core-admin/qubes/storage/xen.py

#!/usr/bin/python2 -O
# vim: fileencoding=utf-8

#
# The Qubes OS Project, https://www.qubes-os.org/
#
# Copyright (C) 2015  Joanna Rutkowska <joanna@invisiblethingslab.com>
# Copyright (C) 2013-2015  Marek Marczykowski-Górecki
#                              <marmarek@invisiblethingslab.com>
# Copyright (C) 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.
#

from __future__ import absolute_import

import os
import os.path
import re
import subprocess

import lxml.etree

import qubes
import qubes.config
import qubes.storage
import qubes.vm.templatevm


class XenStorage(qubes.storage.Storage):
    '''Class for VM storage of Xen VMs.
    '''

    root_dev = 'xvda'
    private_dev = 'xvdb'
    volatile_dev = 'xvdc'
    modules_dev = 'xvdd'

    def __init__(self, vm, vmdir, **kwargs):
        """ Instantiate the storage.

            Args:
                vm: a QubesVM
                vmdir: the root directory of the pool
        """
        assert vm is not None
        assert vmdir is not None

        super(XenStorage, self).__init__(vm, **kwargs)

        self.vmdir = vmdir


    @property
    def private_img(self):
        '''Path to the private image'''
        return self.abspath(qubes.config.vm_files['private_img'])


    @property
    def root_img(self):
        '''Path to the root image'''
        return self.vm.template.root_img if hasattr(self.vm, 'template') \
            else self.abspath(qubes.config.vm_files['root_img'])


    @property
    def rootcow_img(self):
        '''Path to the root COW image'''

        if isinstance(self.vm, qubes.vm.templatevm.TemplateVM):
            return self.abspath(qubes.config.vm_files['rootcow_img'])

        return None


    @property
    def volatile_img(self):
        '''Path to the volatile image'''
        return self.abspath(qubes.config.vm_files['volatile_img'])


    # pylint: disable=redefined-builtin
    @staticmethod
    def format_disk_dev(path, vdev, script=None, rw=True, type='disk',
            domain=None):
        if path is None:
            return ''

        element = lxml.etree.Element('disk')
        element.set('type', 'block')
        element.set('device', type)

        element.append(lxml.etree.Element('driver', name='phy'))
        element.append(lxml.etree.Element('source', dev=path))
        element.append(lxml.etree.Element('target', dev=vdev))

        if not rw:
            element.append(lxml.etree.Element('readonly'))
        if domain is not None:
            # XXX vm.name?
            element.append(lxml.etree.Element('domain', name=domain))
        if script:
            element.append(lxml.etree.Element('script', path=script))

        # TODO return element
        return lxml.etree.tostring(element)


    def root_dev_config(self):
        if isinstance(self.vm, qubes.vm.templatevm.TemplateVM):
            return self.format_disk_dev(
                '{root}:{rootcow}'.format(
                    root=self.root_img,
                    rootcow=self.rootcow_img),
                self.root_dev,
                script='block-origin')

        elif self.vm.hvm and hasattr(self.vm, 'template'):
            # HVM template-based VM - only one device-mapper layer, in dom0
            # (root+volatile)
            # HVM detection based on 'kernel' property is massive hack,
            # but taken from assumption that VM needs Qubes-specific kernel
            # (actually initramfs) to assemble the second layer of device-mapper
            return self.format_disk_dev(
                '{root}:{volatile}'.format(
                    root=self.vm.template.storage.root_img,
                    volatile=self.volatile_img),
                self.root_dev,
                script='block-snapshot')

        elif hasattr(self.vm, 'template'):
            # any other template-based VM - two device-mapper layers: one
            # in dom0 (here) from root+root-cow, and another one from
            # this+volatile.img
            return self.format_disk_dev(
                '{root}:{template_rootcow}'.format(
                    root=self.root_img,
                    template_rootcow=self.vm.template.storage.rootcow_img),
                self.root_dev,
                script='block-snapshot',
                rw=False)

        else:
            # standalone qube
            return self.format_disk_dev(self.root_img, self.root_dev)


    def private_dev_config(self):
        self.format_disk_dev(self.private_img, self.private_dev)

    def volatile_dev_config(self):
        self.format_disk_dev(self.volatile_img, self.volatile_dev)


    def create_on_disk_private_img(self, source_template=None):
        if source_template is None:
            f_private = open(self.private_img, 'a+b')
            f_private.truncate(self.private_img_size)
            f_private.close()

        else:
            self.vm.log.info("Copying the template's private image: {}".format(
                source_template.private_img))
            self._copy_file(source_template.private_img, self.private_img)


    def create_on_disk_root_img(self, source_template=None):
        if source_template is None:
            fd = open(self.root_img, 'a+b')
            fd.truncate(self.root_img_size)
            fd.close()

        elif self.vm.updateable:
            # if not updateable, just use template's disk
            self.vm.log.info("--> Copying the template's root image: {}".format(
                source_template.root_img))
            self._copy_file(source_template.root_img, self.root_img)


    def resize_private_img(self, size):
        fd = open(self.private_img, 'a+b')
        fd.truncate(size)
        fd.close()

        # find loop device if any
        p = subprocess.Popen(
            ['sudo', 'losetup', '--associated', self.private_img],
            stdout=subprocess.PIPE)
        result = p.communicate()

        m = re.match(r'^(/dev/loop\d+):\s', result[0])
        if m is not None:
            loop_dev = m.group(1)

            # resize loop device
            subprocess.check_call(
                ['sudo', 'losetup', '--set-capacity', loop_dev])


    def commit_template_changes(self):
        assert isinstance(self.vm, qubes.vm.templatevm.TemplateVM)

        # TODO: move rootcow_img to this class; the same for vm.is_outdated()
        if os.path.exists(self.vm.rootcow_img):
            os.rename(self.vm.rootcow_img, self.vm.rootcow_img + '.old')

        old_umask = os.umask(002)
        f_cow = open(self.vm.rootcow_img, 'w')
        f_root = open(self.root_img, 'r')
        f_root.seek(0, os.SEEK_END)
        # make empty sparse file of the same size as root.img
        f_cow.truncate(f_root.tell())
        f_cow.close()
        f_root.close()
        os.umask(old_umask)


    def reset_volatile_storage(self, source_template=None):
        if source_template is None:
            source_template = self.vm.template

        if source_template is not None:
            # template-based VM with only one device-mapper layer -
            # volatile.img used as upper layer on root.img, no root-cow.img
            # intermediate layer

            # XXX marmarek says this is either always true or always false;
            # rootcow_img got smashed in 35cb82 (#1573)
            # this may have remain after HVM check
            # this probably should have happen anyway
            if not source_template.storage.rootcow_img:
                if os.path.exists(self.volatile_img):
                    if self.vm.debug:
                        if os.path.getmtime(source_template.storage.root_img) \
                                > os.path.getmtime(self.volatile_img):
                            self.vm.log.warning(
                                'Template have changed, resetting root.img')
                        else:
                            self.vm.log.warning(
                                'Debug mode: not resetting root.img; if you'
                                ' want to force root.img reset, either'
                                ' update template VM, or remove volatile.img'
                                ' file.')
                            return

                    os.remove(self.volatile_img)

                # FIXME stat on f_root; with open() ...
                f_volatile = open(self.volatile_img, "w")
                f_root = open(source_template.storage.root_img, "r")
                f_root.seek(0, os.SEEK_END)
                f_volatile.truncate(f_root.tell()) # make empty sparse file of the same size as root.img
                f_volatile.close()
                f_root.close()
                return # XXX why is that? super() does not run

        super(XenStorage, self).reset_volatile_storage(
            source_template=source_template)


    def prepare_for_vm_startup(self):
        super(XenStorage, self).prepare_for_vm_startup()

        if self.drive is not None:
            (drive_type, drive_domain, drive_path) = self.drive.split(":")

            if drive_domain.lower() != "dom0":
                # XXX "VM '{}' holding '{}' does not exists".format(
                drive_vm = self.vm.app.domains[drive_domain]

                if not drive_vm.is_running():
                    raise qubes.exc.QubesVMNotRunningError(drive_vm,
                        'VM {!r} holding {!r} isn\'t running'.format(
                            drive_domain, drive_path))

        if self.rootcow_img and not os.path.exists(self.rootcow_img):
            self.commit_template_changes()

class XenPool(qubes.storage.Pool):
    def get_storage(self):
        """ Returns an instantiated ``XenStorage``. """
        return XenStorage(self.vm, vmdir=self.vmdir)