Raise exception for invalid signature enc_str

Author: brunorijsman

common/exceptions.py

@@ -321,12 +321,25 @@ class InvalidEncodedFragment(DSKEException):
 
     def __init__(self, encoded_fragment: str):
         super().__init__(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            status_code=status.HTTP_400_BAD_REQUEST
             message="Invalid encoded fragment.",
             details={"encoded_fragment": encoded_fragment},
         )
 
 
+class InvalidEncodedSignature(DSKEException):
+    """
+    Exception raised when trying to parse an encoded signature string that is invalid.
+    """
+
+    def __init__(self, encoded_signature: str):
+        super().__init__(
+            status_code=status.HTTP_400_BAD_REQUEST
+            message="Invalid encoded fragment.",
+            details={"encoded_signature": encoded_signature},
+        )
+
+
 class EncryptorNotRegisteredForClientError(DSKEException):
     """
     Exception raised when an encryptor is not registered for a client.

common/signature.py

@@ -3,6 +3,7 @@
 """
 
 from typing import Optional
+from .exceptions import InvalidEncodedSignatureError
 from .utils import bytes_to_str, str_to_bytes
 
 HEADER_NAME = "DSKE-Signature"
@@ -51,7 +52,7 @@ def from_enc_str(cls, enc_str: str) -> "Signature":
         """
         split_str = enc_str.split(_ENCODING_SEPARATOR)
         if len(split_str) != 2:
-            assert False  # TODO: Raise an exception instead
+            raise InvalidEncodedSignatureError(enc_str)
         allocation_enc_str = split_str[0]
         signature_data_str = split_str[1]
         signature_data = str_to_bytes(signature_data_str)