Doveadm service as non-root user

[Mark Moseley]

On Fri, Feb 1, 2019 at 11:37 PM Aki Tuomi <aki.tuomi at open-xchange.com>
wrote:

>
> On 01 February 2019 at 23:16 Mark Moseley < moseleymark at gmail.com> wrote:
>
>
> Running: Ubuntu xenial, dovecot 2.2.36
>
> I've been working on moving our user base from maildir to mdbox and trying
> to come up with solutions for things like moving emails around. In the
> past, with maildir, our support guys could just mv the files around and
> done. For mdbox, I've been working on getting things set up to use
> doveadm.
>
> One weirdness I've seen is that in imports (i.e. doveadm import), mail
> gets
> copied correctly but the resulting files are left with root ownership (I
> don't have 'service doveadm' 'user' set, so I guess it defaults to root).
> It's typically new m.* files as well as the dovecot.list.index
> and dovecot.list.index.log files.
>
> Looking at strace, no chown is done on them, nor was there setuid. The
> import had no trouble finding the correct user in the db, so I know that
> it
> knows the correct UID (I can see it just fine in debug logs too). And it
> will happily import to existing m.* files with no permissions issues (but
> considering it's running as root, I wouldn't expect it to).
>
> I've seen this using 'import' via IMAPc as well as with both src and dest
> on the same server. I can see this behavior in both scenarios. We have a
> single shared UID for mail, so especially in that "src/dest on same
> server"
> case, it's not a matter of UID-mismatch.
>
> It's a director setup, so all doveadm commands are coming through the
> director. If I run the import directly on the backend (which obviously
> would be a bad idea in real life), the ownership of new m.* files seems to
> be correct (I can see it setuid'ing to the correct UID from userdb in
> strace). If I run the import on the director, I can get a new root-owned
> file every time it rolls over to the next m.* file.
>
> Two questions:
>
> * Is that a bug? Is this expected behavior? Seems like the expected thing
> would be to use the UID from userdb and either do a setuid (just like
> running 'doveadm import' locally did) or chown'ing any new files to the
> correct UID. I always always assume misconfiguration (vs bug, since it's
> almost never a bug) but I'm baffled on this one.
>
> * I see that it's possible to set a user for service doveadm and the wiki
> even suggests that it's a good idea in a single UID setup. If there are no
> mailboxes with any other UIDs, *will setting 'service doveadm' to the same
> UID possibly break anything*? I can't think of why it would, but I want to
> be duly diligent. Plus I'm a little leery about closing the door to ever
> having additional UIDs for mailboxes.
>
> Happy to provide 'doveconf -n' but wanted to check first, before spending
> 15 minutes gently obfuscating it :)
>
>
> Can you try
>
> doveadm import -U victim -u victim ... ?
> ---
> Aki Tuomi
>


Is that to test a generic 'import from sourceUser to dest user' (i.e.
victim isn't literally the same in both -u and -U) or are you looking for a
test where 'sourceUser' is the same email account as the destination?

I just want to make sure I'm understanding right. The original tests (that
result in the root-owned files) were all -U userA -u userB (i.e. different
email accounts for src and dest), if you're asking about the former.

If you're asking about the latter, I ran that and got the same result, a
root-owned dovecot.list.index.log and dovecot.list.index and freshly
created m.* files. The message count in the destination mailbox increases
by the right number (no surprise since it's running as root), so the import
itself is working.

I should add that in both cases (different src/dest email account and same
src/dest), the import works ok -- or at least increments the count in the
index. It just leaves the email account in a broken state. Re-chown'ing it
to the current permissions makes it happy again and the newly imported
messages show up.
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