Add --reset and post-import --set-password; fix algorithm nibble parsing

Add two admin operations on the OATH protocol layer: --reset (RESET
0x04/0xDEAD) and --set-password, which sets an access password after a
successful import only if the applet has none. Fix _parse_select to mask
the SELECT ALGORITHM tag to its low nibble (the applet reports the full
type|algo byte, e.g. 0x21), which previously broke validate on a locked
applet. Add a clean top-level OathError handler.

README.md

@@ -45,8 +45,19 @@ python apex_otp_import.py --input ... --skip-existing
 
 # Target a specific reader, supply a password, and profile memory
 python apex_otp_import.py --input ... --reader VivoKey --password '...' --profile-memory
+
+# Import, then set an access password (only if the applet has none yet)
+python apex_otp_import.py --input ... --set-password 'yourpassword'
+
+# Reset: wipe all credentials and any password (standalone; no input needed)
+python apex_otp_import.py --reset
 ```
 
+Authenticating to a password-protected applet uses the standard YKOATH scheme
+(PBKDF2-HMAC-SHA1 of the password with the device id as salt, then mutual
+challenge-response). `--set-password` only sets a password on an applet that has
+none; it does not change or remove an existing one. `--reset` clears everything.
+
 The input is validated before any reader is touched. Duplicate credential names,
 invalid Base32, over-long names/keys, and unsupported algorithms halt the run
 with a report so they can be fixed in the source data.

apex_otp_import.py

@@ -38,6 +38,7 @@ TAG_ALGORITHM = 0x7B
 
 HOTP_TYPE = 0x10
 TOTP_TYPE = 0x20
+HMAC_MASK = 0x0F   # low nibble of a type|algo byte selects the HMAC algorithm
 HMAC_SHA1 = 0x01
 HMAC_SHA256 = 0x02
 HMAC_SHA512 = 0x03  # rejected by the applet; used only to flag bad input
@@ -253,6 +254,17 @@ def build_validate_data(response: bytes, client_challenge: bytes) -> bytes:
     return tlv(TAG_RESPONSE, response) + tlv(TAG_CHALLENGE, client_challenge)
 
 
+def build_set_code_data(key: bytes, challenge: bytes, algo: int = HMAC_SHA1) -> bytes:
+    """SET CODE payload: KEY(0x73, [type|algo, 16-byte key]) + CHALLENGE(0x74) +
+    RESPONSE(0x75, HMAC(key, challenge)) so the applet can confirm the host
+    derives the same key."""
+    return (
+        tlv(TAG_KEY, bytes([TOTP_TYPE | algo]) + key)
+        + tlv(TAG_CHALLENGE, challenge)
+        + tlv(TAG_RESPONSE, compute_response(key, challenge, algo))
+    )
+
+
 INS_SEND_REMAINING = 0xA5
 
 
@@ -320,6 +332,8 @@ OATH_AIDS = [
 
 INS_SELECT = 0xA4
 INS_PUT = 0x01
+INS_SET_CODE = 0x03
+INS_RESET = 0x04
 INS_LIST = 0xA1
 INS_VALIDATE = 0xA3
 
@@ -378,7 +392,8 @@ class OathSession:
             elif tag == TAG_CHALLENGE:
                 self.challenge = val
             elif tag == TAG_ALGORITHM:
-                self.algorithm = val[0] if val else HMAC_SHA1
+                # applet reports the full type|algo byte; keep only the algo nibble
+                self.algorithm = (val[0] & HMAC_MASK) if val else HMAC_SHA1
 
     @property
     def locked(self) -> bool:
@@ -418,6 +433,25 @@ class OathSession:
             raise OathError(sw)
         return
 
+    def set_password(self, password: str):
+        """SET CODE: install an access password (SHA1) on the applet. Requires
+        the applet be unlocked, or already authenticated this session."""
+        key = derive_key(password, self.device_id)
+        challenge = self.rng(8)
+        data, sw = self.ch.send(
+            0x00, INS_SET_CODE, 0x00, 0x00,
+            data=build_set_code_data(key, challenge, HMAC_SHA1))
+        if sw != 0x9000:
+            raise OathError(sw, "SET CODE failed")
+        return
+
+    def reset(self):
+        """RESET: wipe all credentials and any password (P1P2 = 0xDEAD)."""
+        data, sw = self.ch.send(0x00, INS_RESET, 0xDE, 0xAD)
+        if sw != 0x9000:
+            raise OathError(sw, "RESET failed")
+        return
+
 
 # ---------------------------------------------------------------------------
 # Optional javacard-memory applet (for capacity checks / profiling)
@@ -584,6 +618,11 @@ def parse_args(argv=None):
     p.add_argument("--memlog", default=DEFAULT_MEMLOG,
                    help=f"profiling CSV path (default: {DEFAULT_MEMLOG})")
     p.add_argument("--password", help="applet password (else prompted if locked)")
+    p.add_argument("--reset", action="store_true",
+                   help="wipe all credentials and any password, then exit")
+    p.add_argument("--set-password", metavar="PASS",
+                   help="after importing, set this applet password "
+                        "(only if the applet has none)")
     return p.parse_args(argv)
 
 
@@ -596,6 +635,17 @@ def _reauth(oath, pw):
 def main(argv=None):
     args = parse_args(argv)
 
+    # --reset is a standalone admin action; it needs no input spreadsheet.
+    if args.reset:
+        reader, connection = pick_reader(args.reader)
+        if connection is None:
+            return 1
+        oath = OathSession(CardChannel(connection))
+        oath.select()
+        oath.reset()
+        print(f"Applet reset on '{reader}' (all credentials and any password wiped).")
+        return 0
+
     # 1. Load + validate BEFORE touching any reader.
     creds = load_credentials(args.input)
     problems = validate_input(creds)
@@ -633,6 +683,7 @@ def main(argv=None):
     # 5. OATH session.
     oath = OathSession(channel)
     oath.select()
+    applet_was_locked = oath.locked
     print(f"OATH applet on '{reader}': v{'.'.join(map(str, oath.version))}, "
           f"{'LOCKED' if oath.locked else 'unlocked'}.")
     pw = None
@@ -699,6 +750,15 @@ def main(argv=None):
         if memlog_fh:
             memlog_fh.close()
 
+    # Post-import: optionally set an access password on a not-yet-protected applet.
+    if args.set_password and failed == 0:
+        if applet_was_locked:
+            print("Applet already password-protected; --set-password skipped.")
+        else:
+            oath.select()  # ensure OATH is the active applet (profiling deselects it)
+            oath.set_password(args.set_password)
+            print("Applet password set.")
+
     print(f"\nDone: {ok} written, {skipped} skipped, {failed} failed.")
     if args.profile_memory:
         print(f"Memory profile appended to {args.memlog}.")
@@ -706,4 +766,10 @@ def main(argv=None):
 
 
 if __name__ == "__main__":
+    try:
         sys.exit(main())
+    except OathError as e:
+        print(f"OATH error: {e}")
+        sys.exit(1)
+    except KeyboardInterrupt:
+        sys.exit(130)

docs/design.md

@@ -201,11 +201,25 @@ exceptions (no card, reader gone) surface as clear, actionable messages.
   oversize key, SHA512).
 - `61xx` reassembly via a fake channel that chunks a long LIST response.
 
+## Password / reset admin (added after initial spec)
+
+The importer also exposes two admin operations on the same protocol layer:
+
+- `--set-password PASS`: after a fully successful import, set an access password
+  on the applet **only if it has none** (SET CODE with a SHA1 access key derived
+  as above). Runs post-import for efficiency (single session). Does not change or
+  remove an existing password.
+- `--reset`: standalone; sends RESET (P1P2 = 0xDEAD) to wipe all credentials and
+  any password, then exits.
+
+Note: the applet reports the full `type|algo` byte (e.g. `0x21`) in the SELECT
+ALGORITHM tag; the low nibble is masked off to select the HMAC algorithm.
+
 ## Out of scope (YAGNI)
 
-Setting/changing/removing the applet password (authenticate-only); HOTP import;
-touch-required; RENAME/DELETE; CSV/text input; on-device code calculation
-(beyond optional post-import verification, not included).
+Changing or removing an existing password; HOTP import; touch-required;
+RENAME/DELETE of individual credentials; CSV/text input; on-device code
+calculation (beyond ad-hoc post-import verification, not part of the tool).
 
 ## Files
 

test_oath.py

@@ -7,7 +7,7 @@ from openpyxl import Workbook
 
 from apex_otp_import import (
     tlv, parse_tlvs, decode_secret, pad_key, format_cred_id,
-    build_put_data, build_validate_data,
+    build_put_data, build_validate_data, build_set_code_data,
     derive_key, compute_response,
     Credential, validate_input, load_credentials,
     CardChannel, OathSession, OathError, parse_memory,
@@ -119,6 +119,18 @@ class TestValidateData(unittest.TestCase):
         self.assertEqual(data, bytes([0x75, 0x14]) + resp + bytes([0x74, 0x08]) + chal)
 
 
+class TestSetCodeData(unittest.TestCase):
+    def test_byte_exact_set_code_payload(self):
+        key = b"\x11" * 16
+        chal = b"\x22" * 8
+        data = build_set_code_data(key, chal)
+        resp = compute_response(key, chal, HMAC_SHA1)
+        expected = (tlv(0x73, bytes([0x21]) + key)     # KEY: TOTP|SHA1 + 16-byte key
+                    + tlv(0x74, chal)                   # CHALLENGE
+                    + tlv(0x75, resp))                  # RESPONSE = HMAC(key, challenge)
+        self.assertEqual(data, expected)
+
+
 class TestPasswordAuth(unittest.TestCase):
     SALT = bytes([0x19, 0x83, 0x57, 0x1E, 0xC3, 0xE5, 0xAB, 0xD7])
 
@@ -222,8 +234,9 @@ def select_unlocked():
 
 
 def select_locked(challenge):
+    # real applet reports the full type|algo byte (0x21 = TOTP|SHA1), not 0x01
     return (VERSION_TLV + tlv(0x71, DEV_ID)
-            + tlv(0x74, challenge) + tlv(0x7B, bytes([HMAC_SHA1])))
+            + tlv(0x74, challenge) + tlv(0x7B, bytes([TOTP_TYPE | HMAC_SHA1])))
 
 
 class TestOathSessionSelect(unittest.TestCase):
@@ -314,5 +327,24 @@ class TestOathSessionValidate(unittest.TestCase):
             s.validate("wrong")
 
 
+class TestOathSessionAdmin(unittest.TestCase):
+    def test_set_password_sends_set_code(self):
+        from apex_otp_import import derive_key
+        client = b"\x22" * 8
+        conn = FakeConn([(select_unlocked(), 0x90, 0x00), (b"", 0x90, 0x00)])
+        s = OathSession(CardChannel(conn), rng=lambda n: client)
+        s.select()
+        s.set_password("test1234")
+        self.assertEqual(conn.sent[1][1], 0x03)  # INS SET CODE
+        key = derive_key("test1234", DEV_ID)
+        self.assertEqual(bytes(conn.sent[1][5:]), build_set_code_data(key, client))
+
+    def test_reset_sends_reset_with_dead(self):
+        conn = FakeConn([(select_unlocked(), 0x90, 0x00), (b"", 0x90, 0x00)])
+        s = OathSession(CardChannel(conn)); s.select()
+        s.reset()
+        self.assertEqual(conn.sent[1][:4], [0x00, 0x04, 0xDE, 0xAD])
+
+
 if __name__ == "__main__":
     unittest.main()