<?php
/* requires sql.class.php to function */
class Session
{
	private $link;

	/*
	 *	initialize the session
	 */
	public function Session($sql)
	{
		session_start();
		$this->link = $sql;
	}

	/*
	 *	login utils
	 */
	// only needed on registration and password change.
	public function GenerateSalt()
	{
		$salt = uniqid(rand(), true);
		$salt = md5($salt);
		return substr($salt, 0, 8);
	}
	public function GenerateHash($plainText, $salt)
	{
		$hash = $salt . sha1($salt . $plainText);
		return $hash;
	}

	/*
	 *	check if user is logged in
	 */
	public function IsLogged()
	{
		if( !isset($_SESSION['uid']) )
			return false;
		return $this->TestPassword($_SESSION['uid'],$_SESSION['pass']);
	}

	/*
	 * get password/salt for a given user
	 */
	private function GetSalt($uid)
	{
		$uid = mysql_fetch_array($this->link->Query("SELECT salt FROM users WHERE id='?' LIMIT 1", $uid));
		return $uid[0];
	}
	private function GetPassword($uid)
	{
		$password = mysql_fetch_array($this->link->Query("SELECT password FROM users WHERE id='?' LIMIT 1", $uid));
		return $password[0];
	}
	/*
	 *	make sure the stored password matches the given one.
	 */
	private function TestPassword($uid,$password)
	{
		// get password from cookie
		$password = $_SESSION['pass'];

		// get known password
		$knownpass = $this->GetPassword($uid);

		// if this returns false, someone has tampered with the cookie.
		return $password == $knownpass;
	}

	/*
	 *	returns true if successful
	 */
	public function Login()
	{
		// get the uid from the posted password
		$uid = mysql_fetch_array($this->link->Query("SELECT id FROM users WHERE username='?' LIMIT 1",$_POST['username']));
		$uid = $uid[0];

		$password = $_POST['password'];

		$salt = $this->GetSalt($uid);
		$password = $this->GenerateHash($password,$salt);

		$_SESSION['pass'] = $password;

		if( $this->TestPassword($uid, $password) )
		{
			$_SESSION['uid'] = $uid;
			return true;
		}
		// don't leave the password hash there if the login failed (paranoia)
		unset($_SESSION['pass']);
		return false;
	}

	/*
	 *	logout, as if I'm actually doing something.
	 */
	public function Logout() { session_destroy(); }
}


$session = new Session($link); // make sure $link is a database connection, e.g.

// you may wish to change these if you want your site to behave differently!
if( isset($_POST['login']) && !isset($_SESSION['uid']) )
{
	$login = $session->Login();
}
elseif( $_GET['logout'] )
	$session->Logout();