feat(resilience): implement CHAOS-01 to CHAOS-03 crash consistency and input guards

- CHAOS-01: write chunk and update node size atomically via write_chunk_and_update_size in a single SQLite transaction
- CHAOS-02: reject null-bytes and ASCII control characters in VFS paths and node names via validate_path_safety
- CHAOS-03: invalidate in-memory chunk cache on I/O and disk-full errors to prevent drop failure cascades

src/storage.rs

@@ -1200,6 +1200,43 @@ impl Database {
         Ok(())
     }
 
+    /// Schreibt einen verschlüsselten Chunk und aktualisiert Dateigröße und Modifikationszeitstempel atomar
+    /// in einer einzigen SQLite-Transaktion (Crash-Konsistenz / Power-Loss Schutz / CHAOS-01).
+    pub fn write_chunk_and_update_size(
+        &self,
+        node_id: i64,
+        chunk_index: u32,
+        nonce: &[u8; 12],
+        tag: &[u8; 16],
+        ciphertext: &[u8],
+        new_size: u64,
+        modified_at: u64,
+    ) -> Result<()> {
+        let mut conn = self.conn.lock().unwrap();
+        let tx = conn.transaction()?;
+        tx.execute(
+            "INSERT INTO chunks (node_id, chunk_index, nonce, tag, ciphertext)
+             VALUES (?1, ?2, ?3, ?4, ?5)
+             ON CONFLICT(node_id, chunk_index) DO UPDATE SET
+                nonce = excluded.nonce,
+                tag = excluded.tag,
+                ciphertext = excluded.ciphertext",
+            params![
+                node_id,
+                chunk_index,
+                nonce.as_slice(),
+                tag.as_slice(),
+                ciphertext,
+            ],
+        )?;
+        tx.execute(
+            "UPDATE nodes SET size = ?1, modified_at = ?2 WHERE id = ?3",
+            params![new_size as i64, modified_at as i64, node_id],
+        )?;
+        tx.commit()?;
+        Ok(())
+    }
+
     /// Schneidet überzählige Chunks ab (z. B. beim Truncate oder Überschreiben mit kleinerer Datei)
     /// und shreddert die abzuschneidenden Chunks vorher mit kryptografischem Zufallsrauschen.
     pub fn truncate_chunks_after(&self, node_id: i64, max_chunk_index: u32) -> Result<()> {
@@ -1709,4 +1746,48 @@ mod tests {
         ).unwrap();
         assert_eq!(has_vault_id_chunks, 0, "vault_id darf nicht in chunks existieren");
     }
+
+    #[test]
+    fn test_atomic_chunk_write_and_size_update() {
+        let db = Database::open_in_memory().unwrap();
+        let (salt, kdf, wrapped_dek, nonce, tag) = (
+            [1u8; 16],
+            KdfParams::default(),
+            vec![2u8; 40],
+            [3u8; 12],
+            [4u8; 16],
+        );
+        db.init_schema(&salt, &kdf, &wrapped_dek, &nonce, &tag).unwrap();
+
+        let file = db.create_node(1, "crash_test.bin", false).unwrap();
+        assert_eq!(file.size, 0);
+
+        let chunk_nonce = [5u8; 12];
+        let chunk_tag = [6u8; 16];
+        let ciphertext = vec![7u8; 1024];
+        let new_size = 1024u64;
+        let modified_at = 2000000u64;
+
+        db.write_chunk_and_update_size(
+            file.id,
+            0,
+            &chunk_nonce,
+            &chunk_tag,
+            &ciphertext,
+            new_size,
+            modified_at,
+        ).expect("Atomic write");
+
+        // Chunk verifizieren
+        let chunk = db.read_chunk(file.id, 0).unwrap().expect("Chunk must exist");
+        assert_eq!(chunk.ciphertext, ciphertext);
+        assert_eq!(chunk.nonce, chunk_nonce);
+        assert_eq!(chunk.tag, chunk_tag);
+
+        // Inode verifizieren
+        let nodes = db.list_children(1).unwrap();
+        let updated_file = nodes.iter().find(|n| n.id == file.id).unwrap();
+        assert_eq!(updated_file.size, new_size);
+        assert_eq!(updated_file.modified_at, modified_at);
+    }
 }

src/vfs.rs

@@ -168,8 +168,15 @@ impl SanctumFile {
     }
 
 
-    /// Schreibt den aktuell im RAM gehaltenen Chunk verschlüsselt in die SQLite-Datenbank zurück.
-    fn flush_cached_chunk(&mut self) -> Result<(), FsError> {
+    /// Schreibt den aktuell im RAM gehaltenen Chunk verschlüsselt in die SQLite-Datenbank zurück
+    /// und aktualisiert Dateigröße und Modifikationszeitstempel atomar in einer Transaktion (CHAOS-01).
+    /// Bei Fehlern (z. B. Disk Full) wird der Cache sauber invalidiert (CHAOS-03).
+    fn flush_cached_chunk_and_size(&mut self) -> Result<(), FsError> {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
+
         if let Some((idx, ref data, true)) = self.cached_chunk {
             let (ciphertext, nonce, tag) =
                 encrypt_chunk(&self.dek, self.node_id, idx, data, self.format_version).map_err(|e| {
@@ -177,16 +184,35 @@ impl SanctumFile {
                     FsError::GeneralFailure
                 })?;
 
-            self.db
-                .write_chunk(self.node_id, idx, &nonce, &tag, &ciphertext)
-                .map_err(|e| {
-                    error!("DB-Fehler beim Schreiben des Chunks: {e}");
-                    FsError::GeneralFailure
-                })?;
+            if let Err(e) = self.db.write_chunk_and_update_size(
+                self.node_id,
+                idx,
+                &nonce,
+                &tag,
+                &ciphertext,
+                self.file_size,
+                now,
+            ) {
+                error!("DB-Fehler beim atomaren Chunk- und Size-Write #{idx}: {e}");
+                // CHAOS-03: Bei I/O- oder Disk-Full-Fehlern den Cache sauber invalidieren,
+                // um Folgefehler und Panic-/Warnungsschleifen beim Drop zu unterbinden!
+                self.cached_chunk = None;
+                return Err(FsError::GeneralFailure);
+            }
 
             if let Some((_, _, ref mut dirty)) = self.cached_chunk {
                 *dirty = false;
             }
+            self.meta.size = self.file_size;
+            self.meta.modified_at = UNIX_EPOCH + Duration::from_secs(now);
+        } else if self.meta.size != self.file_size {
+            // Falls kein Chunk dirty war, aber sich z. B. die Dateigröße durch Truncate geändert hat
+            if let Err(e) = self.db.update_node_size_and_time(self.node_id, self.file_size, now) {
+                error!("Fehler beim Aktualisieren der Knotengröße: {e}");
+                return Err(FsError::GeneralFailure);
+            }
+            self.meta.size = self.file_size;
+            self.meta.modified_at = UNIX_EPOCH + Duration::from_secs(now);
         }
         Ok(())
     }
@@ -199,7 +225,7 @@ impl SanctumFile {
         };
 
         if !is_current {
-            self.flush_cached_chunk()?;
+            self.flush_cached_chunk_and_size()?;
             if let Some((_, ref mut data, _)) = self.cached_chunk {
                 data.zeroize();
             }
@@ -236,17 +262,12 @@ impl SanctumFile {
 
 impl Drop for SanctumFile {
     fn drop(&mut self) {
-        if let Err(e) = self.flush_cached_chunk() {
+        if let Err(e) = self.flush_cached_chunk_and_size() {
             warn!("Fehler beim automatischen Flush im SanctumFile::drop: {:?}", e);
         }
         if let Some((_, ref mut data, _)) = self.cached_chunk {
             data.zeroize();
         }
-        let now = SystemTime::now()
-            .duration_since(UNIX_EPOCH)
-            .map(|d| d.as_secs())
-            .unwrap_or(0);
-        let _ = self.db.update_node_size_and_time(self.node_id, self.file_size, now);
     }
 }
 
@@ -334,7 +355,7 @@ impl DavFile for SanctumFile {
 
                 // Wenn der Chunk exakt 1 MB erreicht hat, sofort flushen, um RAM zu schonen
                 if self.cached_chunk.as_ref().map(|(_, d, _)| d.len() >= CHUNK_SIZE).unwrap_or(false) {
-                    self.flush_cached_chunk()?;
+                    self.flush_cached_chunk_and_size()?;
                 }
 
                 src = &src[to_write..];
@@ -370,19 +391,7 @@ impl DavFile for SanctumFile {
     fn flush(&mut self) -> FsFuture<'_, ()> {
         self.touch();
         Box::pin(async move {
-            self.flush_cached_chunk()?;
-            let now = SystemTime::now()
-                .duration_since(UNIX_EPOCH)
-                .map(|d| d.as_secs())
-                .unwrap_or(0);
-            self.db
-                .update_node_size_and_time(self.node_id, self.file_size, now)
-                .map_err(|e| {
-                    error!("Fehler beim Aktualisieren der Knotengröße: {e}");
-                    FsError::GeneralFailure
-                })?;
-            self.meta.size = self.file_size;
-            self.meta.modified_at = UNIX_EPOCH + Duration::from_secs(now);
+            self.flush_cached_chunk_and_size()?;
             Ok(())
         })
     }
@@ -539,6 +548,7 @@ impl SanctumFs {
     }
 
     fn resolve_path(&self, path: &str) -> Result<Option<NodeRecord>, FsError> {
+        validate_path_safety(path)?;
         self.db
             .resolve_path_in_vault(path, self.vault_id, &self.dek)
             .map_err(|_| FsError::GeneralFailure)
@@ -551,6 +561,7 @@ impl SanctumFs {
     }
 
     fn create_node(&self, parent_id: i64, name: &str, is_dir: bool) -> Result<NodeRecord, FsError> {
+        validate_path_safety(name)?;
         self.db
             .create_node_in_vault(self.vault_id, parent_id, name, is_dir, &self.dek)
             .map_err(|e| {
@@ -560,12 +571,26 @@ impl SanctumFs {
     }
 
     fn rename_node(&self, id: i64, new_parent_id: i64, new_name: &str) -> Result<(), FsError> {
+        validate_path_safety(new_name)?;
         self.db
             .rename_node_in_vault(id, new_parent_id, new_name, self.vault_id, &self.dek)
             .map_err(|_| FsError::GeneralFailure)
     }
 }
 
+/// Validiert, dass ein Pfad oder Dateiname keine Null-Bytes oder unzulässige Steuerzeichen enthält (CHAOS-02).
+pub fn validate_path_safety(path: &str) -> Result<(), FsError> {
+    if path.contains('\0') {
+        return Err(FsError::Forbidden);
+    }
+    for c in path.chars() {
+        if (c as u32) < 0x20 && c != '\t' {
+            return Err(FsError::Forbidden);
+        }
+    }
+    Ok(())
+}
+
 impl Drop for SanctumFs {
     fn drop(&mut self) {
         crate::windows::unlock_memory(self.dek.as_ptr(), 32);
@@ -1224,4 +1249,48 @@ mod tests {
             Err(FsError::Forbidden)
         ));
     }
+
+    #[tokio::test]
+    async fn test_path_safety_rejects_null_bytes_and_control_chars() {
+        let (fs, _dir) = create_test_fs(true);
+
+        // 1. Null-Byte im Pfad
+        let null_path = DavPath::new("/bad\0file.txt");
+        assert!(null_path.is_err() || fs.open(&null_path.unwrap(), OpenOptions::default()).await.is_err());
+        assert!(validate_path_safety("/bad\0file.txt").is_err());
+
+        // 2. Steuerzeichen < 0x20
+        assert!(validate_path_safety("/bad\x01file.txt").is_err());
+        assert!(validate_path_safety("/bad\rfile.txt").is_err());
+        assert!(validate_path_safety("/bad\nfile.txt").is_err());
+
+        // 3. Gültiger Pfad
+        assert!(validate_path_safety("/normal_file_123.txt").is_ok());
+        assert!(validate_path_safety("/path/to/subfolder/file.pdf").is_ok());
+    }
+
+    #[tokio::test]
+    async fn test_write_atomic_and_cache_invalidation() {
+        let (fs, _dir) = create_test_fs(true);
+        let path = DavPath::new("/atomic_test.bin").unwrap();
+
+        let mut opts = OpenOptions::default();
+        opts.write = true;
+        opts.create_new = true;
+        let mut file = fs.open(&path, opts).await.unwrap();
+
+        // 1. Schreibe 500 Bytes
+        let payload = Bytes::from(vec![42u8; 500]);
+        file.write_buf(Box::new(std::io::Cursor::new(payload))).await.unwrap();
+
+        // 2. Expliziter Flush: muss Chunk & Dateigröße atomar persistieren
+        file.flush().await.unwrap();
+
+        let node = fs.resolve_path("/atomic_test.bin").unwrap().unwrap();
+        assert_eq!(node.size, 500);
+
+        // Chunk in DB prüfen
+        let chunk = fs.db.read_chunk(node.id, 0).unwrap().unwrap();
+        assert!(!chunk.ciphertext.is_empty());
+    }
 }