Hi Matthijs,
On 6/1/2012 8:27 PM, Matthijs Kooijman wrote:
I'm setting up a dovecot server with managesieve support. I'd like to
offer spamfiltering through a Sieve script to my users by default,
but still allow them to modify the filtering rules through Managesieve.
I found the sieve_global_path configuration option, which seems perfect
for what I want. I can configure a default script there, which will work
for all users until they set upload their own sieve script using
managesieve.
However, when configured like this, the user experience isn't quite
perfect. When users open the managesieve interface on their client,
there is no trace of the default filters, so users might think the
spamfiltering is done in some other manner. Now, when they create a
filtering rule (e.g., to sort out mail to mailing lists), that rule will
overwrite the default spamfiltering rule causing all the spam to spill
into the user's mailbox. I'm afraid that most users won't realize they
have to manually recreate the spamfiltering rule to fix this. Also, they
might not know how to write the rule, even if they do...
You asked this one on IRC a while back right?
I've considered a few existing ways to fix this:
- Use sieve_before / sieve_after to make sure that the default script
is always executed, in addition to any user-supplied scripts. This
removes the surprise, but removes the option for users to tweak the
spamfiltering rules.
Right.
- Don't use sieve_global_path, but instead distribute the default
script to each user's homedir on user creation. This prevents making
changes to the default script for existing users and in my setup,
user creation and (mail)homedir creation are nicely separated through
an LDAP directory, I'd rather not go this route.
Well, we could achieve something that looks very similar from the
outside: we could do some sort of copy-on-write scheme in which users
see the default script as the active one, until they first modify their
Sieve configuration through ManageSieve. Once they modify their default
script, they'll get their own copy. If they activate a script different
from the default and then later decide to deactivate it, their default
will not return as the (implicit) active one. This would be very
different from the current global default script behavior. It is more
like an initial placeholder and template, than something that is always
active when the user has no active script of its own.
- When using the Roundcube webmail application as the IMAP client, I
can point Roundcube at the default sieve script. Now, when Roundcube
sees there are no scripts through ManageSieve, it shows a (fake)
"default" script with the correct contents. As soon as the user
changes this script or creates a new script, it is actually uploaded
to Dovecot, causing the edited script to be used instead of the
global script
This option has the user experience I'm looking for, but having this
out-of-band connection from Roundcube to the default script
configured with dovecot is ugly (and tricky, since these run on
different hosts in my setup). The biggest problem is of course that
this only works for Roundcube, not for any other IMAP client my users
might use.
Agreed, this is ugly since it uses a side-channel. Client dependence is
also very bad.
So, I was wondering: Wouldn't it make sense for the managesieve plugin
to do something similar to roundcube: When the user has no sieve script
configured, let it fake a single "default" script, showing the contents
of the global script?
Since the ManageSieve protocol doesn't seem to support any way to flag
this situation, it would be fooling the clients a bit, but I'm not sure
if that's really a problem.
While the user has not script named "default" in his sieve_dir:
- include a script called "default" in the LISTSCRIPTS output.
- return the contents of the sieve_global_path in the GETSCRIPT
"default" command.
- remove any sieve symlink after a SETACTIVE "default" command (as if
SETACTIVE "" was given). This causes dovecot to fall back to the
sieve_global_path script.
- the DELETESCRIPT "default" command should fail. This might confuse
clients and users, since it is listed in LISTSCRIPTS but cannot be
deleted, but I think most users will understand they can't delete the
default script.
- RENAMESCRIPT "default" "some_name" should copy the sieve_global_path
script into the user's sieve_dir. This will effectively copy the
script instead of renaming it (since it will still be magically
listed in LISTSCRIPTS), so that might be confusing.
All other commands work just like they do now (in particular,
PUTSCRIPT "default" uploads a script called "default" into the user's
sieve_dir, preventing all of the above from applying.
This looks sensible. The only thing that may be an issue is the
DELETESCRIPT "default" situation you describe
