Raise exception for incorrectly encoded signing key

Author: brunorijsman

common/exceptions.py

@@ -335,11 +335,24 @@ class InvalidEncodedSignatureError(DSKEException):
     def __init__(self, encoded_signature: str):
         super().__init__(
             status_code=status.HTTP_400_BAD_REQUEST,
-            message="Invalid encoded fragment.",
+            message="Invalid encoded signature.",
             details={"encoded_signature": encoded_signature},
         )
 
 
+class InvalidEncodedSigningKeyError(DSKEException):
+    """
+    Exception raised when trying to parse an encoded signing key string that is invalid.
+    """
+
+    def __init__(self, encoded_signing_key: str):
+        super().__init__(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            message="Invalid encoded signing key.",
+            details={"encoded_signing_key": encoded_signing_key},
+        )
+
+
 class EncryptorNotRegisteredForClientError(DSKEException):
     """
     Exception raised when an encryptor is not registered for a client.

common/signing_key.py

@@ -5,6 +5,7 @@
 import hashlib
 import hmac
 from .allocation import Allocation
+from .exceptions import InvalidEncodedSigningKeyError
 from .pool import Pool
 from .signature import Signature
 from .utils import bytes_to_str, str_to_bytes
@@ -98,7 +99,7 @@ def from_enc_str(cls, enc_str: str) -> "SigningKey":
         """
         split_str = enc_str.split(_ENCODING_SEPARATOR)
         if len(split_str) != 2:
-            assert False  # TODO: Raise an exception instead
+            raise InvalidEncodedSigningKeyError(enc_str)
         allocation_enc_str = split_str[0]
         key_data_str = split_str[1]
         key_data = str_to_bytes(key_data_str)