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Add disallow_uri_protocols() function for disallowing javascript: URIs #65

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Add disallow_uri_protocols() function for disallowing javascript: URIs #65

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61 changes: 61 additions & 0 deletions src/Sanitize.php
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,8 @@ class Sanitize implements RegistryAware
public $allow_data_attr = true;
/** @var bool */
public $allow_aria_attr = true;
/** @var string[] */
public $disallowed_uri_protocols = ['javascript'];
/** @var array<string, array<string, string>> */
public $add_attributes = ['audio' => ['preload' => 'none'], 'iframe' => ['sandbox' => 'allow-scripts allow-same-origin'], 'video' => ['preload' => 'none']];
/** @var bool */
Expand Down Expand Up @@ -280,6 +282,14 @@ public function allow_aria_attr(bool $allow = true): void
$this->allow_aria_attr = $allow;
}

/**
* @param string[] $protocols List of protocols to disallow
*/
public function disallow_uri_protocols(array $protocols = ['javascript']): void
{
$this->disallowed_uri_protocols = $protocols;
}

/**
* @return void
*/
Expand Down Expand Up @@ -541,6 +551,12 @@ public function sanitize(string $data, int $type, string $base = '')
$this->replace_urls($document, $element, $attributes);
}

if ($this->disallowed_uri_protocols) {
foreach ($this->disallowed_uri_protocols as $protocol) {
$this->strip_uri_protocol($xpath, $protocol);
}
}

// If image handling (caching, etc.) is enabled, cache and rewrite all the image tags.
if ($this->image_handler !== '' && $this->enable_cache) {
$images = $document->getElementsByTagName('img');
Expand Down Expand Up @@ -742,6 +758,51 @@ protected function enforce_allowed_html_nodes(\DOMNode $element, bool $allow_dat
}
}

private function extract_protocol(string $uri): string
{
if (!str_contains($uri, ':')) {
return '';
}
$extracted_protocol = strtolower(preg_replace(
'/[\x01-\x20\s]/',
'',
rawurldecode(explode(':', $uri)[0])
) ?? '');
return $extracted_protocol;
}

/**
* Remove a disallowed URI protocol
*/
protected function strip_uri_protocol(\DOMXPath $xpath, string $protocol): void
{
$protocol = strtolower($protocol);
$elements = $xpath->query('.//a[@href]|.//iframe[@src]|.//math//*[@href]');

if ($elements === false) {
throw new \SimplePie\Exception(sprintf(
'%s(): Possibly malformed expression',
__METHOD__
), 1);
}

foreach ($elements as $element) {
if (!($element instanceof \DOMElement)) {
continue;
}

$href = $element->getAttribute('href');
$src = $element->getAttribute('src');

if ($element->hasAttribute('href') && $this->extract_protocol($href) === $protocol) {
$element->setAttribute('href', 'unsafe:' . $href);
}
if ($element->hasAttribute('src') && $this->extract_protocol($src) === $protocol) {
$element->setAttribute('src', 'unsafe:' . $src);
}
}
}

/**
* @param int-mask-of<SimplePie::CONSTRUCT_*> $type
* @return void
Expand Down
15 changes: 15 additions & 0 deletions src/SimplePie.php
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Original file line number Diff line number Diff line change
Expand Up @@ -692,6 +692,13 @@ class SimplePie
*/
public $allow_aria_attr = true;

/**
* @var string[] Stores array of disallowed URI protocols
* @see SimplePie::disallow_uri_protocols()
* @access private
*/
public $disallowed_uri_protocols = ['javascript'];

/**
* @var bool Should we throw exceptions, or use the old-style error property?
* @access private
Expand Down Expand Up @@ -1589,6 +1596,14 @@ public function allow_aria_attr(bool $allow = true): void
$this->sanitize->allow_aria_attr($allow);
}

/**
* @param string[] $protocols List of protocols to disallow
*/
public function disallow_uri_protocols(array $protocols = ['javascript']): void
{
$this->sanitize->disallow_uri_protocols($protocols);
}

/**
* @return void
*/
Expand Down