Bug in handling encoded/decoded mail messages

[sgros]

Hi!

I'm having a serious issue with certain mails. And this is manifesting itself in versions from cca. 5.0.18 until 6.0.6. The problem is that when a users sends an email, the attachment is received either stripped or incomplete, or the mail is quarantined without any notification. In the log files I found the following error messages related to this behavior:

Jun 9 08:22:15 mail amavis[29212]: (29212-07) Checking: WpwkNKa1zI0Z [1.1.1.1] <abc@def.hr> -> <ghi@dr.def.hr>,<ghi@dr.def.hr>,<ghi@
def.hr>
Jun 9 08:22:15 mail amavis[29212]: (29212-07) WARN: MIME::Parser error: part did not end with expected boundary
Jun 9 08:22:15 mail amavis[29212]: (29212-07) local delivery: <> -> bad-header-quarantine, mbx=/opt/zimbra/data/amavisd/quarantine/badh-WpwkNKa1zI0Z

After some investigation I found out that the problem is with email messages that have lines which end with a dot, e.g.

This is a line that has 74 characters and ends in a dot.

Email client is encoding those lines in the following way:

This is a line that has 74 characters and ends in a dot=
..

But for some reason, one dot is then lost and the line translates into end of the message in the SMTP dialog (single dot in a line)!

For a record, I'm using altermime, but I doubt it's altermime's bug. I did the following experiments, all of which produced the error:

1. Using Webmail and sending mail to a local account
2. Using fat client and sending mail to a local account
3. Sending using foreign mail account to a local mail account. In this case altermime is not invoked.

So, it seems bug is somewhere in postfix. The file I'm using for tests is not for public and I tried to modify it so that I can publish it. But it seems that this particular error occurs only in a specific situations.

Note also that this error is dangerous because neither recipient nor sender receive any error message when the mail is discarded due to this bug.

[sgros]

I managed to generate test case that triggers this bug. The problem is specific and it occurs when there is line with certain format, 74 characters long that ends in a dot. Also, there has to be some non-ASCII character that will force mail client to encode the message.

So, in order to trigger the bug, create text file with the following line:

/xxxxxx/yyy/zzzz/unosN14.jsp[25] naziv_korisnika=xxxxxxx xxxxxxxx pte ltd.

after that line put some non-ascii character, and then put any text you like. When you send the mail with the file attached, the file will be cutted of at the last dot in the line.

So, the question is, how to get rid of this bug.

And yes, I tested with the version 6.0.5, but prior versions have this bug too.