Provided by: libcgi-application-plugin-captcha-perl_0.04-4_all 
NAME
CGI::Application::Plugin::CAPTCHA - Easily create, use, and verify CAPTCHAs in
CGI::Application-based web applications.
VERSION
Version 0.04
SYNOPSIS
# In your CGI::Application-based web application module. . .
use CGI::Application::Plugin::CAPTCHA;
sub setup
{
my $self = shift;
$self->run_modes([ qw/
create
# Your other run modes go here
/]);
$self->captcha_config(
IMAGE_OPTIONS => {
width => 150,
height => 40,
lines => 10,
font => "/Library/Fonts/Arial",
ptsize => 18,
bgcolor => "#FFFF00",
},
CREATE_OPTIONS => [ 'ttf', 'rect' ],
PARTICLE_OPTIONS => [ 300 ],
);
}
# Create a run mode that calls the CAPTCHA creation method...
sub create
{
my $self = shift;
return $self->captcha_create;
}
# In a template far, far away. . .
<img src="/delight/Ident/create"> (to generate a CAPTCHA image)
# Back in your application, to verify the CAPTCHA...
sub some_other_runmode
{
my $self = shift;
my $request = $self->query;
return unless $self->captcha_verify($request->cookie("hash"), $request->param("verify"));
}
DESCRIPTION
"CGI::Application::Plugin::CAPTCHA" allows programmers to easily add and verify CAPTCHAs
in their CGI::Application-derived web applications.
A CAPTCHA (or Completely Automated Public Turing Test to Tell Computers and Humans Apart)
is an image with a random string of characters. A user must successfully enter the random
string in order to submit a form. This is a simple (yet annoying) procedure for humans to
complete, but one that is significantly more difficult for a form-stuffing script to
complete without having to integrate some sort of OCR.
CAPTCHAs are not a perfect solution. Any skilled, diligent cracker will eventually be
able to bypass a CAPTCHA, but it should be able to shut down your average script-kiddie.
"CGI::Application::Plugin::CAPTCHA" is a wrapper for GD::SecurityImage. It makes it more
convenient to access GD::SecurityImage functionality, and gives a more
CGI::Application-like way of doing it.
When a CAPTCHA is created with this module, raw image data is transmitted from your web
application to the client browser. A cookie containing a checksum is also transmitted
with the image. When the client submits their form for processing (along with their
verification of the random string), "captcha_verify()" generates a checksum of the
verification string the user entered. If the newly generated checksum matches the
checksum found in the cookie, we trust that the CAPTCHA has been successfully entered, and
we allow the user to continue processing their form.
The checksum is generated by taking the string in question, and joining it with a SECRET.
We then generate an SHA1 hex digest of the resulting string. The end user will not be
able to generate their own checksums to bypass the CAPTCHA check, because they do not know
the value of our SECRET. This means it is important to choose a good value for your
SECRET.
An easy way to generate a relatively good secret is to run the following perl snippet:
perl -MDigest::SHA=sha1_base64 -le 'print sha1_base64($$,time(),rand(9999))'
The author recognizes that the transmission of a cookie with the CAPTCHA image may not be
a popular decision, and welcomes any patches from those who can provide an equally easy-
to-implement solution.
FUNCTIONS
captcha_config()
This method is used to customize how new CAPTCHA images will be created. Values specified
here are passed along to the appropriate functions in GD::SecurityImage when a new CAPTCHA
is created.
It is recommended that you call "captcha_config()" in the "cgiapp_init()" method of your
CGI::Application base class, and in the "setup()" method of any derived applications.
The following parameters are currently accepted:
IMAGE_OPTIONS
This specifies what options will be passed to the constructor of GD::SecurityImage.
Please see the documentation for GD::SecurityImage for more information.
CREATE_OPTIONS
This specifies what options will be passed to the "create()" method of GD::SecurityImage.
Please see the documentation for GD::SecurityImage for more information.
PARTICLE_OPTIONS
This specifies what options will be passed to the "particle()" method of
GD::SecurityImage. Please see the documentation for GD::SecurityImage for more
information.
SECRET
This specifies the secret that will be used when generating the checksum hash.
captcha_create()
Creates the CAPTCHA image, and return a cookie with the encrypted hash of the random
string. Takes no arguments.
The cookie created in this method is named "hash", and contains only the encrypted hash.
Future versions of this module will allow you to specify cookie options in greater detail.
captcha_verify()
Verifies that the value entered by the user matches what was in the CAPTCHA image.
Argument 1 is the encrypted hash from the cookie sent by "captcha_create()", and argument
2 is the value the user entered to verify the CAPTCHA image. Returns true if the CAPTCHA
was successfully verified, else returns false.
AUTHOR
Jason A. Crome, "<cromedome@cpan.org>"
TODO
• Allow "captcha_config()" to take cookie configuration arguments.
• Allow the plugin to actually create a run mode in your CGI::Application-based webapp
without the developer having to manually create one.
BUGS
Please report any bugs or feature requests to
"bug-cgi-application-plugin-captcha@rt.cpan.org", or through the web interface at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=CGI-Application-Plugin-CAPTCHA>. I will
be notified, and then you'll automatically be notified of progress on your bug as I make
changes.
CONTRIBUTING
Patches, questions, and feedback are welcome.
ACKNOWLEDGEMENTS
A big thanks to Cees Hek for providing a great module for me to borrow code from
(CGI::Application::Plugin::Session), to Michael Peters and Tony Fraser for all of their
valuable input, and to the rest who contributed ideas and criticisms on the
CGI::Application mailing list.
Additional thanks to chorny and Cees for the various bug fixes and patches they have
submitted.
SEE ALSO
CGI::Application GD::SecurityImage Wikipedia entry for CAPTCHA -
<http://en.wikipedia.org/wiki/Captcha>
COPYRIGHT & LICENSE
Copyright 2005-2011 Jason A. Crome, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.