350 lines
12 KiB
Python
350 lines
12 KiB
Python
import base64
|
|
import logging
|
|
import string
|
|
from datetime import datetime, timedelta
|
|
|
|
from django.conf import settings
|
|
from django.contrib.sessions.exceptions import SuspiciousSession
|
|
from django.core.exceptions import SuspiciousOperation
|
|
from django.utils import timezone
|
|
from django.utils.crypto import (
|
|
constant_time_compare, get_random_string, salted_hmac,
|
|
)
|
|
from django.utils.encoding import force_bytes
|
|
from django.utils.module_loading import import_string
|
|
|
|
# session_key should not be case sensitive because some backends can store it
|
|
# on case insensitive file systems.
|
|
VALID_KEY_CHARS = string.ascii_lowercase + string.digits
|
|
|
|
|
|
class CreateError(Exception):
|
|
"""
|
|
Used internally as a consistent exception type to catch from save (see the
|
|
docstring for SessionBase.save() for details).
|
|
"""
|
|
pass
|
|
|
|
|
|
class UpdateError(Exception):
|
|
"""
|
|
Occurs if Django tries to update a session that was deleted.
|
|
"""
|
|
pass
|
|
|
|
|
|
class SessionBase:
|
|
"""
|
|
Base class for all Session classes.
|
|
"""
|
|
TEST_COOKIE_NAME = 'testcookie'
|
|
TEST_COOKIE_VALUE = 'worked'
|
|
|
|
__not_given = object()
|
|
|
|
def __init__(self, session_key=None):
|
|
self._session_key = session_key
|
|
self.accessed = False
|
|
self.modified = False
|
|
self.serializer = import_string(settings.SESSION_SERIALIZER)
|
|
|
|
def __contains__(self, key):
|
|
return key in self._session
|
|
|
|
def __getitem__(self, key):
|
|
return self._session[key]
|
|
|
|
def __setitem__(self, key, value):
|
|
self._session[key] = value
|
|
self.modified = True
|
|
|
|
def __delitem__(self, key):
|
|
del self._session[key]
|
|
self.modified = True
|
|
|
|
def get(self, key, default=None):
|
|
return self._session.get(key, default)
|
|
|
|
def pop(self, key, default=__not_given):
|
|
self.modified = self.modified or key in self._session
|
|
args = () if default is self.__not_given else (default,)
|
|
return self._session.pop(key, *args)
|
|
|
|
def setdefault(self, key, value):
|
|
if key in self._session:
|
|
return self._session[key]
|
|
else:
|
|
self.modified = True
|
|
self._session[key] = value
|
|
return value
|
|
|
|
def set_test_cookie(self):
|
|
self[self.TEST_COOKIE_NAME] = self.TEST_COOKIE_VALUE
|
|
|
|
def test_cookie_worked(self):
|
|
return self.get(self.TEST_COOKIE_NAME) == self.TEST_COOKIE_VALUE
|
|
|
|
def delete_test_cookie(self):
|
|
del self[self.TEST_COOKIE_NAME]
|
|
|
|
def _hash(self, value):
|
|
key_salt = "django.contrib.sessions" + self.__class__.__name__
|
|
return salted_hmac(key_salt, value).hexdigest()
|
|
|
|
def encode(self, session_dict):
|
|
"Return the given session dictionary serialized and encoded as a string."
|
|
serialized = self.serializer().dumps(session_dict)
|
|
hash = self._hash(serialized)
|
|
return base64.b64encode(hash.encode() + b":" + serialized).decode('ascii')
|
|
|
|
def decode(self, session_data):
|
|
encoded_data = base64.b64decode(force_bytes(session_data))
|
|
try:
|
|
# could produce ValueError if there is no ':'
|
|
hash, serialized = encoded_data.split(b':', 1)
|
|
expected_hash = self._hash(serialized)
|
|
if not constant_time_compare(hash.decode(), expected_hash):
|
|
raise SuspiciousSession("Session data corrupted")
|
|
else:
|
|
return self.serializer().loads(serialized)
|
|
except Exception as e:
|
|
# ValueError, SuspiciousOperation, unpickling exceptions. If any of
|
|
# these happen, just return an empty dictionary (an empty session).
|
|
if isinstance(e, SuspiciousOperation):
|
|
logger = logging.getLogger('django.security.%s' % e.__class__.__name__)
|
|
logger.warning(str(e))
|
|
return {}
|
|
|
|
def update(self, dict_):
|
|
self._session.update(dict_)
|
|
self.modified = True
|
|
|
|
def has_key(self, key):
|
|
return key in self._session
|
|
|
|
def keys(self):
|
|
return self._session.keys()
|
|
|
|
def values(self):
|
|
return self._session.values()
|
|
|
|
def items(self):
|
|
return self._session.items()
|
|
|
|
def clear(self):
|
|
# To avoid unnecessary persistent storage accesses, we set up the
|
|
# internals directly (loading data wastes time, since we are going to
|
|
# set it to an empty dict anyway).
|
|
self._session_cache = {}
|
|
self.accessed = True
|
|
self.modified = True
|
|
|
|
def is_empty(self):
|
|
"Return True when there is no session_key and the session is empty."
|
|
try:
|
|
return not self._session_key and not self._session_cache
|
|
except AttributeError:
|
|
return True
|
|
|
|
def _get_new_session_key(self):
|
|
"Return session key that isn't being used."
|
|
while True:
|
|
session_key = get_random_string(32, VALID_KEY_CHARS)
|
|
if not self.exists(session_key):
|
|
return session_key
|
|
|
|
def _get_or_create_session_key(self):
|
|
if self._session_key is None:
|
|
self._session_key = self._get_new_session_key()
|
|
return self._session_key
|
|
|
|
def _validate_session_key(self, key):
|
|
"""
|
|
Key must be truthy and at least 8 characters long. 8 characters is an
|
|
arbitrary lower bound for some minimal key security.
|
|
"""
|
|
return key and len(key) >= 8
|
|
|
|
def _get_session_key(self):
|
|
return self.__session_key
|
|
|
|
def _set_session_key(self, value):
|
|
"""
|
|
Validate session key on assignment. Invalid values will set to None.
|
|
"""
|
|
if self._validate_session_key(value):
|
|
self.__session_key = value
|
|
else:
|
|
self.__session_key = None
|
|
|
|
session_key = property(_get_session_key)
|
|
_session_key = property(_get_session_key, _set_session_key)
|
|
|
|
def _get_session(self, no_load=False):
|
|
"""
|
|
Lazily load session from storage (unless "no_load" is True, when only
|
|
an empty dict is stored) and store it in the current instance.
|
|
"""
|
|
self.accessed = True
|
|
try:
|
|
return self._session_cache
|
|
except AttributeError:
|
|
if self.session_key is None or no_load:
|
|
self._session_cache = {}
|
|
else:
|
|
self._session_cache = self.load()
|
|
return self._session_cache
|
|
|
|
_session = property(_get_session)
|
|
|
|
def get_expiry_age(self, **kwargs):
|
|
"""Get the number of seconds until the session expires.
|
|
|
|
Optionally, this function accepts `modification` and `expiry` keyword
|
|
arguments specifying the modification and expiry of the session.
|
|
"""
|
|
try:
|
|
modification = kwargs['modification']
|
|
except KeyError:
|
|
modification = timezone.now()
|
|
# Make the difference between "expiry=None passed in kwargs" and
|
|
# "expiry not passed in kwargs", in order to guarantee not to trigger
|
|
# self.load() when expiry is provided.
|
|
try:
|
|
expiry = kwargs['expiry']
|
|
except KeyError:
|
|
expiry = self.get('_session_expiry')
|
|
|
|
if not expiry: # Checks both None and 0 cases
|
|
return settings.SESSION_COOKIE_AGE
|
|
if not isinstance(expiry, datetime):
|
|
return expiry
|
|
delta = expiry - modification
|
|
return delta.days * 86400 + delta.seconds
|
|
|
|
def get_expiry_date(self, **kwargs):
|
|
"""Get session the expiry date (as a datetime object).
|
|
|
|
Optionally, this function accepts `modification` and `expiry` keyword
|
|
arguments specifying the modification and expiry of the session.
|
|
"""
|
|
try:
|
|
modification = kwargs['modification']
|
|
except KeyError:
|
|
modification = timezone.now()
|
|
# Same comment as in get_expiry_age
|
|
try:
|
|
expiry = kwargs['expiry']
|
|
except KeyError:
|
|
expiry = self.get('_session_expiry')
|
|
|
|
if isinstance(expiry, datetime):
|
|
return expiry
|
|
expiry = expiry or settings.SESSION_COOKIE_AGE # Checks both None and 0 cases
|
|
return modification + timedelta(seconds=expiry)
|
|
|
|
def set_expiry(self, value):
|
|
"""
|
|
Set a custom expiration for the session. ``value`` can be an integer,
|
|
a Python ``datetime`` or ``timedelta`` object or ``None``.
|
|
|
|
If ``value`` is an integer, the session will expire after that many
|
|
seconds of inactivity. If set to ``0`` then the session will expire on
|
|
browser close.
|
|
|
|
If ``value`` is a ``datetime`` or ``timedelta`` object, the session
|
|
will expire at that specific future time.
|
|
|
|
If ``value`` is ``None``, the session uses the global session expiry
|
|
policy.
|
|
"""
|
|
if value is None:
|
|
# Remove any custom expiration for this session.
|
|
try:
|
|
del self['_session_expiry']
|
|
except KeyError:
|
|
pass
|
|
return
|
|
if isinstance(value, timedelta):
|
|
value = timezone.now() + value
|
|
self['_session_expiry'] = value
|
|
|
|
def get_expire_at_browser_close(self):
|
|
"""
|
|
Return ``True`` if the session is set to expire when the browser
|
|
closes, and ``False`` if there's an expiry date. Use
|
|
``get_expiry_date()`` or ``get_expiry_age()`` to find the actual expiry
|
|
date/age, if there is one.
|
|
"""
|
|
if self.get('_session_expiry') is None:
|
|
return settings.SESSION_EXPIRE_AT_BROWSER_CLOSE
|
|
return self.get('_session_expiry') == 0
|
|
|
|
def flush(self):
|
|
"""
|
|
Remove the current session data from the database and regenerate the
|
|
key.
|
|
"""
|
|
self.clear()
|
|
self.delete()
|
|
self._session_key = None
|
|
|
|
def cycle_key(self):
|
|
"""
|
|
Create a new session key, while retaining the current session data.
|
|
"""
|
|
data = self._session
|
|
key = self.session_key
|
|
self.create()
|
|
self._session_cache = data
|
|
if key:
|
|
self.delete(key)
|
|
|
|
# Methods that child classes must implement.
|
|
|
|
def exists(self, session_key):
|
|
"""
|
|
Return True if the given session_key already exists.
|
|
"""
|
|
raise NotImplementedError('subclasses of SessionBase must provide an exists() method')
|
|
|
|
def create(self):
|
|
"""
|
|
Create a new session instance. Guaranteed to create a new object with
|
|
a unique key and will have saved the result once (with empty data)
|
|
before the method returns.
|
|
"""
|
|
raise NotImplementedError('subclasses of SessionBase must provide a create() method')
|
|
|
|
def save(self, must_create=False):
|
|
"""
|
|
Save the session data. If 'must_create' is True, create a new session
|
|
object (or raise CreateError). Otherwise, only update an existing
|
|
object and don't create one (raise UpdateError if needed).
|
|
"""
|
|
raise NotImplementedError('subclasses of SessionBase must provide a save() method')
|
|
|
|
def delete(self, session_key=None):
|
|
"""
|
|
Delete the session data under this key. If the key is None, use the
|
|
current session key value.
|
|
"""
|
|
raise NotImplementedError('subclasses of SessionBase must provide a delete() method')
|
|
|
|
def load(self):
|
|
"""
|
|
Load the session data and return a dictionary.
|
|
"""
|
|
raise NotImplementedError('subclasses of SessionBase must provide a load() method')
|
|
|
|
@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('This backend does not support clear_expired().')
|