plone.protect 2.0.3

Security for browser forms

Introduction

This package contains utilities that can help to protect parts of Plone or applications build on top of the Plone framework.

1. Restricting to HTTP POST

a) Using decorator

If you only need to allow HTTP POST requests you can use the PostOnly checker:

from plone.protect import PostOnly
from plone.protect import protect

@protect(PostOnly)
def manage_doSomething(self, param, REQUEST=None):
    pass

This checker only operators on HTTP requests; other types of requests are not checked.

b) Passing request to a function validator

Simply:

from plone.protect import PostOnly

...
PostOnly(self.context.REQUEST)
...

2. Form authentication (CSRF)

A common problem in web applications is Cross Site Request Forgery or CSRF. This is an attack method in which an attacker tricks a browser to do a HTTP form submit to another site. To do this the attacker needs to know the exact form parameters. Form authentication is a method to make it impossible for an attacker to predict those parameters by adding an extra authenticator which can be verified.

Generating the token

To use the form authenticator you first need to insert it into your form. This can be done using a simple TAL statement inside your form:

<span tal:replace="structure context/@@authenticator/authenticator"/>

this will produce a HTML input element with the authentication information.

Validating the token

a) ZCA way

Next you need to add logic somewhere to verify the authenticator. This can be done using a call to the authenticator view. For example:

authenticator=getMultiAdapter((context, request), name=u"authenticator")
if not authenticator.verify():
    raise Unauthorized

b) Using decorator

You can do the same thing more conveniently using the protect decorator:

from plone.protect import CheckAuthenticator
from plone.protect import protect

@protect(CheckAuthenticator)
def manage_doSomething(self, param, REQUEST=None):
    pass

c) Passing request to a function validator

Or just:

from plone.protect import CheckAuthenticator

...
CheckAuthenticator(self.context.REQUEST)
...

Protect decorator

The most common way to use plone.protect is through the protect decorator. This decorator takes a list of checkers as parameters: each checker will check a specific security aspect of the request. For example:

from plone.protect import protect
from plone.protect import PostOnly

@protect(PostOnly)
def SensitiveMethod(self, REQUEST=None):
    # This is only allowed with HTTP POST requests.

This relies on the protected method having a parameter called REQUEST (case sensitive).

Customized Form Authentication

If you’d like use a different authentication token for different forms, you can provide an extra string to use with the token:

<tal:authenticator tal:define="authenticator context/@@authenticator">
  <span tal:replace="structure python: authenticator.authenticator('a-form-related-value')"/>
</tal:authenticator>

To verify:

authenticator=getMultiAdapter((context, request), name=u"authenticator")
if not authenticator.verify('a-form-related-value'):
    raise Unauthorized

With the decorator:

from plone.protect import CustomCheckAuthenticator
from plone.protect import protect

@protect(CustomCheckAuthenticator('a-form-related-value'))
def manage_doSomething(self, param, REQUEST=None):
    pass

Changelog

2.0.3 (2016-02-24)

Fixes:

• Added token to @@authenticator view. For forward compatibility with plone.protect 3. [maurits]

• Added plone.protect.interfaces.IDisableCSRFProtection from plone.protect 3. It has no effect in this version. It is only here to avoid having to do conditional imports when you want to disable csrf protection that is not actually in this version. [maurits]

2.0.2 (2012-12-09)

• Use constant time comparison to verify the authenticator. This is part of the fix for https://plone.org/products/plone/security/advisories/20121106/23 [davisagli]

• Add MANIFEST.in. [WouterVH]

• Add ability to customize the token created. [vangheem]

2.0 - 2010-07-18

• Update license to BSD following board decision. http://lists.plone.org/pipermail/membership/2009-August/001038.html [elro]

2.0a1 - 2009-11-14

• Removed deprecated AuthenticateForm class and zope.deprecation dependency. [hannosch]

• Avoid deprecation warning for the sha module in Python 2.6. [hannosch]

• Specify package dependencies [hannosch]

1.1 - 2008-06-02

• Add an optional GenericSetup profile to make it easier to install plone.protect. [mj]

1.0 - 2008-04-19

• The protect decorator had a serious design flaw which broke it. Added proper tests for it and fixed the problems. [wichert]

1.0rc1 - 2008-03-28

• Rename plone.app.protect to plone.protect: there is nothing Plone-specific about the functionality in this package and it really should be used outside of Plone as well. [wichert]

• Made utils.protect work with Zope >= 2.11. [stefan]

1.0b1 - March 7, 2008

• Refactor the code to offer a generic protect decorator for methods which takes a list of checkers as options. Add checkers for both the authenticator verification and HTTP POST-only. [wichert]

1.0a1 - January 27, 2008

• Initial release [wichert]