Doc/library/cookie.rst

:mod:`Cookie` --- HTTP state management
=======================================

.. module:: Cookie
   :synopsis: Support for HTTP state management (cookies).
.. moduleauthor:: Timothy O'Malley <timo@alum.mit.edu>
.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>

.. note::
   The :mod:`Cookie` module has been renamed to :mod:`http.cookies` in Python
   3.  The :term:`2to3` tool will automatically adapt imports when converting
   your sources to Python 3.

**Source code:** :source:`Lib/Cookie.py`

--------------

The :mod:`Cookie` module defines classes for abstracting the concept of
cookies, an HTTP state management mechanism. It supports both simple string-only
cookies, and provides an abstraction for having any serializable data-type as
cookie value.

The module formerly strictly applied the parsing rules described in the
:rfc:`2109` and :rfc:`2068` specifications.  It has since been discovered that
MSIE 3.0x doesn't follow the character rules outlined in those specs and also
many current day browsers and servers have relaxed parsing rules when comes to
Cookie handling.  As a result, the parsing rules used are a bit less strict.

The character set, :data:`string.ascii_letters`, :data:`string.digits` and
``!#$%&'*+-.^_`|~`` denote the set of valid characters allowed by this module
in Cookie name (as :attr:`~Morsel.key`).


.. note::

   On encountering an invalid cookie, :exc:`CookieError` is raised, so if your
   cookie data comes from a browser you should always prepare for invalid data
   and catch :exc:`CookieError` on parsing.


.. exception:: CookieError

   Exception failing because of :rfc:`2109` invalidity: incorrect attributes,
   incorrect :mailheader:`Set-Cookie` header, etc.


.. class:: BaseCookie([input])

   This class is a dictionary-like object whose keys are strings and whose values
   are :class:`Morsel` instances. Note that upon setting a key to a value, the
   value is first converted to a :class:`Morsel` containing the key and the value.

   If *input* is given, it is passed to the :meth:`load` method.


.. class:: SimpleCookie([input])

   This class derives from :class:`BaseCookie` and overrides :meth:`value_decode`
   and :meth:`value_encode` to be the identity and :func:`str` respectively.


.. class:: SerialCookie([input])

   This class derives from :class:`BaseCookie` and overrides :meth:`value_decode`
   and :meth:`value_encode` to be the :func:`pickle.loads` and
   :func:`pickle.dumps`.

   .. deprecated:: 2.3
      Reading pickled values from untrusted cookie data is a huge security hole, as
      pickle strings can be crafted to cause arbitrary code to execute on your server.
      It is supported for backwards compatibility only, and may eventually go away.


.. class:: SmartCookie([input])

   This class derives from :class:`BaseCookie`. It overrides :meth:`value_decode`
   to be :func:`pickle.loads` if it is a valid pickle, and otherwise the value
   itself. It overrides :meth:`value_encode` to be :func:`pickle.dumps` unless it
   is a string, in which case it returns the value itself.

   .. deprecated:: 2.3
      The same security warning from :class:`SerialCookie` applies here.

A further security note is warranted.  For backwards compatibility, the
:mod:`Cookie` module exports a class named :class:`~Cookie.Cookie` which is
just an alias for :class:`SmartCookie`.  This is probably a mistake and will
likely be removed in a future version.  You should not use the
:class:`~Cookie.Cookie` class in your applications, for the same reason why
you should not use the :class:`SerialCookie` class.


.. seealso::

   Module :mod:`cookielib`
      HTTP cookie handling for web *clients*.  The :mod:`cookielib` and :mod:`Cookie`
      modules do not depend on each other.

   :rfc:`2109` - HTTP State Management Mechanism
      This is the state management specification implemented by this module.


.. _cookie-objects:

Cookie Objects
--------------


.. method:: BaseCookie.value_decode(val)

   Return a decoded value from a string representation. Return value can be any
   type. This method does nothing in :class:`BaseCookie` --- it exists so it can be
   overridden.


.. method:: BaseCookie.value_encode(val)

   Return an encoded value. *val* can be any type, but return value must be a
   string. This method does nothing in :class:`BaseCookie` --- it exists so it can
   be overridden.

   In general, it should be the case that :meth:`value_encode` and
   :meth:`value_decode` are inverses on the range of *value_decode*.


.. method:: BaseCookie.output([attrs[, header[, sep]]])

   Return a string representation suitable to be sent as HTTP headers. *attrs* and
   *header* are sent to each :class:`Morsel`'s :meth:`output` method. *sep* is used
   to join the headers together, and is by default the combination ``'\r\n'``
   (CRLF).

   .. versionchanged:: 2.5
      The default separator has been changed from ``'\n'`` to match the cookie
      specification.


.. method:: BaseCookie.js_output([attrs])

   Return an embeddable JavaScript snippet, which, if run on a browser which
   supports JavaScript, will act the same as if the HTTP headers was sent.

   The meaning for *attrs* is the same as in :meth:`output`.


.. method:: BaseCookie.load(rawdata)

   If *rawdata* is a string, parse it as an ``HTTP_COOKIE`` and add the values
   found there as :class:`Morsel`\ s. If it is a dictionary, it is equivalent to::

      for k, v in rawdata.items():
          cookie[k] = v


.. _morsel-objects:

Morsel Objects
--------------


.. class:: Morsel

   Abstract a key/value pair, which has some :rfc:`2109` attributes.

   Morsels are dictionary-like objects, whose set of keys is constant --- the valid
   :rfc:`2109` attributes, which are

   * ``expires``
   * ``path``
   * ``comment``
   * ``domain``
   * ``max-age``
   * ``secure``
   * ``version``
   * ``httponly``

   The attribute :attr:`httponly` specifies that the cookie is only transferred
   in HTTP requests, and is not accessible through JavaScript. This is intended
   to mitigate some forms of cross-site scripting.

   The keys are case-insensitive.

   .. versionadded:: 2.6
      The :attr:`httponly` attribute was added.


.. attribute:: Morsel.value

   The value of the cookie.


.. attribute:: Morsel.coded_value

   The encoded value of the cookie --- this is what should be sent.


.. attribute:: Morsel.key

   The name of the cookie.


.. method:: Morsel.set(key, value, coded_value)

   Set the *key*, *value* and *coded_value* attributes.


.. method:: Morsel.isReservedKey(K)

   Whether *K* is a member of the set of keys of a :class:`Morsel`.


.. method:: Morsel.output([attrs[, header]])

   Return a string representation of the Morsel, suitable to be sent as an HTTP
   header. By default, all the attributes are included, unless *attrs* is given, in
   which case it should be a list of attributes to use. *header* is by default
   ``"Set-Cookie:"``.


.. method:: Morsel.js_output([attrs])

   Return an embeddable JavaScript snippet, which, if run on a browser which
   supports JavaScript, will act the same as if the HTTP header was sent.

   The meaning for *attrs* is the same as in :meth:`output`.


.. method:: Morsel.OutputString([attrs])

   Return a string representing the Morsel, without any surrounding HTTP or
   JavaScript.

   The meaning for *attrs* is the same as in :meth:`output`.


.. _cookie-example:

Example
-------

The following example demonstrates how to use the :mod:`Cookie` module.

.. doctest::
   :options: +NORMALIZE_WHITESPACE

   >>> import Cookie
   >>> C = Cookie.SimpleCookie()
   >>> C["fig"] = "newton"
   >>> C["sugar"] = "wafer"
   >>> print C # generate HTTP headers
   Set-Cookie: fig=newton
   Set-Cookie: sugar=wafer
   >>> print C.output() # same thing
   Set-Cookie: fig=newton
   Set-Cookie: sugar=wafer
   >>> C = Cookie.SimpleCookie()
   >>> C["rocky"] = "road"
   >>> C["rocky"]["path"] = "/cookie"
   >>> print C.output(header="Cookie:")
   Cookie: rocky=road; Path=/cookie
   >>> print C.output(attrs=[], header="Cookie:")
   Cookie: rocky=road
   >>> C = Cookie.SimpleCookie()
   >>> C.load("chips=ahoy; vienna=finger") # load from a string (HTTP header)
   >>> print C
   Set-Cookie: chips=ahoy
   Set-Cookie: vienna=finger
   >>> C = Cookie.SimpleCookie()
   >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";')
   >>> print C
   Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;"
   >>> C = Cookie.SimpleCookie()
   >>> C["oreo"] = "doublestuff"
   >>> C["oreo"]["path"] = "/"
   >>> print C
   Set-Cookie: oreo=doublestuff; Path=/
   >>> C["twix"] = "none for you"
   >>> C["twix"].value
   'none for you'
   >>> C = Cookie.SimpleCookie()
   >>> C["number"] = 7 # equivalent to C["number"] = str(7)
   >>> C["string"] = "seven"
   >>> C["number"].value
   '7'
   >>> C["string"].value
   'seven'
   >>> print C
   Set-Cookie: number=7
   Set-Cookie: string=seven
   >>> # SerialCookie and SmartCookie are deprecated
   >>> # using it can cause security loopholes in your code.
   >>> C = Cookie.SerialCookie()
   >>> C["number"] = 7
   >>> C["string"] = "seven"
   >>> C["number"].value
   7
   >>> C["string"].value
   'seven'
   >>> print C
   Set-Cookie: number="I7\012."
   Set-Cookie: string="S'seven'\012p1\012."
   >>> C = Cookie.SmartCookie()
   >>> C["number"] = 7
   >>> C["string"] = "seven"
   >>> C["number"].value
   7
   >>> C["string"].value
   'seven'
   >>> print C
   Set-Cookie: number="I7\012."
   Set-Cookie: string=seven