With “magic quotes” disabled, why does PHP/Wordpre

问题:

It's a simple question with a strangely elusive answer.

get_magic_quotes_gpc() reports 0. I repeat, magic quotes are off. Magic quotes appear to have been disabled in php.ini (not at runtime).

Nevertheless, all POST data including single quotes (') is escaped when accessed in PHP. What could be causing this?

Thank you.

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Edit: For the curious, this is a screenshot of our phpinfo: http://img843.imageshack.us/img843/6959/screenshot20120120at552.png

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Edit: While preparing a test case, I discovered the general origin of the problem. We're bootstrapping Wordpress as our app integrates with a WP Multisite installation. When I disable the Wordpress bootstrapping, the auto-escaping is disabled. Does anyone know where Wordpress' auto-escape code may be located?

回答1:

I think I found it. Problem (bug): http://core.trac.wordpress.org/ticket/18322

Solution: http://codex.wordpress.org/Function_Reference/stripslashes_deep

    $_GET       = array_map('stripslashes_deep', $_GET);
    $_POST      = array_map('stripslashes_deep', $_POST);
    $_COOKIE    = array_map('stripslashes_deep', $_COOKIE);
    $_SERVER    = array_map('stripslashes_deep', $_SERVER);
    $_REQUEST   = array_map('stripslashes_deep', $_REQUEST);

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Note: As suggested by @Alexandar O'Mara, you might want to reconsider overwriting the superglobals like this. If it's appropriate for your situation, for example, you might just "strip locally" using an alternative like $post = array_map('stripslashes_deep', $_POST);

Also see @quickshiftin's excellent answer.

回答2:

Expanding on @rinogo's answer with a deeper explanation, and offering another workaround.

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In wp-settings.php there's an unconditional call to wp_magic_quotes

// Add magic quotes and set up $_REQUEST ( $_GET + $_POST )
wp_magic_quotes();

Wordpress escapes quotes no matter what

function wp_magic_quotes() {
    // If already slashed, strip.
    // Escape with wpdb.
    // Force REQUEST to be GET + POST.
}

What's interesting though is this call is made after plugins have been loaded, before the theme is loaded. Sooo, at the top of your plugin

// A hack to cope with un-configurable call to wp_magic_quotes
// E.G. Make the original $_POST available through a global $_REAL_POST
$_REAL_GET     = $_GET;
$_REAL_POST    = $_POST;
$_REAL_COOKIE  = $_COOKIE;
$_REAL_REQUEST = $_REQUEST;

Then you can freely use $_REAL_POST et al in place of $_POST (remembering it's a global not a superglobal) where you need to. Also remember that while your plugin has loaded before the theme, if the theme calls down into one of the plugin functions which uses $_POST, it should read from $_REAL_POST to get the unescaped values.

回答3:

The best answer provided here is to copy for own use like:

$post = array_map('stripslashes_deep', $_POST);

There's a theoretical problem with this however: since you're working with a duplicate, you can't persist any changes to the superglobals (hey, I'm not saying it's a good practice, alright?).

Solution: accessor methods

In an attempt to solve this mess in a definite manner and without any side effects, I made "accessor methods" which transparently apply stripslashes_deep() or addslashes_deep()* to get/set requests to the following superglobal arrays:

^{* I had to throw addslashes_deep() together from WordPress' stripslashes_deep().}

• $_GET
• $_POST
• $_COOKIE
• $_SERVER
• $_REQUEST

You can use them like:

echo _get('username');    // echo stripslashes_deep($_GET['username']);
_cookie('name', 'value'); // $_COOKIE['name'] = addslashes_deep('value');

Here's the code (I call it gpcsr.php):

<?php

// cat stripslashes_deep() | sed 's/stripslashes/addslashes/g'
function addslashes_deep( $value ) {
    if ( is_array($value) ) {
        $value = array_map('addslashes_deep', $value);
    } elseif ( is_object($value) ) {
        $vars = get_object_vars( $value );
        foreach ($vars as $key=>$data) {
            $value->{$key} = addslashes_deep( $data );
        }
    } elseif ( is_string( $value ) ) {
        $value = addslashes($value);
    }

    return $value;
}

function _generic_slashes_wrap(&$arr, $key, $value = null) {
    if (func_num_args() === 2) return stripslashes_deep($arr[$key]);
    else $arr[$key] = addslashes_deep($value);
}

function _get       ($key, $value = null) { if (func_num_args() === 1) return _generic_slashes_wrap($_GET,      $key); else _generic_slashes_wrap($_GET,        $key, $value); }
function _post      ($key, $value = null) { if (func_num_args() === 1) return _generic_slashes_wrap($_POST,     $key); else _generic_slashes_wrap($_POST,       $key, $value); }
function _cookie    ($key, $value = null) { if (func_num_args() === 1) return _generic_slashes_wrap($_COOKIE,   $key); else _generic_slashes_wrap($_COOKIE,     $key, $value); }
function _server    ($key, $value = null) { if (func_num_args() === 1) return _generic_slashes_wrap($_SERVER,   $key); else _generic_slashes_wrap($_SERVER,     $key, $value); }
function _request   ($key, $value = null) { if (func_num_args() === 1) return _generic_slashes_wrap($_REQUEST,  $key); else _generic_slashes_wrap($_REQUEST,    $key, $value); }

?>

回答4:

I just had to deal with this issue and found what I think is a pretty nice workaround. It ensures that the GPCs are never slashed. I just put this at the top of my plugin file (it would work at the top of a theme too, I think):

add_action( 'init', 'unslash_gpc' );
function unslash_gpc() {
    $_GET       = array_map('stripslashes_deep', $_GET);
    $_POST      = array_map('stripslashes_deep', $_POST);
    $_COOKIE    = array_map('stripslashes_deep', $_COOKIE);
    $_SERVER    = array_map('stripslashes_deep', $_SERVER);
    $_REQUEST   = array_map('stripslashes_deep', $_REQUEST);
}

And now everything is perfect!

回答5:

Wordpress provides a solution for this by using the wordpress function stripslashes_deep. So, the snippets mentioned in @rinogo's answer would become :

$_GET     = stripslashes_deep($_GET);
$_POST    = stripslashes_deep($_POST);
$_COOKIE  = stripslashes_deep($_COOKIE);
$_REQUEST = stripslashes_deep($_REQUEST);

Also a note, wordpress doesn't say anything about the $_SERVER global variable, so I would assume it's not affected.

WordPress adds slashes to $_POST/$_GET/$_REQUEST/$_COOKIE regardless of what get_magic_quotes_gpc() returns. So in the context of WordPress, stripslashes() or stipslashes_deep() should always be used when using those variables.

回答6:

Or, just do like I did. Comment out all of the implementation in load.php's wp_magic_quotes() method.

I have no use for magic quotes. This was causing me many more headaches than it was worth. Personally, I prefer to maintain my own discipline of input sanitation. I just don't want to start forming bad programming habits.

But, I do understand WordPress' compulsion to include such a "feature". Perhaps the development community would be best served with a global option to disable it.