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from hashlib import sha1
import base64
import binascii
import hmac
import time
import os
from zope.interface import implementer
from pyramid.compat import (
from pyramid.interfaces import ISession
from pyramid.util import strings_differ
def manage_accessed(wrapped):
""" Decorator which causes a cookie to be set when a wrapped
method is called"""
def accessed(session, *arg, **kw):
session.accessed = int(time.time())
if not session._dirty:
session._dirty = True
def set_cookie_callback(request, response):
session.request = None # explicitly break cycle for gc
return wrapped(session, *arg, **kw)
accessed.__doc__ = wrapped.__doc__
return accessed
def signed_serialize(data, secret):
""" Serialize any pickleable structure (``data``) and sign it
using the ``secret`` (must be a string). Return the
serialization, which includes the signature as its first 40 bytes.
The ``signed_deserialize`` method will deserialize such a value.
This function is useful for creating signed cookies. For example:
.. code-block:: python
cookieval = signed_serialize({'a':1}, 'secret')
response.set_cookie('signed_cookie', cookieval)
pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
sig =, pickled, sha1).hexdigest()
return sig + native_(base64.b64encode(pickled))
def signed_deserialize(serialized, secret, hmac=hmac):
""" Deserialize the value returned from ``signed_serialize``. If
the value cannot be deserialized for any reason, a
:exc:`ValueError` exception will be raised.
This function is useful for deserializing a signed cookie value
created by ``signed_serialize``. For example:
.. code-block:: python
cookieval = request.cookies['signed_cookie']
data = signed_deserialize(cookieval, 'secret')
# hmac parameterized only for unit tests
input_sig, pickled = (serialized[:40],
except (binascii.Error, TypeError) as e:
# Badly formed data can make base64 die
raise ValueError('Badly formed base64 data: %s' % e)
sig =, pickled, sha1).hexdigest()
# Avoid timing attacks (see
if strings_differ(sig, input_sig):
raise ValueError('Invalid signature')
return pickle.loads(pickled)
def UnencryptedCookieSessionFactoryConfig(
Configure a :term:`session factory` which will provide unencrypted
(but signed) cookie-based sessions. The return value of this
function is a :term:`session factory`, which may be provided as
the ``session_factory`` argument of a
:class:`pyramid.config.Configurator` constructor, or used
as the ``session_factory`` argument of the
The session factory returned by this function will create sessions
which are limited to storing fewer than 4000 bytes of data (as the
payload must fit into a single cookie).
A string which is used to sign the cookie.
A number of seconds of inactivity before a session times out.
The name of the cookie used for sessioning. Default: ``session``.
The maximum age of the cookie used for sessioning (in seconds).
Default: ``None`` (browser scope).
The path used for the session cookie. Default: ``/``.
The domain used for the session cookie. Default: ``None`` (no domain).
The 'secure' flag of the session cookie. Default: ``False``.
The 'httpOnly' flag of the session cookie. Default: ``False``.
If ``True``, set a session cookie even if an exception occurs
while rendering a view. Default: ``True``.
A callable which takes more or less arbitrary python data structure and
a secret and returns a signed serialization in bytes.
Default: ``signed_serialize`` (using pickle).
A callable which takes a signed and serialized data structure in bytes
and a secret and returns the original data structure if the signature
is valid. Default: ``signed_deserialize`` (using pickle).
class UnencryptedCookieSessionFactory(dict):
""" Dictionary-like session object """
# configuration parameters
_cookie_name = cookie_name
_cookie_max_age = cookie_max_age
_cookie_path = cookie_path
_cookie_domain = cookie_domain
_cookie_secure = cookie_secure
_cookie_httponly = cookie_httponly
_cookie_on_exception = cookie_on_exception
_secret = secret
_timeout = timeout
# dirty flag
_dirty = False
def __init__(self, request):
self.request = request
now = time.time()
created = accessed = now
new = True
value = None
state = {}
cookieval = request.cookies.get(self._cookie_name)
if cookieval is not None:
value = signed_deserialize(cookieval, self._secret)
except ValueError:
value = None
if value is not None:
accessed, created, state = value
new = False
if now - accessed > self._timeout:
state = {}
self.created = created
self.accessed = accessed = new
dict.__init__(self, state)
# ISession methods
def changed(self):
""" This is intentionally a noop; the session is
serialized on every access, so unnecessary"""
def invalidate(self):
self.clear() # XXX probably needs to unset cookie
# non-modifying dictionary methods
get = manage_accessed(dict.get)
__getitem__ = manage_accessed(dict.__getitem__)
items = manage_accessed(dict.items)
values = manage_accessed(dict.values)
keys = manage_accessed(dict.keys)
__contains__ = manage_accessed(dict.__contains__)
__len__ = manage_accessed(dict.__len__)
__iter__ = manage_accessed(dict.__iter__)
if not PY3:
iteritems = manage_accessed(dict.iteritems)
itervalues = manage_accessed(dict.itervalues)
iterkeys = manage_accessed(dict.iterkeys)
has_key = manage_accessed(dict.has_key)
# modifying dictionary methods
clear = manage_accessed(dict.clear)
update = manage_accessed(dict.update)
setdefault = manage_accessed(dict.setdefault)
pop = manage_accessed(dict.pop)
popitem = manage_accessed(dict.popitem)
__setitem__ = manage_accessed(dict.__setitem__)
__delitem__ = manage_accessed(dict.__delitem__)
# flash API methods
def flash(self, msg, queue='', allow_duplicate=True):
storage = self.setdefault('_f_' + queue, [])
if allow_duplicate or (msg not in storage):
def pop_flash(self, queue=''):
storage = self.pop('_f_' + queue, [])
return storage
def peek_flash(self, queue=''):
storage = self.get('_f_' + queue, [])
return storage
# CSRF API methods
def new_csrf_token(self):
token = text_(binascii.hexlify(os.urandom(20)))
self['_csrft_'] = token
return token
def get_csrf_token(self):
token = self.get('_csrft_', None)
if token is None:
token = self.new_csrf_token()
return token
# non-API methods
def _set_cookie(self, response):
if not self._cookie_on_exception:
exception = getattr(self.request, 'exception', None)
if exception is not None: # dont set a cookie during exceptions
return False
cookieval = signed_serialize(
(self.accessed, self.created, dict(self)), self._secret
if len(cookieval) > 4064:
raise ValueError(
'Cookie value is too long to store (%s bytes)' %
max_age = self._cookie_max_age,
path = self._cookie_path,
domain = self._cookie_domain,
secure = self._cookie_secure,
httponly = self._cookie_httponly,
return True
return UnencryptedCookieSessionFactory
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