[bug 2.3.15] seeing user-shared mailboxes across different storage types requires manual change to subscriptions

[Michal Soltys]

On 7/6/21 6:40 PM, Michal Soltys wrote:
> Hi,
> 
> While I was checking old bug I once reported (that one seems to be 
> fixed, https://www.dovecot.org/list/dovecot/2017-January/106593.html) I 
> discovered another issue happening under current version when user 
> sharing his mailbox (with Maildir storage) is not visible under user 
> using mdbox (or sdbox, also tested) - unless subscriptions file is 
> manually adjusted (after subscribing).
> 
> Consider following config:
> 
> # 2.3.15 (0503334ab1): /etc/dovecot/dovecot.conf
> # OS: Linux 5.12.14-arch1-1 x86_64 Arch Linux btrfs
> # Hostname: hakai
> auth_debug = yes
> auth_mechanisms = plain login
> disable_plaintext_auth = no
> first_valid_uid = 1
> listen = *
> mail_debug = yes
> mail_gid = dovecot
> mail_location = maildir:/var/mail1/%n/Maildir
> mail_plugins = acl
> mail_uid = dovecot
> namespace {
>    inbox = yes
>    location =
>    prefix =
>    separator = /
>    type = private
> }
> namespace shared1 {
>    inbox = no
>    list = yes
>    location = maildir:%%h/Maildir/
>    prefix = shared1/%%n/
>    separator = /
>    subscriptions = no
>    type = shared
> }
> namespace shared2 {
>    inbox = no
>    list = yes
>    location = mdbox:%%h/mdbox/
>    prefix = shared2/%%n/
>    separator = /
>    subscriptions = no
>    type = shared
> }
> passdb {
>    args = /etc/dovecot/local-maildir
>    driver = passwd-file
> }
> passdb {
>    args = /etc/dovecot/local-mdbox
>    driver = passwd-file
> }
> plugin {
>    acl = vfile
>    acl_shared_dict = 
> file:/var/mail-data/shared-database/shared-mailboxes.db
> }
> protocols = imap
> service auth {
>    unix_listener auth-userdb {
>      group = mail
>      mode = 0660
>      user = dovecot
>    }
>    user = dovecot
> }
> service imap-login {
>    inet_listener imap {
>      address = *
>      port = 143
>    }
>    inet_listener imaps {
>      address = *
>      port = 993
>    }
>    user = dovecot
> }
> service imap {
>    executable = /usr/lib/dovecot/imap
> }
> userdb {
>    driver = prefetch
> }
> userdb {
>    args = /etc/dovecot/local-maildir
>    driver = passwd-file
> }
> userdb {
>    args = /etc/dovecot/local-mdbox
>    driver = passwd-file
> }
> protocol imap {
>    mail_max_userip_connections = 100
>    mail_plugins = acl imap_acl
> }
> 
> /etc/dovecot/local-maildir:
> 
> user1:{PLAIN}test:::user1:/var/mail1/user1::userdb_mail=maildir:/var/mail1/user1/Maildir 
> userdb_home=/var/mail1/user1
> user2:{PLAIN}test:::user2:/var/mail1/user2::userdb_mail=maildir:/var/mail1/user2/Maildir 
> userdb_home=/var/mail1/user2
> 
> /etc/dovecot/local-mdbox:
> 
> user3:{PLAIN}test:::user3:/var/mail2/user3::userdb_mail=mdbox:/var/mail2/user3/mdbox 
> userdb_home=/var/mail2/user3
> 
> There are two shared namespaces - shared1 for Maildir mailboxes and 
> shared2 for mdbox ones. 'user1' is sharing his 'qwer' folder to user3.
> 
> doveadm mailbox create -u user1 -s qwer
> doveadm acl add -u user1 qwer user=user3 read lookup
> doveadm mailbox subscribe -u user3 shared1/user1/qwer
> 
> This produces subscriptions file such as:
> 
> 14:44 # cat /var/mail2/user3/mdbox/subscriptions
> V       2
> 
> Trash
> shared1    user1    qwer
> 
> With all that in place, 'qwer' won't be visible to user3. But if we 
> change the 'shared1    user1    qwer' to shared1/user1/qwer - then 
> everything will be working fine.
> 
> Sharing mdbox folder to maildir user (user3 -> user1) as well as maildir 
> to maildir (user1 -> user2) works without issues.

So any ideas about it ? Should I just assume that this kind of usage 
(cross-storage sharing) is a corner-case and overall should be avoided ?

I noticed potential other issue, where certain control/index files from 
users were created across the storage as well - for example, for the 
configuration as above, user3 (nominally under /var/mail2/ tree) would 
also end with:

15:31 # ls -laR /var/mail1/user3/
/var/mail1/user3/:
total 0
drwx------ 1 dovecot dovecot 14 Jul 29 15:14 .
drwxr-xr-x 1 dovecot dovecot 30 Jul 29 15:14 ..
drwx------ 1 dovecot dovecot 76 Jul 29 15:14 Maildir

/var/mail1/user3/Maildir:
total 4
drwx------ 1 dovecot dovecot  76 Jul 29 15:14 .
drwx------ 1 dovecot dovecot  14 Jul 29 15:14 ..
-rw------- 1 dovecot dovecot   0 Jul 29 15:14 dovecot-acl-list
-rw------- 1 dovecot dovecot 288 Jul 29 15:14 dovecot.list.index.log