onionshare/tails/lib/stem/process.py

# Copyright 2011-2013, Damian Johnson and The Tor Project
# See LICENSE for licensing information

"""
Helper functions for working with tor as a process.

:NO_TORRC:
  when provided as a torrc_path tor is ran with a blank configuration

:DEFAULT_INIT_TIMEOUT:
  number of seconds before we time out our attempt to start a tor instance

**Module Overview:**

::

  launch_tor             - starts up a tor process
  launch_tor_with_config - starts a tor process with a custom torrc
"""

import os
import re
import signal
import subprocess
import tempfile

import stem.prereq
import stem.util.system

NO_TORRC = "<no torrc>"
DEFAULT_INIT_TIMEOUT = 90


def launch_tor(tor_cmd = "tor", args = None, torrc_path = None, completion_percent = 100, init_msg_handler = None, timeout = DEFAULT_INIT_TIMEOUT, take_ownership = False):
  """
  Initializes a tor process. This blocks until initialization completes or we
  error out.

  If tor's data directory is missing or stale then bootstrapping will include
  making several requests to the directory authorities which can take a little
  while. Usually this is done in 50 seconds or so, but occasionally calls seem
  to get stuck, taking well over the default timeout.

  **To work to must log at NOTICE runlevel to stdout.** It does this by
  default, but if you have a 'Log' entry in your torrc then you'll also need
  'Log NOTICE stdout'.

  Note: The timeout argument does not work on Windows, and relies on the global
  state of the signal module.

  :param str tor_cmd: command for starting tor
  :param list args: additional arguments for tor
  :param str torrc_path: location of the torrc for us to use
  :param int completion_percent: percent of bootstrap completion at which
    this'll return
  :param functor init_msg_handler: optional functor that will be provided with
    tor's initialization stdout as we get it
  :param int timeout: time after which the attempt to start tor is aborted, no
    timeouts are applied if **None**
  :param bool take_ownership: asserts ownership over the tor process so it
    aborts if this python process terminates or a :class:`~stem.control.Controller`
    we establish to it disconnects

  :returns: **subprocess.Popen** instance for the tor subprocess

  :raises: **OSError** if we either fail to create the tor process or reached a
    timeout without success
  """

  if stem.util.system.is_windows():
    timeout = None

  # sanity check that we got a tor binary

  if os.path.sep in tor_cmd:
    # got a path (either relative or absolute), check what it leads to

    if os.path.isdir(tor_cmd):
      raise OSError("'%s' is a directory, not the tor executable" % tor_cmd)
    elif not os.path.isfile(tor_cmd):
      raise OSError("'%s' doesn't exist" % tor_cmd)
  elif not stem.util.system.is_available(tor_cmd):
    raise OSError("'%s' isn't available on your system. Maybe it's not in your PATH?" % tor_cmd)

  # double check that we have a torrc to work with
  if not torrc_path in (None, NO_TORRC) and not os.path.exists(torrc_path):
    raise OSError("torrc doesn't exist (%s)" % torrc_path)

  # starts a tor subprocess, raising an OSError if it fails
  runtime_args, temp_file = [tor_cmd], None

  if args:
    runtime_args += args

  if torrc_path:
    if torrc_path == NO_TORRC:
      temp_file = tempfile.mkstemp(prefix = "empty-torrc-", text = True)[1]
      runtime_args += ["-f", temp_file]
    else:
      runtime_args += ["-f", torrc_path]

  if take_ownership:
    runtime_args += ["__OwningControllerProcess", str(os.getpid())]

  tor_process = subprocess.Popen(runtime_args, stdout = subprocess.PIPE, stderr = subprocess.PIPE)

  if timeout:
    def timeout_handler(signum, frame):
      # terminates the uninitialized tor process and raise on timeout
      if temp_file:
        try:
          os.remove(temp_file)
        except:
          pass

      tor_process.kill()

      raise OSError("reached a %i second timeout without success" % timeout)

    signal.signal(signal.SIGALRM, timeout_handler)
    signal.alarm(timeout)

  bootstrap_line = re.compile("Bootstrapped ([0-9]+)%: ")
  problem_line = re.compile("\[(warn|err)\] (.*)$")
  last_problem = "Timed out"

  while True:
    # Tor's stdout will be read as ASCII bytes. This is fine for python 2, but
    # in python 3 that means it'll mismatch with other operations (for instance
    # the bootstrap_line.search() call later will fail).
    #
    # It seems like python 2.x is perfectly happy for this to be unicode, so
    # normalizing to that.

    init_line = tor_process.stdout.readline().decode("utf-8", "replace").strip()

    # this will provide empty results if the process is terminated
    if not init_line:
      if timeout:
        signal.alarm(0)  # stop alarm

      # ... but best make sure

      tor_process.kill()

      raise OSError("Process terminated: %s" % last_problem)

    # provide the caller with the initialization message if they want it

    if init_msg_handler:
      init_msg_handler(init_line)

    # return the process if we're done with bootstrapping
    bootstrap_match = bootstrap_line.search(init_line)
    problem_match = problem_line.search(init_line)

    if bootstrap_match and int(bootstrap_match.groups()[0]) >= completion_percent:
      if timeout:
        signal.alarm(0)  # stop alarm

      if temp_file:
        try:
          os.remove(temp_file)
        except:
          pass

      return tor_process
    elif problem_match:
      runlevel, msg = problem_match.groups()

      if not "see warnings above" in msg:
        if ": " in msg:
          msg = msg.split(": ")[-1].strip()

        last_problem = msg


def launch_tor_with_config(config, tor_cmd = "tor", completion_percent = 100, init_msg_handler = None, timeout = DEFAULT_INIT_TIMEOUT, take_ownership = False):
  """
  Initializes a tor process, like :func:`~stem.process.launch_tor`, but with a
  customized configuration. This writes a temporary torrc to disk, launches
  tor, then deletes the torrc.

  For example...

  ::

    tor_process = stem.process.launch_tor_with_config(
      config = {
        'ControlPort': '2778',
        'Log': [
          'NOTICE stdout',
          'ERR file /tmp/tor_error_log',
        ],
      },
    )

  :param dict config: configuration options, such as '{"ControlPort": "9051"}',
    values can either be a **str** or **list of str** if for multiple values
  :param str tor_cmd: command for starting tor
  :param int completion_percent: percent of bootstrap completion at which
    this'll return
  :param functor init_msg_handler: optional functor that will be provided with
    tor's initialization stdout as we get it
  :param int timeout: time after which the attempt to start tor is aborted, no
    timeouts are applied if **None**
  :param bool take_ownership: asserts ownership over the tor process so it
    aborts if this python process terminates or a :class:`~stem.control.Controller`
    we establish to it disconnects

  :returns: **subprocess.Popen** instance for the tor subprocess

  :raises: **OSError** if we either fail to create the tor process or reached a
    timeout without success
  """

  # we need to be sure that we're logging to stdout to figure out when we're
  # done bootstrapping

  if 'Log' in config:
    stdout_options = ['DEBUG stdout', 'INFO stdout', 'NOTICE stdout']

    if isinstance(config['Log'], str):
      config['Log'] = [config['Log']]

    has_stdout = False

    for log_config in config['Log']:
      if log_config in stdout_options:
        has_stdout = True
        break

    if not has_stdout:
      config['Log'].append('NOTICE stdout')

  torrc_path = tempfile.mkstemp(prefix = "torrc-", text = True)[1]

  try:
    with open(torrc_path, "w") as torrc_file:
      for key, values in config.items():
        if isinstance(values, str):
          torrc_file.write("%s %s\n" % (key, values))
        else:
          for value in values:
            torrc_file.write("%s %s\n" % (key, value))

    # prevents tor from erroring out due to a missing torrc if it gets a sighup
    args = ['__ReloadTorrcOnSIGHUP', '0']

    return launch_tor(tor_cmd, args, torrc_path, completion_percent, init_msg_handler, timeout, take_ownership)
  finally:
    try:
      os.remove(torrc_path)
    except:
      pass