On 14. 09. 20 22:46, Daniel Miller wrote:
On 9/14/2020 1:19 PM, Matej Tyc wrote:
...
When learning about how ACL work in e.g.
https://doc.dovecot.org/settings/plugin/acl/ - when one wishes to use
the Global ACL file, how does one link it to a particular user's
mailboxes? Examples that are listed in the documentation are far too
generic. For example does "* user=foo lrw" imply that all mailboxes
of all accounts are shared to the user foo? The doveadm command works
only if dovecot is set up with per-mailbox ACL files, so I can't use
it to reverse-engineer the correct syntax.
The global ACLs are...global. They apply to all matching mailboxes
system-wide. So to answer your question, yes "* user=foo lrw" means
all mailboxes of all accounts are shared to the user foo. But...
Great, what about the format itself? Is it
<namespace>/<account>/<mailbox>? The documentation brings up, i.e.
/[email protected]/* shares all mailboxes of John from the example.com
domain? Or have I overlooked a documentation page where the syntax is
introduced?
...
The ACLs grant/deny access to a specific mailbox - when that mailbox
is known to the client. But ACLs are never scanned or iterated over to
generate a list of available mailboxes - that's where the dictionary
comes in. The dictionary is a list of shared mailboxes - but that's
all it is. So when a client queries the server for a list of available
mailboxes the dictionary is consulted. The ACLs are then applied for
each transaction whenever a client tries to read/write/access/whatever
a specific mailbox. So theoretically, if you can manually specify the
shared mailbox correctly, no dictionary is required for access.
Thanks, that's a great explanation!
Next what https://wiki.dovecot.org/SharedMailboxes/Shared and
https://wiki.dovecot.org/Dictionary describe is a possibility to
reference LDAP data to define an ACL dictionary. Do I understand it
correctly that if a LDAP database is the single source of truth, then
I don't have to worry about updating dictionaries as long as LDAP
itself is up-to-date, but I have to keep ACLs and LDAP in sync
manually (or using an application)?
Again, a dictionary is a list of shared mailboxes - not ACL's. You can
use any dictionary source Dovecot can read from - but if the
dictionary also supports writing then any manipulation of ACLs will
automatically update the dictionary.
What the above implies, and I will now state explicitly, is that while
global ACLs provide *access* they do not *publish* that access. A
dictionary must be manually updated to list those mailboxes.
What I understand is that ACLs are purely filesystem-based, i.e. no LDAP
backend, and one has to sync LDAP to respective ACLs "manually".
If I follow what you have said, one could have an equal result with a
database, syncing ACLs "manually" from LDAP, and doveadm will make sure
that the database backend will be up-to-date.
--
Daniel
Thank you very much for your explanations, I will propose a
documentation PR once I figure out all of the missing bits.
