from abc import ABC, abstractmethod import contextlib import errno import logging 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 _path_prefix = '' 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): excludes = [self._path_prefix + '/' + e for e in self.excludes] dirs = [self._path_prefix + '/' + d for d in self.dirs] # index cmd = bup_exec + ['index', '--update', '--one-file-system'] + self._index_opts cmd.extend(['--exclude=%s' % e for e in excludes]) cmd.extend(dirs) self._logger.debug('Executing index command: ' + str(cmd)) res_idx = subprocess.run(cmd, capture_output = True) # save cmd = bup_exec + ['save', '-n', self.name] + self._save_opts + 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, logger = 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, logger) 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 def __init__(self, name, dirs, excludes = None, logger = None, target_remote = None, parent_remote = None, lxc_username = None, lxc_containername = None, snapshot_size = '20G'): 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 super().__init__(name, dirs, excludes, logger, target_remote) 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) out = out.decode('utf-8', errors = 'backslashreplace') err = err.decode('utf-8', errors = 'backslashreplace') self._logger.debug('Command successful.') if len(out): self._logger.debug('Command stdout: %s' % out) if len(err): self._logger.debug('Command stderr: %s' % err) return out 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 container_mountpoint = self._paramiko_exec_cmd(container, 'mktemp -d --tmpdir bupper.XXXXXXXX').rstrip('\n') # make sure it's # - non-empty # - an absolute path # - contains no whitespace if (len(container_mountpoint) <= 1 or container_mountpoint[0] != '/' or re.search(r'\s', container_mountpoint)): raise BackupException('Unexpected mount directory: %s' % container_mountpoint) stack.callback(lambda: self._paramiko_exec_cmd(container, 'rmdir %s' % container_mountpoint)) self._path_prefix = container_mountpoint self._save_opts.extend(['--strip-path', 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') # make sure it's a number 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') # oct-escape certain characters as they are in /proc/mounts # see seq_path[_root]() in linux container_rootfs = container_rootfs.translate( { ord(' ') : r'\040', ord('\t') : r'\011', ord('\n') : r'\012', ord('\\') : r'\0134'}) # make sure the rootfs path is # - non-empty # - an absolute path # - contains no whitespace if (len(container_rootfs) <= 1 or container_rootfs[0] != '/' or re.search(r'\s', container_rootfs)): raise BackupException('Unxpected container rootfs directory: %s' % container_rootfs) # find the device node and the filesystem type for the container rootfs mountlines = self._paramiko_exec_cmd(parent, 'grep "%s" /proc/mounts' % container_rootfs).splitlines() if len(mountlines) != 1: raise BackupException('Expected exactly one matching mount line for the ' 'container root, got %d' % len(mountlines)) mountline = mountlines[0].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] # make sure the LV path is # - non-empty # - an absolute path # - contains no whitespace # and that the FS type is non-empty if (len(lv_path) <= 1 or lv_path[0] != '/' or re.search(r'\s', lv_path) or len(lv_fstype) < 1): raise BackupException('Unexpected LV path/FS type: %s\t%s' % (lv_path, lv_fstype)) # find the LV and VG names lvdisplay = self._paramiko_exec_cmd(parent, 'lvdisplay -C --noheadings -o lv_name,vg_name ' + lv_path).split() if len(lvdisplay) != 2: raise BackupException('Unexpected lvdisplay output: %s' % str(lvdisplay)) lv_name, vg_name = lvdisplay 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 = 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 = container_mountpoint)) return ret