Test PBKDF2 iteration fallback

src/seedpass/core/manager.py

@@ -512,17 +512,36 @@ class PasswordManager:
                 )
                 print("Deriving key...")
                 salt_fp = fingerprint_dir.name
-                if mode == "argon2":
-                    seed_key = derive_key_from_password_argon2(password, salt_fp)
-                else:
-                    seed_key = derive_key_from_password(
-                        password, salt_fp, iterations=iterations
-                    )
-                seed_mgr = EncryptionManager(seed_key, fingerprint_dir)
-                print("Decrypting seed...")
-                try:
-                    self.parent_seed = seed_mgr.decrypt_parent_seed()
-                except Exception:
+
+                iter_candidates: list[int] = [iterations]
+                if mode != "argon2":
+                    iter_candidates.extend([50_000, 100_000])
+
+                seed_mgr: EncryptionManager | None = None
+                for iter_try in dict.fromkeys(iter_candidates):
+                    try:
+                        if mode == "argon2":
+                            seed_key = derive_key_from_password_argon2(
+                                password, salt_fp
+                            )
+                        else:
+                            seed_key = derive_key_from_password(
+                                password, salt_fp, iterations=iter_try
+                            )
+                        seed_mgr = EncryptionManager(seed_key, fingerprint_dir)
+                        print("Decrypting seed...")
+                        self.parent_seed = seed_mgr.decrypt_parent_seed()
+                        if (
+                            mode != "argon2"
+                            and iter_try != iterations
+                            and getattr(self, "config_manager", None)
+                        ):
+                            self.config_manager.set_kdf_iterations(iter_try)
+                        break
+                    except InvalidToken:
+                        seed_mgr = None
+
+                if seed_mgr is None:
                     msg = (
                         "Invalid password for selected seed profile. Please try again."
                     )

src/tests/test_kdf_iteration_fallback.py

@@ -0,0 +1,51 @@
+import bcrypt
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+from helpers import TEST_SEED, TEST_PASSWORD
+from utils.fingerprint import generate_fingerprint
+from utils.key_derivation import derive_index_key, derive_key_from_password
+from seedpass.core.encryption import EncryptionManager
+from seedpass.core.vault import Vault
+from seedpass.core.config_manager import ConfigManager
+from seedpass.core.manager import PasswordManager, EncryptionMode
+
+
+def test_kdf_iteration_fallback(monkeypatch):
+    with TemporaryDirectory() as td:
+        tmp = Path(td)
+        fp_name = generate_fingerprint(TEST_SEED)
+        fp_dir = tmp / fp_name
+        fp_dir.mkdir()
+
+        seed_key = derive_key_from_password(TEST_PASSWORD, fp_name, iterations=100_000)
+        EncryptionManager(seed_key, fp_dir).encrypt_parent_seed(TEST_SEED)
+
+        index_key = derive_index_key(TEST_SEED)
+        enc_mgr = EncryptionManager(index_key, fp_dir)
+        vault = Vault(enc_mgr, fp_dir)
+        cfg_mgr = ConfigManager(vault, fp_dir)
+        cfg = cfg_mgr.load_config(require_pin=False)
+        cfg["password_hash"] = bcrypt.hashpw(
+            TEST_PASSWORD.encode(), bcrypt.gensalt()
+        ).decode()
+        cfg["kdf_iterations"] = 100_000
+        cfg_mgr.save_config(cfg)
+
+        cfg["kdf_iterations"] = 50_000
+        cfg_mgr.save_config(cfg)
+
+        pm = PasswordManager.__new__(PasswordManager)
+        pm.encryption_mode = EncryptionMode.SEED_ONLY
+        pm.config_manager = cfg_mgr
+        pm.fingerprint_dir = fp_dir
+        pm.current_fingerprint = fp_name
+        pm.verify_password = lambda pw: True
+
+        monkeypatch.setattr(
+            "seedpass.core.manager.prompt_existing_password", lambda *_: TEST_PASSWORD
+        )
+
+        assert pm.setup_encryption_manager(fp_dir, exit_on_fail=False)
+        assert pm.parent_seed == TEST_SEED
+        assert cfg_mgr.get_kdf_iterations() == 100_000