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Today We Learn : How To Create A Secure Login Using PHP And MYSQL   :P


Within the global media there are instances of websites and data bases being compromised all the time. Keeping sensitive data secure is essential for developers especially if they have a user database, it could be compromised and user’s sensitive data accessed.Here at Codingsec we will now show you how to create a secure login for your website and also how to protect your website against common hacks used frequently today:

SQL Injections
Session Hijacking
Network Eavesdropping
Cross Site Scripting
Brute Force Attacks

In this example you will require PHP 5.3 or later and also MySQL version 4.1.3 or later, you will also need a web server that is configured to use PHP and MySQL. This can be on your own server or one from a web hosting company.Configure serverThe large majority of web hosting companies will already have PHP and MySQL installed and configured. However it is essential to check that the hosting service that you are using has the required versions installed. Keeping both PHP and MySQL software up to date on your server is essential for security.To check the version of PHP and mySQL on your server use the phpinfo(); function.If you have your own server then you should install the required software, installing an XAMPP stack is highly recommended. Below you will find the download link so you cans select the right one for the operating system that you are using.

http://www.apachefriends.org/en/xampp.html

If you are using your server for production purposes then using this method is not recommended.

To configure your server when using Linux download the required packages, for example within Ubuntu:

sudo apt-get install lamp-server^ phpmyadmin

After installing the required components ensure that you secure MySQL with a secure password.

Configure MySQL Database

Log in to your configured server with your Admin/root account.

Now you should create a database named “secure_login”.

You can see how to do this when using Phpmyadmin.

SQL Code:

CREATE DATABASE `secure_login`;

CREATE DATABASE `secure_login`;

Within some hosting areas, doing this within Phpmyadmin is not available so you will need to do this through  cPanel.

Create User with SELECT, UPDATE and INSERT privileges.

To add new users you will need to have full Admin privileges (root).

SQL Code:

CREATE USER ‘sec_user’@’localhost’ IDENTIFIED BY ‘eKcGZr59zAa2BEWU';
GRANT SELECT, INSERT, UPDATE ON `secure_login`.* TO ‘sec_user’@’localhost';

Here are the details of the User that is created using this code:

User: “sec_user”
Password: “eKcGZr59zAa2BEWU”

It is an excellent idea to create a user with a limited amount of privileges so in the worst case scenario of a security breach the hacker would not be able to drop any tables or delete any important data.  When creating your user on your server it is essential to create your own password and not the one displayed within the example.  Here is a useful password generator to create a secure password for the user. For the connection to be established to your server the password within the code and the PHP/SQL database have to be the same.

Create a MySQL table named “members”.

The code below creates a table with five fields (id, username, email, password, salt). We use the CHAR datatype for fields we know the length of, as the fields “password” and “salt” will always be 128 characters long. Using CHAR here saves on processing power:

CREATE TABLE `secure_login`.`members` (
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`username` VARCHAR(30) NOT NULL,
`email` VARCHAR(50) NOT NULL,
`password` CHAR(128) NOT NULL,
`salt` CHAR(128) NOT NULL
) ENGINE = InnoDB;

As we’ve said before, you can do this in whatever type of client you prefer.

Create a table to store login attempts.

We will use this table to store login attempts for a user. This is an effective technique in which will make brute force attacks more difficult:

CREATE TABLE `secure_login`.`login_attempts` (
`user_id` INT(11) NOT NULL,
`time` VARCHAR(30) NOT NULL
) ENGINE=InnoDB

Create a test row in table “members”.

It is extremely significant to always test your code below is a test user to test the database:

Username: test_user
Email: test@example.com
Password: 6ZaxN2Vzm9NUJT2y

SQL Code:

INSERT INTO `secure_login`.`members` VALUES(1, ‘test_user’, ‘test@example.com’,
‘00807432eae173f652f2064bdca1b61b290b52d40e429a7d295d76a71084aa96c0233b82f1feac45529e0726559645acaed6f3ae58a286b9f075916ebf66cacc’,
‘f9aab579fc1b41ed0c44fe4ecdbfcdb4cb99b9023abb241a6db833288f4eea3c02f76e0d35204a8695077dcf81932aa59006423976224be0390395bae152d4ef’);

Create Database Connection Page

Create a global configurations page

Create a folder called “includes” in the root directory of the application and then create a new PHP file in that directory.

Call the file psl-config.php. When working within a production environment you should store this file and all other include files outside of your servers root.

Storing your include files outside of the web server’s  root means that your file cannot be located using a direct URL. Which means if the file was compromised root permissions of the file could not be displayed as text in a browser window.

<?php /** * These are the database login details */ define(“HOST”, “localhost”); // The host you want to connect to. define(“USER”, “sec_user”); // The database username. define(“PASSWORD”, “4Fa98xkHVd2XmnfK”); // The database password. define(“DATABASE”, “secure_login”); // The database name. define(“CAN_REGISTER”, “any”); define(“DEFAULT_ROLE”, “member”); define(“SECURE”, FALSE); // FOR DEVELOPMENT ONLY!!!! ?>

Create the database connection page

This is the PHP code that we will use to connect to the mySQL database.

Create a new PHP file called db_connect.php in the application’s includes directory and add the code below. This code can be added wherever you like:

<?php
include_once ‘psl-config.php';   // As functions.php is not included
$mysqli = new mysqli(HOST, USER, PASSWORD, DATABASE);

Create the PHP Functions

These functions will do all the processing of the login script. Add all of the functions to a page called functions.php in the includes directory of the application.

Securely start a PHP session.

PHP sessions are known not to be secure, therefore it is important not just to put “session_start();” at the top of every page on which you want to use PHP sessions. We are going to create a function called “sec_session_start()”, this will start a PHP session in a secure way. You should call this function at the top of any page in which you wish to access a PHP session variable. If you are really concerned about security and the privacy of your cookies, have a look at this article: Create-a-Secure-Session-Managment-System-in-Php-and-Mysql.This function makes your login script a whole lot more secure. It stops crackers accessing the session id cookie through JavaScript (for example in an XSS attack). Also the “session_regenerate_id()” function, which regenerates the session id on every page reload, helps prevent session hijacking. Note: If you are using HTTPS in your login application set the “$secure” variable to true. In a production environment it is essential that you use HTTPS.Create a new file called functions.php in your application’s includes directory and add the following code to it:<?php
include_once ‘psl-config.php';function sec_session_start() {
$session_name = ‘sec_session_id';   // Set a custom session name
$secure = SECURE;
// This stops JavaScript being able to access the session id.
$httponly = true;
// Forces sessions to only use cookies.
if (ini_set(‘session.use_only_cookies’, 1) === FALSE) {
header(“Location: ../error.php?err=Could not initiate a safe session (ini_set)”);
exit();
}
// Gets current cookies params.
$cookieParams = session_get_cookie_params();
session_set_cookie_params($cookieParams[“lifetime”],
$cookieParams[“path”],
$cookieParams[“domain”],
$secure,
$httponly);
// Sets the session name to the one set above.
session_name($session_name);
session_start();            // Start the PHP session
session_regenerate_id(true);    // regenerated the session, delete the old one.
}Create the Login Function.
This function will check the email and password against the database. It will return true if there is a match. Add this function to your functions.php file:function login($email, $password, $mysqli) {
// Using prepared statements means that SQL injection is not possible.
if ($stmt = $mysqli->prepare(“SELECT id, username, password, salt
FROM members
WHERE email = ?
LIMIT 1″)) {
$stmt->bind_param(‘s’, $email);  // Bind “$email” to parameter.
$stmt->execute();    // Execute the prepared query.
$stmt->store_result();// get variables from result.
$stmt->bind_result($user_id, $username, $db_password, $salt);
$stmt->fetch();// hash the password with the unique salt.
$password = hash(‘sha512′, $password . $salt);
if ($stmt->num_rows == 1) {
// If the user exists we check if the account is locked
// from too many login attemptsif (checkbrute($user_id, $mysqli) == true) {
// Account is locked
// Send an email to user saying their account is locked
return false;
} else {
// Check if the password in the database matches
// the password the user submitted.
if ($db_password == $password) {
// Password is correct!
// Get the user-agent string of the user.
$user_browser = $_SERVER[‘HTTP_USER_AGENT’];
// XSS protection as we might print this value
$user_id = preg_replace(“/[^0-9]+/”, “”, $user_id);
$_SESSION[‘user_id’] = $user_id;
// XSS protection as we might print this value
$username = preg_replace(“/[^a-zA-Z0-9_\-]+/”,
“”,
$username);
$_SESSION[‘username’] = $username;
$_SESSION[‘login_string’] = hash(‘sha512′,
$password . $user_browser);
// Login successful.
return true;
} else {
// Password is not correct
// We record this attempt in the database
$now = time();
$mysqli->query(“INSERT INTO login_attempts(user_id, time)
VALUES (‘$user_id’, ‘$now’)”);
return false;
}
}
} else {
// No user exists.
return false;
}
}
}The Brute Force Function.
Brute force attacks are when a hacker tries thousands of different passwords on an account, either randomly generated passwords or from a dictionary. In our script if a user account has more than five failed logins their account is locked.Brute force attacks are hard to prevent. A few ways we can prevent them are using a CAPTCHA test, locking user accounts and adding a delay on failed logins, so the user cannot login for another thirty seconds.We strongly recommend using a CAPTCHA. As yet we have not implemented this functionality in the example code, but hope to do so in the near future, using SecureImage, since it does not require registration. You may prefer something better known such as reCAPTCHA from Google.Whichever system you decide on, we suggest you only display the CAPTCHA image after two failed login attempts so as to avoid inconveniencing the user unnecessarily.When faced with the problem of brute force attacks, most developers simply block the IP address after a certain amount of failed logins. But there are many tools to automate the process of making attacks like these; and these tools can go through a series of proxies and even change the IP on each request. Blocking all these IP addresses could mean you’re blocking legitimate users as well. In our code we’ll log failed attempts and lock the user’s account after five failed login attempts. This should trigger the sending of an email to the user with a reset link, but we have not implemented this in our code. Here is the code for the checkbrute() function at the time of writing. Add it to your functions.php code:function checkbrute($user_id, $mysqli) {
// Get timestamp of current time
$now = time();// All login attempts are counted from the past 2 hours.
$valid_attempts = $now – (2 * 60 * 60);if ($stmt = $mysqli->prepare(“SELECT time
FROM login_attempts
WHERE user_id = ?
AND time > ‘$valid_attempts'”)) {
$stmt->bind_param(‘i’, $user_id);
// Execute the prepared query.
$stmt->execute();
$stmt->store_result();

// If there have been more than 5 failed logins
if ($stmt->num_rows > 5) {
return true;
} else {
return false;
}
}
}

Check logged in status.

We do this by checking the “user_id” and the “login_string” SESSION variables. The “login_string” SESSION variable has the user’s browser information hashed together with the password. We use the browser information because it is very unlikely that the user will change their browser mid-session. Doing this helps prevent session hijacking. Add this function to your functions.php file in the includes folder of your application:function login_check($mysqli) {
// Check if all session variables are set
if (isset($_SESSION[‘user_id’],
$_SESSION[‘username’],
$_SESSION[‘login_string’])) {$user_id = $_SESSION[‘user_id’];
$login_string = $_SESSION[‘login_string’];
$username = $_SESSION[‘username’];// Get the user-agent string of the user.
$user_browser = $_SERVER[‘HTTP_USER_AGENT’];if ($stmt = $mysqli->prepare(“SELECT password
FROM members
WHERE id = ? LIMIT 1″)) {
// Bind “$user_id” to parameter.
$stmt->bind_param(‘i’, $user_id);
$stmt->execute();   // Execute the prepared query.
$stmt->store_result();if ($stmt->num_rows == 1) {
// If the user exists get variables from result.
$stmt->bind_result($password);
$stmt->fetch();
$login_check = hash(‘sha512′, $password . $user_browser);if ($login_check == $login_string) {
// Logged In!!!!
return true;
} else {
// Not logged in
return false;
}
} else {
// Not logged in
return false;
}
} else {
// Not logged in
return false;
}
} else {
// Not logged in
return false;
}
}Sanitize URL from PHP_SELF
This next function sanitizes the output from the PHP_SELF server variable. It is a modificaton of a function of the same name used by the WordPress Content Management System:
function esc_url($url) {

if (” == $url) {
return $url;
}

$url = preg_replace(‘|[^a-z0-9-~+_.?#=!&;,/:%@$\|*\'()\\x80-\\xff]|i’, ”, $url);

$strip = array(‘%0d’, ‘%0a’, ‘%0D’, ‘%0A’);
$url = (string) $url;

$count = 1;
while ($count) {
$url = str_replace($strip, ”, $url, $count);
}

$url = str_replace(‘;//’, ‘://’, $url);

$url = htmlentities($url);

$url = str_replace(‘&amp;’, ‘&#038;’, $url);
$url = str_replace(“‘”, ‘&#039;’, $url);

if ($url[0] !== ‘/’) {
// We’re only interested in relative links from $_SERVER[‘PHP_SELF’]
return ”;
} else {
return $url;
}
}

The trouble with using the server variable unfiltered is that it can be used in a cross site scripting attack. Most references will simply tell you to filter it using htmlentities(), however even this appears not to be sufficient hence the belt and braces approach in this function.

Others suggest leaving the action attribute of the form blank, or set to a null string. Doing this, though, leaves the form open to an iframe clickjacking attack.

Create Processing Pages

Create the login processing page (process_login.php)

Create a file to process logins, called process_login.php in the application’s includes directory. It goes in this directory because it contains no HTML markup.

We will use the mysqli_* set of PHP functions as this is one of the most up-to-date mySQL extensions.

<?php
include_once ‘db_connect.php';
include_once ‘functions.php';

sec_session_start(); // Our custom secure way of starting a PHP session.

if (isset($_POST[‘email’], $_POST[‘p’])) {
$email = $_POST[‘email’];
$password = $_POST[‘p’]; // The hashed password.

if (login($email, $password, $mysqli) == true) {
// Login success
header(‘Location: ../protected_page.php’);
} else {
// Login failed
header(‘Location: ../index.php?error=1′);
}
} else {
// The correct POST variables were not sent to this page.
echo ‘Invalid Request';
}

Create a logout script.

Your logout script must start the session, destroy it and then redirect to somewhere else. Note: it might be a good idea to add CSRF protection here in case someone sends a link hidden in this page somehow. For more information about CSRF you could visit Coding Horror.

The current code for logging out the user, which you should add to a file called logout.php in the application’s includes directory, is:

<?php
include_once ‘functions.php';
sec_session_start();

// Unset all session values
$_SESSION = array();

// get session parameters
$params = session_get_cookie_params();

// Delete the actual cookie.
setcookie(session_name(),
”, time() – 42000,
$params[“path”],
$params[“domain”],
$params[“secure”],
$params[“httponly”]);

// Destroy session
session_destroy();
header(‘Location: ../index.php’);

Registration Page.

The registration code is included in two new files, called register.php in the application’s root directory and register.inc.php in the includes directory. It does the following things:

Obtains and validates the username the user wishes to adopt
Obtains and validates the user’s email address
Obtains and validates the password the user wants to use
Hashes the password and passes it back to the register.php page (i.e. it posts to itself)

Most of the validation is done in JavaScript, client side. This is because the user has no motivation to circumvent these checks. Why would a user want to create an account that would be less secure than otherwise? We will discuss the JavaScript in the next section.

For now, just create the register.php file and include the following code in it:

<?php
include_once ‘includes/register.inc.php';
include_once ‘includes/functions.php';
?>
<!DOCTYPE html>
<html>
<head>
<meta charset=”UTF-8″>
<title>Secure Login: Registration Form</title>
<script type=”text/JavaScript” src=”js/sha512.js”></script>
<script type=”text/JavaScript” src=”js/forms.js”></script>
<link rel=”stylesheet” href=”styles/main.css” />
</head>
<body>
<!– Registration form to be output if the POST variables are not
set or if the registration script caused an error. –>
<h1>Register with us</h1>
<?php
if (!empty($error_msg)) {
echo $error_msg;
}
?>
<ul>
<li>Usernames may contain only digits, upper and lower case letters and underscores</li>
<li>Emails must have a valid email format</li>
<li>Passwords must be at least 6 characters long</li>
<li>Passwords must contain
<ul>
<li>At least one upper case letter (A..Z)</li>
<li>At least one lower case letter (a..z)</li>
<li>At least one number (0..9)</li>
</ul>
</li>
<li>Your password and confirmation must match exactly</li>
</ul>
<form action=”<?php echo esc_url($_SERVER[‘PHP_SELF’]); ?>”
method=”post”
name=”registration_form”>
Username: <input type=’text’
name=’username’
id=’username’ /><br>
Email: <input type=”text” name=”email” id=”email” /><br>
Password: <input type=”password”
name=”password”
id=”password”/><br>
Confirm password: <input type=”password”
name=”confirmpwd”
id=”confirmpwd” /><br>
<input type=”button”
value=”Register”
onclick=”return regformhash(this.form,
this.form.username,
this.form.email,
this.form.password,
this.form.confirmpwd);” />
</form>
<p>Return to the <a href=”index.php”>login page</a>.</p>
</body>
</html>

The register.inc.php file in the includes directory should contain the following code:

<?php
include_once ‘db_connect.php';
include_once ‘psl-config.php';

$error_msg = “”;

if (isset($_POST[‘username’], $_POST[‘email’], $_POST[‘p’])) {
// Sanitize and validate the data passed in
$username = filter_input(INPUT_POST, ‘username’, FILTER_SANITIZE_STRING);
$email = filter_input(INPUT_POST, ‘email’, FILTER_SANITIZE_EMAIL);
$email = filter_var($email, FILTER_VALIDATE_EMAIL);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
// Not a valid email
$error_msg .= ‘<p class=”error”>The email address you entered is not valid</p>';
}

$password = filter_input(INPUT_POST, ‘p’, FILTER_SANITIZE_STRING);
if (strlen($password) != 128) {
// The hashed pwd should be 128 characters long.
// If it’s not, something really odd has happened
$error_msg .= ‘<p class=”error”>Invalid password configuration.</p>';
}

// Username validity and password validity have been checked client side.
// This should should be adequate as nobody gains any advantage from
// breaking these rules.
//

$prep_stmt = “SELECT id FROM members WHERE email = ? LIMIT 1″;
$stmt = $mysqli->prepare($prep_stmt);

// check existing email
if ($stmt) {
$stmt->bind_param(‘s’, $email);
$stmt->execute();
$stmt->store_result();

if ($stmt->num_rows == 1) {
// A user with this email address already exists
$error_msg .= ‘<p class=”error”>A user with this email address already exists.</p>';
$stmt->close();
}
$stmt->close();
} else {
$error_msg .= ‘<p class=”error”>Database error Line 39</p>';
$stmt->close();
}

// check existing username
$prep_stmt = “SELECT id FROM members WHERE username = ? LIMIT 1″;
$stmt = $mysqli->prepare($prep_stmt);

if ($stmt) {
$stmt->bind_param(‘s’, $username);
$stmt->execute();
$stmt->store_result();

if ($stmt->num_rows == 1) {
// A user with this username already exists
$error_msg .= ‘<p class=”error”>A user with this username already exists</p>';
$stmt->close();
}
$stmt->close();
} else {
$error_msg .= ‘<p class=”error”>Database error line 55</p>';
$stmt->close();
}

// TODO:
// We’ll also have to account for the situation where the user doesn’t have
// rights to do registration, by checking what type of user is attempting to
// perform the operation.

if (empty($error_msg)) {
// Create a random salt
//$random_salt = hash(‘sha512′, uniqid(openssl_random_pseudo_bytes(16), TRUE)); // Did not work
$random_salt = hash(‘sha512′, uniqid(mt_rand(1, mt_getrandmax()), true));

// Create salted password
$password = hash(‘sha512′, $password . $random_salt);

// Insert the new user into the database
if ($insert_stmt = $mysqli->prepare(“INSERT INTO members (username, email, password, salt) VALUES (?, ?, ?, ?)”)) {
$insert_stmt->bind_param(‘ssss’, $username, $email, $password, $random_salt);
// Execute the prepared query.
if (! $insert_stmt->execute()) {
header(‘Location: ../error.php?err=Registration failure: INSERT’);
}
}
header(‘Location: ./register_success.php’);
}
}

If there is no POST data passed into the form, the registration form is displayed. The form’s submit button calls the JavaScript function regformhash(). This function does the necessary validation checks and submits the form when all is well. The JavaScript functions are discussed in the next section.

If the POST data exists, some server side checks are done to sanitise and validate it. NOTE that these checks are not complete at the time of writing. Some of the issues are mentioned in the comments in the file. At present, we just check that the email address is in the correct format, that the hashed password is the correct length and that the user is not trying to register an email that has already been registered.

If everything checks out, the new user is registered by writing a new record into the members table.

 Create Javascript Files

Create sha512.js file

This file is an implementation in JavaScript of the hashing algorithm sha512. We will use the hashing function so our passwords don’t get sent in plain text.

The file can be downloaded from pajhome.org.uk

(It is also saved in the github repository)

Store your copy of this file in a directory called “js”, off the root directory of the application.

Create forms.js file
This file, which you should create in the js directory of the application, will handle the hashing of the passwords for the login (formhash()) and registration (regformhash()) forms:

function formhash(form, password) {
// Create a new element input, this will be our hashed password field.
var p = document.createElement(“input”);

// Add the new element to our form.
form.appendChild(p);
p.name = “p”;
p.type = “hidden”;
p.value = hex_sha512(password.value);

// Make sure the plaintext password doesn’t get sent.
password.value = “”;

// Finally submit the form.
form.submit();
}

function regformhash(form, uid, email, password, conf) {
// Check each field has a value
if (uid.value == ”         ||
email.value == ”     ||
password.value == ”  ||
conf.value == ”) {

alert(‘You must provide all the requested details. Please try again’);
return false;
}

// Check the username

re = /^\w+$/;
if(!re.test(form.username.value)) {
alert(“Username must contain only letters, numbers and underscores. Please try again”);
form.username.focus();
return false;
}

// Check that the password is sufficiently long (min 6 chars)
// The check is duplicated below, but this is included to give more
// specific guidance to the user
if (password.value.length < 6) {
alert(‘Passwords must be at least 6 characters long.  Please try again’);
form.password.focus();
return false;
}

// At least one number, one lowercase and one uppercase letter
// At least six characters

var re = /(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{6,}/;
if (!re.test(password.value)) {
alert(‘Passwords must contain at least one number, one lowercase and one uppercase letter.  Please try again’);
return false;
}

// Check password and confirmation are the same
if (password.value != conf.value) {
alert(‘Your password and confirmation do not match. Please try again’);
form.password.focus();
return false;
}

// Create a new element input, this will be our hashed password field.
var p = document.createElement(“input”);

// Add the new element to our form.
form.appendChild(p);
p.name = “p”;
p.type = “hidden”;
p.value = hex_sha512(password.value);

// Make sure the plaintext password doesn’t get sent.
password.value = “”;
conf.value = “”;

// Finally submit the form.
form.submit();
return true;
}

In both cases, the JavaScript hashes the password and passes it in the POST data by creating and populating a hidden field.
Create HTML Pages

Create the login form (login.php).

This is an HTML form with two text fields, named “email” and “password”. The form’s submit button calls the JavaScript function formhash(), which will generate a hash of the password, and send “email” and “p” (the hashed password) to the server. You should create this file in the application’s root directory.

When logging in, it is best to use something that is not public, for this guide we are using the email as the login id, the username can then be used to identify the user. If the email is not displayed on any pages within the wider application, it adds another unknown for anyone trying to crack the account.

Note: even though we have encrypted the password so it is not sent in plain text, it is essential that you use the HTTPS protocol (TLS/SSL) when sending passwords in a production system. It cannot be stressed enough that simply hashing the password is not enough. A man-in-the-middle attack could be mounted to read the hash being sent and use it to log in.

<?php
include_once ‘includes/db_connect.php';
include_once ‘includes/functions.php';

sec_session_start();

if (login_check($mysqli) == true) {
$logged = ‘in';
} else {
$logged = ‘out';
}
?>
<!DOCTYPE html>
<html>
<head>
<title>Secure Login: Log In</title>
<link rel=”stylesheet” href=”styles/main.css” />
<script type=”text/JavaScript” src=”js/sha512.js”></script>
<script type=”text/JavaScript” src=”js/forms.js”></script>
</head>
<body>
<?php
if (isset($_GET[‘error’])) {
echo ‘<p class=”error”>Error Logging In!</p>';
}
?>
<form action=”includes/process_login.php” method=”post” name=”login_form”>
Email: <input type=”text” name=”email” />
Password: <input type=”password”
name=”password”
id=”password”/>
<input type=”button”
value=”Login”
onclick=”formhash(this.form, this.form.password);” />
</form>
<p>If you don’t have a login, please <a href=”register.php”>register</a></p>
<p>If you are done, please <a href=”includes/logout.php”>log out</a>.</p>
<p>You are currently logged <?php echo $logged ?>.</p>
</body>
</html>

Create the register_success.php page

Create a new PHP web page called register_success.php, in the root directory of the application. This is the page to which the user is redirected after successfully registering. Of course you can make this page anything you like or redirect to another page entirely (or even not at all). It’s up to you. The page should be located in the root directory of the application. The current register_success.php page that we have written looks like this:

<!DOCTYPE html>
<html>
<head>
<meta charset=”UTF-8″>
<title>Secure Login: Registration Success</title>
<link rel=”stylesheet” href=”styles/main.css” />
</head>
<body>
<h1>Registration successful!</h1>
<p>You can now go back to the <a href=”index.php”>login page</a> and log in</p>
</body>
</html>

Create the error page

Create a new HTML page in the root directory of the application. Call it error.php This is the page to which users will be directed if an error occurs during the login or registration process, or when trying to establish a secure session. The code given below simply provides a bare bones error page. You will probably need something a bit more sophisticated. However, please note that the input into the page must be properly filtered to guard against XSS attacks. The example page code is:

<?php
$error = filter_input(INPUT_GET, ‘err’, $filter = FILTER_SANITIZE_STRING);

if (! $error) {
$error = ‘Oops! An unknown error happened.';
}
?>
<!DOCTYPE html>
<html>
<head>
<meta charset=”UTF-8″>
<title>Secure Login: Error</title>
<link rel=”stylesheet” href=”styles/main.css” />
</head>
<body>
<h1>There was a problem</h1>
<p class=”error”><?php echo $error; ?></p>
</body>
</html>

Protecting Pages

Page Protection Script.

One of the most common problems with authentication systems is the developer forgetting to check if the user is logged in. It is very important you use the code below on every protected page to check that the user is logged in. Make sure you use this function to check if the user is logged in.

// Include database connection and functions here.  See 3.1.
sec_session_start();
if(login_check($mysqli) == true) {
// Add your protected page content here!
} else {
echo ‘You are not authorized to access this page, please login.';
}

As an example of what you should do, we have included a sample protected page. Create a file called protected_page.php in the root directory of the application. The file should contain something like the following:

<?php
include_once ‘includes/db_connect.php';
include_once ‘includes/functions.php';

sec_session_start();
?>
<!DOCTYPE html>
<html>
<head>
<meta charset=”UTF-8″>
<title>Secure Login: Protected Page</title>
<link rel=”stylesheet” href=”styles/main.css” />
</head>
<body>
<?php if (login_check($mysqli) == true) : ?>
<p>Welcome <?php echo htmlentities($_SESSION[‘username’]); ?>!</p>
<p>
This is an example protected page.  To access this page, users
must be logged in.  At some stage, we’ll also check the role of
the user, so pages will be able to determine the type of user
authorised to access the page.
</p>
<p>Return to <a href=”index.php”>login page</a></p>
<?php else : ?>
<p>
<span class=”error”>You are not authorized to access this page.</span> Please <a href=”index.php”>login</a>.
</p>
<?php endif; ?>
</body>
</html>

Our application redirects to this page after a successful login. Your own implementation does not have to do this, of course.

Tips
With very few changes these example scripts can be modified to work with other SQL systems such as SQLite or PostgreSQL.
If you’re wanting to use a different hashing algorithm rather than sha512, try Whirlpool. Avoid using Gost, sha1 (Unless thoroughly salted and in multiple iterations), and as already stated, md5. Encourage your users to create strong, unique passwords with both uppercase and lowercase letters, numbers, and symbols. Consider having your users create a separate login name from their username for added security.
Stay away from the md5() function in login scripts, the md5 hashing algorithm is now considered insecure.
Use HTML and CSS to format the login form and output pages to your liking.WarningsThe login page and the Registration page must use HTTPS. The scripts in this article do not force you to do this and, indeed, you may find it easier not to during development. But you should not use these scripts in a production environment unless you are using HTTPS.
The use of a CAPTCHA on the login page is highly recommended to make brute force and DoS attacks more difficult. We recommend that the CAPTCHA appear on the form after two failed login attempts. This is not yet implemented in the example code.
Make sure that the user cannot see your PHP script, which may occur due to an incorrect server setup. There is a possibility of the users gathering information about your database names and passwords if your PHP code is visible. Ideally any scripts that are included in other scripts or pages should be located in a directory outside of the server’s file system and referenced using a relative path e.g. include ‘../../includes/myscript.inc.php’.
You may get a better solution than this by using a framework such as Zend 2, Symfony or CakePHP. All of these frameworks have arrangements for secure sessions and modules to assist with the login process. You may also find you write better applications if you use a framework.
Nothing is 100% secure. Remember to stay in tune with the latest security news to keep improving the security of your scripts.
Centralized sign in solutions exist and are known as Single Sign-On, or SSO. Depending on the need, these may offer superior alternatives to framework sign in solutions since a single login is able to span multiple disparate software applications which may reside on multiple domains. Examples of popular SSO solutions are Barebones SSO, Jasig CAS, and JOSSO.
The Anti Brute Force of this script, that locks a user account, can be misused very easily. We strongly recommend that you use an anti-brute force technique such as a CAPTCHA.