Dovecot crashes when authenticating for SMTP

[Former user]

Hi, I've just given your docker container a try and got receiving emails to work flawlessly so far. Great job on preparing everything to be so simple!

But I can not get sending mails to work, neither from roundcube or an external client. The dovecot process always dies like this:

Dec 23 15:54:16 fe622512ddb5 mail.err dovecot: auth: Error: BUG: Authentication client sent unknown command: XixKQ<.........>n1g
Dec 23 15:54:16 fe622512ddb5 mail.crit dovecot: auth: Panic: key not found from hash
Dec 23 15:54:16 fe622512ddb5 mail.err dovecot: auth: Error: Raw backtrace: /usr/lib/dovecot/libdovecot.so.0(+0x7aee2) [0x7f8953c7aee2] -> /usr/lib/dovecot/libdovecot.so.0(+0x7afcd) [0x7f8953c7afcd] -> /usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f8953c1fa61] -> dovecot/auth(+0x1809c) [0x7f895413b09c] -> dovecot/auth(+0x1828d) [0x7f895413b28d] -> dovecot/auth(auth_request_handler_reply+0x139) [0x7f895413bce9] -> dovecot/auth(+0x16f35) [0x7f8954139f35] -> dovecot/auth(auth_request_verify_plain_callback+0x48) [0x7f8954139fb8] -> dovecot/auth(+0x28291) [0x7f895414b291] -> dovecot/auth(+0x1dbca) [0x7f8954140bca] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x4c) [0x7f8953c8ec6c] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x101) [0x7f8953c90101] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0x25) [0x7f8953c8ecf5] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f8953c8ee98] -> /usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f8953c25583] -> dovecot/auth(main+0x38f) [0x
Dec 23 15:54:16 fe622512ddb5 mail.crit dovecot: auth: Fatal: master: service(auth): child 3944 killed with signal 6 (core not dumped)

The client doesn't notice anything and just sits there until the connection times out.

I tried different auth mechanisms, PLAIN and LOGIN produce this error, while CRAM-MD5 doesn't seem to be supported at all. Also connection via STARTTLS or direct SSL doesn't make a difference. I generated DKIM keys for the domain (by clicking the button), but didn't put them into DNS yet.

Is this possibly a bug with the container, or am I doing something wrong? I'm not familiar with dovecot, so I don't know how to debug this. Any hints would be appreciated :)

Thanks

[RE]

I ran into the same issue. FWIW, it only happened for a single user account—every other account I’ve tried has been fine. Haven’t had the time to repro, but the error message is exactly the same apart from the “command” on the first line.

[Marius Hanne]

Aha, reducing the password length from 128 characters to 64 helped :) Maybe the admin UI could catch that?

[SH]

Yes, UI will catch this next release. I will investigate why dovecot can't take such long password, I don't like this limit at all...