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                 $e = new ErrorException( $message, 0, $level, $file, $line );
 171                 self::logError( $e );
 172
 173                 // This handler is for logging only. Return false will instruct PHP
 174                 // to continue regular handling.
 175                 return false;
 176         }
 177
 178         /**
 179          * Generate a string representation of an exception's stack trace
 180          *
 181          * Like Exception::getTraceAsString, but replaces argument values with
 182          * argument type or class name.
 183          *
 184          * @param Exception $e
 185          * @return string
 186          */
 187         public static function getRedactedTraceAsString( Exception $e ) {
 188                 $text = '';
 189
 190                 foreach ( self::getRedactedTrace( $e ) as $level => $frame ) {
 191                         if ( isset( $frame['file'] ) && isset( $frame['line'] ) ) {
 192                                 $text .= "#{$level} {$frame['file']}({$frame['line']}): ";
 193                         } else {
 194                                 // 'file' and 'line' are unset for calls via call_user_func (bug 55634)
 195                                 // This matches behaviour of Exception::getTraceAsString to instead
 196                                 // display "[internal function]".
 197                                 $text .= "#{$level} [internal function]: ";
 198                         }
 199
 200                         if ( isset( $frame['class'] ) ) {
 201                                 $text .= $frame['class'] . $frame['type'] . $frame['function'];
 202                         } else {
 203                                 $text .= $frame['function'];
 204                         }
 205
 206                         if ( isset( $frame['args'] ) ) {
 207                                 $text .= '(' . implode( ', ', $frame['args'] ) . ")\n";
 208                         } else {
 209                                 $text .= "()\n";
 210                         }
 211                 }
 212
 213                 $level = $level + 1;
 214                 $text .= "#{$level} {main}";
 215
 216                 return $text;
 217         }
 218
 219         /**
 220          * Return a copy of an exception's backtrace as an array.
 221          *
 222          * Like Exception::getTrace, but replaces each element in each frame's
 223          * argument array with the name of its class (if the element is an object)
 224          * or its type (if the element is a PHP primitive).
 225          *
 226          * @since 1.22
 227          * @param Exception $e
 228          * @return array
 229          */
 230         public static function getRedactedTrace( Exception $e ) {
 231                 return array_map( function ( $frame ) {
 232                         if ( isset( $frame['args'] ) ) {
 233                                 $frame['args'] = array_map( function ( $arg ) {
 234                                         return is_object( $arg ) ? get_class( $arg ) : gettype( $arg );
 235                                 }, $frame['args'] );
 236                         }
 237                         return $frame;
 238                 }, $e->getTrace() );
 239         }
 240
 241         /**
 242          * Get the ID for this exception.
 243          *
 244          * The ID is saved so that one can match the one output to the user (when
 245          * $wgShowExceptionDetails is set to false), to the entry in the debug log.
 246          *
 247          * @since 1.22
 248          * @param Exception $e
 249          * @return string
 250          */
 251         public static function getLogId( Exception $e ) {
 252                 if ( !isset( $e->_mwLogId ) ) {
 253                         $e->_mwLogId = wfRandomString( 8 );
 254                 }
 255                 return $e->_mwLogId;
 256         }
 257
 258         /**
 259          * If the exception occurred in the course of responding to a request,
 260          * returns the requested URL. Otherwise, returns false.
 261          *
 262          * @since 1.23
 263          * @return string|bool
 264          */
 265         public static function getURL() {
 266                 global $wgRequest;
 267                 if ( !isset( $wgRequest ) || $wgRequest instanceof FauxRequest ) {
 268                         return false;
 269                 }
 270                 return $wgRequest->getRequestURL();
 271         }
 272
 273         /**
 274          * Get a message formatting the exception message and its origin.
 275          *
 276          * @since 1.22
 277          * @param Exception $e
 278          * @return string
 279          */
 280         public static function getLogMessage( Exception $e ) {
 281                 $id = self::getLogId( $e );
 282                 $type = get_class( $e );
 283                 $file = $e->getFile();
 284                 $line = $e->getLine();
 285                 $message = $e->getMessage();
 286                 $url = self::getURL() ?: '[no req]';
 287
 288                 return "[$id] $url   $type from line $line of $file: $message";
 289         }
 290
 291         /**
 292          * Serialize an Exception object to JSON.
 293          *
 294          * The JSON object will have keys 'id', 'file', 'line', 'message', and
 295          * 'url'. These keys map to string values, with the exception of 'line',
 296          * which is a number, and 'url', which may be either a string URL or or
 297          * null if the exception did not occur in the context of serving a web
 298          * request.
 299          *
 300          * If $wgLogExceptionBacktrace is true, it will also have a 'backtrace'
 301          * key, mapped to the array return value of Exception::getTrace, but with
 302          * each element in each frame's "args" array (if set) replaced with the
 303          * argument's class name (if the argument is an object) or type name (if
 304          * the argument is a PHP primitive).
 305          *
 306          * @par Sample JSON record ($wgLogExceptionBacktrace = false):
 307          * @code
 308          *  {
 309          *    "id": "c41fb419",
 310          *    "type": "MWException",
 311          *    "file": "/var/www/mediawiki/includes/cache/MessageCache.php",
 312          *    "line": 704,
 313          *    "message": "Non-string key given",
 314          *    "url": "/wiki/Main_Page"
 315          *  }
 316          * @endcode
 317          *
 318          * @par Sample JSON record ($wgLogExceptionBacktrace = true):
 319          * @code
 320          *  {
 321          *    "id": "dc457938",
 322          *    "type": "MWException",
 323          *    "file": "/vagrant/mediawiki/includes/cache/MessageCache.php",
 324          *    "line": 704,
 325          *    "message": "Non-string key given",
 326          *    "url": "/wiki/Main_Page",
 327          *    "backtrace": [{
 328          *      "file": "/vagrant/mediawiki/extensions/VisualEditor/VisualEditor.hooks.php",
 329          *      "line": 80,
 330          *      "function": "get",
 331          *      "class": "MessageCache",
 332          *      "type": "->",
 333          *      "args": ["array"]
 334          *    }]
 335          *  }
 336          * @endcode
 337          *
 338          * @since 1.23
 339          * @param Exception $e
 340          * @param bool $pretty Add non-significant whitespace to improve readability (default: false).
 341          * @param int $escaping Bitfield consisting of FormatJson::.*_OK class constants.
 342          * @return string|bool JSON string if successful; false upon failure
 343          */
 344         public static function jsonSerializeException( Exception $e, $pretty = false, $escaping = 0 ) {
 345                 global $wgLogExceptionBacktrace;
 346
 347                 $exceptionData = array(
 348                         'id' => self::getLogId( $e ),
 349                         'type' => get_class( $e ),
 350                         'file' => $e->getFile(),
 351                         'line' => $e->getLine(),
 352                         'message' => $e->getMessage(),
 353                 );
 354
 355                 // Because MediaWiki is first and foremost a web application, we set a
 356                 // 'url' key unconditionally, but set it to null if the exception does
 357                 // not occur in the context of a web request, as a way of making that
 358                 // fact visible and explicit.
 359                 $exceptionData['url'] = self::getURL() ?: null;
 360
 361                 if ( $wgLogExceptionBacktrace ) {
 362                         // Argument values may not be serializable, so redact them.
 363                         $exceptionData['backtrace'] = self::getRedactedTrace( $e );
 364                 }
 365
 366                 return FormatJson::encode( $exceptionData, $pretty, $escaping );
 367         }
 368
 369         /**
 370          * Log an exception to the exception log (if enabled).
 371          *
 372          * This method must not assume the exception is an MWException,
 373          * it is also used to handle PHP exceptions or exceptions from other libraries.
 374          *
 375          * @since 1.22
 376          * @param Exception $e
 377          */
 378         public static function logException( Exception $e ) {
 379                 global $wgLogExceptionBacktrace;
 380
 381                 if ( !( $e instanceof MWException ) || $e->isLoggable() ) {
 382                         $log = self::getLogMessage( $e );
 383                         if ( $wgLogExceptionBacktrace ) {
 384                                 wfDebugLog( 'exception', $log . "\n" . $e->getTraceAsString() );
 385                         } else {
 386                                 wfDebugLog( 'exception', $log );
 387                         }
 388
 389                         $json = self::jsonSerializeException( $e, false, FormatJson::ALL_OK );
 390                         if ( $json !== false ) {
 391                                 wfDebugLog( 'exception-json', $json, 'private' );
 392                         }
 393                 }
 394         }
 395
 396         /**
 397          * Log an exception that wasn't thrown but made to wrap an error.
 398          *
 399          * @since 1.25
 400          * @param Exception $e
 401         */
 402         protected static function logError( Exception $e ) {
 403                 global $wgLogExceptionBacktrace;
 404
 405                 $log = self::getLogMessage( $e );
 406                 if ( $wgLogExceptionBacktrace ) {
 407                         wfDebugLog( 'error', $log . "\n" . $e->getTraceAsString() );
 408                 } else {
 409                         wfDebugLog( 'error', $log );
 410                 }
 411         }
 412 }