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