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                 $channel = 'error';
 183                 switch ( $level ) {
 184                         case E_ERROR:
 185                         case E_CORE_ERROR:
 186                         case E_COMPILE_ERROR:
 187                         case E_USER_ERROR:
 188                         case E_RECOVERABLE_ERROR:
 189                         case E_PARSE:
 190                                 $levelName = 'Error';
 191                                 $channel = 'fatal';
 192                                 break;
 193                         case E_WARNING:
 194                         case E_CORE_WARNING:
 195                         case E_COMPILE_WARNING:
 196                         case E_USER_WARNING:
 197                                 $levelName = 'Warning';
 198                                 break;
 199                         case E_NOTICE:
 200                         case E_USER_NOTICE:
 201                                 $levelName = 'Notice';
 202                                 break;
 203                         case E_STRICT:
 204                                 $levelName = 'Strict Standards';
 205                                 break;
 206                         case E_DEPRECATED:
 207                         case E_USER_DEPRECATED:
 208                                 $levelName = 'Deprecated';
 209                                 break;
 210                         case /* HHVM's FATAL_ERROR */ 16777217:
 211                                 $levelName = 'Fatal';
 212                                 $channel = 'fatal';
 213                                 break;
 214                         default:
 215                                 $levelName = 'Unknown error';
 216                                 break;
 217                 }
 218
 219                 $e = new ErrorException( "PHP $levelName: $message", 0, $level, $file, $line );
 220                 self::logError( $e, $channel );
 221
 222                 // This handler is for logging only. Return false will instruct PHP
 223                 // to continue regular handling.
 224                 return false;
 225         }
 226
 227
 228         /**
 229          * Look for a fatal error as the cause of the request termination and log
 230          * as an exception.
 231          *
 232          * Special handling is included for missing class errors as they may
 233          * indicate that the user needs to install 3rd-party libraries via
 234          * Composer or other means.
 235          *
 236          * @since 1.25
 237          */
 238         public static function handleFatalError() {
 239                 self::$reservedMemory = null;
 240                 $lastError = error_get_last();
 241
 242                 if ( $lastError &&
 243                         isset( $lastError['type'] ) &&
 244                         in_array( $lastError['type'], self::$fatalErrorTypes )
 245                 ) {
 246                         $msg = "Fatal Error: {$lastError['message']}";
 247                         // HHVM: Class undefined: foo
 248                         // PHP5: Class 'foo' not found
 249                         if ( preg_match( "/Class (undefined: \w+|'\w+' not found)/",
 250                                 $lastError['message']
 251                         ) ) {
 252                                 // @codingStandardsIgnoreStart Generic.Files.LineLength.TooLong
 253                                 $msg = <<<TXT
 254 {$msg}
 255
 256 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.
 257
 258 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.
 259 TXT;
 260                                 // @codingStandardsIgnoreEnd
 261                         }
 262                         $e = new ErrorException( $msg, 0, $lastError['type'] );
 263                         self::logError( $e, 'fatal' );
 264                 }
 265         }
 266
 267         /**
 268          * Generate a string representation of an exception's stack trace
 269          *
 270          * Like Exception::getTraceAsString, but replaces argument values with
 271          * argument type or class name.
 272          *
 273          * @param Exception $e
 274          * @return string
 275          */
 276         public static function getRedactedTraceAsString( Exception $e ) {
 277                 $text = '';
 278
 279                 foreach ( self::getRedactedTrace( $e ) as $level => $frame ) {
 280                         if ( isset( $frame['file'] ) && isset( $frame['line'] ) ) {
 281                                 $text .= "#{$level} {$frame['file']}({$frame['line']}): ";
 282                         } else {
 283                                 // 'file' and 'line' are unset for calls via call_user_func (bug 55634)
 284                                 // This matches behaviour of Exception::getTraceAsString to instead
 285                                 // display "[internal function]".
 286                                 $text .= "#{$level} [internal function]: ";
 287                         }
 288
 289                         if ( isset( $frame['class'] ) ) {
 290                                 $text .= $frame['class'] . $frame['type'] . $frame['function'];
 291                         } else {
 292                                 $text .= $frame['function'];
 293                         }
 294
 295                         if ( isset( $frame['args'] ) ) {
 296                                 $text .= '(' . implode( ', ', $frame['args'] ) . ")\n";
 297                         } else {
 298                                 $text .= "()\n";
 299                         }
 300                 }
 301
 302                 $level = $level + 1;
 303                 $text .= "#{$level} {main}";
 304
 305                 return $text;
 306         }
 307
 308         /**
 309          * Return a copy of an exception's backtrace as an array.
 310          *
 311          * Like Exception::getTrace, but replaces each element in each frame's
 312          * argument array with the name of its class (if the element is an object)
 313          * or its type (if the element is a PHP primitive).
 314          *
 315          * @since 1.22
 316          * @param Exception $e
 317          * @return array
 318          */
 319         public static function getRedactedTrace( Exception $e ) {
 320                 return array_map( function ( $frame ) {
 321                         if ( isset( $frame['args'] ) ) {
 322                                 $frame['args'] = array_map( function ( $arg ) {
 323                                         return is_object( $arg ) ? get_class( $arg ) : gettype( $arg );
 324                                 }, $frame['args'] );
 325                         }
 326                         return $frame;
 327                 }, $e->getTrace() );
 328         }
 329
 330         /**
 331          * Get the ID for this exception.
 332          *
 333          * The ID is saved so that one can match the one output to the user (when
 334          * $wgShowExceptionDetails is set to false), to the entry in the debug log.
 335          *
 336          * @since 1.22
 337          * @param Exception $e
 338          * @return string
 339          */
 340         public static function getLogId( Exception $e ) {
 341                 if ( !isset( $e->_mwLogId ) ) {
 342                         $e->_mwLogId = wfRandomString( 8 );
 343                 }
 344                 return $e->_mwLogId;
 345         }
 346
 347         /**
 348          * If the exception occurred in the course of responding to a request,
 349          * returns the requested URL. Otherwise, returns false.
 350          *
 351          * @since 1.23
 352          * @return string|false
 353          */
 354         public static function getURL() {
 355                 global $wgRequest;
 356                 if ( !isset( $wgRequest ) || $wgRequest instanceof FauxRequest ) {
 357                         return false;
 358                 }
 359                 return $wgRequest->getRequestURL();
 360         }
 361
 362         /**
 363          * Get a message formatting the exception message and its origin.
 364          *
 365          * @since 1.22
 366          * @param Exception $e
 367          * @return string
 368          */
 369         public static function getLogMessage( Exception $e ) {
 370                 $id = self::getLogId( $e );
 371                 $type = get_class( $e );
 372                 $file = $e->getFile();
 373                 $line = $e->getLine();
 374                 $message = $e->getMessage();
 375                 $url = self::getURL() ?: '[no req]';
 376
 377                 return "[$id] $url   $type from line $line of $file: $message";
 378         }
 379
 380         /**
 381          * Serialize an Exception object to JSON.
 382          *
 383          * The JSON object will have keys 'id', 'file', 'line', 'message', and
 384          * 'url'. These keys map to string values, with the exception of 'line',
 385          * which is a number, and 'url', which may be either a string URL or or
 386          * null if the exception did not occur in the context of serving a web
 387          * request.
 388          *
 389          * If $wgLogExceptionBacktrace is true, it will also have a 'backtrace'
 390          * key, mapped to the array return value of Exception::getTrace, but with
 391          * each element in each frame's "args" array (if set) replaced with the
 392          * argument's class name (if the argument is an object) or type name (if
 393          * the argument is a PHP primitive).
 394          *
 395          * @par Sample JSON record ($wgLogExceptionBacktrace = false):
 396          * @code
 397          *  {
 398          *    "id": "c41fb419",
 399          *    "type": "MWException",
 400          *    "file": "/var/www/mediawiki/includes/cache/MessageCache.php",
 401          *    "line": 704,
 402          *    "message": "Non-string key given",
 403          *    "url": "/wiki/Main_Page"
 404          *  }
 405          * @endcode
 406          *
 407          * @par Sample JSON record ($wgLogExceptionBacktrace = true):
 408          * @code
 409          *  {
 410          *    "id": "dc457938",
 411          *    "type": "MWException",
 412          *    "file": "/vagrant/mediawiki/includes/cache/MessageCache.php",
 413          *    "line": 704,
 414          *    "message": "Non-string key given",
 415          *    "url": "/wiki/Main_Page",
 416          *    "backtrace": [{
 417          *      "file": "/vagrant/mediawiki/extensions/VisualEditor/VisualEditor.hooks.php",
 418          *      "line": 80,
 419          *      "function": "get",
 420          *      "class": "MessageCache",
 421          *      "type": "->",
 422          *      "args": ["array"]
 423          *    }]
 424          *  }
 425          * @endcode
 426          *
 427          * @since 1.23
 428          * @param Exception $e
 429          * @param bool $pretty Add non-significant whitespace to improve readability (default: false).
 430          * @param int $escaping Bitfield consisting of FormatJson::.*_OK class constants.
 431          * @return string|false JSON string if successful; false upon failure
 432          */
 433         public static function jsonSerializeException( Exception $e, $pretty = false, $escaping = 0 ) {
 434                 global $wgLogExceptionBacktrace;
 435
 436                 $exceptionData = array(
 437                         'id' => self::getLogId( $e ),
 438                         'type' => get_class( $e ),
 439                         'file' => $e->getFile(),
 440                         'line' => $e->getLine(),
 441                         'message' => $e->getMessage(),
 442                 );
 443
 444                 if ( $e instanceof ErrorException && ( error_reporting() & $e->getSeverity() ) === 0 ) {
 445                         // Flag surpressed errors
 446                         $exceptionData['suppressed'] = true;
 447                 }
 448
 449                 // Because MediaWiki is first and foremost a web application, we set a
 450                 // 'url' key unconditionally, but set it to null if the exception does
 451                 // not occur in the context of a web request, as a way of making that
 452                 // fact visible and explicit.
 453                 $exceptionData['url'] = self::getURL() ?: null;
 454
 455                 if ( $wgLogExceptionBacktrace ) {
 456                         // Argument values may not be serializable, so redact them.
 457                         $exceptionData['backtrace'] = self::getRedactedTrace( $e );
 458                 }
 459
 460                 return FormatJson::encode( $exceptionData, $pretty, $escaping );
 461         }
 462
 463         /**
 464          * Log an exception to the exception log (if enabled).
 465          *
 466          * This method must not assume the exception is an MWException,
 467          * it is also used to handle PHP exceptions or exceptions from other libraries.
 468          *
 469          * @since 1.22
 470          * @param Exception $e
 471          */
 472         public static function logException( Exception $e ) {
 473                 global $wgLogExceptionBacktrace;
 474
 475                 if ( !( $e instanceof MWException ) || $e->isLoggable() ) {
 476                         $log = self::getLogMessage( $e );
 477                         if ( $wgLogExceptionBacktrace ) {
 478                                 wfDebugLog( 'exception', $log . "\n" . $e->getTraceAsString() );
 479                         } else {
 480                                 wfDebugLog( 'exception', $log );
 481                         }
 482
 483                         $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 484                         if ( $json !== false ) {
 485                                 wfDebugLog( 'exception-json', $json, 'private' );
 486                         }
 487                 }
 488         }
 489
 490         /**
 491          * Log an exception that wasn't thrown but made to wrap an error.
 492          *
 493          * @since 1.25
 494          * @param ErrorException $e
 495          * @param string $channel
 496         */
 497         protected static function logError( ErrorException $e, $channel ) {
 498                 global $wgLogExceptionBacktrace;
 499
 500                 // The set_error_handler callback is independent from error_reporting.
 501                 // Filter out unwanted errors manually (e.g. when wfSuppressWarnings is active).
 502                 if ( ( error_reporting() & $e->getSeverity() ) !== 0 ) {
 503                         $log = self::getLogMessage( $e );
 504                         if ( $wgLogExceptionBacktrace ) {
 505                                 wfDebugLog( $channel, $log . "\n" . $e->getTraceAsString() );
 506                         } else {
 507                                 wfDebugLog( $channel, $log );
 508                         }
 509                 }
 510
 511                 // Include all errors in the json log (surpressed errors will be flagged)
 512                 $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 513                 if ( $json !== false ) {
 514                         wfDebugLog( "$channel-json", $json, 'private' );
 515                 }
 516         }
 517 }