authentication query in two table? - php

Question

my website has separate tables for users and admin
now i want to give the privilege to access admin area to some users
my problem is with admin and users table
i dont know if i should copy authentication data from user table to the admin table so they can login in to the admin are , or perform a query to search both tables for username and password and just use level column to verify their access?
something like this ?
$sql = "select `password` , `level` from `admin` where `username` = '$username' UNION
(SELECT `password` , `level` FROM `users` where `username` = '$username') LIMIT 1 ";
$result = $db->query($sql);
while($row = mysql_fetch_assoc($result)){
if($password == $row['passwor'] && $row['level'] != 0)
echo 'welcom to admin area';
else
echo 'login faild';
}

Answer 1

I see you are storing passwords in the clear in your database.
This is a major security risk and should never be done.
Passwords should always be stored as salted hashes using a secure hash function.
I also fail to see the use for separate tables for admins and non-admins.
I recommend you alter your table layout.
table user
-------------
id unsigned integer auto_increment primary key,
username varchar(100) not null,
salt varchar(20) not null,
passhash varchar(48) not null,
isadmin boolean not null default false
Query your table with:
SELECT u.id, u.isadmin FROM user u
WHERE u.username = '$username'
AND passhash = SHA2(CONCAT(u.salt, '$password'),512)
AND isadmin = 1
When creating a user use:
INSERT INTO user (username, salt, passhash, isadmin)
VALUES ('$username', '$salt', SHA2(CONCAT('$salt','$password'),512), '$isadmin')

Answer 2

You may use LEFT JOIN and no need for a loop :
$sql = 'SELECT `a`.`password`, `a`.`level` FROM `admin` AS `a` LEFT JOIN `users` ON `a`.`username` = `u`.`username` WHERE `a`.`username` = "'.$username.'" LIMIT 1';
$result = $db->query($sql);
$row = mysql_fetch_assoc($result);
if($password == $row['passwor'] && $row['level'] != 0)
echo 'welcom to admin area';
else
echo 'login faild';
But you should create a field in your users table and use an int to give rights like :
0 is a user, 1 is a super user, 2 moderator and 3 admin... this is an example. Then you use DEFINE in PHP to setup your class. Also, encode your password. I recommend SHA-512.