Fixed #18967 -- Don't base64-encode message/rfc822 attachments.

Thanks Michael Farrell for the report and his work on the fix.

django/core/mail/message.py

@@ -4,11 +4,13 @@
 import os
 import random
 import time
-from email import charset as Charset, encoders as Encoders
+from email import charset as Charset, encoders as Encoders, message_from_string
 from email.generator import Generator
+from email.message import Message
 from email.mime.text import MIMEText
 from email.mime.multipart import MIMEMultipart
 from email.mime.base import MIMEBase
+from email.mime.message import MIMEMessage
 from email.header import Header
 from email.utils import formatdate, getaddresses, formataddr, parseaddr
 
@@ -118,6 +120,27 @@ def sanitize_address(addr, encoding):
     return formataddr((nm, addr))
 
 
+class SafeMIMEMessage(MIMEMessage):
+
+    def __setitem__(self, name, val):
+        # message/rfc822 attachments must be ASCII
+        name, val = forbid_multi_line_headers(name, val, 'ascii')
+        MIMEMessage.__setitem__(self, name, val)
+
+    def as_string(self, unixfrom=False):
+        """Return the entire formatted message as a string.
+        Optional `unixfrom' when True, means include the Unix From_ envelope
+        header.
+
+        This overrides the default as_string() implementation to not mangle
+        lines that begin with 'From '. See bug #13433 for details.
+        """
+        fp = six.StringIO()
+        g = Generator(fp, mangle_from_=False)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
+
+
 class SafeMIMEText(MIMEText):
 
     def __init__(self, text, subtype, charset):
@@ -137,7 +160,7 @@ def as_string(self, unixfrom=False):
         lines that begin with 'From '. See bug #13433 for details.
         """
         fp = six.StringIO()
-        g = Generator(fp, mangle_from_ = False)
+        g = Generator(fp, mangle_from_=False)
         g.flatten(self, unixfrom=unixfrom)
         return fp.getvalue()
 
@@ -161,7 +184,7 @@ def as_string(self, unixfrom=False):
         lines that begin with 'From '. See bug #13433 for details.
         """
         fp = six.StringIO()
-        g = Generator(fp, mangle_from_ = False)
+        g = Generator(fp, mangle_from_=False)
         g.flatten(self, unixfrom=unixfrom)
         return fp.getvalue()
 
@@ -292,11 +315,26 @@ def _create_attachments(self, msg):
     def _create_mime_attachment(self, content, mimetype):
         """
         Converts the content, mimetype pair into a MIME attachment object.
+
+        If the mimetype is message/rfc822, content may be an
+        email.Message or EmailMessage object, as well as a str.
         """
         basetype, subtype = mimetype.split('/', 1)
         if basetype == 'text':
             encoding = self.encoding or settings.DEFAULT_CHARSET
             attachment = SafeMIMEText(content, subtype, encoding)
+        elif basetype == 'message' and subtype == 'rfc822':
+            # Bug #18967: per RFC2046 s5.2.1, message/rfc822 attachments
+            # must not be base64 encoded.
+            if isinstance(content, EmailMessage):
+                # convert content into an email.Message first
+                content = content.message()
+            elif not isinstance(content, Message):
+                # For compatibility with existing code, parse the message
+                # into a email.Message object if it is not one already.
+                content = message_from_string(content)
+
+            attachment = SafeMIMEMessage(content, subtype)
         else:
             # Encode non-text attachments with base64.
             attachment = MIMEBase(basetype, subtype)

docs/topics/email.txt

@@ -319,15 +319,25 @@ The class has the following methods:
 
        message.attach('design.png', img_data, 'image/png')
 
+    .. versionchanged:: 1.7
+
+      If you specify a ``mimetype`` of ``message/rfc822``, it will also accept
+      :class:`django.core.mail.EmailMessage` and :py:class:`email.message.Message`.
+
+      In addition, ``message/rfc822`` attachments will no longer be
+      base64-encoded in violation of :rfc:`2046#section-5.2.1`, which can cause
+      issues with displaying the attachments in `Evolution`__ and `Thunderbird`__.
+
+      __ https://bugzilla.gnome.org/show_bug.cgi?id=651197
+      __ https://bugzilla.mozilla.org/show_bug.cgi?id=333880
+
 * ``attach_file()`` creates a new attachment using a file from your
   filesystem. Call it with the path of the file to attach and, optionally,
   the MIME type to use for the attachment. If the MIME type is omitted, it
   will be guessed from the filename. The simplest use would be::
 
     message.attach_file('/images/weather_map.png')
 
-.. _DEFAULT_FROM_EMAIL: ../settings/#default-from-email
-
 Sending alternative content types
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/mail/tests.py

@@ -331,6 +331,39 @@ def test_dont_base64_encode(self):
         self.assertFalse(str('Content-Transfer-Encoding: quoted-printable') in s)
         self.assertTrue(str('Content-Transfer-Encoding: 8bit') in s)
 
+    def test_dont_base64_encode_message_rfc822(self):
+        # Ticket #18967
+        # Shouldn't use base64 encoding for a child EmailMessage attachment.
+        # Create a child message first
+        child_msg = EmailMessage('Child Subject', 'Some body of child message', 'bounce@example.com', ['to@example.com'], headers={'From': 'from@example.com'})
+        child_s = child_msg.message().as_string()
+
+        # Now create a parent
+        parent_msg = EmailMessage('Parent Subject', 'Some parent body', 'bounce@example.com', ['to@example.com'], headers={'From': 'from@example.com'})
+
+        # Attach to parent as a string
+        parent_msg.attach(content=child_s, mimetype='message/rfc822')
+        parent_s = parent_msg.message().as_string()
+
+        # Verify that the child message header is not base64 encoded
+        self.assertTrue(str('Child Subject') in parent_s)
+
+        # Feature test: try attaching email.Message object directly to the mail.
+        parent_msg = EmailMessage('Parent Subject', 'Some parent body', 'bounce@example.com', ['to@example.com'], headers={'From': 'from@example.com'})
+        parent_msg.attach(content=child_msg.message(), mimetype='message/rfc822')
+        parent_s = parent_msg.message().as_string()
+
+        # Verify that the child message header is not base64 encoded
+        self.assertTrue(str('Child Subject') in parent_s)
+
+        # Feature test: try attaching Django's EmailMessage object directly to the mail.
+        parent_msg = EmailMessage('Parent Subject', 'Some parent body', 'bounce@example.com', ['to@example.com'], headers={'From': 'from@example.com'})
+        parent_msg.attach(content=child_msg, mimetype='message/rfc822')
+        parent_s = parent_msg.message().as_string()
+
+        # Verify that the child message header is not base64 encoded
+        self.assertTrue(str('Child Subject') in parent_s)
+
 
 class BaseEmailBackendTests(object):
     email_backend = None