On 14. 09. 20 22:46, Daniel Miller wrote:
On 9/14/2020 1:19 PM, Matej Tyc wrote:
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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. /john@example.com/* shares all mailboxes of John from the example.com domain? Or have I overlooked a documentation page where the syntax is introduced?
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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.