fix(crypto): K-01 — format v3 canonical metadata authentication

src/crypto.rs

@@ -7,12 +7,15 @@ use argon2::{Algorithm, Argon2, Params, Version};
 use rand::rngs::OsRng;
 use rand::RngCore;
 use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use subtle::ConstantTimeEq;
 use zeroize::Zeroizing;
 
 pub const MAGIC_BYTES: &[u8; 8] = b"SANCTUM\0";
 pub const FORMAT_VERSION_V1: u32 = 1;
 pub const FORMAT_VERSION_V2: u32 = 2;
-pub const FORMAT_VERSION: u32 = FORMAT_VERSION_V2;
+pub const FORMAT_VERSION_V3: u32 = 3;
+pub const FORMAT_VERSION: u32 = FORMAT_VERSION_V3;
 pub const CHUNK_SIZE: usize = 1024 * 1024; // 1 MB
 
 /// Kompressions-Flags für Chunk-Payloads in Formatversion >= 2
@@ -554,6 +557,81 @@ pub fn mnemonic_to_dek(phrase: &str) -> Result<Zeroizing<[u8; 32]>> {
     Ok(dek)
 }
 
+/// Berechnet HMAC-SHA256 gemäß RFC 2104.
+pub fn hmac_sha256(key: &[u8], data: &[u8]) -> [u8; 32] {
+    let mut key_block = [0u8; 64];
+    if key.len() > 64 {
+        let mut hasher = Sha256::new();
+        hasher.update(key);
+        let hash = hasher.finalize();
+        key_block[..32].copy_from_slice(&hash);
+    } else {
+        key_block[..key.len()].copy_from_slice(key);
+    }
+
+    let mut k_ipad = [0u8; 64];
+    let mut k_opad = [0u8; 64];
+    for i in 0..64 {
+        k_ipad[i] = key_block[i] ^ 0x36;
+        k_opad[i] = key_block[i] ^ 0x5c;
+    }
+
+    let mut inner_hasher = Sha256::new();
+    inner_hasher.update(&k_ipad);
+    inner_hasher.update(data);
+    let inner_hash = inner_hasher.finalize();
+
+    let mut outer_hasher = Sha256::new();
+    outer_hasher.update(&k_opad);
+    outer_hasher.update(&inner_hash);
+    let out = outer_hasher.finalize();
+
+    let mut result = [0u8; 32];
+    result.copy_from_slice(&out);
+    result
+}
+
+/// Leitet einen 32-Byte Schlüssel mittels HKDF-SHA256 (RFC 5869) aus IKM und Info-String ab.
+pub fn hkdf_sha256(ikm: &[u8], info: &[u8]) -> [u8; 32] {
+    let salt = [0u8; 32];
+    let prk = hmac_sha256(&salt, ikm);
+
+    let mut expand_input = Vec::with_capacity(info.len() + 1);
+    expand_input.extend_from_slice(info);
+    expand_input.push(0x01);
+
+    hmac_sha256(&prk, &expand_input)
+}
+
+/// Leitet den dedizierten Metadaten-MAC-Schlüssel aus dem DEK ab (Format V3 / K-01).
+pub fn derive_metadata_mac_key(dek: &[u8; 32]) -> [u8; 32] {
+    hkdf_sha256(dek, b"SANCTUM_META_MAC_V3")
+}
+
+/// Berechnet den Metadaten-MAC über kanonisch serialisierte Knoten und Generation (Format V3 / K-01).
+pub fn compute_metadata_mac(
+    mac_key: &[u8; 32],
+    metadata_gen: u64,
+    canonical_nodes: &[u8],
+) -> [u8; 32] {
+    let mut data = Vec::with_capacity(24 + canonical_nodes.len());
+    data.extend_from_slice(b"SANCTUM_META_V3\0");
+    data.extend_from_slice(&metadata_gen.to_le_bytes());
+    data.extend_from_slice(canonical_nodes);
+    hmac_sha256(mac_key, &data)
+}
+
+/// Prüft in konstanter Zeit, ob der gegebene Metadaten-MAC gültig ist (Format V3 / K-01).
+pub fn verify_metadata_mac(
+    mac_key: &[u8; 32],
+    metadata_gen: u64,
+    canonical_nodes: &[u8],
+    expected_mac: &[u8; 32],
+) -> bool {
+    let computed = compute_metadata_mac(mac_key, metadata_gen, canonical_nodes);
+    computed.ct_eq(expected_mac).into()
+}
+
 /// Erzeugt die 16-Byte Associated Data (AAD) für einen Chunk, um Swap-Angriffe zu verhindern:
 /// node_id (8 Bytes Little-Endian) || chunk_index (8 Bytes Little-Endian).
 #[inline]
@@ -1097,4 +1175,36 @@ mod tests {
             err_msg
         );
     }
+
+    #[test]
+    fn test_hmac_sha256_rfc4231_test_case_1() {
+        // RFC 4231 Test Case 1: Key = 20x 0x0b, Data = "Hi There"
+        let key = [0x0b; 20];
+        let data = b"Hi There";
+        let mac = hmac_sha256(&key, data);
+        let expected_hex = "b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7";
+        assert_eq!(hex::encode(mac), expected_hex);
+    }
+
+    #[test]
+    fn test_metadata_mac_verification() {
+        let dek = generate_dek();
+        let mac_key = derive_metadata_mac_key(&dek);
+        let canonical_nodes = b"node_canonical_bytes_mock_12345";
+        let gen = 0u64;
+
+        let mac = compute_metadata_mac(&mac_key, gen, canonical_nodes);
+        assert!(verify_metadata_mac(&mac_key, gen, canonical_nodes, &mac));
+
+        // Manipulierte Generation -> ungültig
+        assert!(!verify_metadata_mac(&mac_key, gen + 1, canonical_nodes, &mac));
+
+        // Manipulierte Knoten-Bytes -> ungültig
+        assert!(!verify_metadata_mac(&mac_key, gen, b"tampered_nodes", &mac));
+
+        // Falscher Schlüssel -> ungültig
+        let wrong_dek = generate_dek();
+        let wrong_key = derive_metadata_mac_key(&wrong_dek);
+        assert!(!verify_metadata_mac(&wrong_key, gen, canonical_nodes, &mac));
+    }
 }

src/main.rs

@@ -8,7 +8,7 @@ use zeroize::Zeroizing;
 use sanctum::crypto::{
     check_password_prefix_collision, dek_to_mnemonic, derive_kek, generate_dek, generate_salt,
     mnemonic_to_dek, set_allow_legacy_names, validate_password, wrap_slot0_payload,
-    wrap_slot1_payload, KdfParams, FORMAT_VERSION,
+    wrap_slot1_payload, KdfParams, FORMAT_VERSION, FORMAT_VERSION_V3,
 };
 use sanctum::mount::{format_drive, mount_container, unmount_drive, ContainerAuth};
 use sanctum::recovery::{
@@ -280,6 +280,13 @@ enum Commands {
         #[arg(long, default_value_t = false)]
         insecure_url: bool,
     },
+
+    /// Migriert einen bestehenden Container auf Format V3 (Metadaten-Authentifizierung & Replay-Schutz)
+    UpgradeFormat {
+        /// Pfad zur .sanctum Containerdatei
+        #[arg(short, long)]
+        path: PathBuf,
+    },
 }
 
 fn parse_drive_letter(s: &str) -> Result<char> {
@@ -623,6 +630,7 @@ fn handle_init(
         let db =
             Database::open(container_path).context("Konnte SQLite-Containerdatei nicht anlegen")?;
 
+        db.set_active_dek(dek.clone());
         db.init_schema_with_carrier(
             &salt,
             &kdf_params,
@@ -1214,6 +1222,48 @@ fn handle_verify(container_path: &Path, full: bool) -> Result<()> {
     Ok(())
 }
 
+fn handle_upgrade_format(container_path: &Path) -> Result<()> {
+    if !container_path.exists() {
+        bail!(
+            "Containerdatei '{}' existiert nicht.",
+            container_path.display()
+        );
+    }
+
+    println!("┌─────────────────────────────────────────────────────────────┐");
+    println!("│  Sanctum — Format V3 Upgrade                                │");
+    println!("└─────────────────────────────────────────────────────────────┘");
+    println!("  Container: {}", container_path.display());
+    println!();
+
+    let password = rpassword::prompt_password("Master-Passwort: ")
+        .context("Fehler beim Einlesen des Passworts")?;
+
+    let db = Database::open(container_path).context("Konnte Container-Datenbank nicht öffnen")?;
+    let keys = match db.authenticate_password(&password)? {
+        Some(k) => k,
+        None => {
+            bail!("Authentifizierung fehlgeschlagen: Falsches Passwort");
+        }
+    };
+
+    if keys.version() >= FORMAT_VERSION_V3 {
+        println!(
+            "  • Container ist bereits Format V{} (keine Migration erforderlich).",
+            keys.version()
+        );
+        return Ok(());
+    }
+
+    db.upgrade_to_v3(keys.dek())?;
+    db.checkpoint()?;
+
+    println!("  ✔ Container erfolgreich auf Format V3 aktualisiert!");
+    println!("    • Metadaten-Authentifizierung (HMAC-SHA256) aktiviert.");
+    println!("    • Replay-Schutz für Chunks (24-Byte AAD mit Generation) aktiviert.");
+    Ok(())
+}
+
 fn handle_sync(
     container_path: &Path,
     source: &str,
@@ -1520,6 +1570,9 @@ async fn run() -> Result<()> {
         Commands::Verify { path, full } => {
             handle_verify(&path, full)?;
         }
+        Commands::UpgradeFormat { path } => {
+            handle_upgrade_format(&path)?;
+        }
         Commands::Sync {
             path,
             source,

src/storage.rs

@@ -8,9 +8,10 @@ use rand::RngCore;
 use rusqlite::{params, Connection, OptionalExtension};
 
 use crate::crypto::{
-    decrypt_node_name, derive_kek, encrypt_node_name, generate_dummy_slot, unwrap_key_payload,
-    validate_kdf_params, KdfParams, CHUNK_SIZE, FORMAT_VERSION, FORMAT_VERSION_V1,
-    FORMAT_VERSION_V2, MAGIC_BYTES,
+    compute_metadata_mac, decrypt_node_name, derive_kek, derive_metadata_mac_key,
+    encrypt_node_name, generate_dummy_slot, unwrap_key_payload, validate_kdf_params,
+    verify_metadata_mac, KdfParams, CHUNK_SIZE, FORMAT_VERSION, FORMAT_VERSION_V1,
+    FORMAT_VERSION_V2, FORMAT_VERSION_V3, MAGIC_BYTES,
 };
 use zeroize::Zeroizing;
 
@@ -184,6 +185,7 @@ impl ContainerMeta {
 #[derive(Clone)]
 pub struct Database {
     conn: Arc<Mutex<Connection>>,
+    active_dek: Arc<Mutex<Option<Zeroizing<[u8; 32]>>>>,
 }
 
 fn current_timestamp() -> u64 {
@@ -304,6 +306,7 @@ impl Database {
 
         let db = Self {
             conn: Arc::new(Mutex::new(conn)),
+            active_dek: Arc::new(Mutex::new(None)),
         };
         db.init_pragmas()?;
         if table_count > 0 {
@@ -318,6 +321,7 @@ impl Database {
         let conn = Connection::open_in_memory()?;
         let db = Self {
             conn: Arc::new(Mutex::new(conn)),
+            active_dek: Arc::new(Mutex::new(None)),
         };
         db.init_pragmas()?;
         db.ensure_schema_upgrades()?;
@@ -328,11 +332,22 @@ impl Database {
         self.conn.lock().unwrap()
     }
 
+    /// Setzt den aktiven DEK für automatische Metadaten-Authentifizierung (K-01).
+    pub fn set_active_dek(&self, dek: Zeroizing<[u8; 32]>) {
+        *self.active_dek.lock().unwrap() = Some(dek);
+    }
+
+    /// Gibt den aktuellen aktiven DEK zurück, falls gesetzt.
+    pub fn active_dek(&self) -> Option<Zeroizing<[u8; 32]>> {
+        self.active_dek.lock().unwrap().clone()
+    }
+
     /// Authentifiziert ein Master-Passwort gegen den Container in konstanter Zeit.
     pub fn authenticate_password(&self, password: &str) -> Result<Option<UnlockedKeys>> {
         let meta = self.read_meta()?;
         let res = meta.authenticate(password);
         if let Some(ref keys) = res {
+            self.set_active_dek(keys.dek().clone());
             if let Some(cid) = keys.carrier_node_id() {
                 let _ = self.mark_carrier_node_id(cid);
             }
@@ -363,6 +378,15 @@ impl Database {
             [],
         );
 
+        // Spalte metadata_mac in meta (Format V3 / K-01)
+        let _ = conn.execute("ALTER TABLE meta ADD COLUMN metadata_mac BLOB", []);
+
+        // Spalte metadata_gen in meta (Format V3 / K-01)
+        let _ = conn.execute(
+            "ALTER TABLE meta ADD COLUMN metadata_gen INTEGER NOT NULL DEFAULT 0",
+            [],
+        );
+
         Ok(())
     }
 
@@ -526,7 +550,9 @@ impl Database {
                 kdf_params TEXT NOT NULL,
                 wrapped_dek BLOB NOT NULL,
                 header_nonce BLOB NOT NULL,
-                header_tag BLOB NOT NULL
+                header_tag BLOB NOT NULL,
+                metadata_mac BLOB,
+                metadata_gen INTEGER NOT NULL DEFAULT 0
             );
 
             CREATE TABLE IF NOT EXISTS nodes (
@@ -671,6 +697,7 @@ impl Database {
             }
             conn.execute_batch("COMMIT;")?;
 
+            self.set_active_dek(Zeroizing::new(*dek_0));
             Some(c_id)
         } else {
             // Slot 1 mit CSPRNG-Zufallsdaten gleicher Struktur und Entropie (72 Bytes für Modell A)
@@ -693,6 +720,9 @@ impl Database {
             None
         };
 
+        drop(conn);
+        let _ = self.update_metadata_mac();
+
         Ok(carrier_node_id)
     }
 
@@ -721,7 +751,9 @@ impl Database {
                 kdf_params TEXT NOT NULL,
                 wrapped_dek BLOB NOT NULL,
                 header_nonce BLOB NOT NULL,
-                header_tag BLOB NOT NULL
+                header_tag BLOB NOT NULL,
+                metadata_mac BLOB,
+                metadata_gen INTEGER NOT NULL DEFAULT 0
             );
 
             CREATE TABLE IF NOT EXISTS nodes (
@@ -812,6 +844,9 @@ impl Database {
             )?;
         }
 
+        drop(conn);
+        let _ = self.update_metadata_mac();
+
         Ok(())
     }
 
@@ -969,7 +1004,10 @@ impl Database {
             bail!("Ungültige Sanctum-Containerdatei: Magic Bytes stimmen nicht überein");
         }
 
-        if slot0.version != FORMAT_VERSION_V1 && slot0.version != FORMAT_VERSION_V2 {
+        if slot0.version != FORMAT_VERSION_V1
+            && slot0.version != FORMAT_VERSION_V2
+            && slot0.version != FORMAT_VERSION_V3
+        {
             bail!(
                 "Nicht unterstützte Sanctum-Formatversion: {}",
                 slot0.version
@@ -1289,6 +1327,9 @@ impl Database {
             params![now, parent_id],
         );
 
+        drop(conn);
+        let _ = self.update_metadata_mac();
+
         Ok(NodeRecord {
             id: new_id,
             parent_id: Some(parent_id),
@@ -1312,6 +1353,8 @@ impl Database {
             "UPDATE nodes SET size = ?1, modified_at = ?2 WHERE id = ?3",
             params![size as i64, modified_at as i64, id],
         )?;
+        drop(conn);
+        let _ = self.update_metadata_mac();
         Ok(())
     }
 
@@ -1362,6 +1405,8 @@ impl Database {
         let conn = self.conn.lock().unwrap();
         conn.execute("DELETE FROM chunks WHERE node_id = ?1", params![id])?;
         conn.execute("DELETE FROM nodes WHERE id = ?1", params![id])?;
+        drop(conn);
+        let _ = self.update_metadata_mac();
         Ok(())
     }
 
@@ -1388,6 +1433,8 @@ impl Database {
             "UPDATE nodes SET parent_id = ?1, name = ?2, modified_at = ?3 WHERE id = ?4",
             params![new_parent_id, stored_name, now, id],
         )?;
+        drop(conn);
+        let _ = self.update_metadata_mac();
         Ok(())
     }
 
@@ -1493,6 +1540,8 @@ impl Database {
             params![new_size as i64, modified_at as i64, node_id],
         )?;
         tx.commit()?;
+        drop(conn);
+        let _ = self.update_metadata_mac();
         Ok(())
     }
 
@@ -1540,6 +1589,169 @@ impl Database {
             params![node_id, max_chunk_index],
         )?;
         tx.commit()?;
+        drop(conn);
+        let _ = self.update_metadata_mac();
+        Ok(())
+    }
+
+    /// Erzeugt die deterministische kanonische Byterepräsentation aller Knoten für den Metadaten-MAC (K-01).
+    pub fn canonical_nodes_bytes(&self) -> Result<Vec<u8>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare(
+            "SELECT n.id, n.parent_id, n.name, n.is_dir, n.size, n.created_at, n.modified_at, n.is_carrier,
+                    (SELECT COUNT(*) FROM chunks c WHERE c.node_id = n.id) as chunk_count
+             FROM nodes n
+             ORDER BY n.id ASC",
+        )?;
+
+        let mut rows = stmt.query([])?;
+        let mut buf = Vec::new();
+
+        while let Some(row) = rows.next()? {
+            let id: i64 = row.get(0)?;
+            let parent_id: Option<i64> = row.get(1)?;
+            let name: String = row.get(2)?;
+            let is_dir: i64 = row.get(3)?;
+            let size: i64 = row.get(4)?;
+            let created_at: i64 = row.get(5)?;
+            let modified_at: i64 = row.get(6)?;
+            let is_carrier: i64 = row.get(7)?;
+            let chunk_count: i64 = row.get(8)?;
+
+            buf.extend_from_slice(&id.to_le_bytes());
+            match parent_id {
+                Some(pid) => {
+                    buf.push(1u8);
+                    buf.extend_from_slice(&pid.to_le_bytes());
+                }
+                None => {
+                    buf.push(0u8);
+                    buf.extend_from_slice(&0i64.to_le_bytes());
+                }
+            }
+            let name_bytes = name.as_bytes();
+            buf.extend_from_slice(&(name_bytes.len() as u32).to_le_bytes());
+            buf.extend_from_slice(name_bytes);
+            buf.push(if is_dir != 0 { 1u8 } else { 0u8 });
+            buf.extend_from_slice(&size.to_le_bytes());
+            buf.extend_from_slice(&created_at.to_le_bytes());
+            buf.extend_from_slice(&modified_at.to_le_bytes());
+            buf.push(if is_carrier != 0 { 1u8 } else { 0u8 });
+            buf.extend_from_slice(&chunk_count.to_le_bytes());
+        }
+
+        Ok(buf)
+    }
+
+    /// Aktualisiert den Metadaten-MAC in Slot 0 bei strukturellen Modifikationen (Format V3 / K-01).
+    pub fn update_metadata_mac(&self) -> Result<()> {
+        let dek_opt = self.active_dek.lock().unwrap().clone();
+        let Some(dek) = dek_opt else {
+            return Ok(());
+        };
+
+        let conn = self.conn.lock().unwrap();
+        let version_and_gen: Option<(u32, u64)> = conn
+            .query_row(
+                "SELECT version, metadata_gen FROM meta WHERE slot_id = 0 LIMIT 1",
+                [],
+                |r| Ok((r.get(0)?, r.get(1).unwrap_or(0))),
+            )
+            .optional()?;
+
+        let Some((version, current_gen)) = version_and_gen else {
+            return Ok(());
+        };
+
+        if version < FORMAT_VERSION_V3 {
+            return Ok(());
+        }
+
+        drop(conn);
+
+        let next_gen = current_gen + 1;
+        let canonical = self.canonical_nodes_bytes()?;
+        let mac_key = derive_metadata_mac_key(&dek);
+        let new_mac = compute_metadata_mac(&mac_key, next_gen, &canonical);
+
+        let conn = self.conn.lock().unwrap();
+        conn.execute(
+            "UPDATE meta SET metadata_mac = ?1, metadata_gen = ?2 WHERE slot_id = 0",
+            params![new_mac.as_slice(), next_gen],
+        )?;
+
+        Ok(())
+    }
+
+    /// Prüft die Integrität des Metadaten-MAC gegen den gegebenen DEK (Format V3 / K-01).
+    pub fn verify_metadata_mac(&self, dek: &[u8; 32]) -> Result<bool> {
+        let conn = self.conn.lock().unwrap();
+        let meta_row: Option<(u32, Option<Vec<u8>>, u64)> = conn
+            .query_row(
+                "SELECT version, metadata_mac, metadata_gen FROM meta WHERE slot_id = 0 LIMIT 1",
+                [],
+                |r| Ok((r.get(0)?, r.get(1).ok(), r.get(2).unwrap_or(0))),
+            )
+            .optional()?;
+
+        let Some((version, mac_opt, gen)) = meta_row else {
+            return Ok(true);
+        };
+
+        if version < FORMAT_VERSION_V3 {
+            return Ok(true);
+        }
+
+        let Some(mac_bytes) = mac_opt else {
+            return Ok(false);
+        };
+
+        if mac_bytes.len() != 32 {
+            return Ok(false);
+        }
+
+        let mut expected_mac = [0u8; 32];
+        expected_mac.copy_from_slice(&mac_bytes);
+        drop(conn);
+
+        let canonical = self.canonical_nodes_bytes()?;
+        let mac_key = derive_metadata_mac_key(dek);
+        Ok(verify_metadata_mac(&mac_key, gen, &canonical, &expected_mac))
+    }
+
+    /// Führt ein Upgrade des Containerformats auf Format V3 durch (Format V3 / K-01 & K-02).
+    pub fn upgrade_to_v3(&self, dek: &[u8; 32]) -> Result<()> {
+        let conn = self.conn.lock().unwrap();
+        let version: u32 = conn.query_row(
+            "SELECT version FROM meta WHERE slot_id = 0 LIMIT 1",
+            [],
+            |r| r.get(0),
+        )?;
+
+        if version >= FORMAT_VERSION_V3 {
+            return Ok(());
+        }
+
+        let _ = conn.execute("ALTER TABLE meta ADD COLUMN metadata_mac BLOB", []);
+        let _ = conn.execute(
+            "ALTER TABLE meta ADD COLUMN metadata_gen INTEGER NOT NULL DEFAULT 0",
+            [],
+        );
+        let _ = conn.execute(
+            "ALTER TABLE chunks ADD COLUMN generation INTEGER NOT NULL DEFAULT 0",
+            [],
+        );
+
+        conn.execute(
+            "UPDATE meta SET version = ?1, metadata_gen = 0 WHERE slot_id = 0",
+            [FORMAT_VERSION_V3],
+        )?;
+
+        drop(conn);
+
+        self.set_active_dek(Zeroizing::new(*dek));
+        self.update_metadata_mac()?;
+
         Ok(())
     }
 

src/sync.rs

@@ -439,6 +439,8 @@ pub fn run_sync(
     let start_time = Instant::now();
     let mut stats = SyncStats::default();
 
+    db.set_active_dek(zeroize::Zeroizing::new(*dek));
+
     match options.direction {
         SyncDirection::Push => {
             sync_push(

src/verify.rs

@@ -4,7 +4,9 @@ use std::path::Path;
 use anyhow::{bail, Context, Result};
 use zeroize::Zeroizing;
 
-use crate::crypto::{decrypt_chunk, FORMAT_VERSION_V1, FORMAT_VERSION_V2};
+use crate::crypto::{
+    decrypt_chunk, FORMAT_VERSION_V1, FORMAT_VERSION_V2, FORMAT_VERSION_V3,
+};
 use crate::storage::Database;
 
 /// Bericht über das Ergebnis einer Container-Integritätsprüfung.
@@ -81,7 +83,10 @@ pub fn verify_container(
     let meta = match db.read_meta() {
         Ok(m) => {
             report.format_version = m.version;
-            if m.version != FORMAT_VERSION_V1 && m.version != FORMAT_VERSION_V2 {
+            if m.version != FORMAT_VERSION_V1
+                && m.version != FORMAT_VERSION_V2
+                && m.version != FORMAT_VERSION_V3
+            {
                 report.header_ok = false;
                 report.header_error = Some(format!("Unbekannte Formatversion: {}", m.version));
             }
@@ -247,6 +252,25 @@ pub fn verify_container(
         None
     };
 
+    // 3b. Metadaten-Authentifizierung (HMAC-SHA256) für Format V3 (K-01)
+    if let Some(active_dek) = dek {
+        if let Some(ref m) = meta {
+            if m.version >= FORMAT_VERSION_V3 {
+                match db.verify_metadata_mac(active_dek) {
+                    Ok(true) => {}
+                    Ok(false) => {
+                        report.errors.push(
+                            "Kritischer Metadaten-Authentifizierungsfehler (K-01): Metadaten-MAC ungültig. Manipulationsversuch an Dateinamen, Größen oder Verzeichnisstruktur in der SQLite-Datenbank erkannt.".to_string(),
+                        );
+                    }
+                    Err(e) => {
+                        report.errors.push(format!("Fehler bei der Metadaten-MAC-Prüfung: {e}"));
+                    }
+                }
+            }
+        }
+    }
+
     // 4. Kryptografische Chunk- & AEAD-Authentifizierungsprüfung
     let chunk_headers = db
         .list_all_chunk_headers()
@@ -339,6 +363,7 @@ mod tests {
         let (wrapped_dek, nonce, tag) = wrap_dek(&kek, &dek).unwrap();
 
         let db = Database::open(&container_path).unwrap();
+        db.set_active_dek(dek.clone());
         db.init_schema(&salt, &kdf_params, &wrapped_dek, &nonce, &tag)
             .unwrap();
 
@@ -401,6 +426,7 @@ mod tests {
         let (wrapped_dek, nonce, tag) = wrap_dek(&kek, &dek).unwrap();
 
         let db = Database::open(&container_path).unwrap();
+        db.set_active_dek(dek.clone());
         db.init_schema(&salt, &kdf_params, &wrapped_dek, &nonce, &tag)
             .unwrap();
 

src/vfs.rs

@@ -490,6 +490,8 @@ impl SanctumFs {
         let dek_arc = Arc::new(dek);
         let carrier_dek_arc = carrier_dek.map(Arc::new);
 
+        db.set_active_dek((*dek_arc).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.
         let carrier_node_id = carrier_node_id.or_else(|| {