Bug: mimeTree rebuilding does not join boundaries by a line break delimiter (e.g. \r\n)

[titanism]

Can we make it so the mimeTree when rebuilt has proper line breaks with boundaries?

Before WildDuck:

Content-Type: multipart/mixed; boundary="------------cWFvDSey27tFG0hVYLqp9hs9"
MIME-Version: 1.0
Message-ID: <[email protected]>
To: [email protected]
From: [email protected]
Subject: test

This is a multi-part message in MIME format.
--------------cWFvDSey27tFG0hVYLqp9hs9
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

test

--------------cWFvDSey27tFG0hVYLqp9hs9
Content-Type: text/plain; charset=UTF-8; name="example.txt"
Content-Disposition: attachment; filename="example.txt"
Content-Transfer-Encoding: base64

ZXhhbXBsZQo=

--------------cWFvDSey27tFG0hVYLqp9hs9--

After WildDuck:

Content-Type: multipart/mixed; boundary="------------cWFvDSey27tFG0hVYLqp9hs9"
MIME-Version: 1.0
Message-ID: <[email protected]>
To: [email protected]
From: [email protected]
Subject: test

This is a multi-part message in MIME format.--------------cWFvDSey27tFG0hVYLqp9hs9 // <-------- RIGHT HERE
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

test

--------------cWFvDSey27tFG0hVYLqp9hs9
Content-Type: text/plain; charset=UTF-8; name="example.txt"
Content-Disposition: attachment; filename="example.txt"
Content-Transfer-Encoding: base64


--------------cWFvDSey27tFG0hVYLqp9hs9--

You can see the difference with the line break before boundary delimiter.

[titanism]

@andris9 PR submitted to fix this at #572

[andris9]

Seems to be an issue with the parser 🤔

[andris9]

This specific parser bug triggers if the email does not end with a linebreak character. How did you get this email? Any email received via SMTP always ends with a linebreak?

[andris9]

In any case, I verified it, and it is a legitimate bug. It should be extremely rare in production, as emails always end with a linebreak unless you compose an email manually and use APPEND to upload it. I guess this is why it hasn't been discovered before - you need a multipart email with no-multipart text content and without an ending linebreak.

[andris9]

But the issue is not on the composing side, but on the parsing side. The composer behaves correctly.

[titanism]

Thank you @andris9, excited to try this out in the v1.41.1 release #573! 🎉 🙏 🙇