includes/shell/Command.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 namespace MediaWiki\Shell;
  22
  23 use Exception;
  24 use MediaWiki\ProcOpenError;
  25 use MediaWiki\ShellDisabledError;
  26 use Profiler;
  27 use Psr\Log\LoggerAwareTrait;
  28 use Psr\Log\NullLogger;
  29
  30 /**
  31  * Class used for executing shell commands
  32  *
  33  * @since 1.30
  34  */
  35 class Command {
  36         use LoggerAwareTrait;
  37
  38         /** @var string */
  39         private $command = '';
  40
  41         /** @var array */
  42         private $limits = [
  43                 // seconds
  44                 'time' => 180,
  45                 // seconds
  46                 'walltime' => 180,
  47                 // KB
  48                 'memory' => 307200,
  49                 // KB
  50                 'filesize' => 102400,
  51         ];
  52
  53         /** @var string[] */
  54         private $env = [];
  55
  56         /** @var string */
  57         private $method;
  58
  59         /** @var bool */
  60         private $doIncludeStderr = false;
  61
  62         /** @var bool */
  63         private $doLogStderr = false;
  64
  65         /** @var bool */
  66         private $everExecuted = false;
  67
  68         /** @var string|false */
  69         private $cgroup = false;
  70
  71         /**
  72          * bitfield with restrictions
  73          *
  74          * @var int
  75          */
  76         protected $restrictions = 0;
  77
  78         /**
  79          * Constructor. Don't call directly, instead use Shell::command()
  80          *
  81          * @throws ShellDisabledError
  82          */
  83         public function __construct() {
  84                 if ( Shell::isDisabled() ) {
  85                         throw new ShellDisabledError();
  86                 }
  87
  88                 $this->setLogger( new NullLogger() );
  89         }
  90
  91         /**
  92          * Destructor. Makes sure programmer didn't forget to execute the command after all
  93          */
  94         public function __destruct() {
  95                 if ( !$this->everExecuted ) {
  96                         $context = [ 'command' => $this->command ];
  97                         $message = __CLASS__ . " was instantiated, but execute() was never called.";
  98                         if ( $this->method ) {
  99                                 $message .= ' Calling method: {method}.';
 100                                 $context['method'] = $this->method;
 101                         }
 102                         $message .= ' Command: {command}';
 103                         $this->logger->warning( $message, $context );
 104                 }
 105         }
 106
 107         /**
 108          * Adds parameters to the command. All parameters are sanitized via Shell::escape().
 109          *
 110          * @param string|string[] $args,...
 111          * @return $this
 112          */
 113         public function params( /* ... */ ) {
 114                 $args = func_get_args();
 115                 if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
 116                         // If only one argument has been passed, and that argument is an array,
 117                         // treat it as a list of arguments
 118                         $args = reset( $args );
 119                 }
 120                 $this->command .= ' ' . Shell::escape( $args );
 121
 122                 return $this;
 123         }
 124
 125         /**
 126          * Adds unsafe parameters to the command. These parameters are NOT sanitized in any way.
 127          *
 128          * @param string|string[] $args,...
 129          * @return $this
 130          */
 131         public function unsafeParams( /* ... */ ) {
 132                 $args = func_get_args();
 133                 if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
 134                         // If only one argument has been passed, and that argument is an array,
 135                         // treat it as a list of arguments
 136                         $args = reset( $args );
 137                 }
 138                 $this->command .= implode( ' ', $args );
 139
 140                 return $this;
 141         }
 142
 143         /**
 144          * Sets execution limits
 145          *
 146          * @param array $limits Associative array of limits. Keys (all optional):
 147          *   filesize (for ulimit -f), memory, time, walltime.
 148          * @return $this
 149          */
 150         public function limits( array $limits ) {
 151                 if ( !isset( $limits['walltime'] ) && isset( $limits['time'] ) ) {
 152                         // Emulate the behavior of old wfShellExec() where walltime fell back on time
 153                         // if the latter was overridden and the former wasn't
 154                         $limits['walltime'] = $limits['time'];
 155                 }
 156                 $this->limits = $limits + $this->limits;
 157
 158                 return $this;
 159         }
 160
 161         /**
 162          * Sets environment variables which should be added to the executed command environment
 163          *
 164          * @param string[] $env array of variable name => value
 165          * @return $this
 166          */
 167         public function environment( array $env ) {
 168                 $this->env = $env;
 169
 170                 return $this;
 171         }
 172
 173         /**
 174          * Sets calling function for profiler. By default, the caller for execute() will be used.
 175          *
 176          * @param string $method
 177          * @return $this
 178          */
 179         public function profileMethod( $method ) {
 180                 $this->method = $method;
 181
 182                 return $this;
 183         }
 184
 185         /**
 186          * Controls whether stderr should be included in stdout, including errors from limit.sh.
 187          * Default: don't include.
 188          *
 189          * @param bool $yesno
 190          * @return $this
 191          */
 192         public function includeStderr( $yesno = true ) {
 193                 $this->doIncludeStderr = $yesno;
 194
 195                 return $this;
 196         }
 197
 198         /**
 199          * When enabled, text sent to stderr will be logged with a level of 'error'.
 200          *
 201          * @param bool $yesno
 202          * @return $this
 203          */
 204         public function logStderr( $yesno = true ) {
 205                 $this->doLogStderr = $yesno;
 206
 207                 return $this;
 208         }
 209
 210         /**
 211          * Sets cgroup for this command
 212          *
 213          * @param string|false $cgroup Absolute file path to the cgroup, or false to not use a cgroup
 214          * @return $this
 215          */
 216         public function cgroup( $cgroup ) {
 217                 $this->cgroup = $cgroup;
 218
 219                 return $this;
 220         }
 221
 222         /**
 223          * Set additional restrictions for this request
 224          *
 225          * @since 1.31
 226          * @param int $restrictions
 227          * @return $this
 228          */
 229         public function restrict( $restrictions ) {
 230                 $this->restrictions |= $restrictions;
 231
 232                 return $this;
 233         }
 234
 235         /**
 236          * Bitfield helper on whether a specific restriction is enabled
 237          *
 238          * @param int $restriction
 239          *
 240          * @return bool
 241          */
 242         protected function hasRestriction( $restriction ) {
 243                 return ( $this->restrictions & $restriction ) === $restriction;
 244         }
 245
 246         /**
 247          * If called, only the files/directories that are
 248          * whitelisted will be available to the shell command.
 249          *
 250          * limit.sh will always be whitelisted
 251          *
 252          * @param string[] $paths
 253          *
 254          * @return $this
 255          */
 256         public function whitelistPaths( array $paths ) {
 257                 // Default implementation is a no-op
 258                 return $this;
 259         }
 260
 261         /**
 262          * String together all the options and build the final command
 263          * to execute
 264          *
 265          * @return array [ command, whether to use log pipe ]
 266          */
 267         protected function buildFinalCommand() {
 268                 $envcmd = '';
 269                 foreach ( $this->env as $k => $v ) {
 270                         if ( wfIsWindows() ) {
 271                                 /* Surrounding a set in quotes (method used by wfEscapeShellArg) makes the quotes themselves
 272                                  * appear in the environment variable, so we must use carat escaping as documented in
 273                                  * https://technet.microsoft.com/en-us/library/cc723564.aspx
 274                                  * Note however that the quote isn't listed there, but is needed, and the parentheses
 275                                  * are listed there but doesn't appear to need it.
 276                                  */
 277                                 $envcmd .= "set $k=" . preg_replace( '/([&|()<>^"])/', '^\\1', $v ) . '&& ';
 278                         } else {
 279                                 /* Assume this is a POSIX shell, thus required to accept variable assignments before the command
 280                                  * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_01
 281                                  */
 282                                 $envcmd .= "$k=" . escapeshellarg( $v ) . ' ';
 283                         }
 284                 }
 285
 286                 $useLogPipe = false;
 287                 $cmd = $envcmd . trim( $this->command );
 288
 289                 if ( is_executable( '/bin/bash' ) ) {
 290                         $time = intval( $this->limits['time'] );
 291                         $wallTime = intval( $this->limits['walltime'] );
 292                         $mem = intval( $this->limits['memory'] );
 293                         $filesize = intval( $this->limits['filesize'] );
 294
 295                         if ( $time > 0 || $mem > 0 || $filesize > 0 || $wallTime > 0 ) {
 296                                 $cmd = '/bin/bash ' . escapeshellarg( __DIR__ . '/limit.sh' ) . ' ' .
 297                                         escapeshellarg( $cmd ) . ' ' .
 298                                         escapeshellarg(
 299                                                 "MW_INCLUDE_STDERR=" . ( $this->doIncludeStderr ? '1' : '' ) . ';' .
 300                                                 "MW_CPU_LIMIT=$time; " .
 301                                                 'MW_CGROUP=' . escapeshellarg( $this->cgroup ) . '; ' .
 302                                                 "MW_MEM_LIMIT=$mem; " .
 303                                                 "MW_FILE_SIZE_LIMIT=$filesize; " .
 304                                                 "MW_WALL_CLOCK_LIMIT=$wallTime; " .
 305                                                 "MW_USE_LOG_PIPE=yes"
 306                                         );
 307                                 $useLogPipe = true;
 308                         }
 309                 }
 310                 if ( !$useLogPipe && $this->doIncludeStderr ) {
 311                         $cmd .= ' 2>&1';
 312                 }
 313
 314                 return [ $cmd, $useLogPipe ];
 315         }
 316
 317         /**
 318          * Executes command. Afterwards, getExitCode() and getOutput() can be used to access execution
 319          * results.
 320          *
 321          * @return Result
 322          * @throws Exception
 323          * @throws ProcOpenError
 324          * @throws ShellDisabledError
 325          */
 326         public function execute() {
 327                 $this->everExecuted = true;
 328
 329                 $profileMethod = $this->method ?: wfGetCaller();
 330
 331                 list( $cmd, $useLogPipe ) = $this->buildFinalCommand();
 332
 333                 $this->logger->debug( __METHOD__ . ": $cmd" );
 334
 335                 // Don't try to execute commands that exceed Linux's MAX_ARG_STRLEN.
 336                 // Other platforms may be more accomodating, but we don't want to be
 337                 // accomodating, because very long commands probably include user
 338                 // input. See T129506.
 339                 if ( strlen( $cmd ) > SHELL_MAX_ARG_STRLEN ) {
 340                         throw new Exception( __METHOD__ .
 341                                 '(): total length of $cmd must not exceed SHELL_MAX_ARG_STRLEN' );
 342                 }
 343
 344                 $desc = [
 345                         0 => [ 'file', 'php://stdin', 'r' ],
 346                         1 => [ 'pipe', 'w' ],
 347                         2 => [ 'pipe', 'w' ],
 348                 ];
 349                 if ( $useLogPipe ) {
 350                         $desc[3] = [ 'pipe', 'w' ];
 351                 }
 352                 $pipes = null;
 353                 $scoped = Profiler::instance()->scopedProfileIn( __FUNCTION__ . '-' . $profileMethod );
 354                 $proc = proc_open( $cmd, $desc, $pipes );
 355                 if ( !$proc ) {
 356                         $this->logger->error( "proc_open() failed: {command}", [ 'command' => $cmd ] );
 357                         throw new ProcOpenError();
 358                 }
 359                 $outBuffer = $logBuffer = '';
 360                 $errBuffer = null;
 361                 $emptyArray = [];
 362                 $status = false;
 363                 $logMsg = false;
 364
 365                 /* According to the documentation, it is possible for stream_select()
 366                  * to fail due to EINTR. I haven't managed to induce this in testing
 367                  * despite sending various signals. If it did happen, the error
 368                  * message would take the form:
 369                  *
 370                  * stream_select(): unable to select [4]: Interrupted system call (max_fd=5)
 371                  *
 372                  * where [4] is the value of the macro EINTR and "Interrupted system
 373                  * call" is string which according to the Linux manual is "possibly"
 374                  * localised according to LC_MESSAGES.
 375                  */
 376                 $eintr = defined( 'SOCKET_EINTR' ) ? SOCKET_EINTR : 4;
 377                 $eintrMessage = "stream_select(): unable to select [$eintr]";
 378
 379                 $running = true;
 380                 $timeout = null;
 381                 $numReadyPipes = 0;
 382
 383                 while ( $running === true || $numReadyPipes !== 0 ) {
 384                         if ( $running ) {
 385                                 $status = proc_get_status( $proc );
 386                                 // If the process has terminated, switch to nonblocking selects
 387                                 // for getting any data still waiting to be read.
 388                                 if ( !$status['running'] ) {
 389                                         $running = false;
 390                                         $timeout = 0;
 391                                 }
 392                         }
 393
 394                         $readyPipes = $pipes;
 395
 396                         // clear get_last_error without actually raising an error
 397                         // from http://php.net/manual/en/function.error-get-last.php#113518
 398                         // TODO replace with clear_last_error when requirements are bumped to PHP7
 399                         set_error_handler( function () {
 400                         }, 0 );
 401                         // @codingStandardsIgnoreStart Generic.PHP.NoSilencedErrors.Discouraged
 402                         @trigger_error( '' );
 403                         // @codingStandardsIgnoreEnd
 404                         restore_error_handler();
 405
 406                         // @codingStandardsIgnoreStart Generic.PHP.NoSilencedErrors.Discouraged
 407                         $numReadyPipes = @stream_select( $readyPipes, $emptyArray, $emptyArray, $timeout );
 408                         // @codingStandardsIgnoreEnd
 409                         if ( $numReadyPipes === false ) {
 410                                 $error = error_get_last();
 411                                 if ( strncmp( $error['message'], $eintrMessage, strlen( $eintrMessage ) ) == 0 ) {
 412                                         continue;
 413                                 } else {
 414                                         trigger_error( $error['message'], E_USER_WARNING );
 415                                         $logMsg = $error['message'];
 416                                         break;
 417                                 }
 418                         }
 419                         foreach ( $readyPipes as $fd => $pipe ) {
 420                                 $block = fread( $pipe, 65536 );
 421                                 if ( $block === '' ) {
 422                                         // End of file
 423                                         fclose( $pipes[$fd] );
 424                                         unset( $pipes[$fd] );
 425                                         if ( !$pipes ) {
 426                                                 break 2;
 427                                         }
 428                                 } elseif ( $block === false ) {
 429                                         // Read error
 430                                         $logMsg = "Error reading from pipe";
 431                                         break 2;
 432                                 } elseif ( $fd == 1 ) {
 433                                         // From stdout
 434                                         $outBuffer .= $block;
 435                                 } elseif ( $fd == 2 ) {
 436                                         // From stderr
 437                                         $errBuffer .= $block;
 438                                 } elseif ( $fd == 3 ) {
 439                                         // From log FD
 440                                         $logBuffer .= $block;
 441                                         if ( strpos( $block, "\n" ) !== false ) {
 442                                                 $lines = explode( "\n", $logBuffer );
 443                                                 $logBuffer = array_pop( $lines );
 444                                                 foreach ( $lines as $line ) {
 445                                                         $this->logger->info( $line );
 446                                                 }
 447                                         }
 448                                 }
 449                         }
 450                 }
 451
 452                 foreach ( $pipes as $pipe ) {
 453                         fclose( $pipe );
 454                 }
 455
 456                 // Use the status previously collected if possible, since proc_get_status()
 457                 // just calls waitpid() which will not return anything useful the second time.
 458                 if ( $running ) {
 459                         $status = proc_get_status( $proc );
 460                 }
 461
 462                 if ( $logMsg !== false ) {
 463                         // Read/select error
 464                         $retval = -1;
 465                         proc_close( $proc );
 466                 } elseif ( $status['signaled'] ) {
 467                         $logMsg = "Exited with signal {$status['termsig']}";
 468                         $retval = 128 + $status['termsig'];
 469                         proc_close( $proc );
 470                 } else {
 471                         if ( $status['running'] ) {
 472                                 $retval = proc_close( $proc );
 473                         } else {
 474                                 $retval = $status['exitcode'];
 475                                 proc_close( $proc );
 476                         }
 477                         if ( $retval == 127 ) {
 478                                 $logMsg = "Possibly missing executable file";
 479                         } elseif ( $retval >= 129 && $retval <= 192 ) {
 480                                 $logMsg = "Probably exited with signal " . ( $retval - 128 );
 481                         }
 482                 }
 483
 484                 if ( $logMsg !== false ) {
 485                         $this->logger->warning( "$logMsg: {command}", [ 'command' => $cmd ] );
 486                 }
 487
 488                 if ( $errBuffer && $this->doLogStderr ) {
 489                         $this->logger->error( "Error running {command}: {error}", [
 490                                 'command' => $cmd,
 491                                 'error' => $errBuffer,
 492                                 'exitcode' => $retval,
 493                                 'exception' => new Exception( 'Shell error' ),
 494                         ] );
 495                 }
 496
 497                 return new Result( $retval, $outBuffer, $errBuffer );
 498         }
 499 }