class-reprint-exporter.php
284 lines
| 1 | <?php |
| 2 | /** |
| 3 | * Reprint export support for Jetpack on Pressable and WordPress.com (Atomic). |
| 4 | * |
| 5 | * Mirrors the behavior shipped in wpcomsh for WordPress.com on Atomic, but |
| 6 | * hosted in Jetpack so it also serves Pressable and can eventually replace the |
| 7 | * wpcomsh copy. It exposes an HMAC-authenticated, time-limited full-site export |
| 8 | * endpoint backed by the wp-php-toolkit/reprint-exporter package. |
| 9 | * |
| 10 | * On Atomic this runs alongside the wpcomsh copy without colliding: it uses a |
| 11 | * distinct query var (?reprint-api-jetpack) and REST namespace (jetpack/v4/*), so |
| 12 | * clients can migrate off the old ?reprint-api / wpcomsh/v1 surface at their |
| 13 | * own pace. |
| 14 | * |
| 15 | * Gating, in two phases that use different auth and network paths: |
| 16 | * |
| 17 | * 1. Secret rotation via the generic Jetpack REST proxy. The |
| 18 | * /jetpack/v4/reprint/rotate-export-secret route only accepts |
| 19 | * Jetpack-signed requests, so it can only be invoked through the |
| 20 | * WordPress.com public API proxy. On success the site generates a random |
| 21 | * secret, stores it in the `reprint_exporter_secret` option, opens the |
| 22 | * export window, and returns the secret. |
| 23 | * |
| 24 | * 2. Export streaming — the client (now holding the shared secret) talks |
| 25 | * directly to the site at ?reprint-api-jetpack using HMAC-signed requests. This |
| 26 | * bypasses the public API entirely because public-api does not support |
| 27 | * streaming and extra hops add latency and complexity. |
| 28 | * |
| 29 | * The whole feature is gated behind the host check (overridable via the |
| 30 | * `jetpack_reprint_export_available` filter), so generic self-hosted Jetpack |
| 31 | * sites never register or expose any of it. |
| 32 | * |
| 33 | * @package automattic/jetpack |
| 34 | */ |
| 35 | |
| 36 | namespace Automattic\Jetpack\Reprint_Export; |
| 37 | |
| 38 | use Automattic\Jetpack\Constants; |
| 39 | use Automattic\Jetpack\Status\Host; |
| 40 | |
| 41 | /** |
| 42 | * Reprint exporter for Jetpack (Pressable and WordPress.com/Atomic). |
| 43 | */ |
| 44 | class Reprint_Exporter { |
| 45 | |
| 46 | /** |
| 47 | * Option holding the per-site HMAC shared secret. |
| 48 | * |
| 49 | * @var string |
| 50 | */ |
| 51 | const SECRET_OPTION = 'reprint_exporter_secret'; |
| 52 | |
| 53 | /** |
| 54 | * Option holding the unix timestamp of the last time the export window |
| 55 | * was opened. The window is a sliding 60-minute one. |
| 56 | * |
| 57 | * @var string |
| 58 | */ |
| 59 | const ENABLED_OPTION = 'reprint_exporter_enabled'; |
| 60 | |
| 61 | /** |
| 62 | * Clock-skew tolerance, in seconds, allowed for HMAC signatures. |
| 63 | * |
| 64 | * @var int |
| 65 | */ |
| 66 | const HMAC_CLOCK_SKEW = 300; |
| 67 | |
| 68 | /** |
| 69 | * Registers the WordPress hooks. Only ever called on sites where |
| 70 | * is_available() is true (see Jetpack bootstrap). |
| 71 | */ |
| 72 | public static function init() { |
| 73 | add_action( 'parse_request', array( new self(), 'handle_request' ), 0 ); |
| 74 | add_action( 'rest_api_init', array( __CLASS__, 'register_rest_routes' ) ); |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * Whether Reprint export support is available on the current site. |
| 79 | * |
| 80 | * Defaults to true on Pressable and WordPress.com (Atomic) hosts, false |
| 81 | * everywhere else. The filter acts as both an override for testing and an |
| 82 | * emergency kill switch. |
| 83 | * |
| 84 | * On Atomic this coexists with the copy shipped in wpcomsh: the two use |
| 85 | * different query vars (?reprint-api-jetpack here vs ?reprint-api there) and |
| 86 | * REST namespaces (jetpack/v4 vs wpcomsh/v1), so both can run side by side |
| 87 | * while clients migrate to the Jetpack surface. Atomic detection uses |
| 88 | * is_atomic_platform() rather than is_woa_site() so it keeps working once |
| 89 | * wpcomsh (and its reprint copy) is removed. |
| 90 | * |
| 91 | * @return bool |
| 92 | */ |
| 93 | public static function is_available() { |
| 94 | $host = new Host(); |
| 95 | |
| 96 | // Host::is_pressable() was added in jetpack-status 6.2.0. Another plugin on the |
| 97 | // site can ship an older copy of the package that wins autoloading, in which case |
| 98 | // calling the method is fatal, so fall back to the constant it reads. |
| 99 | $is_pressable = method_exists( $host, 'is_pressable' ) |
| 100 | ? $host->is_pressable() |
| 101 | : Constants::is_true( 'IS_PRESSABLE' ); |
| 102 | |
| 103 | $available = $is_pressable || $host->is_atomic_platform(); |
| 104 | |
| 105 | /** |
| 106 | * Filters whether Jetpack Reprint export support is available on the |
| 107 | * current site. |
| 108 | * |
| 109 | * Default: true on Pressable and WordPress.com (Atomic), false elsewhere. |
| 110 | * |
| 111 | * @since 16.1 |
| 112 | * |
| 113 | * @param bool $available Whether Reprint export support is available. |
| 114 | */ |
| 115 | return (bool) apply_filters( 'jetpack_reprint_export_available', $available ); |
| 116 | } |
| 117 | |
| 118 | /** |
| 119 | * Registers the secret-rotation REST route. |
| 120 | */ |
| 121 | public static function register_rest_routes() { |
| 122 | ( new REST_Controller() )->register_routes(); |
| 123 | } |
| 124 | |
| 125 | /** |
| 126 | * Handles the ?reprint-api-jetpack request. |
| 127 | * |
| 128 | * Hooked on `parse_request` at priority 0 so we run before WordPress |
| 129 | * resolves the query and long before any template output (important on |
| 130 | * Private Sites, whose template_redirect hooks redirect + exit). |
| 131 | * |
| 132 | * @param \WP $wp The WordPress environment instance. |
| 133 | */ |
| 134 | public function handle_request( $wp ) { |
| 135 | // phpcs:ignore WordPress.Security.NonceVerification.Recommended |
| 136 | if ( ! isset( $_GET['reprint-api-jetpack'] ) ) { |
| 137 | return; |
| 138 | } |
| 139 | |
| 140 | // Defense in depth: the hook is only registered when available, but |
| 141 | // re-check so the filter kill switch also short-circuits live requests. |
| 142 | if ( ! self::is_available() ) { |
| 143 | return; |
| 144 | } |
| 145 | |
| 146 | // Only respond on the root path, matching the wpcomsh behavior. |
| 147 | if ( '' !== $wp->request ) { |
| 148 | return; |
| 149 | } |
| 150 | |
| 151 | // Sliding activation window: the export stays open only for 60 |
| 152 | // minutes since the last accepted request, so an idle site |
| 153 | // auto-closes the gate. HMAC verification happens separately below. |
| 154 | if ( ! self::is_export_window_open() ) { |
| 155 | return; |
| 156 | } |
| 157 | |
| 158 | // -- CORS ------------------------------------------------------------- |
| 159 | // Allow CORS from any origin. The export client (e.g. Playground) |
| 160 | // runs on many different deployments and new ones appear regularly. |
| 161 | // Since every export request requires a dedicated HMAC secret, the |
| 162 | // origin header is not a meaningful security boundary — an attacker |
| 163 | // without the secret cannot export anything regardless of origin. |
| 164 | // |
| 165 | // Must run before authentication: browsers send the OPTIONS preflight |
| 166 | // without credentials, so auth must not be required for that method. |
| 167 | if ( ! headers_sent() ) { |
| 168 | header( 'Access-Control-Allow-Origin: *' ); |
| 169 | header( 'Access-Control-Allow-Methods: GET, POST, OPTIONS' ); |
| 170 | header( 'Access-Control-Allow-Headers: *' ); |
| 171 | } |
| 172 | |
| 173 | // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized,WordPress.Security.ValidatedSanitizedInput.MissingUnslash |
| 174 | $request_method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( $_SERVER['REQUEST_METHOD'] ) : ''; |
| 175 | if ( 'OPTIONS' === $request_method ) { |
| 176 | if ( ! headers_sent() ) { |
| 177 | header( 'Allow: GET, POST, OPTIONS' ); |
| 178 | } |
| 179 | $this->terminate(); |
| 180 | return; |
| 181 | } |
| 182 | |
| 183 | // -- Authenticate via HMAC -------------------------------------------- |
| 184 | $secret = get_option( self::SECRET_OPTION, '' ); |
| 185 | if ( ! is_string( $secret ) || '' === $secret ) { |
| 186 | $this->error( 503, 'Export not configured. Please rotate the shared secret via POST /jetpack/v4/reprint/rotate-export-secret.' ); |
| 187 | return; |
| 188 | } |
| 189 | |
| 190 | $auth_error = $this->verify_hmac( $secret ); |
| 191 | if ( null !== $auth_error ) { |
| 192 | $this->error( 403, $auth_error ); |
| 193 | return; |
| 194 | } |
| 195 | |
| 196 | // Bump the timestamp now that we know this request is legit. |
| 197 | self::open_export_window(); |
| 198 | |
| 199 | // WordPress is already loaded at this point. Run Reprint! |
| 200 | $this->serve_export(); |
| 201 | $this->terminate(); |
| 202 | } |
| 203 | |
| 204 | /** |
| 205 | * Gate for the export handler: the enabled option must hold a unix |
| 206 | * timestamp within the last 60 minutes. |
| 207 | * |
| 208 | * @return bool |
| 209 | */ |
| 210 | public static function is_export_window_open() { |
| 211 | $enabled_at = (int) get_option( self::ENABLED_OPTION, 0 ); |
| 212 | return $enabled_at > 0 && ( time() - $enabled_at ) <= HOUR_IN_SECONDS; |
| 213 | } |
| 214 | |
| 215 | /** |
| 216 | * Opens (or slides forward) the 60-minute export window by stamping the |
| 217 | * enabled option with the current time. |
| 218 | * |
| 219 | * Shared by the REST enable/rotate routes and the request handler's |
| 220 | * post-auth bump, so the window is opened the same way everywhere. |
| 221 | * |
| 222 | * @return int The unix timestamp the window was opened at. |
| 223 | */ |
| 224 | public static function open_export_window() { |
| 225 | $now = time(); |
| 226 | update_option( self::ENABLED_OPTION, $now ); |
| 227 | return $now; |
| 228 | } |
| 229 | |
| 230 | /** |
| 231 | * Verifies the HMAC signature of the current request. |
| 232 | * |
| 233 | * Seam for tests to override without instantiating the real server. |
| 234 | * |
| 235 | * @param string $secret The per-site shared secret. |
| 236 | * @return string|null Error message on failure, null on success. |
| 237 | */ |
| 238 | protected function verify_hmac( $secret ) { |
| 239 | $hmac_server = new \Site_Export_HMAC_Server( $secret, self::HMAC_CLOCK_SKEW ); |
| 240 | return $hmac_server->verify_globals(); |
| 241 | } |
| 242 | |
| 243 | /** |
| 244 | * Streams the export response. |
| 245 | * |
| 246 | * Seam for tests to override so they don't perform a real export. |
| 247 | */ |
| 248 | protected function serve_export() { |
| 249 | \Site_Export_HTTP_Server::serve( array( 'default_directory' => ABSPATH ) ); |
| 250 | } |
| 251 | |
| 252 | /** |
| 253 | * Sends a JSON error response and terminates. |
| 254 | * |
| 255 | * @param int $code HTTP status code. |
| 256 | * @param string $message Error description. |
| 257 | */ |
| 258 | protected function error( $code, $message ) { |
| 259 | if ( ! headers_sent() ) { |
| 260 | http_response_code( $code ); |
| 261 | header( 'Content-Type: application/json' ); |
| 262 | } |
| 263 | // phpcs:ignore WordPress.WP.AlternativeFunctions.json_encode_json_encode |
| 264 | echo json_encode( |
| 265 | array( |
| 266 | 'error' => $message, |
| 267 | 'code' => $code, |
| 268 | ), |
| 269 | JSON_FORCE_OBJECT |
| 270 | ); |
| 271 | $this->terminate(); |
| 272 | } |
| 273 | |
| 274 | /** |
| 275 | * Terminates the request. |
| 276 | * |
| 277 | * Seam wrapping exit() so tests (which redefine exit via patchwork) can |
| 278 | * assert termination without killing the process. |
| 279 | */ |
| 280 | protected function terminate() { |
| 281 | exit; |
| 282 | } |
| 283 | } |
| 284 |