Feature to force binary canonicalization (#55)

* Added partner setting to force canonicalize binary.

* Formatted with black

pyas2lib/as2.py

@@ -177,6 +177,8 @@ class Partner:
     :param mdn_confirm_text: The text to be used in the MDN for successfully
         processed messages received from this partner.
 
+    :param canonicalize_as_binary: force binary canonicalization for this partner
+
     """
 
     as2_name: str
@@ -194,6 +196,7 @@ class Partner:
     mdn_digest_alg: str = None
     mdn_confirm_text: str = MDN_CONFIRM_TEXT
     ignore_self_signed: bool = True
+    canonicalize_as_binary: bool = False
 
     def __post_init__(self):
         """Run the post initialisation checks for this class."""
@@ -638,7 +641,10 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, find_message_cb=None)
 
                 # Verify the message, first using raw message and if it fails
                 # then convert to canonical form and try again
-                mic_content = canonicalize(self.payload)
+                mic_content = canonicalize(
+                    self.payload,
+                    canonicalize_as_binary=self.sender.canonicalize_as_binary,
+                )
                 verify_cert = self.sender.load_verify_cert()
                 self.digest_alg = verify_message(mic_content, signature, verify_cert)
 

pyas2lib/utils.py

@@ -75,15 +75,19 @@ def mime_to_bytes(msg: message.Message, email_policy: policy.Policy = policy.HTT
     return fp.getvalue()
 
 
-def canonicalize(email_message: message.Message):
+def canonicalize(email_message: message.Message, canonicalize_as_binary: bool = False):
     """
     Function to convert an email Message to standard format string/
 
     :param email_message: email.message.Message to be converted to standard string
+    :param canonicalize_as_binary: force binary canonicalization
     :return: the standard representation of the email message in bytes
     """
 
-    if email_message.get("Content-Transfer-Encoding") == "binary":
+    if (
+        email_message.get("Content-Transfer-Encoding") == "binary"
+        or canonicalize_as_binary
+    ):
         message_header = ""
         message_body = email_message.get_payload(decode=True)
         for k, v in email_message.items():