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