core-admin/qubes/vm/__init__.py

#
# The Qubes OS Project, https://www.qubes-os.org/
#
# Copyright (C) 2010-2015  Joanna Rutkowska <joanna@invisiblethingslab.com>
# Copyright (C) 2011-2015  Marek Marczykowski-Górecki
#                              <marmarek@invisiblethingslab.com>
# Copyright (C) 2014-2015  Wojtek Porczyk <woju@invisiblethingslab.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#

'''Qubes Virtual Machines

'''

import datetime
import os
import re
import subprocess
import sys
import xml.parsers.expat

import lxml.etree

import qubes
import qubes.devices
import qubes.events
import qubes.log
import qubes.tools.qvm_ls


def validate_name(holder, prop, value):
    ''' Check if value is syntactically correct VM name '''
    if not isinstance(value, str):
        raise TypeError('VM name must be string, {!r} found'.format(
            type(value).__name__))
    if len(value) > 31:
        if holder is not None and prop is not None:
            raise qubes.exc.QubesPropertyValueError(holder, prop, value,
                '{} value must be shorter than 32 characters'.format(
                    prop.__name__))
        else:
            raise qubes.exc.QubesValueError(
                'VM name must be shorter than 32 characters')

    # this regexp does not contain '+'; if it had it, we should specifically
    # disallow 'lost+found' #1440
    if re.match(r"^[a-zA-Z][a-zA-Z0-9_-]*$", value) is None:
        if holder is not None and prop is not None:
            raise qubes.exc.QubesPropertyValueError(holder, prop, value,
                '{} value contains illegal characters'.format(prop.__name__))
        else:
            raise qubes.exc.QubesValueError(
                'VM name contains illegal characters')


class Features(dict):
    '''Manager of the features.

    Features can have three distinct values: no value (not present in mapping,
    which is closest thing to :py:obj:`None`), empty string (which is
    interpreted as :py:obj:`False`) and non-empty string, which is
    :py:obj:`True`. Anything assigned to the mapping is coerced to strings,
    however if you assign instances of :py:class:`bool`, they are converted as
    described above. Be aware that assigning the number `0` (which is considered
    false in Python) will result in string `'0'`, which is considered true.

    This class inherits from dict, but has most of the methods that manipulate
    the item disarmed (they raise NotImplementedError). The ones that are left
    fire appropriate events on the qube that owns an instance of this class.
    '''

    #
    # Those are the methods that affect contents. Either disarm them or make
    # them report appropriate events. Good approach is to rewrite them carefully
    # using official documentation, but use only our (overloaded) methods.
    #
    def __init__(self, vm, other=None, **kwargs):
        super(Features, self).__init__()
        self.vm = vm
        self.update(other, **kwargs)

    def __delitem__(self, key):
        super(Features, self).__delitem__(key)
        self.vm.fire_event('domain-feature-delete', key=key)

    def __setitem__(self, key, value):
        if value is None or isinstance(value, bool):
            value = '1' if value else ''
        else:
            value = str(value)
        self.vm.fire_event('domain-feature-set', key=key, value=value)
        super(Features, self).__setitem__(key, value)

    def clear(self):
        for key in self:
            del self[key]

    def pop(self):
        '''Not implemented
        :raises: NotImplementedError
        '''
        raise NotImplementedError()

    def popitem(self):
        '''Not implemented
        :raises: NotImplementedError
        '''
        raise NotImplementedError()

    def setdefault(self):
        '''Not implemented
        :raises: NotImplementedError
        '''
        raise NotImplementedError()

    def update(self, other=None, **kwargs):
        if other is not None:
            if hasattr(other, 'keys'):
                for key in other:
                    self[key] = other[key]
            else:
                for key, value in other:
                    self[key] = value

        for key in kwargs:
            self[key] = kwargs[key]

    #
    # end of overriding
    #

    _NO_DEFAULT = object()

    def check_with_template(self, feature, default=_NO_DEFAULT):
        ''' Check if the vm's template has the specified feature. '''
        if feature in self:
            return self[feature]

        if hasattr(self.vm, 'template') and self.vm.template is not None:
            return self.vm.template.features.check_with_template(feature,
                default)

        if default is self._NO_DEFAULT:
            raise KeyError(feature)

        return default


class BaseVMMeta(qubes.events.EmitterMeta):
    '''Metaclass for :py:class:`.BaseVM`'''
    def __init__(cls, name, bases, dict_):
        super(BaseVMMeta, cls).__init__(name, bases, dict_)
        qubes.tools.qvm_ls.process_class(cls)


class BaseVM(qubes.PropertyHolder, metaclass=BaseVMMeta):
    '''Base class for all VMs

    :param app: Qubes application context
    :type app: :py:class:`qubes.Qubes`
    :param xml: xml node from which to deserialise
    :type xml: :py:class:`lxml.etree._Element` or :py:obj:`None`

    This class is responsible for serializing and deserialising machines and
    provides basic framework. It contains no management logic. For that, see
    :py:class:`qubes.vm.qubesvm.QubesVM`.
    '''
    # pylint: disable=no-member

    def __init__(self, app, xml, features=None, devices=None, tags=None,
            **kwargs):
        # pylint: disable=redefined-outer-name

        # self.app must be set before super().__init__, because some property
        # setters need working .app attribute
        #: mother :py:class:`qubes.Qubes` object
        self.app = app

        super(BaseVM, self).__init__(xml, **kwargs)

        #: dictionary of features of this qube
        self.features = Features(self, features)

        #: :py:class:`DeviceManager` object keeping devices that are attached to
        #: this domain
        self.devices = devices or qubes.devices.DeviceManager(self)

        #: user-specified tags
        self.tags = tags or {}

        #: logger instance for logging messages related to this VM
        self.log = None

        if hasattr(self, 'name'):
            self.init_log()

    def load_extras(self):
        # features
        for node in self.xml.xpath('./features/feature'):
            self.features[node.get('name')] = node.text

        # devices (pci, usb, ...)
        for parent in self.xml.xpath('./devices'):
            devclass = parent.get('class')
            for node in parent.xpath('./device'):
                device = self.devices[devclass].devclass(
                    self.app.domains[node.get('backend-domain')],
                    node.get('id')
                )
                self.devices[devclass].attach(device)

        # tags
        for node in self.xml.xpath('./tags/tag'):
            self.tags[node.get('name')] = node.text

        # SEE:1815 firewall, policy.

    def init_log(self):
        '''Initialise logger for this domain.'''
        self.log = qubes.log.get_vm_logger(self.name)

    def __xml__(self):
        element = lxml.etree.Element('domain')
        element.set('id', 'domain-' + str(self.qid))
        element.set('class', self.__class__.__name__)

        element.append(self.xml_properties())

        features = lxml.etree.Element('features')
        for feature in self.features:
            node = lxml.etree.Element('feature', name=feature)
            node.text = self.features[feature]
            features.append(node)
        element.append(features)

        for devclass in self.devices:
            devices = lxml.etree.Element('devices')
            devices.set('class', devclass)
            for device in self.devices[devclass].attached(persistent=True):
                node = lxml.etree.Element('device')
                node.set('backend-domain', device.backend_domain.name)
                node.set('id', device.ident)
                devices.append(node)
            element.append(devices)

        tags = lxml.etree.Element('tags')
        for tag in self.tags:
            node = lxml.etree.Element('tag', name=tag)
            node.text = self.tags[tag]
            tags.append(node)
        element.append(tags)

        return element

    def __repr__(self):
        proprepr = []
        for prop in self.property_list():
            try:
                proprepr.append('{}={!s}'.format(
                    prop.__name__, getattr(self, prop.__name__)))
            except AttributeError:
                continue

        return '<{} object at {:#x} {}>'.format(
            self.__class__.__name__, id(self), ' '.join(proprepr))

    #
    # xml serialising methods
    #

    def create_config_file(self, prepare_dvm=False):
        '''Create libvirt's XML domain config file

        :param bool prepare_dvm: If we are in the process of preparing \
            DisposableVM
        '''
        domain_config = self.app.env.select_template([
                'libvirt/xen/by-name/{}.xml'.format(self.name),
                'libvirt/xen-user.xml',
                'libvirt/xen-dist.xml',
                'libvirt/xen.xml',
            ]).render(vm=self, prepare_dvm=prepare_dvm)
        return domain_config


class VMProperty(qubes.property):
    '''Property that is referring to a VM

    :param type vmclass: class that returned VM is supposed to be instance of

    and all supported by :py:class:`property` with the exception of ``type`` \
        and ``setter``
    '''

    _none_value = ''

    def __init__(self, name, vmclass=BaseVM, allow_none=False,
            **kwargs):
        if 'type' in kwargs:
            raise TypeError(
                "'type' keyword parameter is unsupported in {}".format(
                    self.__class__.__name__))
        if 'setter' in kwargs:
            raise TypeError(
                "'setter' keyword parameter is unsupported in {}".format(
                    self.__class__.__name__))
        if not issubclass(vmclass, BaseVM):
            raise TypeError(
                "'vmclass' should specify a subclass of qubes.vm.BaseVM")

        super(VMProperty, self).__init__(name,
            saver=(lambda self_, prop, value:
                self._none_value if value is None else value.name),
            **kwargs)
        self.vmclass = vmclass
        self.allow_none = allow_none

    def __set__(self, instance, value):
        if value is self.__class__.DEFAULT:
            self.__delete__(instance)
            return

        if value == self._none_value:
            value = None
        if value is None:
            if self.allow_none:
                super(VMProperty, self).__set__(instance, value)
                return
            else:
                raise ValueError(
                    'Property {!r} does not allow setting to {!r}'.format(
                        self.__name__, value))

        app = instance if isinstance(instance, qubes.Qubes) else instance.app

        try:
            vm = app.domains[value]
        except KeyError:
            raise qubes.exc.QubesVMNotFoundError(value)

        if not isinstance(vm, self.vmclass):
            raise TypeError('wrong VM class: domains[{!r}] is of type {!s} '
                'and not {!s}'.format(value,
                    vm.__class__.__name__,
                    self.vmclass.__name__))

        super(VMProperty, self).__set__(instance, vm)

    def sanitize(self, *, untrusted_newvalue):
        try:
            untrusted_vmname = untrusted_newvalue.decode('ascii')
        except UnicodeDecodeError:
            raise qubes.exc.QubesValueError
        validate_name(None, self, untrusted_vmname)
        return untrusted_vmname