FirejailCommand.php

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<?php
namespace MediaWiki\Shell;
 
use RuntimeException;
 
class FirejailCommand extends Command {
 
    private $firejail;
 
    private $whitelistedPaths = [];
 
    public function __construct( string $firejail ) {
        parent::__construct();
        $this->firejail = $firejail;
    }
 
    public function params( ...$args ): Command {
        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 );
        }
        foreach ( $args as $arg ) {
            if ( substr( $arg, 0, 8 ) === '--output' ) {
                $ex = new RuntimeException(
                    'FirejailCommand does not support parameters that start with --output'
                );
                $this->logger->error(
                    'command tried to shell out with a parameter starting with --output',
                    [
                        'arg' => $arg,
                        'exception' => $ex
                    ]
                );
                throw $ex;
            }
        }
 
        return parent::params( ...$args );
    }
 
    public function whitelistPaths( array $paths ): Command {
        $this->whitelistedPaths = array_merge( $this->whitelistedPaths, $paths );
        return $this;
    }
 
    protected function buildFinalCommand( string $command ): array {
        // If there are no restrictions, don't use firejail
        if ( $this->restrictions === 0 ) {
            $splitCommand = explode( ' ', $command, 2 );
            $this->logger->debug(
                "firejail: Command {$splitCommand[0]} {params} has no restrictions",
                [ 'params' => $splitCommand[1] ?? '' ]
            );
            return parent::buildFinalCommand( $command );
        }
 
        if ( $this->firejail === false ) {
            throw new RuntimeException( 'firejail is enabled, but cannot be found' );
        }
        // quiet has to come first to prevent firejail from adding
        // any output.
        $cmd = [ $this->firejail, '--quiet' ];
        // Use a profile that allows people to add local overrides
        // if their system is setup in an incompatible manner. Also it
        // prevents any default profiles from running.
        // FIXME: Doesn't actually override command-line switches?
        $cmd[] = '--profile=' . __DIR__ . '/firejail.profile';
 
        // By default firejail hides all other user directories, so if
        // MediaWiki is inside a home directory (/home) but not the
        // current user's home directory, pass --allusers to whitelist
        // the home directories again.
        static $useAllUsers = null;
        if ( $useAllUsers === null ) {
            global $IP;
            // In case people are doing funny things with symlinks
            // or relative paths, resolve them all.
            $realIP = realpath( $IP );
            $currentUser = posix_getpwuid( posix_geteuid() );
            $useAllUsers = ( strpos( $realIP, '/home/' ) === 0 )
                && ( strpos( $realIP, $currentUser['dir'] ) !== 0 );
            if ( $useAllUsers ) {
                $this->logger->warning( 'firejail: MediaWiki is located ' .
                    'in a home directory that does not belong to the ' .
                    'current user, so allowing access to all home ' .
                    'directories (--allusers)' );
            }
        }
 
        if ( $useAllUsers ) {
            $cmd[] = '--allusers';
        }
 
        if ( $this->whitelistedPaths ) {
            // Always whitelist limit.sh
            $cmd[] = '--whitelist=' . __DIR__ . '/limit.sh';
            foreach ( $this->whitelistedPaths as $whitelistedPath ) {
                $cmd[] = "--whitelist={$whitelistedPath}";
            }
        }
 
        if ( $this->hasRestriction( Shell::NO_LOCALSETTINGS ) ) {
            $cmd[] = '--blacklist=' . realpath( MW_CONFIG_FILE );
        }
 
        if ( $this->hasRestriction( Shell::NO_ROOT ) ) {
            $cmd[] = '--noroot';
        }
 
        $useSeccomp = $this->hasRestriction( Shell::SECCOMP );
        $extraSeccomp = [];
 
        if ( $this->hasRestriction( Shell::NO_EXECVE ) ) {
            $extraSeccomp[] = 'execve';
            // Normally firejail will run commands in a bash shell,
            // but that won't work if we ban the execve syscall, so
            // run the command without a shell.
            $cmd[] = '--shell=none';
        }
 
        if ( $useSeccomp ) {
            $seccomp = '--seccomp';
            if ( $extraSeccomp ) {
                // The "@default" seccomp group will always be enabled
                $seccomp .= '=' . implode( ',', $extraSeccomp );
            }
            $cmd[] = $seccomp;
        }
 
        if ( $this->hasRestriction( Shell::PRIVATE_DEV ) ) {
            $cmd[] = '--private-dev';
        }
 
        if ( $this->hasRestriction( Shell::NO_NETWORK ) ) {
            $cmd[] = '--net=none';
        }
 
        $builtCmd = implode( ' ', $cmd );
 
        // Prefix the firejail command in front of the wanted command
        return parent::buildFinalCommand( "$builtCmd -- {$command}" );
    }
 
}