2021-09-03 18:32:42 -04:00
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<?php
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namespace BookStack\Util;
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use DOMDocument;
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use DOMElement;
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use DOMNodeList;
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use DOMXPath;
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class HtmlNonceApplicator
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{
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2021-09-04 08:57:04 -04:00
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protected static $placeholder = '[CSP_NONCE_VALUE]';
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2021-09-03 18:32:42 -04:00
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/**
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2021-09-04 08:57:04 -04:00
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* Prepare the given HTML content with nonce attributes including a placeholder
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* value which we can target later.
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2021-09-03 18:32:42 -04:00
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*/
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2021-09-04 08:57:04 -04:00
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public static function prepare(string $html): string
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2021-09-03 18:32:42 -04:00
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{
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if (empty($html)) {
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return $html;
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}
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2021-09-12 11:19:17 -04:00
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$html = '<?xml encoding="utf-8" ?><body>' . $html . '</body>';
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2021-09-03 18:32:42 -04:00
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libxml_use_internal_errors(true);
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$doc = new DOMDocument();
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2021-09-12 11:19:17 -04:00
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$doc->loadHTML($html, LIBXML_SCHEMA_CREATE);
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2021-09-03 18:32:42 -04:00
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$xPath = new DOMXPath($doc);
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// Apply to scripts
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$scriptElems = $xPath->query('//script');
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2021-09-04 08:57:04 -04:00
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static::addNonceAttributes($scriptElems, static::$placeholder);
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2021-09-03 18:32:42 -04:00
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// Apply to styles
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$styleElems = $xPath->query('//style');
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2021-09-04 08:57:04 -04:00
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static::addNonceAttributes($styleElems, static::$placeholder);
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2021-09-03 18:32:42 -04:00
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$returnHtml = '';
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$topElems = $doc->documentElement->childNodes->item(0)->childNodes;
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foreach ($topElems as $child) {
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2021-09-06 17:19:06 -04:00
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$content = $doc->saveHTML($child);
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2021-09-05 18:52:39 -04:00
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$returnHtml .= $content;
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2021-09-03 18:32:42 -04:00
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}
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return $returnHtml;
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}
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2021-09-04 08:57:04 -04:00
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/**
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* Apply the give nonce value to the given prepared HTML.
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*/
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public static function apply(string $html, string $nonce): string
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{
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return str_replace(static::$placeholder, $nonce, $html);
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}
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protected static function addNonceAttributes(DOMNodeList $nodes, string $attrValue): void
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{
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/** @var DOMElement $node */
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foreach ($nodes as $node) {
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$node->setAttribute('nonce', $attrValue);
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2021-09-03 18:32:42 -04:00
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}
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}
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}
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