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Question

im creating a website that requires user authorisation to access some features. im currently working on how a user creates an account and how to utilise sessions to authorise their login. user information is stored in a MySQL table named user which likely includes a reference of username and passwords.

ive been reading up on password hashing/salt for security and wanted the input of some PHP masters, considering im still a rookie to the language.

ive written the following scripts :

define('SALT_LENGTH', 6);

function generateHash($plaintext, $salt==null){
    if($salt == null){
        $salt = substr(md5(uniqid(rand(), true)), 0, SALT_LENGTH);
    }
    else{
        $salt = substr($salt, 0, SALT_LENGTH);
    }

    return $salt . sha1($salt . $plaintext);
}
?>

this is a function included to generate a hash with a salt.

$username = $_POST['username'];
$password = generateHash($_POST['password']);
try{
    $stmt = $pdo->prepare(INSERT INTO user VALUES (:username, :password, :location,     :email, :name);
}catch(PDOException $e){
    echo $e->getMessage();
}
    $stmt->execute(array(':username'=>$username, 
                         ':password'=>$password, 
                         ':location'=>$location, 
                         ':email'=>$email, 
                         ':name'=>$name);

this is the important parts of the script to create an account

if(isset($_POST)){
    //if form was submitted

    $username = $_POST['username'];
    $password = generateHash($_POST['password']);

    session_start();

    $user = 'root';
    $pass = null;
    $pdo = new PDO('mysql:host=localhost; dbname=divebay;', $user, $pass);

    try{
        $stmt = $pdo->prepare('SELECT username FROM user WHERE username =     :username AND password = :password');
        $stmt->execute(array(':username'=>$username,
                             ':password'=>$password);

        if($stmt->fetch(PDO::FETCH_ASSOC)){
            echo 'match';
        }
        else{
            echo 'nomatch';
        }

this is the login session script to lookup users in the database

my main question is does this hashing/salt look like it will work? im confused as to how a hash used to create an encryption in one instance (create acct) will be able to work with a hash created in a different instance. further, is the complexity of what im trying to create appropriate for a relatively simple software project that will likely never be properly deployed?

any other suggestions of where my scripts are wrong will be appreciated also (i need the criticism).

Answer 1

My advice to you is to look for a library/framework that does this for you. Many frameworks will automatically and correctly take care of this kind of thing under the hood for you, often including roles based authorization. Authentication and Authorization aren't immensely difficult to get right, but they're hard enough that you should try to avoid doing it yourself unless you're doing it as a learning exercise.

As for the correctness of your code, I think you need to use the salt matching the stored password on your account name to compare passwords. You should be looking up the password hash for the given username in the database, retrieving the salt from that password hash (which you correctly appended) then using the retrieved salt on the supplied password to get a hash. You then string compare the hash with the stored hash to authenticate.

I don't really know PHP well, but I'm sure that a library exists that will handle this for you.