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
  23 /**
  24  * Handler class for MWExceptions
  25  * @ingroup Exception
  26  */
  27 class MWExceptionHandler {
  28
  29         /**
  30          * @var string $reservedMemory
  31          */
  32         protected static $reservedMemory;
  33         /**
  34          * @var array $fatalErrorTypes
  35          */
  36         protected static $fatalErrorTypes = array(
  37                 E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR,
  38                 /* HHVM's FATAL_ERROR level */ 16777217,
  39         );
  40         /**
  41          * @var bool $handledFatalCallback
  42          */
  43         protected static $handledFatalCallback = false;
  44
  45         /**
  46          * Install handlers with PHP.
  47          */
  48         public static function installHandler() {
  49                 set_exception_handler( 'MWExceptionHandler::handleException' );
  50                 set_error_handler( 'MWExceptionHandler::handleError' );
  51
  52                 // Reserve 16k of memory so we can report OOM fatals
  53                 self::$reservedMemory = str_repeat( ' ', 16384 );
  54                 register_shutdown_function( 'MWExceptionHandler::handleFatalError' );
  55         }
  56
  57         /**
  58          * Report an exception to the user
  59          * @param Exception $e
  60          */
  61         protected static function report( Exception $e ) {
  62                 global $wgShowExceptionDetails;
  63
  64                 $cmdLine = MWException::isCommandLine();
  65
  66                 if ( $e instanceof MWException ) {
  67                         try {
  68                                 // Try and show the exception prettily, with the normal skin infrastructure
  69                                 $e->report();
  70                         } catch ( Exception $e2 ) {
  71                                 // Exception occurred from within exception handler
  72                                 // Show a simpler message for the original exception,
  73                                 // don't try to invoke report()
  74                                 $message = "MediaWiki internal error.\n\n";
  75
  76                                 if ( $wgShowExceptionDetails ) {
  77                                         $message .= 'Original exception: ' . self::getLogMessage( $e ) .
  78                                                 "\nBacktrace:\n" . self::getRedactedTraceAsString( $e ) .
  79                                                 "\n\nException caught inside exception handler: " . self::getLogMessage( $e2 ) .
  80                                                 "\nBacktrace:\n" . self::getRedactedTraceAsString( $e2 );
  81                                 } else {
  82                                         $message .= "Exception caught inside exception handler.\n\n" .
  83                                                 "Set \$wgShowExceptionDetails = true; at the bottom of LocalSettings.php " .
  84                                                 "to show detailed debugging information.";
  85                                 }
  86
  87                                 $message .= "\n";
  88
  89                                 if ( $cmdLine ) {
  90                                         self::printError( $message );
  91                                 } else {
  92                                         echo nl2br( htmlspecialchars( $message ) ) . "\n";
  93                                 }
  94                         }
  95                 } else {
  96                         $message = "Exception encountered, of type \"" . get_class( $e ) . "\"";
  97
  98                         if ( $wgShowExceptionDetails ) {
  99                                 $message .= "\n" . self::getLogMessage( $e ) . "\nBacktrace:\n" .
 100                                         self::getRedactedTraceAsString( $e ) . "\n";
 101                         }
 102
 103                         if ( $cmdLine ) {
 104                                 self::printError( $message );
 105                         } else {
 106                                 echo nl2br( htmlspecialchars( $message ) ) . "\n";
 107                         }
 108
 109                 }
 110         }
 111
 112         /**
 113          * Print a message, if possible to STDERR.
 114          * Use this in command line mode only (see isCommandLine)
 115          *
 116          * @param string $message Failure text
 117          */
 118         public static function printError( $message ) {
 119                 # NOTE: STDERR may not be available, especially if php-cgi is used from the
 120                 # command line (bug #15602). Try to produce meaningful output anyway. Using
 121                 # echo may corrupt output to STDOUT though.
 122                 if ( defined( 'STDERR' ) ) {
 123                         fwrite( STDERR, $message );
 124                 } else {
 125                         echo $message;
 126                 }
 127         }
 128
 129         /**
 130          * If there are any open database transactions, roll them back and log
 131          * the stack trace of the exception that should have been caught so the
 132          * transaction could be aborted properly.
 133          *
 134          * @since 1.23
 135          * @param Exception $e
 136          */
 137         public static function rollbackMasterChangesAndLog( Exception $e ) {
 138                 $factory = wfGetLBFactory();
 139                 if ( $factory->hasMasterChanges() ) {
 140                         $logger = LoggerFactory::getInstance( 'Bug56269' );
 141                         $logger->warning(
 142                                 'Exception thrown with an uncommited database transaction: ' .
 143                                 self::getLogMessage( $e ),
 144                                 self::getLogContext( $e )
 145                         );
 146                         $factory->rollbackMasterChanges();
 147                 }
 148         }
 149
 150         /**
 151          * Exception handler which simulates the appropriate catch() handling:
 152          *
 153          *   try {
 154          *       ...
 155          *   } catch ( Exception $e ) {
 156          *       $e->report();
 157          *   } catch ( Exception $e ) {
 158          *       echo $e->__toString();
 159          *   }
 160          *
 161          * @since 1.25
 162          * @param Exception $e
 163          */
 164         public static function handleException( Exception $e ) {
 165                 try {
 166                         // Rollback DBs to avoid transaction notices. This may fail
 167                         // to rollback some DB due to connection issues or exceptions.
 168                         // However, any sane DB driver will rollback implicitly anyway.
 169                         self::rollbackMasterChangesAndLog( $e );
 170                 } catch ( DBError $e2 ) {
 171                         // If the DB is unreacheable, rollback() will throw an error
 172                         // and the error report() method might need messages from the DB,
 173                         // which would result in an exception loop. PHP may escalate such
 174                         // errors to "Exception thrown without a stack frame" fatals, but
 175                         // it's better to be explicit here.
 176                         self::logException( $e2 );
 177                 }
 178
 179                 self::logException( $e );
 180                 self::report( $e );
 181
 182                 // Exit value should be nonzero for the benefit of shell jobs
 183                 exit( 1 );
 184         }
 185
 186         /**
 187          * Handler for set_error_handler() callback notifications.
 188          *
 189          * Receive a callback from the interpreter for a raised error, create an
 190          * ErrorException, and log the exception to the 'error' logging
 191          * channel(s). If the raised error is a fatal error type (only under HHVM)
 192          * delegate to handleFatalError() instead.
 193          *
 194          * @since 1.25
 195          *
 196          * @param int $level Error level raised
 197          * @param string $message
 198          * @param string $file
 199          * @param int $line
 200          *
 201          * @see logError()
 202          */
 203         public static function handleError(
 204                 $level, $message, $file = null, $line = null
 205         ) {
 206                 if ( in_array( $level, self::$fatalErrorTypes ) ) {
 207                         return call_user_func_array(
 208                                 'MWExceptionHandler::handleFatalError', func_get_args()
 209                         );
 210                 }
 211
 212                 // Map error constant to error name (reverse-engineer PHP error
 213                 // reporting)
 214                 switch ( $level ) {
 215                         case E_RECOVERABLE_ERROR:
 216                                 $levelName = 'Error';
 217                                 break;
 218                         case E_WARNING:
 219                         case E_CORE_WARNING:
 220                         case E_COMPILE_WARNING:
 221                         case E_USER_WARNING:
 222                                 $levelName = 'Warning';
 223                                 break;
 224                         case E_NOTICE:
 225                         case E_USER_NOTICE:
 226                                 $levelName = 'Notice';
 227                                 break;
 228                         case E_STRICT:
 229                                 $levelName = 'Strict Standards';
 230                                 break;
 231                         case E_DEPRECATED:
 232                         case E_USER_DEPRECATED:
 233                                 $levelName = 'Deprecated';
 234                                 break;
 235                         default:
 236                                 $levelName = 'Unknown error';
 237                                 break;
 238                 }
 239
 240                 $e = new ErrorException( "PHP $levelName: $message", 0, $level, $file, $line );
 241                 self::logError( $e, 'error' );
 242
 243                 // This handler is for logging only. Return false will instruct PHP
 244                 // to continue regular handling.
 245                 return false;
 246         }
 247
 248
 249         /**
 250          * Dual purpose callback used as both a set_error_handler() callback and
 251          * a registered shutdown function. Receive a callback from the interpreter
 252          * for a raised error or system shutdown, check for a fatal error, and log
 253          * to the 'fatal' logging channel.
 254          *
 255          * Special handling is included for missing class errors as they may
 256          * indicate that the user needs to install 3rd-party libraries via
 257          * Composer or other means.
 258          *
 259          * @since 1.25
 260          *
 261          * @param int $level Error level raised
 262          * @param string $message Error message
 263          * @param string $file File that error was raised in
 264          * @param int $line Line number error was raised at
 265          * @param array $context Active symbol table point of error
 266          * @param array $trace Backtrace at point of error (undocumented HHVM
 267          *     feature)
 268          * @return bool Always returns false
 269          */
 270         public static function handleFatalError(
 271                 $level = null, $message = null, $file = null, $line = null,
 272                 $context = null, $trace = null
 273         ) {
 274                 // Free reserved memory so that we have space to process OOM
 275                 // errors
 276                 self::$reservedMemory = null;
 277
 278                 if ( $level === null ) {
 279                         // Called as a shutdown handler, get data from error_get_last()
 280                         if ( static::$handledFatalCallback ) {
 281                                 // Already called once (probably as an error handler callback
 282                                 // under HHVM) so don't log again.
 283                                 return false;
 284                         }
 285
 286                         $lastError = error_get_last();
 287                         if ( $lastError !== null ) {
 288                                 $level = $lastError['type'];
 289                                 $message = $lastError['message'];
 290                                 $file = $lastError['file'];
 291                                 $line = $lastError['line'];
 292                         } else {
 293                                 $level = 0;
 294                                 $message = '';
 295                         }
 296                 }
 297
 298                 if ( !in_array( $level, self::$fatalErrorTypes ) ) {
 299                         // Only interested in fatal errors, others should have been
 300                         // handled by MWExceptionHandler::handleError
 301                         return false;
 302                 }
 303
 304                 $msg = "[{exception_id}] PHP Fatal Error: {$message}";
 305
 306                 // Look at message to see if this is a class not found failure
 307                 // HHVM: Class undefined: foo
 308                 // PHP5: Class 'foo' not found
 309                 if ( preg_match( "/Class (undefined: \w+|'\w+' not found)/", $msg ) ) {
 310                         // @codingStandardsIgnoreStart Generic.Files.LineLength.TooLong
 311                         $msg = <<<TXT
 312 {$msg}
 313
 314 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.
 315
 316 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.
 317 TXT;
 318                         // @codingStandardsIgnoreEnd
 319                 }
 320
 321                 // We can't just create an exception and log it as it is likely that
 322                 // the interpreter has unwound the stack already. If that is true the
 323                 // stacktrace we would get would be functionally empty. If however we
 324                 // have been called as an error handler callback *and* HHVM is in use
 325                 // we will have been provided with a useful stacktrace that we can
 326                 // log.
 327                 $trace = $trace ?: debug_backtrace();
 328                 $logger = LoggerFactory::getInstance( 'fatal' );
 329                 $logger->error( $msg, array(
 330                         'exception' => array(
 331                                 'class' => 'ErrorException',
 332                                 'message' => "PHP Fatal Error: {$message}",
 333                                 'code' => $level,
 334                                 'file' => $file,
 335                                 'line' => $line,
 336                                 'trace' => static::redactTrace( $trace ),
 337                         ),
 338                         'exception_id' => wfRandomString( 8 ),
 339                 ) );
 340
 341                 // Remember call so we don't double process via HHVM's fatal
 342                 // notifications and the shutdown hook behavior
 343                 static::$handledFatalCallback = true;
 344                 return false;
 345         }
 346
 347         /**
 348          * Generate a string representation of an exception's stack trace
 349          *
 350          * Like Exception::getTraceAsString, but replaces argument values with
 351          * argument type or class name.
 352          *
 353          * @param Exception $e
 354          * @return string
 355          * @see prettyPrintTrace()
 356          */
 357         public static function getRedactedTraceAsString( Exception $e ) {
 358                 return self::prettyPrintTrace( self::getRedactedTrace( $e ) );
 359         }
 360
 361         /**
 362          * Generate a string representation of a stacktrace.
 363          *
 364          * @param array $trace
 365          * @param string $pad Constant padding to add to each line of trace
 366          * @return string
 367          * @since 1.26
 368          */
 369         public static function prettyPrintTrace( array $trace, $pad = '' ) {
 370                 $text = '';
 371
 372                 foreach ( $trace as $level => $frame ) {
 373                         if ( isset( $frame['file'] ) && isset( $frame['line'] ) ) {
 374                                 $text .= "{$pad}#{$level} {$frame['file']}({$frame['line']}): ";
 375                         } else {
 376                                 // 'file' and 'line' are unset for calls via call_user_func
 377                                 // (bug 55634) This matches behaviour of
 378                                 // Exception::getTraceAsString to instead display "[internal
 379                                 // function]".
 380                                 $text .= "{$pad}#{$level} [internal function]: ";
 381                         }
 382
 383                         if ( isset( $frame['class'] ) ) {
 384                                 $text .= $frame['class'] . $frame['type'] . $frame['function'];
 385                         } else {
 386                                 $text .= $frame['function'];
 387                         }
 388
 389                         if ( isset( $frame['args'] ) ) {
 390                                 $text .= '(' . implode( ', ', $frame['args'] ) . ")\n";
 391                         } else {
 392                                 $text .= "()\n";
 393                         }
 394                 }
 395
 396                 $level = $level + 1;
 397                 $text .= "{$pad}#{$level} {main}";
 398
 399                 return $text;
 400         }
 401
 402         /**
 403          * Return a copy of an exception's backtrace as an array.
 404          *
 405          * Like Exception::getTrace, but replaces each element in each frame's
 406          * argument array with the name of its class (if the element is an object)
 407          * or its type (if the element is a PHP primitive).
 408          *
 409          * @since 1.22
 410          * @param Exception $e
 411          * @return array
 412          */
 413         public static function getRedactedTrace( Exception $e ) {
 414                 return static::redactTrace( $e->getTrace() );
 415         }
 416
 417         /**
 418          * Redact a stacktrace generated by Exception::getTrace(),
 419          * debug_backtrace() or similar means. Replaces each element in each
 420          * frame's argument array with the name of its class (if the element is an
 421          * object) or its type (if the element is a PHP primitive).
 422          *
 423          * @since 1.26
 424          * @param array $trace Stacktrace
 425          * @return array Stacktrace with arugment values converted to data types
 426          */
 427         public static function redactTrace( array $trace ) {
 428                 return array_map( function ( $frame ) {
 429                         if ( isset( $frame['args'] ) ) {
 430                                 $frame['args'] = array_map( function ( $arg ) {
 431                                         return is_object( $arg ) ? get_class( $arg ) : gettype( $arg );
 432                                 }, $frame['args'] );
 433                         }
 434                         return $frame;
 435                 }, $trace );
 436         }
 437
 438         /**
 439          * Get the ID for this exception.
 440          *
 441          * The ID is saved so that one can match the one output to the user (when
 442          * $wgShowExceptionDetails is set to false), to the entry in the debug log.
 443          *
 444          * @since 1.22
 445          * @param Exception $e
 446          * @return string
 447          */
 448         public static function getLogId( Exception $e ) {
 449                 if ( !isset( $e->_mwLogId ) ) {
 450                         $e->_mwLogId = wfRandomString( 8 );
 451                 }
 452                 return $e->_mwLogId;
 453         }
 454
 455         /**
 456          * If the exception occurred in the course of responding to a request,
 457          * returns the requested URL. Otherwise, returns false.
 458          *
 459          * @since 1.23
 460          * @return string|false
 461          */
 462         public static function getURL() {
 463                 global $wgRequest;
 464                 if ( !isset( $wgRequest ) || $wgRequest instanceof FauxRequest ) {
 465                         return false;
 466                 }
 467                 return $wgRequest->getRequestURL();
 468         }
 469
 470         /**
 471          * Get a message formatting the exception message and its origin.
 472          *
 473          * @since 1.22
 474          * @param Exception $e
 475          * @return string
 476          */
 477         public static function getLogMessage( Exception $e ) {
 478                 $id = self::getLogId( $e );
 479                 $type = get_class( $e );
 480                 $file = $e->getFile();
 481                 $line = $e->getLine();
 482                 $message = $e->getMessage();
 483                 $url = self::getURL() ?: '[no req]';
 484
 485                 return "[$id] $url   $type from line $line of $file: $message";
 486         }
 487
 488         /**
 489          * Get a PSR-3 log event context from an Exception.
 490          *
 491          * Creates a structured array containing information about the provided
 492          * exception that can be used to augment a log message sent to a PSR-3
 493          * logger.
 494          *
 495          * @param Exception $e
 496          * @return array
 497          */
 498         public static function getLogContext( Exception $e ) {
 499                 return array(
 500                         'exception' => $e,
 501                         'exception_id' => static::getLogId( $e ),
 502                 );
 503         }
 504
 505         /**
 506          * Get a structured representation of an Exception.
 507          *
 508          * Returns an array of structured data (class, message, code, file,
 509          * backtrace) derived from the given exception. The backtrace information
 510          * will be redacted as per getRedactedTraceAsArray().
 511          *
 512          * @param Exception $e
 513          * @return array
 514          * @since 1.26
 515          */
 516         public static function getStructuredExceptionData( Exception $e ) {
 517                 global $wgLogExceptionBacktrace;
 518                 $data = array(
 519                         'id' => self::getLogId( $e ),
 520                         'type' => get_class( $e ),
 521                         'file' => $e->getFile(),
 522                         'line' => $e->getLine(),
 523                         'message' => $e->getMessage(),
 524                         'code' => $e->getCode(),
 525                         'url' => self::getURL() ?: null,
 526                 );
 527
 528                 if ( $e instanceof ErrorException &&
 529                         ( error_reporting() & $e->getSeverity() ) === 0
 530                 ) {
 531                         // Flag surpressed errors
 532                         $data['suppressed'] = true;
 533                 }
 534
 535                 if ( $wgLogExceptionBacktrace ) {
 536                         $data['backtrace'] = self::getRedactedTrace( $e );
 537                 }
 538
 539                 $previous = $e->getPrevious();
 540                 if ( $previous !== null ) {
 541                         $data['previous'] = self::getStructuredExceptionData( $previous );
 542                 }
 543
 544                 return $data;
 545         }
 546
 547         /**
 548          * Serialize an Exception object to JSON.
 549          *
 550          * The JSON object will have keys 'id', 'file', 'line', 'message', and
 551          * 'url'. These keys map to string values, with the exception of 'line',
 552          * which is a number, and 'url', which may be either a string URL or or
 553          * null if the exception did not occur in the context of serving a web
 554          * request.
 555          *
 556          * If $wgLogExceptionBacktrace is true, it will also have a 'backtrace'
 557          * key, mapped to the array return value of Exception::getTrace, but with
 558          * each element in each frame's "args" array (if set) replaced with the
 559          * argument's class name (if the argument is an object) or type name (if
 560          * the argument is a PHP primitive).
 561          *
 562          * @par Sample JSON record ($wgLogExceptionBacktrace = false):
 563          * @code
 564          *  {
 565          *    "id": "c41fb419",
 566          *    "type": "MWException",
 567          *    "file": "/var/www/mediawiki/includes/cache/MessageCache.php",
 568          *    "line": 704,
 569          *    "message": "Non-string key given",
 570          *    "url": "/wiki/Main_Page"
 571          *  }
 572          * @endcode
 573          *
 574          * @par Sample JSON record ($wgLogExceptionBacktrace = true):
 575          * @code
 576          *  {
 577          *    "id": "dc457938",
 578          *    "type": "MWException",
 579          *    "file": "/vagrant/mediawiki/includes/cache/MessageCache.php",
 580          *    "line": 704,
 581          *    "message": "Non-string key given",
 582          *    "url": "/wiki/Main_Page",
 583          *    "backtrace": [{
 584          *      "file": "/vagrant/mediawiki/extensions/VisualEditor/VisualEditor.hooks.php",
 585          *      "line": 80,
 586          *      "function": "get",
 587          *      "class": "MessageCache",
 588          *      "type": "->",
 589          *      "args": ["array"]
 590          *    }]
 591          *  }
 592          * @endcode
 593          *
 594          * @since 1.23
 595          * @param Exception $e
 596          * @param bool $pretty Add non-significant whitespace to improve readability (default: false).
 597          * @param int $escaping Bitfield consisting of FormatJson::.*_OK class constants.
 598          * @return string|false JSON string if successful; false upon failure
 599          */
 600         public static function jsonSerializeException( Exception $e, $pretty = false, $escaping = 0 ) {
 601                 $data = self::getStructuredExceptionData( $e );
 602                 return FormatJson::encode( $data, $pretty, $escaping );
 603         }
 604
 605         /**
 606          * Log an exception to the exception log (if enabled).
 607          *
 608          * This method must not assume the exception is an MWException,
 609          * it is also used to handle PHP exceptions or exceptions from other libraries.
 610          *
 611          * @since 1.22
 612          * @param Exception $e
 613          */
 614         public static function logException( Exception $e ) {
 615                 if ( !( $e instanceof MWException ) || $e->isLoggable() ) {
 616                         $logger = LoggerFactory::getInstance( 'exception' );
 617                         $logger->error(
 618                                 self::getLogMessage( $e ),
 619                                 self::getLogContext( $e )
 620                         );
 621
 622                         $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 623                         if ( $json !== false ) {
 624                                 $logger = LoggerFactory::getInstance( 'exception-json' );
 625                                 $logger->error( $json, array( 'private' => true ) );
 626                         }
 627
 628                         Hooks::run( 'LogException', array( $e, false ) );
 629                 }
 630         }
 631
 632         /**
 633          * Log an exception that wasn't thrown but made to wrap an error.
 634          *
 635          * @since 1.25
 636          * @param ErrorException $e
 637          * @param string $channel
 638         */
 639         protected static function logError( ErrorException $e, $channel ) {
 640                 // The set_error_handler callback is independent from error_reporting.
 641                 // Filter out unwanted errors manually (e.g. when
 642                 // MediaWiki\suppressWarnings is active).
 643                 $suppressed = ( error_reporting() & $e->getSeverity() ) === 0;
 644                 if ( !$suppressed ) {
 645                         $logger = LoggerFactory::getInstance( $channel );
 646                         $logger->error(
 647                                 self::getLogMessage( $e ),
 648                                 self::getLogContext( $e )
 649                         );
 650                 }
 651
 652                 // Include all errors in the json log (surpressed errors will be flagged)
 653                 $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 654                 if ( $json !== false ) {
 655                         $logger = LoggerFactory::getInstance( "{$channel}-json" );
 656                         $logger->error( $json, array( 'private' => true ) );
 657                 }
 658
 659                 Hooks::run( 'LogException', array( $e, $suppressed ) );
 660         }
 661 }