Re: Group-readable email and overriden ACL's
- On Tue, Aug 23, 2011 at 11:11:31AM -0400, Wietse Venema wrote:
> Kasper Loopstra:Support for multi-user access is the job of the mail-store, not the MTA.
> > Dear list members,
> > In our setup we have various mailboxes that have to be read (and edited)
> > by groups of people. All these groups are defined in LDAP, as are the
> > members (everything uses PAM, so all these accounts are on the system as
> > well). The email is accessed by Dovecot, binding with the LDAP server as
> > the user owning the mail. This means that all the mail for a certain
> > user has to be accessible to that user on the system, otherwise Dovecot
> > cannot read it. We use public namespaces in Dovecot to achieve this.
> > Our problem is that postfix gives permissions 700 to all messages
> > (overriding default ACL's). The messages may be owned by the correct
> > group for a user, and be in the right folder, but still cannot be read
> > by Dovecot (and our users). Hopefully, there is a more elegant solution
> > then monitoring the filesystem for edits and changing the permissions
> > when a mail folder is edited.
> In this case, the solution would be to deliver and read the mail
> with dovecot, and to configure the permissions with Dovecot if
> Postfix implements only bare-bones email delivery and does not
> support access by multiple UIDs other than the owner and root.
IMAP servers like Cyrus, Dovecot, ... have appropriate mailbox access-control
mechanisms that allow access by multiple (typically IMAP) users, and in some
cases access to the underlying files via local clients running as the user.
Work with the mail-store. Direct access to the underlying files is probably
not a good idea.