Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.
Awesome Lists | Featured Topics | Projects
https://github.com/oalders/html-restrict

HTML::Restrict - Strip away unwanted HTML tags
https://github.com/oalders/html-restrict
hacktoberfest parse perl strip-html unwanted-html-tags
Last synced: about 2 months ago
JSON representation
HTML::Restrict - Strip away unwanted HTML tags
Host: GitHub
URL: https://github.com/oalders/html-restrict
Owner: oalders
License: other
Created: 2009-09-16T21:40:05.000Z (over 15 years ago)
Default Branch: main
Last Pushed: 2024-09-03T23:08:21.000Z (4 months ago)
Last Synced: 2024-10-11T21:11:58.446Z (2 months ago)
Topics: hacktoberfest, parse, perl, strip-html, unwanted-html-tags
Language: Perl
Homepage:
Size: 229 KB
Stars: 10
Watchers: 5
Forks: 9
Open Issues: 5
Metadata Files:
- Readme: README.md
- Changelog: Changes
- License: LICENSE
Awesome Lists containing this project

README

        # NAME

HTML::Restrict - Strip unwanted HTML tags and attributes

# VERSION

version v3.0.2

# SYNOPSIS

    use HTML::Restrict;

    my $hr = HTML::Restrict->new();

    # use default rules to start with (strip away all HTML)

    my $processed = $hr->process('  i am bold  ');

    # $processed now equals: 'i am bold'

    # Now, a less restrictive example:

    $hr = HTML::Restrict->new(

        rules => {

            b   => [],

            img => [qw( src alt / )]

        }

    );

    my $html = q[hello ];

    $processed = $hr->process( $html );

    # $processed now equals: hello 

# DESCRIPTION

This module uses [HTML::Parser](https://metacpan.org/pod/HTML%3A%3AParser) to strip HTML from text in a restrictive

manner.  By default all HTML is restricted.  You may alter the default

behaviour by supplying your own tag rules.

# CONSTRUCTOR AND STARTUP

## new()

Creates and returns a new HTML::Restrict object.

    my $hr = HTML::Restrict->new()

HTML::Restrict doesn't require any params to be passed to new.  If your goal is

to remove all HTML from text, then no further setup is required.  Just pass

your text to the process() method and you're done:

    my $plain_text = $hr->process( $html );

If you need to set up specific rules, have a look at the params which

HTML::Restrict recognizes:

- `rules => \%rules`

    Sets the rules which will be used to process your data.  By default all HTML

    tags are off limits.  Use this argument to define the HTML elements and

    corresponding attributes you'd like to use.  Essentially, consider the default

    behaviour to be:

        rules => {}

    Rules should be passed as a HASHREF of allowed tags.  Each hash value should

    represent the allowed attributes for the listed tag.  For example, if you want

    to allow a fair amount of HTML, you can try something like this:

        my %rules = (

            a       => [qw( href target )],

            b       => [],

            caption => [],

            center  => [],

            em      => [],

            i       => [],

            img     => [qw( alt border height width src style )],

            li      => [],

            ol      => [],

            p       => [qw(style)],

            span    => [qw(style)],

            strong  => [],

            sub     => [],

            sup     => [],

            table   => [qw( style border cellspacing cellpadding align )],

            tbody   => [],

            td      => [],

            tr      => [],

            u       => [],

            ul      => [],

        );

        my $hr = HTML::Restrict->new( rules => \%rules )

    Or, to allow only bolded text:

        my $hr = HTML::Restrict->new( rules => { b => [] } );

    Allow bolded text, images and some (but not all) image attributes:

        my %rules = (

            b   => [ ],

            img => [qw( src alt width height border / )

        );

        my $hr = HTML::Restrict->new( rules => \%rules );

    Since [HTML::Parser](https://metacpan.org/pod/HTML%3A%3AParser) treats a closing slash as an attribute, you'll need to

    add "/" to your list of allowed attributes if you'd like your tags to retain

    closing slashes.  For example:

        my $hr = HTML::Restrict->new( rules =>{ hr => [] } );

        $hr->process( "
"); # returns: 


        my $hr = HTML::Restrict->new( rules =>{ hr => [qw( / )] } );

        $hr->process( "
"); # returns: 


    HTML::Restrict strips away any tags and attributes which are not explicitly

    allowed. It also rebuilds your explicitly allowed tags and places their

    attributes in the order in which they appear in your rules.

    So, if you define the following rules:

        my %rules = (

            ...

            img => [qw( src alt title width height id / )]

            ...

        );

    then your image tags will all be built like this:

        

    This gives you greater consistency in your tag layout.  If you don't care about

    element order you don't need to pay any attention to this, but you should be

    aware that your elements are being reconstructed rather than just stripped

    down.

    As of 2.1.0, you can also specify a regex to be tested against the attribute

    value. This feature should be considered experimental for the time being:

        my $hr = HTML::Restrict->new(

            rules => {

                iframe => [

                    qw( width height allowfullscreen ),

                    {   src         => qr{^http://www\.youtube\.com},

                        frameborder => qr{^(0|1)$},

                    }

                ],

                img => [ qw( alt ), { src => qr{^/my/images/} }, ],

            },

        );

        my $html = '';

        my $processed = $hr->process( $html );

        # $processed now equals: 

    As of 2.3.0, the value to be tested against can also be a code reference.  The

    code reference will be passed the value of the attribute, and should return

    either a string to use for the attribute value, or undef to remove the attribute.

        my $hr = HTML::Restrict->new(

            rules => {

                span => [

                    { style     => sub {

                        my $value = shift;

                        # all colors are orange

                        $value =~ s/\bcolor\s*:\s*[^;]+/color: orange/g;

                        return $value;

                    } }

                ],

            },

        );

        my $html = 'This is blue';

        my $processed = $hr->process( $html );

        # $processed now equals: 

- `trim => [0|1]`

    By default all leading and trailing spaces will be removed when text is

    processed.  Set this value to 0 in order to disable this behaviour.

- `uri_schemes => [undef, 'http', 'https', 'irc', ... ]`

    As of version 1.0.3, URI scheme checking is performed on all href and src tag

    attributes. The following schemes are allowed out of the box.  No action is

    required on your part:

        [ undef, 'http', 'https' ]

    (undef represents relative URIs). These restrictions have been put in place to

    prevent XSS in the form of:

        click for cookie!

    See [URI](https://metacpan.org/pod/URI) for more detailed info on scheme parsing.  If, for example, you

    wanted to filter out every scheme barring SSL, you would do it like this:

        uri_schemes => ['https']

    This feature is new in 1.0.3.  Previous to this, there was no schema checking

    at all.  Moving forward, you'll need to whitelist explicitly all URI schemas

    which are not supported by default.  This is in keeping with the whitelisting

    behaviour of this module and is also the safest possible approach.  Keep in

    mind that changes to uri\_schemes are not additive, so you'll need to include

    the defaults in any changes you make, should you wish to keep them:

        # defaults + irc + mailto

        uri_schemes => [ 'undef', 'http', 'https', 'irc', 'mailto' ]

- allow\_declaration => \[0|1\]

    Set this value to true if you'd like to allow/preserve DOCTYPE declarations in

    your content.  Useful when cleaning up your own static files or templates. This

    feature is off by default.

        my $html = q[foo];

        my $hr = HTML::Restrict->new( allow_declaration => 1 );

        $html = $hr->process( $html );

        # $html is now: "foo"

- allow\_comments => \[0|1\]

    Set this value to true if you'd like to allow/preserve HTML comments in your

    content.  Useful when cleaning up your own static files or templates. This

    feature is off by default.

        my $html = q[foo];

        my $hr = HTML::Restrict->new( allow_comments => 1 );

        $html = $hr->process( $html );

        # $html is now: "foo"

- create\_newlines => \[0|1\]

    Set the value to true if you'd like to have each br tag replaced by a

    newline and every p tag replaced by two newlines. If a tag is

    specified in the allowed HTML, it won't be replaced.

- replace\_img => \[0|1|CodeRef\]

    Set the value to true if you'd like to have img tags replaced with

    `[IMAGE: ...]` containing the alt attribute text.  If you set it to a

    code reference, you can provide your own replacement (which may

    even contain HTML).

        sub replacer {

            my ($tagname, $attr, $text) = @_; # from HTML::Parser

            return qq{IMAGE: $attr->{alt}};

        }

        my $hr = HTML::Restrict->new( replace_img => \&replacer );

    This attribute will only take effect if the img tag is not included

    in the allowed HTML.

- strip\_enclosed\_content => \[0|1\]

    The default behaviour up to 1.0.4 was to preserve the content between script

    and style tags, even when the tags themselves were being deleted.  So, you'd be

    left with a bunch of JavaScript or CSS, just with the enclosing tags missing.

    This is almost never what you want, so starting at 1.0.5 the default will be to

    remove any script or style info which is enclosed in these tags, unless they

    have specifically been whitelisted in the rules.  This will be a sane default

    when cleaning up content submitted via a web form.  However, if you're using

    HTML::Restrict to purge your own HTML you can be more restrictive.

        # strip the head section, in addition to JS and CSS

        my $html = '......JS herefoo';

        my $hr = HTML::Restrict->new(

            strip_enclosed_content => [ 'script', 'style', 'head' ]

        );

        $html = $hr->process( $html );

        # $html is now '...foo';

    The caveat here is that HTML::Restrict will not try to fix broken HTML. In the

    above example, if you have any opening script, style or head tags which don't

    also include matching closing tags, all following content will be stripped

    away, regardless of any parent tags.

    Keep in mind that changes to strip\_enclosed\_content are not additive, so if you

    are adding additional tags you'll need to include the entire list of tags whose

    enclosed content you'd like to remove.  This feature strips script and style

    tags by default.

- `filter_text => [0|1|CodeRef]`

    By default all text will be filtered to fix any encoding problems which may

    cause security issues. You may override the encoding behaviour by providing

    your own anonymous sub to `filter_text`. This first and only argument to the

    sub is the text which needs to be filtered. The sub should return a scalar

    containing the transformed text.

        filter_text => sub {

            my $text = shift;

            ... # transform text

            return $text;

        },

    You may also this value to 0 in order to disable this behaviour entirely.

    Please be advised this is a security risk. Use caution when disabling this

    parameter or providing your own filter function.

# SUBROUTINES/METHODS

## process( $html )

This is the method which does the real work.  It parses your data, removes any

tags and attributes which are not specifically allowed and returns the

resulting text.  Requires and returns a SCALAR.

## get\_rules

Accessor which returns a hash ref of the current rule set.

## get\_uri\_schemes

Accessor which returns an array ref of the current valid uri schemes.

# CAVEATS

Please note that all tag and attribute names passed via the rules param must be

supplied in lower case.

    # correct

    my $hr = HTML::Restrict->new( rules => { body => ['onload'] } );

    # throws a fatal error

    my $hr = HTML::Restrict->new( rules => { Body => ['onLoad'] } );

# MOTIVATION

There are already several modules on the CPAN which accomplish much of the same

thing, but after doing a lot of poking around, I was unable to find a solution

with a simple setup which I was happy with.

The most common use case might be stripping HTML from user submitted data

completely or allowing just a few tags and attributes to be displayed.  With

the exception of URI scheme checking, this module doesn't do any validation on

the actual content of the tags or attributes.  If this is a requirement, you

can either mess with the parser object, post-process the text yourself or have

a look at one of the more feature-rich modules in the SEE ALSO section below.

My aim here is to keep things easy and, hopefully, cover a lot of the less

complex use cases with just a few lines of code and some brief documentation.

The idea is to be up and running quickly.

# SEE ALSO

[HTML::TagFilter](https://metacpan.org/pod/HTML%3A%3ATagFilter), [HTML::Defang](https://metacpan.org/pod/HTML%3A%3ADefang), [MojoMojo::Declaw](https://metacpan.org/pod/MojoMojo%3A%3ADeclaw), [HTML::StripScripts](https://metacpan.org/pod/HTML%3A%3AStripScripts),

[HTML::Detoxifier](https://metacpan.org/pod/HTML%3A%3ADetoxifier), HTML::Sanitizer, [HTML::Scrubber](https://metacpan.org/pod/HTML%3A%3AScrubber)

# ACKNOWLEDGEMENTS

Thanks to Raybec Communications [http://www.raybec.com](http://www.raybec.com) for funding my

work on this module and for releasing it to the world.

Thanks also to the many other contributors. [https://github.com/oalders/html-restrict/graphs/contributors](https://github.com/oalders/html-restrict/graphs/contributors)

# AUTHOR

Olaf Alders 

# COPYRIGHT AND LICENSE

This software is copyright (c) 2009 by Olaf Alders.

This is free software; you can redistribute it and/or modify it under

the same terms as the Perl 5 programming language system itself.