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GH-78319: Stop sending the UTF8 marker when appending messages to a mailbox.

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The UTF8 marker is defined in RFC 6855 and tells the server that the
message being appended contains UTF8 addresses, an unencoded UTF8 subject,
etc.  However, if a client appends a message containing UTF8 addresses but
without that marker, the bytes can only be parsed as UTF8 because that's
the only RFC-compliant way to parse those bytes.

RFC 6855 says clients MUST send the UTF8 marker.

Due to an accidental discrepancy, RFC 9051 (IMAP4rev2) does not contain
that marker. IMAP4rev2 was intended to be upwardly compatible with RFC
6855, but this problem broke that. This has no ill effects, since the
marker does not change the message's meaning.

While investigating the problem, I noticed that Python uses the marker
incorrectly: Python uses it to mark ALL messages if UTF8=ACCEPT support
has been enabled, not just ones that contain UTF8 addresses.

The best way forward appear to be using the syntax defined in RFC 9051 and
publishing a revision to RFC 6855, so this change modifies imaplib to
match RFC 9051.

FWIW JMAP is like IMAP4rev2 in this case; UTF8 is just there, without any
marker. Also, neither UTF8=ACCEPT, IMAP4rev2 or JMAP provide any way to
learn whether a message was stored with or without the marker.

This quasi-accidentally solves #78319 by removing the case that broke.
This commit is contained in:
Arnt Gulbrandsen 2023-07-26 11:37:13 +02:00
parent 4e04393b2f
commit 32ee63d34e
2 changed files with 2 additions and 4 deletions
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2
Lib/imaplib.py
View file

@ -411,8 +411,6 @@ class IMAP4:
else:
date_time = None
literal = MapCRLF.sub(CRLF, message)
if self.utf8_enabled:
literal = b'UTF8 (' + literal + b')'
self.literal = literal
return self._simple_command(name, mailbox, flags, date_time)

4
Lib/test/test_imaplib.py
View file

@ -324,7 +324,7 @@ class NewIMAPTestsMixin():
typ, data = client.append(None, None, None, msg_string.encode('utf-8'))
self.assertEqual(typ, 'OK')
self.assertEqual(server.response,
('UTF8 (%s)\r\n' % msg_string).encode('utf-8'))
('%s\r\n' % msg_string).encode('utf-8'))
def test_search_disallows_charset_in_utf8_mode(self):
class UTF8Server(SimpleIMAPHandler):
@ -775,7 +775,7 @@ class ThreadedNetworkedTests(unittest.TestCase):
self.assertEqual(typ, 'OK')
self.assertEqual(
server.response,
('UTF8 (%s)\r\n' % msg_string).encode('utf-8')
('%s\r\n' % msg_string).encode('utf-8')
)
# XXX also need a test that makes sure that the Literal and Untagged_status