roundcube/rootfs/etc/confd/templates/password-config.inc.php.tmpl

<?php

$config['password_driver'] = 'ldap_simple';
$config['password_confirm_current'] = true;
$config['password_require_nonalpha'] = false;
$config['password_hosts'] = null;
$config['password_force_save'] = true;

$config['password_algorithm'] = 'sha512-crypt';
$config['password_algorithm_prefix'] = '{CRYPT}';

$config['password_ldap_host'] = '{{getenv "LDAPHOST"}}';
$config['password_ldap_port'] = '389';
$config['password_ldap_version'] = '3';
$config['password_ldap_starttls'] = {{getenv "LDAPSTARTTLS"}};
$config['password_ldap_basedn'] = '{{getenv "LDAPBASEDN"}}';
$config['password_ldap_method'] = 'user';
$config['password_ldap_userDN_mask'] = '{{getenv "LDAPUSERDNMASK"}}';

$config['password_ldap_encodage'] = 'crypt';
$config['password_ldap_pwattr'] = '{{getenv "LDAPPASSWORDATTRIBUTE"}}';
$config['password_ldap_force_replace'] = true;