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         protected $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 string|null */
  60         private $inputString;
  61
  62         /** @var bool */
  63         private $doIncludeStderr = false;
  64
  65         /** @var bool */
  66         private $doLogStderr = false;
  67
  68         /** @var bool */
  69         private $everExecuted = false;
  70
  71         /** @var string|false */
  72         private $cgroup = false;
  73
  74         /**
  75          * bitfield with restrictions
  76          *
  77          * @var int
  78          */
  79         protected $restrictions = 0;
  80
  81         /**
  82          * Constructor. Don't call directly, instead use Shell::command()
  83          *
  84          * @throws ShellDisabledError
  85          */
  86         public function __construct() {
  87                 if ( Shell::isDisabled() ) {
  88                         throw new ShellDisabledError();
  89                 }
  90
  91                 $this->setLogger( new NullLogger() );
  92         }
  93
  94         /**
  95          * Destructor. Makes sure programmer didn't forget to execute the command after all
  96          */
  97         public function __destruct() {
  98                 if ( !$this->everExecuted ) {
  99                         $context = [ 'command' => $this->command ];
 100                         $message = __CLASS__ . " was instantiated, but execute() was never called.";
 101                         if ( $this->method ) {
 102                                 $message .= ' Calling method: {method}.';
 103                                 $context['method'] = $this->method;
 104                         }
 105                         $message .= ' Command: {command}';
 106                         $this->logger->warning( $message, $context );
 107                 }
 108         }
 109
 110         /**
 111          * Adds parameters to the command. All parameters are sanitized via Shell::escape().
 112          * Null values are ignored.
 113          *
 114          * @param string|string[] ...$args
 115          * @return $this
 116          */
 117         public function params( ...$args ): Command {
 118                 if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
 119                         // If only one argument has been passed, and that argument is an array,
 120                         // treat it as a list of arguments
 121                         $args = reset( $args );
 122                 }
 123                 $this->command = trim( $this->command . ' ' . Shell::escape( $args ) );
 124
 125                 return $this;
 126         }
 127
 128         /**
 129          * Adds unsafe parameters to the command. These parameters are NOT sanitized in any way.
 130          * Null values are ignored.
 131          *
 132          * @param string|string[] ...$args
 133          * @return $this
 134          */
 135         public function unsafeParams( ...$args ): Command {
 136                 if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
 137                         // If only one argument has been passed, and that argument is an array,
 138                         // treat it as a list of arguments
 139                         $args = reset( $args );
 140                 }
 141                 $args = array_filter( $args,
 142                         function ( $value ) {
 143                                 return $value !== null;
 144                         }
 145                 );
 146                 $this->command = trim( $this->command . ' ' . implode( ' ', $args ) );
 147
 148                 return $this;
 149         }
 150
 151         /**
 152          * Sets execution limits
 153          *
 154          * @param array $limits Associative array of limits. Keys (all optional):
 155          *   filesize (for ulimit -f), memory, time, walltime.
 156          * @return $this
 157          */
 158         public function limits( array $limits ): Command {
 159                 if ( !isset( $limits['walltime'] ) && isset( $limits['time'] ) ) {
 160                         // Emulate the behavior of old wfShellExec() where walltime fell back on time
 161                         // if the latter was overridden and the former wasn't
 162                         $limits['walltime'] = $limits['time'];
 163                 }
 164                 $this->limits = $limits + $this->limits;
 165
 166                 return $this;
 167         }
 168
 169         /**
 170          * Sets environment variables which should be added to the executed command environment
 171          *
 172          * @param string[] $env array of variable name => value
 173          * @return $this
 174          */
 175         public function environment( array $env ): Command {
 176                 $this->env = $env;
 177
 178                 return $this;
 179         }
 180
 181         /**
 182          * Sets calling function for profiler. By default, the caller for execute() will be used.
 183          *
 184          * @param string $method
 185          * @return $this
 186          */
 187         public function profileMethod( $method ): Command {
 188                 $this->method = $method;
 189
 190                 return $this;
 191         }
 192
 193         /**
 194          * Sends the provided input to the command.
 195          * When set to null (default), the command will use the standard input.
 196          * @param string|null $inputString
 197          * @return $this
 198          */
 199         public function input( $inputString ): Command {
 200                 $this->inputString = is_null( $inputString ) ? null : (string)$inputString;
 201
 202                 return $this;
 203         }
 204
 205         /**
 206          * Controls whether stderr should be included in stdout, including errors from limit.sh.
 207          * Default: don't include.
 208          *
 209          * @param bool $yesno
 210          * @return $this
 211          */
 212         public function includeStderr( $yesno = true ): Command {
 213                 $this->doIncludeStderr = $yesno;
 214
 215                 return $this;
 216         }
 217
 218         /**
 219          * When enabled, text sent to stderr will be logged with a level of 'error'.
 220          *
 221          * @param bool $yesno
 222          * @return $this
 223          */
 224         public function logStderr( $yesno = true ): Command {
 225                 $this->doLogStderr = $yesno;
 226
 227                 return $this;
 228         }
 229
 230         /**
 231          * Sets cgroup for this command
 232          *
 233          * @param string|false $cgroup Absolute file path to the cgroup, or false to not use a cgroup
 234          * @return $this
 235          */
 236         public function cgroup( $cgroup ): Command {
 237                 $this->cgroup = $cgroup;
 238
 239                 return $this;
 240         }
 241
 242         /**
 243          * Set additional restrictions for this request
 244          *
 245          * @since 1.31
 246          * @param int $restrictions
 247          * @return $this
 248          */
 249         public function restrict( $restrictions ): Command {
 250                 $this->restrictions |= $restrictions;
 251
 252                 return $this;
 253         }
 254
 255         /**
 256          * Bitfield helper on whether a specific restriction is enabled
 257          *
 258          * @param int $restriction
 259          *
 260          * @return bool
 261          */
 262         protected function hasRestriction( $restriction ) {
 263                 return ( $this->restrictions & $restriction ) === $restriction;
 264         }
 265
 266         /**
 267          * If called, only the files/directories that are
 268          * whitelisted will be available to the shell command.
 269          *
 270          * limit.sh will always be whitelisted
 271          *
 272          * @param string[] $paths
 273          *
 274          * @return $this
 275          */
 276         public function whitelistPaths( array $paths ): Command {
 277                 // Default implementation is a no-op
 278                 return $this;
 279         }
 280
 281         /**
 282          * String together all the options and build the final command
 283          * to execute
 284          *
 285          * @param string $command Already-escaped command to run
 286          * @return array [ command, whether to use log pipe ]
 287          */
 288         protected function buildFinalCommand( $command ) {
 289                 $envcmd = '';
 290                 foreach ( $this->env as $k => $v ) {
 291                         if ( wfIsWindows() ) {
 292                                 /* Surrounding a set in quotes (method used by wfEscapeShellArg) makes the quotes themselves
 293                                  * appear in the environment variable, so we must use carat escaping as documented in
 294                                  * https://technet.microsoft.com/en-us/library/cc723564.aspx
 295                                  * Note however that the quote isn't listed there, but is needed, and the parentheses
 296                                  * are listed there but doesn't appear to need it.
 297                                  */
 298                                 $envcmd .= "set $k=" . preg_replace( '/([&|()<>^"])/', '^\\1', $v ) . '&& ';
 299                         } else {
 300                                 /* Assume this is a POSIX shell, thus required to accept variable assignments before the command
 301                                  * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_01
 302                                  */
 303                                 $envcmd .= "$k=" . escapeshellarg( $v ) . ' ';
 304                         }
 305                 }
 306
 307                 $useLogPipe = false;
 308                 $cmd = $envcmd . trim( $command );
 309
 310                 if ( is_executable( '/bin/bash' ) ) {
 311                         $time = intval( $this->limits['time'] );
 312                         $wallTime = intval( $this->limits['walltime'] );
 313                         $mem = intval( $this->limits['memory'] );
 314                         $filesize = intval( $this->limits['filesize'] );
 315
 316                         if ( $time > 0 || $mem > 0 || $filesize > 0 || $wallTime > 0 ) {
 317                                 $cmd = '/bin/bash ' . escapeshellarg( __DIR__ . '/limit.sh' ) . ' ' .
 318                                         escapeshellarg( $cmd ) . ' ' .
 319                                         escapeshellarg(
 320                                                 "MW_INCLUDE_STDERR=" . ( $this->doIncludeStderr ? '1' : '' ) . ';' .
 321                                                 "MW_CPU_LIMIT=$time; " .
 322                                                 'MW_CGROUP=' . escapeshellarg( $this->cgroup ) . '; ' .
 323                                                 "MW_MEM_LIMIT=$mem; " .
 324                                                 "MW_FILE_SIZE_LIMIT=$filesize; " .
 325                                                 "MW_WALL_CLOCK_LIMIT=$wallTime; " .
 326                                                 "MW_USE_LOG_PIPE=yes"
 327                                         );
 328                                 $useLogPipe = true;
 329                         }
 330                 }
 331                 if ( !$useLogPipe && $this->doIncludeStderr ) {
 332                         $cmd .= ' 2>&1';
 333                 }
 334
 335                 return [ $cmd, $useLogPipe ];
 336         }
 337
 338         /**
 339          * Executes command. Afterwards, getExitCode() and getOutput() can be used to access execution
 340          * results.
 341          *
 342          * @return Result
 343          * @throws Exception
 344          * @throws ProcOpenError
 345          * @throws ShellDisabledError
 346          */
 347         public function execute() {
 348                 $this->everExecuted = true;
 349
 350                 $profileMethod = $this->method ?: wfGetCaller();
 351
 352                 list( $cmd, $useLogPipe ) = $this->buildFinalCommand( $this->command );
 353
 354                 $this->logger->debug( __METHOD__ . ": $cmd" );
 355
 356                 // Don't try to execute commands that exceed Linux's MAX_ARG_STRLEN.
 357                 // Other platforms may be more accomodating, but we don't want to be
 358                 // accomodating, because very long commands probably include user
 359                 // input. See T129506.
 360                 if ( strlen( $cmd ) > SHELL_MAX_ARG_STRLEN ) {
 361                         throw new Exception( __METHOD__ .
 362                                 '(): total length of $cmd must not exceed SHELL_MAX_ARG_STRLEN' );
 363                 }
 364
 365                 $desc = [
 366                         0 => $this->inputString === null ? [ 'file', 'php://stdin', 'r' ] : [ 'pipe', 'r' ],
 367                         1 => [ 'pipe', 'w' ],
 368                         2 => [ 'pipe', 'w' ],
 369                 ];
 370                 if ( $useLogPipe ) {
 371                         $desc[3] = [ 'pipe', 'w' ];
 372                 }
 373                 $pipes = null;
 374                 $scoped = Profiler::instance()->scopedProfileIn( __FUNCTION__ . '-' . $profileMethod );
 375                 $proc = proc_open( $cmd, $desc, $pipes );
 376                 if ( !$proc ) {
 377                         $this->logger->error( "proc_open() failed: {command}", [ 'command' => $cmd ] );
 378                         throw new ProcOpenError();
 379                 }
 380
 381                 $buffers = [
 382                         0 => $this->inputString, // input
 383                         1 => '', // stdout
 384                         2 => null, // stderr
 385                         3 => '', // log
 386                 ];
 387                 $emptyArray = [];
 388                 $status = false;
 389                 $logMsg = false;
 390
 391                 /* According to the documentation, it is possible for stream_select()
 392                  * to fail due to EINTR. I haven't managed to induce this in testing
 393                  * despite sending various signals. If it did happen, the error
 394                  * message would take the form:
 395                  *
 396                  * stream_select(): unable to select [4]: Interrupted system call (max_fd=5)
 397                  *
 398                  * where [4] is the value of the macro EINTR and "Interrupted system
 399                  * call" is string which according to the Linux manual is "possibly"
 400                  * localised according to LC_MESSAGES.
 401                  */
 402                 $eintr = defined( 'SOCKET_EINTR' ) ? SOCKET_EINTR : 4;
 403                 $eintrMessage = "stream_select(): unable to select [$eintr]";
 404
 405                 /* The select(2) system call only guarantees a "sufficiently small write"
 406                  * can be made without blocking. And on Linux the read might block too
 407                  * in certain cases, although I don't know if any of them can occur here.
 408                  * Regardless, set all the pipes to non-blocking to avoid T184171.
 409                  */
 410                 foreach ( $pipes as $pipe ) {
 411                         stream_set_blocking( $pipe, false );
 412                 }
 413
 414                 $running = true;
 415                 $timeout = null;
 416                 $numReadyPipes = 0;
 417
 418                 while ( $pipes && ( $running === true || $numReadyPipes !== 0 ) ) {
 419                         if ( $running ) {
 420                                 $status = proc_get_status( $proc );
 421                                 // If the process has terminated, switch to nonblocking selects
 422                                 // for getting any data still waiting to be read.
 423                                 if ( !$status['running'] ) {
 424                                         $running = false;
 425                                         $timeout = 0;
 426                                 }
 427                         }
 428
 429                         // clear get_last_error without actually raising an error
 430                         // from https://www.php.net/manual/en/function.error-get-last.php#113518
 431                         // TODO replace with clear_last_error when requirements are bumped to PHP7
 432                         set_error_handler( function () {
 433                         }, 0 );
 434                         \Wikimedia\suppressWarnings();
 435                         trigger_error( '' );
 436                         \Wikimedia\restoreWarnings();
 437                         restore_error_handler();
 438
 439                         $readPipes = array_filter( $pipes, function ( $fd ) use ( $desc ) {
 440                                 return $desc[$fd][0] === 'pipe' && $desc[$fd][1] === 'r';
 441                         }, ARRAY_FILTER_USE_KEY );
 442                         $writePipes = array_filter( $pipes, function ( $fd ) use ( $desc ) {
 443                                 return $desc[$fd][0] === 'pipe' && $desc[$fd][1] === 'w';
 444                         }, ARRAY_FILTER_USE_KEY );
 445                         // stream_select parameter names are from the POV of us being able to do the operation;
 446                         // proc_open desriptor types are from the POV of the process doing it.
 447                         // So $writePipes is passed as the $read parameter and $readPipes as $write.
 448                         // phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
 449                         $numReadyPipes = @stream_select( $writePipes, $readPipes, $emptyArray, $timeout );
 450                         if ( $numReadyPipes === false ) {
 451                                 $error = error_get_last();
 452                                 if ( strncmp( $error['message'], $eintrMessage, strlen( $eintrMessage ) ) == 0 ) {
 453                                         continue;
 454                                 } else {
 455                                         trigger_error( $error['message'], E_USER_WARNING );
 456                                         $logMsg = $error['message'];
 457                                         break;
 458                                 }
 459                         }
 460                         foreach ( $writePipes + $readPipes as $fd => $pipe ) {
 461                                 // True if a pipe is unblocked for us to write into, false if for reading from
 462                                 $isWrite = array_key_exists( $fd, $readPipes );
 463
 464                                 if ( $isWrite ) {
 465                                         // Don't bother writing if the buffer is empty
 466                                         if ( $buffers[$fd] === '' ) {
 467                                                 fclose( $pipes[$fd] );
 468                                                 unset( $pipes[$fd] );
 469                                                 continue;
 470                                         }
 471                                         $res = fwrite( $pipe, $buffers[$fd], 65536 );
 472                                 } else {
 473                                         $res = fread( $pipe, 65536 );
 474                                 }
 475
 476                                 if ( $res === false ) {
 477                                         $logMsg = 'Error ' . ( $isWrite ? 'writing to' : 'reading from' ) . ' pipe';
 478                                         break 2;
 479                                 }
 480
 481                                 if ( $res === '' || $res === 0 ) {
 482                                         // End of file?
 483                                         if ( feof( $pipe ) ) {
 484                                                 fclose( $pipes[$fd] );
 485                                                 unset( $pipes[$fd] );
 486                                         }
 487                                 } elseif ( $isWrite ) {
 488                                         $buffers[$fd] = (string)substr( $buffers[$fd], $res );
 489                                         if ( $buffers[$fd] === '' ) {
 490                                                 fclose( $pipes[$fd] );
 491                                                 unset( $pipes[$fd] );
 492                                         }
 493                                 } else {
 494                                         $buffers[$fd] .= $res;
 495                                         if ( $fd === 3 && strpos( $res, "\n" ) !== false ) {
 496                                                 // For the log FD, every line is a separate log entry.
 497                                                 $lines = explode( "\n", $buffers[3] );
 498                                                 $buffers[3] = array_pop( $lines );
 499                                                 foreach ( $lines as $line ) {
 500                                                         $this->logger->info( $line );
 501                                                 }
 502                                         }
 503                                 }
 504                         }
 505                 }
 506
 507                 foreach ( $pipes as $pipe ) {
 508                         fclose( $pipe );
 509                 }
 510
 511                 // Use the status previously collected if possible, since proc_get_status()
 512                 // just calls waitpid() which will not return anything useful the second time.
 513                 if ( $running ) {
 514                         $status = proc_get_status( $proc );
 515                 }
 516
 517                 if ( $logMsg !== false ) {
 518                         // Read/select error
 519                         $retval = -1;
 520                         proc_close( $proc );
 521                 } elseif ( $status['signaled'] ) {
 522                         $logMsg = "Exited with signal {$status['termsig']}";
 523                         $retval = 128 + $status['termsig'];
 524                         proc_close( $proc );
 525                 } else {
 526                         if ( $status['running'] ) {
 527                                 $retval = proc_close( $proc );
 528                         } else {
 529                                 $retval = $status['exitcode'];
 530                                 proc_close( $proc );
 531                         }
 532                         if ( $retval == 127 ) {
 533                                 $logMsg = "Possibly missing executable file";
 534                         } elseif ( $retval >= 129 && $retval <= 192 ) {
 535                                 $logMsg = "Probably exited with signal " . ( $retval - 128 );
 536                         }
 537                 }
 538
 539                 if ( $logMsg !== false ) {
 540                         $this->logger->warning( "$logMsg: {command}", [ 'command' => $cmd ] );
 541                 }
 542
 543                 if ( $buffers[2] && $this->doLogStderr ) {
 544                         $this->logger->error( "Error running {command}: {error}", [
 545                                 'command' => $cmd,
 546                                 'error' => $buffers[2],
 547                                 'exitcode' => $retval,
 548                                 'exception' => new Exception( 'Shell error' ),
 549                         ] );
 550                 }
 551
 552                 return new Result( $retval, $buffers[1], $buffers[2] );
 553         }
 554
 555         /**
 556          * Returns the final command line before environment/limiting, etc are applied.
 557          * Use string conversion only for debugging, don't try to pass this to
 558          * some other execution medium.
 559          *
 560          * @return string
 561          */
 562         public function __toString() {
 563                 return "#Command: {$this->command}";
 564         }
 565 }