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
 }