fix for missing method in Python 3.6

Author: Andrea Bonomi

securid/jsontoken.py

@@ -3,9 +3,8 @@
 import os
 import os.path
 import json
-from datetime import date
 from typing import Any, Dict, Optional, Union
-from .utils import Bytes
+from .utils import Bytes, fromisoformat
 from .token import SERIAL_LENGTH, Token, AbstractTokenFile
 from .exceptions import ParseException, InvalidSeed, InvalidSerial
 
@@ -81,7 +80,7 @@ def json_decode_token(cls, data: Union[Bytes, Dict[str, Any]]) -> Token:
             token = Token(
                 digits=dct['digits'],
                 interval=dct['period'],
-                exp_date=date.fromisoformat(dct['exp_date'])
+                exp_date=fromisoformat(dct['exp_date'])
                 if dct.get('exp_date')
                 else None,
                 seed=bytes(dct['secret']),

securid/sdtid.py

@@ -14,6 +14,7 @@
     aes_ecb_encrypt,
     xor_block,
     cbc_hash,
+    fromisoformat,
 )
 from .exceptions import ParseException, InvalidSignature
 
@@ -251,7 +252,7 @@ def get(self, name: str, default: Any = None, kind: Optional[str] = None) -> Any
         elif kind == 'int':
             value = int(value)
         elif kind == 'date':
-            value = date.fromisoformat(value.replace('/', '-'))
+            value = fromisoformat(value.replace('/', '-'))
         return value
 
 

securid/token.py

@@ -13,6 +13,7 @@
     random,
     Bytearray,
     aes_ecb_encrypt,
+    fromisoformat,
 )
 
 __all__ = ['Token', 'AbstractTokenFile', 'SERIAL_LENGTH']
@@ -64,7 +65,7 @@ def __init__(
         if isinstance(seed, str):
             seed = bytes(seed, 'ascii')
         if isinstance(exp_date, str):
-            exp_date = date.fromisoformat(exp_date)
+            exp_date = fromisoformat(exp_date)
         self.seed = seed
         self.interval = interval
         self.digits = digits

securid/utils.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python
 
+from datetime import datetime, date
 from typing import Union, Optional
 from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
 
@@ -20,6 +21,7 @@
     'aes_ecb_decrypt',
     'xor_block',
     'cbc_hash',
+    'fromisoformat',
 ]
 
 AES_BLOCK_SIZE = 16
@@ -78,3 +80,10 @@ def cbc_hash(key: Bytes, iv: Bytes, data: Bytes) -> bytes:
         result = aes_ecb_encrypt(key, xor_block(result, data))
         data = data[AES_BLOCK_SIZE:]
     return bytes(result)
+
+
+def fromisoformat(dt: str) -> date:
+    """
+    Convert a YYYY-MM-DD string into a date object
+    """
+    return datetime.strptime(dt, '%Y-%m-%d').date()