- Fix header folding to use \n only to align with milter protocol

requirements

CHANGES

@@ -1,6 +1,8 @@
 0.9.4 UNRELEASED
  - Create PID directory if it is missing
  - Fix crash when verifying if domain for signing was not set
+ - Fix header folding to use \n only to align with milter protocol
+   requirements
 
 0.9.3 2018-03-02
  - Fixup csl dataset processing for single item lists

dkimpy_milter/__init__.py

@@ -40,6 +40,7 @@ from dkimpy_milter.util import setExceptHook
 from dkimpy_milter.util import write_pid
 from dkimpy_milter.util import read_keyfile
 from dkimpy_milter.util import own_socketfile
+from dkimpy_milter.util import fold
 
 __version__ = "0.9.4"
 FWS = re.compile(r'\r?\n[ \t]+')
@@ -176,7 +177,7 @@ class dkimMilter(Milter.Base):
     if self.arresults:
         h = authres.AuthenticationResultsHeader(authserv_id = self.receiver, 
             results=self.arresults)
-        h = dkim.fold(str(h))
+        h = fold(str(h))
         if milterconfig.get('Syslog'):
             syslog.syslog(str(h))
         name,val = str(h).split(': ',1)

dkimpy_milter/util.py

@@ -16,6 +16,39 @@
 # with this program; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
+def fold(header):
+    """Fold a header line into multiple crlf-separated lines at column 72.
+    Borrowed from dkimpy and updated to only add \n instead of \r\n because
+    that's what the milter protocol wants.
+
+    >>> text(fold(b'foo'))
+    'foo'
+    >>> text(fold(b'foo  '+b'foo'*24).splitlines()[0])
+    'foo  '
+    >>> text(fold(b'foo'*25).splitlines()[-1])
+    ' foo'
+    >>> len(fold(b'foo'*25).splitlines()[0])
+    72
+    """
+    i = header.rfind(b"\r\n ")
+    if i == -1:
+        pre = b""
+    else:
+        i += 3
+        pre = header[:i]
+        header = header[i:]
+    maxleng = 72
+    while len(header) > maxleng:
+        i = header[:maxleng].rfind(b" ")
+        if i == -1:
+            j = maxleng
+        else:
+            j = i + 1
+        pre += header[:j] + b"\n   "
+        header = header[j:]
+        namelen = 0
+    return pre + header
+
 def user_group(userid):
     """Return user and group from UserID"""
     import grp