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import base64
import time
from datetime import datetime, timedelta
try:
import cPickle as pickle
except ImportError:
import pickle
from django.conf import settings
from django.core.exceptions import SuspiciousOperation
from django.utils.crypto import constant_time_compare
from django.utils.crypto import get_random_string
from django.utils.crypto import salted_hmac
from django.utils import timezone
class CreateError(Exception):
"""
Used internally as a consistent exception type to catch from save (see the
docstring for SessionBase.save() for details).
"""
pass
class SessionBase(object):
"""
Base class for all Session classes.
"""
TEST_COOKIE_NAME = 'testcookie'
TEST_COOKIE_VALUE = 'worked'
def __init__(self, session_key=None):
self._session_key = session_key
self.accessed = False
self.modified = False
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, *args):
self.modified = self.modified or key in self._session
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):
"Returns the given session dictionary pickled and encoded as a string."
pickled = pickle.dumps(session_dict, pickle.HIGHEST_PROTOCOL)
hash = self._hash(pickled)
return base64.encodestring(hash + ":" + pickled)
def decode(self, session_data):
encoded_data = base64.decodestring(session_data)
try:
# could produce ValueError if there is no ':'
hash, pickled = encoded_data.split(':', 1)
expected_hash = self._hash(pickled)
if not constant_time_compare(hash, expected_hash):
raise SuspiciousOperation("Session data corrupted")
else:
return pickle.loads(pickled)
except Exception:
# ValueError, SuspiciousOperation, unpickling exceptions. If any of
# these happen, just return an empty dictionary (an empty session).
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 iterkeys(self):
return self._session.iterkeys()
def itervalues(self):
return self._session.itervalues()
def iteritems(self):
return self._session.iteritems()
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 _get_new_session_key(self):
"Returns session key that isn't being used."
# Todo: move to 0-9a-z charset in 1.5
hex_chars = '1234567890abcdef'
# session_key should not be case sensitive because some backends
# can store it on case insensitive file systems.
while True:
session_key = get_random_string(32, hex_chars)
if not self.exists(session_key):
break
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 _get_session_key(self):
return self._session_key
session_key = property(_get_session_key)
def _get_session(self, no_load=False):
"""
Lazily loads session from storage (unless "no_load" is True, when only
an empty dict is stored) and stores 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):
"""Get the number of seconds until the session expires."""
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 - timezone.now()
return delta.days * 86400 + delta.seconds
def get_expiry_date(self):
"""Get session the expiry date (as a datetime object)."""
expiry = self.get('_session_expiry')
if isinstance(expiry, datetime):
return expiry
if not expiry: # Checks both None and 0 cases
expiry = settings.SESSION_COOKIE_AGE
return timezone.now() + timedelta(seconds=expiry)
def set_expiry(self, value):
"""
Sets 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):
"""
Returns ``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):
"""
Removes the current session data from the database and regenerates the
key.
"""
self.clear()
self.delete()
self.create()
def cycle_key(self):
"""
Creates a new session key, whilst retaining the current session data.
"""
data = self._session_cache
key = self.session_key
self.create()
self._session_cache = data
self.delete(key)
# Methods that child classes must implement.
def exists(self, session_key):
"""
Returns True if the given session_key already exists.
"""
raise NotImplementedError
def create(self):
"""
Creates 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
def save(self, must_create=False):
"""
Saves the session data. If 'must_create' is True, a new session object
is created (otherwise a CreateError exception is raised). Otherwise,
save() can update an existing object with the same key.
"""
raise NotImplementedError
def delete(self, session_key=None):
"""
Deletes the session data under this key. If the key is None, the
current session key value is used.
"""
raise NotImplementedError
def load(self):
"""
Loads the session data and returns a dictionary.
"""
raise NotImplementedError
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