203 lines
7.6 KiB
Python
203 lines
7.6 KiB
Python
import datetime
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import logging
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import os
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import shutil
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import tempfile
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from django.conf import settings
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from django.contrib.sessions.backends.base import (
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VALID_KEY_CHARS, CreateError, SessionBase, UpdateError,
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)
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from django.contrib.sessions.exceptions import InvalidSessionKey
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from django.core.exceptions import ImproperlyConfigured, SuspiciousOperation
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from django.utils import timezone
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class SessionStore(SessionBase):
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"""
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Implement a file based session store.
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"""
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def __init__(self, session_key=None):
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self.storage_path = type(self)._get_storage_path()
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self.file_prefix = settings.SESSION_COOKIE_NAME
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super().__init__(session_key)
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@classmethod
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def _get_storage_path(cls):
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try:
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return cls._storage_path
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except AttributeError:
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storage_path = getattr(settings, 'SESSION_FILE_PATH', None) or tempfile.gettempdir()
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# Make sure the storage path is valid.
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if not os.path.isdir(storage_path):
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raise ImproperlyConfigured(
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"The session storage path %r doesn't exist. Please set your"
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" SESSION_FILE_PATH setting to an existing directory in which"
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" Django can store session data." % storage_path)
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cls._storage_path = storage_path
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return storage_path
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def _key_to_file(self, session_key=None):
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"""
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Get the file associated with this session key.
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"""
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if session_key is None:
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session_key = self._get_or_create_session_key()
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# Make sure we're not vulnerable to directory traversal. Session keys
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# should always be md5s, so they should never contain directory
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# components.
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if not set(session_key).issubset(VALID_KEY_CHARS):
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raise InvalidSessionKey(
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"Invalid characters in session key")
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return os.path.join(self.storage_path, self.file_prefix + session_key)
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def _last_modification(self):
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"""
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Return the modification time of the file storing the session's content.
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"""
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modification = os.stat(self._key_to_file()).st_mtime
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if settings.USE_TZ:
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modification = datetime.datetime.utcfromtimestamp(modification)
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return modification.replace(tzinfo=timezone.utc)
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return datetime.datetime.fromtimestamp(modification)
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def _expiry_date(self, session_data):
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"""
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Return the expiry time of the file storing the session's content.
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"""
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return session_data.get('_session_expiry') or (
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self._last_modification() + datetime.timedelta(seconds=settings.SESSION_COOKIE_AGE)
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)
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def load(self):
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session_data = {}
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try:
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with open(self._key_to_file(), "rb") as session_file:
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file_data = session_file.read()
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# Don't fail if there is no data in the session file.
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# We may have opened the empty placeholder file.
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if file_data:
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try:
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session_data = self.decode(file_data)
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except (EOFError, SuspiciousOperation) as e:
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if isinstance(e, SuspiciousOperation):
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logger = logging.getLogger('django.security.%s' % e.__class__.__name__)
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logger.warning(str(e))
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self.create()
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# Remove expired sessions.
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expiry_age = self.get_expiry_age(expiry=self._expiry_date(session_data))
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if expiry_age <= 0:
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session_data = {}
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self.delete()
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self.create()
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except (IOError, SuspiciousOperation):
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self._session_key = None
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return session_data
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def create(self):
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while True:
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self._session_key = self._get_new_session_key()
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try:
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self.save(must_create=True)
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except CreateError:
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continue
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self.modified = True
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return
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def save(self, must_create=False):
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if self.session_key is None:
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return self.create()
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# Get the session data now, before we start messing
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# with the file it is stored within.
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session_data = self._get_session(no_load=must_create)
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session_file_name = self._key_to_file()
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try:
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# Make sure the file exists. If it does not already exist, an
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# empty placeholder file is created.
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flags = os.O_WRONLY | getattr(os, 'O_BINARY', 0)
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if must_create:
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flags |= os.O_EXCL | os.O_CREAT
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fd = os.open(session_file_name, flags)
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os.close(fd)
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except FileNotFoundError:
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if not must_create:
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raise UpdateError
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except FileExistsError:
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if must_create:
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raise CreateError
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# Write the session file without interfering with other threads
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# or processes. By writing to an atomically generated temporary
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# file and then using the atomic os.rename() to make the complete
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# file visible, we avoid having to lock the session file, while
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# still maintaining its integrity.
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#
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# Note: Locking the session file was explored, but rejected in part
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# because in order to be atomic and cross-platform, it required a
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# long-lived lock file for each session, doubling the number of
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# files in the session storage directory at any given time. This
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# rename solution is cleaner and avoids any additional overhead
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# when reading the session data, which is the more common case
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# unless SESSION_SAVE_EVERY_REQUEST = True.
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#
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# See ticket #8616.
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dir, prefix = os.path.split(session_file_name)
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try:
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output_file_fd, output_file_name = tempfile.mkstemp(dir=dir, prefix=prefix + '_out_')
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renamed = False
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try:
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try:
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os.write(output_file_fd, self.encode(session_data).encode())
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finally:
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os.close(output_file_fd)
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# This will atomically rename the file (os.rename) if the OS
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# supports it. Otherwise this will result in a shutil.copy2
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# and os.unlink (for example on Windows). See #9084.
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shutil.move(output_file_name, session_file_name)
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renamed = True
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finally:
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if not renamed:
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os.unlink(output_file_name)
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except (OSError, IOError, EOFError):
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pass
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def exists(self, session_key):
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return os.path.exists(self._key_to_file(session_key))
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def delete(self, session_key=None):
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if session_key is None:
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if self.session_key is None:
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return
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session_key = self.session_key
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try:
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os.unlink(self._key_to_file(session_key))
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except OSError:
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pass
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def clean(self):
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pass
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@classmethod
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def clear_expired(cls):
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storage_path = cls._get_storage_path()
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file_prefix = settings.SESSION_COOKIE_NAME
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for session_file in os.listdir(storage_path):
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if not session_file.startswith(file_prefix):
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continue
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session_key = session_file[len(file_prefix):]
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session = cls(session_key)
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# When an expired session is loaded, its file is removed, and a
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# new file is immediately created. Prevent this by disabling
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# the create() method.
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session.create = lambda: None
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session.load()
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