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Fixed #18194 -- Expiration of file-based sessions 

* Prevented stale session files from being loaded
* Added removal of stale session files in django-admin.py clearsessions

Thanks ej for the report, crodjer and Elvard for their inputs.
This commit is contained in:
Aymeric Augustin 2012-10-27 23:12:08 +02:00
parent 882c47cd40
commit 5fec97b9df
9 changed files with 176 additions and 29 deletions
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12
django/contrib/sessions/backends/base.py
View File

@ -1,7 +1,6 @@
from __future__ import unicode_literals
import base64
import time
from datetime import datetime, timedelta
try:
from django.utils.six.moves import cPickle as pickle
@ -309,3 +308,14 @@ class SessionBase(object):
Loads the session data and returns a dictionary.
"""
raise NotImplementedError
@classmethod
def clear_expired(cls):
"""
Remove expired sessions from the session store.
If this operation isn't possible on a given backend, it should raise
NotImplementedError. If it isn't necessary, because the backend has
a built-in expiration mechanism, it should be a no-op.
"""
raise NotImplementedError

4
django/contrib/sessions/backends/cache.py
View File

@ -65,3 +65,7 @@ class SessionStore(SessionBase):
return
session_key = self.session_key
self._cache.delete(KEY_PREFIX + session_key)
@classmethod
def clear_expired(cls):
pass

5
django/contrib/sessions/backends/db.py
View File

@ -71,6 +71,11 @@ class SessionStore(SessionBase):
except Session.DoesNotExist:
pass
@classmethod
def clear_expired(cls):
Session.objects.filter(expire_date__lt=timezone.now()).delete()
transaction.commit_unless_managed()
# At bottom to avoid circular import
from django.contrib.sessions.models import Session

71
django/contrib/sessions/backends/file.py
View File

@ -1,3 +1,4 @@
import datetime
import errno
import os
import tempfile
@ -5,27 +6,36 @@ import tempfile
from django.conf import settings
from django.contrib.sessions.backends.base import SessionBase, CreateError
from django.core.exceptions import SuspiciousOperation, ImproperlyConfigured
from django.utils import timezone
class SessionStore(SessionBase):
"""
Implements a file based session store.
"""
def __init__(self, session_key=None):
self.storage_path = getattr(settings, "SESSION_FILE_PATH", None)
if not self.storage_path:
self.storage_path = tempfile.gettempdir()
# Make sure the storage path is valid.
if not os.path.isdir(self.storage_path):
raise ImproperlyConfigured(
"The session storage path %r doesn't exist. Please set your"
" SESSION_FILE_PATH setting to an existing directory in which"
" Django can store session data." % self.storage_path)
self.storage_path = type(self)._get_storage_path()
self.file_prefix = settings.SESSION_COOKIE_NAME
super(SessionStore, self).__init__(session_key)
@classmethod
def _get_storage_path(cls):
try:
return cls._storage_path
except AttributeError:
storage_path = getattr(settings, "SESSION_FILE_PATH", None)
if not storage_path:
storage_path = tempfile.gettempdir()
# Make sure the storage path is valid.
if not os.path.isdir(storage_path):
raise ImproperlyConfigured(
"The session storage path %r doesn't exist. Please set your"
" SESSION_FILE_PATH setting to an existing directory in which"
" Django can store session data." % storage_path)
cls._storage_path = storage_path
return storage_path
VALID_KEY_CHARS = set("abcdef0123456789")
def _key_to_file(self, session_key=None):
@ -44,6 +54,18 @@ class SessionStore(SessionBase):
return os.path.join(self.storage_path, self.file_prefix + session_key)
def _last_modification(self):
"""
Return the modification time of the file storing the session's content.
"""
modification = os.stat(self._key_to_file()).st_mtime
if settings.USE_TZ:
modification = datetime.datetime.utcfromtimestamp(modification)
modification = modification.replace(tzinfo=timezone.utc)
else:
modification = datetime.datetime.fromtimestamp(modification)
return modification
def load(self):
session_data = {}
try:
@ -56,6 +78,15 @@ class SessionStore(SessionBase):
session_data = self.decode(file_data)
except (EOFError, SuspiciousOperation):
self.create()
# Remove expired sessions.
expiry_age = self.get_expiry_age(
modification=self._last_modification(),
expiry=session_data.get('_session_expiry'))
if expiry_age < 0:
session_data = {}
self.delete()
self.create()
except IOError:
self.create()
return session_data
@ -142,3 +173,19 @@ class SessionStore(SessionBase):
def clean(self):
pass
@classmethod
def clear_expired(cls):
storage_path = getattr(settings, "SESSION_FILE_PATH", tempfile.gettempdir())
file_prefix = settings.SESSION_COOKIE_NAME
for session_file in os.listdir(storage_path):
if not session_file.startswith(file_prefix):
continue
session_key = session_file[len(file_prefix):]
session = cls(session_key)
# When an expired session is loaded, its file is removed, and a
# new file is immediately created. Prevent this by disabling
# the create() method.
session.create = lambda: None
session.load()

4
django/contrib/sessions/backends/signed_cookies.py
View File

@ -92,3 +92,7 @@ class SessionStore(SessionBase):
return signing.dumps(session_cache, compress=True,
salt='django.contrib.sessions.backends.signed_cookies',
serializer=PickleSerializer)
@classmethod
def clear_expired(cls):
pass

14
django/contrib/sessions/management/commands/clearsessions.py
View File

@ -1,11 +1,15 @@
from django.conf import settings
from django.core.management.base import NoArgsCommand
from django.utils import timezone
from django.utils.importlib import import_module
class Command(NoArgsCommand):
help = "Can be run as a cronjob or directly to clean out expired sessions (only with the database backend at the moment)."
def handle_noargs(self, **options):
from django.db import transaction
from django.contrib.sessions.models import Session
Session.objects.filter(expire_date__lt=timezone.now()).delete()
transaction.commit_unless_managed()
engine = import_module(settings.SESSION_ENGINE)
try:
engine.SessionStore.clear_expired()
except NotImplementedError:
self.stderr.write("Session engine '%s' doesn't support clearing "
"expired sessions.\n" % settings.SESSION_ENGINE)

61
django/contrib/sessions/tests.py
View File

@ -1,4 +1,5 @@
from datetime import timedelta
import os
import shutil
import string
import tempfile
@ -12,6 +13,7 @@ from django.contrib.sessions.backends.file import SessionStore as FileSession
from django.contrib.sessions.backends.signed_cookies import SessionStore as CookieSession
from django.contrib.sessions.models import Session
from django.contrib.sessions.middleware import SessionMiddleware
from django.core import management
from django.core.cache import DEFAULT_CACHE_ALIAS
from django.core.exceptions import ImproperlyConfigured, SuspiciousOperation
from django.http import HttpResponse
@ -319,6 +321,30 @@ class DatabaseSessionTests(SessionTestsMixin, TestCase):
del self.session._session_cache
self.assertEqual(self.session['y'], 2)
@override_settings(SESSION_ENGINE="django.contrib.sessions.backends.db")
def test_clearsessions_command(self):
"""
Test clearsessions command for clearing expired sessions.
"""
self.assertEqual(0, Session.objects.count())
# One object in the future
self.session['foo'] = 'bar'
self.session.set_expiry(3600)
self.session.save()
# One object in the past
other_session = self.backend()
other_session['foo'] = 'bar'
other_session.set_expiry(-3600)
other_session.save()
# Two sessions are in the database before clearsessions...
self.assertEqual(2, Session.objects.count())
management.call_command('clearsessions')
# ... and one is deleted.
self.assertEqual(1, Session.objects.count())
@override_settings(USE_TZ=True)
class DatabaseSessionWithTimeZoneTests(DatabaseSessionTests):
@ -358,6 +384,9 @@ class FileSessionTests(SessionTestsMixin, unittest.TestCase):
# Do file session tests in an isolated directory, and kill it after we're done.
self.original_session_file_path = settings.SESSION_FILE_PATH
self.temp_session_store = settings.SESSION_FILE_PATH = tempfile.mkdtemp()
# Reset the file session backend's internal caches
if hasattr(self.backend, '_storage_path'):
del self.backend._storage_path
super(FileSessionTests, self).setUp()
def tearDown(self):
@ -368,6 +397,7 @@ class FileSessionTests(SessionTestsMixin, unittest.TestCase):
@override_settings(
SESSION_FILE_PATH="/if/this/directory/exists/you/have/a/weird/computer")
def test_configuration_check(self):
del self.backend._storage_path
# Make sure the file backend checks for a good storage dir
self.assertRaises(ImproperlyConfigured, self.backend)
@ -381,6 +411,37 @@ class FileSessionTests(SessionTestsMixin, unittest.TestCase):
self.assertRaises(SuspiciousOperation,
self.backend("a/b/c").load)
@override_settings(SESSION_ENGINE="django.contrib.sessions.backends.file")
def test_clearsessions_command(self):
"""
Test clearsessions command for clearing expired sessions.
"""
storage_path = self.backend._get_storage_path()
file_prefix = settings.SESSION_COOKIE_NAME
def count_sessions():
return len([session_file for session_file in os.listdir(storage_path)
if session_file.startswith(file_prefix)])
self.assertEqual(0, count_sessions())
# One object in the future
self.session['foo'] = 'bar'
self.session.set_expiry(3600)
self.session.save()
# One object in the past
other_session = self.backend()
other_session['foo'] = 'bar'
other_session.set_expiry(-3600)
other_session.save()
# Two sessions are in the filesystem before clearsessions...
self.assertEqual(2, count_sessions())
management.call_command('clearsessions')
# ... and one is deleted.
self.assertEqual(1, count_sessions())
class CacheSessionTests(SessionTestsMixin, unittest.TestCase):

2
docs/ref/django-admin.txt
View File

@ -1200,8 +1200,6 @@ clearsessions
Can be run as a cron job or directly to clean out expired sessions.
This is only supported by the database backend at the moment.
``django.contrib.sitemaps``
---------------------------

32
docs/topics/http/sessions.txt
View File

@ -272,6 +272,13 @@ You can edit it multiple times.
Returns either ``True`` or ``False``, depending on whether the user's
session cookie will expire when the user's Web browser is closed.
.. method:: SessionBase.clear_expired
.. versionadded:: 1.5
Removes expired sessions from the session store. This class method is
called by :djadmin:`clearsessions`.
Session object guidelines
-------------------------
@ -458,22 +465,29 @@ This setting is a global default and can be overwritten at a per-session level
by explicitly calling the :meth:`~backends.base.SessionBase.set_expiry` method
of ``request.session`` as described above in `using sessions in views`_.
Clearing the session table
Clearing the session store
==========================
If you're using the database backend, note that session data can accumulate in
the ``django_session`` database table and Django does *not* provide automatic
purging. Therefore, it's your job to purge expired sessions on a regular basis.
As users create new sessions on your website, session data can accumulate in
your session store. If you're using the database backend, the
``django_session`` database table will grow. If you're using the file backend,
your temporary directory will contain an increasing number of files.
To understand this problem, consider what happens when a user uses a session.
To understand this problem, consider what happens with the database backend.
When a user logs in, Django adds a row to the ``django_session`` database
table. Django updates this row each time the session data changes. If the user
logs out manually, Django deletes the row. But if the user does *not* log out,
the row never gets deleted.
the row never gets deleted. A similar process happens with the file backend.
Django provides a sample clean-up script: ``django-admin.py clearsessions``.
That script deletes any session in the session table whose ``expire_date`` is
in the past -- but your application may have different requirements.
Django does *not* provide automatic purging of expired sessions. Therefore,
it's your job to purge expired sessions on a regular basis. Django provides a
clean-up management command for this purpose: :djadmin:`clearsessions`. It's
recommended to call this command on a regular basis, for example as a daily
cron job.
Note that the cache backend isn't vulnerable to this problem, because caches
automatically delete stale data. Neither is the cookie backend, because the
session data is stored by the users' browsers.
Settings
========