includes/exception/MWExceptionHandler.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  */
  20
  21 use MediaWiki\Logger\LoggerFactory;
  22 use MediaWiki\MediaWikiServices;
  23
  24 /**
  25  * Handler class for MWExceptions
  26  * @ingroup Exception
  27  */
  28 class MWExceptionHandler {
  29
  30         /**
  31          * @var string $reservedMemory
  32          */
  33         protected static $reservedMemory;
  34         /**
  35          * @var array $fatalErrorTypes
  36          */
  37         protected static $fatalErrorTypes = [
  38                 E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR,
  39                 /* HHVM's FATAL_ERROR level */ 16777217,
  40         ];
  41         /**
  42          * @var bool $handledFatalCallback
  43          */
  44         protected static $handledFatalCallback = false;
  45
  46         /**
  47          * Install handlers with PHP.
  48          */
  49         public static function installHandler() {
  50                 set_exception_handler( 'MWExceptionHandler::handleException' );
  51                 set_error_handler( 'MWExceptionHandler::handleError' );
  52
  53                 // Reserve 16k of memory so we can report OOM fatals
  54                 self::$reservedMemory = str_repeat( ' ', 16384 );
  55                 register_shutdown_function( 'MWExceptionHandler::handleFatalError' );
  56         }
  57
  58         /**
  59          * Report an exception to the user
  60          * @param Exception|Throwable $e
  61          */
  62         protected static function report( $e ) {
  63                 try {
  64                         // Try and show the exception prettily, with the normal skin infrastructure
  65                         if ( $e instanceof MWException ) {
  66                                 // Delegate to MWException until all subclasses are handled by
  67                                 // MWExceptionRenderer and MWException::report() has been
  68                                 // removed.
  69                                 $e->report();
  70                         } else {
  71                                 MWExceptionRenderer::output(
  72                                         $e, MWExceptionRenderer::AS_PRETTY );
  73                         }
  74                 } catch ( Exception $e2 ) {
  75                         // Exception occurred from within exception handler
  76                         // Show a simpler message for the original exception,
  77                         // don't try to invoke report()
  78                         MWExceptionRenderer::output( $e, MWExceptionRenderer::AS_PRETTY, $e2 );
  79                 }
  80         }
  81
  82         /**
  83          * If there are any open database transactions, roll them back and log
  84          * the stack trace of the exception that should have been caught so the
  85          * transaction could be aborted properly.
  86          *
  87          * @since 1.23
  88          * @param Exception|Throwable $e
  89          */
  90         public static function rollbackMasterChangesAndLog( $e ) {
  91                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
  92                 if ( $lbFactory->hasMasterChanges() ) {
  93                         $logger = LoggerFactory::getInstance( 'Bug56269' );
  94                         $logger->warning(
  95                                 'Exception thrown with an uncommited database transaction: ' .
  96                                 self::getLogMessage( $e ),
  97                                 self::getLogContext( $e )
  98                         );
  99                 }
 100                 $lbFactory->rollbackMasterChanges( __METHOD__ );
 101         }
 102
 103         /**
 104          * Exception handler which simulates the appropriate catch() handling:
 105          *
 106          *   try {
 107          *       ...
 108          *   } catch ( Exception $e ) {
 109          *       $e->report();
 110          *   } catch ( Exception $e ) {
 111          *       echo $e->__toString();
 112          *   }
 113          *
 114          * @since 1.25
 115          * @param Exception|Throwable $e
 116          */
 117         public static function handleException( $e ) {
 118                 try {
 119                         // Rollback DBs to avoid transaction notices. This may fail
 120                         // to rollback some DB due to connection issues or exceptions.
 121                         // However, any sane DB driver will rollback implicitly anyway.
 122                         self::rollbackMasterChangesAndLog( $e );
 123                 } catch ( DBError $e2 ) {
 124                         // If the DB is unreacheable, rollback() will throw an error
 125                         // and the error report() method might need messages from the DB,
 126                         // which would result in an exception loop. PHP may escalate such
 127                         // errors to "Exception thrown without a stack frame" fatals, but
 128                         // it's better to be explicit here.
 129                         self::logException( $e2 );
 130                 }
 131
 132                 self::logException( $e );
 133                 self::report( $e );
 134
 135                 // Exit value should be nonzero for the benefit of shell jobs
 136                 exit( 1 );
 137         }
 138
 139         /**
 140          * Handler for set_error_handler() callback notifications.
 141          *
 142          * Receive a callback from the interpreter for a raised error, create an
 143          * ErrorException, and log the exception to the 'error' logging
 144          * channel(s). If the raised error is a fatal error type (only under HHVM)
 145          * delegate to handleFatalError() instead.
 146          *
 147          * @since 1.25
 148          *
 149          * @param int $level Error level raised
 150          * @param string $message
 151          * @param string $file
 152          * @param int $line
 153          * @return bool
 154          *
 155          * @see logError()
 156          */
 157         public static function handleError(
 158                 $level, $message, $file = null, $line = null
 159         ) {
 160                 if ( in_array( $level, self::$fatalErrorTypes ) ) {
 161                         return call_user_func_array(
 162                                 'MWExceptionHandler::handleFatalError', func_get_args()
 163                         );
 164                 }
 165
 166                 // Map error constant to error name (reverse-engineer PHP error
 167                 // reporting)
 168                 switch ( $level ) {
 169                         case E_RECOVERABLE_ERROR:
 170                                 $levelName = 'Error';
 171                                 break;
 172                         case E_WARNING:
 173                         case E_CORE_WARNING:
 174                         case E_COMPILE_WARNING:
 175                         case E_USER_WARNING:
 176                                 $levelName = 'Warning';
 177                                 break;
 178                         case E_NOTICE:
 179                         case E_USER_NOTICE:
 180                                 $levelName = 'Notice';
 181                                 break;
 182                         case E_STRICT:
 183                                 $levelName = 'Strict Standards';
 184                                 break;
 185                         case E_DEPRECATED:
 186                         case E_USER_DEPRECATED:
 187                                 $levelName = 'Deprecated';
 188                                 break;
 189                         default:
 190                                 $levelName = 'Unknown error';
 191                                 break;
 192                 }
 193
 194                 $e = new ErrorException( "PHP $levelName: $message", 0, $level, $file, $line );
 195                 self::logError( $e, 'error' );
 196
 197                 // This handler is for logging only. Return false will instruct PHP
 198                 // to continue regular handling.
 199                 return false;
 200         }
 201
 202         /**
 203          * Dual purpose callback used as both a set_error_handler() callback and
 204          * a registered shutdown function. Receive a callback from the interpreter
 205          * for a raised error or system shutdown, check for a fatal error, and log
 206          * to the 'fatal' logging channel.
 207          *
 208          * Special handling is included for missing class errors as they may
 209          * indicate that the user needs to install 3rd-party libraries via
 210          * Composer or other means.
 211          *
 212          * @since 1.25
 213          *
 214          * @param int $level Error level raised
 215          * @param string $message Error message
 216          * @param string $file File that error was raised in
 217          * @param int $line Line number error was raised at
 218          * @param array $context Active symbol table point of error
 219          * @param array $trace Backtrace at point of error (undocumented HHVM
 220          *     feature)
 221          * @return bool Always returns false
 222          */
 223         public static function handleFatalError(
 224                 $level = null, $message = null, $file = null, $line = null,
 225                 $context = null, $trace = null
 226         ) {
 227                 // Free reserved memory so that we have space to process OOM
 228                 // errors
 229                 self::$reservedMemory = null;
 230
 231                 if ( $level === null ) {
 232                         // Called as a shutdown handler, get data from error_get_last()
 233                         if ( static::$handledFatalCallback ) {
 234                                 // Already called once (probably as an error handler callback
 235                                 // under HHVM) so don't log again.
 236                                 return false;
 237                         }
 238
 239                         $lastError = error_get_last();
 240                         if ( $lastError !== null ) {
 241                                 $level = $lastError['type'];
 242                                 $message = $lastError['message'];
 243                                 $file = $lastError['file'];
 244                                 $line = $lastError['line'];
 245                         } else {
 246                                 $level = 0;
 247                                 $message = '';
 248                         }
 249                 }
 250
 251                 if ( !in_array( $level, self::$fatalErrorTypes ) ) {
 252                         // Only interested in fatal errors, others should have been
 253                         // handled by MWExceptionHandler::handleError
 254                         return false;
 255                 }
 256
 257                 $msg = "[{exception_id}] PHP Fatal Error: {$message}";
 258
 259                 // Look at message to see if this is a class not found failure
 260                 // HHVM: Class undefined: foo
 261                 // PHP5: Class 'foo' not found
 262                 if ( preg_match( "/Class (undefined: \w+|'\w+' not found)/", $msg ) ) {
 263                         // @codingStandardsIgnoreStart Generic.Files.LineLength.TooLong
 264                         $msg = <<<TXT
 265 {$msg}
 266
 267 MediaWiki or an installed extension requires this class but it is not embedded directly in MediaWiki's git repository and must be installed separately by the end user.
 268
 269 Please see <a href="https://www.mediawiki.org/wiki/Download_from_Git#Fetch_external_libraries">mediawiki.org</a> for help on installing the required components.
 270 TXT;
 271                         // @codingStandardsIgnoreEnd
 272                 }
 273
 274                 // We can't just create an exception and log it as it is likely that
 275                 // the interpreter has unwound the stack already. If that is true the
 276                 // stacktrace we would get would be functionally empty. If however we
 277                 // have been called as an error handler callback *and* HHVM is in use
 278                 // we will have been provided with a useful stacktrace that we can
 279                 // log.
 280                 $trace = $trace ?: debug_backtrace();
 281                 $logger = LoggerFactory::getInstance( 'fatal' );
 282                 $logger->error( $msg, [
 283                         'exception' => [
 284                                 'class' => 'ErrorException',
 285                                 'message' => "PHP Fatal Error: {$message}",
 286                                 'code' => $level,
 287                                 'file' => $file,
 288                                 'line' => $line,
 289                                 'trace' => static::redactTrace( $trace ),
 290                         ],
 291                         'exception_id' => wfRandomString( 8 ),
 292                 ] );
 293
 294                 // Remember call so we don't double process via HHVM's fatal
 295                 // notifications and the shutdown hook behavior
 296                 static::$handledFatalCallback = true;
 297                 return false;
 298         }
 299
 300         /**
 301          * Generate a string representation of an exception's stack trace
 302          *
 303          * Like Exception::getTraceAsString, but replaces argument values with
 304          * argument type or class name.
 305          *
 306          * @param Exception|Throwable $e
 307          * @return string
 308          * @see prettyPrintTrace()
 309          */
 310         public static function getRedactedTraceAsString( $e ) {
 311                 return self::prettyPrintTrace( self::getRedactedTrace( $e ) );
 312         }
 313
 314         /**
 315          * Generate a string representation of a stacktrace.
 316          *
 317          * @param array $trace
 318          * @param string $pad Constant padding to add to each line of trace
 319          * @return string
 320          * @since 1.26
 321          */
 322         public static function prettyPrintTrace( array $trace, $pad = '' ) {
 323                 $text = '';
 324
 325                 $level = 0;
 326                 foreach ( $trace as $level => $frame ) {
 327                         if ( isset( $frame['file'] ) && isset( $frame['line'] ) ) {
 328                                 $text .= "{$pad}#{$level} {$frame['file']}({$frame['line']}): ";
 329                         } else {
 330                                 // 'file' and 'line' are unset for calls via call_user_func
 331                                 // (bug 55634) This matches behaviour of
 332                                 // Exception::getTraceAsString to instead display "[internal
 333                                 // function]".
 334                                 $text .= "{$pad}#{$level} [internal function]: ";
 335                         }
 336
 337                         if ( isset( $frame['class'] ) && isset( $frame['type'] ) && isset( $frame['function'] ) ) {
 338                                 $text .= $frame['class'] . $frame['type'] . $frame['function'];
 339                         } elseif ( isset( $frame['function'] ) ) {
 340                                 $text .= $frame['function'];
 341                         } else {
 342                                 $text .= 'NO_FUNCTION_GIVEN';
 343                         }
 344
 345                         if ( isset( $frame['args'] ) ) {
 346                                 $text .= '(' . implode( ', ', $frame['args'] ) . ")\n";
 347                         } else {
 348                                 $text .= "()\n";
 349                         }
 350                 }
 351
 352                 $level = $level + 1;
 353                 $text .= "{$pad}#{$level} {main}";
 354
 355                 return $text;
 356         }
 357
 358         /**
 359          * Return a copy of an exception's backtrace as an array.
 360          *
 361          * Like Exception::getTrace, but replaces each element in each frame's
 362          * argument array with the name of its class (if the element is an object)
 363          * or its type (if the element is a PHP primitive).
 364          *
 365          * @since 1.22
 366          * @param Exception|Throwable $e
 367          * @return array
 368          */
 369         public static function getRedactedTrace( $e ) {
 370                 return static::redactTrace( $e->getTrace() );
 371         }
 372
 373         /**
 374          * Redact a stacktrace generated by Exception::getTrace(),
 375          * debug_backtrace() or similar means. Replaces each element in each
 376          * frame's argument array with the name of its class (if the element is an
 377          * object) or its type (if the element is a PHP primitive).
 378          *
 379          * @since 1.26
 380          * @param array $trace Stacktrace
 381          * @return array Stacktrace with arugment values converted to data types
 382          */
 383         public static function redactTrace( array $trace ) {
 384                 return array_map( function ( $frame ) {
 385                         if ( isset( $frame['args'] ) ) {
 386                                 $frame['args'] = array_map( function ( $arg ) {
 387                                         return is_object( $arg ) ? get_class( $arg ) : gettype( $arg );
 388                                 }, $frame['args'] );
 389                         }
 390                         return $frame;
 391                 }, $trace );
 392         }
 393
 394         /**
 395          * Get the ID for this exception.
 396          *
 397          * The ID is saved so that one can match the one output to the user (when
 398          * $wgShowExceptionDetails is set to false), to the entry in the debug log.
 399          *
 400          * @since 1.22
 401          * @deprecated since 1.27: Exception IDs are synonymous with request IDs.
 402          * @param Exception|Throwable $e
 403          * @return string
 404          */
 405         public static function getLogId( $e ) {
 406                 wfDeprecated( __METHOD__, '1.27' );
 407                 return WebRequest::getRequestId();
 408         }
 409
 410         /**
 411          * If the exception occurred in the course of responding to a request,
 412          * returns the requested URL. Otherwise, returns false.
 413          *
 414          * @since 1.23
 415          * @return string|false
 416          */
 417         public static function getURL() {
 418                 global $wgRequest;
 419                 if ( !isset( $wgRequest ) || $wgRequest instanceof FauxRequest ) {
 420                         return false;
 421                 }
 422                 return $wgRequest->getRequestURL();
 423         }
 424
 425         /**
 426          * Get a message formatting the exception message and its origin.
 427          *
 428          * @since 1.22
 429          * @param Exception|Throwable $e
 430          * @return string
 431          */
 432         public static function getLogMessage( $e ) {
 433                 $id = WebRequest::getRequestId();
 434                 $type = get_class( $e );
 435                 $file = $e->getFile();
 436                 $line = $e->getLine();
 437                 $message = $e->getMessage();
 438                 $url = self::getURL() ?: '[no req]';
 439
 440                 return "[$id] $url   $type from line $line of $file: $message";
 441         }
 442
 443         /**
 444          * @param Exception|Throwable $e
 445          * @return string
 446          */
 447         public static function getPublicLogMessage( $e ) {
 448                 $reqId = WebRequest::getRequestId();
 449                 $type = get_class( $e );
 450                 return '[' . $reqId . '] '
 451                         . gmdate( 'Y-m-d H:i:s' ) . ': '
 452                         . 'Fatal exception of type "' . $type . '"';
 453         }
 454
 455         /**
 456          * Get a PSR-3 log event context from an Exception.
 457          *
 458          * Creates a structured array containing information about the provided
 459          * exception that can be used to augment a log message sent to a PSR-3
 460          * logger.
 461          *
 462          * @param Exception|Throwable $e
 463          * @return array
 464          */
 465         public static function getLogContext( $e ) {
 466                 return [
 467                         'exception' => $e,
 468                         'exception_id' => WebRequest::getRequestId(),
 469                 ];
 470         }
 471
 472         /**
 473          * Get a structured representation of an Exception.
 474          *
 475          * Returns an array of structured data (class, message, code, file,
 476          * backtrace) derived from the given exception. The backtrace information
 477          * will be redacted as per getRedactedTraceAsArray().
 478          *
 479          * @param Exception|Throwable $e
 480          * @return array
 481          * @since 1.26
 482          */
 483         public static function getStructuredExceptionData( $e ) {
 484                 global $wgLogExceptionBacktrace;
 485                 $data = [
 486                         'id' => WebRequest::getRequestId(),
 487                         'type' => get_class( $e ),
 488                         'file' => $e->getFile(),
 489                         'line' => $e->getLine(),
 490                         'message' => $e->getMessage(),
 491                         'code' => $e->getCode(),
 492                         'url' => self::getURL() ?: null,
 493                 ];
 494
 495                 if ( $e instanceof ErrorException &&
 496                         ( error_reporting() & $e->getSeverity() ) === 0
 497                 ) {
 498                         // Flag surpressed errors
 499                         $data['suppressed'] = true;
 500                 }
 501
 502                 if ( $wgLogExceptionBacktrace ) {
 503                         $data['backtrace'] = self::getRedactedTrace( $e );
 504                 }
 505
 506                 $previous = $e->getPrevious();
 507                 if ( $previous !== null ) {
 508                         $data['previous'] = self::getStructuredExceptionData( $previous );
 509                 }
 510
 511                 return $data;
 512         }
 513
 514         /**
 515          * Serialize an Exception object to JSON.
 516          *
 517          * The JSON object will have keys 'id', 'file', 'line', 'message', and
 518          * 'url'. These keys map to string values, with the exception of 'line',
 519          * which is a number, and 'url', which may be either a string URL or or
 520          * null if the exception did not occur in the context of serving a web
 521          * request.
 522          *
 523          * If $wgLogExceptionBacktrace is true, it will also have a 'backtrace'
 524          * key, mapped to the array return value of Exception::getTrace, but with
 525          * each element in each frame's "args" array (if set) replaced with the
 526          * argument's class name (if the argument is an object) or type name (if
 527          * the argument is a PHP primitive).
 528          *
 529          * @par Sample JSON record ($wgLogExceptionBacktrace = false):
 530          * @code
 531          *  {
 532          *    "id": "c41fb419",
 533          *    "type": "MWException",
 534          *    "file": "/var/www/mediawiki/includes/cache/MessageCache.php",
 535          *    "line": 704,
 536          *    "message": "Non-string key given",
 537          *    "url": "/wiki/Main_Page"
 538          *  }
 539          * @endcode
 540          *
 541          * @par Sample JSON record ($wgLogExceptionBacktrace = true):
 542          * @code
 543          *  {
 544          *    "id": "dc457938",
 545          *    "type": "MWException",
 546          *    "file": "/vagrant/mediawiki/includes/cache/MessageCache.php",
 547          *    "line": 704,
 548          *    "message": "Non-string key given",
 549          *    "url": "/wiki/Main_Page",
 550          *    "backtrace": [{
 551          *      "file": "/vagrant/mediawiki/extensions/VisualEditor/VisualEditor.hooks.php",
 552          *      "line": 80,
 553          *      "function": "get",
 554          *      "class": "MessageCache",
 555          *      "type": "->",
 556          *      "args": ["array"]
 557          *    }]
 558          *  }
 559          * @endcode
 560          *
 561          * @since 1.23
 562          * @param Exception|Throwable $e
 563          * @param bool $pretty Add non-significant whitespace to improve readability (default: false).
 564          * @param int $escaping Bitfield consisting of FormatJson::.*_OK class constants.
 565          * @return string|false JSON string if successful; false upon failure
 566          */
 567         public static function jsonSerializeException( $e, $pretty = false, $escaping = 0 ) {
 568                 $data = self::getStructuredExceptionData( $e );
 569                 return FormatJson::encode( $data, $pretty, $escaping );
 570         }
 571
 572         /**
 573          * Log an exception to the exception log (if enabled).
 574          *
 575          * This method must not assume the exception is an MWException,
 576          * it is also used to handle PHP exceptions or exceptions from other libraries.
 577          *
 578          * @since 1.22
 579          * @param Exception|Throwable $e
 580          */
 581         public static function logException( $e ) {
 582                 if ( !( $e instanceof MWException ) || $e->isLoggable() ) {
 583                         $logger = LoggerFactory::getInstance( 'exception' );
 584                         $logger->error(
 585                                 self::getLogMessage( $e ),
 586                                 self::getLogContext( $e )
 587                         );
 588
 589                         $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 590                         if ( $json !== false ) {
 591                                 $logger = LoggerFactory::getInstance( 'exception-json' );
 592                                 $logger->error( $json, [ 'private' => true ] );
 593                         }
 594
 595                         Hooks::run( 'LogException', [ $e, false ] );
 596                 }
 597         }
 598
 599         /**
 600          * Log an exception that wasn't thrown but made to wrap an error.
 601          *
 602          * @since 1.25
 603          * @param ErrorException $e
 604          * @param string $channel
 605         */
 606         protected static function logError( ErrorException $e, $channel ) {
 607                 // The set_error_handler callback is independent from error_reporting.
 608                 // Filter out unwanted errors manually (e.g. when
 609                 // MediaWiki\suppressWarnings is active).
 610                 $suppressed = ( error_reporting() & $e->getSeverity() ) === 0;
 611                 if ( !$suppressed ) {
 612                         $logger = LoggerFactory::getInstance( $channel );
 613                         $logger->error(
 614                                 self::getLogMessage( $e ),
 615                                 self::getLogContext( $e )
 616                         );
 617                 }
 618
 619                 // Include all errors in the json log (surpressed errors will be flagged)
 620                 $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 621                 if ( $json !== false ) {
 622                         $logger = LoggerFactory::getInstance( "{$channel}-json" );
 623                         $logger->error( $json, [ 'private' => true ] );
 624                 }
 625
 626                 Hooks::run( 'LogException', [ $e, $suppressed ] );
 627         }
 628 }