CGI::Untaint 0.8
Perl
module
-
Part of CPAN
distribution
CGI-Untaint 0.8.
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 = 'MyRecipes',
}, $q->Vars );
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 = 'MyRecipes',
}, $q->Vars);
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.
See LOCAL 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.
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 $1
will return the untainted value required.
e.g. if you often extract single digit variables, you could create
package Mysite::CGI::Untaint::digit;
use base 'CGI::Untaint::object';
sub _untaint_re { qr/^(\d)$/ }
1;
You should specify the path to 'Mysite' in the INCLUDE_PATH configuration
option. (See new() above.)
When extract() is called CGI::Untaint will automatically 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 to $self->value)
e.g. in the above example, if you sometimes need to ensure that the
digit extracted is prime, you would supply:
sub is_valid { (1 x shift->value) !~ /^1?$|^(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
call
my $number = $handler->extract(-as_like_digit => 'value');
This package comes with two very simplistic handlers: 'integer' and
'printable'. To really make this work for you you either need to write,
or download from CPAN, other handlers. Currently available handlers from
CPAN include:
CGI::Untaint::creditcard
CGI::Untaint::date
CGI::Untaint::email
CGI::Untaint::uk_postcode
CGI::Untaint::url
If you create any others, please let me know and I'll include them here.
(Or, if you have requests for other handlers, let me know and I'll see
if I can create them).
None known yet.
CGI. perlsec.
Tony Bowden, <kasei@tmtm.com>.
I'd love to hear from you if you start using this. I'd particularly like
to hear any suggestions as to how to make it even better / easier etc.
Copyright (C) 2001 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.
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