Captcha.pm

Captcha.pm is a Perl module which provides a simple CAPTCHA framework. It's written in a object oriented programming style. Session information is stored in a hashed DB file (/var/tmp/captcha.db by default).

Usage

From its inline documentation:

  1. Install Perl's GD library:
  2. Put Captcha.pm into /var/www/lib
  3. Create a CGI script /var/www/cgi-bin/captcha.pl which outputs a random CAPTCHA image: 
    #!/usr/bin/perl -w

use strict;
use warnings;
use FindBin qw($Bin);
use lib $Bin . "/../lib";
use Captcha;

new Captcha()->image();
  4. Create a CGI script /var/www/cgi-bin/order.pl which does the real work and therefore has to be protected by a CAPTCHA: 
    #!/usr/bin/perl -w

use strict;
use warnings;
use CGI;
use FindBin qw($Bin);
use lib $Bin . "/../lib";
use Captcha;

my $cgi = new CGI();
my $captcha = new Captcha();

if (!$captcha->ok($cgi->param("captcha"))) {
  # user entered a wrong captcha code -> print an error
  exit -1;
}

# do the real work, e.g. place the order, do some heavy computation, etc.
...
  5. Create a form which serves as start page and where the user has to fill out several fields, including the CAPTCHA: 
    <html>
<head>
<title>Place an order</title>
</head>
<body>
<form method="POST" action="/cgi-bin/order.pl">
... some other input fields ...
<div>
<p>Please solve the following equation:</p>
<img src="/cgi-bin/captcha.pl"> = <input type="text" name="captcha" size="4">
</div>
<input type="submit">
</form>
</body>
</html>
  6. Optionally, if your start page is a CGI script, too, you might want to use the link() method provided by this module: 
    #!/usr/bin/perl -w

use strict;
use warnings;
use CGI;
use FindBin qw($Bin);
use lib dirname($Bin) . "/../lib";
use Captcha;

my $cgi = new CGI();
my $captcha = new Captcha();

# ... print html form ...

print $captcha->link();

# ... print reminder of html form ...

You can override builtin defaults by providing the constructor one or more of these parameters:

ParameterDefaultInfo
dbfile/var/tmp/captcha.dbLocation of the session database file
cookiecaptcha_sidName of the session cookie
width200Width of the CAPTCHA image in pixels
height50Height of the CAPTCHA image in pixels
permitted_ips[]List of IP addresses which are allowed without any CAPTCHA code; simple string-like prefix match, e.g. "192.168." matches 192.168.0.0/16
bypass_funcundefReference to a (anonymous) function which will bypass CAPTCHA checking if it returns a true value
captcha_urlcaptcha.plURL of the CGI script which prints the CAPTCHA image
captcha_fieldcaptchaName of the form field which contains the CAPTCHA code entered by the user

Examples

Download Captcha.pm, captcha.pl, and captcha_test.pl from below. Save them to the cgi-bin folder on your webserver. Point your webbrowser to /cgi-bin/captcha_test.pl on your webserver.

Downloads