Pigeonhole Sieve: Dict Lookup for Sieve Scripts
===============================================

Sieve scripts can be obtained from a number of different <types of locations>
[Pigeonhole.Sieve.Configuration.txt]. This page shows how to retrieve them from
a Dovecot dictionary [http://wiki2.dovecot.org/Dictionary] (abbreviated as
'dict'), which can have either a file or database backend.

To retrieve a Sieve script from the dict database, two lookups are performed.
First, the name of the Sieve script is queried from the dict path
'/priv/sieve/name/<name>'. If the Sieve script exists, this yields a data ID
which in turn points to the actual script text. The script text is subsequently
queried from the dict path '/priv/sieve/data/<dict-id>'.

The second query is only necessary when no compiled binary is available or when
the script has changed and needs to be recompiled. The data ID is used to
detect changes in the dict's underlying database. Changing a Sieve script in
the database must be done by first making a new script data item with a new
data ID. Then, the mapping from name to data ID must be changed to point to the
new script text, thereby changing the data ID returned from the name lookup,
i.e. the first query mentioned above. Script binaries compiled from Sieve
scripts contained in a dict database record the data ID. While the data ID
contained in the binary is identical to the one returned from the dict lookup,
the binary is assumed up-to-date. When the returned data ID is different, the
new script text is retrieved using the second query and compiled into a new
binary containing the updated data ID.

Note that, by default, compiled binaries are not stored at all for Sieve
scripts retrieved from a dict database. The ';bindir=<path>' option needs to be
specified in the <location specification> [Pigeonhole.Sieve.Configuration.txt].

Configuration
-------------

The script location syntax is specified as follows:

---%<-------------------------------------------------------------------------
sieve = dict:<dict-uri>[;<option>[=<value>][;...]]
---%<-------------------------------------------------------------------------

The following additional options are recognized:

user=<username> :
  Overrides the user name used for the dict lookup. Normally, the name of the
  user running the Sieve interpreter is used.

If the name of the Script is left unspecified and is not otherwise provided by
the Sieve interpreter, the name defaults to `default'.

Examples
--------

Using a flat file backend
-------------------------

Flat file example 1
-------------------

To retrieve the Sieve script named "keep" from the dict file
/etc/dovecot/sieve.dict:

---%<-------------------------------------------------------------------------
sieve = dict:file:/etc/dovecot/sieve.dict;name=keep
---%<-------------------------------------------------------------------------

The file /etc/dovecot/sieve.dict might look like this. Note that with the above
configuration, only the "keep" script will be used.

---%<-------------------------------------------------------------------------
priv/sieve/name/keep
1
priv/sieve/name/discard
2
priv/sieve/data/1
keep;
priv/sieve/data/2
discard;
---%<-------------------------------------------------------------------------

Flat file example 2
-------------------

Following on from example 1, a more advanced script. This notifies an external
email address when new mail has arrived. Note that the script all needs to be
on one line.

---%<-------------------------------------------------------------------------
priv/sieve/name/notify
5
priv/sieve/data/5
require ["enotify", "variables"]; if header :matches "From" "*" { set "from"
"${1}";} notify :importance "3" :message "New email from ${from}"
"mailto:other@domain.com?body=New%20email%20has%20arrived.";
---%<-------------------------------------------------------------------------

Using a SQL backend
-------------------

For greater flexibility, it's possible to use a SQL backend for your dict
scripts. First, set up a configuration file (such as
/etc/dovecot/dict-sieve-sql.conf) with your database configuration. This should
consist of the following parts:

---%<-------------------------------------------------------------------------
# The database connection params
connect = host=localhost dbname=dovecot user=dovecot password=password

# The name mapping that yields the ID of the Sieve script
map {
    pattern = priv/sieve/name/$script_name   # The name of the script, as per
the "sieve" config parameter
    table = user_sieve_scripts               # The database table
    username_field = username                # The field in the table to query
on
    value_field = id                         # The field which contains the
return value of the script ID
    fields {
        script_name = $script_name           # FIXME: The other database field
to query?
    }
}

# The name mapping that yields the script content from ID
{
    pattern = priv/sieve/data/$id            # The ID, obtained from above
    table = user_sieve_scripts               # The database table
    username_field = username                # The field in the table to query
    value_field = script_data                # The field which contains the
script
    fields {
        id = $id                             # FIXME: The other database field
to query?
    }
}
---%<-------------------------------------------------------------------------

Next, create a dict proxy service. Normally in /etc/dovecot/dovecot.conf:

---%<-------------------------------------------------------------------------
dict {
    sieve = pgsql:/etc/dovecot/dict-sieve-sql.conf.ext
}
---%<-------------------------------------------------------------------------

Finally, configure Sieve to check the dict (e.g. in
/etc/dovecot/conf.d/90-sieve.conf). This looks up a script called "active" in
the database.

---%<-------------------------------------------------------------------------
plugin {
    sieve = dict:proxy::sieve;name=active
}
---%<-------------------------------------------------------------------------

As with the flat file, the database query will need to return the Sieve script
all in one line, otherwise the subsequent lines will be ignored.

Note: you might need to <configure the proxy permissions> [Dict.txt]

Caching the compiled Sieve binaries
-----------------------------------

With the configuration described above, the Sieve binaries will be compiled
each time they are called. To improve performance, it is preferable to cache
them, which can be done using the bindir parameter, which is added to the Sieve
configuration. For example:

---%<-------------------------------------------------------------------------
{
    sieve = dict:file:/etc/dovecot/sieve.dict;name=keep;bindir=~/.sieve-bin
}
---%<-------------------------------------------------------------------------

Or:

---%<-------------------------------------------------------------------------
{
    sieve =
dict:file:/etc/dovecot/sieve.dict;name=keep;bindir=/var/sieve-scripts/%u
}
---%<-------------------------------------------------------------------------

*Note:* Sieve uses the ID number as its cache index and to detect the need to
compile. Therefore, if a script is changed, then its ID must also be changed
for it to be reloaded.

(This file was created from the wiki on 2019-06-19 12:42)
