mail_crypt crashing randomly during LMTP

[Timo Sirainen]

On 31. Mar 2020, at 13.47, Timo Sirainen <timo at sirainen.com> wrote:
> 
> On 29. Mar 2020, at 17.07, Timo Sirainen <timo at sirainen.com> wrote:
>> 
>>> This is what the log says in the moment of crashing:
>>> dovecot: lmtp(53852): Panic: Module context mail_crypt_user_module missing
>>> *** backtrace *** (see: https://pastebin.com/YCiFtxmy)
>> 
>> It shows mailbox_free() in the backtrace, so it's probably crashing in mail_crypt_mailbox_close()'s MAIL_CRYPT_CONTEXT(box). But looking at the code, I can't see how that could be possible. Maybe there is some kind of memory corruption or something.
> 
> 
> Looks like there's a bug when some users have mail_crypt plugin loaded and other users don't. If LMTP delivers a mail to both users within the same session, it crashes at deinit. A workaround could be to tell MTA to deliver to max recipient at a time. We'll get this fixed also to some future release. You could also apply a patch:

Looks like there is also a better way to do this. Enable mail_crypt plugin always in dovecot.conf, but return mail_crypt_save_version differently for users. So mail_crypt_save_version=0 for users who don't want encryption, mail_crypt_save_version=2 for users who do want encryption.