {
             }
 
             let (to_parent_path, to_name) = self.split_parent_and_name(&to_str);
+
+            if self.anti_leak && is_leak_file(to_name) {
+                return Err(FsError::Forbidden);
+            }
+
             let to_parent = self
                 .db
                 .resolve_path(to_parent_path)
@@ -720,3 +843,167 @@ impl DavFileSystem for SanctumFs {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::crypto::{derive_kek, generate_dek, generate_salt, wrap_dek, KdfParams, FORMAT_VERSION};
+    use dav_server::fs::OpenOptions;
+    use futures_util::StreamExt;
+
+    #[test]
+    fn test_is_leak_file() {
+        assert!(is_leak_file("Thumbs.db"));
+        assert!(is_leak_file("thumbs.db"));
+        assert!(is_leak_file("THUMBS.DB"));
+        assert!(is_leak_file("ehthumbs.db"));
+        assert!(is_leak_file("ehthumbs_vista.db"));
+        assert!(is_leak_file("desktop.ini"));
+        assert!(is_leak_file("Desktop.ini"));
+        assert!(is_leak_file("Folder.jpg"));
+        assert!(is_leak_file("albumartsmall.jpg"));
+        assert!(is_leak_file("AlbumArt_{12345}_Large.jpg"));
+        assert!(is_leak_file("AlbumArt_{12345}_Small.jpg"));
+        assert!(is_leak_file("autorun.inf"));
+        assert!(is_leak_file(".ds_store"));
+
+        // Harmlos:
+        assert!(!is_leak_file("secret.txt"));
+        assert!(!is_leak_file("passwords.kdbx"));
+        assert!(!is_leak_file("my_folder.jpg.txt"));
+        assert!(!is_leak_file("desktop_notes.ini.bak"));
+    }
+
+    fn create_test_fs(anti_leak: bool) -> (SanctumFs, tempfile_placeholder::TempDir) {
+        let temp_dir = tempfile_placeholder::TempDir::new();
+        let db_path = temp_dir.path().join("test_vfs.sanctum");
+        let db = Database::open(&db_path).unwrap();
+
+        let salt = generate_salt();
+        let kdf_params = KdfParams {
+            memory_cost: 1024,
+            time_cost: 1,
+            parallelism: 1,
+        };
+        let kek = derive_kek("testpwd", &salt, &kdf_params).unwrap();
+        let dek = generate_dek();
+        let (wrapped_dek, header_nonce, header_tag) = wrap_dek(&kek, &dek).unwrap();
+        db.init_schema(&salt, &kdf_params, &wrapped_dek, &header_nonce, &header_tag)
+            .unwrap();
+
+        let fs = SanctumFs::with_options(db, dek, FORMAT_VERSION, anti_leak);
+        (fs, temp_dir)
+    }
+
+    mod tempfile_placeholder {
+        use std::path::{Path, PathBuf};
+        pub struct TempDir(PathBuf);
+        impl TempDir {
+            pub fn new() -> Self {
+                let p = std::env::temp_dir().join(format!("sanctum_test_{}", rand::random::<u64>()));
+                std::fs::create_dir_all(&p).unwrap();
+                Self(p)
+            }
+            pub fn path(&self) -> &Path {
+                &self.0
+            }
+        }
+        impl Drop for TempDir {
+            fn drop(&mut self) {
+                let _ = std::fs::remove_dir_all(&self.0);
+            }
+        }
+    }
+
+    #[tokio::test]
+    async fn test_anti_leak_blocks_creation() {
+        let (fs, _dir) = create_test_fs(true);
+
+        let path = DavPath::new("/desktop.ini").unwrap();
+        let mut opts = OpenOptions::default();
+        opts.write = true;
+        opts.create_new = true;
+
+        // desktop.ini muss blockiert werden mit Forbidden
+        let res = fs.open(&path, opts).await;
+        assert!(matches!(res, Err(FsError::Forbidden)));
+
+        // create_dir mit Thumbs.db muss auch blockiert werden
+        let dir_path = DavPath::new("/Thumbs.db").unwrap();
+        let res_dir = fs.create_dir(&dir_path).await;
+        assert!(matches!(res_dir, Err(FsError::Forbidden)));
+
+        // Normale Datei muss erlaubt sein
+        let valid_path = DavPath::new("/notes.txt").unwrap();
+        let mut valid_opts = OpenOptions::default();
+        valid_opts.write = true;
+        valid_opts.create_new = true;
+        let res_valid = fs.open(&valid_path, valid_opts).await;
+        assert!(res_valid.is_ok());
+    }
+
+    #[tokio::test]
+    async fn test_anti_leak_filters_read_dir() {
+        let (fs_shielded, _dir) = create_test_fs(true);
+
+        // Erstelle eine normale Datei
+        let normal_path = DavPath::new("/legit.txt").unwrap();
+        let mut opts = OpenOptions::default();
+        opts.write = true;
+        opts.create_new = true;
+        let res = fs_shielded.open(&normal_path, opts).await;
+        assert!(res.is_ok());
+
+        // Erzwinge direkt in die DB eine Thumbs.db Datei
+        fs_shielded.db.create_node(1, "Thumbs.db", false).unwrap();
+
+        // read_dir mit anti_leak = true darf Thumbs.db NICHT anzeigen
+        let root_path = DavPath::new("/").unwrap();
+        let mut stream = fs_shielded.read_dir(&root_path, ReadDirMeta::None).await.unwrap();
+        let mut names = Vec::new();
+        while let Some(entry) = stream.next().await {
+            let entry = entry.unwrap();
+            names.push(String::from_utf8_lossy(&entry.name()).to_string());
+        }
+
+        assert!(names.contains(&"legit.txt".to_string()));
+        assert!(!names.contains(&"Thumbs.db".to_string()));
+
+        // Mit unshielded FS (anti_leak = false) muss Thumbs.db sichtbar sein
+        let fs_unshielded = SanctumFs::with_options(
+            fs_shielded.db.clone(),
+            zeroize::Zeroizing::new([0u8; 32]),
+            FORMAT_VERSION,
+            false,
+        );
+        let mut stream_unshielded = fs_unshielded.read_dir(&root_path, ReadDirMeta::None).await.unwrap();
+        let mut names_unshielded = Vec::new();
+        while let Some(entry) = stream_unshielded.next().await {
+            let entry = entry.unwrap();
+            names_unshielded.push(String::from_utf8_lossy(&entry.name()).to_string());
+        }
+        assert!(names_unshielded.contains(&"Thumbs.db".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_vfs_activity_tracking() {
+        let (fs, _dir) = create_test_fs(true);
+        let act_arc = fs.last_activity();
+        let initial_time = act_arc.load(Ordering::Relaxed);
+        assert!(initial_time > 0);
+
+        // Manuell zurückdatieren
+        act_arc.store(1000, Ordering::Relaxed);
+        assert_eq!(act_arc.load(Ordering::Relaxed), 1000);
+
+        // Nach einem VFS-Zugriff muss die Zeit aktualisiert sein
+        let path = DavPath::new("/test_activity.txt").unwrap();
+        let mut opts = OpenOptions::default();
+        opts.write = true;
+        opts.create_new = true;
+        let _ = fs.open(&path, opts).await;
+
+        let new_time = act_arc.load(Ordering::Relaxed);
+        assert!(new_time > 1000);
+    }
+}

src/windows.rs

@@ -188,6 +188,229 @@ pub fn get_default_system_icon() -> Option<tray_item::IconSource> {
     }
 }
 
+/// Guard zur Verwaltung des Hintergrundthreads für die Windows-Sitzungssperre.
+/// Beim Droppen wird das Win32-Nachrichtenfenster geschlossen und der Thread sauber beendet.
+pub struct SessionLockGuard {
+    #[cfg(windows)]
+    hwnd: isize,
+    #[cfg(windows)]
+    join_handle: Option<std::thread::JoinHandle<()>>,
+}
+
+#[cfg(windows)]
+impl Drop for SessionLockGuard {
+    fn drop(&mut self) {
+        if self.hwnd != 0 {
+            unsafe {
+                PostMessageW(self.hwnd, 0x0010 /* WM_CLOSE */, 0, 0);
+            }
+        }
+        if let Ok(mut guard) = SESSION_LOCK_TX.lock() {
+            *guard = None;
+        }
+        if let Some(handle) = self.join_handle.take() {
+            let _ = handle.join();
+        }
+    }
+}
+
+#[cfg(not(windows))]
+pub struct SessionLockGuard;
+
+#[cfg(windows)]
+static SESSION_LOCK_TX: std::sync::Mutex<Option<tokio::sync::mpsc::Sender<()>>> =
+    std::sync::Mutex::new(None);
+
+#[cfg(windows)]
+#[allow(non_snake_case)]
+#[repr(C)]
+struct WNDCLASSEXW {
+    cbSize: u32,
+    style: u32,
+    lpfnWndProc: Option<unsafe extern "system" fn(isize, u32, usize, isize) -> isize>,
+    cbClsExtra: i32,
+    cbWndExtra: i32,
+    hInstance: isize,
+    hIcon: isize,
+    hCursor: isize,
+    hbrBackground: isize,
+    lpszMenuName: *const u16,
+    lpszClassName: *const u16,
+    hIconSm: isize,
+}
+
+#[cfg(windows)]
+#[allow(non_snake_case)]
+#[repr(C)]
+struct MSG {
+    hwnd: isize,
+    message: u32,
+    wParam: usize,
+    lParam: isize,
+    time: u32,
+    pt_x: i32,
+    pt_y: i32,
+}
+
+#[cfg(windows)]
+extern "system" {
+    fn GetModuleHandleW(lpModuleName: *const u16) -> isize;
+    fn RegisterClassExW(lpwcx: *const WNDCLASSEXW) -> u16;
+    fn UnregisterClassW(lpClassName: *const u16, hInstance: isize) -> i32;
+    fn CreateWindowExW(
+        dwExStyle: u32,
+        lpClassName: *const u16,
+        lpWindowName: *const u16,
+        dwStyle: u32,
+        x: i32,
+        y: i32,
+        nWidth: i32,
+        nHeight: i32,
+        hWndParent: isize,
+        hMenu: isize,
+        hInstance: isize,
+        lpParam: *mut std::ffi::c_void,
+    ) -> isize;
+    fn DestroyWindow(hwnd: isize) -> i32;
+    fn DefWindowProcW(hwnd: isize, msg: u32, wparam: usize, lparam: isize) -> isize;
+    fn GetMessageW(lpMsg: *mut MSG, hWnd: isize, wMsgFilterMin: u32, wMsgFilterMax: u32) -> i32;
+    fn TranslateMessage(lpMsg: *const MSG) -> i32;
+    fn DispatchMessageW(lpMsg: *const MSG) -> isize;
+    fn PostMessageW(hwnd: isize, msg: u32, wparam: usize, lparam: isize) -> i32;
+    fn PostQuitMessage(nExitCode: i32);
+}
+
+#[cfg(windows)]
+#[link(name = "wtsapi32")]
+extern "system" {
+    fn WTSRegisterSessionNotification(hwnd: isize, flags: u32) -> i32;
+    fn WTSUnRegisterSessionNotification(hwnd: isize) -> i32;
+}
+
+#[cfg(windows)]
+unsafe extern "system" fn session_wnd_proc(
+    hwnd: isize,
+    msg: u32,
+    wparam: usize,
+    lparam: isize,
+) -> isize {
+    const WM_CLOSE: u32 = 0x0010;
+    const WM_WTSSESSION_CHANGE: u32 = 0x02B1;
+    const WTS_SESSION_LOCK: usize = 0x7;
+    const WTS_SESSION_LOGOFF: usize = 0x6;
+
+    match msg {
+        WM_WTSSESSION_CHANGE => {
+            if wparam == WTS_SESSION_LOCK || wparam == WTS_SESSION_LOGOFF {
+                if let Ok(guard) = SESSION_LOCK_TX.lock() {
+                    if let Some(ref tx) = *guard {
+                        let _ = tx.blocking_send(());
+                    }
+                }
+            }
+            0
+        }
+        WM_CLOSE => {
+            PostQuitMessage(0);
+            0
+        }
+        _ => DefWindowProcW(hwnd, msg, wparam, lparam),
+    }
+}
+
+/// Startet einen Hintergrundthread mit einem verdeckten Win32-Nachrichtenfenster (HWND_MESSAGE),
+/// das via `WTSRegisterSessionNotification` auf Sperr-Events (Win + L) lauscht und beim Eintreffen
+/// ein Signal an den übergebenen Tokio-Kanal sendet.
+#[cfg(windows)]
+pub fn start_session_lock_monitor(
+    shutdown_tx: tokio::sync::mpsc::Sender<()>,
+) -> Result<SessionLockGuard> {
+    if let Ok(mut guard) = SESSION_LOCK_TX.lock() {
+        *guard = Some(shutdown_tx);
+    }
+
+    let (hwnd_tx, hwnd_rx) = std::sync::mpsc::channel::<isize>();
+
+    let join_handle = std::thread::Builder::new()
+        .name("sanctum-session-monitor".to_string())
+        .spawn(move || unsafe {
+            let h_instance = GetModuleHandleW(std::ptr::null());
+            let class_name: Vec<u16> = "SanctumSessionMonitorClass\0".encode_utf16().collect();
+
+            let wcx = WNDCLASSEXW {
+                cbSize: std::mem::size_of::<WNDCLASSEXW>() as u32,
+                style: 0,
+                lpfnWndProc: Some(session_wnd_proc),
+                cbClsExtra: 0,
+                cbWndExtra: 0,
+                hInstance: h_instance,
+                hIcon: 0,
+                hCursor: 0,
+                hbrBackground: 0,
+                lpszMenuName: std::ptr::null(),
+                lpszClassName: class_name.as_ptr(),
+                hIconSm: 0,
+            };
+
+            RegisterClassExW(&wcx);
+
+            let hwnd = CreateWindowExW(
+                0,
+                class_name.as_ptr(),
+                std::ptr::null(),
+                0,
+                0,
+                0,
+                0,
+                0,
+                -3, // HWND_MESSAGE
+                0,
+                h_instance,
+                std::ptr::null_mut(),
+            );
+
+            if hwnd == 0 {
+                let _ = hwnd_tx.send(0);
+                return;
+            }
+
+            WTSRegisterSessionNotification(hwnd, 0); // NOTIFY_FOR_THIS_SESSION = 0
+
+            let _ = hwnd_tx.send(hwnd);
+
+            let mut msg = std::mem::zeroed::<MSG>();
+            while GetMessageW(&mut msg, 0, 0, 0) > 0 {
+                TranslateMessage(&msg);
+                DispatchMessageW(&msg);
+            }
+
+            WTSUnRegisterSessionNotification(hwnd);
+            DestroyWindow(hwnd);
+            UnregisterClassW(class_name.as_ptr(), h_instance);
+        })
+        .context("Konnte Windows Session-Monitor-Thread nicht starten")?;
+
+    let hwnd = hwnd_rx
+        .recv()
+        .map_err(|e| anyhow::anyhow!("Session-Monitor-Thread initialisierte nicht rechtzeitig: {e}"))?;
+
+    if hwnd == 0 {
+        bail!("Win32-Nachrichtenfenster für Session-Lock konnte nicht erstellt werden");
+    }
+
+    Ok(SessionLockGuard {
+        hwnd,
+        join_handle: Some(join_handle),
+    })
+}
+
+#[cfg(not(windows))]
+pub fn start_session_lock_monitor(
+    _shutdown_tx: tokio::sync::mpsc::Sender<()>,
+) -> Result<SessionLockGuard> {
+    Ok(SessionLockGuard)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -198,4 +421,13 @@ mod tests {
         assert!(drive.is_ascii_alphabetic());
         assert!(drive >= 'D' && drive <= 'Z');
     }
+
+    #[test]
+    fn test_session_lock_monitor_lifecycle() {
+        let (tx, _rx) = tokio::sync::mpsc::channel(1);
+        let monitor = start_session_lock_monitor(tx);
+        assert!(monitor.is_ok());
+        // Dropping monitor closes message loop and joins thread cleanly
+        drop(monitor);
+    }
 }