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from abc import ABC, abstractmethod
import contextlib
import errno
import logging
import os.path
import re
import socket
import subprocess
from .exceptions import BackupException, RemoteExecException
from . import repository
from . import ssh_remote
from . import _ssh_client
def _parse_name(name):
"""
Parse a backup name into a remote specification.
"""
# split off the username
if not '@' in name:
raise ValueError('Invalid backup name: "%s", must be of format user@host')
username, _, host = name.partition('@')
port = 22 # overridden later if specified in name
colons = host.count(':')
if colons >= 2: # IPv6 literal, possibly with port
m = re.match(r'\[(.+)\](:\d+)?', host, re.ASCII | re.IGNORECASE)
if m is not None: # [literal]:port
host, port = m.groups()
elif colons == 1: # host:port
host, _, port = host.partition(':')
return ssh_remote.SSHRemote(host, port, username)
class Target(ABC):
name = None
dirs = None
excludes = None
_logger = None
_index_opts = None
_save_opts = None
def __init__(self, name, dirs, excludes = None, logger = None):
if excludes is None:
excludes = []
self.name = name
self.dirs = dirs
self.excludes = excludes
if logger is None:
self._logger = logging.getLogger(self.name)
else:
self._logger = logger
self._index_opts = []
self._save_opts = []
def _do_save(self, bup_exec):
cmd = bup_exec + ['index', '--update', '--one-file-system'] + self._index_opts
cmd.extend(['--exclude=%s' % e for e in self.excludes])
cmd.extend(self.dirs)
self._logger.debug('Executing index command: ' + str(cmd))
res_idx = subprocess.run(cmd, capture_output = True)
cmd = bup_exec + ['save', '-n', self.name] + self._save_opts + self.dirs
self._logger.debug('Executing save command: ' + str(cmd))
res_save = subprocess.run(cmd, capture_output = True)
retcode = 0
output = b''
if res_idx.returncode != 0:
retcode = res_idx.returncode
output += res_idx.stderr + res_idx.stdout
if res_save.returncode != 0:
retcode = res_save.returncode
output += res_save.stderr + res_save.stdout
result = repository.StepResult(retcode, output)
return result
@abstractmethod
def save(self, data_dir):
pass
class TargetLocal(Target):
def save(self, data_dir):
return self._do_save(['bup'])
class TargetSSH(Target):
_remote = None
def __init__(self, name, dirs, excludes = None,
remote = None):
if remote is None:
remote = _parse_name(name)
if remote.proxy_remote is not None:
raise NotImplementedError('Proxy remote not implemented')
if remote.port != 22:
raise NotImplementedError('Specifying port not implemented')
self._remote = remote
super().__init__(name, dirs, excludes)
def save(self, data_dir):
return self._do_save(['bup', 'on', '%s@%s' % (self._remote.username, self._remote.host)])
class TargetSSHLXCLVM(TargetSSH):
"""
This target backs up an LXC container that lives on its own LVM logical
volume. Requires root-capable login on the container's host.
:param SSHRemote parent_remote:
"""
_parent_remote = None
_lxc_username = None
_lxc_containername = None
_container_mountpoint = '/mnt/bupper'
def __init__(self, name, dirs, excludes = None,
target_remote = None, parent_remote = None,
lxc_username = None, lxc_containername = None,
snapshot_size = '20G'):
dirs_snapshot = [os.path.join(self._container_mountpoint, d) for d in dirs]
excludes_snapshot = None
if excludes is not None:
excludes_snapshot = [os.path.join(self._container_mountpoint, e) for e in excludes]
super().__init__(name, dirs_snapshot, excludes_snapshot, target_remote)
if parent_remote is None:
raise ValueError('parent_remote not specified')
if lxc_username is None:
lxc_username = parent_remote.usename
self._parent_remote = parent_remote
self._lxc_username = lxc_username
self._lxc_containername = lxc_containername
self._snapshot_size = snapshot_size
def _paramiko_exec_cmd(self, client, cmd):
self._logger.debug('Client %s: executing command: %s' % (client, cmd))
res = client.exec_command(cmd)
chan = res[0].channel
chan.settimeout(64)
try:
out, err = res[1].read(), res[2].read()
except socket.timeout as t:
raise RemoteExecException('Timeout waiting for command output',
errno.ETIMEDOUT, b'') from t
chan.recv_exit_status()
if chan.exit_status != 0:
raise RemoteExecException('Error executing "%s"' % cmd,
chan.exit_status, err + out)
return out.decode('utf-8', errors = 'backslashreplace')
def save(self, data_dir):
with contextlib.ExitStack() as stack:
parent = stack.enter_context(_ssh_client.SSHConnection(self._parent_remote))
container = stack.enter_context(_ssh_client.SSHConnection(self._remote))
# create the mount directory
self._container_mountpoint = self._paramiko_exec_cmd(container,
'mktemp -d --tmpdir bupper.XXXXXXXX').rstrip('\n')
if len(self._container_mountpoint) <= 1 or self._container_mountpoint[0] != '/':
raise BackupException('Unexpected mount directory: %s' % self._container_mountpoint)
stack.callback(lambda: self._paramiko_exec_cmd(container,
'rmdir %s' % self._container_mountpoint))
self._save_opts.extend(['--strip-path', self._container_mountpoint])
# get the PID of the container's init
cmd_template = 'su -s /bin/sh -c "{command}" %s' % self._lxc_username
container_pid = self._paramiko_exec_cmd(parent, cmd_template.format(
command = 'lxc-info -H -p -n %s' % self._lxc_containername)).rstrip('\n')
if not re.fullmatch('[0-9]+', container_pid):
raise BackupException('Invalid container PID: %s' % container_pid)
# get the LV/VG for the container's rootfs
container_rootfs = self._paramiko_exec_cmd(parent, cmd_template.format(
command = 'lxc-info -H -c lxc.rootfs.path -n %s' %
self._lxc_containername))\
.rstrip('\n')\
.translate({ord(' ') : r'\040', ord('\t') : r'\011',
ord('\n') : r'\012', ord('\\') : r'\0134'})
if len(container_rootfs) <= 1 or container_rootfs[0] != '/':
raise BackupException('Unxpected container rootfs directory: %s' % container_rootfs)
mountline = self._paramiko_exec_cmd(parent, 'grep "%s" /proc/mounts' %
container_rootfs).rstrip('\n').split()
if len(mountline) < 2 or mountline[1] != container_rootfs:
raise BackupException('Invalid mount line: %s' % mountline)
lv_path = mountline[0]
lv_fstype = mountline[2]
if len(lv_path) <= 1 or lv_path[0] != '/' or len(lv_fstype) < 1:
raise BackupException('Unexpected LV path/FS type: %s\t%s' % (lv_path, lv_fstype))
lv_name, vg_name = self._paramiko_exec_cmd(parent,
'lvdisplay -C --noheadings -o lv_name,vg_name ' + lv_path)\
.strip().split()
if len(lv_name) < 1 or len(vg_name) < 1:
raise BackupException('Unexpected LV/VG name: %s\t%s' % (lv_name, vg_name))
# create a read-only snapshot
snapshot_name = 'bupper_' + lv_name
self._paramiko_exec_cmd(parent,
'lvcreate --permission r --snapshot -L {size} -n {name} {origin}'
.format(size = self._snapshot_size, name = snapshot_name,
origin = lv_path))
stack.callback(lambda: self._paramiko_exec_cmd(parent,
'lvremove -f %s/%s' % (vg_name, snapshot_name)))
# execute the backup
# wait for the new node to be created
self._paramiko_exec_cmd(parent, 'udevadm settle')
# we cannot trust any binaries located inside the container, since a
# compromised container could use them to execute arbitrary code
# with real root privileges, thus nullifying the point of
# unprivileged containers)
# so we ship a special tool, 'nsmount', which has to be
# installed on the parent, to mount the snapshot into the
# container mount namespace
self._paramiko_exec_cmd(parent,
'nsmount m {pid} {mountpoint} {devpath} {fstype}'.format(
pid = container_pid, mountpoint = self._container_mountpoint,
devpath = '/dev/%s/%s' % (vg_name, snapshot_name),
fstype = lv_fstype))
try:
ret = super().save(data_dir)
finally:
self._paramiko_exec_cmd(parent,
'nsmount u {pid} {mountpoint}'.format(
pid = container_pid, mountpoint = self._container_mountpoint))
return ret
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