FreedomBox/actions/backups

#!/usr/bin/python3
# -*- mode: python -*-
# SPDX-License-Identifier: AGPL-3.0-or-later
"""
Wrapper to handle backups using borg-backups.
"""

import argparse
import json
import os
import pathlib
import re
import subprocess
import sys
import tarfile

from plinth.modules.backups import MANIFESTS_FOLDER
from plinth.utils import Version

TIMEOUT = 30
BACKUPS_DATA_PATH = pathlib.Path('/var/lib/plinth/backups-data/')


def parse_arguments():
    """Return parsed command line arguments as dictionary."""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')

    setup = subparsers.add_parser(
        'setup', help='Create repository if it does not already exist')

    init = subparsers.add_parser('init', help='Initialize a repository')
    init.add_argument('--encryption', help='Encryption of the repository',
                      required=True)

    info = subparsers.add_parser('info', help='Show repository information')

    list_repo = subparsers.add_parser('list-repo',
                                      help='List repository contents')

    create_archive = subparsers.add_parser('create-archive',
                                           help='Create archive')
    create_archive.add_argument('--paths', help='Paths to include in archive',
                                nargs='+')
    create_archive.add_argument('--comment',
                                help='Comment text to add to archive',
                                default='')

    delete_archive = subparsers.add_parser('delete-archive',
                                           help='Delete archive')

    export_help = 'Export archive contents as tar on stdout'
    export_tar = subparsers.add_parser('export-tar', help=export_help)

    get_archive_apps = subparsers.add_parser(
        'get-archive-apps', help='Get list of apps included in archive')

    restore_archive = subparsers.add_parser(
        'restore-archive', help='Restore files from an archive')
    restore_archive.add_argument('--destination', help='Destination',
                                 required=True)

    for cmd in [
            info, init, list_repo, create_archive, delete_archive, export_tar,
            get_archive_apps, restore_archive, setup
    ]:
        cmd.add_argument('--path', help='Repository or Archive path',
                         required=False)
        cmd.add_argument('--ssh-keyfile', help='Path of private ssh key',
                         default=None)

    get_exported_archive_apps = subparsers.add_parser(
        'get-exported-archive-apps',
        help='Get list of apps included in exported archive file')
    get_exported_archive_apps.add_argument('--path', help='Tarball file path',
                                           required=True)

    restore_exported_archive = subparsers.add_parser(
        'restore-exported-archive',
        help='Restore files from an exported archive')
    restore_exported_archive.add_argument('--path', help='Tarball file path',
                                          required=True)

    dump_settings = subparsers.add_parser('dump-settings',
                                          help='Dump JSON settings to a file')
    dump_settings.add_argument('--app-id',
                               help='ID of the app to dump settings for')

    load_settings = subparsers.add_parser(
        'load-settings', help='Load JSON settings from a file')
    load_settings.add_argument('--app-id',
                               help='ID of the app to load settings for')

    subparsers.required = True
    return parser.parse_args()


def subcommand_setup(arguments):
    """Create repository if it does not already exist."""
    try:
        run(['borg', 'info', arguments.path], arguments, check=True)
    except subprocess.CalledProcessError:
        path = os.path.dirname(arguments.path)
        if not os.path.exists(path):
            os.makedirs(path)

        init_repository(arguments, encryption='none')


def init_repository(arguments, encryption):
    """Initialize a local or remote borg repository"""
    if encryption != 'none':
        if not _read_encryption_passphrase(arguments):
            raise ValueError('No encryption passphrase provided')

    cmd = ['borg', 'init', '--encryption', encryption, arguments.path]
    run(cmd, arguments)


def subcommand_init(arguments):
    """Initialize the borg repository."""
    init_repository(arguments, encryption=arguments.encryption)


def subcommand_info(arguments):
    """Show repository information."""
    run(['borg', 'info', '--json', arguments.path], arguments)


def subcommand_list_repo(arguments):
    """List repository contents."""
    run(['borg', 'list', '--json', '--format="{comment}"', arguments.path],
        arguments)


def _get_borg_version(arugments):
    """Return the version of borgbackup."""
    process = run(['borg', '--version'], arugments, stdout=subprocess.PIPE)
    return process.stdout.decode().split()[1]  # Example: "borg 1.1.9"


def subcommand_create_archive(arguments):
    """Create archive."""
    paths = filter(os.path.exists, arguments.paths)
    command = ['borg', 'create', '--json']
    if arguments.comment:
        comment = arguments.comment
        if Version(_get_borg_version(arguments)) < Version('1.1.10'):
            # Undo any placeholder escape sequences in comments as this version
            # of borg does not support placeholders. XXX: Drop this code when
            # support for borg < 1.1.10 is dropped.
            comment = comment.replace('{{', '{').replace('}}', '}')

        command += ['--comment', comment]

    command += [arguments.path] + list(paths)
    run(command, arguments)


def subcommand_delete_archive(arguments):
    """Delete archive."""
    run(['borg', 'delete', arguments.path], arguments)


def _extract(archive_path, destination, arguments, locations=None):
    """Extract archive contents."""
    prev_dir = os.getcwd()
    borg_call = ['borg', 'extract', archive_path]
    # do not extract any files when we get an empty locations list
    if locations is not None:
        borg_call.extend(locations)

    try:
        os.chdir(os.path.expanduser(destination))
        # TODO: with python 3.7 use subprocess.run with the 'capture_output'
        # argument
        process = run(borg_call, arguments, check=False,
                      stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        if process.returncode != 0:
            error = process.stderr.decode()
            # Don't fail on the borg error when no files were matched
            if "never matched" not in error:
                raise subprocess.CalledProcessError(process.returncode,
                                                    process.args)
    finally:
        os.chdir(prev_dir)


def subcommand_export_tar(arguments):
    """Export archive contents as tar stream on stdout."""
    run(['borg', 'export-tar', arguments.path, '-', '--tar-filter=gzip'],
        arguments)


def _read_archive_file(archive, filepath, arguments):
    """Read the content of a file inside an archive"""
    borg_call = ['borg', 'extract', archive, filepath, '--stdout']
    return run(borg_call, arguments, stdout=subprocess.PIPE).stdout.decode()


def subcommand_get_archive_apps(arguments):
    """Get list of apps included in archive."""
    manifest_folder = os.path.relpath(MANIFESTS_FOLDER, '/')
    borg_call = [
        'borg', 'list', arguments.path, manifest_folder, '--format',
        '{path}{NEWLINE}'
    ]
    try:
        borg_process = run(borg_call, arguments, stdout=subprocess.PIPE)
        manifest_path = borg_process.stdout.decode().strip()
    except subprocess.CalledProcessError:
        sys.exit(1)

    manifest = None
    if manifest_path:
        manifest_data = _read_archive_file(arguments.path, manifest_path,
                                           arguments)
        manifest = json.loads(manifest_data)

    if manifest:
        for app in _get_apps_of_manifest(manifest):
            print(app['name'])


def _get_apps_of_manifest(manifest):
    """Get apps of a manifest.

    Supports both dict format as well as list format of plinth <=0.42

    """
    if isinstance(manifest, list):
        apps = manifest
    elif isinstance(manifest, dict) and 'apps' in manifest:
        apps = manifest['apps']
    else:
        raise RuntimeError('Unknown manifest format')

    return apps


def subcommand_get_exported_archive_apps(arguments):
    """Get list of apps included in an exported archive file."""
    manifest = None
    with tarfile.open(arguments.path) as tar_handle:
        filenames = tar_handle.getnames()
        for name in filenames:
            if 'var/lib/plinth/backups-manifests/' in name \
               and name.endswith('.json'):
                manifest_data = tar_handle.extractfile(name).read()
                manifest = json.loads(manifest_data)
                break

    if manifest:
        for app in _get_apps_of_manifest(manifest):
            print(app['name'])


def subcommand_restore_archive(arguments):
    """Restore files from an archive."""
    _locations = json.loads(arguments.stdin)
    locations = _locations['directories'] + _locations['files']
    locations = [os.path.relpath(location, '/') for location in locations]
    _extract(arguments.path, arguments.destination, arguments,
             locations=locations)


def subcommand_restore_exported_archive(arguments):
    """Restore files from an exported archive."""
    locations = json.loads(arguments.stdin)

    with tarfile.open(arguments.path) as tar_handle:
        for member in tar_handle.getmembers():
            path = '/' + member.name
            if path in locations['files']:
                tar_handle.extract(member, '/')
            else:
                for directory in locations['directories']:
                    if path.startswith(directory):
                        tar_handle.extract(member, '/')
                        break


def _assert_app_id(app_id):
    """Check that app ID is correct."""
    if not re.fullmatch(r'[a-z0-9_]+', app_id):
        raise Exception('Invalid App ID')


def subcommand_dump_settings(arguments):
    """Dump an app's settings to a JSON file."""
    app_id = arguments.app_id
    _assert_app_id(app_id)
    BACKUPS_DATA_PATH.mkdir(exist_ok=True)
    settings_path = BACKUPS_DATA_PATH / f'{app_id}-settings.json'
    settings_path.write_text(arguments.stdin)


def subcommand_load_settings(arguments):
    """Load an app's settings from a JSON file."""
    app_id = arguments.app_id
    _assert_app_id(app_id)
    settings_path = BACKUPS_DATA_PATH / f'{app_id}-settings.json'
    try:
        print(settings_path.read_text())
    except FileNotFoundError:
        print('{}')


def _read_encryption_passphrase(arguments):
    """Read encryption passphrase from stdin."""
    if arguments.stdin:
        try:
            return json.loads(arguments.stdin)['encryption_passphrase']
        except KeyError:
            pass

    return None


def get_env(arguments):
    """Create encryption and ssh kwargs out of given arguments"""
    env = dict(os.environ, BORG_RELOCATED_REPO_ACCESS_IS_OK='yes',
               LANG='C.UTF-8')
    # Always provide BORG_PASSPHRASE (also if empty) so borg does not get stuck
    # while asking for a passphrase.
    encryption_passphrase = _read_encryption_passphrase(arguments)
    env['BORG_PASSPHRASE'] = encryption_passphrase or ''

    return env


def run(cmd, arguments, check=True, **kwargs):
    """Wrap the command with extra encryption passphrase handling."""
    env = get_env(arguments)
    return subprocess.run(cmd, check=check, env=env, **kwargs)


def main():
    """Parse arguments and perform all duties."""
    arguments = parse_arguments()
    arguments.stdin = sys.stdin.read()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]
    subcommand_method(arguments)


if __name__ == '__main__':
    main()