Scrubber(3)

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

SYNOPSIS
    #!/usr/bin/perl -w
    use HTML::Scrubber;
    use strict;
                                                                            #
    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>
    ];
                                                                            #
    my $scrubber = HTML::Scrubber->new( allow => [ qw[ p b i u hr br ] ] ); #
                                                                            #
    print $scrubber->scrub($html);                                          #
                                                                            #
    $scrubber->deny( qw[ p b i u hr br ] );                                 #
                                                                            #
    print $scrubber->scrub($html);                                          #
                                                                            #

DESCRIPTION
If you wanna "scrub" or "sanitize" html input in a reliable an 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.

  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
        },
        b => 1,
        ...
    );

  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;

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), 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{^(?!(?:java)?script)}i,
            'src'         => qr{^(?!(?:java)?script)}i,
    #   If your perl doesn't have qr
    #   just use a string with length greater than 1
            'cite'        => '(?i-xsm:^(?!(?:java)?script))',
            '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, HTML::Sanitizer.

BUGS/SUGGESTIONS/ETC
Please use https://rt.cpan.org/NoAuth/Bugs.html?Dist=HTML-Scrubber to report bugs/additions/etc or send mail to <bug-HTML-Scrubber#rt.cpan.org>.

AUTHOR
D. H. (PodMaster)

LICENSE
Copyright (c) 2003-2004 by D.H. (PodMaster). All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The LICENSE file contains the full text of the license.