feat(security): implement Phase 2 Modell A (Steganografischer Alibi-Carrier für Plausible Deniability)

2026-09-09 20:22:00 +02:00
parent b8e4dcb614
commit 030ce6a1e5
8 changed files with 1971 additions and 73 deletions
@@ -0,0 +1,360 @@
+use std::path::PathBuf;
+
+use bytes::Bytes;
+use dav_server::davpath::DavPath;
+use dav_server::fs::{DavFileSystem, FsError, OpenOptions, ReadDirMeta};
+use rand::rngs::OsRng;
+use rand::RngCore;
+
+use sanctum::crypto::{
+    derive_kek, generate_dek, generate_salt, wrap_slot0_payload,
+    wrap_slot1_payload, KdfParams, CHUNK_SIZE,
+};
+use sanctum::storage::Database;
+use sanctum::verify::verify_container;
+use sanctum::vfs::SanctumFs;
+
+fn temp_db_path(prefix: &str) -> PathBuf {
+    let mut path = std::env::temp_dir();
+    let id: u64 = OsRng.next_u64();
+    path.push(format!("sanctum_test_{}_{}.sanctum", prefix, id));
+    path
+}
+
+#[tokio::test]
+async fn test_model_a_carrier_filesystem_and_accounting_attack_resistance() {
+    let path = temp_db_path("carrier_accounting");
+    let carrier_size_bytes = 10 * 1024 * 1024; // 10 MB (10 Blöcke à 1 MB)
+    let carrier_name = "backup_image.iso";
+
+    let pass_decoy = "DecoyPassword2026!";
+    let pass_hidden = "SuperSecretHiddenPassword2026!";
+
+    let kdf_params = KdfParams {
+        memory_cost: 1024,
+        time_cost: 1,
+        parallelism: 1,
+    };
+
+    let salt_0 = generate_salt();
+    let kek_0 = derive_kek(pass_decoy, &salt_0, &kdf_params).unwrap();
+    let dek_0 = generate_dek();
+
+    let salt_1 = generate_salt();
+    let kek_1 = derive_kek(pass_hidden, &salt_1, &kdf_params).unwrap();
+    let dek_1 = generate_dek();
+
+    let carrier_node_id = 3i64;
+    let (wrapped_0, nonce_0, tag_0) =
+        wrap_slot0_payload(&kek_0, &dek_0, carrier_node_id).unwrap();
+    let (wrapped_1, nonce_1, tag_1) =
+        wrap_slot1_payload(&kek_1, &dek_1, &dek_0, carrier_node_id).unwrap();
+
+    let db = Database::open(&path).expect("Open database");
+
+    let created_cid = db
+        .init_schema_with_carrier(
+            &salt_0,
+            &kdf_params,
+            &wrapped_0,
+            &nonce_0,
+            &tag_0,
+            Some((
+                carrier_name,
+                carrier_size_bytes,
+                &salt_1,
+                &kdf_params,
+                &wrapped_1,
+                &nonce_1,
+                &tag_1,
+                &dek_0,
+                &dek_1,
+            )),
+        )
+        .expect("Init carrier schema");
+
+    db.checkpoint().unwrap();
+    assert_eq!(created_cid, Some(carrier_node_id));
+
+    // 1. Authentifizierung beider Passwörter
+    let meta = db.read_meta().unwrap();
+    let auth_decoy = meta.authenticate(pass_decoy).expect("Auth decoy");
+    assert_eq!(auth_decoy.slot_id(), 0);
+    assert_eq!(**auth_decoy.dek(), *dek_0);
+    assert_eq!(auth_decoy.carrier_node_id(), Some(carrier_node_id));
+
+    let auth_hidden = meta.authenticate(pass_hidden).expect("Auth hidden");
+    assert_eq!(auth_hidden.slot_id(), 1);
+    assert_eq!(**auth_hidden.dek(), *dek_1);
+    assert_eq!(*auth_hidden.carrier_dek().unwrap(), *dek_0);
+    assert_eq!(auth_hidden.carrier_node_id(), Some(carrier_node_id));
+
+    // 2. Decoy Mount: Schutz der Alibi-Datei (backup_image.iso)
+    let decoy_fs = SanctumFs::with_carrier(
+        db.clone(),
+        auth_decoy.dek().clone(),
+        auth_decoy.carrier_dek(),
+        auth_decoy.carrier_node_id(),
+        auth_decoy.version(),
+        true,
+        0,
+    );
+
+    let carrier_path = DavPath::new("/backup_image.iso").unwrap();
+
+    // Metadaten der Alibi-Datei im Decoy prüfen
+    let carrier_meta = decoy_fs.metadata(&carrier_path).await.expect("Carrier meta");
+    assert_eq!(carrier_meta.len(), carrier_size_bytes);
+    assert!(!carrier_meta.is_dir());
+
+    // Alibi-Datei darf im Decoy-Mount NICHT zum Schreiben geöffnet werden
+    let write_opts = OpenOptions {
+        write: true,
+        ..Default::default()
+    };
+    assert!(
+        matches!(decoy_fs.open(&carrier_path, write_opts).await, Err(FsError::Forbidden)),
+        "Alibi-Datei darf nicht zum Schreiben geöffnet werden"
+    );
+
+    // Alibi-Datei darf im Decoy-Mount NICHT gelöscht werden
+    assert!(
+        matches!(decoy_fs.remove_file(&carrier_path).await, Err(FsError::Forbidden)),
+        "Alibi-Datei darf nicht gelöscht werden"
+    );
+
+    // Alibi-Datei darf im Decoy-Mount NICHT umbenannt werden
+    let new_name = DavPath::new("/renamed.iso").unwrap();
+    assert!(
+        matches!(decoy_fs.rename(&carrier_path, &new_name).await, Err(FsError::Forbidden)),
+        "Alibi-Datei darf nicht umbenannt werden"
+    );
+
+    // Alibi-Datei KANN im Decoy-Mount gelesen werden
+    let read_opts = OpenOptions {
+        read: true,
+        ..Default::default()
+    };
+    let mut file_reader = decoy_fs.open(&carrier_path, read_opts).await.expect("Open read");
+    let first_mb = file_reader.read_bytes(CHUNK_SIZE).await.expect("Read first chunk");
+    assert_eq!(first_mb.len(), CHUNK_SIZE);
+
+    // 3. Hidden Mount: Dateisystem-Operationen innerhalb des Alibi-Carriers
+    let hidden_fs = SanctumFs::with_carrier(
+        db.clone(),
+        auth_hidden.dek().clone(),
+        auth_hidden.carrier_dek(),
+        auth_hidden.carrier_node_id(),
+        auth_hidden.version(),
+        true,
+        1,
+    );
+
+    // Wurzelverzeichnis des Hidden Vault auflisten (anfangs leer)
+    let root_path = DavPath::new("/").unwrap();
+    let mut stream = hidden_fs
+        .read_dir(&root_path, ReadDirMeta::None)
+        .await
+        .expect("Read dir root");
+    use futures_util::StreamExt;
+    let mut entries = Vec::new();
+    while let Some(item) = stream.next().await {
+        entries.push(item.unwrap().name());
+    }
+    assert!(entries.is_empty(), "Hidden Vault Wurzelverzeichnis muss anfangs leer sein");
+
+    // Ordner erstellen
+    let secret_dir = DavPath::new("/Classified").unwrap();
+    hidden_fs.create_dir(&secret_dir).await.expect("Create Classified dir");
+
+    // Datei im Ordner anlegen und schreiben
+    let secret_file_path = DavPath::new("/Classified/passwords.txt").unwrap();
+    let create_opts = OpenOptions {
+        create: true,
+        write: true,
+        ..Default::default()
+    };
+    let mut secret_file = hidden_fs
+        .open(&secret_file_path, create_opts)
+        .await
+        .expect("Create secret file");
+
+    let secret_content = b"TopSecretCredentials_2026_SanctumCoreSecureVault";
+    secret_file
+        .write_bytes(Bytes::from_static(secret_content))
+        .await
+        .expect("Write secret content");
+    secret_file.flush().await.expect("Flush secret file");
+    drop(secret_file);
+
+    // Datei lesen und verifizieren
+    let read_opts = OpenOptions {
+        read: true,
+        ..Default::default()
+    };
+    let mut read_handle = hidden_fs
+        .open(&secret_file_path, read_opts)
+        .await
+        .expect("Open secret file for read");
+    let read_data = read_handle.read_bytes(1024).await.expect("Read secret bytes");
+    assert_eq!(&read_data[..], secret_content);
+    drop(read_handle);
+
+    // Größere Binärdatei schreiben (über 2 MB = 2 Blöcke)
+    let big_file_path = DavPath::new("/Classified/payload.bin").unwrap();
+    let mut big_file = hidden_fs
+        .open(&big_file_path, OpenOptions { create: true, write: true, ..Default::default() })
+        .await
+        .expect("Create big file");
+
+    let payload_size = 2 * 1024 * 1024 + 12345; // 2 MB + 12.345 Bytes
+    let mut payload = vec![0u8; payload_size];
+    OsRng.fill_bytes(&mut payload);
+
+    big_file.write_bytes(Bytes::copy_from_slice(&payload)).await.expect("Write big payload");
+    big_file.flush().await.expect("Flush big file");
+    drop(big_file);
+
+    // Datei zurücklesen und Bit-für-Bit verifizieren
+    let mut read_big = hidden_fs
+        .open(&big_file_path, OpenOptions { read: true, ..Default::default() })
+        .await
+        .expect("Open big file");
+    let read_big_bytes = read_big.read_bytes(payload_size + 100).await.expect("Read big file bytes");
+    assert_eq!(read_big_bytes.len(), payload_size);
+    assert_eq!(&read_big_bytes[..], &payload[..]);
+    drop(read_big);
+
+    // Datei umbenennen
+    let renamed_path = DavPath::new("/Classified/renamed_payload.bin").unwrap();
+    hidden_fs.rename(&big_file_path, &renamed_path).await.expect("Rename file");
+    assert!(hidden_fs.metadata(&big_file_path).await.is_err());
+    assert!(hidden_fs.metadata(&renamed_path).await.is_ok());
+
+    // Datei löschen (Blöcke werden geshreddert und freigegeben)
+    hidden_fs.remove_file(&renamed_path).await.expect("Remove file");
+    assert!(hidden_fs.metadata(&renamed_path).await.is_err());
+
+    // Checkpoint SQLite
+    db.checkpoint().unwrap();
+
+    // 4. CHUNKS-ACCOUNTING-ANGRIFF & INTEGRITÄTSPRÜFUNG
+    // Ein Angreifer besitzt nur das Decoy-Passwort (dek_0).
+    // Er führt eine 100%-ige kryptografische AEAD-Prüfung aller Chunks in der SQLite-Datenbank durch.
+    // ALLE Chunks müssen fehlerfrei unter DEK_0 entschlüsseln!
+    let report = verify_container(&path, Some(&dek_0), true).expect("Verify with DEK_0");
+    assert!(
+        report.is_healthy(),
+        "Container muss für einen Angreifer mit DEK_0 100% gesund und fehlerfrei sein! Fehler: {:?}",
+        report.errors
+    );
+    assert_eq!(
+        report.corrupted_chunks, 0,
+        "Chunks-Accounting: Es darf exakt 0 korrupte Chunks unter DEK_0 geben!"
+    );
+    assert_eq!(
+        report.orphan_nodes, 0,
+        "Es darf keine verwaisten Knoten geben!"
+    );
+
+    // Aufräumen
+    let _ = std::fs::remove_file(&path);
+}
+
+#[tokio::test]
+async fn test_model_a_container_file_size_invariance() {
+    let path = temp_db_path("carrier_size_invariance");
+    let carrier_size_bytes = 10 * 1024 * 1024; // 10 MB
+
+    let pass_decoy = "DecoyPass2026!";
+    let pass_hidden = "HiddenPass2026!";
+
+    let kdf_params = KdfParams {
+        memory_cost: 1024,
+        time_cost: 1,
+        parallelism: 1,
+    };
+
+    let salt_0 = generate_salt();
+    let kek_0 = derive_kek(pass_decoy, &salt_0, &kdf_params).unwrap();
+    let dek_0 = generate_dek();
+
+    let salt_1 = generate_salt();
+    let kek_1 = derive_kek(pass_hidden, &salt_1, &kdf_params).unwrap();
+    let dek_1 = generate_dek();
+
+    let carrier_node_id = 3i64;
+    let (wrapped_0, nonce_0, tag_0) =
+        wrap_slot0_payload(&kek_0, &dek_0, carrier_node_id).unwrap();
+    let (wrapped_1, nonce_1, tag_1) =
+        wrap_slot1_payload(&kek_1, &dek_1, &dek_0, carrier_node_id).unwrap();
+
+    let db = Database::open(&path).expect("Open database");
+
+    db.init_schema_with_carrier(
+        &salt_0,
+        &kdf_params,
+        &wrapped_0,
+        &nonce_0,
+        &tag_0,
+        Some((
+            "virtual_disk.vhdx",
+            carrier_size_bytes,
+            &salt_1,
+            &kdf_params,
+            &wrapped_1,
+            &nonce_1,
+            &tag_1,
+            &dek_0,
+            &dek_1,
+        )),
+    )
+    .expect("Init carrier schema");
+
+    db.checkpoint().unwrap();
+
+    // Initiale Dateigröße messen
+    let initial_file_size = std::fs::metadata(&path).unwrap().len();
+    assert!(initial_file_size >= carrier_size_bytes, "Containergröße muss mindestens 10 MB betragen");
+
+    // Hidden Mount öffnen und 4 MB geheime Daten schreiben
+    let meta = db.read_meta().unwrap();
+    let auth_hidden = meta.authenticate(pass_hidden).expect("Auth hidden");
+
+    let hidden_fs = SanctumFs::with_carrier(
+        db.clone(),
+        auth_hidden.dek().clone(),
+        auth_hidden.carrier_dek(),
+        auth_hidden.carrier_node_id(),
+        auth_hidden.version(),
+        true,
+        1,
+    );
+
+    let test_file = DavPath::new("/large_confidential.pdf").unwrap();
+    let mut handle = hidden_fs
+        .open(&test_file, OpenOptions { create: true, write: true, ..Default::default() })
+        .await
+        .expect("Open file");
+
+    let mut random_data = vec![0u8; 4 * 1024 * 1024]; // 4 MB
+    OsRng.fill_bytes(&mut random_data);
+    handle.write_bytes(Bytes::copy_from_slice(&random_data)).await.expect("Write 4MB");
+    handle.flush().await.expect("Flush 4MB");
+    drop(handle);
+
+    db.checkpoint().unwrap();
+
+    // Dateigröße nach dem Schreiben von 4 MB im Hidden Vault messen
+    let size_after_hidden_writes = std::fs::metadata(&path).unwrap().len();
+
+    // Die Dateigröße auf der Festplatte DARF NICHT WACHSEN!
+    // Alle Chunks wurden in vorallokierte Carrier-Blöcke überschrieben.
+    assert_eq!(
+        initial_file_size, size_after_hidden_writes,
+        "Dateigröße auf der Festplatte darf sich beim Schreiben in den Hidden Vault NICHT verändern! Vorher: {}, Nachher: {}",
+        initial_file_size, size_after_hidden_writes
+    );
+
+    let _ = std::fs::remove_file(&path);
+}