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Cookie --- HTTP state management

Cookie

Timothy O'Malley <timo@alum.mit.edu>

Moshe Zadka <moshez@zadka.site.co.il>

Note

The Cookie module has been renamed to http.cookies in Python 3.0. The 2to3 tool will automatically adapt imports when converting your sources to 3.0.

The 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 2109 and 2068 specifications. It has since been discovered that MSIE 3.0x doesn't follow the character rules outlined in those specs. As a result, the parsing rules used are a bit less strict.

Note

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

CookieError

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

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

If input is given, it is passed to the load method.

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

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

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.

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

2.3 The same security warning from SerialCookie applies here.

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

Module cookielib

HTTP cookie handling for web clients. The cookielib and Cookie modules do not depend on each other.

2109 - HTTP State Management Mechanism

This is the state management specification implemented by this module.

Cookie Objects

BaseCookie.value_decode(val)

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

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 BaseCookie --- it exists so it can be overridden

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

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

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

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

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 output.

BaseCookie.load(rawdata)

If rawdata is a string, parse it as an HTTP_COOKIE and add the values found there as Morsels. If it is a dictionary, it is equivalent to:

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

Morsel Objects

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

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

  • expires
  • path
  • comment
  • domain
  • max-age
  • secure
  • version
  • httponly

The attribute httponly specifies that the cookie is only transfered 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.

2.6 The httponly attribute was added.

Morsel.value

The value of the cookie.

Morsel.coded_value

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

Morsel.key

The name of the cookie.

Morsel.set(key, value, coded_value)

Set the key, value and coded_value members.

Morsel.isReservedKey(K)

Whether K is a member of the set of keys of a Morsel.

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:".

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 output.

Morsel.OutputString([attrs])

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

The meaning for attrs is the same as in output.

Example

The following example demonstrates how to use the Cookie module.

>>> 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="I7012." Set-Cookie: string="S'seven'012p1012." >>> C = Cookie.SmartCookie() >>> C["number"] = 7 >>> C["string"] = "seven" >>> C["number"].value 7 >>> C["string"].value 'seven' >>> print C Set-Cookie: number="I7012." Set-Cookie: string=seven