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.IX Title "CGI::Application::Plugin::CAPTCHA 3pm"
.TH CGI::Application::Plugin::CAPTCHA 3pm "2021-01-07" "perl v5.32.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.SH "NAME"
CGI::Application::Plugin::CAPTCHA \- Easily create, use, and verify CAPTCHAs in
CGI::Application\-based web applications.
.SH "VERSION"
.IX Header "VERSION"
Version 0.04
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& # 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 => [ \*(Aqttf\*(Aq, \*(Aqrect\*(Aq ],
\& 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. . .
\& 
(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"));
\& }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`CGI::Application::Plugin::CAPTCHA\*(C'\fR allows programmers to easily add and
verify CAPTCHAs in their CGI::Application\-derived web applications.
.PP
A \s-1CAPTCHA\s0 (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 \s-1OCR.\s0
.PP
CAPTCHAs are not a perfect solution. Any skilled, diligent cracker will
eventually be able to bypass a \s-1CAPTCHA,\s0 but it should be able to shut down
your average script-kiddie.
.PP
\&\f(CW\*(C`CGI::Application::Plugin::CAPTCHA\*(C'\fR 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.
.PP
When a \s-1CAPTCHA\s0 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),
\&\f(CW\*(C`captcha_verify()\*(C'\fR 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 \s-1CAPTCHA\s0 has been successfully entered, and we allow
the user to continue processing their form.
.PP
The checksum is generated by taking the string in question, and joining it with
a \s-1SECRET.\s0 We then generate an \s-1SHA1\s0 hex digest of the resulting string. The
end user will not be able to generate their own checksums to bypass the \s-1CAPTCHA\s0
check, because they do not know the value of our \s-1SECRET.\s0 This means it is
important to choose a good value for your \s-1SECRET.\s0
.PP
An easy way to generate a relatively good secret is to run the following perl
snippet:
.PP
.Vb 1
\& perl \-MDigest::SHA=sha1_base64 \-le \*(Aqprint sha1_base64($$,time(),rand(9999))\*(Aq
.Ve
.PP
The author recognizes that the transmission of a cookie with the \s-1CAPTCHA\s0 image
may not be a popular decision, and welcomes any patches from those who can
provide an equally easy-to-implement solution.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "\fBcaptcha_config()\fP"
.IX Subsection "captcha_config()"
This method is used to customize how new \s-1CAPTCHA\s0 images will be created.
Values specified here are passed along to the appropriate functions in
GD::SecurityImage when a new \s-1CAPTCHA\s0 is created.
.PP
It is recommended that you call \f(CW\*(C`captcha_config()\*(C'\fR in the \f(CW\*(C`cgiapp_init()\*(C'\fR
method of your CGI::Application base class, and in the \f(CW\*(C`setup()\*(C'\fR method of
any derived applications.
.PP
The following parameters are currently accepted:
.PP
\fI\s-1IMAGE_OPTIONS\s0\fR
.IX Subsection "IMAGE_OPTIONS"
.PP
This specifies what options will be passed to the constructor of
GD::SecurityImage. Please see the documentation for GD::SecurityImage
for more information.
.PP
\fI\s-1CREATE_OPTIONS\s0\fR
.IX Subsection "CREATE_OPTIONS"
.PP
This specifies what options will be passed to the \f(CW\*(C`create()\*(C'\fR method of
GD::SecurityImage. Please see the documentation for GD::SecurityImage
for more information.
.PP
\fI\s-1PARTICLE_OPTIONS\s0\fR
.IX Subsection "PARTICLE_OPTIONS"
.PP
This specifies what options will be passed to the \f(CW\*(C`particle()\*(C'\fR method of
GD::SecurityImage. Please see the documentation for GD::SecurityImage
for more information.
.PP
\fI\s-1SECRET\s0\fR
.IX Subsection "SECRET"
.PP
This specifies the secret that will be used when generating the checksum hash.
.SS "\fBcaptcha_create()\fP"
.IX Subsection "captcha_create()"
Creates the \s-1CAPTCHA\s0 image, and return a cookie with the encrypted hash of the
random string. Takes no arguments.
.PP
The cookie created in this method is named \f(CW\*(C`hash\*(C'\fR, and contains only the
encrypted hash. Future versions of this module will allow you to specify
cookie options in greater detail.
.SS "\fBcaptcha_verify()\fP"
.IX Subsection "captcha_verify()"
Verifies that the value entered by the user matches what was in the \s-1CAPTCHA\s0
image. Argument 1 is the encrypted hash from the cookie sent by
\&\f(CW\*(C`captcha_create()\*(C'\fR, and argument 2 is the value the user entered to verify
the \s-1CAPTCHA\s0 image. Returns true if the \s-1CAPTCHA\s0 was successfully verified, else
returns false.
.SH "AUTHOR"
.IX Header "AUTHOR"
Jason A. Crome, \f(CW\*(C`\*(C'\fR
.SH "TODO"
.IX Header "TODO"
.IP "\(bu" 4
Allow \f(CW\*(C`captcha_config()\*(C'\fR to take cookie configuration arguments.
.IP "\(bu" 4
Allow the plugin to actually create a run mode in your CGI::Application\-based
webapp without the developer having to manually create one.
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs or feature requests to
\&\f(CW\*(C`bug\-cgi\-application\-plugin\-captcha@rt.cpan.org\*(C'\fR, or through the web interface at
.
I will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
.SH "CONTRIBUTING"
.IX Header "CONTRIBUTING"
Patches, questions, and feedback are welcome.
.SH "ACKNOWLEDGEMENTS"
.IX Header "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.
.PP
Additional thanks to chorny and Cees for the various bug fixes and patches
they have submitted.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
CGI::Application
GD::SecurityImage
Wikipedia entry for \s-1CAPTCHA\s0 \-
.SH "COPYRIGHT & LICENSE"
.IX Header "COPYRIGHT & LICENSE"
Copyright 2005\-2011 Jason A. Crome, all rights reserved.
.PP
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.