amp-debug-validation-request.php

<?php
/**
 * AMP Debug Validation Request plugin initialization file.
 *
 * @package   AMP_Debug_Validation_Request
 * @author    Weston Ruter, Google
 * @license   GPL-2.0-or-later
 * @copyright 2019 Google Inc.
 *
 * @wordpress-plugin
 * Plugin Name: AMP Debug Validation Request
 * Plugin URI: https://gist.github.com/westonruter/48e546e4636bec5fafd8a29e0fc7a001
 * Description: Debug validation request failures.
 * Version: 0.3.0
 * Author: Weston Ruter, Google
 * Author URI: https://weston.ruter.net/
 * License: GNU General Public License v2 (or later)
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 * Gist Plugin URI: https://gist.github.com/westonruter/48e546e4636bec5fafd8a29e0fc7a001
 */

namespace AMP_Debug_Validation_Request;

use AMP_Validation_Manager;
use WP_Admin_Bar;
use WP_Error;

const QUERY_VAR = 'amp_debug_validate_request';

add_action(
	'parse_query',
	function () {
		if ( ! isset( $_GET[ QUERY_VAR ] ) || ! class_exists( 'AMP_Validation_Manager' ) ) {
			return;
		}
		if ( ! AMP_Validation_Manager::has_cap() ) {
			wp_die( 'Please log in before doing this.' );
		}
		if ( ! wp_verify_nonce( wp_unslash( $_GET[ QUERY_VAR ] ), QUERY_VAR ) ) {
			wp_die( 'Unable to verify nonce.' );
		}

		$current_url = amp_get_current_url();
		$current_url = remove_query_arg( QUERY_VAR, $current_url );

		$results = validate_url( $current_url );

		$data = [
			'success' => ! is_wp_error( $results ),
			'results' => $results,
		];

		header( 'Content-Type: application/json' );
		echo wp_json_encode( $data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES );
		exit;
	}
);

add_action(
	'admin_bar_menu',
	function ( WP_Admin_Bar $admin_bar ) {
		if ( ! $admin_bar->get_node( 'amp' ) || ! AMP_Validation_Manager::has_cap() || ! class_exists( 'AMP_Validation_Manager' ) ) {
			return;
		}

		$admin_bar->add_node(
			[
				'id'     => 'amp-debug-validation-response-directly',
				'title'  => 'Debug AMP validation response directly',
				'href'   => add_query_arg( AMP_Validation_Manager::VALIDATE_QUERY_VAR, AMP_Validation_Manager::get_amp_validate_nonce() ),
				'parent' => 'amp',
				'meta'   => [
					'target' => '_blank',
				],
			]
		);

		$admin_bar->add_node(
			[
				'id'     => 'amp-debug-validation-response-with-loopback-request',
				'title'  => 'Debug AMP validation response w/ loopback request',
				'href'   => add_query_arg( QUERY_VAR, wp_create_nonce( QUERY_VAR ) ),
				'parent' => 'amp',
				'meta'   => [
					'target' => '_blank',
				],
			]
		);
	},
	1000
);

// Work around issue where amp_validate is included in url key of response.
add_action(
	'wp',
	function () {
		if ( ! class_exists( 'AMP_Validation_Manager' ) ) {
			return;
		}
		$_SERVER['REQUEST_URI'] = remove_query_arg( AMP_Validation_Manager::VALIDATE_QUERY_VAR, $_SERVER['REQUEST_URI'] );
	}
);

/**
 * Validate URL.
 *
 * Patched version of `AMP_Validation_Manager::validate_url()`.
 *
 * @param string $url URL.
 * @return array|WP_Error
 */
function validate_url( $url ) {
	$added_query_vars = [
		AMP_Validation_Manager::VALIDATE_QUERY_VAR   => AMP_Validation_Manager::get_amp_validate_nonce(),
		AMP_Validation_Manager::CACHE_BUST_QUERY_VAR => wp_rand(),
	];
	$validation_url   = add_query_arg( $added_query_vars, $url );

	$r = null;

	/** This filter is documented in wp-includes/class-http.php */
	$allowed_redirects = apply_filters( 'http_request_redirection_count', 5 );
	for ( $redirect_count = 0; $redirect_count < $allowed_redirects; $redirect_count++ ) {
		$r = wp_remote_get(
			$validation_url,
			[
				'cookies'     => wp_unslash( $_COOKIE ), // Pass along cookies so private pages and drafts can be accessed.
				'timeout'     => 15, // Increase from default of 5 to give extra time for the plugin to identify the sources for any given validation errors.
				'sslverify'   => false,
				'redirection' => 0, // Because we're in a loop for redirection.
				'headers'     => [
					'Cache-Control' => 'no-cache',
				],
			]
		);

		// If the response is not a redirect, then break since $r is all we need.
		$response_code   = wp_remote_retrieve_response_code( $r );
		$location_header = wp_remote_retrieve_header( $r, 'Location' );
		$is_redirect     = (
			$response_code
			&&
			$response_code > 300 && $response_code < 400
			&&
			$location_header
		);
		if ( ! $is_redirect ) {
			break;
		}

		// Ensure absolute URL.
		if ( '/' === substr( $location_header, 0, 1 ) ) {
			$location_header = preg_replace( '#(^https?://[^/]+)/.*#', '$1', home_url( '/' ) ) . $location_header;
		}

		// Block redirecting to a different host.
		$location_header = wp_validate_redirect( $location_header );
		if ( ! $location_header ) {
			break;
		}

		$validation_url = add_query_arg( $added_query_vars, $location_header );
	}

	if ( is_wp_error( $r ) ) {
		return $r;
	}

	$response = trim( wp_remote_retrieve_body( $r ) );
	if ( wp_remote_retrieve_response_code( $r ) >= 400 ) {
		$data = json_decode( $response, true );
		return new WP_Error(
			is_array( $data ) && isset( $data['code'] ) ? $data['code'] : wp_remote_retrieve_response_code( $r ),
			is_array( $data ) && isset( $data['message'] ) ? $data['message'] : wp_remote_retrieve_response_message( $r )
		);
	}

	if ( wp_remote_retrieve_response_code( $r ) >= 300 ) {
		return new WP_Error(
			'http_request_failed',
			__( 'Too many redirects.', 'amp' )
		);
	}

	$url = remove_query_arg(
		array_keys( $added_query_vars ),
		$validation_url
	);

	// Strip byte order mark (BOM).
	while ( "\xEF\xBB\xBF" === substr( $response, 0, 3 ) ) {
		$response = substr( $response, 3 );
	}

	// Strip any leading whitespace.
	$response = ltrim( $response );

	// Strip HTML comments that may have been injected at the end of the response (e.g. by a caching plugin).
	$response = preg_replace( '/<!--.*?-->\s*$/s', '', $response );

	$data = [
		'first_kb_response' => substr( $response, 0, 1024 ),
	];

	if ( '' === $response ) {
		return new WP_Error( 'white_screen_of_death', '', $data );
	}
	if ( '{' !== substr( $response, 0, 1 ) ) {
		return new WP_Error( 'response_not_json', '', $data );
	}
	$validation = json_decode( $response, true );
	if ( json_last_error() || ! isset( $validation['results'] ) || ! is_array( $validation['results'] ) ) {
		return new WP_Error( 'malformed_json_validation_errors', '', $data );
	}

	return array_merge(
		$validation,
		compact( 'url' )
	);
}

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c