Magento Force Admin Login With Password

magento-auth-admin-pass

Mage::app("default");

$username = 'admin'; 
$password = 'password'; 

try{   
    $authenticated = Mage::getModel('admin/user')->authenticate($username, $password); 
} catch ( Exception $e ) {  
    $authenticated = false;  
}

// Do something depending on whether $authenticated is truthy