2010-06-04 13:22:16 +02:00
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Captcha Plugin Architecture
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===========================
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2010-06-04 12:57:57 +02:00
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This document contains design notes for the plone.app.discussion Captcha plugin
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architecture.
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Introduction
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------------
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When a Captcha plugin (e.g. plone.formwidget.captcha or
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plone.formwidget.recaptcha) is installed, plone.app.discussion
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extends the comment form with a Captcha field/widget and a Captcha validator.
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The form extender and validator are only registered if there is a plugin
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installed that claims to provide the "plone.app.discussion-captcha" feature in
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its configure.zcml file::
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<configure ...
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xmlns:meta="http://namespaces.zope.org/meta">
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<!-- Declare that plone.formwidget.captcha provides a Captcha field that
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can be used by plone.app.discussion to add a Captcha field to comment
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forms. -->
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<meta:provides feature="plone.app.discussion-captcha" />
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...
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</configure>
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For an example see:
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https://svn.plone.org/svn/plone/plone.formwidget.captcha/trunk/plone/formwidget/captcha/configure.zcml
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Currently plone.formwidget.captcha and plone.formwidget.recaptcha provide such a
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feature. If you want to write your own Captcha plugin, it has to provide this
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feature as well.
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CaptchaExtender
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---------------
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The CaptchaExtender class extends the comment form with a Captcha field and
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widget. The CaptchaExtender currently uses either the CaptchaFieldWidget from
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plone.formwidget.captcha or the ReCaptchaFieldWidget from
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plone.formwidget.recaptcha. If you want to write your own Captcha solution, you
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have to override the update() method of the CaptchaExtender or write your own
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CaptchaExtender class.
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CaptchaValidator
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----------------
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The CaptchaValidator class provides custom versions of the
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plone.formwidget.captcha and the plone.formwidget.recaptcha validators. It does
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this, because we want to be able to have more than one Captcha solution
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installed in one Plone instance. We also want to be able to easily switch
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between different Captcha implementations inside a single Plone instance.
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Therefore we have to check which Captcha solution is enabled in the discussion
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control panel and use only the selected Captcha validator. It is not enough to
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check if a Captcha plugin is just installed, because there could be more than
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one.
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We do two checks. First we check for a suitable Captcha solution (check for the
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plone.app.discussion-captcha feature, see notes above). Second, we check which
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Captcha solution is enabled in the discussion control panel and apply the
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corresponding field validator.
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