php sessions to authenticate user on login form

Question

I have the following code designed to begin a session and store username/password data, and if nothing is submitted, or no session data stored, redirect to a fail page.

session_start();
if(isset($_POST['username']) || isset($_POST['password'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];
    $_SESSION['username'] = $username;
    $_SESSION['password'] = $password;
}

if(isset($_SESSION['username']) || isset($_SESSION['password'])){
    $navbar = "1";
    $logindisplay = "0";
    $username = $_SESSION['username'];
    $password = $_SESSION['password'];
} else {
    header('Location:http://website.com/fail.php');
}

$authed = auth($username, $password);
if( $authed == "0" ){
    header('Location:http://website.com/fail.php');
}

Its not working the way it should and is redirecting me to fail even though i submitted my info and stored it in the session. Am i doing something wrong?

NOTE the authed function worked fine before i added the session code.

Answer 1

what about using this to setup session

session_start();
if( isset($_POST['username']) && isset($_POST['password']) )
{
    if( auth($_POST['username'], $_POST['password']) )
    {
        // auth okay, setup session
        $_SESSION['user'] = $_POST['username'];
        // redirect to required page
        header( "Location: index.php" );
     } else {
        // didn't auth go back to loginform
        header( "Location: loginform.html" );
     }
 } else {
     // username and password not given so go back to login
     header( "Location: loginform.html" );
 }

and at the top of each "secure" page use this code:

session_start();
session_regenerate_id();
if(!isset($_SESSION['user']))      // if there is no valid session
{
    header("Location: loginform.html");
}

this keeps a very small amount of code at the top of each page instead of running the full auth at the top of every page. To logout of the session:

session_start();
unset($_SESSION['user']);
session_destroy();
header("Location: loginform.html");

Answer 2

First, don't store the password in the session. It's a bad thing. Second, don't store the username in the session until after you have authenticated.

Try the following:

<?php

session_start();

if (isset($_POST['username']) && isset($_POST['password'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];
    $authed = auth($username, $password);

    if (! $authed) {
        header('Location: http://website.com/fail.php');
    } else {
        $_SESSION['username'] = $username;
    }
}

if (isset($_SESSION['username'])) {
    $navbar = 1;
    $logindisplay = 0;
} else {
    header ('Location: http://website.com/fail.php');
}