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'] = 'dovecot';
$config['password_dovecotpw'] = '/usr/bin/doveadm pw';
$config['password_algorithm_prefix'] = '{PBKDF2}';
$config['password_dovecotpw_method'] = 'PBKDF2';

$config['password_ldap_host'] = '{{getenv "LDAP_HOST"}}';
$config['password_ldap_port'] = '{{getenv "LDAP_CONNECTION_PORT" "389"}}';
$config['password_ldap_version'] = '3';
$config['password_ldap_starttls'] = {{getenv "LDAP_STARTTLS" "true"}};
$config['password_ldap_basedn'] = '{{getenv "LDAP_BASE_DN"}}';
$config['password_ldap_method'] = 'user';
$config['password_ldap_userDN_mask'] = '{{getenv "LDAP_USER_DN_MASK"}}';

$config['password_ldap_encodage'] = 'default';
$config['password_ldap_pwattr'] = '{{getenv "LDAP_PASSWORD_ATTRIBUTE" "userPassword"}}';
$config['password_ldap_force_replace'] = true;