add line separator support

dkim/__init__.py

@@ -365,7 +365,7 @@ def text(s):
     return s.encode('ascii')
 
 
-def fold(header, namelen=0):
+def fold(header, namelen=0, linesep=b'\r\n'):
     """Fold a header line into multiple crlf-separated lines at column 72.
 
     >>> text(fold(b'foo'))
@@ -399,10 +399,10 @@ def fold(header, namelen=0):
         i = header[:maxleng].rfind(b" ")
         if i == -1:
             j = maxleng
-            pre += header[:j] + b"\r\n "
+            pre += header[:j] + linesep + b" "
         else:
             j = i + 1
-            pre += header[:i] + b"\r\n "
+            pre += header[:i] + linesep + b" "
         header = header[j:]
         maxleng = 72
     if len(header) > 2:
@@ -460,8 +460,9 @@ class DomainSigner(object):
   #: (with either \\n or \\r\\n line endings)
   #: @param logger: a logger to which debug info will be written (default None)
   #: @param signature_algorithm: the signing algorithm to use when signing
+  #: @param linesep: use this line seperator for folding the headers
   def __init__(self,message=None,logger=None,signature_algorithm=b'rsa-sha256',
-        minkey=1024):
+        minkey=1024, linesep=b'\r\n'):
     self.set_message(message)
     if logger is None:
         logger = get_default_logger()
@@ -482,6 +483,9 @@ class DomainSigner(object):
     #: Minimum public key size.  Shorter keys raise KeyFormatError. The
     #: default is 1024
     self.minkey = minkey
+    # use this line seperator for output
+    self.linesep = linesep
+
 
   #: Header fields to protect from additions by default.
   #:
@@ -608,7 +612,7 @@ class DomainSigner(object):
 
     header_value = b"; ".join(b"=".join(x) for x in fields)
     if not standardize:
-      header_value = fold(header_value, namelen=len(header_name))
+      header_value = fold(header_value, namelen=len(header_name), linesep=b'\r\n')
     header_value = RE_BTAG.sub(b'\\1',header_value)
     header = (header_name, b' ' + header_value)
     h = HashThrough(self.hasher())
@@ -634,10 +638,10 @@ class DomainSigner(object):
     # relaxed/simple (for broken receivers), and fold now.
     idx = [i for i in range(len(fields)) if fields[i][0] == b'b'][0]
     fields[idx] = (b'b', base64.b64encode(bytes(sig2)))
-    header_value = b"; ".join(b"=".join(x) for x in fields) + b"\r\n"
+    header_value = b"; ".join(b"=".join(x) for x in fields) + self.linesep
 
     if not standardize:
-      header_value = fold(header_value, namelen=len(header_name))
+      header_value = fold(header_value, namelen=len(header_name), linesep=self.linesep)
 
     return header_value
 
@@ -947,7 +951,7 @@ class ARC(DomainSigner):
     results_lists = [raw.replace(srv_id + b';', b'').strip() for (raw, parsed) in auth_headers]
     results_lists = [tags.split(b';') for tags in results_lists]
     results = [tag.strip() for sublist in results_lists for tag in sublist]
-    auth_results = srv_id + b'; ' + b';\r\n  '.join(results)
+    auth_results = srv_id + b'; ' + (b';' + self.linesep + b'  ').join(results)
 
     # extract cv
     parsed_auth_results = AuthenticationResultsHeader.parse('Authentication-Results: ' + auth_results.decode('utf-8'))
@@ -1216,7 +1220,8 @@ class ARC(DomainSigner):
 def sign(message, selector, domain, privkey, identity=None,
          canonicalize=(b'relaxed', b'simple'),
          signature_algorithm=b'rsa-sha256',
-         include_headers=None, length=False, logger=None):
+         include_headers=None, length=False, logger=None,
+         linesep=b'\r\n'):
     # type: (bytes, bytes, bytes, bytes, bytes, tuple, bytes, list, bool, any) -> bytes
     """Sign an RFC822 message and return the DKIM-Signature header line.
     @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings)
@@ -1229,11 +1234,12 @@ def sign(message, selector, domain, privkey, identity=None,
     @param include_headers: a list of strings indicating which headers are to be signed (default all headers not listed as SHOULD NOT sign)
     @param length: true if the l= tag should be included to indicate body length (default False)
     @param logger: a logger to which debug info will be written (default None)
+    @param linesep: use this line seperator for folding the headers
     @return: DKIM-Signature header field terminated by \\r\\n
     @raise DKIMException: when the message, include_headers, or key are badly formed.
     """
 
-    d = DKIM(message,logger=logger,signature_algorithm=signature_algorithm)
+    d = DKIM(message,logger=logger,signature_algorithm=signature_algorithm,linesep=linesep)
     return d.sign(selector, domain, privkey, identity=identity, canonicalize=canonicalize, include_headers=include_headers, length=length)
 
 
@@ -1260,7 +1266,7 @@ dkim_verify = verify
 def arc_sign(message, selector, domain, privkey,
              srv_id, signature_algorithm=b'rsa-sha256',
              include_headers=None, timestamp=None,
-             logger=None, standardize=False):
+             logger=None, standardize=False, linesep=b'\r\n'):
     # type: (bytes, bytes, bytes, bytes, bytes, bytes, list, any, any, bool) -> list
     """Sign an RFC822 message and return the ARC set header lines for the next instance
     @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings)
@@ -1272,11 +1278,12 @@ def arc_sign(message, selector, domain, privkey,
     @param include_headers: a list of strings indicating which headers are to be signed (default all headers not listed as SHOULD NOT sign)
     @param timestamp: the time in integer seconds when the message is sealed (default is int(time.time) based on platform, can be string or int)
     @param logger: a logger to which debug info will be written (default None)
+    @param linesep: use this line seperator for folding the headers
     @return: A list containing the ARC set of header fields for the next instance
     @raise DKIMException: when the message, include_headers, or key are badly formed.
     """
 
-    a = ARC(message,logger=logger,signature_algorithm=b'rsa-sha256')
+    a = ARC(message,logger=logger,signature_algorithm=b'rsa-sha256',linesep=linesep)
     if not include_headers:
         include_headers = a.default_sign_headers()
     return a.sign(selector, domain, privkey, srv_id, include_headers=include_headers,