how to get admin access on certain pages - php

Question

I have created a website that has a basic registration and login system, I have pages that I only want admins to access.
My database for the accounts has a role column with 1 user assigned as admin and the other assigned as user
AUTHENTICATE.PHP
<?php
session_start();
// Change this to your connection info.
$DATABASE_HOST = 'localhost';
$DATABASE_USER = 'root';
$DATABASE_PASS = '';
$DATABASE_NAME = 'feedbackdb';
// Try and connect using the info above.
$con = mysqli_connect($DATABASE_HOST, $DATABASE_USER, $DATABASE_PASS, $DATABASE_NAME);
if ( mysqli_connect_errno() ) {
// If there is an error with the connection, stop the script and display the error.
exit('Failed to connect to MySQL: ' . mysqli_connect_error());
}
// Now we check if the data from the login form was submitted, isset() will check if the data exists.
if ( !isset($_POST['username'], $_POST['password']) ) {
// Could not get the data that should have been sent.
exit('Please fill both the username and password fields!');
}
// Prepare our SQL, preparing the SQL statement will prevent SQL injection.
if ($stmt = $con->prepare('SELECT id, password FROM accounts WHERE username = ?')) {
// Bind parameters (s = string, i = int, b = blob, etc), in our case the username is a string so we use "s"
$stmt->bind_param('s', $_POST['username']);
$stmt->execute();
// Store the result so we can check if the account exists in the database.
$stmt->store_result();
if ($stmt->num_rows > 0) {
$stmt->bind_result($id, $password);
$stmt->fetch();
// Account exists, now we verify the password.
// Note: remember to use password_hash in your registration file to store the hashed passwords.
if (password_verify($_POST['password'], $password)) {
// Verification success! User has loggedin!
// Create sessions so we know the user is logged in, they basically act like cookies but remember the data on the server.
session_regenerate_id();
$_SESSION['loggedin'] = TRUE;
$_SESSION['name'] = $_POST['username'];
$_SESSION['id'] = $id;
$_SESSION['admin'] = true/false;
header('location: home.php');
} else {
echo 'Incorrect password!';
}
} else {
echo 'Incorrect username!';
}
$stmt->close();
}
?>
And what I use to check:
<?php
session_start();
if(isset($_SESSION['admin'], $_SESSION['admin'])){
header('Location: index.php');
exit;
}
?>
that's the code I'm using in the page,
the problem I have is it doesn't matter who I log in as it always redirects, whereas I want the page to be accessible for admins but not users.

Answer 1

First, you need to alter your query to return the role column.
if ($stmt = $con->prepare('SELECT id, password, role FROM accounts WHERE username = ?'))
Next, you need to bind that value the same way you do $id and $password.
$stmt->bind_result($id, $password, $role);
Next, inside of your password_verify() block where you assign the other $_SESSION variables, set a role variable.
$_SESSION['loggedin'] = TRUE;
$_SESSION['name'] = $_POST['username'];
$_SESSION['id'] = $id;
$_SESSION['role'] = $role;
Now, on any page you want, you can block access to anyone who isn't an admin.
if(empty($_SESSION['role']) || $_SESSION['role'] !== 'admin') {
//block user access
die("You do not have permission to view this page.");
}
If you want to show something on a page which is only visible to admins without blocking all users from the page entirely, you could do
if(!empty($_SESSION['role']) && $_SESSION['role'] == 'admin') {
echo "Only admins can see this text.";
}
Variable Cleanup
I recommend instead of creating multiple different session variable, you create a single user session variable containing an array of data you may need. I recommend this because it is cleaner, easier to manage, and easier to use later in your code.
Basically, replace all of your $_SESSION variable declarations with this:
$_SESSION['user'] = [
'loggedin' => true,
'name' => $_POST['username'],
'id' => $id,
'role' => $role
];
Then, to check if the user is an admin you would do something like this:
if(empty($_SESSION['user']) || $_SESSION['user']['role'] !== 'admin') {
//block user access
die("You do not have permission to view this page.");
}
And to show something for only admins without blocking all users from the page entirely:
if(!empty($_SESSION['user']) && $_SESSION['user']['role'] == 'admin') {
echo "Only admins can see this text.";
}
NOTE: Using MySQL Root user for website DB access is extremely unwise
and unsafe. Don't do it. Make a specific MySQL user only with limited
permissions on that data that they require
from Martin in the
comments.