Сообщения об ошибках
oirinely at yahoo dot com -
that piece of code will not print another value unless it looks like this:
<?php
$_SESSION['value'] = 'some value';
$value = 'another value';
$_SESSION['value'] = $value; // with this line in, $_SESSION['value'] now equals $value so it will be insecure
echo $_SESSION['value'];
?>
Использование глобальных переменных (Register_Globals)
Наверное, наиболее спорным моментом в разработке PHP стала замена значения по умолчанию для опции register_globals с ON на OFF в версии » 4.2.0. Большинство пользователей доверились разработчикам, даже не зная, что это за опция и как она влияет на работу PHP. Эта страница документации призвана показать, как эта настройка сочетается с вопросами безопасности при разработке приложений. Следует понимать, что сама по себе эта опция никак не влияет на безопасность, ургозу представляет некорректное использование предоставляемых ею возможностей.
В случае, если значение параметра register_globals ON, перед выполнением вашего кода будут инициализированы различные переменные, например, переменные, переданные при отправке формы. Также, учитывая тот факт, что PHP не требует инициализации переменных, написать потенциально опасный код очень легко. Это было очень спорным решением, но общество разработчиков PHP решило изменить значение по умолчанию этой директивы на OFF. В противном случае при написании кода разработчики не могли бы с уверенностью сказать, откуда пришла та или иная переменная и насколько она достоверна. До такого нововведения переменные, определяемые разработчиком внутри скрипта, и передаваемые пользователем внешние данные могли перемешиваться. Приведем простой пример злоупотребления конфигурационной опцией register_globals:
Пример #1 Пример опасного кода с register_globals = on
<?php
// устанавливаем переменную $authorized = true только для пользователей, прошедших авторизацию
if (authenticated_user()) {
$authorized = true;
}
// Поскольку в случае неудачи при проверке авторизации переменная $authorized
// не установлена, она может быть установлена автоматически, благодаря register_globals,
// например, при GET запросе GET auth.php?authorized=1.
// Таким образом, пройти эту проверку можно без авторизации
if ($authorized) {
include "/highly/sensitive/data.php";
}
?>
В случае register_globals = on логика работы скрипта может быть нарушена. В случае, если установленное значение off, переменная $authorized не может быть установлена из внешних данных запроса, и скрипт будет работать корректно. Но все же инициализация переменных - один из признаков хорошего тона в программировании. Например, в приведенном выше участке кода мы могли поместить $authorized = false в качестве первой строки. Такой код работал бы как со значением on, так и off опции register_globals, и подразумевая, что по умолчанию пользователь не проходил авторизацию.
Приведем еще один пример, использующий сессии. В случае, если register_globals = on, мы можем использовать переменную $username в приведенном ниже примере, но тогда у нас не будет уверенности в достоверности ее значения (к примеру, она могла быть передана в GET-запросе).
Пример #2 Пример использования сессий со значением register_globals on или off
<?php
// Мы не знаем, откуда получена переменная $username, но точно знаем, что
// переменная $_SESSION хранит в себе данные сессии
if (isset($_SESSION['username'])) {
echo "Hello <b>{$_SESSION['username']}</b>";
} else {
echo "Hello <b>Guest</b><br />";
echo "Would you like to login?";
}
?>
Также существует возможность реализации оперативного реагирования в случае попытки подмены переменных. Так как во время разработки приложения мы знаем ожидаемое значение переменной, а также знаем ее достоверное значение, мы можем их сопоставить. Это не защитит код от подмены переменных, но усложнит перебор возможных вариантов. Если вы не хотите знать, как именно были получены внешние данные, используйте переменную $_REQUEST, которая состоит из данных GET и POST запросов, а также данных COOKIE. Также, информацию об этом можно найти в разделе внешние данные в PHP.
Пример #3 Обнаружение попытки подмены переменных
<?php
if (isset($_COOKIE['MAGIC_COOKIE'])) {
// MAGIC_COOKIE получена из достоверного источника.
// Для полной уверенности необходимо проверить ее значение.
} elseif (isset($_GET['MAGIC_COOKIE']) || isset($_POST['MAGIC_COOKIE'])) {
mail("admin@example.com", "Обнаружена попытка взлома", $_SERVER['REMOTE_ADDR']);
echo "Обнаружено нарушение безопасности, администратор уведомлен.";
exit;
} else {
// MAGIC_COOKIE в данных запроса не присутствует
}
?>
Следует понимать, что установка register_globals в off не сделает ваш код безопасным. Каждую полученную от пользователя переменную следует проверять на соответствие ожидаемому значению. Всегда проверяйте ввод пользователя и инициализируйте все используемые переменные. Для проверки на наличие неинициализированных переменных можно включить в опцию error_reporting() отображение ошибок категории E_NOTICE.
Замечание: Суперглобальные переменные: замечание о доступностиНачиная с PHP 4.1.0, стали доступными суперглобальные массивы, такие как $_GET, $_POST, $_SERVER и т.д. Дополнительную информацию смотрите в разделе руководства superglobals
add a note
User Contributed NotesИспользование глобальных переменных (Register_Globals)
Anonymous
29-Apr-2008 01:14
29-Apr-2008 01:14
fab dot mariotti at [google]gmail dot com
16-Apr-2008 09:59
16-Apr-2008 09:59
For my application I defined two functions:
wit_set_gv('space','key','value')
wit_get_gv('space','key')
Forgive the "wit_" prefix but the gv stays for Global Variable.
Maybe I should start with a simple version:
wit_set_gv('key','value')
wit_get_gv('key')
This way you would set or get a global/session value.
The register_globals (on or off), session state and/or
superglobal variables will be handled by these functions.
I did add a 'space' item because I wanted to have control
on what goes to/comes from where. As an example if I call:
wit_get_gv('WIT_CONF','URL')
I know that I have to check for a global variable named
WIT_CONF which also gives me a positive responce
on isset($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
Dice
16-Apr-2008 06:46
16-Apr-2008 06:46
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
01-Apr-2008 03:59
01-Apr-2008 03:59
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($_SERVER); break;
}
}
}
?>
subarea
20-Mar-2008 05:43
20-Mar-2008 05:43
If you have no access to php.ini and the solution with
the .htaccess entry (php_flag register_globals 0)
also doesn't work or you are just a little bit paranoid,
you can use the following script.
this is just a workaround to kill all (through register globals) imported vars!
<?php
foreach(array_keys($_REQUEST) as $var_to_kill) unset($$var_to_kill);
foreach(array_keys($_SESSION) as $var_to_kill) unset($$var_to_kill);
foreach(array_keys($_SERVER) as $var_to_kill) unset($$var_to_kill);
unset($var_to_kill);
?>
if you like it, just drop me a line...
greetz subarea
dot dot dot dot dot alexander at gmail dot com
09-Mar-2008 03:19
09-Mar-2008 03:19
@ Mike Willbanks's post
This is an even cleaner version of your code:
<?php
if( ini_get(register_globals) ) {
/* genocide the damn registered globals if they are on */
foreach( $_REQUEST as $key => $var ){
if( $var === $$key ){
unset($$key);
}
}
}
?>
oirinel at yahoo dot com
18-Dec-2007 09:35
18-Dec-2007 09:35
when using register_globals=On be careful since using something like:
$_SESSION['value'] = 'some value';
$value = 'another value';
echo $_SESSION['value']; // !!! will print 'another value' !!!!
Hope this will save someone from headaches and from loosing hours!
Tumasch
13-Dec-2007 02:50
13-Dec-2007 02:50
In addition to Mike Willbanks post:
Put this to the beginning of every file or to a functions.inc.php and call it every time before start working with user variables.
This will prevent problems with wrong initalized variables or users who try to break your application.
And this has an extra bonus: Applications which still work are also register_globasl = off enabled!
<?php
//
// If register_globals is on, delete all variables exept the ones in the array
//
if (ini_get('register_globals')) {
foreach ($GLOBALS as $int_temp_name => $int_temp_value) {
if (!in_array($int_temp_name, array (
'GLOBALS',
'_FILES',
'_REQUEST',
'_COOKIE',
'_SERVER',
'_ENV',
'_SESSION',
ini_get('session.name'),
'int_temp_name',
'int_temp_value'
))) {
unset ($GLOBALS[$int_temp_name]);
}
}
}
//
// Now, (re)import the variables
//
if (isset ($_REQUEST['pass']))
$ext_pass = $_REQUEST['pass'];
if (isset ($_REQUEST['user']))
$ext_user = $_REQUEST['user'];
if (isset ($_REQUEST['action']))
$ext_action = $_REQUEST['action'];
//
// Cleanup entries
//
$int_pass = (isset ($ext_pass) ? preg_replace("'[^A-Z]'", "", $ext_pass) : '');
$int_user = (isset ($ext_user) ? preg_replace("'[]A-Za-z0-9áäàâãëèéêïìîóöòôõúüùû \.^\$\!\_-()'", "", $ext_user) : '');
$int_action = (isset ($ext_action) ? intval($ext_action) : '');
//
// Import Session variables
//
if (isset ($_SESSION)) {
foreach ($_SESSION as $int_temp_key => $int_temp_value) {
if ($int_temp_value != '') {
$$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 != '') {
$$int_temp_key = $int_temp_value;
}
}
}
//
// From here on, work only with $int_ variables and you're safe!
//
?>
With this you can prevent a lot of different problems!
Mike Willbanks
05-Sep-2007 05:40
05-Sep-2007 05:40
Sorry the last php code I submitted was formatted nice but I changed some things for readability and didn't implement it across the board. Here is the correct code:
<?php
if (ini_get(register_globals)) {
$rg = array_keys($_REQUEST);
foreach($rg as $var)
{
if ($_REQUEST[$var] === $$var)
{
unset($$var);
}
}
}
?>
Mike Willbanks
29-Aug-2007 08:15
29-Aug-2007 08:15
Alans code may get rid of globals but it is slow since it is doing regular expressions on each of the input items. Then to add on more time the code is being passed through eval.
Besides the slower performance, his code is not checking to see if the variable may have been changed at any state before this code is being done.
There might be auto_prepended files or include files that might need to run before it. He is also going through get and post and lastly request which is a little silly seeing as request will contain the get, post and cookie so he has run get and post twice.
Here is a more effective fix that will take all the keys in request which become variable names and checks to make sure that the variables match then unsets the element.
<?php
if (ini_get(register_globals)) {
$rg = array_keys($_REQUEST);
foreach($rg as $var)
{
if ($_REQUEST[$v] === $$v)
{
unset($$v);
}
}
}
?>
alan hogan
20-Jul-2007 05:08
20-Jul-2007 05:08
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});");
}
}
?>
Timbo
14-Jul-2007 05:25
14-Jul-2007 05:25
In response to the above post by Caliwebman at yahoo dot com, a.k.a. "Gentle Warrior" who complained about the lack of documentation on register_globals:
I think this code snippet will address the *main* source of his confusion:
<?
function readyToBeAProgrammer()
{
$stuff=$_URINALYSIS['test'];
if($stuff == THC)
{
return false;
}
else
{
return true;
}
// register_globals is all about knowing where your variables are really coming from
// what if a malicious user tried to pass off
// $stuff=$_GET['someone_elses_drop']; // as $stuff ?
// preventing this kind of substitution is the whole point
// of disabling register_globals
}
if(!readyToBeAProgrammer())
{
die("Switch to coffee, man!");
}
?>
P.S., let's give it up in appreciation for the moderators who must sit though and clean up these boards, facetious posts like mine included...
caliwebman at yahoo dot com
10-Jul-2007 12:29
10-Jul-2007 12:29
U know what I find incredibly insane? The fact that no where on the first pages <<<PLURAL does anyone even suggest where to find this code. And IF it exists in a file called "register_globals-etc..." than I have no clue why none of my sites have this file. It amazes me that we here on this side have made things so incredibly difficult on ourselves and the newer coders. Why? I thought that was what Microsoft was doing but quite honestly follks, we here on this side have MS beat when it comes to making things MUCH more of a challenge than they need be.
PLEASE, please dumb things down. And if you can't? ASK someone who is NOT in your bubble of code to review what you are writing in your dirstructions.... directions.... ask someoen like your MOM or DAD who know nothing of the code.
We sure would get going mch more quickly if we all paid attenttion to this simple rule.... and lastly, the front end designers are finally getting it together..... thank you, but again, remember, THE 3 CLICK RULE!!!
Peace,
Gentle Warrior
Scott
29-Jun-2007 07:19
29-Jun-2007 07:19
I couldn't get any of the suggested ways to disable register_globals to work in what I believe to be an Apache environment, where even phpinfo() is disabled. I finally had to resort to
foreach(array_keys($_REQUEST) as $field)
{
unset(${$field});
}
to get the $_REQUEST array without auto-setting all the request variables. I'm somewhat new to the whole PHP thing and wonder if there is a downside to this that I don't see.
someone at example dot com
17-Apr-2007 09:14
17-Apr-2007 09:14
In reply to yyalcinkaya at ku edu tr you could just do this with $_REQUEST:
foreach($_REQUEST as $k => $v)
{
${$k} = $v;
}
...though doing something like this is asking for a world of trouble IMHO.
yyalcinkaya at ku edu tr
28-Mar-2007 12:37
28-Mar-2007 12:37
if you want to keep register_globals off you can use this codes instead.
foreach($_POST AS $key => $value) {
${$key} = $value;
}
foreach($_GET AS $key => $value) {
${$key} = $value;
}
alan at xensource dot com
15-Nov-2005 06:00
15-Nov-2005 06:00
From the PHP Manual page on Using register_globals:
Do not use extract() on untrusted data, like user-input ($_GET, ...). If you do, for example, if you want to run old code that relies on register_globals temporarily, make sure you use one of the non-overwriting extract_type values such as EXTR_SKIP and be aware that you should extract in the same order that's defined in variables_order within the php.ini.
Dexter at dexpark dot com
06-Nov-2005 03:59
06-Nov-2005 03:59
For Apache users or webhosters, you can set the
php_flag register_globals on/off in a VirtualHost context.
dyer85 at gmail dot com
05-Nov-2005 07:10
05-Nov-2005 07:10
I'd suggest taking a look at php.net's source code for these user notes, if you want to get ideas on some nice ways to collect and validate user data.
http://php.net/source.php?url=/manual/add-note.php
hbinduni at gmail dot com
30-Oct-2005 10:06
30-Oct-2005 10:06
[quote]
If you're under an Apache environment that has this option enabled, but you're on shared hosting so have no access to php.ini, you can unset this value for your own site by placing the following in an .htaccess file in the root:
php_flag register_globals 0
[/quote]
adding php_flag in .htaccess under apache 2 will cause internal server error. according to apache 2 manual, php_flag should goes to <virtual> or <directory> section.
ramosa (0) gmail dotty com
24-Sep-2005 06:24
24-Sep-2005 06:24
Here's a one liner that works both with register globals on or off, and is even secure enough when it's on, as you make sure you init the var.
Using the ?: operator
$variable = isset($_GET["variable"]) ? $_GET["variable"] : "";
kcinick at ciudad dot com dot ar
19-May-2005 12:12
19-May-2005 12:12
if you plan to use php_admin_value register_globals [0-1] inside <VirtualHost> in apache, forget it, it don't show any error messages in the configuration, but at the time of running, it enable and disables register_globals at random request, if you need to customize this param to multiple virtual host, put it in a <Directory> directives, it works fine there...
PD: same for safe_mode, etc...
ryanwray at gmail dot com
24-Nov-2004 04:03
24-Nov-2004 04:03
In reply to ben at nullcreations dot net:
This is true of the super-global $_SESSION, as it will always be processed last (it is not considered in variables_order directive)
However, it is possible to over-write other data, namely GET, POST, COOKIE, ENVIROMENT and SERVER.
Of course, what you can overwrite will depend on the directive variables_order - by default, you could overwrite GET and POST data via COOKIE (because cookie data is processed last out of the three which should not really be of great concern.
My below code is irrelevant unless extract or another method which does the same thing (ie. I have seen variable variables used before to reach the same affect) is used.
ben at nullcreations dot net
23-Nov-2004 01:53
23-Nov-2004 01:53
Just a note to all the people who think $_SESSION can be poisoned by register_globals - it can't.
Consider the fact that GET/POST/COOKIE is Processed *before* sessions are. This means that even if you have register_globals on, and they write to $_SESSION, $_SESSION will just get reset again with the appropriate values.
Some people take to using extract() as a means to simulate register_globals in scripts where they're not sure what the server environment will be - this is when you should worry about such things. The reason is because extract() can concievably occur after GET/POST/COOKIE and SESSION processing.
snarkles <anything at $myname dot net>
19-May-2004 09:06
19-May-2004 09:06
If you're under an Apache environment that has this option enabled, but you're on shared hosting so have no access to php.ini, you can unset this value for your own site by placing the following in an .htaccess file in the root:
php_flag register_globals 0
The ini_set() function actually accomplishes nothing here, since the variables will have already been created by the time the script processes the ini file change.
And since this is the security chapter, just as a side note, another thing that's helpful to put into your .htaccess is:
<Files ".ht*">
deny from all
</Files>
That way no one can load .htaccess in their browser and have a peek at its contents.
Sorry, not aware of a similar workaround for IIS. :\
dav at thedevelopersalliance dot com
18-Dec-2003 07:38
18-Dec-2003 07:38
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.