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- require("common.php");
- // This variable will be used to re-display the user's username to them in the
- // login form if they fail to enter the correct password. It is initialized here
- // to an empty value, which will be shown if the user has not submitted the form.
- $submitted_username = '';
- // This if statement checks to determine whether the login form has been submitted
- // If it has, then the login code is run, otherwise the form is displayed
- if(!empty($_GET))
- {
- // This query retreives the user's information from the database using
- // their username.
- $query = "
- SELECT
- id,
- username,
- password,
- salt,
- email
- FROM users
- WHERE
- username = :username
- ";
- // The parameter values
- $query_params = array(
- ':username' => $_GET['username']
- );
- try
- {
- // Execute the query against the database
- $stmt = $db->prepare($query);
- $result = $stmt->execute($query_params);
- }
- catch(PDOException $ex)
- {
- // Note: On a production website, you should not output $ex->getMessage().
- // It may provide an attacker with helpful information about your code.
- die("Failed to run query: " . $ex->getMessage());
- }
- // This variable tells us whether the user has successfully logged in or not.
- // We initialize it to false, assuming they have not.
- // If we determine that they have entered the right details, then we switch it to true.
- $login_ok = false;
- // Retrieve the user data from the database. If $row is false, then the username
- // they entered is not registered.
- $row = $stmt->fetch();
- if($row)
- {
- // Using the password submitted by the user and the salt stored in the database,
- // we now check to see whether the passwords match by hashing the submitted password
- // and comparing it to the hashed version already stored in the database.
- $check_password = hash('sha256', $_GET['password'] . $row['salt']);
- for($round = 0; $round < 65536; $round++)
- {
- $check_password = hash('sha256', $check_password . $row['salt']);
- }
- if($check_password === $row['password'])
- {
- // If they do, then we flip this to true
- $login_ok = true;
- }
- }
- // If the user logged in successfully, then we send them to the private members-only page
- // Otherwise, we display a login failed message and show the login form again
- if($login_ok)
- {
- // Here I am preparing to store the $row array into the $_SESSION by
- // removing the salt and password values from it. Although $_SESSION is
- // stored on the server-side, there is no reason to store sensitive values
- // in it unless you have to. Thus, it is best practice to remove these
- // sensitive values first.
- unset($row['salt']);
- unset($row['password']);
- // This stores the user's data into the session at the index 'user'.
- // We will check this index on the private members-only page to determine whether
- // or not the user is logged in. We can also use it to retrieve
- // the user's details.
- $_SESSION['user'] = $row;
- // Redirect the user to the private members-only page.
- $query = "
- INSERT
- INTO
- 'users' ('time')
- VALUES
- date('Y-m-d')
- ";
- die("1");
- }
- else
- {
- // Tell the user they failed
- print("2");
- // Show them their username again so all they have to do is enter a new
- // password. The use of htmlentities prevents XSS attacks. You should
- // always use htmlentities on user submitted values before displaying them
- // to any users (including the user that submitted them). For more information:
- // http://en.wikipedia.org/wiki/XSS_attack
- $submitted_username = htmlentities($_POST['username'], ENT_QUOTES, 'UTF-8');
- }
- }
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