Introduction

During a migration from one IMAP server to another, the need arose to run both the old and the new IMAP servers in paralell. By default,

Horde only allows a single primary server to be enabled in servers.php. Of course, we could have allowed our users to simply select

their server by enabling IMAP server selection, but there is a better way. What follows are instructions on using a MySQL backend to

select an IMAP server for authentication, given a username:

The SQL table

There are many ways to do this of course. In this example, we'll just be using a table with two rows:

---------------------------------------------------------

|   username        |     server.domain.com             |

---------------------------------------------------------

Your table can be constructed however you like. It can even be a part of your existing Horde DB. The important point is that you need the

table to be constructed in such a way as to be able to query a username and have the lookup return a servername. Our example

uses a table called 'host'.

Writing a hook

Here's some sample code for a hook placed inside horde/config/hooks.php:

if (!function_exists('_imp_hook_imap')) {

        function _imp_hook_imap($userName)

        {

                global $conf;

                include_once 'DB.php';

                $_db = &DB::connect($conf['sql'], true);

                $query = sprintf('SELECT server FROM host WHERE user=%s', $_db->quote($userName));

                $result = $_db->getOne($query);

                if (!is_a($result, 'PEAR_Error')) {

                        return $result;

                } else {

                        return false;

                }

        }

} 

Placing the hook into the session

The above hook returns a single line containing a server name. The results are injected into /horde/imp/lib/Session.php as follows:

        if (!empty($GLOBALS['conf']['hooks']['imap'])) {

                require_once HORDE_BASE . '/config/hooks.php';

                if (function_exists('_imp_hook_imap')) {

                        $_SESSION['imp']['server'] = call_user_func('_imp_hook_imap',  $_SESSION['imp']['user']);

                        }

        }

On our setup, this is done right before authentication is attempted (right around line 223). As best I can tell, you're fine so long

as you don't have $_SESSION['imp']['server'] overwritten by anything else before you get to the call to &Auth::singleton(array('imp', 'imp'));

Disclaimer

This code works on our setup thus far. It could be wrong, uneccesary, foolish, or otherwise idiotic. In short, YMMV.

Questions? Send them to mp@xmission.com