System installed : Dovecot 2.2.12 as IMAP server and Postfix as MTA. Dovecot and Postfix connected via LMTP
- Dovecot mail plugin 'mail-filter' to encrypt/decrypt emails on the fly with public/private users' RSA keys.
Case study : You have 3 (virtuals) users belonging to 3 different domains, all managed by your Dovecot server. One of these users is connected to Dovecot with MUA Thunderbird, and he's writing an email to someone outside of yours domains, but he puts the two others users' email addresses in CC : mail from user1@domain1.dovecot --> to: someone@outside, CC: user2@domain2.dovecot, user3@domaine3.dovecot
What happens (as far as I can understand) : The email is submitted to Postfix : one copy is delivered outside, the other is passed to Dovecot via LMTP for user2 & user3 @dovecot Dovecot is handling the final delivery, through mail-filter plugin as follow :
- both users contexts are created from user_db queries
- mail-filter plugin is init for user2
- /mail_user_created/ for user2
- mai-filter plugin arguments are parsed for user2
- â¦/mail_allocated/ then /mail_save_begin/ for user2 (at this stage, the email is encrypted with users2 params)
- Dovecot tells to LMTP that mail for user2 is delivered
- then, â we are still in user2 context â, an other /mail_allocated/ is run, followed by a /istream_opened/
- mail user context is swithed to user3 --> /mail_user_created/ --> plugin's args parsed --> ⦠/mail_allocated/
- and⦠Dovecot tells to LMTP that mail for user3 is delivered
So, it appears that Dovecot is re-using user2's email to pass it to user3 by opening an istream in user2's context. In my configuration, Dovecot can't do that because it has not the user2's private rsa key to reopen the email it has just encrypted, so it passes the email to user3 with user2 encryption params. Final result : user3 is receiving the email encrypted with user2's rsa key !
Problem : how to force Dovecot to deinit then reinit mail-filter plugin for each user to be sure that each email is encrypted with the right key before it is saved to users' mailboxes ?
Thank you in advance for your help.
Stan.