# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
#
# Copyright 2011, Piston Cloud Computing, Inc.
#
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""
Utility methods to resize, repartition, and modify disk images.

Includes injection of SSH PGP keys into authorized_keys file.

"""

import crypt
import json
import os
import random
import tempfile

from nova import exception
from nova import flags
from nova import log as logging
from nova.openstack.common import cfg
from nova import utils
from nova.virt.disk import guestfs
from nova.virt.disk import loop
from nova.virt.disk import nbd


LOG = logging.getLogger(__name__)

disk_opts = [
    cfg.StrOpt('injected_network_template',
               default=utils.abspath('virt/interfaces.template'),
               help='Template file for injected network'),
    cfg.ListOpt('img_handlers',
                default=['loop', 'nbd', 'guestfs'],
                help='Order of methods used to mount disk images'),

    # NOTE(yamahata): ListOpt won't work because the command may include a
    #                 comma. For example:
    #
    #                 mkfs.ext3 -O dir_index,extent -E stride=8,stripe-width=16
    #                           --label %(fs_label)s %(target)s
    #
    #                 list arguments are comma separated and there is no way to
    #                 escape such commas.
    #
    cfg.MultiStrOpt('virt_mkfs',
                    default=[
                      'default=mkfs.ext3 -L %(fs_label)s -F %(target)s',
                      'linux=mkfs.ext3 -L %(fs_label)s -F %(target)s',
                      'windows=mkfs.ntfs'
                      ' --force --fast --label %(fs_label)s %(target)s',
                      # NOTE(yamahata): vfat case
                      #'windows=mkfs.vfat -n %(fs_label)s %(target)s',
                      ],
                    help='mkfs commands for ephemeral device. '
                         'The format is <os_type>=<mkfs command>'),
    ]

FLAGS = flags.FLAGS
FLAGS.register_opts(disk_opts)

_MKFS_COMMAND = {}
_DEFAULT_MKFS_COMMAND = None


for s in FLAGS.virt_mkfs:
    # NOTE(yamahata): mkfs command may includes '=' for its options.
    #                 So item.partition('=') doesn't work here
    os_type, mkfs_command = s.split('=', 1)
    if os_type:
        _MKFS_COMMAND[os_type] = mkfs_command
    if os_type == 'default':
        _DEFAULT_MKFS_COMMAND = mkfs_command


def mkfs(os_type, fs_label, target):
    mkfs_command = (_MKFS_COMMAND.get(os_type, _DEFAULT_MKFS_COMMAND) or
                    '') % locals()
    if mkfs_command:
        utils.execute(*mkfs_command.split())


def extend(image, size):
    """Increase image to size"""
    file_size = os.path.getsize(image)
    if file_size >= size:
        return
    utils.execute('qemu-img', 'resize', image, size)
    # NOTE(vish): attempts to resize filesystem
    utils.execute('e2fsck', '-fp', image, check_exit_code=False)
    utils.execute('resize2fs', image, check_exit_code=False)


def bind(src, target, instance_name):
    """Bind device to a filesytem"""
    if src:
        utils.execute('touch', target, run_as_root=True)
        utils.execute('mount', '-o', 'bind', src, target,
                run_as_root=True)
        s = os.stat(src)
        cgroup_info = "c %s:%s rwm" % (os.major(s.st_rdev),
                                       os.minor(s.st_rdev))
        cgroups_path = \
            "/sys/fs/cgroup/devices/sysdefault/libvirt/lxc/%s/devices.allow" \
            % instance_name
        utils.execute('echo', '>', cgroup_info, cgroups_path, run_as_root=True)


def unbind(target):
    if target:
        utils.execute('umount', target, run_as_root=True)


class _DiskImage(object):
    """Provide operations on a disk image file."""

    def __init__(self, image, partition=None, use_cow=False, mount_dir=None):
        # These passed to each mounter
        self.image = image
        self.partition = partition
        self.mount_dir = mount_dir

        # Internal
        self._mkdir = False
        self._mounter = None
        self._errors = []

        # As a performance tweak, don't bother trying to
        # directly loopback mount a cow image.
        self.handlers = FLAGS.img_handlers[:]
        if use_cow and 'loop' in self.handlers:
            self.handlers.remove('loop')

        if not self.handlers:
            raise exception.Error(_('no capable image handler configured'))

    @property
    def errors(self):
        """Return the collated errors from all operations."""
        return '\n--\n'.join([''] + self._errors)

    @staticmethod
    def _handler_class(mode):
        """Look up the appropriate class to use based on MODE."""
        for cls in (loop.Mount, nbd.Mount, guestfs.Mount):
            if cls.mode == mode:
                return cls
        raise exception.Error(_("unknown disk image handler: %s" % mode))

    def mount(self):
        """Mount a disk image, using the object attributes.

        The first supported means provided by the mount classes is used.

        True, or False is returned and the 'errors' attribute
        contains any diagnostics.
        """
        if self._mounter:
            raise exception.Error(_('image already mounted'))

        if not self.mount_dir:
            self.mount_dir = tempfile.mkdtemp()
            self._mkdir = True

        try:
            for h in self.handlers:
                mounter_cls = self._handler_class(h)
                mounter = mounter_cls(image=self.image,
                                      partition=self.partition,
                                      mount_dir=self.mount_dir)
                if mounter.do_mount():
                    self._mounter = mounter
                    break
                else:
                    LOG.debug(mounter.error)
                    self._errors.append(mounter.error)
        finally:
            if not self._mounter:
                self.umount()  # rmdir

        return bool(self._mounter)

    def umount(self):
        """Unmount a disk image from the file system."""
        try:
            if self._mounter:
                self._mounter.do_umount()
        finally:
            if self._mkdir:
                os.rmdir(self.mount_dir)


# Public module functions

def inject_data(image,
                key=None, net=None, metadata=None, admin_password=None,
                partition=None, use_cow=False):
    """Injects a ssh key and optionally net data into a disk image.

    it will mount the image as a fully partitioned disk and attempt to inject
    into the specified partition number.

    If partition is not specified it mounts the image as a single partition.

    """
    img = _DiskImage(image=image, partition=partition, use_cow=use_cow)
    if img.mount():
        try:
            inject_data_into_fs(img.mount_dir,
                                key, net, metadata, admin_password,
                                utils.execute)
        finally:
            img.umount()
    else:
        raise exception.Error(img.errors)


def inject_files(image, files, partition=None, use_cow=False):
    """Injects arbitrary files into a disk image"""
    img = _DiskImage(image=image, partition=partition, use_cow=use_cow)
    if img.mount():
        try:
            for (path, contents) in files:
                _inject_file_into_fs(img.mount_dir, path, contents)
        finally:
            img.umount()
    else:
        raise exception.Error(img.errors)


def setup_container(image, container_dir=None, use_cow=False):
    """Setup the LXC container.

    It will mount the loopback image to the container directory in order
    to create the root filesystem for the container.

    LXC does not support qcow2 images yet.
    """
    try:
        img = _DiskImage(image=image, use_cow=use_cow, mount_dir=container_dir)
        if img.mount():
            return img
        else:
            raise exception.Error(img.errors)
    except Exception, exn:
        LOG.exception(_('Failed to mount filesystem: %s'), exn)


def destroy_container(img):
    """Destroy the container once it terminates.

    It will umount the container that is mounted,
    and delete any  linked devices.

    LXC does not support qcow2 images yet.
    """
    try:
        if img:
            img.umount()
    except Exception, exn:
        LOG.exception(_('Failed to remove container: %s'), exn)


def inject_data_into_fs(fs, key, net, metadata, admin_password, execute):
    """Injects data into a filesystem already mounted by the caller.
    Virt connections can call this directly if they mount their fs
    in a different way to inject_data
    """
    if key:
        _inject_key_into_fs(key, fs, execute=execute)
    if net:
        _inject_net_into_fs(net, fs, execute=execute)
    if metadata:
        _inject_metadata_into_fs(metadata, fs, execute=execute)
    if admin_password:
        _inject_admin_password_into_fs(admin_password, fs, execute=execute)


def _inject_file_into_fs(fs, path, contents):
    absolute_path = os.path.join(fs, path.lstrip('/'))
    parent_dir = os.path.dirname(absolute_path)
    utils.execute('mkdir', '-p', parent_dir, run_as_root=True)
    utils.execute('tee', absolute_path, process_input=contents,
          run_as_root=True)


def _inject_metadata_into_fs(metadata, fs, execute=None):
    metadata_path = os.path.join(fs, "meta.js")
    metadata = dict([(m.key, m.value) for m in metadata])

    utils.execute('tee', metadata_path,
                  process_input=json.dumps(metadata), run_as_root=True)


def _inject_key_into_fs(key, fs, execute=None):
    """Add the given public ssh key to root's authorized_keys.

    key is an ssh key string.
    fs is the path to the base of the filesystem into which to inject the key.
    """
    sshdir = os.path.join(fs, 'root', '.ssh')
    utils.execute('mkdir', '-p', sshdir, run_as_root=True)
    utils.execute('chown', 'root', sshdir, run_as_root=True)
    utils.execute('chmod', '700', sshdir, run_as_root=True)
    keyfile = os.path.join(sshdir, 'authorized_keys')
    key_data = [
        '\n',
        '# The following ssh key was injected by Nova',
        '\n',
        key.strip(),
        '\n',
    ]
    utils.execute('tee', '-a', keyfile,
                  process_input=''.join(key_data), run_as_root=True)


def _inject_net_into_fs(net, fs, execute=None):
    """Inject /etc/network/interfaces into the filesystem rooted at fs.

    net is the contents of /etc/network/interfaces.
    """
    netdir = os.path.join(os.path.join(fs, 'etc'), 'network')
    utils.execute('mkdir', '-p', netdir, run_as_root=True)
    utils.execute('chown', 'root:root', netdir, run_as_root=True)
    utils.execute('chmod', 755, netdir, run_as_root=True)
    netfile = os.path.join(netdir, 'interfaces')
    utils.execute('tee', netfile, process_input=net, run_as_root=True)


def _inject_admin_password_into_fs(admin_passwd, fs, execute=None):
    """Set the root password to admin_passwd

    admin_password is a root password
    fs is the path to the base of the filesystem into which to inject
    the key.

    This method modifies the instance filesystem directly,
    and does not require a guest agent running in the instance.

    """
    # The approach used here is to copy the password and shadow
    # files from the instance filesystem to local files, make any
    # necessary changes, and then copy them back.

    admin_user = 'root'

    fd, tmp_passwd = tempfile.mkstemp()
    os.close(fd)
    fd, tmp_shadow = tempfile.mkstemp()
    os.close(fd)

    utils.execute('cp', os.path.join(fs, 'etc', 'passwd'), tmp_passwd,
                  run_as_root=True)
    utils.execute('cp', os.path.join(fs, 'etc', 'shadow'), tmp_shadow,
                  run_as_root=True)
    _set_passwd(admin_user, admin_passwd, tmp_passwd, tmp_shadow)
    utils.execute('cp', tmp_passwd, os.path.join(fs, 'etc', 'passwd'),
                  run_as_root=True)
    os.unlink(tmp_passwd)
    utils.execute('cp', tmp_shadow, os.path.join(fs, 'etc', 'shadow'),
                  run_as_root=True)
    os.unlink(tmp_shadow)


def _set_passwd(username, admin_passwd, passwd_file, shadow_file):
    """set the password for username to admin_passwd

    The passwd_file is not modified.  The shadow_file is updated.
    if the username is not found in both files, an exception is raised.

    :param username: the username
    :param encrypted_passwd: the  encrypted password
    :param passwd_file: path to the passwd file
    :param shadow_file: path to the shadow password file
    :returns: nothing
    :raises: exception.Error(), IOError()

    """
    salt_set = ('abcdefghijklmnopqrstuvwxyz'
                'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
                '0123456789./')
    # encryption algo - id pairs for crypt()
    algos = {'SHA-512': '$6$', 'SHA-256': '$5$', 'MD5': '$1$', 'DES': ''}

    salt = 16 * ' '
    salt = ''.join([random.choice(salt_set) for c in salt])

    # crypt() depends on the underlying libc, and may not support all
    # forms of hash. We try md5 first. If we get only 13 characters back,
    # then the underlying crypt() didn't understand the '$n$salt' magic,
    # so we fall back to DES.
    # md5 is the default because it's widely supported. Although the
    # local crypt() might support stronger SHA, the target instance
    # might not.
    encrypted_passwd = crypt.crypt(admin_passwd, algos['MD5'] + salt)
    if len(encrypted_passwd) == 13:
        encrypted_passwd = crypt.crypt(admin_passwd, algos['DES'] + salt)

    try:
        p_file = open(passwd_file, 'rb')
        s_file = open(shadow_file, 'rb')

        # username MUST exist in passwd file or it's an error
        found = False
        for entry in p_file:
            split_entry = entry.split(':')
            if split_entry[0] == username:
                found = True
                break
        if not found:
            msg = _('User %(username)s not found in password file.')
            raise exception.Error(msg % username)

        # update password in the shadow file.It's an error if the
        # the user doesn't exist.
        new_shadow = list()
        found = False
        for entry in s_file:
            split_entry = entry.split(':')
            if split_entry[0] == username:
                split_entry[1] = encrypted_passwd
                found = True
            new_entry = ':'.join(split_entry)
            new_shadow.append(new_entry)
        s_file.close()
        if not found:
            msg = _('User %(username)s not found in shadow file.')
            raise exception.Error(msg % username)
        s_file = open(shadow_file, 'wb')
        for entry in new_shadow:
            s_file.write(entry)
    finally:
        p_file.close()
        s_file.close()
