mitogen/econtext/sudo.py

import logging
import os
import pty
import termios
import time

import econtext.master


LOG = logging.getLogger(__name__)
PASSWORD_PROMPT = 'password'


def flags(names):
    """Return the result of ORing a set of (space separated) :py:mod:`termios`
    module constants together."""
    return sum(getattr(termios, name) for name in names.split())


def cfmakeraw((iflag, oflag, cflag, lflag, ispeed, ospeed, cc)):
    """Given a list returned by :py:func:`termios.tcgetattr`, return a list
    that has been modified in the same manner as the `cfmakeraw()` C library
    function."""
    iflag &= ~flags('IGNBRK BRKINT PARMRK ISTRIP INLCR IGNCR ICRNL IXON')
    oflag &= ~flags('OPOST IXOFF')
    lflag &= ~flags('ECHO ECHOE ECHONL ICANON ISIG IEXTEN')
    cflag &= ~flags('CSIZE PARENB')
    cflag |= flags('CS8')

    iflag = 0
    oflag = 0
    lflag = 0
    return [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]


def disable_echo(fd):
    old = termios.tcgetattr(fd)
    new = cfmakeraw(old)
    #new = old[:]
    #new[3] &= ~flags('ECHO')
    tcsetattr_flags = termios.TCSAFLUSH
    if hasattr(termios, 'TCSASOFT'):
        tcsetattr_flags |= termios.TCSASOFT
    termios.tcsetattr(fd, tcsetattr_flags, new)


def tty_create_child(*args):
    master_fd, slave_fd = os.openpty()
    import econtext.core
    #econtext.core.set_nonblocking(master_fd)
    disable_echo(master_fd)
    disable_echo(slave_fd)

    pid = os.fork()
    if not pid:
        os.dup2(slave_fd, 0)
        os.dup2(slave_fd, 1)
        os.dup2(slave_fd, 2)
        os.close(slave_fd)
        os.close(master_fd)
        #os.setsid()
        os.close(os.open(os.ttyname(1), os.O_RDWR))
        os.execvp(args[0], args)
        raise SystemExit

    os.close(slave_fd)
    LOG.debug('tty_create_child() child %d fd %d, parent %d, args %r',
              pid, master_fd, os.getpid(), args)
    return pid, master_fd


class StateMachine(object):
    S_PW_PROMPT, S_SHELL, S_CONNECTED = range(3)
    state = S_PW_PROMPT


class Stream(econtext.master.Stream):
    create_child = staticmethod(tty_create_child)
    sudo_path = 'sudo'
    password = None

    def get_boot_command(self):
        bits = [self.sudo_path, '-S', '-u', self._context.username]
        return bits + super(Stream, self).get_boot_command()

    def _connect_bootstrap(self):
        password_sent = False
        it = econtext.master.iter_read(self.receive_side.fd,
                                       time.time() + 10.0)

        for buf in it:
            if buf.endswith('EC0\n'):
                return self._ec0_received()
            elif (not password_sent) and 'password' in buf.lower():
                if self.password is None:
                    raise econtext.core.StreamError('password required')
                LOG.debug('sending password')
                os.write(self.transmit_side.fd, self.password + '\n')
                password_sent = True
        else:
            raise econtext.core.StreamError('bootstrap failed')


def connect(broker, username=None, sudo_path=None, python_path=None, password=None):
    """Get the named sudo context, creating it if it does not exist."""
    if username is None:
        username = 'root'

    context = econtext.master.Context(
        broker=broker,
        name='sudo:' + username,
        username=username)

    context.stream = Stream(context)
    if sudo_path:
        context.stream.sudo_path = sudo_path
    if password:
        context.stream.password = password
    if python_path:
        context.stream.python_path = python_path
    context.stream.connect()
    return broker.register(context)