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Escaper


Genel Bakış

Websites and web applications are vulnerable to XSS attacks and although PHP provides escaping functionality, in some contexts it is not sufficient/appropriate. Phalcon\Escaper provides contextual escaping and is written in Zephir, providing the minimal overhead when escaping different kinds of texts.

We designed this component based on the XSS (Cross Site Scripting) Prevention Cheat Sheet created by the OWASP. Additionally, this component relies on mbstring to support almost any charset. To illustrate how this component works and why it is important, consider the following example:

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$title = '</title><script>alert(1)</script>';
echo $escaper->escapeHtml($title);
// &lt;/title&gt;&lt;script&gt;alert(1)&lt;/script&gt;

$css = ';`(';
echo $escaper->escapeCss($css);
// &#x3c &#x2f style&#x3e

$fontName = 'Verdana\"</style>';
echo $escaper->escapeCss($fontName);
// Verdana\22 \3c \2f style\3e

$js = "';</script>Hello";
echo $escaper->escapeJs($js);
// \x27\x3b\x3c\2fscript\x3eHello

HTML

You can escape text prior to printing it to your views using escapeHtml(). Without escaping you could potentially echo unsafe data in your HTML output.

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$title = '</title><script>alert(1)</script>';
echo $escaper->escapeHtml($title);
// &lt;/title&gt;&lt;script&gt;alert(1)&lt;/script&gt;

HTML syntax:

<?php echo $this->escaper->escapeHtml($title); ?>

Volt syntax:

{{ title | escape }}

HTML Attributes

Escaping attributes is different than escaping HTML content. The escaper works by changing every non-alphanumeric character to a safe format. It uses htmlspecialchars internally. This kind of escaping is intended escape excluding complex ones such as href or url. To escape attributes, you can use the escapeHtmlAttr() method

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$attr = '"><h1>Hello</table';
echo $escaper->escapeHtmlAttr($attr);
// &#x22;&#x3e;&#x3c;h1&#x3e;Hello&#x3c;&#x2f;table

HTML syntax:

<?php echo $this->escaper->escapeHtmlAttr($attr); ?>

Volt syntax:

{{ attr | escape_attr }}

URLs

escapeUrl() can be used to escape attributes such as href or url:

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$url = '"><script>alert(1)</script><a href="#';
echo $escaper->escapeHtmlAttr($url);
// %22%3E%3Cscript%3Ealert%281%29%3C%2Fscript%3E%3Ca%20href%3D%22%23

HTML syntax:

<?php echo $this->escaper->escapeHtmlAttr($url); ?>

CSS

CSS identifiers/values can be escaped by using escapeCss():

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$css = '"><script>alert(1)</script><a href="#';
echo $escaper->escapeCss($css);
// \22 \3e \3c script\3e alert\28 1\29 \3c \2f script\3e \3c a\20 href\3d \22 \23 

HTML syntax:

<?php echo $this->escaper->escapeCss($css); ?>

Volt syntax:

{{ css | escape_css }}

JavaScript

Content printed into javascript code must be properly escaped. escapeJs() helps with this task:

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$js = "'; alert(100); var x='";
echo $escaper->escapeJs($js);
// \x27; alert(100); var x\x3d\x27

HTML syntax:

<?php echo $this->escaper->escapeJs($js); ?>

Volt syntax:

{{ js | escape_js }}

Encoding

Phalcon\Escape also offers methods regarding the encoding of the text to be escaped.

detectEncoding()

Detects the character encoding of a string to be handled by an encoder. Special-handling for chr(172) and chr(128) to chr(159) which fail to be detected mb_detect_encoding. The method returns a string with the detected encoding or null

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

echo $escaper->detectEncoding('ḂḃĊċḊḋḞḟĠġṀṁ'); // UTF-8

getEncoding()

Returns the internal encoding used by the escaper

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

echo $escaper->getEncoding();

normalizeEncoding()

Utility method that normalizes a string’s encoding to UTF-32.

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

echo $escaper->normalizeEncoding('ḂḃĊċḊḋḞḟĠġṀṁ');  

setEncoding()

Sets the encoding to be used by the escaper

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$escaper->setEncoding('utf-8');

echo $escaper->getEncoding(); // 'utf-8'

setDoubleEncode()

Sets the escaper to use double encoding or not (default true)

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$escaper->setDoubleEncode(false);

setHtmlQuoteType()

You can set the quote type to be used by the escaper. The passed variable is one of the constants that htmlspecialchars accepts: - ENT_COMPAT - ENT_QUOTES - ENT_NOQUOTES - ENT_IGNORE - ENT_SUBSTITUTE - ENT_DISALLOWED - ENT_HTML401 - ENT_XML1 - ENT_XHTML - ENT_HTML5

<?php

use Phalcon\Escaper;

$escaper = new Escaper();

$escaper->setHtmlQuoteType(ENT_XHTML);

Exceptions

Any exceptions thrown in the Escaper component will be of type Phalcon\Escaper\Exception. It is thrown when the data supplied to the component is not valid. You can use these exceptions to selectively catch exceptions thrown only from this component.

<?php

use Phalcon\Escaper;
use Phalcon\Escaper\Exception;
use Phalcon\Mvc\Controller;

/**
 * @property Escaper $escaper
 */
class IndexController extends Controller
{
    public function index()
    {
        try {
            echo $this->escaper->normalizeEncoding('ḂḃĊċḊḋḞḟĠġṀṁ');  
        } catch (Exception $ex) {
            echo $ex->getMessage();
        }
    }
}

Dependency Injection

If you use the Phalcon\Di\FactoryDefault container, the Phalcon\Escaper is already registered for you with the name escaper.

An example of the registration of the service as well as accessing it is below:

<?php

use Phalcon\Di;
use Phalcon\Escaper;

$container = new Di();

$container->set(
    'escaper',
    function () use  {
        return new Escaper();
    }
);

You can now use the component in a controller (or a component that implements Phalcon\Di\Injectable)

<?php

namespace MyApp;

use Phalcon\Escaper;
use Phalcon\Mvc\Controller;

/**
 * Invoices controller
 *
 * @property Escaper $escaper
 */
class InvoicesController extends Controller
{
    public function indexAction()
    {

    }

    public function saveAction()
    {
        echo $this->escaper->escapeHtml('The post was correctly saved!');
    }
}

Custom

Phalcon also offers the Phalcon\Escaper\EscaperInterface which can be implemented in a custom class. The class can offer the escaper functionality you require.

<?php

namespace MyApp\Escaper;

use Phalcon\Escaper\EscaperInterface;

class Custom extends EscaperInterface
{
    /**
     * Escape CSS strings by replacing non-alphanumeric chars by their
     * hexadecimal representation
     */
    public function escapeCss(string $css): string;

    /**
     * Escapes a HTML string
     */
    public function escapeHtml(string $text): string;

    /**
     * Escapes a HTML attribute string
     */
    public function escapeHtmlAttr(string $text): string;

    /**
     * Escape Javascript strings by replacing 
     * non-alphanumeric chars by their hexadecimal 
     * representation
     */
    public function escapeJs(string $js): string;

    /**
     * Escapes a URL. Internally uses rawurlencode
     */
    public function escapeUrl(string $url): string;

    /**
     * Returns the internal encoding used by the escaper
     */
    public function getEncoding(): string;

    /**
     * Sets the encoding to be used by the escaper
     */
    public function setEncoding(string $encoding): void;

    /**
     * Sets the HTML quoting type for htmlspecialchars
     */
    public function setHtmlQuoteType(int $quoteType): void;
}