Merge: #14983: always add a line end after a MIME boundary marker.

Lib/email/generator.py

@@ -299,9 +299,8 @@ class Generator:
             # body-part
             self._fp.write(body_part)
         # close-delimiter transport-padding
-        self.write(self._NL + '--' + boundary + '--')
+        self.write(self._NL + '--' + boundary + '--' + self._NL)
         if msg.epilogue is not None:
-            self.write(self._NL)
             if self._mangle_from_:
                 epilogue = fcre.sub('>From ', msg.epilogue)
             else:

Lib/test/test_email/data/msg_02.txt

@@ -119,6 +119,7 @@ hello
 
 
 --__--__----
+
 --192.168.1.2.889.32614.987812255.500.21814
 Content-type: text/plain; charset=us-ascii
 Content-description: Digest Footer

Lib/test/test_email/test_email.py

@@ -1745,7 +1745,8 @@ From: bperson@dom.ain
 
 --BOUNDARY
 
---BOUNDARY--''')
+--BOUNDARY--
+''')
 
     def test_no_parts_in_a_multipart_with_empty_epilogue(self):
         outer = MIMEBase('multipart', 'mixed')
@@ -1790,7 +1791,8 @@ MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
 
 hello world
---BOUNDARY--''')
+--BOUNDARY--
+''')
 
     def test_seq_parts_in_a_multipart_with_empty_preamble(self):
         eq = self.ndiffAssertEqual
@@ -1816,7 +1818,8 @@ MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
 
 hello world
---BOUNDARY--''')
+--BOUNDARY--
+''')
 
 
     def test_seq_parts_in_a_multipart_with_none_preamble(self):
@@ -1842,7 +1845,8 @@ MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
 
 hello world
---BOUNDARY--''')
+--BOUNDARY--
+''')
 
 
     def test_seq_parts_in_a_multipart_with_none_epilogue(self):
@@ -1868,7 +1872,8 @@ MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
 
 hello world
---BOUNDARY--''')
+--BOUNDARY--
+''')
 
 
     def test_seq_parts_in_a_multipart_with_empty_epilogue(self):

Misc/NEWS

@@ -27,6 +27,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #14983: email.generator now always adds a line end after each MIME
+  boundary marker, instead of doing so only when there is an epilogue.  This
+  fixes an RFC compliance bug and solves an issue with signed MIME parts.
+
 - Issue #20540: Fix a performance regression (vs. Python 3.2) when layering
   a multiprocessing Connection over a TCP socket.  For small payloads, Nagle's
   algorithm would introduce idle delays before the entire transmission of a