Security

Common attacks include:

  • SQL injections
  • ….

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Chosen Code

Cool

Quick and dirty to sanitize GET and POST arrays. Change RegEx badTags to suite your needs.

/**
 * Sanitize the posted input, located in $_POST or $_GET arrays;
 */
$badTags = array('@<script[^>]*?>.*?</script>@si',
                  '@&#(\d+);@e',
                  '@\[\[(.*?)\]\]@si',
                  '@\[!(.*?)!\]@si',
                  '@\[\~(.*?)\~\]@si',
                  '@\[\((.*?)\)\]@si',
                  '@{{(.*?)}}@si',
                  '@\[\*(.*?)\*\]@si');
foreach($_POST as $key => $value) {
  $_POST[$key] = preg_replace($badTags, "", $value);
}
foreach($_GET as $key => $value) {
  $_GET[$key] = preg_replace($badTags, "", $value);
}

More comprehensive solution

<?
///////////////////////////////////////
// sanitize.inc.php
// Sanitization functions for PHP
// by: Gavin Zuchlinski, Jamie Pratt, Hokkaido
// webpage: http://libox.net
// Last modified: September 27, 2003
//
// Many thanks to those on the webappsec list for helping me improve these functions
///////////////////////////////////////
// Function list:
// sanitize_paranoid_string($string) -- input string, returns string stripped of all non
//           alphanumeric
// sanitize_system_string($string) -- input string, returns string stripped of special
//           characters
// sanitize_sql_string($string) -- input string, returns string with slashed out quotes
// sanitize_html_string($string) -- input string, returns string with html replacements
//           for special characters
// sanitize_int($integer) -- input integer, returns ONLY the integer (no extraneous
//           characters
// sanitize_float($float) -- input float, returns ONLY the float (no extraneous
//           characters)
// sanitize($input, $flags) -- input any variable, performs sanitization
//           functions specified in flags. flags can be bitwise
//           combination of PARANOID, SQL, SYSTEM, HTML, INT, FLOAT, LDAP,
//           UTF8
///////////////////////////////////////
define("PARANOID", 1);
define("SQL", 2);
define("SYSTEM", 4);
define("HTML", 8);
define("INT", 16);
define("FLOAT", 32);
define("LDAP", 64);
define("UTF8", 128);
 
// internal function for utf8 decoding
// thanks to Jamie Pratt for noticing that PHP's function is a little
// screwy
function my_utf8_decode($string)
{
return strtr($string,
  "???????¥µ????????????????????????????????????????????????????????????",
  "SOZsozYYuAAAAAAACEEEEIIIIDNOOOOOOUUUUYsaaaaaaaceeeeiiiionoooooouuuuyy");
}
 
// paranoid sanitization -- only let the alphanumeric set through
function sanitize_paranoid_string($string, $min='', $max='')
{
  $string = preg_replace("/[^a-zA-Z0-9]/", "", $string);
  $len = strlen($string);
  if((($min != '') && ($len < $min)) || (($max != '') && ($len > $max)))
    return FALSE;
  return $string;
}
 
// sanitize a string in prep for passing a single argument to system() (or similar)
function sanitize_system_string($string, $min='', $max='')
{
  $pattern = '/(;|\||`|>|<|&|^|"|'."\n|\r|'".'|{|}|[|]|\)|\()/i'; // no piping, passing possible environment variables ($),
                           // seperate commands, nested execution, file redirection,
                           // background processing, special commands (backspace, etc.), quotes
                           // newlines, or some other special characters
  $string = preg_replace($pattern, '', $string);
  $string = '"'.preg_replace('/\$/', '\\\$', $string).'"'; //make sure this is only interpretted as ONE argument
  $len = strlen($string);
  if((($min != '') && ($len < $min)) || (($max != '') && ($len > $max)))
    return FALSE;
  return $string;
}
 
// sanitize a string for SQL input (simple slash out quotes and slashes)
function sanitize_sql_string($string, $min='', $max='')
{
  $pattern[0] = '/(\\\\)/';
  $pattern[1] = "/\"/";
  $pattern[2] = "/'/";
  $replacement[0] = '\\\\\\';
  $replacement[1] = '\"';
  $replacement[2] = "\\'";
  $len = strlen($string);
  if((($min != '') && ($len < $min)) || (($max != '') && ($len > $max)))
    return FALSE;
  return preg_replace($pattern, $replacement, $string);
}
 
// sanitize a string for SQL input (simple slash out quotes and slashes)
function sanitize_ldap_string($string, $min='', $max='')
{
  $pattern = '/(\)|\(|\||&)/';
  $len = strlen($string);
  if((($min != '') && ($len < $min)) || (($max != '') && ($len > $max)))
    return FALSE;
  return preg_replace($pattern, '', $string);
}
 
 
// sanitize a string for HTML (make sure nothing gets interpretted!)
function sanitize_html_string($string)
{
  $pattern[0] = '/\&/';
  $pattern[1] = '/</';
  $pattern[2] = "/>/";
  $pattern[3] = '/\n/';
  $pattern[4] = '/"/';
  $pattern[5] = "/'/";
  $pattern[6] = "/%/";
  $pattern[7] = '/\(/';
  $pattern[8] = '/\)/';
  $pattern[9] = '/\+/';
  $pattern[10] = '/-/';
  $replacement[0] = '&amp;';
  $replacement[1] = '&lt;';
  $replacement[2] = '&gt;';
  $replacement[3] = '<br>';
  $replacement[4] = '&quot;';
  $replacement[5] = '&#39;';
  $replacement[6] = '&#37;';
  $replacement[7] = '&#40;';
  $replacement[8] = '&#41;';
  $replacement[9] = '&#43;';
  $replacement[10] = '&#45;';
  return preg_replace($pattern, $replacement, $string);
}
 
// make int int!
function sanitize_int($integer, $min='', $max='')
{
  $int = intval($integer);
  if((($min != '') && ($int < $min)) || (($max != '') && ($int > $max)))
    return FALSE;
  return $int;
}
 
// make float float!
function sanitize_float($float, $min='', $max='')
{
  $float = floatval($float);
  if((($min != '') && ($float < $min)) || (($max != '') && ($float > $max)))
    return FALSE;
  return $float;
}
 
// glue together all the other functions
function sanitize($input, $flags, $min='', $max='')
{
  if($flags & UTF8) $input = my_utf8_decode($input);
  if($flags & PARANOID) $input = sanitize_paranoid_string($input, $min, $max);
  if($flags & INT) $input = sanitize_int($input, $min, $max);
  if($flags & FLOAT) $input = sanitize_float($input, $min, $max);
  if($flags & HTML) $input = sanitize_html_string($input, $min, $max);
  if($flags & SQL) $input = sanitize_sql_string($input, $min, $max);
  if($flags & LDAP) $input = sanitize_ldap_string($input, $min, $max);
  if($flags & SYSTEM) $input = sanitize_system_string($input, $min, $max);
  return $input;
}
 
?>

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