core-admin/qubes/__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 library 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 library 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 library; if not, see <https://www.gnu.org/licenses/>.
#

'''
Qubes OS

:copyright: © 2010-2015 Invisible Things Lab
'''

import builtins
import collections
import os
import os.path
import string

import lxml.etree
import qubes.config
import qubes.events
import qubes.exc

__author__ = 'Invisible Things Lab'
__license__ = 'GPLv2 or later'
__version__ = 'R3'


class Label(object):
    '''Label definition for virtual machines

    Label specifies colour of the padlock displayed next to VM's name.
    When this is a :py:class:`qubes.vm.dispvm.DispVM`, padlock is overlayed
    with recycling pictogram.

    :param int index: numeric identificator of label
    :param str color: colour specification as in HTML (``#abcdef``)
    :param str name: label's name like "red" or "green"
    '''

    def __init__(self, index, color, name):
        #: numeric identificator of label
        self.index = index

        #: colour specification as in HTML (``#abcdef``)
        self.color = color

        #: label's name like "red" or "green"
        self.name = name

        #: freedesktop icon name, suitable for use in
        #: :py:meth:`PyQt4.QtGui.QIcon.fromTheme`
        self.icon = 'appvm-' + name

        #: freedesktop icon name, suitable for use in
        #: :py:meth:`PyQt4.QtGui.QIcon.fromTheme` on DispVMs
        self.icon_dispvm = 'dispvm-' + name


    @classmethod
    def fromxml(cls, xml):
        '''Create label definition from XML node

        :param lxml.etree._Element xml: XML node reference
        :rtype: :py:class:`qubes.Label`
        '''

        index = int(xml.get('id').split('-', 1)[1])
        color = xml.get('color')
        name = xml.text

        return cls(index, color, name)


    def __xml__(self):
        element = lxml.etree.Element(
            'label', id='label-{}'.format(self.index), color=self.color)
        element.text = self.name
        return element

    def __str__(self):
        return self.name

    def __repr__(self):
        return '{}({!r}, {!r}, {!r})'.format(
            self.__class__.__name__,
            self.index,
            self.color,
            self.name)

    def __eq__(self, other):
        if isinstance(other, Label):
            return self.name == other.name
        return NotImplemented

    def __hash__(self):
        return hash(self.name)

    @builtins.property
    def icon_path(self):
        '''Icon path

        .. deprecated:: 2.0
           use :py:meth:`PyQt4.QtGui.QIcon.fromTheme` and :py:attr:`icon`
        '''
        return os.path.join(qubes.config.system_path['qubes_icon_dir'],
            self.icon) + ".png"


    @builtins.property
    def icon_path_dispvm(self):
        '''Icon path

        .. deprecated:: 2.0
           use :py:meth:`PyQt4.QtGui.QIcon.fromTheme` and :py:attr:`icon_dispvm`
        '''
        return os.path.join(qubes.config.system_path['qubes_icon_dir'],
            self.icon_dispvm) + ".png"


class property(object):  # pylint: disable=redefined-builtin,invalid-name
    '''Qubes property.

    This class holds one property that can be saved to and loaded from
    :file:`qubes.xml`. It is used for both global and per-VM properties.

    Property can be unset by ordinary ``del`` statement or assigning
    :py:attr:`DEFAULT` special value to it. After deletion (or before first
    assignment/load) attempting to read a property will get its default value
    or, when no default, py:class:`exceptions.AttributeError`.

    :param str name: name of the property
    :param collections.Callable setter: if not :py:obj:`None`, this is used to \
        initialise value; first parameter to the function is holder instance \
        and the second is value; this is called before ``type``
    :param collections.Callable saver: function to coerce value to something \
        readable by setter
    :param type type: if not :py:obj:`None`, value is coerced to this type
    :param object default: default value; if callable, will be called with \
        holder as first argument
    :param int load_stage: stage when property should be loaded (see \
        :py:class:`Qubes` for description of stages)
    :param int order: order of evaluation (bigger order values are later)
    :param bool clone: :py:meth:`PropertyHolder.clone_properties` will not \
        include this property by default if :py:obj:`False`
    :param str doc: docstring; this should be one paragraph of plain RST, no \
        sphinx-specific features

    Setters and savers have following signatures:

        .. :py:function:: setter(self, prop, value)
            :noindex:

            :param self: instance of object that is holding property
            :param prop: property object
            :param value: value being assigned

        .. :py:function:: saver(self, prop, value)
            :noindex:

            :param self: instance of object that is holding property
            :param prop: property object
            :param value: value being saved
            :rtype: str
            :raises property.DontSave: when property should not be saved at all

    '''

    #: Assigning this value to property means setting it to its default value.
    #: If property has no default value, this will unset it.
    DEFAULT = object()

    # internal use only
    _NO_DEFAULT = object()

    def __init__(self, name, setter=None, saver=None, type=None,
            default=_NO_DEFAULT, write_once=False, load_stage=2, order=0,
            save_via_ref=False, clone=True,
            doc=None):
        # pylint: disable=redefined-builtin
        self.__name__ = name
        self._setter = setter
        self._saver = saver if saver is not None else (
            lambda self, prop, value: str(value))
        self.type = type
        self._default = default
        self._write_once = write_once
        self.order = order
        self.load_stage = load_stage
        self.save_via_ref = save_via_ref
        self.clone = clone
        self.__doc__ = doc
        self._attr_name = '_qubesprop_' + name

    def __get__(self, instance, owner):
        if instance is None:
            return self

        # XXX this violates duck typing, shall we keep it?
        if not isinstance(instance, PropertyHolder):
            raise AttributeError('qubes.property should be used on '
                'qubes.PropertyHolder instances only')

        try:
            return getattr(instance, self._attr_name)

        except AttributeError:
            return self.get_default(instance)

    def get_default(self, instance):
        if self._default is self._NO_DEFAULT:
            raise AttributeError(
                'property {!r} have no default'.format(self.__name__))
        elif isinstance(self._default, collections.Callable):
            return self._default(instance)
        else:
            return self._default

    def __set__(self, instance, value):
        self._enforce_write_once(instance)

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

        try:
            oldvalue = getattr(instance, self.__name__)
            has_oldvalue = True
        except AttributeError:
            has_oldvalue = False

        if self._setter is not None:
            value = self._setter(instance, self, value)
        if self.type not in (None, type(value)):
            value = self.type(value)

        if has_oldvalue:
            instance.fire_event('property-pre-set:' + self.__name__,
                pre_event=True,
                name=self.__name__, newvalue=value, oldvalue=oldvalue)
        else:
            instance.fire_event('property-pre-set:' + self.__name__,
                pre_event=True,
                name=self.__name__, newvalue=value)

        instance._property_init(self, value)  # pylint: disable=protected-access

        if has_oldvalue:
            instance.fire_event('property-set:' + self.__name__,
                name=self.__name__, newvalue=value, oldvalue=oldvalue)
        else:
            instance.fire_event('property-set:' + self.__name__,
                name=self.__name__, newvalue=value)


    def __delete__(self, instance):
        self._enforce_write_once(instance)

        try:
            oldvalue = getattr(instance, self.__name__)
            has_oldvalue = True
        except AttributeError:
            has_oldvalue = False

        if has_oldvalue:
            instance.fire_event('property-pre-del:' + self.__name__,
                pre_event=True,
                name=self.__name__, oldvalue=oldvalue)
            try:
                delattr(instance, self._attr_name)
            except AttributeError:
                pass
            instance.fire_event('property-del:' + self.__name__,
                name=self.__name__, oldvalue=oldvalue)

        else:
            instance.fire_event('property-pre-del:' + self.__name__,
                pre_event=True,
                name=self.__name__)
            instance.fire_event('property-del:' + self.__name__,
                name=self.__name__)


    def __repr__(self):
        default = ' default={!r}'.format(self._default) \
            if self._default is not self._NO_DEFAULT \
            else ''
        return '<{} object at {:#x} name={!r}{}>'.format(
            self.__class__.__name__, id(self), self.__name__, default)

    def __str__(self):
        return self.__name__

    def __hash__(self):
        return hash(self.__name__)

    def __lt__(self, other):
        if isinstance(other, property):
            return (self.load_stage, self.order, self.__name__) <\
                   (other.load_stage, other.order, other.__name__)
        return NotImplemented

    def __eq__(self, other):
        if isinstance(other, str):
            return self.__name__ == other
        return isinstance(other, property) and self.__name__ == other.__name__


    def _enforce_write_once(self, instance):
        if self._write_once and not instance.property_is_default(self):
            raise AttributeError(
                'property {!r} is write-once and already set'.format(
                    self.__name__))

    def sanitize(self, *, untrusted_newvalue):
        '''Coarse sanitization of value to be set, before sending it to a
        setter. Can raise QubesValueError if the value is invalid.

        :param untrusted_newvalue: value to be validated
        :return: sanitized value
        :raises: qubes.exc.QubesValueError
        '''
        # do not treat type='str' as sufficient validation
        if self.type is not None and self.type is not str:
            # assume specific type will preform enough validation
            try:
                untrusted_newvalue = untrusted_newvalue.decode('ascii',
                    errors='strict')
            except UnicodeDecodeError:
                raise qubes.exc.QubesValueError
            if self.type is bool:
                return self.bool(None, None, untrusted_newvalue)
            else:
                try:
                    return self.type(untrusted_newvalue)
                except ValueError:
                    raise qubes.exc.QubesValueError
        else:
            # 'str' or not specified type
            try:
                untrusted_newvalue = untrusted_newvalue.decode('ascii',
                    errors='strict')
            except UnicodeDecodeError:
                raise qubes.exc.QubesValueError
            allowed_set = string.printable
            if not all(x in allowed_set for x in untrusted_newvalue):
                raise qubes.exc.QubesValueError(
                    'Invalid characters in property value')
            return untrusted_newvalue


    #
    # exceptions
    #

    class DontSave(Exception):
        '''This exception may be raised from saver to sign that property should
        not be saved.
        '''
        pass

    @staticmethod
    def dontsave(self, prop, value):
        '''Dummy saver that never saves anything.'''
        # pylint: disable=bad-staticmethod-argument,unused-argument
        raise property.DontSave()

    #
    # some setters provided
    #

    @staticmethod
    def forbidden(self, prop, value):
        '''Property setter that forbids loading a property.

        This is used to effectively disable property in classes which inherit
        unwanted property. When someone attempts to load such a property, it

        :throws AttributeError: always
        ''' # pylint: disable=bad-staticmethod-argument,unused-argument

        raise AttributeError(
            'setting {} property on {} instance is forbidden'.format(
                prop.__name__, self.__class__.__name__))


    @staticmethod
    def bool(self, prop, value):
        '''Property setter for boolean properties.

        It accepts (case-insensitive) ``'0'``, ``'no'`` and ``false`` as
        :py:obj:`False` and ``'1'``, ``'yes'`` and ``'true'`` as
        :py:obj:`True`.
        ''' # pylint: disable=bad-staticmethod-argument,unused-argument

        if isinstance(value, str):
            lcvalue = value.lower()
            if lcvalue in ('0', 'no', 'false', 'off'):
                return False
            if lcvalue in ('1', 'yes', 'true', 'on'):
                return True
            raise qubes.exc.QubesValueError(
                'Invalid literal for boolean property: {!r}'.format(value))

        return bool(value)


def stateless_property(func):
    '''Decorator similar to :py:class:`builtins.property`, but for properties
    exposed through management API (including qvm-prefs etc)'''
    return property(func.__name__,
        setter=property.forbidden,
        saver=property.DontSave,
        default=func,
        doc=func.__doc__)


class PropertyHolder(qubes.events.Emitter):
    '''Abstract class for holding :py:class:`qubes.property`

    Events fired by instances of this class:

        .. event:: property-load (subject, event)

            Fired once after all properties are loaded from XML. Individual
            ``property-set`` events are not fired.

        .. event:: property-set:<propname> \
                (subject, event, name, newvalue[, oldvalue])

            Fired when property changes state. Signature is variable,
            *oldvalue* is present only if there was an old value.

            :param name: Property name
            :param newvalue: New value of the property
            :param oldvalue: Old value of the property

        .. event:: property-pre-set:<propname> \
                (subject, event, name, newvalue[, oldvalue])

            Fired before property changes state. Signature is variable,
            *oldvalue* is present only if there was an old value.

            :param name: Property name
            :param newvalue: New value of the property
            :param oldvalue: Old value of the property

        .. event:: property-del:<propname> \
                (subject, event, name[, oldvalue])

            Fired when property gets deleted (is set to default). Signature is
            variable, *oldvalue* is present only if there was an old value.

            :param name: Property name
            :param oldvalue: Old value of the property

        .. event:: property-pre-del:<propname> \
                (subject, event, name[, oldvalue])

            Fired before property gets deleted (is set to default). Signature
            is variable, *oldvalue* is present only if there was an old value.

            :param name: Property name
            :param oldvalue: Old value of the property

        .. event:: clone-properties (subject, event, src, proplist)

            :param src: object, from which we are cloning
            :param proplist: list of properties

    Members:
    '''

    def __init__(self, xml, **kwargs):
        self.xml = xml

        propvalues = {}

        all_names = set(prop.__name__ for prop in self.property_list())
        for key in list(kwargs):
            if not key in all_names:
                continue
            propvalues[key] = kwargs.pop(key)

        super(PropertyHolder, self).__init__(**kwargs)

        for key, value in propvalues.items():
            setattr(self, key, value)

        if self.xml is not None:
            # check if properties are appropriate
            all_names = set(prop.__name__ for prop in self.property_list())

            for node in self.xml.xpath('./properties/property'):
                name = node.get('name')
                if name not in all_names:
                    raise TypeError(
                        'property {!r} not applicable to {!r}'.format(
                            name, self.__class__.__name__))

    @classmethod
    def property_list(cls, load_stage=None):
        '''List all properties attached to this VM's class

        :param load_stage: Filter by load stage
        :type load_stage: :py:func:`int` or :py:obj:`None`
        '''

        props = set()
        for class_ in cls.__mro__:
            props.update(prop for prop in class_.__dict__.values()
                if isinstance(prop, property))
        if load_stage is not None:
            props = set(prop for prop in props
                if prop.load_stage == load_stage)
        return sorted(props)

    def _property_init(self, prop, value):
        '''Initialise property to a given value, without side effects.

        :param qubes.property prop: property object of particular interest
        :param value: value
        '''

        # pylint: disable=protected-access
        setattr(self, self.property_get_def(prop)._attr_name, value)


    def property_is_default(self, prop):
        '''Check whether property is in it's default value.

        Properties when unset may return some default value, so
        ``hasattr(vm, prop.__name__)`` is wrong in some circumstances. This
        method allows for checking if the value returned is in fact it's
        default value.

        :param qubes.property prop: property object of particular interest
        :rtype: bool
        ''' # pylint: disable=protected-access

        # both property_get_def() and ._attr_name may throw AttributeError,
        # which we don't want to catch
        attrname = self.property_get_def(prop)._attr_name
        return not hasattr(self, attrname)

    def property_get_default(self, prop):
        '''Get property default value.

        :param qubes.property or str prop: property object of particular
        interest
        '''

        return self.property_get_def(prop).get_default(self)


    @classmethod
    def property_get_def(cls, prop):
        '''Return property definition object.

        If prop is already :py:class:`qubes.property` instance, return the same
        object.

        :param prop: property object or name
        :type prop: qubes.property or str
        :rtype: qubes.property
        '''

        if isinstance(prop, qubes.property):
            return prop

        for p in cls.property_list():
            if p.__name__ == prop:
                return p

        raise AttributeError('No property {!r} found in {!r}'.format(
            prop, cls))


    def load_properties(self, load_stage=None):
        '''Load properties from immediate children of XML node.

        ``property-set`` events are not fired for each individual property.

        :param int load_stage: Stage of loading.
        '''

        if self.xml is None:
            return
        all_names = set(
            prop.__name__ for prop in self.property_list(load_stage))
        for node in self.xml.xpath('./properties/property'):
            name = node.get('name')
            value = node.get('ref') or node.text

            if not name in all_names:
                continue

            setattr(self, name, value)


    def xml_properties(self, with_defaults=False):
        '''Iterator that yields XML nodes representing set properties.

        :param bool with_defaults: If :py:obj:`True`, then it also includes \
            properties which were not set explicite, but have default values \
            filled.
        '''


        properties = lxml.etree.Element('properties')

        for prop in self.property_list():
            # pylint: disable=protected-access
            try:
                value = getattr(
                    self, (prop.__name__ if with_defaults else prop._attr_name))
            except AttributeError:
                continue

            try:
                value = prop._saver(self, prop, value)
            except property.DontSave:
                continue

            element = lxml.etree.Element('property', name=prop.__name__)
            if prop.save_via_ref:
                element.set('ref', value)
            else:
                element.text = value
            properties.append(element)

        return properties


    # this was clone_attrs
    def clone_properties(self, src, proplist=None):
        '''Clone properties from other object.

        :param PropertyHolder src: source object
        :param iterable proplist: list of properties \
            (:py:obj:`None` or omit for all properties except those with \
            :py:attr:`property.clone` set to :py:obj:`False`)
        '''

        if proplist is None:
            proplist = [prop for prop in self.property_list()
                if prop.clone]
        else:
            proplist = [prop for prop in self.property_list()
                if prop.__name__ in proplist or prop in proplist]

        for prop in proplist:
            try:
                # pylint: disable=protected-access
                self._property_init(prop, getattr(src, prop._attr_name))
            except AttributeError:
                continue

        self.fire_event('clone-properties', src=src, proplist=proplist)


    def property_require(self, prop, allow_none=False, hard=False):
        '''Complain badly when property is not set.

        :param prop: property name or object
        :type prop: qubes.property or str
        :param bool allow_none: if :py:obj:`True`, don't complain if \
            :py:obj:`None` is found
        :param bool hard: if :py:obj:`True`, raise :py:class:`AssertionError`; \
            if :py:obj:`False`, log warning instead
        '''

        if isinstance(prop, qubes.property):
            prop = prop.__name__

        try:
            value = getattr(self, prop)
            if value is None and not allow_none:
                raise AttributeError()
        except AttributeError:
            # pylint: disable=no-member
            msg = 'Required property {!r} not set on {!r}'.format(prop, self)
            if hard:
                raise AssertionError(msg)
            else:
                # pylint: disable=no-member
                self.log.fatal(msg)


    def close(self):
        super().close()

        # Remove all properties -- somewhere in them there are cyclic
        # references. This just removes all the properties, just in case.
        # They are removed directly, bypassing write_once.
        for prop in self.property_list():
            # pylint: disable=protected-access
            try:
                delattr(self, prop._attr_name)
            except AttributeError:
                pass


# pylint: disable=wrong-import-position
from qubes.vm import VMProperty
from qubes.app import Qubes

__all__ = [
    'Label',
    'PropertyHolder',
    'Qubes',
    'VMProperty',
    'property',
]