Fixes #6953 LRC replace DOM output with regex injection (#6954)

Co-authored-by: Gael Robin <robin.gael@gmail.com>

inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/Dom.php

@@ -10,6 +10,24 @@ class Dom implements ProcessorInterface {
 
 	use HelperTrait;
 
+	/**
+	 * Number of injects hashes.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $count;
+
+	/**
+	 * Maximum number of hashes to inject.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $max_hashes;
+
 	/**
 	 * Add hashes to the HTML elements
 	 *
@@ -44,27 +62,35 @@ public function add_hashes( $html ) {
 			return $html;
 		}
 
-		$this->add_hash_to_element( $body, $this->get_depth() );
+		$this->max_hashes = $this->get_max_tags();
+		$this->count      = 0;
 
-		return $dom->saveHTML();
+		return $this->add_hash_to_element( $body, $this->get_depth(), $html );
 	}
 
 	/**
 	 * Add a hash to the element and its children.
 	 *
 	 * @param \DOMElement $element The element to add the hash to.
 	 * @param int         $depth   The depth of the recursion.
+	 * @param string      $html    The HTML content.
+	 *
+	 * @return string
 	 */
-	private function add_hash_to_element( $element, $depth ) {
+	private function add_hash_to_element( $element, $depth, $html ) {
 		if ( $depth < 0 ) {
-			return;
+			return $html;
 		}
 
 		$processed_tags = $this->get_processed_tags();
 
-		static $count = 0;
-
 		foreach ( $element->childNodes as $child ) { // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
+
+			if ( $this->count >= $this->max_hashes ) {
+				Logger::warning( 'Stopping LRC hash injection as max_hashes is reached.', [ 'LazyRenderContent' ] );
+				return $html;
+			}
+
 			if ( ! $child instanceof \DOMElement ) {
 				continue;
 			}
@@ -81,15 +107,32 @@ private function add_hash_to_element( $element, $depth ) {
 			$child_html       = $child->ownerDocument->saveHTML( $child ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
 			$opening_tag_html = strstr( $child_html, '>', true ) . '>';
 
-			$hash = md5( $opening_tag_html . $count );
+			$hash = md5( $opening_tag_html . $this->count );
 
-			++$count;
+			++$this->count;
 
-			// Add the data-rocket-location-hash attribute.
-			$child->setAttribute( 'data-rocket-location-hash', $hash );
+			// Inject the hash as an attribute in the opening tag.
+			$replace = preg_replace( '/' . $child->tagName . '/is', '$0 data-rocket-location-hash="' . $hash . '"', $opening_tag_html, 1 ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
+			if ( is_null( $replace ) ) {
+				continue;
+			}
+			// Replace the opening tag in the HTML by the manipulated one
+			// If DOMDocument automatically modified the original element, we might not find it in the HTML.
+			// Known issue: if there is an element with the exact same opening tag before in the HTML that did not receive a hash, it will replaced instead of the correct element in the HTML.
+			$element_replacements = 0;
+			$modified_html        = preg_replace( '/' . preg_quote( $opening_tag_html, '/' ) . '/', $replace, $html, 1, $element_replacements );
+			if ( $element_replacements < 1 ) {
+				Logger::warning( 'Opening tag from DOMDocument not found in original HTML.', [ 'LazyRenderContent' ] );
+			}
+			if ( is_null( $modified_html ) ) {
+				continue;
+			}
+			$html = $modified_html;
 
 			// Recursively process child elements.
-			$this->add_hash_to_element( $child, $depth - 1 );
+			$html = $this->add_hash_to_element( $child, $depth - 1, $html );
 		}
+
+		return $html;
 	}
 }

inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/HelperTrait.php

@@ -8,6 +8,8 @@ trait HelperTrait {
 	/**
 	 * Get filtered elements depth.
 	 *
+	 * @since 3.17
+	 *
 	 * @return int
 	 */
 	protected function get_depth() {
@@ -20,6 +22,23 @@ protected function get_depth() {
 		return wpm_apply_filters_typed( 'integer', 'rocket_lrc_depth', 2 );
 	}
 
+	/**
+	 * Get filtered element maximum count.
+	 *
+	 * @since 3.17
+	 *
+	 * @return int
+	 */
+	protected function get_max_tags() {
+		/**
+		 * Filter the maximal number of processed tags.
+		 * High values allow to process more elements but expose to a risk of performance issue because of the regex replacement process.
+		 *
+		 * @param int $depth Depth value.
+		 */
+		return wpm_apply_filters_typed( 'integer', 'rocket_lrc_max_hashes', 200 );
+	}
+
 	/**
 	 * Get processed tags.
 	 *
@@ -29,6 +48,8 @@ protected function get_processed_tags() {
 		/**
 		 * Filter the processed element tags.
 		 *
+		 * @since 3.17
+		 *
 		 * @param array|string[] $tags Tags to be processed.
 		 */
 		$tags = wpm_apply_filters_typed(

inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/Regex.php

@@ -9,6 +9,24 @@ class Regex implements ProcessorInterface {
 
 	use HelperTrait;
 
+	/**
+	 * Number of injects hashes.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $count;
+
+	/**
+	 * Maximum number of hashes to inject.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $max_hashes;
+
 	/**
 	 * Add hashes to the HTML elements
 	 *
@@ -25,6 +43,9 @@ public function add_hashes( $html ) {
 			return $html;
 		}
 
+		$this->max_hashes = $this->get_max_tags();
+		$this->count      = 0;
+
 		return $this->add_hash_to_element( $html, $matches[0] );
 	}
 
@@ -47,15 +68,19 @@ private function add_hash_to_element( $html, $element ) {
 			return $html;
 		}
 
-		$count = 0;
-
 		foreach ( $matches as $child ) {
+
+			if ( $this->count >= $this->max_hashes ) {
+				Logger::warning( 'Stopping LRC hash injection as max_hashes is reached.', [ 'LazyRenderContent' ] );
+				return $html;
+			}
+
 			// Calculate the hash of the opening tag.
 			$opening_tag_html = strstr( $child[0], '>', true ) . '>';
 
-			$hash = md5( $opening_tag_html . $count );
+			$hash = md5( $opening_tag_html . $this->count );
 
-			++$count;
+			++$this->count;
 
 			// Add the data-rocket-location-hash attribute.
 			$replace = preg_replace( '/' . $child[1] . '/is', '$0 data-rocket-location-hash="' . $hash . '"', $child[0], 1 );

inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/SimpleHtmlDom.php

@@ -12,6 +12,24 @@ class SimpleHtmlDom implements ProcessorInterface {
 
 	use HelperTrait;
 
+	/**
+	 * Number of injects hashes.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $count;
+
+	/**
+	 * Maximum number of hashes to inject.
+	 *
+	 * @since 3.17
+	 *
+	 * @var int
+	 */
+	private $max_hashes;
+
 	/**
 	 * Add hashes to the HTML elements
 	 *
@@ -30,6 +48,9 @@ public function add_hashes( $html ) {
 			return $html;
 		}
 
+		$this->max_hashes = $this->get_max_tags();
+		$this->count      = 0;
+
 		$this->add_hash_to_element( $body, $this->get_depth() );
 
 		return $dom->save();
@@ -48,9 +69,13 @@ private function add_hash_to_element( $element, $depth ) {
 
 		$processed_tags = $this->get_processed_tags();
 
-		static $count = 0;
-
 		foreach ( $element->childNodes() as $child ) {
+
+			if ( $this->count >= $this->max_hashes ) {
+				Logger::warning( 'Stopping LRC hash injection as max_hashes is reached.', [ 'LazyRenderContent' ] );
+				return;
+			}
+
 			if ( ! in_array( strtoupper( $child->getTag() ), $processed_tags, true ) ) {
 				continue;
 			}
@@ -59,9 +84,9 @@ private function add_hash_to_element( $element, $depth ) {
 			$child_html       = $child->html();
 			$opening_tag_html = strstr( $child_html, '>', true ) . '>';
 
-			$hash = md5( $opening_tag_html . $count );
+			$hash = md5( $opening_tag_html . $this->count );
 
-			++$count;
+			++$this->count;
 
 			// Add the data-rocket-location-hash attribute.
 			$child->setAttribute( 'data-rocket-location-hash', $hash );

tests/Fixtures/inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/expected.html

@@ -7,7 +7,7 @@
 			<article data-rocket-location-hash="d1f41b6001aa95d1577259dd681a9b19">
 				<header data-rocket-location-hash="fbfcccd11db41b93d3d0676c9e14fdc8">
 					<h1>Original</h1>
-					<div></div>
+					<div attribute-added-to-bypass-dom-processor-known-issue="1"></div>
 				</header>
 				<section data-rocket-location-hash="75202dec0fcc2df72399263306a2e2e7">
 					<h2>Text</h2>

tests/Fixtures/inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/expectedRegex.html

@@ -7,7 +7,7 @@
 			<article data-rocket-location-hash="d1f41b6001aa95d1577259dd681a9b19">
 				<header data-rocket-location-hash="fbfcccd11db41b93d3d0676c9e14fdc8">
 					<h1>Original</h1>
-					<div data-rocket-location-hash="7b16eca0652d4703f83ba63e304f2030"></div>
+					<div data-rocket-location-hash="d9527fe8d9073f13915c4ae1183acd6a" attribute-added-to-bypass-dom-processor-known-issue="1"></div>
 				</header>
 				<section data-rocket-location-hash="372b731e1cb055b2c1a710227f2f6cd6">
 					<h2>Text</h2>

tests/Fixtures/inc/Engine/Optimization/LazyRenderContent/Frontend/Processor/original.html

@@ -7,7 +7,7 @@
 			<article>
 				<header>
 					<h1>Original</h1>
-					<div></div>
+					<div attribute-added-to-bypass-dom-processor-known-issue="1"></div>
 				</header>
 				<section>
 					<h2>Text</h2>

tests/Fixtures/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/add_hashes.php

@@ -22,6 +22,39 @@
 			'expected' => [
 				'html' => file_get_contents( WP_ROCKET_TESTS_FIXTURES_DIR . '/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/html/expected.php' ),
 			]
+		],
+		'shouldStopAt200Hashes' => [
+			'config' => [
+				'row' => [
+					'url' => 'http://example.org/',
+					'is_mobile' => 0,
+					'below_the_fold' => json_encode(
+						[]
+					),
+					'status' => 'completed'
+				],
+				'html' => file_get_contents( WP_ROCKET_TESTS_FIXTURES_DIR . '/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/html/long_original.php' ),
+			],
+			'expected' => [
+				'html' => file_get_contents( WP_ROCKET_TESTS_FIXTURES_DIR . '/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/html/long_expected_200_hashes.php' ),
+			]
+		],
+		'shouldStopAtFilteredMaxHashes' => [
+			'config' => [
+				'row' => [
+					'url' => 'http://example.org/',
+					'is_mobile' => 0,
+					'below_the_fold' => json_encode(
+						[]
+					),
+					'status' => 'completed'
+				],
+				'html' => file_get_contents( WP_ROCKET_TESTS_FIXTURES_DIR . '/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/html/long_original.php' ),
+				'max_hashes' => 150,
+			],
+			'expected' => [
+				'html' => file_get_contents( WP_ROCKET_TESTS_FIXTURES_DIR . '/inc/Engine/Optimization/LazyRenderContent/Frontend/Subscriber/html/long_expected_150_hashes.php' ),
+			]
 		]
 	]
 ];