Add CanonicalizationPolicy, which encapsulates the combined hybrid simple/relaxed schemes.

dkim/__init__.py

@@ -25,7 +25,10 @@ import logging
 import re
 import time
 
-from dkim.canonicalization import algorithms
+from dkim.canonicalization import (
+    algorithms,
+    CanonicalizationPolicy,
+    )
 from dkim.crypto import (
     DigestTooLargeError,
     HASH_ALGORITHMS,
@@ -334,8 +337,9 @@ def verify(message, logger=None, dnsfunc=get_txt):
     except KeyError as e:
         logger.error("unknown canonicalization algorithm: %s" % e.message)
         return False
-    headers = header_algorithm.canonicalize_headers(headers)
-    body = body_algorithm.canonicalize_body(body)
+    canon_policy = CanonicalizationPolicy(header_algorithm, body_algorithm)
+    headers = canon_policy.canonicalize_headers(headers)
+    body = canon_policy.canonicalize_body(body)
 
     try:
         hasher = HASH_ALGORITHMS[sig[b'a']]

dkim/canonicalization.py

@@ -23,6 +23,7 @@ import re
 
 __all__ = [
     'algorithms',
+    'CanonicalizationPolicy',
     ]
 
 
@@ -83,4 +84,17 @@ class Relaxed:
             compress_whitespace(strip_trailing_whitespace(body)))
 
 
+class CanonicalizationPolicy:
+
+    def __init__(self, header_algorithm, body_algorithm):
+        self.header_algorithm = header_algorithm
+        self.body_algorithm = body_algorithm
+
+    def canonicalize_headers(self, headers):
+        return self.header_algorithm.canonicalize_headers(headers)
+
+    def canonicalize_body(self, body):
+        return self.body_algorithm.canonicalize_body(body)
+
+
 algorithms = dict((c.name, c) for c in (Simple, Relaxed))