- Correctly fold lines at or near the maximum line length (fix folding

zero length lines and adding a blank line and adding an exra cr/lf for
      lines near max length (LP: #1717576)

ChangeLog

@@ -1,9 +1,15 @@
+2018-06-16 Version 0.8.1
+    - Correctly fold lines at or near the maximum line length (fix folding
+      zero length lines and adding a blank line and adding an exra cr/lf for
+      lines near max length (LP: #1717576)
+      - Thanks to Christian Jørgensen and John Levine for reporting the issue
+
 2018-05-18 Version 0.8.0
     - Change from distutils to setuptools with entry points because it's the
       future
     - Use install_requires and extras_requires to document external
       dependencies for dkimpy (LP: #1227526)
-    - Fix typo in dknewky(1) for k= tag (Thanks to Andreas Schulze for
+    - Fix typo in dknewkey(1) for k= tag (Thanks to Andreas Schulze for
       reporting)
     - Detect incorrect version in DKIM public key record (LP: #1763815)
     - Detect unknown algorithm in k= tag and raise an appropriate error, vice

dkim/__init__.py

@@ -352,7 +352,18 @@ def fold(header, namelen=0):
     ' foo'
     >>> len(fold(b'foo'*25).splitlines()[0])
     72
+    >>> text(fold(b'x'))
+    'x'
+    >>> text(fold(b'xyz'*24))
+    'xyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyzxyz'
     """
+    # 72 is the max line length we actually want, but the header field name
+    # has to fit in the first line too (See Debian Bug #863690).
+    maxleng = 72 - namelen
+    if len(header) <= maxleng:
+        return header
+    if len(header) - header.rfind(b"\r\n") == 2 and len(header) <= maxleng +2:
+        return header
     i = header.rfind(b"\r\n ")
     if i == -1:
         pre = b""
@@ -360,9 +371,6 @@ def fold(header, namelen=0):
         i += 3
         pre = header[:i]
         header = header[i:]
-    # 72 is the max line length we actually want, but the header field name
-    # has to fit in the first line too (See Debian Bug #863690).
-    maxleng = 72 - namelen
     while len(header) > maxleng:
         i = header[:maxleng].rfind(b" ")
         if i == -1:
@@ -372,6 +380,12 @@ def fold(header, namelen=0):
         pre += header[:j] + b"\r\n "
         header = header[j:]
         namelen = 0
+    if len(header) > 2:
+        return pre + header
+    else:
+        if pre[0] == b' ':
+            return pre[:-1]
+        else:
             return pre + header
 
 def load_pk_from_dns(name, dnsfunc=get_txt):

setup.py

@@ -24,7 +24,7 @@
 from setuptools import setup
 import os
 
-version = "0.8.0"
+version = "0.8.1"
 
 kw = {}  # Work-around for lack of 'or' requires in setuptools.
 try: