Mini Shell

# coding=utf-8
#
# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2019 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
import json
import logging
import os
import pwd
import shutil
import sys
import zlib
from contextlib import contextmanager
from typing import List, Optional  # NOQA

SNAPSHOT_PATH = '/var/lve/snapshots'
SNAPSHOT_EXT = '.snapshot'
SNAPSHOT_EXT_LEN = len(SNAPSHOT_EXT)


class Snapshot(object):
    """
    This class is responsible for loading and saving snapshot files for the interval
    The files will be saved in a format of: /var/lve/snapshots/[uid]/dump_time.snapshot
    dump_time is the timestamp/integer
    The directories /var/lve/snaphosts/[uid] and the dump files itself will be owned by user
    They will not be readable by other users.
    """

    def __init__(self, incident, compresslevel=1):
        # type: (dict, int) -> None
        self.compresslevel = compresslevel
        self.incident = incident
        self.log = logging.getLogger('lib-snapshot')

    def save(self, data):
        # type: (dict) -> str
        dump_date = data['dump_time']
        assert dump_date is not None

        # convert possible non-ascii data to unicode
        self._replace_unicode_data(data)
        json_compressed = zlib.compress(json.dumps(data).encode(), self.compresslevel)
        with self.create_file(dump_date) as f:
            f.write(json_compressed)
            self.log.debug('Snapshot dumped to file %s', f.name)
        return f.name

    @staticmethod
    def _to_unicode(obj):
        if isinstance(obj, bytes):
            return obj.decode('utf-8', 'replace')
        return obj

    def _replace_unicode_data(self, data):
        # type: (dict) -> None
        u_queries = []
        for query in data.get('snap_sql', []):
            u_queries.append(list(map(self._to_unicode, query)))
        data['snap_sql'] = u_queries

        u_urls = []
        for http in data.get('snap_http', []):
            u_urls.append(list(map(self._to_unicode, http)))
        data['snap_http'] = u_urls

    def get_file_list(self):
        # type: () -> List[str]
        dir_ = self.get_dir()
        if os.path.isdir(dir_):
            return os.listdir(dir_)
        return []

    def get_ts_list(self, from_ts, to_ts):
        # type: (Optional[int], Optional[int]) -> List[int]
        """
        Return ordered list of timestamps when snapshots for this use were created
        :param from_ts:
        :param to_ts:
        :return: list of timesteamps, ordered for that period
        """
        return self.snapshot_filter(self.get_file_list(), from_ts, to_ts)

    def get_snapshots(self, from_ts, to_ts):
        # type: (Optional[int], Optional[int]) -> list
        """
        Get all snapshot for a period
        :param from_ts
        :param to_ts
        :return: list of snapshots, ordered by date
        """
        result = []
        for ts in self.get_ts_list(from_ts, to_ts):
            try:
                filename = self.get_file_name(self.ts_to_name(ts))
                if not os.geteuid():
                    with drop_privileges(self.incident["uid"]):
                        content = self.read_file_content(filename)
                else:
                    content = self.read_file_content(filename)
                result.append(json.loads(content))
            except (IOError, ValueError, OSError) as ve:
                self.log.warning(
                    "Corrupted file: %s (%s)",
                    self.get_file_name(self.ts_to_name(ts)),
                    str(ve),
                )
        return result

    def read_file_content(self, filename):
        # type: (str) -> str
        with open(filename, 'rb') as f:
            content = f.read()
        try:
            content = zlib.decompress(content)
        except zlib.error:
            compressed_content = zlib.compress(content, self.compresslevel)
            with open(filename, 'wb') as f:
                f.write(compressed_content)
        return content.decode()

    def get_incident_snapshots(self):
        # type: () -> list
        """
        Load all snapshots for given incident
        :return: list of snapshots
        """
        return self.get_snapshots(self.incident["incident_start_time"], self.incident["incident_end_time"])

    def get_dir(self):
        # type: () -> str
        return os.path.join(SNAPSHOT_PATH, str(self.incident["uid"]))

    def get_file_name(self, name):
        # type: (str) -> str
        return os.path.join(self.get_dir(), name)

    def create_file(self, dump_date):
        # type: (int) -> open()
        """
        create file, change its ownership & permissions if needed. Create directories if needed as well
        :param dump_date: int timestamp used as file name
        :return: open File object
        """
        dir_ = self.get_dir()
        if not os.path.exists(dir_):
            try:  # sacrifice security if we cannot setup ownership properly
                os.makedirs(dir_)
                os.chmod(dir_, 0o751)
                os.chown(dir_, self.incident["uid"], 0)
            except (IOError, OSError) as e:
                self.log.error('Unable to create dir %s (%s)', dir_, str(e))
        file_name = self.get_file_name(self.ts_to_name(dump_date))
        with drop_privileges(self.incident["uid"]):
            file_ = open(file_name, 'wb')  # pylint: disable=consider-using-with
            try:
                os.fchmod(file_.fileno(), 0o400)
            except (IOError, OSError) as e:
                self.log.error('Unable to set file permissions %s (%s)', file_name, str(e))
        return file_

    def delete_old(self, to_ts):
        # type: (int) -> None
        """
        Delete old snapshots. If there are no more
        :param to_ts: up to which timestamp to remove snapshots
        :return: None
        """
        _dir = self.get_dir()
        files = os.listdir(_dir)
        all_snapshots = self.snapshot_filter(files)
        ts_to_remove = self.snapshot_filter(files, to_ts=to_ts)
        if all_snapshots == ts_to_remove:
            shutil.rmtree(_dir, ignore_errors=True)
        else:
            for ts in ts_to_remove:
                os.remove(self.get_file_name(self.ts_to_name(ts)))

    @staticmethod
    def get_ts(file_):
        # type: (str) -> Optional[int]
        if file_.endswith(SNAPSHOT_EXT):
            ts = file_[0:-SNAPSHOT_EXT_LEN]
            if ts.isdigit():
                try:
                    return int(ts)
                except ValueError:
                    pass
        return None

    @staticmethod
    def snapshot_filter(files, from_ts=None, to_ts=None):
        # type: (List[str], Optional[int], Optional[int]) -> List[int]
        if from_ts is None:
            from_ts = 0
        if to_ts is None:
            to_ts = sys.maxsize
        result = []
        for filename in files:
            ts = Snapshot.get_ts(filename)
            if ts is not None and from_ts <= ts <= to_ts:
                result.append(ts)
        return sorted(result)

    @staticmethod
    def ts_to_name(ts):
        # type: (int) -> str
        return str(ts) + SNAPSHOT_EXT


@contextmanager
def drop_privileges(uid):
    old_uid, old_gid, old_groups = os.getuid(), os.getgid(), os.getgroups()
    gid = pwd.getpwnam('nobody')[3]
    os.setgroups([])
    os.setegid(gid)
    os.seteuid(uid)
    try:
        yield
    finally:
        os.seteuid(old_uid)
        os.setegid(old_gid)
        os.setgroups(old_groups)