Command.php

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<?php
namespace MediaWiki\Shell;
 
use Exception;
use MediaWiki\ProcOpenError;
use MediaWiki\ShellDisabledError;
use Profiler;
use Psr\Log\LoggerAwareTrait;
use Psr\Log\NullLogger;
 
class Command {
    use LoggerAwareTrait;
 
    private $command = '';
 
    private $limits = [
        // seconds
        'time' => 180,
        // seconds
        'walltime' => 180,
        // KB
        'memory' => 307200,
        // KB
        'filesize' => 102400,
    ];
 
    private $env = [];
 
    private $method;
 
    private $useStderr = false;
 
    private $everExecuted = false;
 
    private $cgroup = false;
 
    public function __construct() {
        if ( Shell::isDisabled() ) {
            throw new ShellDisabledError();
        }
 
        $this->setLogger( new NullLogger() );
    }
 
    public function __destruct() {
        if ( !$this->everExecuted ) {
            $context = [ 'command' => $this->command ];
            $message = __CLASS__ . " was instantiated, but execute() was never called.";
            if ( $this->method ) {
                $message .= ' Calling method: {method}.';
                $context['method'] = $this->method;
            }
            $message .= ' Command: {command}';
            $this->logger->warning( $message, $context );
        }
    }
 
    public function params( /* ... */ ) {
        $args = func_get_args();
        if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
            // If only one argument has been passed, and that argument is an array,
            // treat it as a list of arguments
            $args = reset( $args );
        }
        $this->command = trim( $this->command . ' ' . Shell::escape( $args ) );
 
        return $this;
    }
 
    public function unsafeParams( /* ... */ ) {
        $args = func_get_args();
        if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
            // If only one argument has been passed, and that argument is an array,
            // treat it as a list of arguments
            $args = reset( $args );
        }
        $args = array_filter( $args,
            function ( $value ) {
                return $value !== null;
            }
        );
        $this->command = trim( $this->command . ' ' . implode( ' ', $args ) );
 
        return $this;
    }
 
    public function limits( array $limits ) {
        if ( !isset( $limits['walltime'] ) && isset( $limits['time'] ) ) {
            // Emulate the behavior of old wfShellExec() where walltime fell back on time
            // if the latter was overridden and the former wasn't
            $limits['walltime'] = $limits['time'];
        }
        $this->limits = $limits + $this->limits;
 
        return $this;
    }
 
    public function environment( array $env ) {
        $this->env = $env;
 
        return $this;
    }
 
    public function profileMethod( $method ) {
        $this->method = $method;
 
        return $this;
    }
 
    public function includeStderr( $yesno = true ) {
        $this->useStderr = $yesno;
 
        return $this;
    }
 
    public function cgroup( $cgroup ) {
        $this->cgroup = $cgroup;
 
        return $this;
    }
 
    public function execute() {
        $this->everExecuted = true;
 
        $profileMethod = $this->method ?: wfGetCaller();
 
        $envcmd = '';
        foreach ( $this->env as $k => $v ) {
            if ( wfIsWindows() ) {
                /* Surrounding a set in quotes (method used by wfEscapeShellArg) makes the quotes themselves
                 * appear in the environment variable, so we must use carat escaping as documented in
                 * https://technet.microsoft.com/en-us/library/cc723564.aspx
                 * Note however that the quote isn't listed there, but is needed, and the parentheses
                 * are listed there but doesn't appear to need it.
                 */
                $envcmd .= "set $k=" . preg_replace( '/([&|()<>^"])/', '^\\1', $v ) . '&& ';
            } else {
                /* Assume this is a POSIX shell, thus required to accept variable assignments before the command
                 * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_01
                 */
                $envcmd .= "$k=" . escapeshellarg( $v ) . ' ';
            }
        }
 
        $cmd = $envcmd . trim( $this->command );
 
        $useLogPipe = false;
        if ( is_executable( '/bin/bash' ) ) {
            $time = intval( $this->limits['time'] );
            $wallTime = intval( $this->limits['walltime'] );
            $mem = intval( $this->limits['memory'] );
            $filesize = intval( $this->limits['filesize'] );
 
            if ( $time > 0 || $mem > 0 || $filesize > 0 || $wallTime > 0 ) {
                $cmd = '/bin/bash ' . escapeshellarg( __DIR__ . '/limit.sh' ) . ' ' .
                       escapeshellarg( $cmd ) . ' ' .
                       escapeshellarg(
                           "MW_INCLUDE_STDERR=" . ( $this->useStderr ? '1' : '' ) . ';' .
                           "MW_CPU_LIMIT=$time; " .
                           'MW_CGROUP=' . escapeshellarg( $this->cgroup ) . '; ' .
                           "MW_MEM_LIMIT=$mem; " .
                           "MW_FILE_SIZE_LIMIT=$filesize; " .
                           "MW_WALL_CLOCK_LIMIT=$wallTime; " .
                           "MW_USE_LOG_PIPE=yes"
                       );
                $useLogPipe = true;
            } elseif ( $this->useStderr ) {
                $cmd .= ' 2>&1';
            }
        } elseif ( $this->useStderr ) {
            $cmd .= ' 2>&1';
        }
        wfDebug( __METHOD__ . ": $cmd\n" );
 
        // Don't try to execute commands that exceed Linux's MAX_ARG_STRLEN.
        // Other platforms may be more accomodating, but we don't want to be
        // accomodating, because very long commands probably include user
        // input. See T129506.
        if ( strlen( $cmd ) > SHELL_MAX_ARG_STRLEN ) {
            throw new Exception( __METHOD__ .
                                 '(): total length of $cmd must not exceed SHELL_MAX_ARG_STRLEN' );
        }
 
        $desc = [
            0 => [ 'file', 'php://stdin', 'r' ],
            1 => [ 'pipe', 'w' ],
            2 => [ 'file', 'php://stderr', 'w' ],
        ];
        if ( $useLogPipe ) {
            $desc[3] = [ 'pipe', 'w' ];
        }
        $pipes = null;
        $scoped = Profiler::instance()->scopedProfileIn( __FUNCTION__ . '-' . $profileMethod );
        $proc = proc_open( $cmd, $desc, $pipes );
        if ( !$proc ) {
            $this->logger->error( "proc_open() failed: {command}", [ 'command' => $cmd ] );
            throw new ProcOpenError();
        }
        $outBuffer = $logBuffer = '';
        $emptyArray = [];
        $status = false;
        $logMsg = false;
 
        /* According to the documentation, it is possible for stream_select()
         * to fail due to EINTR. I haven't managed to induce this in testing
         * despite sending various signals. If it did happen, the error
         * message would take the form:
         *
         * stream_select(): unable to select [4]: Interrupted system call (max_fd=5)
         *
         * where [4] is the value of the macro EINTR and "Interrupted system
         * call" is string which according to the Linux manual is "possibly"
         * localised according to LC_MESSAGES.
         */
        $eintr = defined( 'SOCKET_EINTR' ) ? SOCKET_EINTR : 4;
        $eintrMessage = "stream_select(): unable to select [$eintr]";
 
        $running = true;
        $timeout = null;
        $numReadyPipes = 0;
 
        while ( $running === true || $numReadyPipes !== 0 ) {
            if ( $running ) {
                $status = proc_get_status( $proc );
                // If the process has terminated, switch to nonblocking selects
                // for getting any data still waiting to be read.
                if ( !$status['running'] ) {
                    $running = false;
                    $timeout = 0;
                }
            }
 
            $readyPipes = $pipes;
 
            // Clear last error
            // @codingStandardsIgnoreStart Generic.PHP.NoSilencedErrors.Discouraged
            @trigger_error( '' );
            $numReadyPipes = @stream_select( $readyPipes, $emptyArray, $emptyArray, $timeout );
            if ( $numReadyPipes === false ) {
                // @codingStandardsIgnoreEnd
                $error = error_get_last();
                if ( strncmp( $error['message'], $eintrMessage, strlen( $eintrMessage ) ) == 0 ) {
                    continue;
                } else {
                    trigger_error( $error['message'], E_USER_WARNING );
                    $logMsg = $error['message'];
                    break;
                }
            }
            foreach ( $readyPipes as $fd => $pipe ) {
                $block = fread( $pipe, 65536 );
                if ( $block === '' ) {
                    // End of file
                    fclose( $pipes[$fd] );
                    unset( $pipes[$fd] );
                    if ( !$pipes ) {
                        break 2;
                    }
                } elseif ( $block === false ) {
                    // Read error
                    $logMsg = "Error reading from pipe";
                    break 2;
                } elseif ( $fd == 1 ) {
                    // From stdout
                    $outBuffer .= $block;
                } elseif ( $fd == 3 ) {
                    // From log FD
                    $logBuffer .= $block;
                    if ( strpos( $block, "\n" ) !== false ) {
                        $lines = explode( "\n", $logBuffer );
                        $logBuffer = array_pop( $lines );
                        foreach ( $lines as $line ) {
                            $this->logger->info( $line );
                        }
                    }
                }
            }
        }
 
        foreach ( $pipes as $pipe ) {
            fclose( $pipe );
        }
 
        // Use the status previously collected if possible, since proc_get_status()
        // just calls waitpid() which will not return anything useful the second time.
        if ( $running ) {
            $status = proc_get_status( $proc );
        }
 
        if ( $logMsg !== false ) {
            // Read/select error
            $retval = -1;
            proc_close( $proc );
        } elseif ( $status['signaled'] ) {
            $logMsg = "Exited with signal {$status['termsig']}";
            $retval = 128 + $status['termsig'];
            proc_close( $proc );
        } else {
            if ( $status['running'] ) {
                $retval = proc_close( $proc );
            } else {
                $retval = $status['exitcode'];
                proc_close( $proc );
            }
            if ( $retval == 127 ) {
                $logMsg = "Possibly missing executable file";
            } elseif ( $retval >= 129 && $retval <= 192 ) {
                $logMsg = "Probably exited with signal " . ( $retval - 128 );
            }
        }
 
        if ( $logMsg !== false ) {
            $this->logger->warning( "$logMsg: {command}", [ 'command' => $cmd ] );
        }
 
        return new Result( $retval, $outBuffer );
    }
}