JCaptcha Plugin

Last updated by pkprasad82 1 year ago

JCaptcha Plugin

JCaptcha

JCaptcha is an open source (LGPL) captcha solution. JCaptcha provides visual and audio challenges and could be extended to provide different kinds of challenges if you desire.

Versions

||Version||Minimum Grails Version||Notes|| | 0.1 | 0.6 | | | 0.2 | 1.0-RC1 | |

The Plugin

The Grails JCaptcha plugin provides an easy way to define Captchas, display them and verify the response.

Installation

The plugin is available from the official repository so can be installed via …

grails install-plugin jcaptcha

Usage

Defining Captchas

Captchas are defined in the grails-app/conf/Config.groovy file.

log4j {
    /* log4j config */
}jcaptchas {
    captcha1 = …
    captcha2 = …
}

Each jcaptcha.* entry must be an instance of CaptchaService which is responsible for generating challenges and verifying responses.

Some example Captchas …

import java.awt.Font
import java.awt.Colorimport com.octo.captcha.service.multitype.GenericManageableCaptchaService
import com.octo.captcha.engine.GenericCaptchaEngine
import com.octo.captcha.image.gimpy.GimpyFactory
import com.octo.captcha.component.word.wordgenerator.RandomWordGenerator
import com.octo.captcha.component.image.wordtoimage.ComposedWordToImage
import com.octo.captcha.component.image.fontgenerator.RandomFontGenerator
import com.octo.captcha.component.image.backgroundgenerator.GradientBackgroundGenerator
import com.octo.captcha.component.image.color.SingleColorGenerator
import com.octo.captcha.component.image.textpaster.NonLinearTextPaster
import com.octo.captcha.service.sound.DefaultManageableSoundCaptchaService
jcaptchas {
	imageCaptcha = new GenericManageableCaptchaService(
		new GenericCaptchaEngine(
			new GimpyFactory(
				new RandomWordGenerator(
					"abcdefghijklmnopqrstuvwxyz1234567890"
				),
				new ComposedWordToImage(
					new RandomFontGenerator(
						20, // min font size
						30, // max font size
						[new Font("Arial", 0, 10)] as Font[]
					),
					new GradientBackgroundGenerator(
						140, // width
						35, // height
						new SingleColorGenerator(new Color(0, 60, 0)),
						new SingleColorGenerator(new Color(20, 20, 20))
					),
					new NonLinearTextPaster(
						6, // minimal length of text
						6, // maximal length of text
						new Color(0, 255, 0)
					)
				)
			)
		),
		180, // minGuarantedStorageDelayInSeconds
		180000 // maxCaptchaStoreSize
	)
	soundCaptcha = new DefaultManageableSoundCaptchaService()
}

Construction/configuration of captcha services is part of JCaptcha itself so refer to the JCaptcha documentation on that.

JCaptcha Controller

The plugin installs a controller called 'JCaptchaController'. It's function is to render captcha challenges. It currently supports two rendering formats: jpeg and wav.

The controller supports URIs like {{jcaptcha/jpeg/<captchaname>}} and {{jcaptcha/wav/<captchaname>}} which will write the binary output to the output stream.

Make sure that you don't try and render image captchas as sound or vice versa. If you attempt this you will get an IllegalArgumentException.

JCaptcha Tags

The plugin makes tags available for jpeg and wav challenges.

<jcaptcha:jpeg name="<captchaname>" height="Xpx" width="Xpx" /> // results in an img tag
<jcaptcha:wav name="<captchaname>" autostart="0" /> // results in an embed tag

You can pass any other attributes that are accepted by the underlying HTML tags to the tags.

JCaptcha Service

The JCaptchaService class is responsible for obtaining the instances of CaptchaService defined in your config. It is also used for verifying responses to challenges.

class ExampleController
{
    def jcaptchaService    def index = {
        if (jcaptchaService.validateResponse("captchaName", session.id, params.captchaResponse))
        {
            /* User entered response correctly
        }
        else
        {
            /* User got it wrong, OR THEY ARE A BOT Let's get em.
        }
    }
}

Notice that you need to pass {{session.id}} to {{validateResponse}}. This is because the captcha service needs to match the response to the challenge to check the answer. The key between the two is {{session.id}}.

Example Application

Here is a fully functional example application that uses the JCaptcha plugin.