fix(vfs): V-03 — raii memory lock guard prevents premature memory unlock on fs clone

src/crypto.rs

@@ -104,7 +104,20 @@ pub fn check_password_prefix_collision(pass0: &str, pass1: &str) -> Result<()> {
 }
 
 /// Leitet aus dem Master-Passwort und dem Salt einen 256-Bit Key Encryption Key (KEK) via Argon2id ab.
-pub fn derive_kek(password: &str, salt: &[u8], params: &KdfParams) -> Result<Zeroizing<[u8; 32]>> {
+/// RAII-Guard für kurzzeitige Stack-Puffer, um Lock-Leaks bei Fehlern oder Rückgabe zu verhindern (V-03).
+struct ScopedMemoryLock(*const u8, usize);
+
+impl Drop for ScopedMemoryLock {
+    fn drop(&mut self) {
+        crate::windows::unlock_memory(self.0, self.1);
+    }
+}
+
+pub fn derive_kek(
+    password: &str,
+    salt: &[u8; 16],
+    params: &KdfParams,
+) -> Result<Zeroizing<[u8; 32]>> {
     validate_kdf_params(params)?;
 
     let argon2_params = Params::new(
@@ -118,12 +131,11 @@ pub fn derive_kek(password: &str, salt: &[u8], params: &KdfParams) -> Result<Zer
     let argon2 = Argon2::new(Algorithm::Argon2id, Version::V0x13, argon2_params);
     let mut kek = Zeroizing::new([0u8; 32]);
     let _ = crate::windows::lock_memory(kek.as_ptr(), 32);
+    let _lock_guard = ScopedMemoryLock(kek.as_ptr(), 32);
 
-    let res = argon2.hash_password_into(password.as_bytes(), salt, &mut *kek);
-    if let Err(e) = res {
-        let _ = crate::windows::unlock_memory(kek.as_ptr(), 32);
-        bail!("Argon2id KDF-Berechnung fehlgeschlagen: {e}");
-    }
+    argon2
+        .hash_password_into(password.as_bytes(), salt, &mut *kek)
+        .map_err(|e| anyhow::anyhow!("Argon2id KDF-Berechnung fehlgeschlagen: {e}"))?;
 
     Ok(kek)
 }
@@ -132,6 +144,7 @@ pub fn derive_kek(password: &str, salt: &[u8], params: &KdfParams) -> Result<Zer
 pub fn generate_dek() -> Zeroizing<[u8; 32]> {
     let mut dek = Zeroizing::new([0u8; 32]);
     let _ = crate::windows::lock_memory(dek.as_ptr(), 32);
+    let _lock_guard = ScopedMemoryLock(dek.as_ptr(), 32);
     OsRng.fill_bytes(&mut *dek);
     dek
 }

src/vfs.rs

@@ -94,6 +94,42 @@ impl DavDirEntry for SanctumDirEntry {
     }
 }
 
+/// RAII-Guard für im physischen RAM verriegelte Schlüssel (VirtualLock / mlock).
+/// Entriegelt den Speicherbereich via VirtualUnlock / munlock erst beim Drop der letzten verbleibenden Referenz (V-03).
+#[derive(Debug)]
+pub struct MemoryLockGuard(Zeroizing<[u8; 32]>);
+
+impl MemoryLockGuard {
+    pub fn new(key: Zeroizing<[u8; 32]>) -> Self {
+        crate::windows::lock_memory(key.as_ptr(), 32);
+        Self(key)
+    }
+
+    pub fn key(&self) -> &Zeroizing<[u8; 32]> {
+        &self.0
+    }
+}
+
+impl std::ops::Deref for MemoryLockGuard {
+    type Target = Zeroizing<[u8; 32]>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl AsRef<[u8; 32]> for MemoryLockGuard {
+    fn as_ref(&self) -> &[u8; 32] {
+        &self.0
+    }
+}
+
+impl Drop for MemoryLockGuard {
+    fn drop(&mut self) {
+        crate::windows::unlock_memory(self.0.as_ptr(), 32);
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Datei-Handle mit Streaming & Chunk-Pufferung
 // ---------------------------------------------------------------------------
@@ -103,7 +139,7 @@ pub struct SanctumFile {
     file_size: u64,
     cursor: u64,
     db: Database,
-    dek: Arc<Zeroizing<[u8; 32]>>,
+    dek: Arc<MemoryLockGuard>,
     meta: SanctumMetaData,
     // (chunk_index, decrypted_payload, is_dirty)
     cached_chunk: Option<(u32, Vec<u8>, bool)>,
@@ -126,7 +162,7 @@ impl SanctumFile {
     pub fn new(
         node: NodeRecord,
         db: Database,
-        dek: Arc<Zeroizing<[u8; 32]>>,
+        dek: Arc<MemoryLockGuard>,
         format_version: u32,
         last_activity: Arc<AtomicU64>,
         append: bool,
@@ -445,9 +481,9 @@ impl DavFile for SanctumFile {
 #[derive(Clone)]
 pub struct SanctumFs {
     db: Database,
-    dek: Arc<Zeroizing<[u8; 32]>>,
+    dek: Arc<MemoryLockGuard>,
     #[allow(dead_code)]
-    carrier_dek: Option<Arc<Zeroizing<[u8; 32]>>>,
+    carrier_dek: Option<Arc<MemoryLockGuard>>,
     carrier_node_id: Option<i64>,
     carrier_fs: Option<CarrierFs>,
     format_version: u32,
@@ -493,10 +529,10 @@ impl SanctumFs {
             .duration_since(UNIX_EPOCH)
             .map(|d| d.as_secs())
             .unwrap_or(0);
-        let dek_arc = Arc::new(dek);
-        let carrier_dek_arc = carrier_dek.map(Arc::new);
+        let dek_guard = Arc::new(MemoryLockGuard::new(dek));
+        let carrier_dek_guard = carrier_dek.map(|k| Arc::new(MemoryLockGuard::new(k)));
 
-        let db = db.with_session(vault_id, (*dek_arc).clone());
+        let db = db.with_session(vault_id, (*dek_guard.key()).clone());
 
         // Im Decoy-Vault (Slot 0): Stelle sicher, dass carrier_node_id stets bekannt ist,
         // um die Trägerdatei vor versehentlichem Löschen oder Überschreiben zu schützen.
@@ -509,12 +545,12 @@ impl SanctumFs {
         });
 
         let carrier_fs = if vault_id == 1 {
-            if let (Some(ref c_dek), Some(c_nid)) = (&carrier_dek_arc, carrier_node_id) {
+            if let (Some(ref c_dek), Some(c_nid)) = (&carrier_dek_guard, carrier_node_id) {
                 match CarrierFs::load(
                     db.clone(),
                     c_nid,
-                    c_dek.clone(),
-                    dek_arc.clone(),
+                    Arc::new((*c_dek.key()).clone()),
+                    Arc::new((*dek_guard.key()).clone()),
                     format_version,
                     anti_leak,
                 ) {
@@ -531,16 +567,10 @@ impl SanctumFs {
             None
         };
 
-        // Forensischer RAM-Paging-Schutz via VirtualLock (verhindert Auslagerung in pagefile.sys)
-        crate::windows::lock_memory(dek_arc.as_ptr(), 32);
-        if let Some(ref c_dek) = carrier_dek_arc {
-            crate::windows::lock_memory(c_dek.as_ptr(), 32);
-        }
-
         Self {
             db,
-            dek: dek_arc,
-            carrier_dek: carrier_dek_arc,
+            dek: dek_guard,
+            carrier_dek: carrier_dek_guard,
             carrier_node_id,
             carrier_fs,
             format_version,
@@ -550,6 +580,10 @@ impl SanctumFs {
         }
     }
 
+    pub fn dek_strong_count(&self) -> usize {
+        Arc::strong_count(&self.dek)
+    }
+
     pub fn vault_id(&self) -> u32 {
         self.vault_id
     }
@@ -636,15 +670,6 @@ pub fn validate_path_safety(path: &str) -> Result<(), FsError> {
     Ok(())
 }
 
-impl Drop for SanctumFs {
-    fn drop(&mut self) {
-        crate::windows::unlock_memory(self.dek.as_ptr(), 32);
-        if let Some(ref c_dek) = self.carrier_dek {
-            crate::windows::unlock_memory(c_dek.as_ptr(), 32);
-        }
-    }
-}
-
 impl DavFileSystem for SanctumFs {
     fn open<'a>(
         &'a self,

tests/mount_security_test.rs

@@ -154,3 +154,68 @@ fn test_mount_security_multi_auth_and_no_token_in_url() {
         "Saubere URI darf kein Token enthalten"
     );
 }
+
+#[tokio::test]
+async fn test_vfs_memory_lock_retention_on_clone_v03() {
+    use dav_server::davpath::DavPath;
+    use dav_server::fs::{DavFileSystem, ReadDirMeta};
+    use futures_util::StreamExt;
+    use sanctum::vfs::SanctumFs;
+
+    let temp_dir = std::env::temp_dir();
+    let container_path: PathBuf =
+        temp_dir.join(format!("test_v03_lock_{}.sanctum", std::process::id()));
+    if container_path.exists() {
+        let _ = std::fs::remove_file(&container_path);
+    }
+
+    let salt = generate_salt();
+    let kdf_params = KdfParams {
+        memory_cost: MIN_MEMORY_COST_KIB,
+        time_cost: MIN_TIME_COST,
+        parallelism: 1,
+    };
+    let kek = derive_kek("TestPassV03!", &salt, &kdf_params).unwrap();
+    let dek = generate_dek();
+    let (wrapped_dek, nonce, tag) = wrap_dek(&kek, &dek).unwrap();
+
+    let db = Database::open(&container_path).unwrap();
+    db.init_schema(&salt, &kdf_params, &wrapped_dek, &nonce, &tag)
+        .unwrap();
+
+    // 1. Initialisiere SanctumFs
+    let fs = SanctumFs::new(db.clone(), dek, sanctum::crypto::FORMAT_VERSION);
+    assert_eq!(
+        fs.dek_strong_count(),
+        1,
+        "Anfangs muss genau 1 Referenz auf den verriegelten DEK existieren"
+    );
+
+    // 2. Klone SanctumFs (wie bei jeder HTTP/WebDAV-Anfrage im Server)
+    let fs_clone = fs.clone();
+    assert_eq!(
+        fs.dek_strong_count(),
+        2,
+        "Nach dem Klonen müssen 2 Referenzen existieren"
+    );
+
+    // 3. Droppe den Klon
+    drop(fs_clone);
+
+    // 4. V-03: Der Refcount muss nun wieder 1 sein. Der Speicherbereich darf NICHT
+    // vorzeitig über Drop eines Klons entriegelt worden sein!
+    assert_eq!(
+        fs.dek_strong_count(),
+        1,
+        "Nach Drop des Klons muss genau 1 Referenz erhalten bleiben"
+    );
+
+    // Verifiziere funktionale Nutzbarkeit nach Drop des Klons
+    let root_path = DavPath::new("/").unwrap();
+    let mut entries = fs.read_dir(&root_path, ReadDirMeta::None).await.unwrap();
+    assert!(entries.next().await.is_none());
+
+    drop(fs);
+    let _ = std::fs::remove_file(&container_path);
+}
+