[Dovecot] patch: list shared namespace

[Bernhard Herzog]

Hi,

I've been working on a patch for dovecot 1.2 from the Kolab branch
(http://hg.intevation.org/kolab/dovecot-1.2_kolab-branch/) that
implements listing of shared namespaces.  I've got something that works
in some basic way but is still missing some pieces.  See the attached
patch, which also contains some installation and configuration notes.


Implementation notes: 

One of the main problems the patch addresses is getting a list of all
users that have mailboxes the logged in user can see.  The patch uses a
dict to cache information about which users have at least one mailbox
that is visible to other users.  The dict doesn't cache which other
users, though.  The cache entry for a given user is updated whenever the
dovecot-acl-list file in the maildir root directory is updated.  This
ties the implementation to a specific acl backend to an extent, but that
shouldn't be a problem at the moment.

Another problem is that namespaces for all those users have to be
created.  The patch does that in shared-storage.c when the shared
storage is created.  At this stage of development of the patch that
works well enough, I think, but it might be better to update the
namespaces whenever a list iterator is created.

To avoid unnecessary coupling between the shared namespace code and the
ACL plugin, the shared namespace code has a hook that it calls when it
needs a list of all the users who may have mailboxes visible to the
current user.  The ACL plugin sets that hook and uses the dict to
produce that list.  This way, the ACL plugin depends on the shared
namespace code but not the other way round and all the dict handling is
in the ACL plugin.

I'm not sure the new hook is really needed.  The patch could perhaps
just as well extend the acl_next_hook_mail_storage_created and
acl_next_hook_mailbox_list_created functions to do the namespace
creation when they're called for a shared storage or mailbox list.


Problems:

All of my tests so far involved a shared namespace of the form

namespace shared {
  separator = /
  prefix = users/%%u/
  location = maildir:.../var/mail/%%u:...
  subscriptions = no
  list = yes
  hidden = no
}

Also, let's assume two users, ford and arthur with ford's "INBOX/hhgttg"
available to arthur as "users/ford/INBOX/hhgttg".  Arthur may not list
ford's INBOX, though.  In the following the current user is always
arthur.

I found the following problems:

 - LIST response includes namespaces the user doesn't really have access
   to.  E.g. if there's another user, zaphod who's made some mailbox
   available to somebody else, but not arthur, arthur still sees

   * LIST (\Noselect \HasChildren) "/" "users/zaphod"

   Not sure it's worth fixing this, though.

 - List with "%" doesn't list all intermediate mailboxes.

   On the one hand arthur sees this:

     x LIST "" "*"
     ...
     * LIST (\Noselect \HasChildren) "/" "users/ford"
     * LIST (\HasNoChildren) "/" "users/ford/INBOX/hhgttg"
     x OK List completed.

   OTOH, with "%" only this:

     x LIST "" "users/ford/%"
     x OK List completed.

   cyrus shows

     x LIST "" "users/ford/%"
     * LIST (\Noselect \HasChildren) "/" "users/ford/INBOX"
     x OK List completed.

   At least Kontact resp. KMail rely on this.

 - The dovecot-acl-list is not always rebuilt, even when it should have
   been, AFAICT.  In particular, if the file exists but is empty, it's
   never updated, even when ACL later change.  Maybe this is a bug in
   the Kolab branch.


Cheers,

   Bernhard

-- 
Bernhard Herzog  |  ++49-541-335 08 30  |  http://www.intevation.de/
Intevation GmbH, Neuer Graben 17, 49074 Osnabrück | AG Osnabrück, HR B 18998
Geschäftsführer: Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
-------------- next part --------------
A non-text attachment was scrubbed...
Name: list-shared-namespaces-20081028.diff
Type: text/x-diff
Size: 9845 bytes
Desc: not available
Url : http://dovecot.org/pipermail/dovecot/attachments/20081028/035cd760/attachment-0002.bin 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part.
Url : http://dovecot.org/pipermail/dovecot/attachments/20081028/035cd760/attachment-0003.bin