CGI::Application::PlugUserCContributed PerCGI::Application::Plugin::CAPTCHA(3)NAMECGI::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::SHA1=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.
FUNCTIONScaptcha_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
<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.
perl v5.14.12011-07-CGI::Application::Plugin::CAPTCHA(3)
