core-admin-client/qubesadmin/app.py
Marek Marczykowski-Górecki 218d43a2e0
Add simple properties caching
Reduce Admin API calls by caching returned values. The cache is not
enabled by default, because it could result in stale values being
returned. It can be enabled by setting 'cache_enabled' to True on
Qubes() object. This is safe in two cases:
 - the application don't care about changed values - like a short-lived
   process that retrieve values once (for example qvm-ls)
 - the application listen for events and invalidate cache when property
   is changed

For the second case, invalidating the cache on appropriate event
(property-set:*, property-reset:*) is done before calling other event
handlers. This is because the event may try to access the property value
(not necessary from the event arguments), so we need to be sure it will
see the new value.

Fixes QubesOS/qubes-issues#5415
2020-05-22 18:59:44 +02:00

820 lines
30 KiB
Python

# -*- encoding: utf-8 -*-
#
# The Qubes OS Project, http://www.qubes-os.org
#
# Copyright (C) 2017 Marek Marczykowski-Górecki
# <marmarek@invisiblethingslab.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with this program; if not, see <http://www.gnu.org/licenses/>.
"""
Main Qubes() class and related classes.
"""
import os
import shlex
import socket
import shutil
import subprocess
import sys
import logging
import qubesadmin.base
import qubesadmin.exc
import qubesadmin.label
import qubesadmin.storage
import qubesadmin.utils
import qubesadmin.vm
import qubesadmin.config
import qubesadmin.devices
class VMCollection(object):
"""Collection of VMs objects"""
def __init__(self, app):
self.app = app
self._vm_list = None
self._vm_objects = {}
def clear_cache(self):
"""Clear cached list of VMs"""
self._vm_list = None
def refresh_cache(self, force=False):
"""Refresh cached list of VMs"""
if not force and self._vm_list is not None:
return
vm_list_data = self.app.qubesd_call(
'dom0',
'admin.vm.List'
)
new_vm_list = {}
# FIXME: this will probably change
for vm_data in vm_list_data.splitlines():
vm_name, props = vm_data.decode('ascii').split(' ', 1)
vm_name = str(vm_name)
props = props.split(' ')
new_vm_list[vm_name] = dict(
[vm_prop.split('=', 1) for vm_prop in props])
self._vm_list = new_vm_list
for name, vm in list(self._vm_objects.items()):
if vm.name not in self._vm_list:
# VM no longer exists
del self._vm_objects[name]
elif vm.__class__.__name__ != self._vm_list[vm.name]['class']:
# VM class have changed
del self._vm_objects[name]
# TODO: some generation ID, to detect VM re-creation
elif name != vm.name:
# renamed
self._vm_objects[vm.name] = vm
del self._vm_objects[name]
def __getitem__(self, item):
if isinstance(item, qubesadmin.vm.QubesVM):
item = item.name
if not self.app.blind_mode and item not in self:
raise KeyError(item)
return self.get_blind(item)
def get_blind(self, item):
"""
Get a vm without downloading the list
and checking if exists
"""
if item not in self._vm_objects:
cls = qubesadmin.vm.QubesVM
# provide class name to constructor, if already cached (which can be
# done by 'item not in self' check above, unless blind_mode is
# enabled
klass = None
if self._vm_list and item in self._vm_list:
klass = self._vm_list[item]['class']
self._vm_objects[item] = cls(self.app, item, klass=klass)
return self._vm_objects[item]
def __contains__(self, item):
if isinstance(item, qubesadmin.vm.QubesVM):
item = item.name
self.refresh_cache()
return item in self._vm_list
def __delitem__(self, key):
self.app.qubesd_call(key, 'admin.vm.Remove')
self.clear_cache()
def __iter__(self):
self.refresh_cache()
for vm in sorted(self._vm_list):
yield self[vm]
def keys(self):
"""Get list of VM names."""
self.refresh_cache()
return self._vm_list.keys()
def values(self):
"""Get list of VM objects."""
self.refresh_cache()
return [self[name] for name in self._vm_list]
class QubesBase(qubesadmin.base.PropertyHolder):
"""Main Qubes application.
This is a base abstract class, don't use it directly. Use specialized
class in py:class:`qubesadmin.Qubes` instead, which points at
:py:class:`QubesLocal` or :py:class:`QubesRemote`.
"""
#: domains (VMs) collection
domains = None
#: labels collection
labels = None
#: storage pools
pools = None
#: type of qubesd connection: either 'socket' or 'qrexec'
qubesd_connection_type = None
#: logger
log = None
#: do not check for object (VM, label etc) existence before really needed
blind_mode = False
#: cache retrieved properties values
cache_enabled = False
def __init__(self):
super(QubesBase, self).__init__(self, 'admin.property.', 'dom0')
self.domains = VMCollection(self)
self.labels = qubesadmin.base.WrapperObjectsCollection(
self, 'admin.label.List', qubesadmin.label.Label)
self.pools = qubesadmin.base.WrapperObjectsCollection(
self, 'admin.pool.List', qubesadmin.storage.Pool)
#: cache for available storage pool drivers and options to create them
self._pool_drivers = None
self.log = logging.getLogger('app')
self._local_name = None
def list_vmclass(self):
"""Call Qubesd in order to obtain the vm classes list"""
vmclass = self.qubesd_call('dom0', 'admin.vmclass.List') \
.decode().splitlines()
return sorted(vmclass)
def list_deviceclass(self):
"""Call Qubesd in order to obtain the device classes list"""
deviceclasses = self.qubesd_call('dom0', 'admin.deviceclass.List') \
.decode().splitlines()
return sorted(deviceclasses)
def _refresh_pool_drivers(self):
"""
Refresh cached storage pool drivers and their parameters.
:return: None
"""
if self._pool_drivers is None:
pool_drivers_data = self.qubesd_call(
'dom0', 'admin.pool.ListDrivers', None, None)
assert pool_drivers_data.endswith(b'\n')
pool_drivers = {}
for driver_line in pool_drivers_data.decode('ascii').splitlines():
if not driver_line:
continue
driver_name, driver_options = driver_line.split(' ', 1)
pool_drivers[driver_name] = driver_options.split(' ')
self._pool_drivers = pool_drivers
@property
def pool_drivers(self):
""" Available storage pool drivers """
self._refresh_pool_drivers()
return self._pool_drivers.keys()
def pool_driver_parameters(self, driver):
""" Parameters to initialize storage pool using given driver """
self._refresh_pool_drivers()
return self._pool_drivers[driver]
def add_pool(self, name, driver, **kwargs):
""" Add a storage pool to config
:param name: name of storage pool to create
:param driver: driver to use, see :py:meth:`pool_drivers` for
available drivers
:param kwargs: configuration parameters for storage pool,
see :py:meth:`pool_driver_parameters` for a list
"""
# sort parameters only to ease testing, not required by API
payload = 'name={}\n'.format(name) + \
''.join('{}={}\n'.format(key, value)
for key, value in sorted(kwargs.items()))
self.qubesd_call('dom0', 'admin.pool.Add', driver,
payload.encode('utf-8'))
def remove_pool(self, name):
""" Remove a storage pool """
self.qubesd_call('dom0', 'admin.pool.Remove', name, None)
@property
def local_name(self):
""" Get localhost name """
if not self._local_name:
self._local_name = os.uname()[1]
return self._local_name
def get_label(self, label):
"""Get label as identified by index or name
:throws KeyError: when label is not found
"""
# first search for name, verbatim
try:
return self.labels[label]
except KeyError:
pass
# then search for index
if isinstance(label, int) or label.isdigit():
for i in self.labels.values():
if i.index == int(label):
return i
raise KeyError(label)
@staticmethod
def get_vm_class(clsname):
"""Find the class for a domain.
Compatibility function, client tools use str to identify domain classes.
:param str clsname: name of the class
:return str: class
"""
return clsname
def add_new_vm(self, cls, name, label, template=None, pool=None,
pools=None):
"""Create new Virtual Machine
Example usage with custom storage pools:
>>> app = qubesadmin.Qubes()
>>> pools = {'private': 'external'}
>>> vm = app.add_new_vm('AppVM', 'my-new-vm', 'red',
>>> 'my-template', pools=pools)
>>> vm.netvm = app.domains['sys-whonix']
:param str cls: name of VM class (`AppVM`, `TemplateVM` etc)
:param str name: name of VM
:param str label: label color for new VM
:param str template: template to use (if apply for given VM class),
can be also VM object; use None for default value
:param str pool: storage pool to use instead of default one
:param dict pools: storage pool for specific volumes
:return new VM object
"""
if not isinstance(cls, str):
cls = cls.__name__
if template is qubesadmin.DEFAULT:
template = None
elif template is not None:
template = str(template)
if pool and pools:
raise ValueError('only one of pool= and pools= can be used')
method_prefix = 'admin.vm.Create.'
payload = 'name={} label={}'.format(name, label)
if pool:
payload += ' pool={}'.format(str(pool))
method_prefix = 'admin.vm.CreateInPool.'
if pools:
payload += ''.join(' pool:{}={}'.format(vol, str(pool))
for vol, pool in sorted(pools.items()))
method_prefix = 'admin.vm.CreateInPool.'
self.qubesd_call('dom0', method_prefix + cls, template,
payload.encode('utf-8'))
self.domains.clear_cache()
return self.domains[name]
def clone_vm(self, src_vm, new_name, new_cls=None, pool=None, pools=None,
ignore_errors=False, ignore_volumes=None,
ignore_devices=False):
# pylint: disable=too-many-statements
"""Clone Virtual Machine
Example usage with custom storage pools:
>>> app = qubesadmin.Qubes()
>>> pools = {'private': 'external'}
>>> src_vm = app.domains['personal']
>>> vm = app.clone_vm(src_vm, 'my-new-vm', pools=pools)
>>> vm.label = app.labels['green']
:param QubesVM or str src_vm: source VM
:param str new_name: name of new VM
:param str new_cls: name of VM class (`AppVM`, `TemplateVM` etc) - use
None to copy it from *src_vm*
:param str pool: storage pool to use instead of default one
:param dict pools: storage pool for specific volumes
:param bool ignore_errors: should errors on meta-data setting be only
logged, or abort the whole operation?
:param list ignore_volumes: do not clone volumes on this list,
like 'private' or 'root'
:param bool ignore_devices: if True, do not copy device assignments
:return new VM object
"""
if pool and pools:
raise ValueError('only one of pool= and pools= can be used')
if isinstance(src_vm, str):
src_vm = self.domains[src_vm]
if new_cls is None:
new_cls = src_vm.klass
template = getattr(src_vm, 'template', None)
if template is not None:
template = str(template)
label = src_vm.label
if pool is None and pools is None:
# use the same pools as the source - check if non default is used
for volume in sorted(src_vm.volumes.values()):
if not volume.save_on_stop:
# clone only persistent volumes
continue
if ignore_volumes and volume.name in ignore_volumes:
continue
default_pool = getattr(self.app, 'default_pool_' + volume.name,
volume.pool)
if default_pool != volume.pool:
if pools is None:
pools = {}
pools[volume.name] = volume.pool
method_prefix = 'admin.vm.Create.'
payload = 'name={} label={}'.format(new_name, label)
if pool:
payload += ' pool={}'.format(str(pool))
method_prefix = 'admin.vm.CreateInPool.'
if pools:
payload += ''.join(' pool:{}={}'.format(vol, str(pool))
for vol, pool in sorted(pools.items()))
method_prefix = 'admin.vm.CreateInPool.'
self.qubesd_call('dom0', method_prefix + new_cls, template,
payload.encode('utf-8'))
self.domains.clear_cache()
dst_vm = self.domains[new_name]
try:
assert isinstance(dst_vm, qubesadmin.vm.QubesVM)
for prop in src_vm.property_list():
# handled by admin.vm.Create call
if prop in ('name', 'qid', 'template', 'label', 'uuid',
'installed_by_rpm'):
continue
if src_vm.property_is_default(prop):
continue
try:
setattr(dst_vm, prop, getattr(src_vm, prop))
except AttributeError:
pass
except qubesadmin.exc.QubesException as e:
dst_vm.log.error(
'Failed to set {!s} property: {!s}'.format(prop, e))
if not ignore_errors:
raise
for tag in src_vm.tags:
if tag.startswith('created-by-'):
continue
try:
dst_vm.tags.add(tag)
except qubesadmin.exc.QubesException as e:
dst_vm.log.error(
'Failed to add {!s} tag: {!s}'.format(tag, e))
if not ignore_errors:
raise
for feature, value in src_vm.features.items():
try:
dst_vm.features[feature] = value
except qubesadmin.exc.QubesException as e:
dst_vm.log.error(
'Failed to set {!s} feature: {!s}'.format(feature, e))
if not ignore_errors:
raise
try:
dst_vm.firewall.save_rules(src_vm.firewall.rules)
except qubesadmin.exc.QubesException as e:
self.log.error('Failed to set firewall: %s', e)
if not ignore_errors:
raise
try:
# FIXME: convert to qrexec calls to dom0/GUI VM
appmenus_cmd = \
['qvm-appmenus', '--init', '--update',
'--source', src_vm.name, dst_vm.name]
subprocess.check_output(appmenus_cmd, stderr=subprocess.STDOUT)
except OSError:
# this file needs to be python 2.7 compatible,
# so no FileNotFoundError
self.log.error('Failed to clone appmenus, qvm-appmenus missing')
if not ignore_errors:
raise qubesadmin.exc.QubesException(
'Failed to clone appmenus')
except subprocess.CalledProcessError as e:
self.log.error('Failed to clone appmenus: %s',
e.output.decode())
if not ignore_errors:
raise qubesadmin.exc.QubesException(
'Failed to clone appmenus')
except qubesadmin.exc.QubesException:
if not ignore_errors:
del self.domains[dst_vm.name]
raise
try:
for dst_volume in sorted(dst_vm.volumes.values()):
if not dst_volume.save_on_stop:
# clone only persistent volumes
continue
if ignore_volumes and dst_volume.name in ignore_volumes:
continue
src_volume = src_vm.volumes[dst_volume.name]
dst_vm.log.info('Cloning {} volume'.format(dst_volume.name))
dst_volume.clone(src_volume)
except qubesadmin.exc.QubesException:
del self.domains[dst_vm.name]
raise
if not ignore_devices:
try:
for devclass in src_vm.devices:
for assignment in src_vm.devices[devclass].assignments(
persistent=True):
new_assignment = qubesadmin.devices.DeviceAssignment(
backend_domain=assignment.backend_domain,
ident=assignment.ident,
options=assignment.options,
persistent=assignment.persistent)
dst_vm.devices[devclass].attach(new_assignment)
except qubesadmin.exc.QubesException:
if not ignore_errors:
del self.domains[dst_vm.name]
raise
return dst_vm
def qubesd_call(self, dest, method, arg=None, payload=None,
payload_stream=None):
"""
Execute Admin API method.
If `payload` and `payload_stream` are both specified, they will be sent
in that order.
:param dest: Destination VM name
:param method: Full API method name ('admin...')
:param arg: Method argument (if any)
:param payload: Payload send to the method
:param payload_stream: file-like object to read payload from
:return: Data returned by qubesd (string)
.. warning:: *payload_stream* will get closed by this function
"""
raise NotImplementedError(
'qubesd_call not implemented in QubesBase class; use specialized '
'class: qubesadmin.Qubes()')
def run_service(self, dest, service, filter_esc=False, user=None,
localcmd=None, wait=True, autostart=True, **kwargs):
"""Run qrexec service in a given destination
*kwargs* are passed verbatim to :py:meth:`subprocess.Popen`.
:param str dest: Destination - may be a VM name or empty
string for default (for a given service)
:param str service: service name
:param bool filter_esc: filter escape sequences to protect terminal \
emulator
:param str user: username to run service as
:param str localcmd: Command to connect stdin/stdout to
:param bool wait: Wait service run
:param bool autostart: Automatically start the target VM
:rtype: subprocess.Popen
"""
raise NotImplementedError(
'run_service not implemented in QubesBase class; use specialized '
'class: qubesadmin.Qubes()')
@staticmethod
def _call_with_stream(command, payload, payload_stream):
"""Helper method to pass data to qubesd. Calls a command with
payload and payload_stream as input.
:param command: command to run
:param payload: Initial payload, or None
:param payload_stream: File-like object with the rest of data
:return: (process, stdout, stderr)
"""
if payload:
# It's not strictly correct to write data to stdin in this way,
# because the process can get blocked on stdout or stderr pipe.
# However, in practice the output should be always smaller than 4K.
proc = subprocess.Popen(
command,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc.stdin.write(payload)
try:
shutil.copyfileobj(payload_stream, proc.stdin)
except BrokenPipeError:
# We might receive an error from qubesd before we sent
# everything (for instance, because we are sending too much
# data).
pass
else:
# Connect the stream directly.
proc = subprocess.Popen(
command,
stdin=payload_stream,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
payload_stream.close()
stdout, stderr = proc.communicate()
return proc, stdout, stderr
def _invalidate_cache(self, subject, event, name, **kwargs):
"""Invalidate cached value of a property.
This method is designed to be hooked as an event handler for:
- property-set:*
- property-del:*
This is done in :py:class:`qubesadmin.events.EventsDispatcher` class
directly, before calling other handlers.
It handles both VM and global properties.
Note: even if the new value is given in the event arguments, it is
ignored because it comes without type information.
:param subject: either VM object or None
:param event: name of the event
:param name: name of the property
:param kwargs: other arguments
:return: none
""" # pylint: disable=unused-argument
if subject is None:
subject = self
try:
# pylint: disable=protected-access
del subject._properties_cache[name]
except KeyError:
pass
class QubesLocal(QubesBase):
"""Application object communicating through local socket.
Used when running in dom0.
"""
qubesd_connection_type = 'socket'
def qubesd_call(self, dest, method, arg=None, payload=None,
payload_stream=None):
"""
Execute Admin API method.
If `payload` and `payload_stream` are both specified, they will be sent
in that order.
:param dest: Destination VM name
:param method: Full API method name ('admin...')
:param arg: Method argument (if any)
:param payload: Payload send to the method
:param payload_stream: file-like object to read payload from
:return: Data returned by qubesd (string)
.. warning:: *payload_stream* will get closed by this function
"""
if payload_stream:
# payload_stream can be used for large amount of data,
# so optimize for throughput, not latency: spawn actual qrexec
# service implementation, which may use some optimization there (
# see admin.vm.volume.Import - actual data handling is done with dd)
method_path = os.path.join(
qubesadmin.config.QREXEC_SERVICES_DIR, method)
if not os.path.exists(method_path):
raise qubesadmin.exc.QubesDaemonCommunicationError(
'{} not found'.format(method_path))
command = ['env', 'QREXEC_REMOTE_DOMAIN=dom0',
'QREXEC_REQUESTED_TARGET=' + dest, method_path, arg]
if os.getuid() != 0:
command.insert(0, 'sudo')
(_, stdout, _) = self._call_with_stream(
command, payload, payload_stream)
return self._parse_qubesd_response(stdout)
try:
client_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
client_socket.connect(qubesadmin.config.QUBESD_SOCKET)
except (IOError, OSError) as e:
raise qubesadmin.exc.QubesDaemonCommunicationError(
'Failed to connect to qubesd service: %s', str(e))
# src, method, dest, arg
for call_arg in ('dom0', method, dest, arg):
if call_arg is not None:
client_socket.sendall(call_arg.encode('ascii'))
client_socket.sendall(b'\0')
if payload is not None:
client_socket.sendall(payload)
client_socket.shutdown(socket.SHUT_WR)
return_data = client_socket.makefile('rb').read()
client_socket.close()
return self._parse_qubesd_response(return_data)
def run_service(self, dest, service, filter_esc=False, user=None,
localcmd=None, wait=True, autostart=True, **kwargs):
"""Run qrexec service in a given destination
:param str dest: Destination - may be a VM name or empty
string for default (for a given service)
:param str service: service name
:param bool filter_esc: filter escape sequences to protect terminal \
emulator
:param str user: username to run service as
:param str localcmd: Command to connect stdin/stdout to
:param bool wait: wait for remote process to finish
:rtype: subprocess.Popen
"""
if not dest:
raise ValueError('Empty destination name allowed only from a VM')
if not wait and localcmd:
raise ValueError('wait=False incompatible with localcmd')
if autostart:
try:
self.qubesd_call(dest, 'admin.vm.Start')
except qubesadmin.exc.QubesVMNotHaltedError:
pass
elif not self.domains.get_blind(dest).is_running():
raise qubesadmin.exc.QubesVMNotRunningError(
'%s is not running', dest)
qrexec_opts = ['-d', dest]
if filter_esc:
qrexec_opts.extend(['-t'])
if filter_esc or os.isatty(sys.stderr.fileno()):
qrexec_opts.extend(['-T'])
if localcmd:
qrexec_opts.extend(['-l', localcmd])
if user is None:
user = 'DEFAULT'
if not wait:
qrexec_opts.extend(['-e'])
if 'connect_timeout' in kwargs:
qrexec_opts.extend(['-w', str(kwargs.pop('connect_timeout'))])
kwargs.setdefault('stdin', subprocess.PIPE)
kwargs.setdefault('stdout', subprocess.PIPE)
kwargs.setdefault('stderr', subprocess.PIPE)
proc = subprocess.Popen(
[qubesadmin.config.QREXEC_CLIENT] + qrexec_opts + [
'{}:QUBESRPC {} dom0'.format(user, service)], **kwargs)
return proc
class QubesRemote(QubesBase):
"""Application object communicating through qrexec services.
Used when running in VM.
"""
qubesd_connection_type = 'qrexec'
def qubesd_call(self, dest, method, arg=None, payload=None,
payload_stream=None):
"""
Execute Admin API method.
If `payload` and `payload_stream` are both specified, they will be sent
in that order.
:param dest: Destination VM name
:param method: Full API method name ('admin...')
:param arg: Method argument (if any)
:param payload: Payload send to the method
:param payload_stream: file-like object to read payload from
:return: Data returned by qubesd (string)
.. warning:: *payload_stream* will get closed by this function
"""
service_name = method
if arg is not None:
service_name += '+' + arg
command = [qubesadmin.config.QREXEC_CLIENT_VM,
dest, service_name]
if payload_stream:
(p, stdout, stderr) = self._call_with_stream(
command, payload, payload_stream)
else:
p = subprocess.Popen(command,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(stdout, stderr) = p.communicate(payload)
if p.returncode != 0:
raise qubesadmin.exc.QubesDaemonNoResponseError(
'Service call error: %s', stderr.decode())
return self._parse_qubesd_response(stdout)
def run_service(self, dest, service, filter_esc=False, user=None,
localcmd=None, wait=True, autostart=True, **kwargs):
"""Run qrexec service in a given destination
:param str dest: Destination - may be a VM name or empty
string for default (for a given service)
:param str service: service name
:param bool filter_esc: filter escape sequences to protect terminal \
emulator
:param str user: username to run service as
:param str localcmd: Command to connect stdin/stdout to
:param bool wait: wait for process to finish
:rtype: subprocess.Popen
"""
if not autostart and not dest:
raise ValueError(
'autostart=False makes sense only with a defined target')
if user:
raise ValueError(
'non-default user not possible for calls from VM')
if not wait and localcmd:
raise ValueError('wait=False incompatible with localcmd')
qrexec_opts = []
if filter_esc:
qrexec_opts.extend(['-t'])
if filter_esc or (
os.isatty(sys.stderr.fileno()) and 'stderr' not in kwargs):
qrexec_opts.extend(['-T'])
if not autostart and not self.domains.get_blind(dest).is_running():
raise qubesadmin.exc.QubesVMNotRunningError(
'%s is not running', dest)
if not wait:
# qrexec-client-vm can only request service calls, which are
# started using MSG_EXEC_CMDLINE qrexec protocol message; this
# message means "start the process, pipe its stdin/out/err,
# and when it terminates, send exit code back".
# According to the protocol qrexec-client-vm needs to wait for
# MSG_DATA_EXIT_CODE, so implementing wait=False would require
# some protocol change (or protocol violation).
raise NotImplementedError(
'wait=False not implemented for calls from VM')
kwargs.setdefault('stdin', subprocess.PIPE)
kwargs.setdefault('stdout', subprocess.PIPE)
kwargs.setdefault('stderr', subprocess.PIPE)
proc = subprocess.Popen(
[qubesadmin.config.QREXEC_CLIENT_VM] +
qrexec_opts +
[dest or '', service] +
(shlex.split(localcmd) if localcmd else []),
**kwargs)
return proc