WIP: HTML API: Add fuzz tester

tests/phpunit/tests/html-api/wpHtml-parserFuzzing.php

@@ -0,0 +1,232 @@
+<?php
+/**
+ * Fuzz tests covering HTML API parsing.
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ *
+ * @since 7.1.0
+ */
+
+/**
+ * @group html-api-fuzzing
+ *
+ * @coversDefaultClass WP_HTML_Processor
+ */
+class Tests_HtmlApi_ParserFuzzing extends WP_UnitTestCase {
+	private $seed;
+
+	private $end_at;
+
+	public function set_up() {
+		parent::set_up();
+
+		$this->seed = intval( getenv( 'FUZZ_SEED' ) );
+		$duration   = intval( getenv( 'FUZZ_DURATION' ) );
+
+		if ( 0 === $this->seed && $duration <= 0 ) {
+			$this->markTestSkipped( 'Fuzz test only runs when given a positive duration or specific seed value.' );
+		}
+
+		$this->end_at = time() + $duration;
+	}
+
+	/**
+	 * Runs the fuzzing suite to verify HTML API parsing.
+	 *
+	 * @dataProvider data_seeds
+	 *
+	 * @param int $seed Randomization seed for reproducing test.
+	 */
+	public function test_run_fuzzer( int $seed ): void {
+		static $test_catalog = self::fuzz_tests();
+
+		srand( $seed );
+
+		$fuzz_test    = $test_catalog[ array_rand( $test_catalog ) ];
+		call_user_func( $fuzz_test );
+	}
+
+	public static function data_seeds(): Generator {
+		$end_at = time() + intval( getenv( 'FUZZ_DURATION' ) );
+		$budget = 5;
+
+		while ( time() < $end_at && --$budget ) {
+			$seed = random_int( 0, 4294967296 );
+			yield $seed => array( $seed );
+		}
+	}
+
+	private static function fuzz_tests(): array {
+		return array(
+			'self::fuzz_parses_tag',
+		);
+	}
+
+	/**
+	 * Verifies parsing of tag openers.
+	 *
+	 * @param string $tag_opener Complete HTML snippet with an opening tag.
+	 */
+	public function fuzz_parses_tag(): void {
+		$tag_opener = self::make_tag_opener();
+		$dom        = self::dom( $tag_opener );
+
+//		fwrite( STDERR, "\n\e[33mAnalyzing \e[32m{$tag_opener}\e[m" );
+
+		/** @var DOM\HtmlElement $tag */
+		$tag = $dom->childNodes[0];
+
+		$processor = WP_HTML_Processor::create_fragment( $tag_opener );
+//		$processor = new WP_HTML_Tag_Processor( $tag_opener );
+		$this->assertTrue(
+			$processor->next_token(),
+			'Should have found a complete token in the test input'
+		);
+
+		$this->assertSame(
+			'#tag',
+			$processor->get_token_type(),
+			'Should have found a tag as the test input token.'
+		);
+
+		$this->assertSame(
+			$tag->nodeName,
+			$processor->get_tag(),
+			'Should have read expected tag name from input.'
+		);
+
+		foreach ( $tag->getAttributeNames() as $attribute_name ) {
+			$expected = $tag->getAttribute( $attribute_name );
+			$actual   = $processor->get_attribute( $attribute_name );
+
+			$this->assertTrue(
+				isset( $actual ),
+				"Expected to find attribute '{$attribute_name}' on test input."
+			);
+
+			if ( '' === $expected ) {
+				$this->assertTrue(
+					$actual,
+					"Should have found boolean attribute '{$attribute_name}'."
+				);
+			} else {
+				$this->assertSame(
+					$expected,
+					$actual,
+					"Should have detected and properly decoded attribute '{$attribute_name}'."
+				);
+			}
+		}
+	}
+
+	public static function make_tag_opener(): string {
+		$tag_name  = self::make_html_tag_name();
+		$arg_count = random_int( 0, 8 );
+
+		if ( 0 === $arg_count ) {
+			return "<{$tag_name}>";
+		}
+
+		$tag   = "<{$tag_name}";
+		$attrs = array();
+		for ( $i = 0; $i < $arg_count; $i++ ) {
+			$name    = self::make_attribute_name();
+			$attrs[] = self::make_ws() . $name;
+
+			if ( random_int( 0, 100 ) < 10 ) {
+				$attrs[] = self::make_ws() . $name;
+				if ( random_int( 0, 100 ) < 50 ) {
+					$attrs[] = self::make_ws() . strtoupper( $name );
+				}
+			}
+		}
+
+		shuffle( $attrs );
+		$tag .= implode( '', $attrs );
+
+		$ws     = random_int( 0, 100 ) < 10 ? self::make_ws() : '';
+		$closer = random_int( 0, 100 ) < 20 ? '/' : '';
+
+		return "{$tag}{$ws}{$closer}>";
+	}
+
+	public static function make_ws(): string {
+		$length = random_int( 1, 4 );
+		$ws     = '';
+
+		for ( $i = 0; $i < $length; $i++ ) {
+			$ws .= " \t\r\n\f"[ random_int( 0, 4 ) ];
+		}
+
+		return $ws;
+	}
+
+	public static function make_attribute_name(): string {
+		$choice = random_int( 0, 100 );
+
+		if ( $choice < 80 ) {
+			return self::make_typical_attribute_name();
+		}
+
+		return self::make_random_attribute_name();
+	}
+
+	public static function make_typical_attribute_name(): string {
+		$attribute_names = array(
+			'alt',
+			'id',
+			'src',
+			'source',
+			'class',
+			'data-post-id',
+		);
+
+		return $attribute_names[ array_rand( $attribute_names ) ];
+	}
+
+	public static function make_random_attribute_name(): string {
+		$forbidden = "=/> \t\f\r\n";
+
+		$name   = '';
+		$length = random_int( 1, 14 );
+		for ( $i = 0; $i < $length; $i++ ) {
+			$c = mb_chr( random_int( 0, 1114111 ) );
+			if ( str_contains( $forbidden, $c ) ) {
+				--$i;
+				continue;
+			}
+
+			$name .= $c;
+		}
+
+		return $name;
+	}
+
+	public static function make_html_tag_name(): string {
+		$html_tag_names = array(
+			'a',
+			'abbr',
+			'article',
+			'b',
+			'div',
+			'em',
+			'i',
+			'link',
+			'main',
+			'strong',
+			'template',
+			'section',
+		);
+
+		return $html_tag_names[ array_rand( $html_tag_names ) ];
+	}
+
+	private static function dom( string $html ) {
+		if ( ! ( class_exists( 'DOM\HTMLDocument' ) && defined( 'LIBXML_NOERROR' ) && defined( 'LIBXML_HTML_NOIMPLIED' ) ) ) {
+			throw new Error( 'Cannot run tests without DOM support.' );
+		}
+
+		return DOM\HTMLDocument::createFromString( $html, LIBXML_NOERROR | LIBXML_HTML_NOIMPLIED );
+	}
+}