plone.protect 3.0.26

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 operates 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.

If you want to create the token value programmatically, use the following:

from plone.protect.authenticator import createToken
token = createToken()

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)
...

Headers

You can also pass in the token by using the header X-CSRF-TOKEN. This can be useful for AJAX requests.

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

Automatic CSRF Protection

Since version 3, plone.protect provides automatic CSRF protection. It does this by automatically including the auth token to all internal forms when the user requesting the page is logged in.

Additionally, whenever a particular request attempts to write to the ZODB, it’ll check for the existence of a correct auth token.

Allowing write on read programatically

When you need to allow a known write on read, you’ve got several options.

Adding a CSRF token to your links

If you’ve got a GET request that causes a known write on read, your first option should be to simply add a CSRF token to the URLs that result in that request. plone.protect provides the addTokenToUrl function for this purpose:

from plone.protect.utils import addTokenToUrl

url = addTokenToUrl(url)

If you just want to allow an object to be writable on a request…

You can use the safeWrite helper function:

from plone.protect.auto import safeWrite

safeWrite(myobj, request)

Marking the entire request as safe

Just add the IDisableCSRFProtection interface to the current request object:

from plone.protect.interfaces import IDisableCSRFProtection
from zope.interface import alsoProvides

alsoProvides(request, IDisableCSRFProtection)

Warning! When you do this, the current request is susceptible to CSRF exploits so do any required CSRF protection manually.

Clickjacking Protection

plone.protect also provides, by default, clickjacking protection since version 3.0.

To protect against this attack, plone employs the use of the X-Frame-Options header. plone.protect will set the X-Frame-Options value to SAMEORIGIN.

To customize this value, you can set it to a custom value for a custom view (e.g. self.request.response.setHeader('X-Frame-Options', 'ALLOWALL')), override it at your proxy server, or you can set the environment variable of PLONE_X_FRAME_OPTIONS to whatever value you’d like plone.protect to set this to globally.

You can opt out of this by making the environment variable empty.

Disable All Automatic CSRF Protection

To disable all automatic CSRF protection, set the environment variable PLONE_CSRF_DISABLED value to true.

WARNING! It is very dangerous to do this. Do not do this unless the zeo client with this setting is not public and you know what you are doing.

..note::

This doesn’t disable explicit and manual CSRF protection checks.

Fixing CSRF Protection failures in tests

If you get Unauthorized errors in tests due to unprotected form submission where normally automatic protection would be in place you can use the following blueprint to protect your forms:

from plone.protect.authenticator import createToken
from ..testing import MY_INTEGRATION_TESTING_LAYER
import unittest

class MyTest(unittest.TestCase):

    layer = MY_INTEGRATION_TESTING_LAYER

    def setUp(self):
        self.request = self.layer['request']
        # Disable plone.protect for these tests
        self.request.form['_authenticator'] = createToken()
        # Eventuelly you find this also useful
        self.request.environ['REQUEST_METHOD'] = 'POST'

Notes

This package monkey patches a number of modules in order to better handle CSRF protection:

- Archetypes add forms, add csrf
- Zope2 object locking support
- pluggable auth csrf protection

If you are using a proxy cache in front of your site, be aware that you will need to clear the entry for ++resource++protect.js every time you update this package or you will find issues with modals while editing content.

Compatibility

plone.protect version 3 was made for Plone 5. You can use it on Plone 4 for better protection, but you will need the plone4.csrffixes hotfix package as well. Otherwise you get needless warnings or errors. See the hotfix announcement and the hotfix page.

Changelog

3.0.26 (2017-08-04)

New features:

• Catch AttributeError on transform. [hvelarde]

3.0.25 (2017-07-18)

Bug fixes:

• Fix logging to no longer write traceback to stdout, but include it in the logging message instead. [jone]

3.0.24 (2017-07-03)

Bug fixes:

• Remove unittest2 dependency [kakshay21]

3.0.23 (2016-11-26)

Bug fixes:

• Allow confirm-action for all contexts, instead of only Plone Site root. This avoids an error when calling it on a subsite. Fixes issue #51. [maurits]

• Code Style: utf8-headers, import sorting, new style namespace declaration, autopep8 [jensens]

• Fix #57: Html must contain “body”, otherwise plone.protect breaks. [jensens]

3.0.22 (2016-11-17)

Bug fixes:

• avoid zope.globalrequest.getRequest() [tschorr]

3.0.21 (2016-10-05)

Bug fixes:

• Avoid regenerating image scale over and over in Plone 4. Avoid (unnoticed) error when refreshing lock in Plone 4, plus a few other cases that were handled by plone4.csrffixes. Fixes https://github.com/plone/plone.protect/issues/47 [maurits]

3.0.20 (2016-09-08)

Bug fixes:

• Only try the confirm view for urls that are in the portal. This applies PloneHotfix20160830. [maurits]

• Removed RedirectTo patch. The patch has been merged to Products.CMFFormController 3.0.7 (Plone 4.3 and 5.0) and 3.1.2 (Plone 5.1). Note that we are not requiring those versions in our setup.py, because the code in this package no longer needs it. [maurits]

3.0.19 (2016-08-19)

New:

• Added protect.js from plone4.csrffixes. This adds an X-CSRF-TOKEN header to ajax requests. Fixes https://github.com/plone/plone.protect/issues/42 [maurits]

Fixes:

• Use zope.interface decorator. [gforcada]

3.0.18 (2016-02-25)

Fixes:

• Fixed AttributeError when calling safeWrite on a TestRequest, because this has no environ.. [maurits]

3.0.17 (2015-12-07)

Fixes:

• Internationalized button in confirm.pt. [vincentfretin]

3.0.16 (2015-11-05)

Fixes:

• Make sure transforms don’t fail on redirects. [lgraf]

3.0.15 (2015-10-30)

• make sure to always compare content type with a string when checking if we should show the confirm-action view. [vangheem]

• Internationalized confirm.pt [vincentfretin]

• Disable editable border for @@confirm-action view. [lgraf]

• Make title and description show up on @@confirm-action view. [lgraf]

• Allow views to override ‘X-Frame-Options’ by setting the response header manually. [alecm]

• Avoid parsing redirect responses (this avoids a warning on the log files). [gforcada]

3.0.14 (2015-10-08)

• Handle TypeError caused by getToolByName on an invalid context [vangheem]

• You can opt out of clickjacking protection by setting the environment variable PLONE_X_FRAME_OPTIONS to an empty string. [maurits]

• Be more flexible in parsing the PLONE_CSRF_DISABLED environment variable. We are no longer case sensitive, and we accept true, t, yes, y, 1 as true values. [maurits]

• Avoid TypeError when checking the content-type header. [maurits]

3.0.13 (2015-10-07)

• Always force html serializer as the XHTML variant seems to cause character encoding issues [vangheem]

3.0.12 (2015-10-06)

• Do not check writes to temporary storage like session storage [davisagli]

3.0.11 (2015-10-06)

• play nicer with inline JavaScript [vangheem]

3.0.10 (2015-10-06)

• make imports backward compatible [vangheem]

3.0.9 (2015-09-27)

• patch pluggable auth with marmoset patch because the patch would not apply otherwise depending on somewhat-random import order [vangheem]

• get auto-csrf protection working on the zope root [vangheem]

3.0.8 (2015-09-20)

• conditionally patch Products.PluggableAuthService if needed [vangheem]

• Do not raise ComponentLookupError on transform [vangheem]

3.0.7 (2015-07-24)

• Fix pluggable auth CSRF warnings on zope root. Very difficult to reproduce. Just let plone.protect do it’s job also on zope root. [vangheem]

3.0.6 (2015-07-20)

• Just return if the request object is not valid. [vangheem]

3.0.5 (2015-07-20)

• fix pluggable auth CSRF warnings [vangheem]

• fix detecting safe object writes on non-GET requests [vangheem]

• instead of using _v_safe_write users should now use the safeWrite function in plone.protect.auto [vangheem]

3.0.4 (2015-05-13)

• patch locking functions to use _v_safe_write attribute [vangheem]

• Be able to use _v_safe_write attribute to specify objects are safe to write [vangheem]

3.0.3 (2015-03-30)

• handle zope root not having IKeyManager Utility and CRSF protection not being supported on zope root requests yet [vangheem]

3.0.2 (2015-03-13)

• Add ITransform.transformBytes for protect transform to fix compatibility with plone.app.blocks’ ESI-rendering [atsoukka]

3.0.1 (2014-11-01)

• auto CSRF protection: check for changes on all the storages [mamico]

• CSRF test fixed [mamico]

3.0.0 (2014-04-13)

• auto-rotate keyrings [vangheem]

• use specific keyring for protected forms [vangheem]

• add automatic clickjacking protection(thanks to Manish Bhattacharya) [vangheem]

• add automatic CSRF protection [vangheem]

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]