fix: prevent unsafe url rewrites

src/Url/UrlTransformer.php

@@ -4,26 +4,59 @@ namespace WPContentSync\Url;
 
 final class UrlTransformer {
 	public function transformString( string $value, UrlMappingCollection $mappings ): string {
-		$transformed = $value;
+		$replacements = array();
 
 		foreach ( $mappings->all() as $mapping ) {
-			$transformed = $this->replaceMapping( $transformed, $mapping );
+			$replacements = array_merge( $replacements, $this->replacementsForMapping( $mapping ) );
 		}
 
-		return $transformed;
+		if ( array() === $replacements ) {
+			return $value;
+		}
+
+		return preg_replace_callback(
+			$this->replacementPattern( array_keys( $replacements ) ),
+			static function ( array $matches ) use ( $replacements ): string {
+				return $replacements[ $matches[0] ];
+			},
+			$value
+		) ?? $value;
 	}
 
-	private function replaceMapping( string $value, UrlMapping $mapping ): string {
+	/**
+	 * @return array<string, string>
+	 */
+	private function replacementsForMapping( UrlMapping $mapping ): array {
 		$source      = $mapping->sourceUrl();
 		$destination = $mapping->destinationUrl();
 
-		$replacements = array(
+		return array(
 			$source                              => $destination,
 			str_replace( '&', '&amp;', $source ) => str_replace( '&', '&amp;', $destination ),
 			$this->toProtocolRelative( $source ) => $this->toProtocolRelative( $destination ),
+			str_replace( '&', '&amp;', $this->toProtocolRelative( $source ) ) => str_replace( '&', '&amp;', $this->toProtocolRelative( $destination ) ),
+		);
+	}
+
+	/**
+	 * @param array<int, string> $sources Replacement sources.
+	 */
+	private function replacementPattern( array $sources ): string {
+		usort(
+			$sources,
+			static function ( string $left, string $right ): int {
+				return strlen( $right ) <=> strlen( $left );
+			}
 		);
 
-		return strtr( $value, $replacements );
+		$quoted = array_map(
+			static function ( string $source ): string {
+				return preg_quote( $source, '~' );
+			},
+			$sources
+		);
+
+		return '~(?<![A-Za-z0-9.-])(?:' . implode( '|', $quoted ) . ')(?![A-Za-z0-9.-])~';
 	}
 
 	private function toProtocolRelative( string $url ): string {

tests/Unit/Url/UrlTransformerTest.php

@@ -81,4 +81,65 @@ class UrlTransformerTest extends TestCase {
 			$transformer->transformString( 'https://example.test https://cdn.example.test/image.jpg', $mappings )
 		);
 	}
+
+	public function test_it_does_not_cascade_mapping_destinations_into_other_sources(): void {
+		$transformer = new UrlTransformer();
+		$mappings    = new UrlMappingCollection(
+			array(
+				new UrlMapping( 'https://a.example.test', 'https://b.example.test' ),
+				new UrlMapping( 'https://b.example.test', 'https://c.example.test' ),
+			)
+		);
+
+		self::assertSame(
+			'https://b.example.test/page https://c.example.test/page',
+			$transformer->transformString( 'https://a.example.test/page https://b.example.test/page', $mappings )
+		);
+	}
+
+	public function test_it_does_not_rewrite_partial_host_matches(): void {
+		$transformer = new UrlTransformer();
+		$mappings    = new UrlMappingCollection(
+			array(
+				new UrlMapping( 'https://example.test', 'https://staging.example.test' ),
+			)
+		);
+
+		self::assertSame(
+			'https://example.test.evil/path https://staging.example.test/path',
+			$transformer->transformString(
+				'https://example.test.evil/path https://example.test/path',
+				$mappings
+			)
+		);
+	}
+
+	public function test_it_prefers_more_specific_overlapping_mappings(): void {
+		$transformer = new UrlTransformer();
+		$mappings    = new UrlMappingCollection(
+			array(
+				new UrlMapping( 'https://example.test', 'https://staging.example.test' ),
+				new UrlMapping( 'https://example.test/uploads', 'https://media.staging.example.test/uploads' ),
+			)
+		);
+
+		self::assertSame(
+			'https://media.staging.example.test/uploads/image.jpg',
+			$transformer->transformString( 'https://example.test/uploads/image.jpg', $mappings )
+		);
+	}
+
+	public function test_it_rewrites_escaped_protocol_relative_urls(): void {
+		$transformer = new UrlTransformer();
+		$mappings    = new UrlMappingCollection(
+			array(
+				new UrlMapping( 'https://example.test/path?a=1&b=2', 'https://staging.example.test/path?a=1&b=2' ),
+			)
+		);
+
+		self::assertSame(
+			'//staging.example.test/path?a=1&b=2',
+			$transformer->transformString( '//example.test/path?a=1&b=2', $mappings )
+		);
+	}
 }