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<?php
class Sanitizer {
/**
* @param array<int, string> $allowed_elements
* @param array<int, string> $disallowed_attributes
*/
private static function strip_harmful_tags(DOMDocument $doc, array $allowed_elements, $disallowed_attributes): DOMDocument {
$xpath = new DOMXPath($doc);
$entries = $xpath->query('//*');
foreach ($entries as $entry) {
if (!in_array($entry->nodeName, $allowed_elements)) {
$entry->parentNode->removeChild($entry);
}
if ($entry->hasAttributes()) {
$attrs_to_remove = array();
foreach ($entry->attributes as $attr) {
if (strpos($attr->nodeName, 'on') === 0) {
array_push($attrs_to_remove, $attr);
}
if (strpos($attr->nodeName, "data-") === 0) {
array_push($attrs_to_remove, $attr);
}
if ($attr->nodeName == 'href' && stripos($attr->value, 'javascript:') === 0) {
array_push($attrs_to_remove, $attr);
}
if (in_array($attr->nodeName, $disallowed_attributes)) {
array_push($attrs_to_remove, $attr);
}
}
foreach ($attrs_to_remove as $attr) {
$entry->removeAttributeNode($attr);
}
}
}
return $doc;
}
public static function iframe_whitelisted(DOMElement $entry): bool {
$src = parse_url($entry->getAttribute("src"), PHP_URL_HOST);
if (!empty($src))
return PluginHost::getInstance()->run_hooks_until(PluginHost::HOOK_IFRAME_WHITELISTED, true, $src);
return false;
}
private static function is_prefix_https(): bool {
return parse_url(Config::get_self_url(), PHP_URL_SCHEME) == 'https';
}
/**
* @param array<int, string>|null $highlight_words Words to highlight in the HTML output.
*
* @return false|string The HTML, or false if an error occurred.
*/
public static function sanitize(string $str, ?bool $force_remove_images = false, int $owner = null, string $site_url = null, array $highlight_words = null, int $article_id = null) {
$scope = Tracer::start(__METHOD__);
if (!$owner && isset($_SESSION["uid"]))
$owner = $_SESSION["uid"];
$res = trim($str); if (!$res) return '';
$doc = new DOMDocument();
$doc->loadHTML('<?xml encoding="UTF-8">' . $res);
$xpath = new DOMXPath($doc);
// is it a good idea to possibly rewrite urls to our own prefix?
// $rewrite_base_url = $site_url ? $site_url : Config::get_self_url();
$rewrite_base_url = $site_url ? $site_url : "http://domain.invalid/";
$entries = $xpath->query('(//a[@href]|//img[@src]|//source[@srcset|@src]|//video[@poster])');
foreach ($entries as $entry) {
if ($entry->hasAttribute('href')) {
$entry->setAttribute('href',
UrlHelper::rewrite_relative($rewrite_base_url, $entry->getAttribute('href'), $entry->tagName, "href"));
$entry->setAttribute('rel', 'noopener noreferrer');
$entry->setAttribute("target", "_blank");
}
if ($entry->hasAttribute('src')) {
$entry->setAttribute('src',
UrlHelper::rewrite_relative($rewrite_base_url, $entry->getAttribute('src'), $entry->tagName, "src"));
}
if ($entry->nodeName == 'img') {
$entry->setAttribute('referrerpolicy', 'no-referrer');
$entry->setAttribute('loading', 'lazy');
}
if ($entry->hasAttribute('srcset')) {
$matches = RSSUtils::decode_srcset($entry->getAttribute('srcset'));
for ($i = 0; $i < count($matches); $i++) {
$matches[$i]["url"] = UrlHelper::rewrite_relative($rewrite_base_url, $matches[$i]["url"]);
}
$entry->setAttribute("srcset", RSSUtils::encode_srcset($matches));
}
if ($entry->hasAttribute('poster')) {
$entry->setAttribute('poster',
UrlHelper::rewrite_relative($rewrite_base_url, $entry->getAttribute('poster'), $entry->tagName, "poster"));
}
if ($entry->hasAttribute('src') &&
($owner && get_pref(Prefs::STRIP_IMAGES, $owner)) || $force_remove_images || ($_SESSION["bw_limit"] ?? false)) {
$p = $doc->createElement('p');
$a = $doc->createElement('a');
$a->setAttribute('href', $entry->getAttribute('src'));
$a->appendChild(new DOMText($entry->getAttribute('src')));
$a->setAttribute('target', '_blank');
$a->setAttribute('rel', 'noopener noreferrer');
$p->appendChild($a);
if ($entry->nodeName == 'source') {
if ($entry->parentNode && $entry->parentNode->parentNode)
$entry->parentNode->parentNode->replaceChild($p, $entry->parentNode);
} else if ($entry->nodeName == 'img') {
if ($entry->parentNode)
$entry->parentNode->replaceChild($p, $entry);
}
}
}
$entries = $xpath->query('//iframe');
foreach ($entries as $entry) {
if (!self::iframe_whitelisted($entry)) {
$entry->setAttribute('sandbox', 'allow-scripts');
} else {
if (self::is_prefix_https()) {
$entry->setAttribute("src",
str_replace("http://", "https://",
$entry->getAttribute("src")));
}
}
}
$allowed_elements = array('a', 'abbr', 'address', 'acronym', 'audio', 'article', 'aside',
'b', 'bdi', 'bdo', 'big', 'blockquote', 'body', 'br',
'caption', 'cite', 'center', 'code', 'col', 'colgroup',
'data', 'dd', 'del', 'details', 'description', 'dfn', 'div', 'dl', 'font',
'dt', 'em', 'footer', 'figure', 'figcaption',
'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'header', 'hr', 'html', 'i',
'img', 'ins', 'kbd', 'li', 'main', 'mark', 'nav', 'noscript',
'ol', 'p', 'picture', 'pre', 'q', 'ruby', 'rp', 'rt', 's', 'samp', 'section',
'small', 'source', 'span', 'strike', 'strong', 'sub', 'summary',
'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'time',
'tr', 'track', 'tt', 'u', 'ul', 'var', 'wbr', 'video', 'xml:namespace' );
if ($_SESSION['hasSandbox'] ?? false) $allowed_elements[] = 'iframe';
$disallowed_attributes = array('id', 'style', 'class', 'width', 'height', 'allow');
PluginHost::getInstance()->chain_hooks_callback(PluginHost::HOOK_SANITIZE,
function ($result) use (&$doc, &$allowed_elements, &$disallowed_attributes) {
if (is_array($result)) {
$doc = $result[0];
$allowed_elements = $result[1];
$disallowed_attributes = $result[2];
} else {
$doc = $result;
}
},
$doc, $site_url, $allowed_elements, $disallowed_attributes, $article_id);
$doc->removeChild($doc->firstChild); //remove doctype
$doc = self::strip_harmful_tags($doc, $allowed_elements, $disallowed_attributes);
$entries = $xpath->query('//iframe');
foreach ($entries as $entry) {
$div = $doc->createElement('div');
$div->setAttribute('class', 'embed-responsive');
$entry->parentNode->replaceChild($div, $entry);
$div->appendChild($entry);
}
if (is_array($highlight_words)) {
foreach ($highlight_words as $word) {
// http://stackoverflow.com/questions/4081372/highlight-keywords-in-a-paragraph
$elements = $xpath->query("//*/text()");
foreach ($elements as $child) {
$fragment = $doc->createDocumentFragment();
$text = $child->textContent;
while (($pos = mb_stripos($text, $word)) !== false) {
$fragment->appendChild(new DOMText(mb_substr($text, 0, (int)$pos)));
$word = mb_substr($text, (int)$pos, mb_strlen($word));
$highlight = $doc->createElement('span');
$highlight->appendChild(new DOMText($word));
$highlight->setAttribute('class', 'highlight');
$fragment->appendChild($highlight);
$text = mb_substr($text, $pos + mb_strlen($word));
}
if (!empty($text)) $fragment->appendChild(new DOMText($text));
$child->parentNode->replaceChild($fragment, $child);
}
}
}
$res = $doc->saveHTML();
$scope->close();
/* strip everything outside of <body>...</body> */
$res_frag = array();
if (preg_match('/<body>(.*)<\/body>/is', $res, $res_frag)) {
return $res_frag[1];
} else {
return $res;
}
}
}
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