import base64
import binascii
import hashlib
import hmac
import os
import time
from zope.deprecation import deprecated
from zope.interface import implementer
from webob.cookies import SignedSerializer
from pyramid.compat import (
pickle,
PY2,
text_,
bytes_,
native_,
urlparse,
)
from pyramid.exceptions import (
BadCSRFOrigin,
BadCSRFToken,
)
from pyramid.interfaces import ISession
from pyramid.settings import aslist
from pyramid.util import (
is_same_domain,
strings_differ,
)
def manage_accessed(wrapped):
""" Decorator which causes a cookie to be renewed when an accessor
method is called."""
def accessed(session, *arg, **kw):
session.accessed = now = int(time.time())
if session._reissue_time is not None:
if now - session.renewed > session._reissue_time:
session.changed()
return wrapped(session, *arg, **kw)
accessed.__doc__ = wrapped.__doc__
return accessed
def manage_changed(wrapped):
""" Decorator which causes a cookie to be set when a setter method
is called."""
def changed(session, *arg, **kw):
session.accessed = int(time.time())
session.changed()
return wrapped(session, *arg, **kw)
changed.__doc__ = wrapped.__doc__
return changed
[docs]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)
try:
# bw-compat with pyramid <= 1.5b1 where latin1 is the default
secret = bytes_(secret)
except UnicodeEncodeError:
secret = bytes_(secret, 'utf-8')
sig = hmac.new(secret, pickled, hashlib.sha1).hexdigest()
return sig + native_(base64.b64encode(pickled))
[docs]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
try:
input_sig, pickled = (bytes_(serialized[:40]),
base64.b64decode(bytes_(serialized[40:])))
except (binascii.Error, TypeError) as e:
# Badly formed data can make base64 die
raise ValueError('Badly formed base64 data: %s' % e)
try:
# bw-compat with pyramid <= 1.5b1 where latin1 is the default
secret = bytes_(secret)
except UnicodeEncodeError:
secret = bytes_(secret, 'utf-8')
sig = bytes_(hmac.new(secret, pickled, hashlib.sha1).hexdigest())
# Avoid timing attacks (see
# http://seb.dbzteam.org/crypto/python-oauth-timing-hmac.pdf)
if strings_differ(sig, input_sig):
raise ValueError('Invalid signature')
return pickle.loads(pickled)
[docs]def check_csrf_origin(request, trusted_origins=None, raises=True):
"""
Check the Origin of the request to see if it is a cross site request or
not.
If the value supplied by the Origin or Referer header isn't one of the
trusted origins and ``raises`` is ``True``, this function will raise a
:exc:`pyramid.exceptions.BadCSRFOrigin` exception but if ``raises`` is
``False`` this function will return ``False`` instead. If the CSRF origin
checks are successful this function will return ``True`` unconditionally.
Additional trusted origins may be added by passing a list of domain (and
ports if nonstandard like `['example.com', 'dev.example.com:8080']`) in
with the ``trusted_origins`` parameter. If ``trusted_origins`` is ``None``
(the default) this list of additional domains will be pulled from the
``pyramid.csrf_trusted_origins`` setting.
Note that this function will do nothing if request.scheme is not https.
.. versionadded:: 1.7
"""
def _fail(reason):
if raises:
raise BadCSRFOrigin(reason)
else:
return False
if request.scheme == "https":
# Suppose user visits http://example.com/
# An active network attacker (man-in-the-middle, MITM) sends a
# POST form that targets https://example.com/detonate-bomb/ and
# submits it via JavaScript.
#
# The attacker will need to provide a CSRF cookie and token, but
# that's no problem for a MITM when we cannot make any assumptions
# about what kind of session storage is being used. So the MITM can
# circumvent the CSRF protection. This is true for any HTTP connection,
# but anyone using HTTPS expects better! For this reason, for
# https://example.com/ we need additional protection that treats
# http://example.com/ as completely untrusted. Under HTTPS,
# Barth et al. found that the Referer header is missing for
# same-domain requests in only about 0.2% of cases or less, so
# we can use strict Referer checking.
# Determine the origin of this request
origin = request.headers.get("Origin")
if origin is None:
origin = request.referrer
# Fail if we were not able to locate an origin at all
if not origin:
return _fail("Origin checking failed - no Origin or Referer.")
# Parse our origin so we we can extract the required information from
# it.
originp = urlparse.urlparse(origin)
# Ensure that our Referer is also secure.
if originp.scheme != "https":
return _fail(
"Referer checking failed - Referer is insecure while host is "
"secure."
)
# Determine which origins we trust, which by default will include the
# current origin.
if trusted_origins is None:
trusted_origins = aslist(
request.registry.settings.get(
"pyramid.csrf_trusted_origins", [])
)
if request.host_port not in set(["80", "443"]):
trusted_origins.append("{0.domain}:{0.host_port}".format(request))
else:
trusted_origins.append(request.domain)
# Actually check to see if the request's origin matches any of our
# trusted origins.
if not any(is_same_domain(originp.netloc, host)
for host in trusted_origins):
reason = (
"Referer checking failed - {0} does not match any trusted "
"origins."
)
return _fail(reason.format(origin))
return True
[docs]def check_csrf_token(request,
token='csrf_token',
header='X-CSRF-Token',
raises=True):
""" Check the CSRF token in the request's session against the value in
``request.POST.get(token)`` (if a POST request) or
``request.headers.get(header)``. If a ``token`` keyword is not supplied to
this function, the string ``csrf_token`` will be used to look up the token
in ``request.POST``. If a ``header`` keyword is not supplied to this
function, the string ``X-CSRF-Token`` will be used to look up the token in
``request.headers``.
If the value supplied by post or by header doesn't match the value
supplied by ``request.session.get_csrf_token()``, and ``raises`` is
``True``, this function will raise an
:exc:`pyramid.exceptions.BadCSRFToken` exception.
If the values differ and ``raises`` is ``False``, this function will
return ``False``. If the CSRF check is successful, this function will
return ``True`` unconditionally.
Note that using this function requires that a :term:`session factory` is
configured.
See :ref:`auto_csrf_checking` for information about how to secure your
application automatically against CSRF attacks.
.. versionadded:: 1.4a2
.. versionchanged:: 1.7a1
A CSRF token passed in the query string of the request is no longer
considered valid. It must be passed in either the request body or
a header.
"""
supplied_token = ""
# If this is a POST/PUT/etc request, then we'll check the body to see if it
# has a token. We explicitly use request.POST here because CSRF tokens
# should never appear in an URL as doing so is a security issue. We also
# explicitly check for request.POST here as we do not support sending form
# encoded data over anything but a request.POST.
if token is not None:
supplied_token = request.POST.get(token, "")
# If we were unable to locate a CSRF token in a request body, then we'll
# check to see if there are any headers that have a value for us.
if supplied_token == "" and header is not None:
supplied_token = request.headers.get(header, "")
expected_token = request.session.get_csrf_token()
if strings_differ(bytes_(expected_token), bytes_(supplied_token)):
if raises:
raise BadCSRFToken('check_csrf_token(): Invalid token')
return False
return True
[docs]class PickleSerializer(object):
""" A serializer that uses the pickle protocol to dump Python
data to bytes.
This is the default serializer used by Pyramid.
``protocol`` may be specified to control the version of pickle used.
Defaults to :attr:`pickle.HIGHEST_PROTOCOL`.
"""
def __init__(self, protocol=pickle.HIGHEST_PROTOCOL):
self.protocol = protocol
def loads(self, bstruct):
"""Accept bytes and return a Python object."""
return pickle.loads(bstruct)
def dumps(self, appstruct):
"""Accept a Python object and return bytes."""
return pickle.dumps(appstruct, self.protocol)
[docs]def BaseCookieSessionFactory(
serializer,
cookie_name='session',
max_age=None,
path='/',
domain=None,
secure=False,
httponly=False,
timeout=1200,
reissue_time=0,
set_on_exception=True,
):
"""
.. versionadded:: 1.5
Configure a :term:`session factory` which will provide 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
:meth:`pyramid.config.Configurator.set_session_factory` method.
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).
.. warning:
This class provides no protection from tampering and is only intended
to be used by framework authors to create their own cookie-based
session factories.
Parameters:
``serializer``
An object with two methods: ``loads`` and ``dumps``. The ``loads``
method should accept bytes and return a Python object. The ``dumps``
method should accept a Python object and return bytes. A ``ValueError``
should be raised for malformed inputs.
``cookie_name``
The name of the cookie used for sessioning. Default: ``'session'``.
``max_age``
The maximum age of the cookie used for sessioning (in seconds).
Default: ``None`` (browser scope).
``path``
The path used for the session cookie. Default: ``'/'``.
``domain``
The domain used for the session cookie. Default: ``None`` (no domain).
``secure``
The 'secure' flag of the session cookie. Default: ``False``.
``httponly``
Hide the cookie from Javascript by setting the 'HttpOnly' flag of the
session cookie. Default: ``False``.
``timeout``
A number of seconds of inactivity before a session times out. If
``None`` then the cookie never expires. This lifetime only applies
to the *value* within the cookie. Meaning that if the cookie expires
due to a lower ``max_age``, then this setting has no effect.
Default: ``1200``.
``reissue_time``
The number of seconds that must pass before the cookie is automatically
reissued as the result of a request which accesses the session. The
duration is measured as the number of seconds since the last session
cookie was issued and 'now'. If this value is ``0``, a new cookie
will be reissued on every request accessing the session. If ``None``
then the cookie's lifetime will never be extended.
A good rule of thumb: if you want auto-expired cookies based on
inactivity: set the ``timeout`` value to 1200 (20 mins) and set the
``reissue_time`` value to perhaps a tenth of the ``timeout`` value
(120 or 2 mins). It's nonsensical to set the ``timeout`` value lower
than the ``reissue_time`` value, as the ticket will never be reissued.
However, such a configuration is not explicitly prevented.
Default: ``0``.
``set_on_exception``
If ``True``, set a session cookie even if an exception occurs
while rendering a view. Default: ``True``.
.. versionadded: 1.5a3
"""
@implementer(ISession)
class CookieSession(dict):
""" Dictionary-like session object """
# configuration parameters
_cookie_name = cookie_name
_cookie_max_age = max_age if max_age is None else int(max_age)
_cookie_path = path
_cookie_domain = domain
_cookie_secure = secure
_cookie_httponly = httponly
_cookie_on_exception = set_on_exception
_timeout = timeout if timeout is None else int(timeout)
_reissue_time = reissue_time if reissue_time is None else int(reissue_time)
# dirty flag
_dirty = False
def __init__(self, request):
self.request = request
now = time.time()
created = renewed = now
new = True
value = None
state = {}
cookieval = request.cookies.get(self._cookie_name)
if cookieval is not None:
try:
value = serializer.loads(bytes_(cookieval))
except ValueError:
# the cookie failed to deserialize, dropped
value = None
if value is not None:
try:
# since the value is not necessarily signed, we have
# to unpack it a little carefully
rval, cval, sval = value
renewed = float(rval)
created = float(cval)
state = sval
new = False
except (TypeError, ValueError):
# value failed to unpack properly or renewed was not
# a numeric type so we'll fail deserialization here
state = {}
if self._timeout is not None:
if now - renewed > self._timeout:
# expire the session because it was not renewed
# before the timeout threshold
state = {}
self.created = created
self.accessed = renewed
self.renewed = renewed
self.new = new
dict.__init__(self, state)
# ISession methods
def changed(self):
if not self._dirty:
self._dirty = True
def set_cookie_callback(request, response):
self._set_cookie(response)
self.request = None # explicitly break cycle for gc
self.request.add_response_callback(set_cookie_callback)
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 PY2:
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_changed(dict.clear)
update = manage_changed(dict.update)
setdefault = manage_changed(dict.setdefault)
pop = manage_changed(dict.pop)
popitem = manage_changed(dict.popitem)
__setitem__ = manage_changed(dict.__setitem__)
__delitem__ = manage_changed(dict.__delitem__)
# flash API methods
@manage_changed
def flash(self, msg, queue='', allow_duplicate=True):
storage = self.setdefault('_f_' + queue, [])
if allow_duplicate or (msg not in storage):
storage.append(msg)
@manage_changed
def pop_flash(self, queue=''):
storage = self.pop('_f_' + queue, [])
return storage
@manage_accessed
def peek_flash(self, queue=''):
storage = self.get('_f_' + queue, [])
return storage
# CSRF API methods
@manage_changed
def new_csrf_token(self):
token = text_(binascii.hexlify(os.urandom(20)))
self['_csrft_'] = token
return token
@manage_accessed
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 = native_(serializer.dumps(
(self.accessed, self.created, dict(self))
))
if len(cookieval) > 4064:
raise ValueError(
'Cookie value is too long to store (%s bytes)' %
len(cookieval)
)
response.set_cookie(
self._cookie_name,
value=cookieval,
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 CookieSession
[docs]def UnencryptedCookieSessionFactoryConfig(
secret,
timeout=1200,
cookie_name='session',
cookie_max_age=None,
cookie_path='/',
cookie_domain=None,
cookie_secure=False,
cookie_httponly=False,
cookie_on_exception=True,
signed_serialize=signed_serialize,
signed_deserialize=signed_deserialize,
):
"""
.. deprecated:: 1.5
Use :func:`pyramid.session.SignedCookieSessionFactory` instead.
Caveat: Cookies generated using ``SignedCookieSessionFactory`` are not
compatible with cookies generated using
``UnencryptedCookieSessionFactory``, so existing user session data
will be destroyed if you switch to it.
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
:meth:`pyramid.config.Configurator.set_session_factory`
method.
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).
Parameters:
``secret``
A string which is used to sign the cookie.
``timeout``
A number of seconds of inactivity before a session times out.
``cookie_name``
The name of the cookie used for sessioning.
``cookie_max_age``
The maximum age of the cookie used for sessioning (in seconds).
Default: ``None`` (browser scope).
``cookie_path``
The path used for the session cookie.
``cookie_domain``
The domain used for the session cookie. Default: ``None`` (no domain).
``cookie_secure``
The 'secure' flag of the session cookie.
``cookie_httponly``
The 'httpOnly' flag of the session cookie.
``cookie_on_exception``
If ``True``, set a session cookie even if an exception occurs
while rendering a view.
``signed_serialize``
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).
``signed_deserialize``
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 SerializerWrapper(object):
def __init__(self, secret):
self.secret = secret
def loads(self, bstruct):
return signed_deserialize(bstruct, secret)
def dumps(self, appstruct):
return signed_serialize(appstruct, secret)
serializer = SerializerWrapper(secret)
return BaseCookieSessionFactory(
serializer,
cookie_name=cookie_name,
max_age=cookie_max_age,
path=cookie_path,
domain=cookie_domain,
secure=cookie_secure,
httponly=cookie_httponly,
timeout=timeout,
reissue_time=0, # to keep session.accessed == session.renewed
set_on_exception=cookie_on_exception,
)
deprecated(
'UnencryptedCookieSessionFactoryConfig',
'The UnencryptedCookieSessionFactoryConfig callable is deprecated as of '
'Pyramid 1.5. Use ``pyramid.session.SignedCookieSessionFactory`` instead.'
' Caveat: Cookies generated using SignedCookieSessionFactory are not '
'compatible with cookies generated using UnencryptedCookieSessionFactory, '
'so existing user session data will be destroyed if you switch to it.'
)
[docs]def SignedCookieSessionFactory(
secret,
cookie_name='session',
max_age=None,
path='/',
domain=None,
secure=False,
httponly=False,
set_on_exception=True,
timeout=1200,
reissue_time=0,
hashalg='sha512',
salt='pyramid.session.',
serializer=None,
):
"""
.. versionadded:: 1.5
Configure a :term:`session factory` which will provide 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
:meth:`pyramid.config.Configurator.set_session_factory`
method.
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).
Parameters:
``secret``
A string which is used to sign the cookie. The secret should be at
least as long as the block size of the selected hash algorithm. For
``sha512`` this would mean a 512 bit (64 character) secret. It should
be unique within the set of secret values provided to Pyramid for
its various subsystems (see :ref:`admonishment_against_secret_sharing`).
``hashalg``
The HMAC digest algorithm to use for signing. The algorithm must be
supported by the :mod:`hashlib` library. Default: ``'sha512'``.
``salt``
A namespace to avoid collisions between different uses of a shared
secret. Reusing a secret for different parts of an application is
strongly discouraged (see :ref:`admonishment_against_secret_sharing`).
Default: ``'pyramid.session.'``.
``cookie_name``
The name of the cookie used for sessioning. Default: ``'session'``.
``max_age``
The maximum age of the cookie used for sessioning (in seconds).
Default: ``None`` (browser scope).
``path``
The path used for the session cookie. Default: ``'/'``.
``domain``
The domain used for the session cookie. Default: ``None`` (no domain).
``secure``
The 'secure' flag of the session cookie. Default: ``False``.
``httponly``
Hide the cookie from Javascript by setting the 'HttpOnly' flag of the
session cookie. Default: ``False``.
``timeout``
A number of seconds of inactivity before a session times out. If
``None`` then the cookie never expires. This lifetime only applies
to the *value* within the cookie. Meaning that if the cookie expires
due to a lower ``max_age``, then this setting has no effect.
Default: ``1200``.
``reissue_time``
The number of seconds that must pass before the cookie is automatically
reissued as the result of accessing the session. The
duration is measured as the number of seconds since the last session
cookie was issued and 'now'. If this value is ``0``, a new cookie
will be reissued on every request accessing the session. If ``None``
then the cookie's lifetime will never be extended.
A good rule of thumb: if you want auto-expired cookies based on
inactivity: set the ``timeout`` value to 1200 (20 mins) and set the
``reissue_time`` value to perhaps a tenth of the ``timeout`` value
(120 or 2 mins). It's nonsensical to set the ``timeout`` value lower
than the ``reissue_time`` value, as the ticket will never be reissued.
However, such a configuration is not explicitly prevented.
Default: ``0``.
``set_on_exception``
If ``True``, set a session cookie even if an exception occurs
while rendering a view. Default: ``True``.
``serializer``
An object with two methods: ``loads`` and ``dumps``. The ``loads``
method should accept bytes and return a Python object. The ``dumps``
method should accept a Python object and return bytes. A ``ValueError``
should be raised for malformed inputs. If a serializer is not passed,
the :class:`pyramid.session.PickleSerializer` serializer will be used.
.. versionadded: 1.5a3
"""
if serializer is None:
serializer = PickleSerializer()
signed_serializer = SignedSerializer(
secret,
salt,
hashalg,
serializer=serializer,
)
return BaseCookieSessionFactory(
signed_serializer,
cookie_name=cookie_name,
max_age=max_age,
path=path,
domain=domain,
secure=secure,
httponly=httponly,
timeout=timeout,
reissue_time=reissue_time,
set_on_exception=set_on_exception,
)
