Perl extension for scrubbing/sanitizing html
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README.md

Build Status Kwalitee status GitHub issues GitHub tag Cpan license Cpan version

NAME

HTML::Scrubber - Perl extension for scrubbing/sanitizing HTML

VERSION

version 0.17

SYNOPSIS

use HTML::Scrubber;

my $scrubber = HTML::Scrubber->new( allow => [ qw[ p b i u hr br ] ] );
print $scrubber->scrub('<p><b>bold</b> <em>missing</em></p>');
# output is: <p><b>bold</b> </p>

# more complex input
my $html = q[
<style type="text/css"> BAD { background: #666; color: #666;} </style>
<script language="javascript"> alert("Hello, I am EVIL!");    </script>
<HR>
    a   => <a href=1>link </a>
    br  => <br>
    b   => <B> bold </B>
    u   => <U> UNDERLINE </U>
];

print $scrubber->scrub($html);

$scrubber->deny( qw[ p b i u hr br ] );

print $scrubber->scrub($html);

DESCRIPTION

If you want to "scrub" or "sanitize" html input in a reliable and flexible fashion, then this module is for you.

I wasn't satisfied with HTML::Sanitizer because it is based on HTML::TreeBuilder, so I thought I'd write something similar that works directly with HTML::Parser.

METHODS

First a note on documentation: just study the EXAMPLE below. It's all the documentation you could need.

Also, be sure to read all the comments as well as How does it work?.

If you're new to perl, good luck to you.

new

my $scrubber = HTML::Scrubber->new( allow => [ qw[ p b i u hr br ] ] );

Build a new HTML::Scrubber. The arguments are the initial values for the following directives:-

  • default
  • allow
  • deny
  • rules
  • process
  • comment

comment

warn "comments are  ", $p->comment ? 'allowed' : 'not allowed';
$p->comment(0);  # off by default

process

warn "process instructions are  ", $p->process ? 'allowed' : 'not allowed';
$p->process(0);  # off by default

script

warn "script tags (and everything in between) are supressed"
    if $p->script;      # off by default
$p->script( 0 || 1 );

** Please note that this is implemented using HTML::Parser's ignore_elements function, so if script is set to true, all script tags encountered will be validated like all other tags.

style

warn "style tags (and everything in between) are supressed"
    if $p->style;       # off by default
$p->style( 0 || 1 );

** Please note that this is implemented using HTML::Parser's ignore_elements function, so if style is set to true, all style tags encountered will be validated like all other tags.

allow

$p->allow(qw[ t a g s ]);

deny

$p->deny(qw[ t a g s ]);

rules

$p->rules(
    img => {
        src => qr{^(?!http://)}i, # only relative image links allowed
        alt => 1,                 # alt attribute allowed
        '*' => 0,                 # deny all other attributes
    },
    a => {
        href => sub { ... },      # check or adjust with a callback
    },
    b => 1,
    ...
);

Updates a set of attribute rules. Each rule can be 1/0, a regular expression or a callback. Values longer than 1 char are treated as regexps. The callback is called with the following arguments: the current object, tag name, attribute name, and attribute value; the callback should return an empty list to drop the attribute, undef to keep it without a value, or a new scalar value.

default

print "default is ", $p->default();
$p->default(1);      # allow tags by default
$p->default(
    undef,           # don't change
    {                # default attribute rules
        '*' => 1,    # allow attributes by default
    }
);

scrub_file

$html = $scrubber->scrub_file('foo.html');   ## returns giant string
die "Eeek $!" unless defined $html;  ## opening foo.html may have failed
$scrubber->scrub_file('foo.html', 'new.html') or die "Eeek $!";
$scrubber->scrub_file('foo.html', *STDOUT)
    or die "Eeek $!"
        if fileno STDOUT;

scrub

print $scrubber->scrub($html);  ## returns giant string
$scrubber->scrub($html, 'new.html') or die "Eeek $!";
$scrubber->scrub($html', *STDOUT)
    or die "Eeek $!"
        if fileno STDOUT;

default handler, used by both _scrub and _scrub_fh. Moved all the common code (basically all of it) into a single routine for ease of maintenance.

default handler, does the scrubbing if we're scrubbing out to a file. Now calls _scrub_str and pushes that out to a file.

default handler, does the scrubbing if we're returning a giant string. Now calls _scrub_str and appends that to the output string.

How does it work?

When a tag is encountered, HTML::Scrubber allows/denies the tag using the explicit rule if one exists.

If no explicit rule exists, Scrubber applies the default rule.

If an explicit rule exists, but it's a simple rule(1), then the default attribute rule is applied.

EXAMPLE

#!/usr/bin/perl -w
use HTML::Scrubber;
use strict;

my @allow = qw[ br hr b a ];

my @rules = (
    script => 0,
    img    => {
        src => qr{^(?!http://)}i,    # only relative image links allowed
        alt => 1,                    # alt attribute allowed
        '*' => 0,                    # deny all other attributes
    },
);

my @default = (
    0 =>                             # default rule, deny all tags
        {
        '*'    => 1,                             # default rule, allow all attributes
        'href' => qr{^(?:http|https|ftp)://}i,
        'src'  => qr{^(?:http|https|ftp)://}i,

        #   If your perl doesn't have qr
        #   just use a string with length greater than 1
        'cite'        => '(?i-xsm:^(?:http|https|ftp):)',
        'language'    => 0,
        'name'        => 1,                                 # could be sneaky, but hey ;)
        'onblur'      => 0,
        'onchange'    => 0,
        'onclick'     => 0,
        'ondblclick'  => 0,
        'onerror'     => 0,
        'onfocus'     => 0,
        'onkeydown'   => 0,
        'onkeypress'  => 0,
        'onkeyup'     => 0,
        'onload'      => 0,
        'onmousedown' => 0,
        'onmousemove' => 0,
        'onmouseout'  => 0,
        'onmouseover' => 0,
        'onmouseup'   => 0,
        'onreset'     => 0,
        'onselect'    => 0,
        'onsubmit'    => 0,
        'onunload'    => 0,
        'src'         => 0,
        'type'        => 0,
        }
);

my $scrubber = HTML::Scrubber->new();
$scrubber->allow(@allow);
$scrubber->rules(@rules);    # key/value pairs
$scrubber->default(@default);
$scrubber->comment(1);       # 1 allow, 0 deny

## preferred way to create the same object
$scrubber = HTML::Scrubber->new(
    allow   => \@allow,
    rules   => \@rules,
    default => \@default,
    comment => 1,
    process => 0,
);

require Data::Dumper, die Data::Dumper::Dumper($scrubber) if @ARGV;

my $it = q[
    <?php   echo(" EVIL EVIL EVIL "); ?>    <!-- asdf -->
    <hr>
    <I FAKE="attribute" > IN ITALICS WITH FAKE="attribute" </I><br>
    <B> IN BOLD </B><br>
    <A NAME="evil">
        <A HREF="javascript:alert('die die die');">HREF=JAVA &lt;!&gt;</A>
        <br>
        <A HREF="image/bigone.jpg" ONMOUSEOVER="alert('die die die');">
            <IMG SRC="image/smallone.jpg" ALT="ONMOUSEOVER JAVASCRIPT">
        </A>
    </A> <br>
];

print "#original text", $/, $it, $/;
print
    "#scrubbed text (default ", $scrubber->default(),    # no arguments returns the current value
    " comment ", $scrubber->comment(), " process ", $scrubber->process(), " )", $/, $scrubber->scrub($it), $/;

$scrubber->default(1);                                   # allow all tags by default
$scrubber->comment(0);                                   # deny comments

print
    "#scrubbed text (default ",
    $scrubber->default(),
    " comment ",
    $scrubber->comment(),
    " process ",
    $scrubber->process(),
    " )", $/,
    $scrubber->scrub($it),
    $/;

$scrubber->process(1);    # allow process instructions (dangerous)
$default[0] = 1;          # allow all tags by default
$default[1]->{'*'} = 0;   # deny all attributes by default
$scrubber->default(@default);    # set the default again

print
    "#scrubbed text (default ",
    $scrubber->default(),
    " comment ",
    $scrubber->comment(),
    " process ",
    $scrubber->process(),
    " )", $/,
    $scrubber->scrub($it),
    $/;

FUN

If you have Test::Inline (and you've installed HTML::Scrubber), try

pod2test Scrubber.pm >scrubber.t
perl scrubber.t

SEE ALSO

HTML::Parser, Test::Inline.

The HTML::Sanitizer module is no longer available on CPAN.

VERSION REQUIREMENTS

As of version 0.14 I have added a perl minimum version requirement of 5.8. This is basically due to failures on the smokers perl 5.6 installations - which appears to be down to installation mechanisms and requirements.

Since I don't want to spend the time supporting a version that is so old (and may not work for reasons on UTF support etc), I have added a use 5.008; to the main module.

If this is problematic I am very willing to accept patches to fix this up, although I do not personally see a good reason to support a release that has been obsolete for 13 years.

CONTRIBUTING

If you want to contribute to the development of this module, the code is on GitHub. You'll need a perl environment with Dist::Zilla, and if you're just getting started, there's some documentation on using Vagrant and Perlbrew here.

There is now a .perltidyrc and a .tidyallrc file within the repository for the standard perltidy settings used - I will apply these before new releases. Please do not let formatting prevent you from sending in patches etc - this can be sorted out as part of the release process. Info on tidyall can be found at https://metacpan.org/pod/distribution/Code-TidyAll/bin/tidyall.

AUTHORS

COPYRIGHT AND LICENSE

This software is copyright (c) 2017 by Ruslan Zakirov, Nigel Metheringham, 2003-2004 D. H.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

SUPPORT

Perldoc

You can find documentation for this module with the perldoc command.

perldoc HTML::Scrubber

Websites

The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources.

Bugs / Feature Requests

Please report any bugs or feature requests by email to bug-html-scrubber at rt.cpan.org, or through the web interface at https://rt.cpan.org/Public/Bug/Report.html?Queue=HTML-Scrubber. You will be automatically notified of any progress on the request by the system.

Source Code

The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :)

https://github.com/nigelm/html-scrubber

git clone https://github.com/nigelm/html-scrubber.git

CONTRIBUTORS