Short
Working on login system and trying to implement remember me feature.
Recently, l did research about this subject, read bunch of articles, posts, stories, novels, fairy tales (calling them so, because some of them doesn't contain even 1 line of code, just loads of words) about, cookie vulnerabilities such as fixation, hijacking ... etc.
And decided to achieve following targets
- To set time delay between login attempts (to prevent bruteforce attacks) and to limit attempts count
- To regenerate session id on nearly every operation
But I really confused about my main problem: which way is proper, for "remember me" feature? to use cookies/session/database?
And please explain your idea on code.(I can't understand clearly without code)
Detailed
Currently, my code looks like that
During sign-in I'm using following function to set cookies and session
protected function validateUser($userid, $ckey=0, $rememmber=0) {
session_start();
session_regenerate_id(true); //this is a security measure
$_SESSION['user_id'] = $userid;
$_SESSION['HTTP_USER_AGENT'] = md5($_SERVER['HTTP_USER_AGENT']);
if (isset($remember) && $rememmber == 'on') {
setcookie("user_id", $_SESSION['user_id'], time() + 60 * 60 * 24 * COOKIE_TIME_OUT, "/");
setcookie("user_key", sha1($ckey), time() + 60 * 60 * 24 * COOKIE_TIME_OUT, "/");
}
return true;
}
Then on secure user pages, checking for user_id using user_id to fetch all important data about user from db
public function protect() {
session_start();
/* Secure against Session Hijacking by checking user agent */
if (isset($_SESSION['HTTP_USER_AGENT'])) {
if ($_SESSION['HTTP_USER_AGENT'] != md5($_SERVER['HTTP_USER_AGENT'])) {
$this->signout();
exit;
}
}
// before we allow sessions, we need to check authentication key - ckey and ctime stored in database
/* If session not set, check for cookies set by Remember me */
if (!isset($_SESSION['user_id'])) {
if (isset($_COOKIE['user_id']) && isset($_COOKIE['user_key'])) {
/* we double check cookie expiry time against stored in database */
$cookie_user_id = $_COOKIE['user_id'];
$stmt = $this->db->prepare("select `ckey`,`ctime` from `users` where `id` =?") or die($this->db->error);
$stmt->bind_param("i", $cookie_user_id) or die(htmlspecialchars($stmt->error));
$stmt->execute() or die(htmlspecialchars($stmt->error));
$stmt->bind_result($ckey, $ctime) or die($stmt->error);
$stmt->close() or die(htmlspecialchars($stmt->error));
// coookie expiry
if ((time() - $ctime) > 60 * 60 * 24 * COOKIE_TIME_OUT) {
$this->signout();
}
/* Security check with untrusted cookies - dont trust value stored in cookie.
/* We also do authentication check of the `ckey` stored in cookie matches that stored in database during login */
if (!empty($ckey) && is_numeric($_COOKIE['user_id']) && $_COOKIE['key'] == sha1($ckey)) {
session_regenerate_id(); //against session fixation attacks.
$_SESSION['user_id'] = $_COOKIE['user_id'];
$_SESSION['HTTP_USER_AGENT'] = md5($_SERVER['HTTP_USER_AGENT']);
} else {
$this->signout();
}
} else {
if ($page != 'main') {
header('Location:' . wsurl);
exit();
}
}
}