is my login script vulnerable to sql injection attacks, if yes, what should i do

session_start();

$loginFormAction = $_SERVER['PHP_SELF'];
if (isset($accesscheck)) {
  $GLOBALS['PrevUrl'] = $accesscheck;
  session_register('PrevUrl');
}

if (isset($_POST['user'])) {
  $loginUsername=$_POST['user'];
  $password=$_POST['password'];
  $MM_fldUserAuthorization = "";
  $MM_redirectLoginSuccess = "login.php";
  $MM_redirectLoginFailed = "login.php";
  $MM_redirecttoReferrer = false;
  mysql_select_db($database_mine, $mine);
 
  $LoginRS__query=sprintf("SELECT user_name, password, user_id, role, first_name, last_name, company_id, email FROM user WHERE user_name='%s' AND password='%s'",
    get_magic_quotes_gpc() ? $loginUsername : addslashes($loginUsername), get_magic_quotes_gpc() ? $password : addslashes($password));
   
  $LoginRS = mysql_query($LoginRS__query, $mine) or die(mysql_error());
  $row_LoginRS = mysql_fetch_assoc($LoginRS);
  $loginFoundUser = mysql_num_rows($LoginRS);
  if ($loginFoundUser) {
     $loginStrGroup = "";
   
    //declare two session variables and assign them
    $GLOBALS['MM_Username'] = $loginUsername;
      $GLOBALS['user1'] = $row_LoginRS['user_id'];      
      $GLOBALS['level'] = $row_LoginRS['role'];
      $GLOBALS['name'] = $row_LoginRS['first_name'];      
      $GLOBALS['lname'] = $row_LoginRS['last_name'];
      $GLOBALS['comp'] = $row_LoginRS['company_id'];      
      $GLOBALS['email'] = $row_LoginRS['email'];
      $GLOBALS['MM_UserGroup'] = $loginStrGroup;           

//register the session variables
session_start();
session_register("MM_Username");
session_register('user1');      
session_register('level');
session_register('name');
session_register('lname');
session_register('comp');
session_register('email');
session_register("MM_UserGroup");
$valid_user = 1;

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jblayneyAsked:
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kylealanhaleConnect With a Mentor Commented:
Sorry, small typo; here's a (hopefully) bug free example.  Untested, but the principle is true.  By the way, this checks for a username between 6 and 15 characters long, either a letter or a number, or the character !, @, or #.
if (!preg_match('/^[a-zA-Z\d!@#]{6,15}$/', $username)) die('Invalid username.');

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kylealanhaleCommented:
Well, you do add slashes, that's good.  The only other thing I would suggest would be to put anything (such as those username and password values) through quick regex check to make sure they only have the characters you want.  Something like
if (!preg_match('/[^\w\d!@#]{6,15}$/', $username)) die('Invalid username.');

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jblayneyAuthor Commented:
thank you
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