core-admin/qubes/vm/mix/net.py

#
# The Qubes OS Project, https://www.qubes-os.org/
#
# Copyright (C) 2010-2016  Joanna Rutkowska <joanna@invisiblethingslab.com>
# Copyright (C) 2013-2016  Marek Marczykowski-Górecki
#                              <marmarek@invisiblethingslab.com>
# Copyright (C) 2014-2016  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.
#

''' This module contains the NetVMMixin '''

import os
import re

import libvirt  # pylint: disable=import-error
import qubes
import qubes.events
import qubes.firewall
import qubes.exc


def _setter_mac(self, prop, value):
    ''' Helper for setting the MAC address '''
    # pylint: disable=unused-argument
    if not isinstance(value, str):
        raise ValueError('MAC address must be a string')
    value = value.lower()
    if re.match(r"^([0-9a-f][0-9a-f]:){5}[0-9a-f][0-9a-f]$", value) is None:
        raise ValueError('Invalid MAC address value')
    return value


def _default_ip(self):
    if not self.is_networked():
        return None
    if self.netvm is not None:
        return self.netvm.get_ip_for_vm(self)  # pylint: disable=no-member

    return self.get_ip_for_vm(self)


def _setter_ip(self, prop, value):
    # pylint: disable=unused-argument
    if not isinstance(value, str):
        raise ValueError('IP address must be a string')
    value = value.lower()
    if re.match(r"^([0-9]{1,3}.){3}[0-9]{1,3}$", value) is None:
        raise ValueError('Invalid IP address value')
    return value


def _setter_netvm(self, prop, value):
    # pylint: disable=unused-argument
    if value is None:
        return
    if not value.provides_network:
        raise qubes.exc.QubesValueError(
            'The {!s} qube does not provide network'.format(value))

    if value is self \
            or value in self.app.domains.get_vms_connected_to(self):
        raise qubes.exc.QubesValueError(
            'Loops in network are unsupported')
    return value


class NetVMMixin(qubes.events.Emitter):
    ''' Mixin containing network functionality '''
    mac = qubes.property('mac', type=str,
        default='00:16:3E:5E:6C:00',
        setter=_setter_mac,
        doc='MAC address of the NIC emulated inside VM')

    ip = qubes.property('ip', type=str,
        default=_default_ip,
        setter=_setter_ip,
        doc='IP address of this domain.')

    # CORE2: swallowed uses_default_netvm
    netvm = qubes.VMProperty('netvm', load_stage=4, allow_none=True,
        default=(lambda self: self.app.default_fw_netvm if self.provides_network
            else self.app.default_netvm),
        setter=_setter_netvm,
        doc='''VM that provides network connection to this domain. When
            `None`, machine is disconnected. When absent, domain uses default
            NetVM.''')

    provides_network = qubes.property('provides_network', default=False,
        type=bool, setter=qubes.property.bool,
        doc='''If this domain can act as network provider (formerly known as
            NetVM or ProxyVM)''')


    @property
    def firewall_conf(self):
        return 'firewall.xml'

    #
    # used in networked appvms or proxyvms (netvm is not None)
    #


    @qubes.stateless_property
    def visible_ip(self):
        '''IP address of this domain as seen by the domain.'''
        return self.features.check_with_template('net/fake-ip', None) or \
            self.ip

    @qubes.stateless_property
    def visible_gateway(self):
        '''Default gateway of this domain as seen by the domain.'''
        return self.features.check_with_template('net/fake-gateway', None) or \
            self.netvm.gateway

    @qubes.stateless_property
    def visible_netmask(self):
        '''Netmask as seen by the domain.'''
        return self.features.check_with_template('net/fake-netmask', None) or \
            self.netvm.netmask

    #
    # used in netvms (provides_network=True)
    # those properties and methods are most likely accessed as vm.netvm.<prop>
    #

    @staticmethod
    def get_ip_for_vm(vm):
        '''Get IP address for (appvm) domain connected to this (netvm) domain.
        '''
        import qubes.vm.dispvm  # pylint: disable=redefined-outer-name
        if isinstance(vm, qubes.vm.dispvm.DispVM):
            return '10.138.{}.{}'.format((vm.dispid >> 8) & 0xff,
                vm.dispid & 0xff)

        # VM technically can get address which ends in '.0'. This currently
        # does not happen, because qid < 253, but may happen in the future.
        return '10.137.{}.{}'.format((vm.qid >> 8) & 0xff, vm.qid & 0xff)

    @qubes.stateless_property
    def gateway(self):
        '''Gateway for other domains that use this domain as netvm.'''
        return self.visible_ip if self.provides_network else None

    @property
    def netmask(self):
        '''Netmask for gateway address.'''
        return '255.255.255.255' if self.is_networked() else None

    @property
    def connected_vms(self):
        ''' Return a generator containing all domains connected to the current
            NetVM.
        '''
        for vm in self.app.domains:
            if vm.netvm is self:
                yield vm

    #
    # used in both
    #

    @property
    def dns(self):
        '''Secondary DNS server set up for this domain.'''
        if self.netvm is not None or self.provides_network:
            return (
                '10.139.1.1',
                '10.139.1.2',
            )

        return None

    def __init__(self, *args, **kwargs):
        self._firewall = None
        super(NetVMMixin, self).__init__(*args, **kwargs)

    @qubes.events.handler('domain-start')
    def on_domain_started(self, event, **kwargs):
        '''Connect this domain to its downstream domains. Also reload firewall
        in its netvm.

        This is needed when starting netvm *after* its connected domains.
        '''  # pylint: disable=unused-argument

        if self.netvm:
            self.netvm.reload_firewall_for_vm(self)  # pylint: disable=no-member

        for vm in self.connected_vms:
            if not vm.is_running():
                continue
            vm.log.info('Attaching network')
            # SEE: 1426
            vm.cleanup_vifs()

            try:
                # 1426
                vm.run('modprobe -r xen-netfront xennet',
                    user='root', wait=True)
            except:  # pylint: disable=bare-except
                pass

            try:
                vm.attach_network()
            except qubes.exc.QubesException:
                vm.log.warning('Cannot attach network', exc_info=1)

    @qubes.events.handler('domain-pre-shutdown')
    def shutdown_net(self, event, force=False):
        ''' Checks before NetVM shutdown if any connected domains are running.
            If `force` is `True` tries to detach network interfaces of connected
            vms
        '''  # pylint: disable=unused-argument

        connected_vms = [vm for vm in self.connected_vms if vm.is_running()]
        if connected_vms and not force:
            raise qubes.exc.QubesVMError(self,
                'There are other VMs connected to this VM: {}'.format(
                    ', '.join(vm.name for vm in connected_vms)))

        # SEE: 1426
        # detach network interfaces of connected VMs before shutting down,
        # otherwise libvirt will not notice it and will try to detach them
        # again (which would fail, obviously).
        # This code can be removed when #1426 got implemented
        for vm in connected_vms:
            if vm.is_running():
                try:
                    vm.detach_network()
                except (qubes.exc.QubesException, libvirt.libvirtError):
                    # ignore errors
                    pass

    def attach_network(self):
        '''Attach network in this machine to it's netvm.'''

        if not self.is_running():
            raise qubes.exc.QubesVMNotRunningError(self)
        assert self.netvm is not None

        if not self.netvm.is_running():  # pylint: disable=no-member
            # pylint: disable=no-member
            self.log.info('Starting NetVM ({0})'.format(self.netvm.name))
            self.netvm.start()

        self.netvm.set_mapped_ip_info_for_vm(self)
        self.libvirt_domain.attachDevice(
            self.app.env.get_template('libvirt/devices/net.xml').render(
                vm=self))

    def detach_network(self):
        '''Detach machine from it's netvm'''

        if not self.is_running():
            raise qubes.exc.QubesVMNotRunningError(self)
        assert self.netvm is not None

        self.libvirt_domain.detachDevice(
            self.app.env.get_template('libvirt/devices/net.xml').render(
                vm=self))

    def is_networked(self):
        '''Check whether this VM can reach network (firewall notwithstanding).

        :returns: :py:obj:`True` if is machine can reach network, \
            :py:obj:`False` otherwise.
        :rtype: bool
        '''

        if self.provides_network:
            return True

        return self.netvm is not None

    def cleanup_vifs(self):
        '''Remove stale network device backends.

        Libvirt does not remove vif when backend domain is down, so we must do
        it manually. This method is one big hack for #1426.
        '''

        dev_basepath = '/local/domain/%d/device/vif' % self.xid
        for dev in self.app.vmm.xs.ls('', dev_basepath) or []:
            # check if backend domain is alive
            backend_xid = int(self.app.vmm.xs.read('',
                '{}/{}/backend-id'.format(dev_basepath, dev)))
            if backend_xid in self.app.vmm.libvirt_conn.listDomainsID():
                # check if device is still active
                if self.app.vmm.xs.read('',
                        '{}/{}/state'.format(dev_basepath, dev)) == '4':
                    continue
            # remove dead device
            self.app.vmm.xs.rm('', '{}/{}'.format(dev_basepath, dev))

    def reload_firewall_for_vm(self, vm):
        ''' Reload the firewall rules for the vm '''
        if not self.is_running():
            return

        base_dir = '/qubes-firewall/' + vm.ip + '/'
        # remove old entries if any (but don't touch base empty entry - it
        # would trigger reload right away
        self.qdb.rm(base_dir)
        # write new rules
        for key, value in vm.firewall.qdb_entries(addr_family=4).items():
            self.qdb.write(base_dir + key, value)
        # signal its done
        self.qdb.write(base_dir[:-1], '')

    def set_mapped_ip_info_for_vm(self, vm):
        '''
        Set configuration to possibly hide real IP from the VM.
        This needs to be done before executing 'script'
        (`/etc/xen/scripts/vif-route-qubes`) in network providing VM
        '''
        # add info about remapped IPs (VM IP hidden from the VM itself)
        mapped_ip_base = '/mapped-ip/{}'.format(vm.ip)
        if vm.visible_ip:
            self.qdb.write(mapped_ip_base + '/visible-ip', vm.visible_ip)
        else:
            self.qdb.rm(mapped_ip_base + '/visible-ip')
        if vm.visible_gateway:
            self.qdb.write(mapped_ip_base + '/visible-gateway',
                vm.visible_gateway)
        else:
            self.qdb.rm(mapped_ip_base + '/visible-gateway')


    @qubes.events.handler('property-del:netvm')
    def on_property_del_netvm(self, event, name, oldvalue=None):
        ''' Sets the the NetVM to default NetVM '''
        # pylint: disable=unused-argument
        # we are changing to default netvm
        newvalue = self.netvm
        if newvalue == oldvalue:
            return
        self.fire_event('property-set:netvm',
            name='netvm', newvalue=newvalue, oldvalue=oldvalue)

    @qubes.events.handler('property-pre-set:netvm')
    def on_property_pre_set_netvm(self, event, name, newvalue, oldvalue=None):
        ''' Run sanity checks before setting a new NetVM '''
        # pylint: disable=unused-argument
        if newvalue is not None:
            if not self.app.vmm.offline_mode \
                    and self.is_running() and not newvalue.is_running():
                raise qubes.exc.QubesVMNotStartedError(newvalue,
                    'Cannot dynamically attach to stopped NetVM: {!r}'.format(
                        newvalue))

        if oldvalue is not None:
            if self.is_running():
                self.detach_network()

    @qubes.events.handler('property-set:netvm')
    def on_property_set_netvm(self, event, name, newvalue, oldvalue=None):
        ''' Replaces the current NetVM with a new one and fires
            net-domain-connect event
        '''
        # pylint: disable=unused-argument

        if newvalue is None:
            return

        if self.is_running():
            # refresh IP, DNS etc
            self.create_qdb_entries()
            self.attach_network()

            newvalue.fire_event('net-domain-connect', vm=self)

    @qubes.events.handler('net-domain-connect')
    def on_net_domain_connect(self, event, vm):
        ''' Reloads the firewall config for vm '''
        # pylint: disable=unused-argument
        self.reload_firewall_for_vm(vm)

    @qubes.events.handler('domain-qdb-create')
    def on_domain_qdb_create(self, event):
        ''' Fills the QubesDB with firewall entries. Not implemented '''
        # SEE: 1815 fill firewall QubesDB entries
        pass

    @qubes.events.handler('firewall-changed', 'domain-spawn')
    def on_firewall_changed(self, event, **kwargs):
        ''' Reloads the firewall if vm is running and has a NetVM assigned '''
        # pylint: disable=unused-argument
        if self.is_running() and self.netvm:
            self.netvm.set_mapped_ip_info_for_vm(self)
            self.netvm.reload_firewall_for_vm(self)  # pylint: disable=no-member

    # CORE2: swallowed get_firewall_conf, write_firewall_conf,
    # get_firewall_defaults
    @property
    def firewall(self):
        if self._firewall is None:
            self._firewall = qubes.firewall.Firewall(self)
        return self._firewall

    def has_firewall(self):
        ''' Return `True` if there are some vm specific firewall rules set '''
        return os.path.exists(os.path.join(self.dir_path, self.firewall_conf))