Question

I wrote a function in PHP to check username and password from MySQL database and store as session after successful validation. But whatever value I enter to the input box it approves it and made a successful login. My Login code doesn’t work

here it is

function queryByUserAndPass($tableName, $username, $password){
    $queryStatement = "SELECT * FROM ".$tableName." WHERE username='".$username."' 
                      AND password='".$password."' LIMIT 1";
    return $queryStatement;
}

function checkLogIn() {

    if(isset($_POST['submit'])){
        $username = $_POST['username'];
        $password = $_POST['password'];
        $queryState = queryByUserAndPass("nepal_users", $username, $password);
        if( $resultQuery = mysql_query($queryState) ){
            $found_user= mysql_fetch_array($resultQuery);
            $_SESSION['id']=$found_user['id'];
            $_SESSION['username']=$found_user['username'];
            $message="succesful log in ".$_SESSION['username'];
            header("location:home.php");
            exit;
        }else {
            $message="error in log in";
        }    

    }

}

Please tell me what is wrong in this code and why it is not working.

Answer 1

you dont check if username and password are correct!

    if( $resultQuery = mysql_query($queryState) ){
        $found_user = mysql_fetch_array($resultQuery);
        if ($username === $found_user['username'] &&
          $password === $found_user['password']) {
            $_SESSION['id']=$found_user['id'];
            $_SESSION['username']=$found_user['username'];
            $message="succesful log in ".$_SESSION['username'];
            header("Location: home.php");
            exit;
        } else {
            echo "wrong username or password";
        }
    }else {
        $message="error from database: " . mysql_errno($resultQuery);
    }

IMPORTANT NOTE

The code above just illustrates where the logic problem in your code is. There are two other serious issues in it:

1. Its vulnerable to SQL injection. Using prepared statements is common practise. If prepared statemements are not availabe to you, use something like $SAFE_USER_DATA = array_map('mysql_real_escape_string', $_POST); and use this instead of directly reading $_POSTdata. That way you ensure no malicious user can modify your SQL statements to gain access to your system.

2. You should never store passwords as plain text – storing a salted SHA1 password hash is encouraged. do NOT simply use md5($password). Attackers can easily decrypt those with the help of rainbow tables