Reportando errores
It would make this whole issue a lot less confusing for less-experienced PHP programmers if you just explained:
- $myVariable no longer works by default
- $_GET['myVariable'] works just fine
I'm embarrassed to say it's taken me six months since my ISP upgraded to PHP5 figure this out. I've completely rewritten scripts to stop using GET variables altogether.
I'm dumb.
Usando Register Globals
Advertencia
Esta característica ha sido declarada OBSOLETA desde PHP 5.3.0 y ELIMINADA a partir de PHP 5.4.0.
Quizás el cambio más controversial en PHP fue cuando el valor predeterminado para la directiva de PHP register_globals pasó de ON a OFF en PHP » 4.2.0. La dependencia sobre esta directiva era bastante común y muchas personas ni siquiera sabía que existía y asumían sólo que ese era el modo como PHP funcionaba. Esta página explicará cómo se puede escribir código inseguro con esta directiva, pero tenga en cuenta que la directiva en si misma no es insegura sino el uso inapropiado de ella.
Cuando está activada, register_globals inyectará los scripts con todo tipo de variables, como las de peticiones provenientes de formularios HTML. Esto, unido al hecho de que PHP no requiere la inicialización de variables, significa que es muy fácil escribir código inseguro. Fue una decisión difícil, pero la comunidad de PHP decidió desactivar esta directiva por defecto. Cuando está activada, las personas usan variables que en realidad no se sabe a ciencia cierta de dónde provienen y solo queda asumir. Las variables internas que son definidas en el script mismo son mezcladas con los datos requeridos enviados por los usuarios y al deshabilitar register_globals se cambia esto. Vamos a demostrar con un ejemplo del uso incorrecto de register_globals:
Ejemplo #1 Ejemplo de uso incorrecto con register_globals = on
<?php
// $authorized = true Se define sólo si el usuario está autenticado
if (authenticated_user()) {
$authorized = true;
}
// Debido a que no se inicializa $authorized como false, esta podría ser
// definida a través de register_globals, como desde GET auth.php?authorized=1
// ¡Por lo tanto, cualquier persona puede verse como autenticada!
if ($authorized) {
include "/highly/sensitive/data.php";
}
?>
Cuando está register_globals = on, la lógica anterior podría verse comprometida. Cuando está deshabilitada, $authorized no puede definirse a través de peticiones, así que estará bien, aunque realmente en general es una buena práctica de programación inicializar las variables primero. Por ejemplo, en el ejemplo anterior se puede haber realizado primero algo como $authorized = false. Hacer esto primero significa que el código anterior podría funcionar con register_globals activado o desactivado ya que los usuarios de forma predeterminada no serían autorizados.
Otro ejemplo es aquel de las sesiones. Cuando está register_globals = on, se puede usar también $username en el siguiente ejemplo, pero nuevamente se debe notar que $username también puede provenir de otros medios, tal como GET (a través de la URL).
Ejemplo #2 Ejemplo de uso de sesiones con register_globals on u off
<?php
// No se sabría por dónde proviene $username, pero se sabe que $_SESSION es
// para datos de sesión.
if (isset($_SESSION['username'])) {
echo "Hello <b>{$_SESSION['username']}</b>";
} else {
echo "Hello <b>Guest</b><br />";
echo "Would you like to login?";
}
?>
Incluso es posible tomar medidas preventivas para advertir cuando se haga un intento de falsificación. Si se sabe previamente con exactitud el lugar de donde una variable debería provenir, se puede verificar si los datos enviados provienen de una clase inapropiada de sumisión. Si bien no garantiza que los datos no han sido falsificados, esto requiere que un atacante adivine el medio apropiado para falsificar. Si no importa de donde provienen los datos requeridos, se puede usar $_REQUEST ya que contiene una mezcla de datos GET, POST y COOKIE. Ver también la sección del manual sobre el uso de variables desde fuentes externas sources.
Ejemplo #3 Detección de envenenamiento simple de variables
<?php
if (isset($_COOKIE['MAGIC_COOKIE'])) {
// MAGIC_COOKIE viene de una cookie.
// ¡Asegúrese de validar la información de la cookie!
} elseif (isset($_GET['MAGIC_COOKIE']) || isset($_POST['MAGIC_COOKIE'])) {
mail("admin@example.com", "Posible intento de ataque", $_SERVER['REMOTE_ADDR']);
echo "Violación de seguridad, el administrador ha sido alertado.";
exit;
} else {
// MAGIC_COOKIE no se establece a través de este REQUEST
}
?>
Por supuesto, simplemente deshabilitar register_globals no quiere decir que su código
es seguro. Cada pieza de datos que es remitida, también debe ser
verificada de otras formas. ¡Siempre valide los datos de los usuarios e inicialice
sus variables! Para chequear por variables no inicializadas, se puede usar
error_reporting() para mostrar
errores de nivel E_NOTICE.
Para obtener información sobre la emulación de register_globals activado o desactivado, consulte este FAQ.
Nota: Nota de disponibilidad de Superglobals
Los arrays Superglobal como $_GET, $_POST y $_SERVER, etc. están disponibles desde PHP 4.1.0. Para más información, lea la sección del manual en superglobals
add a note
User Contributed Notes
Usando Register Globals - [13 notes]
lester burlap ¶
4 years ago
claude dot pache at gmail dot com ¶
4 years ago
Beware that all the solutions given in the comments below for emulating register_global being off are bogus, because they can destroy predefined variables you should not unset. For example, suppose that you have
<?php $_GET['_COOKIE'] == 'foo'; ?>
Then the simplistic solutions of the previous comments let you lose all the cookies registered in the superglobal "$_COOKIE"! (Note that in this situation, even with register_global set to "on", PHP is smart enough to not mess predefined variables such as $_COOKIE.)
A proper solution for emulating register_global being off is given in the FAQ, as stated in the documentation above.
moore at hs-furtwangen dot de ¶
4 years ago
I had a look at the post from Dice, in which he suggested the function unregister_globals(). It didn't seem to work - only tested php 4.4.8 and 5.2.1 - so I made some tweaking to get it running. (I had to use $GLOBALS due to the fact that $$name won't work with superglobals).
<?php
//Undo register_globals
function unregister_globals() {
if (ini_get('register_globals')) {
$array = array('_REQUEST', '_FILES');
foreach ($array as $value) {
if(isset($GLOBALS[$value])){
foreach ($GLOBALS[$value] as $key => $var) {
if (isset($GLOBALS[$key]) && $var === $GLOBALS[$key]) {
//echo 'found '.$key.' = '.$var.' in $'.$value."\n";
unset($GLOBALS[$key]);
}
}
}
}
}
}
?>
The echo was for debuging, thought it might come in handy.
Dice ¶
5 years ago
To expand on the nice bit of code Mike Willbanks wrote and Alexander tidied up, I turned the whole thing in a function that removes all the globals added by register_globals so it can be implemented in an included functions.php and doesn't litter the main pages too much.
<?php
//Undo register_globals
function unregister_globals() {
if (ini_get(register_globals)) {
$array = array('_REQUEST', '_SESSION', '_SERVER', '_ENV', '_FILES');
foreach ($array as $value) {
foreach ($GLOBALS[$value] as $key => $var) {
if ($var === $GLOBALS[$key]) {
unset($GLOBALS[$key]);
}
}
}
}
}
?>
Ruquay K Calloway ¶
5 years ago
While we all appreciate the many helpful posts to get rid of register_globals, maybe you're one of those who just loves it. More likely, your boss says you just have to live with it because he thinks it's a great feature.
No problem, just call (below defined):
<?php register_globals(); ?>
anywhere, as often as you want. Or update your scripts!
<?php
/**
* function to emulate the register_globals setting in PHP
* for all of those diehard fans of possibly harmful PHP settings :-)
* @author Ruquay K Calloway
* @param string $order order in which to register the globals, e.g. 'egpcs' for default
*/
function register_globals($order = 'egpcs')
{
// define a subroutine
if(!function_exists('register_global_array'))
{
function register_global_array(array $superglobal)
{
foreach($superglobal as $varname => $value)
{
global $$varname;
$$varname = $value;
}
}
}
$order = explode("\r\n", trim(chunk_split($order, 1)));
foreach($order as $k)
{
switch(strtolower($k))
{
case 'e': register_global_array($_ENV); break;
case 'g': register_global_array($_GET); break;
case 'p': register_global_array($_POST); break;
case 'c': register_global_array($_COOKIE); break;
case 's': register_global_array($_SERVER); break;
}
}
}
?>
fab dot mariotti at [google]gmail dot com ¶
5 years ago
For my application I defined two functions:
wit_set_gv('space','key','value')
wit_get_gv('space','key')
Forgive the "wit_" prefix but the gv stays for Global Variable.
Maybe I should start with a simple version:
wit_set_gv('key','value')
wit_get_gv('key')
This way you would set or get a global/session value.
The register_globals (on or off), session state and/or
superglobal variables will be handled by these functions.
I did add a 'space' item because I wanted to have control
on what goes to/comes from where. As an example if I call:
wit_get_gv('WIT_CONF','URL')
I know that I have to check for a global variable named
WIT_CONF which also gives me a positive responce
on isset($WIT_CONF['URL']). In this case $WIT_CONF
is global and static. But I can also set up a $WIT_STATE
variable which will represent the state of the transaction.
Using the code of WIT_set_gv() and WIT_get_gv(), with the help
of a simple few lines (in my case: include globals.inc.php)
definition script I handle this problem.
In my case, for example, if 'WIT_STATE' (or other names)
is not a defined globally available variable I default to check
for a session variable.
For example you might warn or stop if a requested named variable
matches a $_POST, $_GET or $_SESSION variable name while you
do not expect so. i.e. all my private data has a wit_ prefix
but no public request has (shouldn't have) this prefix.
Oopss. I do realize that this comment might not be in the proper
place. i.e. "register_globals". Indeed it might give some advice
to users still using register_globals and willing to change the
code for a "better" solution. Of course the simple switching to "register_globals = off" might not solve
the securities issues.
Cheers
F
Tumasch ¶
5 years ago
In addition to Mike Willbanks post:
Put this to the beginning of every file or to a functions.inc.php and call it every time before start working with user variables.
This will prevent problems with wrong initalized variables or users who try to break your application.
And this has an extra bonus: Applications which still work are also register_globasl = off enabled!
<?php
//
// If register_globals is on, delete all variables exept the ones in the array
//
if (ini_get('register_globals')) {
foreach ($GLOBALS as $int_temp_name => $int_temp_value) {
if (!in_array($int_temp_name, array (
'GLOBALS',
'_FILES',
'_REQUEST',
'_COOKIE',
'_SERVER',
'_ENV',
'_SESSION',
ini_get('session.name'),
'int_temp_name',
'int_temp_value'
))) {
unset ($GLOBALS[$int_temp_name]);
}
}
}
//
// Now, (re)import the variables
//
if (isset ($_REQUEST['pass']))
$ext_pass = $_REQUEST['pass'];
if (isset ($_REQUEST['user']))
$ext_user = $_REQUEST['user'];
if (isset ($_REQUEST['action']))
$ext_action = $_REQUEST['action'];
//
// Cleanup entries
//
$int_pass = (isset ($ext_pass) ? preg_replace("'[^A-Z]'", "", $ext_pass) : '');
$int_user = (isset ($ext_user) ? preg_replace("'[]A-Za-z0-9áäàâãëèéêïìîóöòôõúüùû \.^\$\!\_-()'", "", $ext_user) : '');
$int_action = (isset ($ext_action) ? intval($ext_action) : '');
//
// Import Session variables
//
if (isset ($_SESSION)) {
foreach ($_SESSION as $int_temp_key => $int_temp_value) {
if ($int_temp_value != '') {
$$int_temp_key = $int_temp_value;
}
}
}
//
// Import Cookie variables
//
if (isset ($_COOKIE)) {
foreach ($_COOKIE as $int_temp_key => $int_temp_value) {
if ($int_temp_value != '') {
$$int_temp_key = $int_temp_value;
}
}
}
//
// From here on, work only with $int_ variables and you're safe!
//
?>
With this you can prevent a lot of different problems!
subarea AT webfire DOT biz ¶
4 years ago
your webspace provider has register-globals activated by standard and you don't have a chance to turn it off? no problem anymore, here is your solution...
<?php
// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
// this is just a workaround to kill all through register globals imported vars!
// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
// place this script after session_start() to be sure you unregister_globals('_SESSION');
// that's all, now all through "register_globals" assigned vars are deleted from scope.
// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
if (ini_get('register_globals') == 1)
{
if (is_array($_REQUEST)) foreach(array_keys($_REQUEST) as $var_to_kill) unset($$var_to_kill);
if (is_array($_SESSION)) foreach(array_keys($_SESSION) as $var_to_kill) unset($$var_to_kill);
if (is_array($_SERVER)) foreach(array_keys($_SERVER) as $var_to_kill) unset($$var_to_kill);
unset($var_to_kill);
}
?>
hope you like it ;)
greetz subarea
bohwaz ¶
4 years ago
<?php
// Unregister_globals: unsets all global variables set from a superglobal array
// --------------------
// This is useful if you don't know the configuration of PHP on the server the application
// will be run
// Place this in the first lines of all of your scripts
// Don't forget that the register_global of $_SESSION is done after session_start() so after
// each session_start() put a unregister_globals('_SESSION');
function unregister_globals()
{
if (!ini_get('register_globals'))
{
return false;
}
foreach (func_get_args() as $name)
{
foreach ($GLOBALS[$name] as $key=>$value)
{
if (isset($GLOBALS[$key]))
unset($GLOBALS[$key]);
}
}
}
unregister_globals('_POST', '_GET', '_COOKIE', '_REQUEST', '_SERVER', '_ENV', '_FILES');
?>
dav at thedevelopersalliance dot com ¶
9 years ago
import_request_variables() has a good solution to part of this problem - add a prefix to all imported variables, thus almost eliminating the factor of overriding internal variables through requests. you should still check data, but adding a prefix to imports is a start.
Andrew dot GuertinNO at SPAMuvm dot edu ¶
4 years ago
It's not mentioned anywhere, but it seems register globals also affects file uploads.
When a file is uploaded (with in this case, <input type="file" name="coconut">), the following variables appear:
["_FILES"]=>
array(1) {
["coconut"]=>
array(5) {
["name"]=>
string(14) "mozicon128.png"
["type"]=>
string(9) "image/png"
["tmp_name"]=>
string(14) "/tmp/phpWgtRBx"
["error"]=>
int(0)
["size"]=>
int(15113)
}
}
When register globals is turned on, the following variables also appear:
["coconut_name"]=>
string(14) "mozicon128.png"
["coconut_type"]=>
string(9) "image/png"
["coconut"]=>
string(14) "/tmp/phpWgtRBx"
["coconut_size"]=>
int(15113)
georg_gruber at yahoo dot com ¶
4 years ago
BEWARE of using register_globals = On, it's not only bad karma but highly dangerous.
Consider the following coding:
<?php
// assume $_SESSION['user'] = array('Hello', 'World');
// assume session_start() was called somewhere before.
print('<pre>Contents of array $_SESSION[\'user\']');
print_r($_SESSION['user']);
print('<hr>Contents of array $user (PHP SETUP register_globals = On)');
print_r($user);
print('</pre>');
?>
If you manipulate $user you'll manipulate $_SESSION['user'] as well with PHP SETUP register_globals = On.
So please avoid it at any cost, no serious programmer would ever want to have register_globals = On.
alan hogan ¶
5 years ago
Useful for shared hosting or scripts that you are sharing with other people.
<?php
// Effectively turn off dangerous register_globals without having to edit php.ini
if (ini_get(register_globals)) // If register_globals is enabled
{ // Unset $_GET keys
foreach ($_GET as $get_key => $get_value) {
if (ereg('^([a-zA-Z]|_){1}([a-zA-Z0-9]|_)*$', $get_key)) eval("unset(\${$get_key});");
} // Unset $_POST keys
foreach ($_POST as $post_key => $post_value) {
if (ereg('^([a-zA-Z]|_){1}([a-zA-Z0-9]|_)*$', $post_key)) eval("unset(\${$post_key});");
} // Unset $_REQUEST keys
foreach ($_REQUEST as $request_key => $request_value) {
if (ereg('^([a-zA-Z]|_){1}([a-zA-Z0-9]|_)*$', $request_key)) eval("unset(\${$request_key});");
}
}
?>