Captcha(3pm)

NAME
Authen::Captcha - Perl extension for creating captcha's to verify the human element in transactions.

SYNOPSIS
  use Authen::Captcha;

  # create a new object
  my $captcha = Authen::Captcha->new();

  # set the data_folder. contains flatfile db to maintain state
  $captcha->data_folder('/some/folder');

  # set directory to hold publicly accessible images
  $captcha->output_folder('/some/http/folder');

  # Alternitively, any of the methods to set variables may also be
  # used directly in the constructor

  my $captcha = Authen::Captcha->new(
    data_folder => '/some/folder',
    output_folder => '/some/http/folder',
    );

  # create a captcha. Image filename is "$token.png"
  my $token = $captcha->generate_code($number_of_characters);

  # check for a valid submitted captcha
  #   $code is the submitted letter combination guess from the user
  #   $token is the submitted token from the user (that we gave them)
  my $results = $captcha->check_code($code,$token);
  # $results will be one of:
  #          1 : Passed
  #          0 : Code not checked (file error)
  #         -1 : Failed: code expired
  #         -2 : Failed: invalid code (not in database)
  #         -3 : Failed: invalid code (code does not match token)
  ##############

WARNING
The captcha produced by this module is rather weak compared to other modules available. You are advised to update to GD::SecurityImage, which provides API-compatible interface in GD::SecurityImage::AC module.

ABSTRACT
Authen::Captcha provides an object oriented interface to captcha file creations. Captcha stands for Completely Automated Public Turing test to tell Computers and Humans Apart. A Captcha is a program that can generate and grade tests that:

    - most humans can pass.
    - current computer programs can't pass

The most common form is an image file containing distorted text, which humans are adept at reading, and computers (generally) do a poor job. This module currently implements that method. We plan to add other methods, such as distorted sound files, and plain text riddles.

REQUIRES
    GD          (see http://search.cpan.org/~lds/GD-2.11/)
    Digest::MD5 (standard perl module)

In most common situations, you'll also want to have:

 A web server (untested on windows, but it should work)
 cgi-bin or mod-perl access
 Perl: Perl 5.00503 or later must be installed on the web server.
 GD.pm (with PNG support)

INSTALLATION
Download the zipped tar file from:

    http://search.cpan.org/search?dist=Authen-Captcha

Unzip the module as follows or use winzip:

    tar -zxvf Authen-Captcha-1.xxx.tar.gz

The module can be installed using the standard Perl procedure:

    perl Makefile.PL
    make
    make test
    make install    # you need to be root

Windows users without a working "make" can get nmake from:

    ftp://ftp.microsoft.com/Softlib/MSLFILES/nmake15.exe

METHODS

  MAIN METHODS

"$captcha = Authen::Captcha->new();"
    This creates a new Captcha object. Optionally, you can pass in a hash with configuration information. See the method descriptions for more detail on what they mean.

       data_folder => '/some/folder', # required
       output_folder => '/some/http/folder', # required
       expire => 300, # optional. default 300
       width =>  25, # optional. default 25
       height => 35, # optional. default 35
       images_folder => '/some/folder', # optional. default to lib dir
       keep_failures => 0, # optional, defaults to 0(false)
       debug => 0, # optional. default 0

"$token = $captcha->generate_code( $number_of_characters );"
    Creates a captcha. Image filename is "$token.png"

    It can also be called in array context to retrieve the string of characters used to generate the captcha (the string the user is expected to respond with). This is useful for debugging. ex.

    "($token,$chars) = $captcha->generate_code( $number_of_characters );"

"$results = $captcha->check_code($code,$token);"
    check for a valid submitted captcha

    $code is the submitted letter combination guess from the user

    $token is the submitted token from the user (that we gave them)

    If the $code and $token are correct, the image file and database entry will be removed.

    If the $token matches one in the database, and "keep_failures" is false (the default), the image file and database entry will be removed to avoid repeated attempts on the same captcha.

    $results will be one of:

        1 : Passed
        0 : Code not checked (file error)
       -1 : Failed: code expired
       -2 : Failed: invalid code (not in database)
       -3 : Failed: invalid code (code does not match token)

  ACCESSOR METHODS

"$captcha->data_folder( '/some/folder' );"
    Required. Sets the directory to hold the flatfile database that will be used to store the current non-expired valid captcha tokens. Must be writable by the process running the script (usually the web server user, which is usually either "apache" or "http"), but should not be accessible to the end user.

"$captcha->output_folder( '/some/folder' );"
    Required. Sets the directory to hold the generated Captcha image files. This is usually a web accessible directory so that the user can view the images in here, but it doesn't have to be web accessible (you could be attaching the images to an e-mail for some verification, or some other Captcha implementation). Must be writable by the process running the script (usually the web server user, which is usually either "apache" or "http").

"$captcha->images_folder( '/some/folder' );"
    Optional, and may greatly affect the results... use with caution. Allows you to override the default character graphic png's and backgrounds with your own set of graphics. These are used in the generation of the final captcha image file. The defaults are held in:
        [lib install dir]/Authen/Captcha/images

"$captcha->expire( 300 );"
    Optional. Sets the number of seconds this captcha will remain valid. This means that the created captcha's will not remain valid forever, just as long as you want them to be active. Set to an appropriate value for your application. Defaults to 300.

"$captcha->width( 25 );"
    Optional. Number of pixels high for the character graphics. Defaults to 25.

"$captcha->height( 35 );"
    Optional. Number of pixels wide for the character graphics. Defaults to 35.

"$captcha->keep_failures( [0|1] );"
    Optional. Defaults to zero. This option controls whether or not the captcha will remain valid after a failed attempt. By default, we only allow one attempt to solve it. This greatly reduces the possibility that a bot could brute force a correct answer. Change it at your own risk.

"$captcha->debug( [0|1|2] );"
    Optional. Sets the debugging bit. 1 turns it on, 0 turns it off. 2 will print out verbose messages to STDERR.

TODO
sound file captcha: Incorporating distorted sound file creation.

SEE ALSO
The Captcha project:
    http://www.captcha.net/

The origonal perl script this came from:
    http://www.firstproductions.com/cgi/

AUTHORS
Seth T. Jackson, <sjackson@purifieddata.net>

Josh I. Miller, <jmiller@purifieddata.net>

First Productions, Inc. created the cgi-script distributed under the GPL which was used as the basis for this module. Much work has gone into making this more robust, and suitable for other applications, but much of the origonal code remains.

Fixes were reported and contributed by various people, see Changes file for a complete list.

COPYRIGHT AND LICENSE
Copyright 2003, First Productions, Inc. (FIRSTPRODUCTIONS HUMAN TEST 1.0)

Copyright 2003 by Seth Jackson

Copyright 2012 by Paolo Rossi, Lubomir Rintel, Chris Dunlop, Gert Schepens and Ernesto Hernández-Novich

This library is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. (see license.txt).

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA