collective.honeypot 2.0

Introduction

This package gives honeypot protection for forms.

Use cases

Spammers have found you and are pounding various forms on your website. Prime victims are the join form, contact form, sendto form and comment form.

Maybe you have some captcha protection in place but spammers have found a way around it. Or you want to detect a spammer before doing a possibly time consuming validation.

You have noticed that some scripts send e-mails or add a comment even when they receive a GET instead of a POST request.

You do not want to put up any user unfriendly captchas, but do not want to make it easy for spammers either.

Or, rather differently, you wonder if you can temporarily disallow all POST requests while you are doing a big migration.

Idea

One anti-spam idea that has found adoption is a honeypot: adding a field that would never be filled in by a human. The reasoning is that spammers will likely fill in all fields in a form, for two reasons:

1. The bots do not know which fields are required, so they fill everything in, just to be sure.

2. After a successful submission, each field might be shown on the website, so they fill all fields to get their message in the face of unsuspecting visitors.

The field should be hidden so it does not distract humans. But: making the input type hidden could mean that a spammer ignores it and does not fill it in after all, so we hide it with css instead.

Some spambots seem to know a bit about Plone. They know which fields are required on a few forms in a standard Plone website without captchas, or they even know a way around validation. If we add an invisible field they will simply not use it. So: for a few explicitly selected forms we require that the invisible field is in the submitted form, although it must be empty.

Installation and usage

Add collective.honeypot to the eggs of your zope instance in your buildout config:

[instance]
eggs =
    collective.honeypot

Run buildout and start the zope instance.

What does this do?

• This registers overrides for several templates and scripts (using z3c.jbot).

• It adds those templates and scripts to the list of extra protected actions. This means that a POST request to these actions now must have the honeypot field and it must be empty.

Fixes

Some scripts in standard Plone happily add a comment or send an e-mail when you use a GET request. This package does not agree with that policy and has fixes to require a POST request.

When using z3c.jbot, the package detects which fixes are needed. Some add-ons may or may not be available, so we only load fixes that can be applied, especially for plone.app.discussion.

If you override a script or template in an own skin layer or via some zcml, then our fixes may have no effect, so you need to do a fix yourself.

So, what are the actual fixes that this package contains?

• Some forms may get the invisible honeypot field automatically. This package registers an override for the @@authenticator view from plone.protect that is used in several templates for csrf protection (cross site request forgery). So any template that already uses this, is automatically loading our honeypot field.

• plone.app.discussion:

  • Add the honeypot field to the ‘add comment’ form. This fix is only done when you load fixes.zcml.

  • The honeypot field is not required, because the ‘add comment’ form posts to the context, not to a specific action.

• Plone:

  • Require POST for the send_feedback_site and sendto scripts.

  • Add the honeypot field to the sendto_form and contact-info forms.

  • The register form is automatically protected by our @@authenticator override.

  • Require the honeypot field for the above actions and the join form, specifically: sendto_form, sendto, contact-info, send_feedback_site, register, join_form.

Protecting your own forms

In a form that you want to protect, you must add this:

<div tal:replace="structure context/@@honeypot_field|nothing" />

This is all that is needed to have the basic protection of an invisible field that captures spammers if they fill it in. A Forbidden exception is raised in that case.

Some forms may get this invisible field automatically. This package registers an override for the @@authenticator view from plone.protect that is used in several templates for csrf protection (cross site request forgery). So any template that already uses this, is automatically loading our honeypot field.

For extra protection, you can add the page on which the form appears to the EXTRA_PROTECTED_ACTIONS. This means that the Forbidden exception is also raised if the field is not submitted in the form at all. See the Configuration section.

Note that it would be nice to accept all posts from authenticated users, but our code is run too early in the Zope process: we cannot know yet if the user is logged in or not.

Configuration

There is no configuration that you can do within a Plone Site. That would be too easy to get wrong, possibly even disabling the means to undo the damage. Also, with multiple Plone Sites in one Zope instance this would get even trickier. So we chose a different approach.

You can configure settings via environment variables in the zope.conf of your zope instance. For testing you could set an environment variable in your command shell and start the zope instance and it will get picked up. But the usual way would be to do this in buildout.cfg:

[instance]
environment-vars =
    HONEYPOT_FIELD pooh
    EXTRA_PROTECTED_ACTIONS discussion_reply join_form sendto_form
    WHITELISTED_ACTIONS jq_reveal_email
    WHITELISTED_START jq_*
    IGNORED_FORM_FIELDS secret_field
    ACCEPTED_LOG_LEVEL info
    SPAMMER_LOG_LEVEL error
    DISALLOW_ALL_POSTS no

General notes:

• None of the options are required. It will work fine without any environment variables.

• Values are split on whitespace or comma.

• Any @ character gets automatically replaced by a space, to make it easier to reference @@some_view by simply some_view, as we always protect them both.

These are the supported variables:

HONEYPOT_FIELD

Name to use as input name of the honeypot field. If you give no value here, no honeypot checks are done, so you only get some logging. This is obviously not the main goal of this package, but it may be useful when you need to do some debugging. If you do not list the variable, you get the default value of protected_1. In case spammers learn about this package and do not fill in the standard name, you can change the name here.

EXTRA_PROTECTED_ACTIONS

For these form actions the honeypot field is required: the field must be in the posted request, though it of course still must be empty. If you add actions here but do not change the forms, they become unusable for visitors, which is not what you want. On the other hand, if you have a form that you no longer wish to use, you can add it here and it will stop functioning. For @@view simply use view and it will match both.

WHITELISTED_ACTIONS

These form actions are not checked. List here actions that are harmless, for example actions that load some data via an AJAX call. Generally, actions that change nothing in the database and do not send emails are safe to add here. If you add this environment variable but leave it empty, you override the default and do not whitelist anything. By default we whitelist these actions:

• at_validate_field (inline validation)

• atct_edit (edit form)

• edit (edit form)

• kssValidateField (inline validation)

• jq_reveal_email (zest.emailhider)

• z3cform_validate_field (inline validation)

WHITELISTED_START

Form actions starting with one of these strings are not checked. See WHITELISTED_ACTIONS for more info. If you have lots of harmless actions that start with jq_ you can add that string to this list. Regular expression are too easy to get wrong, so we do not support it.

IGNORED_FORM_FIELDS

We log information about POST requests, to allow a system admin to go through the log and discover posts that are obviously spam attempts but are not caught yet and need extra handling, perhaps an extra form that should get protection. This information may contain form fields that should be left secret or that are not interesting. No matter what you fill in here, we always ignore fields that contain the term password.

ACCEPTED_LOG_LEVEL

Log level for accepted posts. This accepts standard lower or upper case log levels: debug, info, warn, warning, error, critical. When an unknown level is used or the setting is empty, we fall back to the default: INFO.

SPAMMER_LOG_LEVEL

Log level for caught spammers. This accepts standard lower or upper case log levels: debug, info, warn, warning, error, critical. When an unknown level is used or the setting is empty, we fall back to the default: ERROR.

DISALLOW_ALL_POSTS

Set this to 1, on, true, or yes to disallow all POST requests. This may be handy if you want to effectively make a Plone Site read-only, for example in preparation of a security release or when you are doing a big migration in a new zope instance and want to keep the old instance alive for the time being. Note that, like the rest of the checks, this only has an effect in a Plone (or CMF) site, not in the Zope root.

When are the checks not done?

This package does not check fields on any GET requests, it actually blocks the GET requests on selected forms and requires a POST there. Hence the field checks only work on POST requests.

If you have made the HONEYPOT_FIELD configuration option empty, no honeypot checks are done, so you only get some logging.

If Zope does any traversal, only the original action is checked. For example:

• A visitor makes a POST request to a my_form action. The honeypot checks are done for that action.

• The my_form action may be an old-style CMF form controller action that calls a validation script validate_my_form. This validation script does not get honeypot checks.

• After validation, the action may do a traverse to a script do_action that does the real work, like changing the database or sending an email. This script does not get honeypot checks.

As an aside, if you have such a setup, you should make sure the do_action script calls a validation script too and only accepts POST requests. Otherwise a smart spammer can bypass the validate_my_form validation script by requesting the do_action script directly. And he can bypass the honeypot checks by using a GET request.

z3c.form

You can easily add a honeypot field to a z3c.form. Just add a TextLine field to your form Interface definition, set the widgetFactory to the widget that collective.honeypot supplies, and make it hidden. Something like this:

from collective.honeypot.z3cform.widget import HoneypotFieldWidget
from z3c.form import form, interfaces
from zope import schema
from zope.interface import Interface

class IHoneypot(Interface):
    # Keep field title empty so visitors do not see it.
    honeypot = schema.TextLine(title=u"", required=False)

class MyForm(form.Form):
    fields = form.field.Fields(IHoneypot)

    def update(self):
        self.fields['honeypot'].widgetFactory = HoneypotFieldWidget
        self.fields['honeypot'].mode = interfaces.HIDDEN_MODE

See collective/honeypot/discussion/z3cformextender.py for an example of how to extend an existing form, in this case the comment form in plone.app.discussion.

Compatibility

This works on Plone 5.2.

Changelog