Question

I’m doing some maintenance on a clients website that uses the simple mysql_query() function for all of their database queries. On one of their pages, a query is done to pull user information based on their nickname. The file is very robust and going through and changing every instance to pull from user IDs instead of nicknames is not really feasible.

They’re running into problems with some nicknames, particularly “Link”, “Echo”, “Slayer”. I see why link and echo could potentially cause issues with the query, but not so much Slayer. Is there anything I can do (aside from preventing creation of these names in the future) to help the query go through and pull the information I need?

Edit:
The whole function:

function userInfo($username){
    global $username_array;
    $username = prepare($username);
    $username_array = mysql_fetch_array(mysql_query("SELECT * FROM `users` WHERE `name` = '$username' LIMIT 1"));
}

It should return an array $username_array back to the original script. With 99% of users, this works fine. For some reason, the users above, this done not work.

function prepare($val,$type=0){
$val = XSS($val);
$val = sqlInjection($val);
return $val;

}

function XSS($val) {
   // remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
   $val = preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x20])/', '', $val);

   // straight replacements, the user should never need these since they're normal characters
   // this prevents like <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&#X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
   $search = 'abcdefghijklmnopqrstuvwxyz';
   $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
   $search .= '1234567890!@#$%^&*()';
   $search .= '~`";:?+/={}[]-_|\'\\';
   for ($i = 0; $i < strlen($search); $i++) {
      // ;? matches the ;, which is optional
      // 0{0,7} matches any padded zeros, which are optional and go up to 8 chars
      // &#x0040 @ search for the hex values
      $val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); // with a ;
      // &#00064 @ 0{0,7} matches '0' zero to seven times
      $val = preg_replace('/(&#0{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ;
   }

   // now the only remaining whitespace attacks are \t, \n, and \r
   $ra1 = Array('javascript', 'vbscript', 'expression', 'applet', 'blink', 'script', 'iframe', 'frameset', 'ilayer', 'bgsound');
   $ra2 = Array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload');
   $ra = array_merge($ra1, $ra2);

   $found = true; // keep replacing as long as the previous round replaced something
   while ($found == true) {
      $val_before = $val;
      for ($i = 0; $i < sizeof($ra); $i++) {
         $pattern = '/';
         for ($j = 0; $j < strlen($ra[$i]); $j++) {
            if ($j > 0) {
               $pattern .= '(';
               $pattern .= '(&#[x|X]0{0,8}([9][a][b]);?)?';
               $pattern .= '|(&#0{0,8}([9][10][13]);?)?';
               $pattern .= ')?';
            }
            $pattern .= $ra[$i][$j];
         }
         $pattern .= '/i';
         $replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag
         $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags
         if ($val_before == $val) {
            // no replacements were made, so exit the loop
            $found = false;
         }
      }
   }
   return $val;
}

function sqlInjection($val){
  if (get_magic_quotes_gpc()){
    $val = stripslashes($val);
  }
  if(version_compare(phpversion(),"4.3.0") == "-1"){
    return mysql_escape_string($val);
  }else{
    return mysql_real_escape_string($val);
  }
}

Answer 1

There should be no problem since no user input should ever be directly executed.

Make sure you escape the strings properly and consider using prepared statements incase someone has a nasty suprise waiting such as this.