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