Merge PR #454.

ykman/cli/otp.py

@@ -37,7 +37,12 @@
  UpdateConfiguration,
 )
 from yubikit.core import TRANSPORT, CommandError
-from yubikit.core.otp import modhex_encode, modhex_decode, OtpConnection
+from yubikit.core.otp import (
+ MODHEX_ALPHABET,
+ modhex_encode,
+ modhex_decode,
+ OtpConnection,
+)
 
 from .util import (
  ykman_group,
@@ -381,8 +386,8 @@ def yubiotp(
 
  try:
  public_id = modhex_decode(public_id)
- except KeyError:
- ctx.fail("Invalid public ID, must be modhex.")
+ except ValueError:
+ ctx.fail(f"Invalid public ID, must be modhex ({MODHEX_ALPHABET}).")
 
  if not private_id:
  if generate_private_id:

yubikit/core/otp.py

@@ -37,6 +37,9 @@
 logger = logging.getLogger(__name__)
 
 
+MODHEX_ALPHABET = "cbdefghijklnrtuv"
+
+
 class CommandRejectedError(CommandError):
  """The issues command was rejected by the YubiKey"""
 
@@ -70,18 +73,15 @@ def check_crc(data: bytes) -> bool:
  return calculate_crc(data) == CRC_OK_RESIDUAL
 
 
-_MODHEX = "cbdefghijklnrtuv"
-
-
 def modhex_encode(data: bytes) -> str:
  """Encode a bytes-like object using Modhex (modified hexadecimal) encoding."""
- return "".join(_MODHEX[b >> 4] + _MODHEX[b & 0xF] for b in data)
+ return "".join(MODHEX_ALPHABET[b >> 4] + MODHEX_ALPHABET[b & 0xF] for b in data)
 
 
 def modhex_decode(string: str) -> bytes:
  """Decode the Modhex (modified hexadecimal) string."""
  return bytes(
- _MODHEX.index(string[i]) << 4 | _MODHEX.index(string[i + 1])
+ MODHEX_ALPHABET.index(string[i]) << 4 | MODHEX_ALPHABET.index(string[i + 1])
  for i in range(0, len(string), 2)
  )