Add support for amp-live-list requests

includes/class-amp-theme-support.php

@@ -65,6 +65,15 @@ class AMP_Theme_Support {
 		'attachment',
 	);
 
+	/**
+	 * AMP-specific query vars that were purged.
+	 *
+	 * @since 0.7
+	 * @see AMP_Theme_Support::purge_amp_query_vars()
+	 * @var string[]
+	 */
+	public static $purged_amp_query_vars = array();
+
 	/**
 	 * Initialize.
 	 */
@@ -93,6 +102,7 @@ public static function init() {
 			self::register_paired_hooks();
 		}
 
+		self::purge_amp_query_vars();
 		self::register_hooks();
 		self::$embed_handlers    = self::register_content_embed_handlers();
 		self::$sanitizer_classes = amp_get_content_sanitizers();
@@ -183,6 +193,64 @@ public static function register_hooks() {
 		// @todo Add character conversion.
 	}
 
+	/**
+	 * Remove query vars that come in requests such as for amp-live-list.
+	 *
+	 * WordPress should generally not respond differently to requests when these parameters
+	 * are present. In some cases, when a query param such as __amp_source_origin is present
+	 * then it would normally get included into pagination links generated by get_pagenum_link().
+	 * The whitelist sanitizer empties out links that contain this string as it matches the
+	 * blacklisted_value_regex. So by preemptively scrubbing any reference to these query vars
+	 * we can ensure that WordPress won't end up referencing them in any way.
+	 *
+	 * @since 0.7
+	 */
+	public static function purge_amp_query_vars() {
+		$query_vars = array(
+			'__amp_source_origin',
+			'amp_latest_update_time',
+		);
+
+		// Scrub input vars.
+		foreach ( $query_vars as $query_var ) {
+			if ( ! isset( $_GET[ $query_var ] ) ) { // phpcs:ignore
+				continue;
+			}
+			self::$purged_amp_query_vars[ $query_var ] = wp_unslash( $_GET[ $query_var ] ); // phpcs:ignore
+			unset( $_REQUEST[ $query_var ], $_GET[ $query_var ] );
+			$scrubbed = true;
+		}
+
+		if ( isset( $scrubbed ) ) {
+			$build_query = function( $query ) use ( $query_vars ) {
+				$pattern = '/^(' . join( '|', $query_vars ) . ')(?==|$)/';
+				$pairs   = array();
+				foreach ( explode( '&', $query ) as $pair ) {
+					if ( ! preg_match( $pattern, $pair ) ) {
+						$pairs[] = $pair;
+					}
+				}
+				return join( '&', $pairs );
+			};
+
+			// Scrub QUERY_STRING.
+			if ( ! empty( $_SERVER['QUERY_STRING'] ) ) {
+				$_SERVER['QUERY_STRING'] = $build_query( $_SERVER['QUERY_STRING'] );
+			}
+
+			// Scrub REQUEST_URI.
+			if ( ! empty( $_SERVER['REQUEST_URI'] ) ) {
+				list( $path, $query ) = explode( '?', $_SERVER['REQUEST_URI'], 2 );
+
+				$pairs                  = $build_query( $query );
+				$_SERVER['REQUEST_URI'] = $path;
+				if ( ! empty( $pairs ) ) {
+					$_SERVER['REQUEST_URI'] .= "?{$pairs}";
+				}
+			}
+		}
+	}
+
 	/**
 	 * Register/override widgets.
 	 *

tests/test-class-amp-theme-support.php

@@ -19,6 +19,8 @@ class Test_AMP_Theme_Support extends WP_UnitTestCase {
 	public function tearDown() {
 		parent::tearDown();
 		remove_theme_support( 'amp' );
+		$_REQUEST                = array(); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+		$_SERVER['QUERY_STRING'] = '';
 	}
 
 	/**
@@ -133,4 +135,51 @@ public function test_finish_output_buffering() {
 
 		$this->assertContains( '<script async custom-element="amp-ad"', $sanitized_html );
 	}
+
+	/**
+	 * Test purge_amp_query_vars.
+	 *
+	 * @covers AMP_Theme_Support::purge_amp_query_vars()
+	 */
+	public function test_purge_amp_query_vars() {
+		// phpcs:disable WordPress.Security.NonceVerification.NoNonceVerification
+		$bad_query_vars = array(
+			'amp_latest_update_time' => '1517199956',
+			'__amp_source_origin'    => home_url(),
+		);
+		$ok_query_vars  = array(
+			'bar' => 'baz',
+		);
+		$all_query_vars = array_merge( $bad_query_vars, $ok_query_vars );
+
+		$_SERVER['QUERY_STRING'] = build_query( $all_query_vars );
+
+		remove_action( 'wp', 'amp_maybe_add_actions' );
+		$this->go_to( add_query_arg( $all_query_vars, home_url( '/foo/' ) ) );
+		$_REQUEST = $_GET; // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+		foreach ( $all_query_vars as $key => $value ) {
+			$this->assertArrayHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertArrayHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+
+		AMP_Theme_Support::$purged_amp_query_vars = array();
+		AMP_Theme_Support::purge_amp_query_vars();
+		$this->assertEqualSets( AMP_Theme_Support::$purged_amp_query_vars, $bad_query_vars );
+
+		foreach ( $bad_query_vars as $key => $value ) {
+			$this->assertArrayNotHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertArrayNotHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertNotContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertNotContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+		foreach ( $ok_query_vars as $key => $value ) {
+			$this->assertArrayHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertArrayHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
+			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+		// phpcs:enable WordPress.Security.NonceVerification.NoNonceVerification
+	}
 }