| 1 |
<?php |
| 2 |
namespace Activitypub; |
| 3 |
|
| 4 |
use WP_Error; |
| 5 |
use DateTime; |
| 6 |
use DateTimeZone; |
| 7 |
use Activitypub\Collection\Users; |
| 8 |
|
| 9 |
/** |
| 10 |
* ActivityPub Signature Class |
| 11 |
* |
| 12 |
* @author Matthias Pfefferle |
| 13 |
* @author Django Doucet |
| 14 |
*/ |
| 15 |
class Signature { |
| 16 |
|
| 17 |
/** |
| 18 |
* Return the public key for a given user. |
| 19 |
* |
| 20 |
* @param int $user_id The WordPress User ID. |
| 21 |
* @param bool $force Force the generation of a new key pair. |
| 22 |
* |
| 23 |
* @return mixed The public key. |
| 24 |
*/ |
| 25 |
public static function get_public_key_for( $user_id, $force = false ) { |
| 26 |
if ( $force ) { |
| 27 |
self::generate_key_pair_for( $user_id ); |
| 28 |
} |
| 29 |
|
| 30 |
$key_pair = self::get_keypair_for( $user_id ); |
| 31 |
|
| 32 |
return $key_pair['public_key']; |
| 33 |
} |
| 34 |
|
| 35 |
/** |
| 36 |
* Return the private key for a given user. |
| 37 |
* |
| 38 |
* @param int $user_id The WordPress User ID. |
| 39 |
* @param bool $force Force the generation of a new key pair. |
| 40 |
* |
| 41 |
* @return mixed The private key. |
| 42 |
*/ |
| 43 |
public static function get_private_key_for( $user_id, $force = false ) { |
| 44 |
if ( $force ) { |
| 45 |
self::generate_key_pair_for( $user_id ); |
| 46 |
} |
| 47 |
|
| 48 |
$key_pair = self::get_keypair_for( $user_id ); |
| 49 |
|
| 50 |
return $key_pair['private_key']; |
| 51 |
} |
| 52 |
|
| 53 |
/** |
| 54 |
* Return the key pair for a given user. |
| 55 |
* |
| 56 |
* @param int $user_id The WordPress User ID. |
| 57 |
* |
| 58 |
* @return array The key pair. |
| 59 |
*/ |
| 60 |
public static function get_keypair_for( $user_id ) { |
| 61 |
$option_key = self::get_signature_options_key_for( $user_id ); |
| 62 |
$key_pair = \get_option( $option_key ); |
| 63 |
|
| 64 |
if ( ! $key_pair ) { |
| 65 |
$key_pair = self::generate_key_pair_for( $user_id ); |
| 66 |
} |
| 67 |
|
| 68 |
return $key_pair; |
| 69 |
} |
| 70 |
|
| 71 |
/** |
| 72 |
* Generates the pair keys |
| 73 |
* |
| 74 |
* @param int $user_id The WordPress User ID. |
| 75 |
* |
| 76 |
* @return array The key pair. |
| 77 |
*/ |
| 78 |
protected static function generate_key_pair_for( $user_id ) { |
| 79 |
$option_key = self::get_signature_options_key_for( $user_id ); |
| 80 |
$key_pair = self::check_legacy_key_pair_for( $user_id ); |
| 81 |
|
| 82 |
if ( $key_pair ) { |
| 83 |
\add_option( $option_key, $key_pair ); |
| 84 |
|
| 85 |
return $key_pair; |
| 86 |
} |
| 87 |
|
| 88 |
$config = array( |
| 89 |
'digest_alg' => 'sha512', |
| 90 |
'private_key_bits' => 2048, |
| 91 |
'private_key_type' => \OPENSSL_KEYTYPE_RSA, |
| 92 |
); |
| 93 |
|
| 94 |
$key = \openssl_pkey_new( $config ); |
| 95 |
$priv_key = null; |
| 96 |
|
| 97 |
\openssl_pkey_export( $key, $priv_key ); |
| 98 |
|
| 99 |
$detail = \openssl_pkey_get_details( $key ); |
| 100 |
|
| 101 |
// check if keys are valid |
| 102 |
if ( |
| 103 |
empty( $priv_key ) || ! is_string( $priv_key ) || |
| 104 |
! isset( $detail['key'] ) || ! is_string( $detail['key'] ) |
| 105 |
) { |
| 106 |
return array( |
| 107 |
'private_key' => null, |
| 108 |
'public_key' => null, |
| 109 |
); |
| 110 |
} |
| 111 |
|
| 112 |
$key_pair = array( |
| 113 |
'private_key' => $priv_key, |
| 114 |
'public_key' => $detail['key'], |
| 115 |
); |
| 116 |
|
| 117 |
// persist keys |
| 118 |
\add_option( $option_key, $key_pair ); |
| 119 |
|
| 120 |
return $key_pair; |
| 121 |
} |
| 122 |
|
| 123 |
/** |
| 124 |
* Return the option key for a given user. |
| 125 |
* |
| 126 |
* @param int $user_id The WordPress User ID. |
| 127 |
* |
| 128 |
* @return string The option key. |
| 129 |
*/ |
| 130 |
protected static function get_signature_options_key_for( $user_id ) { |
| 131 |
$id = $user_id; |
| 132 |
|
| 133 |
if ( $user_id > 0 ) { |
| 134 |
$user = \get_userdata( $user_id ); |
| 135 |
// sanatize username because it could include spaces and special chars |
| 136 |
$id = sanitize_title( $user->user_login ); |
| 137 |
} |
| 138 |
|
| 139 |
return 'activitypub_keypair_for_' . $id; |
| 140 |
} |
| 141 |
|
| 142 |
/** |
| 143 |
* Check if there is a legacy key pair |
| 144 |
* |
| 145 |
* @param int $user_id The WordPress User ID. |
| 146 |
* |
| 147 |
* @return array|bool The key pair or false. |
| 148 |
*/ |
| 149 |
protected static function check_legacy_key_pair_for( $user_id ) { |
| 150 |
switch ( $user_id ) { |
| 151 |
case 0: |
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$public_key = \get_option( 'activitypub_blog_user_public_key' ); |
| 153 |
$private_key = \get_option( 'activitypub_blog_user_private_key' ); |
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break; |
| 155 |
case -1: |
| 156 |
$public_key = \get_option( 'activitypub_application_user_public_key' ); |
| 157 |
$private_key = \get_option( 'activitypub_application_user_private_key' ); |
| 158 |
break; |
| 159 |
default: |
| 160 |
$public_key = \get_user_meta( $user_id, 'magic_sig_public_key', true ); |
| 161 |
$private_key = \get_user_meta( $user_id, 'magic_sig_private_key', true ); |
| 162 |
break; |
| 163 |
} |
| 164 |
|
| 165 |
if ( ! empty( $public_key ) && is_string( $public_key ) && ! empty( $private_key ) && is_string( $private_key ) ) { |
| 166 |
return array( |
| 167 |
'private_key' => $private_key, |
| 168 |
'public_key' => $public_key, |
| 169 |
); |
| 170 |
} |
| 171 |
|
| 172 |
return false; |
| 173 |
} |
| 174 |
|
| 175 |
/** |
| 176 |
* Generates the Signature for a HTTP Request |
| 177 |
* |
| 178 |
* @param int $user_id The WordPress User ID. |
| 179 |
* @param string $http_method The HTTP method. |
| 180 |
* @param string $url The URL to send the request to. |
| 181 |
* @param string $date The date the request is sent. |
| 182 |
* @param string $digest The digest of the request body. |
| 183 |
* |
| 184 |
* @return string The signature. |
| 185 |
*/ |
| 186 |
public static function generate_signature( $user_id, $http_method, $url, $date, $digest = null ) { |
| 187 |
$user = Users::get_by_id( $user_id ); |
| 188 |
$key = self::get_private_key_for( $user->get__id() ); |
| 189 |
|
| 190 |
$url_parts = \wp_parse_url( $url ); |
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|
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$host = $url_parts['host']; |
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$path = '/'; |
| 194 |
|
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// add path |
| 196 |
if ( ! empty( $url_parts['path'] ) ) { |
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$path = $url_parts['path']; |
| 198 |
} |
| 199 |
|
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// add query |
| 201 |
if ( ! empty( $url_parts['query'] ) ) { |
| 202 |
$path .= '?' . $url_parts['query']; |
| 203 |
} |
| 204 |
|
| 205 |
$http_method = \strtolower( $http_method ); |
| 206 |
|
| 207 |
if ( ! empty( $digest ) ) { |
| 208 |
$signed_string = "(request-target): $http_method $path\nhost: $host\ndate: $date\ndigest: $digest"; |
| 209 |
} else { |
| 210 |
$signed_string = "(request-target): $http_method $path\nhost: $host\ndate: $date"; |
| 211 |
} |
| 212 |
|
| 213 |
$signature = null; |
| 214 |
\openssl_sign( $signed_string, $signature, $key, \OPENSSL_ALGO_SHA256 ); |
| 215 |
$signature = \base64_encode( $signature ); // phpcs:ignore |
| 216 |
|
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$key_id = $user->get_url() . '#main-key'; |
| 218 |
|
| 219 |
if ( ! empty( $digest ) ) { |
| 220 |
return \sprintf( 'keyId="%s",algorithm="rsa-sha256",headers="(request-target) host date digest",signature="%s"', $key_id, $signature ); |
| 221 |
} else { |
| 222 |
return \sprintf( 'keyId="%s",algorithm="rsa-sha256",headers="(request-target) host date",signature="%s"', $key_id, $signature ); |
| 223 |
} |
| 224 |
} |
| 225 |
|
| 226 |
/** |
| 227 |
* Verifies the http signatures |
| 228 |
* |
| 229 |
* @param WP_REQUEST|array $request The request object or $_SERVER array. |
| 230 |
* |
| 231 |
* @return mixed A boolean or WP_Error. |
| 232 |
*/ |
| 233 |
public static function verify_http_signature( $request ) { |
| 234 |
if ( is_object( $request ) ) { // REST Request object |
| 235 |
// check if route starts with "index.php" |
| 236 |
if ( str_starts_with( $request->get_route(), '/index.php' ) || ! rest_get_url_prefix() ) { |
| 237 |
$route = $request->get_route(); |
| 238 |
} else { |
| 239 |
$route = '/' . rest_get_url_prefix() . '/' . ltrim( $request->get_route(), '/' ); |
| 240 |
} |
| 241 |
$headers = $request->get_headers(); |
| 242 |
$headers['(request-target)'][0] = strtolower( $request->get_method() ) . ' ' . $route; |
| 243 |
} else { |
| 244 |
$request = self::format_server_request( $request ); |
| 245 |
$headers = $request['headers']; // $_SERVER array |
| 246 |
$headers['(request-target)'][0] = strtolower( $headers['request_method'][0] ) . ' ' . $headers['request_uri'][0]; |
| 247 |
} |
| 248 |
|
| 249 |
if ( ! isset( $headers['signature'] ) ) { |
| 250 |
return new WP_Error( 'activitypub_signature', 'Request not signed', array( 'status' => 403 ) ); |
| 251 |
} |
| 252 |
|
| 253 |
if ( array_key_exists( 'signature', $headers ) ) { |
| 254 |
$signature_block = self::parse_signature_header( $headers['signature'][0] ); |
| 255 |
} elseif ( array_key_exists( 'authorization', $headers ) ) { |
| 256 |
$signature_block = self::parse_signature_header( $headers['authorization'][0] ); |
| 257 |
} |
| 258 |
|
| 259 |
if ( ! isset( $signature_block ) || ! $signature_block ) { |
| 260 |
return new WP_Error( 'activitypub_signature', 'Incompatible request signature. keyId and signature are required', array( 'status' => 403 ) ); |
| 261 |
} |
| 262 |
|
| 263 |
$signed_headers = $signature_block['headers']; |
| 264 |
if ( ! $signed_headers ) { |
| 265 |
$signed_headers = array( 'date' ); |
| 266 |
} |
| 267 |
|
| 268 |
$signed_data = self::get_signed_data( $signed_headers, $signature_block, $headers ); |
| 269 |
if ( ! $signed_data ) { |
| 270 |
return new WP_Error( 'activitypub_signature', 'Signed request date outside acceptable time window', array( 'status' => 403 ) ); |
| 271 |
} |
| 272 |
|
| 273 |
$algorithm = self::get_signature_algorithm( $signature_block ); |
| 274 |
if ( ! $algorithm ) { |
| 275 |
return new WP_Error( 'activitypub_signature', 'Unsupported signature algorithm (only rsa-sha256 and hs2019 are supported)', array( 'status' => 403 ) ); |
| 276 |
} |
| 277 |
|
| 278 |
if ( \in_array( 'digest', $signed_headers, true ) && isset( $body ) ) { |
| 279 |
if ( is_array( $headers['digest'] ) ) { |
| 280 |
$headers['digest'] = $headers['digest'][0]; |
| 281 |
} |
| 282 |
$digest = explode( '=', $headers['digest'], 2 ); |
| 283 |
if ( 'SHA-256' === $digest[0] ) { |
| 284 |
$hashalg = 'sha256'; |
| 285 |
} |
| 286 |
if ( 'SHA-512' === $digest[0] ) { |
| 287 |
$hashalg = 'sha512'; |
| 288 |
} |
| 289 |
|
| 290 |
if ( \base64_encode( \hash( $hashalg, $body, true ) ) !== $digest[1] ) { // phpcs:ignore |
| 291 |
return new WP_Error( 'activitypub_signature', 'Invalid Digest header', array( 'status' => 403 ) ); |
| 292 |
} |
| 293 |
} |
| 294 |
|
| 295 |
$public_key = self::get_remote_key( $signature_block['keyId'] ); |
| 296 |
|
| 297 |
if ( \is_wp_error( $public_key ) ) { |
| 298 |
return $public_key; |
| 299 |
} |
| 300 |
|
| 301 |
$verified = \openssl_verify( $signed_data, $signature_block['signature'], $public_key, $algorithm ) > 0; |
| 302 |
|
| 303 |
if ( ! $verified ) { |
| 304 |
return new WP_Error( 'activitypub_signature', 'Invalid signature', array( 'status' => 403 ) ); |
| 305 |
} |
| 306 |
return $verified; |
| 307 |
} |
| 308 |
|
| 309 |
/** |
| 310 |
* Get public key from key_id |
| 311 |
* |
| 312 |
* @param string $key_id The URL to the public key. |
| 313 |
* |
| 314 |
* @return WP_Error|string The public key. |
| 315 |
*/ |
| 316 |
public static function get_remote_key( $key_id ) { // phpcs:ignore |
| 317 |
$actor = get_remote_metadata_by_actor( strip_fragment_from_url( $key_id ) ); // phpcs:ignore |
| 318 |
if ( \is_wp_error( $actor ) ) { |
| 319 |
return $actor; |
| 320 |
} |
| 321 |
if ( isset( $actor['publicKey']['publicKeyPem'] ) ) { |
| 322 |
return \rtrim( $actor['publicKey']['publicKeyPem'] ); // phpcs:ignore |
| 323 |
} |
| 324 |
return new WP_Error( 'activitypub_no_remote_key_found', 'No Public-Key found' ); |
| 325 |
} |
| 326 |
|
| 327 |
/** |
| 328 |
* Gets the signature algorithm from the signature header |
| 329 |
* |
| 330 |
* @param array $signature_block |
| 331 |
* |
| 332 |
* @return string The signature algorithm. |
| 333 |
*/ |
| 334 |
public static function get_signature_algorithm( $signature_block ) { |
| 335 |
if ( $signature_block['algorithm'] ) { |
| 336 |
switch ( $signature_block['algorithm'] ) { |
| 337 |
case 'rsa-sha-512': |
| 338 |
return 'sha512'; //hs2019 https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12 |
| 339 |
default: |
| 340 |
return 'sha256'; |
| 341 |
} |
| 342 |
} |
| 343 |
return false; |
| 344 |
} |
| 345 |
|
| 346 |
/** |
| 347 |
* Parses the Signature header |
| 348 |
* |
| 349 |
* @param string $signature The signature header. |
| 350 |
* |
| 351 |
* @return array signature parts |
| 352 |
*/ |
| 353 |
public static function parse_signature_header( $signature ) { |
| 354 |
$parsed_header = array(); |
| 355 |
$matches = array(); |
| 356 |
|
| 357 |
if ( \preg_match( '/keyId="(.*?)"/ism', $signature, $matches ) ) { |
| 358 |
$parsed_header['keyId'] = trim( $matches[1] ); |
| 359 |
} |
| 360 |
if ( \preg_match( '/created=([0-9]*)/ism', $signature, $matches ) ) { |
| 361 |
$parsed_header['(created)'] = trim( $matches[1] ); |
| 362 |
} |
| 363 |
if ( \preg_match( '/expires=([0-9]*)/ism', $signature, $matches ) ) { |
| 364 |
$parsed_header['(expires)'] = trim( $matches[1] ); |
| 365 |
} |
| 366 |
if ( \preg_match( '/algorithm="(.*?)"/ism', $signature, $matches ) ) { |
| 367 |
$parsed_header['algorithm'] = trim( $matches[1] ); |
| 368 |
} |
| 369 |
if ( \preg_match( '/headers="(.*?)"/ism', $signature, $matches ) ) { |
| 370 |
$parsed_header['headers'] = \explode( ' ', trim( $matches[1] ) ); |
| 371 |
} |
| 372 |
if ( \preg_match( '/signature="(.*?)"/ism', $signature, $matches ) ) { |
| 373 |
$parsed_header['signature'] = \base64_decode( preg_replace( '/\s+/', '', trim( $matches[1] ) ) ); // phpcs:ignore |
| 374 |
} |
| 375 |
|
| 376 |
if ( ( $parsed_header['signature'] ) && ( $parsed_header['algorithm'] ) && ( ! $parsed_header['headers'] ) ) { |
| 377 |
$parsed_header['headers'] = array( 'date' ); |
| 378 |
} |
| 379 |
|
| 380 |
return $parsed_header; |
| 381 |
} |
| 382 |
|
| 383 |
/** |
| 384 |
* Gets the header data from the included pseudo headers |
| 385 |
* |
| 386 |
* @param array $signed_headers The signed headers. |
| 387 |
* @param array $signature_block (pseudo-headers) |
| 388 |
* @param array $headers (http headers) |
| 389 |
* |
| 390 |
* @return string signed headers for comparison |
| 391 |
*/ |
| 392 |
public static function get_signed_data( $signed_headers, $signature_block, $headers ) { |
| 393 |
$signed_data = ''; |
| 394 |
// This also verifies time-based values by returning false if any of these are out of range. |
| 395 |
foreach ( $signed_headers as $header ) { |
| 396 |
if ( 'host' === $header ) { |
| 397 |
if ( isset( $headers['x_original_host'] ) ) { |
| 398 |
$signed_data .= $header . ': ' . $headers['x_original_host'][0] . "\n"; |
| 399 |
continue; |
| 400 |
} |
| 401 |
} |
| 402 |
if ( '(request-target)' === $header ) { |
| 403 |
$signed_data .= $header . ': ' . $headers[ $header ][0] . "\n"; |
| 404 |
continue; |
| 405 |
} |
| 406 |
if ( str_contains( $header, '-' ) ) { |
| 407 |
$signed_data .= $header . ': ' . $headers[ str_replace( '-', '_', $header ) ][0] . "\n"; |
| 408 |
continue; |
| 409 |
} |
| 410 |
if ( '(created)' === $header ) { |
| 411 |
if ( ! empty( $signature_block['(created)'] ) && \intval( $signature_block['(created)'] ) > \time() ) { |
| 412 |
// created in future |
| 413 |
return false; |
| 414 |
} |
| 415 |
} |
| 416 |
if ( '(expires)' === $header ) { |
| 417 |
if ( ! empty( $signature_block['(expires)'] ) && \intval( $signature_block['(expires)'] ) < \time() ) { |
| 418 |
// expired in past |
| 419 |
return false; |
| 420 |
} |
| 421 |
} |
| 422 |
if ( 'date' === $header ) { |
| 423 |
// allow a bit of leeway for misconfigured clocks. |
| 424 |
$d = new DateTime( $headers[ $header ][0] ); |
| 425 |
$d->setTimeZone( new DateTimeZone( 'UTC' ) ); |
| 426 |
$c = $d->format( 'U' ); |
| 427 |
|
| 428 |
$dplus = time() + ( 3 * HOUR_IN_SECONDS ); |
| 429 |
$dminus = time() - ( 3 * HOUR_IN_SECONDS ); |
| 430 |
|
| 431 |
if ( $c > $dplus || $c < $dminus ) { |
| 432 |
// time out of range |
| 433 |
return false; |
| 434 |
} |
| 435 |
} |
| 436 |
$signed_data .= $header . ': ' . $headers[ $header ][0] . "\n"; |
| 437 |
} |
| 438 |
return \rtrim( $signed_data, "\n" ); |
| 439 |
} |
| 440 |
|
| 441 |
/** |
| 442 |
* Generates the digest for a HTTP Request |
| 443 |
* |
| 444 |
* @param string $body The body of the request. |
| 445 |
* |
| 446 |
* @return string The digest. |
| 447 |
*/ |
| 448 |
public static function generate_digest( $body ) { |
| 449 |
$digest = \base64_encode( \hash( 'sha256', $body, true ) ); // phpcs:ignore |
| 450 |
return "SHA-256=$digest"; |
| 451 |
} |
| 452 |
|
| 453 |
/** |
| 454 |
* Formats the $_SERVER to resemble the WP_REST_REQUEST array, |
| 455 |
* for use with verify_http_signature() |
| 456 |
* |
| 457 |
* @param array $_SERVER The $_SERVER array. |
| 458 |
* |
| 459 |
* @return array $request The formatted request array. |
| 460 |
*/ |
| 461 |
public static function format_server_request( $server ) { |
| 462 |
$request = array(); |
| 463 |
foreach ( $server as $param_key => $param_val ) { |
| 464 |
$req_param = strtolower( $param_key ); |
| 465 |
if ( 'REQUEST_URI' === $req_param ) { |
| 466 |
$request['headers']['route'][] = $param_val; |
| 467 |
} else { |
| 468 |
$header_key = str_replace( |
| 469 |
'http_', |
| 470 |
'', |
| 471 |
$req_param |
| 472 |
); |
| 473 |
$request['headers'][ $header_key ][] = \wp_unslash( $param_val ); |
| 474 |
} |
| 475 |
} |
| 476 |
return $request; |
| 477 |
} |
| 478 |
} |
| 479 |
|
