The HTML Sanitizer component aims at sanitizing/cleaning untrusted HTML code (e.g. created by a WYSIWYG editor in the browser) into HTML that can be trusted. It is based on the HTML Sanitizer W3C Standard Proposal.
The HTML sanitizer creates a new HTML structure from scratch, taking only the elements and attributes that are allowed by configuration. This means that the returned HTML is very predictable (it only contains allowed elements), but it does not work well with badly formatted input (e.g. invalid HTML). The sanitizer is targeted for two use cases:
- Preventing security attacks based on :ref:`XSS <xss-attacks>` or other technologies relying on the execution of malicious code on the visitors browsers;
- Generating HTML that always respects a certain format (only certain tags, attributes, hosts, etc.) to be able to consistently style the resulting output with CSS. This also protects your application against attacks related to e.g. changing the CSS of the whole page.
You can install the HTML Sanitizer component with:
$ composer require symfony/html-sanitizer
Use the :class:`Symfony\\Component\\HtmlSanitizer\\HtmlSanitizer` class to
sanitize the HTML. In the Symfony framework, this class is available as the
html_sanitizer service. This service will be :doc:`autowired </service_container/autowiring>`
automatically when type-hinting for
:class:`Symfony\\Component\\HtmlSanitizer\\HtmlSanitizerInterface`:
.. configuration-block::
.. code-block:: php-symfony
// src/Controller/BlogPostController.php
namespace App\Controller;
// ...
use Symfony\Component\HtmlSanitizer\HtmlSanitizerInterface;
class BlogPostController extends AbstractController
{
public function createAction(HtmlSanitizerInterface $htmlSanitizer, Request $request): Response
{
$unsafeContents = $request->getPayload()->get('post_contents');
$safeContents = $htmlSanitizer->sanitize($unsafeContents);
// ... proceed using the safe HTML
}
}
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$htmlSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())->allowSafeElements()
);
// unsafe HTML (e.g. from a WYSIWYG editor in the browser)
$unsafePostContents = ...;
$safePostContents = $htmlSanitizer->sanitize($unsafePostContents);
// ... proceed using the safe HTML
Note
The default configuration of the HTML sanitizer allows all "safe" elements and attributes, as defined by the W3C Standard Proposal. In practice, this means that the resulting code will not contain any scripts, styles or other elements that can cause the website to behave or look different. Later in this article, you'll learn how to :ref:`fully customize the HTML sanitizer <html-sanitizer-configuration>`.
The default :method:`Symfony\\Component\\HtmlSanitizer\\HtmlSanitizer::sanitize`
method cleans the HTML code for usage in the <body> element. Using the
:method:`Symfony\\Component\\HtmlSanitizer\\HtmlSanitizer::sanitizeFor`
method, you can instruct HTML sanitizer to customize this for the
<head> or a more specific HTML tag:
// tags not allowed in <head> will be removed
$safeInput = $htmlSanitizer->sanitizeFor('head', $userInput);
// encodes the returned HTML using HTML entities
$safeInput = $htmlSanitizer->sanitizeFor('title', $userInput);
$safeInput = $htmlSanitizer->sanitizeFor('textarea', $userInput);
// uses the <body> context, removing tags only allowed in <head>
$safeInput = $htmlSanitizer->sanitizeFor('body', $userInput);
$safeInput = $htmlSanitizer->sanitizeFor('section', $userInput);
The HTML sanitizer component directly integrates with Symfony Forms, to sanitize the form input before it is processed by your application.
You can enable the sanitizer in TextType forms, or any form extending
this type (such as TextareaType), using the sanitize_html option:
// src/Form/BlogPostType.php
namespace App\Form;
// ...
class BlogPostType extends AbstractType
{
// ...
public function configureOptions(OptionsResolver $resolver): void
{
$resolver->setDefaults([
'sanitize_html' => true,
// use the "sanitizer" option to use a custom sanitizer (see below)
//'sanitizer' => 'app.post_sanitizer',
]);
}
}
Besides sanitizing user input, you can also sanitize HTML code before
outputting it in a Twig template using the sanitize_html() filter:
{{ post.body|sanitize_html }}
{# you can also use a custom sanitizer (see below) #}
{{ post.body|sanitize_html('app.post_sanitizer') }}The behavior of the HTML sanitizer can be fully customized. This allows you to explicitly state which elements, attributes and even attribute values are allowed.
You can do this by defining a new HTML sanitizer in the configuration:
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
block_elements:
- h1
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<framework:sanitizer name="app.post_sanitizer">
<framework:block-element name="h1"/>
</framework:sanitizer>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
->blockElement('h1')
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
->blockElement('h1')
);
This configuration defines a new html_sanitizer.sanitizer.app.post_sanitizer
service. This service will be :doc:`autowired </service_container/autowiring>`
for services having an HtmlSanitizerInterface $appPostSanitizer parameter.
You can start the custom HTML sanitizer by using one of the two baselines:
- Static elements
- All elements and attributes on the baseline allow lists from the W3C Standard Proposal (this does not include scripts).
- Safe elements
- All elements and attributes from the "static elements" list, excluding elements and attributes that can also lead to CSS injection/click-jacking.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# enable either of these
allow_safe_elements: true
allow_static_elements: true
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<!-- allow-safe-elements/allow-static-elements:
enable either of these -->
<framework:sanitizer
name="app.post_sanitizer"
allow-safe-elements="true"
allow-static-elements="true"
/>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// enable either of these
->allowSafeElements(true)
->allowStaticElements(true)
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// enable either of these
->allowSafeElements()
->allowStaticElements()
);
This adds elements to the allow list. For each element, you can also specify the allowed attributes on that element. If not given, all allowed attributes from the W3C Standard Proposal are allowed.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
allow_elements:
# allow the <article> element and 2 attributes
article: ['class', 'data-attr']
# allow the <img> element and preserve the src attribute
img: 'src'
# allow the <h1> element with all safe attributes
h1: '*'
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<!-- allow-safe-elements/allow-static-elements:
enable either of these -->
<framework:sanitizer name="app.post_sanitizer">
<!-- allow the <article> element and 2 attributes -->
<framework:allow-element name="article">
<framework:attribute>class</framework:attribute>
<framework:attribute>data-attr</framework:attribute>
</framework:allow-element>
<!-- allow the <img> element and preserve the src attribute -->
<framework:allow-element name="img">
<framework:attribute>src</framework:attribute>
</framework:allow-element>
<!-- allow the <h1> element with all safe attributes -->
<framework:allow-element name="img">
<framework:attribute>*</framework:attribute>
</framework:allow-element>
</framework:sanitizer>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// allow the <article> element and 2 attributes
->allowElement('article', ['class', 'data-attr'])
// allow the <img> element and preserve the src attribute
->allowElement('img', 'src')
// allow the <h1> element with all safe attributes
->allowElement('h1', '*')
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// allow the <article> element and 2 attributes
->allowElement('article', ['class', 'data-attr'])
// allow the <img> element and preserve the src attribute
->allowElement('img', 'src')
// allow the <h1> element with all safe attributes
->allowElement('h1')
);
You can also block (the element will be removed, but its children will be kept) or drop (the element and its children will be removed) elements.
This can also be used to remove elements from the allow list.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
# remove <div>, but process the children
block_elements: ['div']
# remove <figure> and its children
drop_elements: ['figure']
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<!-- remove <div>, but process the children -->
<framework:block-element>div</framework:block-element>
<!-- remove <figure> and its children -->
<framework:drop-element>figure</framework:drop-element>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// remove <div>, but process the children
->blockElement('div')
// remove <figure> and its children
->dropElement('figure')
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// remove <div>, but process the children
->blockElement('div')
// remove <figure> and its children
->dropElement('figure')
);
Using this option, you can specify which attributes will be preserved in the returned HTML. The attribute will be allowed on the given elements, or on all elements allowed before this setting.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
allow_attributes:
# allow "src' on <iframe> elements
src: ['iframe']
# allow "data-attr" on all elements currently allowed
data-attr: '*'
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<!-- allow "src' on <iframe> elements -->
<framework:allow-attribute name="src">
<framework:element>iframe</framework:element>
</framework:allow-attribute>
<!-- allow "data-attr" on all elements currently allowed -->
<framework:allow-attribute name="data-attr">
<framework:element>*</framework:element>
</framework:allow-attribute>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// allow "src' on <iframe> elements
->allowAttribute('src', ['iframe'])
// allow "data-attr" on all elements currently allowed
->allowAttribute('data-attr', '*')
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// allow "src' on <iframe> elements
->allowAttribute('src', ['iframe'])
// allow "data-attr" on all elements currently allowed
->allowAttribute('data-attr', '*')
);
This option allows you to disallow attributes that were allowed before.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
allow_attributes:
# allow the "data-attr" on all safe elements...
data-attr: '*'
drop_attributes:
# ...except for the <section> element
data-attr: ['section']
# disallows "style' on any allowed element
style: '*'
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<!-- allow the "data-attr" on all safe elements... -->
<framework:allow-attribute name="data-attr">
<framework:element>*</framework:element>
</framework:allow-attribute>
<!-- ...except for the <section> element -->
<framework:drop-attribute name="data-attr">
<framework:element>section</framework:element>
</framework:drop-attribute>
<!-- disallows "style' on any allowed element -->
<framework:drop-attribute name="style">
<framework:element>*</framework:element>
</framework:drop-attribute>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// allow the "data-attr" on all safe elements...
->allowAttribute('data-attr', '*')
// ...except for the <section> element
->dropAttribute('data-attr', ['section'])
// disallows "style' on any allowed element
->dropAttribute('style', '*')
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// allow the "data-attr" on all safe elements...
->allowAttribute('data-attr', '*')
// ...except for the <section> element
->dropAttribute('data-attr', ['section'])
// disallows "style' on any allowed element
->dropAttribute('style', '*')
);
Using this option, you can force an attribute with a given value on an
element. For instance, use the follow config to always set rel="noopener noreferrer" on each <a>
element (even if the original one didn't contain a rel attribute):
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
force_attributes:
a:
rel: noopener noreferrer
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<framework:force-attribute name="a">
<framework:attribute name="rel">noopener noreferrer</framework:attribute>
</framework:force-attribute>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
->forceAttribute('a', ['rel' => 'noopener noreferrer'])
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
->forceAttribute('a', 'rel', 'noopener noreferrer')
);
Besides allowing/blocking elements and attributes, you can also control the
URLs of <a> elements:
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
# if `true`, all URLs using the `http://` scheme will be converted to
# use the `https://` scheme instead. `http` still needs to be allowed
# in `allowed_link_schemes`
force_https_urls: true
# specifies the allowed URL schemes. If the URL has a different scheme, the
# attribute will be dropped
allowed_link_schemes: ['http', 'https', 'mailto']
# specifies the allowed hosts, the attribute will be dropped if the
# URL contains a different host. Subdomains are allowed: e.g. the following
# config would also allow 'www.symfony.com', 'live.symfony.com', etc.
allowed_link_hosts: ['symfony.com']
# whether to allow relative links (i.e. URLs without scheme and host)
allow_relative_links: true
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<!-- force-https-urls: if `true`, all URLs using the `http://` scheme will be
converted to use the `https://` scheme instead.
`http` still needs to be allowed in `allowed-link-scheme` -->
<!-- allow-relative-links: whether to allow relative links (i.e. URLs without
scheme and host) -->
<framework:html-sanitizer
force-https-urls="true"
allow-relative-links="true"
>
<!-- specifies the allowed URL schemes. If the URL has a different scheme,
the attribute will be dropped -->
<allowed-link-scheme>http</allowed-link-scheme>
<allowed-link-scheme>https</allowed-link-scheme>
<allowed-link-scheme>mailto</allowed-link-scheme>
<!-- specifies the allowed hosts, the attribute will be dropped if the
URL contains a different host. Subdomains are allowed: e.g. the following
config would also allow 'www.symfony.com', 'live.symfony.com', etc. -->
<allowed-link-host>symfony.com</allowed-link-host>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// if `true`, all URLs using the `http://` scheme will be converted to
// use the `https://` scheme instead. `http` still needs to be
// allowed in `allowedLinkSchemes`
->forceHttpsUrls(true)
// specifies the allowed URL schemes. If the URL has a different scheme, the
// attribute will be dropped
->allowedLinkSchemes(['http', 'https', 'mailto'])
// specifies the allowed hosts, the attribute will be dropped if the
// URL contains a different host. Subdomains are allowed: e.g. the following
// config would also allow 'www.symfony.com', 'live.symfony.com', etc.
->allowedLinkHosts(['symfony.com'])
// whether to allow relative links (i.e. URLs without scheme and host)
->allowRelativeLinks(true)
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// if `true`, all URLs using the `http://` scheme will be converted to
// use the `https://` scheme instead. `http` still needs to be
// allowed in `allowedLinkSchemes`
->forceHttpsUrls()
// specifies the allowed URL schemes. If the URL has a different scheme, the
// attribute will be dropped
->allowedLinkSchemes(['http', 'https', 'mailto'])
// specifies the allowed hosts, the attribute will be dropped if the
// URL contains a different host which is not a subdomain of the allowed host
->allowedLinkHosts(['symfony.com']) // Also allows any subdomain (i.e. www.symfony.com)
// whether to allow relative links (i.e. URLs without scheme and host)
->allowRelativeLinks()
);
Like :ref:`link URLs <html-sanitizer-link-url>`, you can also control the
URLs of other media in the HTML. The following attributes are checked by
the HTML sanitizer: src, href, lowsrc, background and ping.
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
# if `true`, all URLs using the `http://` scheme will be converted to
# use the `https://` scheme instead. `http` still needs to be allowed
# in `allowed_media_schemes`
force_https_urls: true
# specifies the allowed URL schemes. If the URL has a different scheme, the
# attribute will be dropped
allowed_media_schemes: ['http', 'https', 'mailto']
# specifies the allowed hosts, the attribute will be dropped if the URL
# contains a different host which is not a subdomain of the allowed host
allowed_media_hosts: ['symfony.com'] # Also allows any subdomain (i.e. www.symfony.com)
# whether to allow relative URLs (i.e. URLs without scheme and host)
allow_relative_medias: true
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<!-- force-https-urls: if `true`, all URLs using the `http://` scheme will be
converted to use the `https://` scheme instead. `http`
still needs to be allowed in `allowed-media-scheme` -->
<!-- allow-relative-medias: whether to allow relative URLs (i.e. URLs without
scheme and host) -->
<framework:html-sanitizer
force-https-urls="true"
allow-relative-medias="true"
>
<!-- specifies the allowed URL schemes. If the URL has a different scheme,
the attribute will be dropped -->
<allowed-media-scheme>http</allowed-media-scheme>
<allowed-media-scheme>https</allowed-media-scheme>
<allowed-media-scheme>mailto</allowed-media-scheme>
<!-- specifies the allowed hosts, the attribute will be dropped if the URL
contains a different host which is not a subdomain of the allowed host.
Also allows any subdomain (i.e. www.symfony.com) -->
<allowed-media-host>symfony.com</allowed-media-host>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// if `true`, all URLs using the `http://` scheme will be converted to
// use the `https://` scheme instead. `http` still needs to be
// allowed in `allowedMediaSchemes`
->forceHttpsUrls(true)
// specifies the allowed URL schemes. If the URL has a different scheme, the
// attribute will be dropped
->allowedMediaSchemes(['http', 'https', 'mailto'])
// specifies the allowed hosts, the attribute will be dropped if the URL
// contains a different host which is not a subdomain of the allowed host
->allowedMediaHosts(['symfony.com']) // Also allows any subdomain (i.e. www.symfony.com)
// whether to allow relative URLs (i.e. URLs without scheme and host)
->allowRelativeMedias(true)
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// if `true`, all URLs using the `http://` scheme will be converted to
// use the `https://` scheme instead. `http` still needs to be
// allowed in `allowedMediaSchemes`
->forceHttpsUrls()
// specifies the allowed URL schemes. If the URL has a different scheme, the
// attribute will be dropped
->allowedMediaSchemes(['http', 'https', 'mailto'])
// specifies the allowed hosts, the attribute will be dropped if the URL
// contains a different host which is not a subdomain of the allowed host
->allowedMediaHosts(['symfony.com']) // Also allows any subdomain (i.e. www.symfony.com)
// whether to allow relative URLs (i.e. URLs without scheme and host)
->allowRelativeMedias()
);
In order to prevent DoS attacks, by default the HTML sanitizer limits the
input length to 20000 characters (as measured by strlen($input)). All
the contents exceeding that length will be truncated. Use this option to
increase or decrease this limit:
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
# inputs longer (in characters) than this value will be truncated
max_input_length: 30000 # default: 20000
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<framework:sanitizer name="app.post_sanitizer">
<!-- inputs longer (in characters) than this value will be truncated (default: 20000) -->
<framework:max-input-length>20000</framework:max-input-length>
</framework:sanitizer>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
// inputs longer (in characters) than this value will be truncated (default: 20000)
->withMaxInputLength(20000)
;
};
.. code-block:: php-standalone
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
// inputs longer (in characters) than this value will be truncated (default: 20000)
->withMaxInputLength(20000)
);
It is possible to disable this length limit by setting the max input length to
-1. Beware that it may expose your application to DoS attacks.
Controlling the link and media URLs is done by the
:class:`Symfony\\Component\\HtmlSanitizer\\Visitor\\AttributeSanitizer\\UrlAttributeSanitizer`.
You can also implement your own attribute sanitizer, to control the value
of other attributes in the HTML. Create a class implementing
:class:`Symfony\\Component\\HtmlSanitizer\\Visitor\\AttributeSanitizer\\AttributeSanitizerInterface`
and register it as a service. After this, use with_attribute_sanitizers
to enable it for an HTML sanitizer:
.. configuration-block::
.. code-block:: yaml
# config/packages/html_sanitizer.yaml
framework:
html_sanitizer:
sanitizers:
app.post_sanitizer:
# ...
with_attribute_sanitizers:
- App\Sanitizer\CustomAttributeSanitizer
# you can also disable previously enabled custom attribute sanitizers
#without_attribute_sanitizers:
# - App\Sanitizer\CustomAttributeSanitizer
.. code-block:: xml
<!-- config/packages/html_sanitizer.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:framework="http://symfony.com/schema/dic/symfony"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd
http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
<framework:config>
<framework:html-sanitizer>
<with-attribute-sanitizer>App\Sanitizer\CustomAttributeSanitizer</with-attribute-sanitizer>
<!-- you can also disable previously enabled attribute sanitizers -->
<without-attribute-sanitizer>Symfony\Component\HtmlSanitizer\Visitor\AttributeSanitizer\UrlAttributeSanitizer</without-attribute-sanitizer>
</framework:html-sanitizer>
</framework:config>
</container>
.. code-block:: php
// config/packages/framework.php
use App\Sanitizer\CustomAttributeSanitizer;
use Symfony\Config\FrameworkConfig;
return static function (FrameworkConfig $framework): void {
$framework->htmlSanitizer()
->sanitizer('app.post_sanitizer')
->withAttributeSanitizer(CustomAttributeSanitizer::class)
// you can also disable previously enabled attribute sanitizers
//->withoutAttributeSanitizer(CustomAttributeSanitizer::class)
;
};
.. code-block:: php-standalone
use App\Sanitizer\CustomAttributeSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
$customAttributeSanitizer = new CustomAttributeSanitizer();
$postSanitizer = new HtmlSanitizer(
(new HtmlSanitizerConfig())
->withAttributeSanitizer($customAttributeSanitizer)
// you can also disable previously enabled attribute sanitizers
//->withoutAttributeSanitizer($customAttributeSanitizer)
);