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PHP Session Security

The following code can be used to generate separate content for 3 levels of users. One level is the public, another level is regular logged in users and the final level is the administrator. To make the login and access secure, the session variables from the login page must run through a select statement to check if they match the rows in the database table. When they do match, the if, else if and else statement displays the  proper content. Since session variavbles are stored on the server, the only way to see those session variables is to have access to the folder and files which stores the session variables, or write code into a php script which displays the session variables.

 $customerId = $_SESSION['memberId'];
 $customerLogin = $_SESSION['memberLogin'];
 $customerPassword = $_SESSION['memberPassword'];

$command_ogin = "SELECT login, password FROM logins WHERE customer_id ='$customerId'"; 
$result_login = mysqli_query($db, $command_login);
$row_login = mysqli_fetch_assoc($result_login);
$mylogin = $row_login['login'];
$mypassword = $row_login['password'];

if (!(is_numeric($customerId)) || $customerLogin!=$mylogin || $customerPassword!=$mypassword )  {
// general public
}else if(is_numeric($customerId) && $customerId!=1 && $customerLogin==$mylogin && $customerPassword==$mypassword ){
// other members other than admin stuff
// distinct admin member stuff

Although the method above allows security from others logging in with false credentials elsewhere, validating passwords that are sessions can be risky in some instances. For example, the following code could be added to a file (after session_start()) to display all session variables and the session id.

$session_id = session_id();
echo $session_id;
// get stored session variables $_SESSION
foreach($_SESSION as $key => $value) 
    echo $key . " = " . $value . "

Insecure Sessions With PHP Sample
Imagine the previous code example without the check for the logged in user’s password. If this is the case, the code will only check if session variables exist and the actual values remain unchecked. For all simplicity, let’s assume the code is used with a public php script called ‘My Friendly Social Network’. With the code below, you could login to the page as an admin that is hosted on a server, then, open the same page of the script that is located in a different folder on the different server. The new page would only check for the existence of the session variables. It would not check for username or password. Now that the new page thinks you are authenticated, it leaves security at the highest risk. To make things worse, the admin of one site could easily become the admin at the other site.

if (!(is_numeric($customerId)) )  {
// general public
}else if(is_numeric($customerId) && $customerId!=1 ){
// other members other than admin stuff
// distinct admin member stuff

The point to remember is that session variables can be created and used in any php application. Therefore, validating session variables with database table rows for specific session variables will keep the application more secure for all members.

If the php application was custom built, not open source and not a public script, it is much more secure. You see all sorts of open source code with security risks that programmers have discovered. If nobody has access to the insecure php script above which only checks for a session variable, there is a great chance that nobody would ever know the session variables other than the administrator; especially if the session variable is quite unique. The session variable ‘z_app_cred’ would more than likely be much more secure than ‘id’; should someone be crazy enough to try and guess.

Even though the application above is not as secure as it should be, it probably would not have issues since the session variables are secretive; especially if each user must be unique. Since the actual session id for each member is different, the can only get their session id through logging in. Nevertheless, checking session variables makes the application more secure.

You can always save session variables to desired folder using the session_save_path() function. Details on saving sessions to a desired folder can be found here.