Magento 1.8 – Check Admin User Privileges Programmatically

It's the current admin password of the user you are logged in with, not the one you are about to create.

My source below may some helpful.

events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="backend_auth_user_login_success">
        <observer name="name_of_observer_for_backend_auth_user_login_success" instance="\Instance\Class\Name" />
    </event>
</config>

Then create the observer.

class BackendAuthUserLoginSuccess implements ObserverInterface
{
    const DEFAULT_SESSION_NAME_OF_FRONTEND = 'PHPSESSID';

    /**
     * (non-PHPdoc)
     * @see \Magento\Framework\Event\ObserverInterface::execute()
     */
    public function execute(\Magento\Framework\Event\Observer $observer) {
        if (! isset($_COOKIE[self::DEFAULT_SESSION_NAME_OF_FRONTEND])) return;
        $backSessionId = session_id();
        $frontendSessionId = $_COOKIE[self::DEFAULT_SESSION_NAME_OF_FRONTEND];
        session_write_close();
        session_id($frontendSessionId);
        session_start();
        $_SESSION['admin'] = [$backSessionId];
        session_write_close();
        session_id($backSessionId);
        session_start();
        return;
    }
}

Now after admin login then you can get admin session id by front-end session in $_SESSION['admin'], and you can use session_id($_SESSION['admin'][0]) switch session details and continue.

This code need front-end session id already created, so must add one iframe (src=frontend.anypage) to backend/auth/login page.