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