Captcha Plugin

A simple plugin for commenting with CAPTCHA™ test.

• Captcha.zip

Changes

• 0.01(2006-05-18):
• First release.
• 0.02(2006-05-19):
• Now can configure TTL for CAPTCHA tests from the plugin setting screen.
• 0.10(2006-10-04):
• Now can enable or disable CAPTCHA tests per-blog basis.
• Now can change the length of CAPTCHA test strings.
• Now can set a secret key for generating CAPTCHA codes.
• Captcha images can be placed under the user-specific directory. This is for someone who can make plugins directory be executable but not readable (it might be usual for most web-hosting services).
• 0.11(2006-10-05):
• Captcha plugin now employed Data::Dumper module for configuration object serialization.
• Meaningless caching for plugin data is removed.
• 0.11a(2006-10-05):
• Now Captcha plugin becomes compatible with Authen-Captcha distributed via CPAN, which doesn't support "secret" option.
• 0.12(2006-10-08):
• Now users can modify the template for showing CAPTCHA tests from the plugin setting screen. Be careful to modify this.
• 0.13(2006-10-17):
• Fix a bug for captcha-disabled blogs.

Overview

"Captcha Plugin" is an anti comment-spam plugin which generates and verifies CAPTCHA™ tests that most human commenters can easily pass but current spambots cannot pass.

Unlike well-known SCode plugin, Captcha plugin generates different CAPTCHA tests whenever commenters request commenting pages, and each tests have shorter time to live. So, I think, Captcha plugin is less exploitable by spammers than the predecessors.

Requirements

This plugin is supported on Movable Type 3.2 or later and requires the following Perl modules:

• Authen::Captcha
• GD

If you want to employ "secret key" feature, you must apply the following patch to Authen::Captcha.

• #7664: improve Authen::Captcha security

Installation

Installation process is not so hard.

• Download [attachment:wiki:DownloadableFiles:Captcha.zip Captcha.zip].
• Unpack the distribution in your Movable Type directory. You will get just one directory called "captcha" under your plugins directory.
• Check permissions for files and directories.
• plugins/captcha/captcha_js.cgi should be executable as a CGI script.
• plugins/captcha/data should be writable by CGI programs.
• plugins/captcha/images should be writable by CGI programs.

That's all. You'll see the Captcha plugin in the plugins listing in the system overview screen.

Usage

To use CAPTCHA tests, you will need to add the following line into your all commenting templates and rebuild them.

<script type="text/javascript" src="<$MTCaptchaJsURL$>"></script>

Each CAPTCHA tests has a time to live, and the default lifetime is 1 hour. To customize the lifetime, you will need to change "CAPTCHA TTL" from the blog plugin setting screen.

See Also

• http://code.google.com/p/ogawa/source/browse/trunk/captcha

License

This code is released under the Artistic License. The terms of the Artistic License are described at http://www.perl.com/language/misc/Artistic.html.

Author & Copyright

Copyright 2006, Hirotaka Ogawa (hirotaka.ogawa at gmail.com)