import errno
import os
import tempfile
from django.conf import settings
from django.contrib.sessions.backends.base import SessionBase,CreateError
from django.core.exceptions import SuspiciousOperation,ImproperlyConfigured
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.file_prefix = settings.SESSION_COOKIE_NAME
super(SessionStore, self).__init__(session_key)
def _key_to_file(self, session_key=None):
"""
Get the file associated with this session key.
"""
if session_key is None:
session_key = self.session_key
# Make sure we're not vulnerable to directory traversal. Session keys
# should always be md5s, so they should never contain directory
# components.
if os.path.sep in session_key:
raise SuspiciousOperation(
"Invalid characters (directory components) in session key")
return os.path.join(self.storage_path, self.file_prefix + session_key)
def load(self):
session_data = {}
try:
session_file = open(self._key_to_file(), "rb")
try:
file_data = session_file.read()
# Don't fail if there is no data in the session file.
# We may have opened the empty placeholder file.
if file_data:
try:
session_data = self.decode(file_data)
except (EOFError, SuspiciousOperation):
self.create()
finally:
session_file.close()
except IOError:
pass
return session_data
def create(self):
while True:
self._session_key = self._get_new_session_key()
try:
self.save(must_create=True)
except CreateError:
continue
self.modified = True
self._session_cache = {}
return
def save(self, must_create=False):
# Get the session data now, before we start messing
# with the file it is stored within.
session_data = self._get_session(no_load=must_create)
session_file_name = self._key_to_file()
try:
# Make sure the file exists. If it does not already exist, an
# empty placeholder file is created.
flags = os.O_WRONLY | os.O_CREAT | getattr(os, 'O_BINARY', 0)
if must_create:
flags |= os.O_EXCL
fd = os.open(session_file_name, flags)
os.close(fd)
except OSError, e:
if must_create and e.errno == errno.EEXIST:
raise CreateError
raise
# Write the session file without interfering with other threads
# or processes. By writing to an atomically generated temporary
# file and then using the atomic os.rename() to make the complete
# file visible, we avoid having to lock the session file, while
# still maintaining its integrity.
#
# Note: Locking the session file was explored, but rejected in part
# because in order to be atomic and cross-platform, it required a
# long-lived lock file for each session, doubling the number of
# files in the session storage directory at any given time. This
# rename solution is cleaner and avoids any additional overhead
# when reading the session data, which is the more common case
# unless SESSION_SAVE_EVERY_REQUEST = True.
#
# See ticket #8616.
dir, prefix = os.path.split(session_file_name)
try:
output_file_fd, output_file_name = tempfile.mkstemp(dir=dir,
prefix=prefix + '_out_')
renamed = False
try:
try:
os.write(output_file_fd, self.encode(session_data))
finally:
os.close(output_file_fd)
os.rename(output_file_name, session_file_name)
renamed = True
finally:
if not renamed:
os.unlink(output_file_name)
except (OSError, IOError, EOFError):
pass
def exists(self, session_key):
if os.path.exists(self._key_to_file(session_key)):
return True
return False
def delete(self, session_key=None):
if session_key is None:
if self._session_key is None:
return
session_key = self._session_key
try:
os.unlink(self._key_to_file(session_key))
except OSError:
pass
def clean(self):
pass
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