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 /**
  22  * Handler class for MWExceptions
  23  * @ingroup Exception
  24  */
  25 class MWExceptionHandler {
  26
  27         protected static $reservedMemory;
  28         protected static $fatalErrorTypes = array(
  29                 E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR,
  30                 /* HHVM's FATAL_ERROR level */ 16777217,
  31         );
  32
  33         /**
  34          * Install handlers with PHP.
  35          */
  36         public static function installHandler() {
  37                 set_exception_handler( array( 'MWExceptionHandler', 'handleException' ) );
  38                 set_error_handler( array( 'MWExceptionHandler', 'handleError' ) );
  39
  40                 // Reserve 16k of memory so we can report OOM fatals
  41                 self::$reservedMemory = str_repeat( ' ', 16384 );
  42                 register_shutdown_function(
  43                         array( 'MWExceptionHandler', 'handleFatalError' )
  44                 );
  45         }
  46
  47         /**
  48          * Report an exception to the user
  49          * @param Exception $e
  50          */
  51         protected static function report( Exception $e ) {
  52                 global $wgShowExceptionDetails;
  53
  54                 $cmdLine = MWException::isCommandLine();
  55
  56                 if ( $e instanceof MWException ) {
  57                         try {
  58                                 // Try and show the exception prettily, with the normal skin infrastructure
  59                                 $e->report();
  60                         } catch ( Exception $e2 ) {
  61                                 // Exception occurred from within exception handler
  62                                 // Show a simpler message for the original exception,
  63                                 // don't try to invoke report()
  64                                 $message = "MediaWiki internal error.\n\n";
  65
  66                                 if ( $wgShowExceptionDetails ) {
  67                                         $message .= 'Original exception: ' . self::getLogMessage( $e ) .
  68                                                 "\nBacktrace:\n" . self::getRedactedTraceAsString( $e ) .
  69                                                 "\n\nException caught inside exception handler: " . self::getLogMessage( $e2 ) .
  70                                                 "\nBacktrace:\n" . self::getRedactedTraceAsString( $e2 );
  71                                 } else {
  72                                         $message .= "Exception caught inside exception handler.\n\n" .
  73                                                 "Set \$wgShowExceptionDetails = true; at the bottom of LocalSettings.php " .
  74                                                 "to show detailed debugging information.";
  75                                 }
  76
  77                                 $message .= "\n";
  78
  79                                 if ( $cmdLine ) {
  80                                         self::printError( $message );
  81                                 } else {
  82                                         echo nl2br( htmlspecialchars( $message ) ) . "\n";
  83                                 }
  84                         }
  85                 } else {
  86                         $message = "Exception encountered, of type \"" . get_class( $e ) . "\"";
  87
  88                         if ( $wgShowExceptionDetails ) {
  89                                 $message .= "\n" . MWExceptionHandler::getLogMessage( $e ) . "\nBacktrace:\n" .
  90                                         self::getRedactedTraceAsString( $e ) . "\n";
  91                         }
  92
  93                         if ( $cmdLine ) {
  94                                 self::printError( $message );
  95                         } else {
  96                                 echo nl2br( htmlspecialchars( $message ) ) . "\n";
  97                         }
  98
  99                 }
 100         }
 101
 102         /**
 103          * Print a message, if possible to STDERR.
 104          * Use this in command line mode only (see isCommandLine)
 105          *
 106          * @param string $message Failure text
 107          */
 108         public static function printError( $message ) {
 109                 # NOTE: STDERR may not be available, especially if php-cgi is used from the
 110                 # command line (bug #15602). Try to produce meaningful output anyway. Using
 111                 # echo may corrupt output to STDOUT though.
 112                 if ( defined( 'STDERR' ) ) {
 113                         fwrite( STDERR, $message );
 114                 } else {
 115                         echo $message;
 116                 }
 117         }
 118
 119         /**
 120          * If there are any open database transactions, roll them back and log
 121          * the stack trace of the exception that should have been caught so the
 122          * transaction could be aborted properly.
 123          *
 124          * @since 1.23
 125          * @param Exception $e
 126          */
 127         public static function rollbackMasterChangesAndLog( Exception $e ) {
 128                 $factory = wfGetLBFactory();
 129                 if ( $factory->hasMasterChanges() ) {
 130                         wfDebugLog( 'Bug56269',
 131                                 'Exception thrown with an uncommited database transaction: ' .
 132                                         MWExceptionHandler::getLogMessage( $e ) . "\n" .
 133                                         $e->getTraceAsString()
 134                         );
 135                         $factory->rollbackMasterChanges();
 136                 }
 137         }
 138
 139         /**
 140          * Exception handler which simulates the appropriate catch() handling:
 141          *
 142          *   try {
 143          *       ...
 144          *   } catch ( Exception $e ) {
 145          *       $e->report();
 146          *   } catch ( Exception $e ) {
 147          *       echo $e->__toString();
 148          *   }
 149          *
 150          * @since 1.25
 151          * @param Exception $e
 152          */
 153         public static function handleException( $e ) {
 154                 global $wgFullyInitialised;
 155
 156                 self::rollbackMasterChangesAndLog( $e );
 157                 self::logException( $e );
 158                 self::report( $e );
 159
 160                 // Final cleanup
 161                 if ( $wgFullyInitialised ) {
 162                         try {
 163                                 // uses $wgRequest, hence the $wgFullyInitialised condition
 164                                 wfLogProfilingData();
 165                         } catch ( Exception $e ) {
 166                         }
 167                 }
 168
 169                 // Exit value should be nonzero for the benefit of shell jobs
 170                 exit( 1 );
 171         }
 172
 173         /**
 174          * @since 1.25
 175          * @param int $level Error level raised
 176          * @param string $message
 177          * @param string $file
 178          * @param int $line
 179          */
 180         public static function handleError( $level, $message, $file = null, $line = null ) {
 181                 // Map error constant to error name (reverse-engineer PHP error reporting)
 182                 switch ( $level ) {
 183                         case E_ERROR:
 184                         case E_CORE_ERROR:
 185                         case E_COMPILE_ERROR:
 186                         case E_USER_ERROR:
 187                         case E_RECOVERABLE_ERROR:
 188                         case E_PARSE:
 189                                 $levelName = 'Error';
 190                                 break;
 191                         case E_WARNING:
 192                         case E_CORE_WARNING:
 193                         case E_COMPILE_WARNING:
 194                         case E_USER_WARNING:
 195                                 $levelName = 'Warning';
 196                                 break;
 197                         case E_NOTICE:
 198                         case E_USER_NOTICE:
 199                                 $levelName = 'Notice';
 200                                 break;
 201                         case E_STRICT:
 202                                 $levelName = 'Strict Standards';
 203                                 break;
 204                         case E_DEPRECATED:
 205                         case E_USER_DEPRECATED:
 206                                 $levelName = 'Deprecated';
 207                                 break;
 208                         case /* HHVM's FATAL_ERROR */ 16777217:
 209                                 $levelName = 'Fatal';
 210                                 break;
 211                         default:
 212                                 $levelName = 'Unknown error';
 213                                 break;
 214                 }
 215
 216                 $e = new ErrorException( "PHP $levelName: $message", 0, $level, $file, $line );
 217                 self::logError( $e );
 218
 219                 // This handler is for logging only. Return false will instruct PHP
 220                 // to continue regular handling.
 221                 return false;
 222         }
 223
 224
 225         /**
 226          * Look for a fatal error as the cause of the request termination and log
 227          * as an exception.
 228          *
 229          * Special handling is included for missing class errors as they may
 230          * indicate that the user needs to install 3rd-party libraries via
 231          * Composer or other means.
 232          *
 233          * @since 1.25
 234          */
 235         public static function handleFatalError() {
 236                 self::$reservedMemory = null;
 237                 $lastError = error_get_last();
 238
 239                 if ( $lastError &&
 240                         isset( $lastError['type'] ) &&
 241                         in_array( $lastError['type'], self::$fatalErrorTypes )
 242                 ) {
 243                         $msg = "Fatal Error: {$lastError['message']}";
 244                         // HHVM: Class undefined: foo
 245                         // PHP5: Class 'foo' not found
 246                         if ( preg_match( "/Class (undefined: \w+|'\w+' not found)/",
 247                                 $lastError['message']
 248                         ) ) {
 249                                 $msg = <<<TXT
 250 {$msg}
 251
 252 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.
 253
 254 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.
 255 TXT;
 256                         }
 257                         $e = new ErrorException( $msg, 0, $lastError['type'] );
 258                         self::logError( $e );
 259                 }
 260         }
 261
 262         /**
 263          * Generate a string representation of an exception's stack trace
 264          *
 265          * Like Exception::getTraceAsString, but replaces argument values with
 266          * argument type or class name.
 267          *
 268          * @param Exception $e
 269          * @return string
 270          */
 271         public static function getRedactedTraceAsString( Exception $e ) {
 272                 $text = '';
 273
 274                 foreach ( self::getRedactedTrace( $e ) as $level => $frame ) {
 275                         if ( isset( $frame['file'] ) && isset( $frame['line'] ) ) {
 276                                 $text .= "#{$level} {$frame['file']}({$frame['line']}): ";
 277                         } else {
 278                                 // 'file' and 'line' are unset for calls via call_user_func (bug 55634)
 279                                 // This matches behaviour of Exception::getTraceAsString to instead
 280                                 // display "[internal function]".
 281                                 $text .= "#{$level} [internal function]: ";
 282                         }
 283
 284                         if ( isset( $frame['class'] ) ) {
 285                                 $text .= $frame['class'] . $frame['type'] . $frame['function'];
 286                         } else {
 287                                 $text .= $frame['function'];
 288                         }
 289
 290                         if ( isset( $frame['args'] ) ) {
 291                                 $text .= '(' . implode( ', ', $frame['args'] ) . ")\n";
 292                         } else {
 293                                 $text .= "()\n";
 294                         }
 295                 }
 296
 297                 $level = $level + 1;
 298                 $text .= "#{$level} {main}";
 299
 300                 return $text;
 301         }
 302
 303         /**
 304          * Return a copy of an exception's backtrace as an array.
 305          *
 306          * Like Exception::getTrace, but replaces each element in each frame's
 307          * argument array with the name of its class (if the element is an object)
 308          * or its type (if the element is a PHP primitive).
 309          *
 310          * @since 1.22
 311          * @param Exception $e
 312          * @return array
 313          */
 314         public static function getRedactedTrace( Exception $e ) {
 315                 return array_map( function ( $frame ) {
 316                         if ( isset( $frame['args'] ) ) {
 317                                 $frame['args'] = array_map( function ( $arg ) {
 318                                         return is_object( $arg ) ? get_class( $arg ) : gettype( $arg );
 319                                 }, $frame['args'] );
 320                         }
 321                         return $frame;
 322                 }, $e->getTrace() );
 323         }
 324
 325         /**
 326          * Get the ID for this exception.
 327          *
 328          * The ID is saved so that one can match the one output to the user (when
 329          * $wgShowExceptionDetails is set to false), to the entry in the debug log.
 330          *
 331          * @since 1.22
 332          * @param Exception $e
 333          * @return string
 334          */
 335         public static function getLogId( Exception $e ) {
 336                 if ( !isset( $e->_mwLogId ) ) {
 337                         $e->_mwLogId = wfRandomString( 8 );
 338                 }
 339                 return $e->_mwLogId;
 340         }
 341
 342         /**
 343          * If the exception occurred in the course of responding to a request,
 344          * returns the requested URL. Otherwise, returns false.
 345          *
 346          * @since 1.23
 347          * @return string|bool
 348          */
 349         public static function getURL() {
 350                 global $wgRequest;
 351                 if ( !isset( $wgRequest ) || $wgRequest instanceof FauxRequest ) {
 352                         return false;
 353                 }
 354                 return $wgRequest->getRequestURL();
 355         }
 356
 357         /**
 358          * Get a message formatting the exception message and its origin.
 359          *
 360          * @since 1.22
 361          * @param Exception $e
 362          * @return string
 363          */
 364         public static function getLogMessage( Exception $e ) {
 365                 $id = self::getLogId( $e );
 366                 $type = get_class( $e );
 367                 $file = $e->getFile();
 368                 $line = $e->getLine();
 369                 $message = $e->getMessage();
 370                 $url = self::getURL() ?: '[no req]';
 371
 372                 return "[$id] $url   $type from line $line of $file: $message";
 373         }
 374
 375         /**
 376          * Serialize an Exception object to JSON.
 377          *
 378          * The JSON object will have keys 'id', 'file', 'line', 'message', and
 379          * 'url'. These keys map to string values, with the exception of 'line',
 380          * which is a number, and 'url', which may be either a string URL or or
 381          * null if the exception did not occur in the context of serving a web
 382          * request.
 383          *
 384          * If $wgLogExceptionBacktrace is true, it will also have a 'backtrace'
 385          * key, mapped to the array return value of Exception::getTrace, but with
 386          * each element in each frame's "args" array (if set) replaced with the
 387          * argument's class name (if the argument is an object) or type name (if
 388          * the argument is a PHP primitive).
 389          *
 390          * @par Sample JSON record ($wgLogExceptionBacktrace = false):
 391          * @code
 392          *  {
 393          *    "id": "c41fb419",
 394          *    "type": "MWException",
 395          *    "file": "/var/www/mediawiki/includes/cache/MessageCache.php",
 396          *    "line": 704,
 397          *    "message": "Non-string key given",
 398          *    "url": "/wiki/Main_Page"
 399          *  }
 400          * @endcode
 401          *
 402          * @par Sample JSON record ($wgLogExceptionBacktrace = true):
 403          * @code
 404          *  {
 405          *    "id": "dc457938",
 406          *    "type": "MWException",
 407          *    "file": "/vagrant/mediawiki/includes/cache/MessageCache.php",
 408          *    "line": 704,
 409          *    "message": "Non-string key given",
 410          *    "url": "/wiki/Main_Page",
 411          *    "backtrace": [{
 412          *      "file": "/vagrant/mediawiki/extensions/VisualEditor/VisualEditor.hooks.php",
 413          *      "line": 80,
 414          *      "function": "get",
 415          *      "class": "MessageCache",
 416          *      "type": "->",
 417          *      "args": ["array"]
 418          *    }]
 419          *  }
 420          * @endcode
 421          *
 422          * @since 1.23
 423          * @param Exception $e
 424          * @param bool $pretty Add non-significant whitespace to improve readability (default: false).
 425          * @param int $escaping Bitfield consisting of FormatJson::.*_OK class constants.
 426          * @return string|bool JSON string if successful; false upon failure
 427          */
 428         public static function jsonSerializeException( Exception $e, $pretty = false, $escaping = 0 ) {
 429                 global $wgLogExceptionBacktrace;
 430
 431                 $exceptionData = array(
 432                         'id' => self::getLogId( $e ),
 433                         'type' => get_class( $e ),
 434                         'file' => $e->getFile(),
 435                         'line' => $e->getLine(),
 436                         'message' => $e->getMessage(),
 437                 );
 438
 439                 if ( $e instanceof ErrorException && ( error_reporting() & $e->getSeverity() ) === 0 ) {
 440                         // Flag surpressed errors
 441                         $exceptionData['suppressed'] = true;
 442                 }
 443
 444                 // Because MediaWiki is first and foremost a web application, we set a
 445                 // 'url' key unconditionally, but set it to null if the exception does
 446                 // not occur in the context of a web request, as a way of making that
 447                 // fact visible and explicit.
 448                 $exceptionData['url'] = self::getURL() ?: null;
 449
 450                 if ( $wgLogExceptionBacktrace ) {
 451                         // Argument values may not be serializable, so redact them.
 452                         $exceptionData['backtrace'] = self::getRedactedTrace( $e );
 453                 }
 454
 455                 return FormatJson::encode( $exceptionData, $pretty, $escaping );
 456         }
 457
 458         /**
 459          * Log an exception to the exception log (if enabled).
 460          *
 461          * This method must not assume the exception is an MWException,
 462          * it is also used to handle PHP exceptions or exceptions from other libraries.
 463          *
 464          * @since 1.22
 465          * @param Exception $e
 466          */
 467         public static function logException( Exception $e ) {
 468                 global $wgLogExceptionBacktrace;
 469
 470                 if ( !( $e instanceof MWException ) || $e->isLoggable() ) {
 471                         $log = self::getLogMessage( $e );
 472                         if ( $wgLogExceptionBacktrace ) {
 473                                 wfDebugLog( 'exception', $log . "\n" . $e->getTraceAsString() );
 474                         } else {
 475                                 wfDebugLog( 'exception', $log );
 476                         }
 477
 478                         $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 479                         if ( $json !== false ) {
 480                                 wfDebugLog( 'exception-json', $json, 'private' );
 481                         }
 482                 }
 483         }
 484
 485         /**
 486          * Log an exception that wasn't thrown but made to wrap an error.
 487          *
 488          * @since 1.25
 489          * @param ErrorException $e
 490         */
 491         protected static function logError( ErrorException $e ) {
 492                 global $wgLogExceptionBacktrace;
 493
 494                 // The set_error_handler callback is independent from error_reporting.
 495                 // Filter out unwanted errors manually (e.g. when wfSuppressWarnings is active).
 496                 if ( ( error_reporting() & $e->getSeverity() ) !== 0 ) {
 497                         $log = self::getLogMessage( $e );
 498                         if ( $wgLogExceptionBacktrace ) {
 499                                 wfDebugLog( 'error', $log . "\n" . $e->getTraceAsString() );
 500                         } else {
 501                                 wfDebugLog( 'error', $log );
 502                         }
 503                 }
 504
 505                 // Include all errors in the json log (surpressed errors will be flagged)
 506                 $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 507                 if ( $json !== false ) {
 508                         wfDebugLog( 'error-json', $json, 'private' );
 509                 }
 510         }
 511 }