How to authenticate securely by session tokens and cookies? updated - php

Question

I tried to write my own authentication method (school project), and I'm stuck.
Please advise, how to solve a secure authentication:
There is an index.php which contains everything that needs to be "protected". I will copy the relevant parts of my code here.
updated index.php
session_start();
function checkUserAuth(){
$authStatus = false;
if (isset($_SESSION['PHPSESSID'])){
if ($_SESSION['PHPSESSID'] == $_COOKIE['PHPSESSID']){
$authStatus = true;
}
}
return $authStatus;
}
if(!checkUserAuth()){
include_once(dirname(__DIR__).'/admin/authentication/login.php');
exit();
}
If the checkUserAuth() determines, that there is no properly authenticated user, will include the login.php and stop the rest of the script.
updated login.php:
if(array_key_exists($username, $users) && password_verify($password, $users[$username])){
$_SESSION['PHPSESSID'] = $_COOKIE['PHPSESSID'];
$_SESSION['login_user'] = $_POST['user'];
What I imagine that might happen, is that if the login details are correct, the login.php sets a cookie, and refreshes the page. Then the index.php will detect the cookie, and skip the login part.
The login is pretty much figured out, and thanks to Juned, I think it is working now. However I don't know how secure is this?
On a scale from 1 to very, how wrong I am?

Answer 1

There are loads of ways of doing this. The below pseudocode is not the most efficient but should work and I don't think what you've done above will actually work.
Does this help?
login.php pseudocode
<?php
session_start(); // this function checks if there's a session ID already set, if not, sets one.
if(array_key_exists($username, $users) && password_verify($password, $users[$username])){
// do your login details checking here
// if login details correct
// set a flag in the $_SESSION superglobal and whatever else you want to store about the user like their username e.g.
$_SESSION["loggedIn"] = true;
$_SESSION["username"] = "$_POST['user']"; // better practice to fetch a clean version from your database
//else return user to login page
}
?>
index.php pseudocode
<?php
session_start(); // this will fetch the session ID and other variables that you might have set e.g. username, logged in status
function checkUserAuth(){
$authStatus = false;
if (isset($_SESSION['loggedIn']) && $_SESSION['loggedIn'] === true){
$authStatus = true;
}
return $authStatus;
}
if(!checkUserAuth()){
// redirect to login page. e.g.
header('Location: login.php');
exit;
}
?>