Multipart emails with empty multiline text part break DKIM

[GioPan04]

This is a similar issue to #411, although much specific.
I've noticed that If a multipart email (text and html) is sent and the text part contains more than 5 empty lines (both \r\n and \n) the email won't get correctly signed.

• This message contains 5 empty lines and gets correctly signed working.txt

• This message contains 6 empty lines and is not correctly signed fail.txt

I've also noticed that if a message is not correctly signed one empty line gets removed from the text part (this maybe the reason for the failing DKIM).

• This is the message downloaded from gmail (the receiving server) which was sent with 5 empty new lines: pass-gmail.txt

• This is the message downloaded from gmail which was sent with 6 empty new lines: fail-gmail.txt

[andris9]

Yes, the current DKIM signing implementation is buggy. I plan to replace it with https://github.com/postalsys/mailauth which has a better, more tested implementation

[GioPan04]

Is there any ETA on this?

[andris9]

Try v 3.10.0

[GioPan04]

I'm still experiencing this issue.
A line between the multiparts is deleted after the dkim is calculated, breaking the previous body hash altogether.

I'm using Zone-MTA 3.10.0

[GioPan04]

I was able to isolate the issue.
It seems like that if I connect to TLS or STARTTLS the DKIM is incorrectly calculated. When I connect to the raw 25 port the DKIM is valid.