CGI::Untaint - process CGI input parameters

      use CGI::Untaint;

      my $q = new CGI;
      my $handler = CGI::Untaint->new( $q->Vars );
      my $handler2 = CGI::Untaint->new({
            INCLUDE_PATH => 'My::Untaint',
      }, $apr->parms);

      my $name     = $handler->extract(-as_printable => 'name');
      my $homepage = $handler->extract(-as_url => 'homepage');

      my $postcode = $handler->extract(-as_postcode => 'address6');

      # Create your own handler...

      package MyRecipes::CGI::Untaint::legal_age;
      use base 'CGI::Untaint::integer';
      sub is_valid { 
        shift->value > 21;

      package main;
      my $age = $handler->extract(-as_legal_age => 'age');

    Dealing with large web based applications with multiple forms is a
    minefield. It's often hard enough to ensure you validate all your input
    at all, without having to worry about doing it in a consistent manner.
    If any of the validation rules change, you often have to alter them in
    many different places. And, if you want to operate taint-safe, then
    you're just adding even more headaches.

    This module provides a simple, convenient, abstracted and extensible
    manner for validating and untainting the input from web forms.

    You simply create a handler with a hash of your parameters (usually
    $q->Vars), and then iterate over the fields you wish to extract,
    performing whatever validations you choose. The resulting variable is
    guaranteed not only to be valid, but also untainted.

      my $handler  = CGI::Untaint->new( $q->Vars );
      my $handler2 = CGI::Untaint->new({
            INCLUDE_PATH => 'My::Untaint',
      }, $apr->parms);

    The simplest way to contruct an input handler is to pass a hash of
    parameters (usually $q->Vars) to new(). Each parameter will then be able
    to be extracted later by calling an extract() method on it.

    However, you may also pass a leading reference to a hash of
    configuration variables.

    Currently the only such variable supported is 'INCLUDE_PATH', which
    allows you to specify a local path in which to find extraction handlers.

      my $homepage = $handler->extract(-as_url => 'homepage');
      my $state = $handler->extract(-as_us_state => 'address4');
      my $state = $handler->extract(-as_like_us_state => 'address4');

    Once you have constructed your Input Handler, you call the 'extract'
    method on each piece of data with which you are concerned.

    The takes an -as_whatever flag to state what type of data you require.
    This will check that the input value correctly matches the required
    specification, and return an untainted value. It will then call the
    is_valid() method, where applicable, to ensure that this doesn't just
    _look_ like a valid value, but actually is one.

    If you want to skip this stage, then you can call -as_like_whatever
    which will perform the untainting but not the validation.

      my $error = $handler->error;

    If the validation failed, this will return the reason why.

    As well as as the handlers supplied with this module for extracting
    data, you may also create your own. In general these should inherit from
    'CGI::Untaint::object', and must provide an '_untaint_re' method which
    returns a compiled regular expression, suitably bracketed such that $1
    will return the untainted value required.

    e.g. if you often extract single digit variables, you could create

      package My::Untaint::digit;

      use base 'CGI::Untaint::object';

      sub _untaint_re { qr/^(\d)$/ }


    You should specify the path 'My::Untaint' in the INCLUDE_PATH
    configuration option. (See new() above.)

    When extract() is called CGI::Untaint will also check to see if you have
    an is_valid() method also, and if so will run this against the value
    extracted from the regular expression (available as $self->value).

    If this returns a true value, then the extracted value will be returned,
    otherwise we return undef.

    is_valid() can also modify the value being returned, by assigning

    e.g. in the above example, if you sometimes need to ensure that the
    digit extracted is prime, you would supply:

      sub is_valid { (1 x shift->value) !~ /^1?$|^(11+?)\1+$/ };

    Now, when users call extract(), it will also check that the value is
    valid(), i.e. prime:

      my $number = $handler->extract(-as_digit => 'value');

    A user wishing to skip the validation, but still ensure untainting can

      my $number = $handler->extract(-as_like_digit => 'value');

    If you create your own local handlers, then you may wish to explore
    Test::CGI::Untaint, available from the CPAN. This makes it very easy to
    write tests for your handler. (Thanks to Profero Ltd.)

    This package comes with the following simplistic handlers:

      printable  - a printable string
      integer    - an integer
      hex        - a hexadecimal number (as a string)

    To really make this work for you you either need to write, or download
    from CPAN, other handlers. Some of the handlers available on CPAN

      asin         - an Amazon ID
      boolean      - boolean value
      country      - a country code or name
      creditcard   - a credit card number
      date         - a date (into a Date::Simple)
      datetime     - a date (into a DateTime)
      email        - an email address
      hostname     - a DNS host name
      html         - sanitized HTML
      ipaddress    - an IP address
      isbn         - an ISBN
      uk_postcode  - a UK Postcode
      url          - a URL
      zipcode      - a US zipcode

    None known yet.

    CGI. perlsec. Test::CGI::Untaint.

    Tony Bowden

    Please direct all correspondence regarding this module to:

    Copyright (C) 2001-2005 Tony Bowden. All rights reserved.

    This module is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.