1HTML::Restrict(3) User Contributed Perl Documentation HTML::Restrict(3)
2
6 HTML::Restrict - Strip unwanted HTML tags and attributes
7
9 version v2.3.0
10
12 use HTML::Restrict;
13 my $hr = HTML::Restrict->new();
15 # use default rules to start with (strip away all HTML)
17 my $processed = $hr->process(' <b>i am bold</b> ');
18 # $processed now equals: 'i am bold'
20 # Now, a less restrictive example:
22 use HTML::Restrict;
23 my $hr = HTML::Restrict->new(
25 rules => {
26 b => [],
27 img => [qw( src alt / )]
28 }
29 );
30 my $html = q[<body><b>hello</b> <img src="pic.jpg" alt="me" id="test" /></body>];
32 my $processed = $hr->process( $html );
33 # $processed now equals: <b>hello</b> <img src="pic.jpg" alt="me" />
35
37 This module uses HTML::Parser to strip HTML from text in a restrictive
38 manner. By default all HTML is restricted. You may alter the default
39 behaviour by supplying your own tag rules.
40
42 new()
43 Creates and returns a new HTML::Restrict object.
44 my $hr = HTML::Restrict->new()
46 HTML::Restrict doesn't require any params to be passed to new. If your
48 goal is to remove all HTML from text, then no further setup is
49 required. Just pass your text to the process() method and you're done:
50 my $plain_text = $hr->process( $html );
52 If you need to set up specific rules, have a look at the params which
54 HTML::Restrict recognizes:
55 · "rules => \%rules"
57 Sets the rules which will be used to process your data. By default
59 all HTML tags are off limits. Use this argument to define the HTML
60 elements and corresponding attributes you'd like to use.
61 Essentially, consider the default behaviour to be:
62 rules => {}
64 Rules should be passed as a HASHREF of allowed tags. Each hash
66 value should represent the allowed attributes for the listed tag.
67 For example, if you want to allow a fair amount of HTML, you can
68 try something like this:
69 my %rules = (
71 a => [qw( href target )],
72 b => [],
73 caption => [],
74 center => [],
75 em => [],
76 i => [],
77 img => [qw( alt border height width src style )],
78 li => [],
79 ol => [],
80 p => [qw(style)],
81 span => [qw(style)],
82 strong => [],
83 sub => [],
84 sup => [],
85 table => [qw( style border cellspacing cellpadding align )],
86 tbody => [],
87 td => [],
88 tr => [],
89 u => [],
90 ul => [],
91 );
92 my $hr = HTML::Restrict->new( rules => \%rules )
94 Or, to allow only bolded text:
96 my $hr = HTML::Restrict->new( rules => { b => [] } );
98 Allow bolded text, images and some (but not all) image attributes:
100 my %rules = (
102 b => [ ],
103 img => [qw( src alt width height border / )
104 );
105 my $hr = HTML::Restrict->new( rules => \%rules );
106 Since HTML::Parser treats a closing slash as an attribute, you'll
108 need to add "/" to your list of allowed attributes if you'd like
109 your tags to retain closing slashes. For example:
110 my $hr = HTML::Restrict->new( rules =>{ hr => [] } );
112 $hr->process( "<hr />"); # returns: <hr>
113 my $hr = HTML::Restrict->new( rules =>{ hr => [qw( / )] } );
115 $hr->process( "<hr />"); # returns: <hr />
116 HTML::Restrict strips away any tags and attributes which are not
118 explicitly allowed. It also rebuilds your explicitly allowed tags
119 and places their attributes in the order in which they appear in
120 your rules.
121 So, if you define the following rules:
123 my %rules = (
125 ...
126 img => [qw( src alt title width height id / )]
127 ...
128 );
129 then your image tags will all be built like this:
131 <img src=".." alt="..." title="..." width="..." height="..." id=".." />
133 This gives you greater consistency in your tag layout. If you
135 don't care about element order you don't need to pay any attention
136 to this, but you should be aware that your elements are being
137 reconstructed rather than just stripped down.
138 As of 2.1.0, you can also specify a regex to be tested against the
140 attribute value. This feature should be considered experimental for
141 the time being:
142 my $hr = HTML::Restrict->new(
144 rules => {
145 iframe => [
146 qw( width height allowfullscreen ),
147 { src => qr{^http://www\.youtube\.com},
148 frameborder => qr{^(0|1)$},
149 }
150 ],
151 img => [ qw( alt ), { src => qr{^/my/images/} }, ],
152 },
153 );
154 my $html = '<img src="http://www.example.com/image.jpg" alt="Alt Text">';
156 my $processed = $hr->process( $html );
157 # $processed now equals: <img alt="Alt Text">
159 As of 2.3.0, the value to be tested against can also be a code
161 reference. The code reference will be passed the value of the
162 attribute, and should return either a string to use for the
163 attribute value, or undef to remove the attribute.
164 my $hr = HTML::Restrict->new(
166 rules => {
167 span => [
168 { style => sub {
169 my $value = shift;
170 # all colors are orange
171 $value =~ s/\bcolor\s*:\s*[^;]+/color: orange/g;
172 return $value;
173 } }
174 ],
175 },
176 );
177 my $html = '<span style="color: #0000ff;">This is blue</span>';
179 my $processed = $hr->process( $html );
180 # $processed now equals: <span style="color: orange;">
182 · "trim => [0|1]"
184 By default all leading and trailing spaces will be removed when
186 text is processed. Set this value to 0 in order to disable this
187 behaviour.
188 · "uri_schemes => [undef, 'http', 'https', 'irc', ... ]"
190 As of version 1.0.3, URI scheme checking is performed on all href
192 and src tag attributes. The following schemes are allowed out of
193 the box. No action is required on your part:
194 [ undef, 'http', 'https' ]
196 (undef represents relative URIs). These restrictions have been put
198 in place to prevent XSS in the form of:
199 <a href="javascript:alert(document.cookie)">click for cookie!</a>
201 See URI for more detailed info on scheme parsing. If, for example,
203 you wanted to filter out every scheme barring SSL, you would do it
204 like this:
205 uri_schemes => ['https']
207 This feature is new in 1.0.3. Previous to this, there was no
209 schema checking at all. Moving forward, you'll need to whitelist
210 explicitly all URI schemas which are not supported by default.
211 This is in keeping with the whitelisting behaviour of this module
212 and is also the safest possible approach. Keep in mind that
213 changes to uri_schemes are not additive, so you'll need to include
214 the defaults in any changes you make, should you wish to keep them:
215 # defaults + irc + mailto
217 uri_schemes => [ 'undef', 'http', 'https', 'irc', 'mailto' ]
218 · allow_declaration => [0|1]
220 Set this value to true if you'd like to allow/preserve DOCTYPE
222 declarations in your content. Useful when cleaning up your own
223 static files or templates. This feature is off by default.
224 my $html = q[<!doctype html><body>foo</body>];
226 my $hr = HTML::Restrict->new( allow_declaration => 1 );
228 $html = $hr->process( $html );
229 # $html is now: "<!doctype html>foo"
230 · allow_comments => [0|1]
232 Set this value to true if you'd like to allow/preserve HTML
234 comments in your content. Useful when cleaning up your own static
235 files or templates. This feature is off by default.
236 my $html = q[<body><!-- comments! -->foo</body>];
238 my $hr = HTML::Restrict->new( allow_comments => 1 );
240 $html = $hr->process( $html );
241 # $html is now: "<!-- comments! -->foo"
242 · replace_img => [0|1|CodeRef]
244 Set the value to true if you'd like to have img tags replaced with
246 "[IMAGE: ...]" containing the alt attribute text. If you set it to
247 a code reference, you can provide your own replacement (which may
248 even contain HTML).
249 sub replacer {
251 my ($tagname, $attr, $text) = @_; # from HTML::Parser
252 return qq{<a href="$attr->{src}">IMAGE: $attr->{alt}</a>};
253 }
254 my $hr = HTML::Restrict->new( replace_img => \&replacer );
256 This attribute will only take effect if the img tag is not included
258 in the allowed HTML.
259 · strip_enclosed_content => [0|1]
261 The default behaviour up to 1.0.4 was to preserve the content
263 between script and style tags, even when the tags themselves were
264 being deleted. So, you'd be left with a bunch of JavaScript or
265 CSS, just with the enclosing tags missing. This is almost never
266 what you want, so starting at 1.0.5 the default will be to remove
267 any script or style info which is enclosed in these tags, unless
268 they have specifically been whitelisted in the rules. This will be
269 a sane default when cleaning up content submitted via a web form.
270 However, if you're using HTML::Restrict to purge your own HTML you
271 can be more restrictive.
272 # strip the head section, in addition to JS and CSS
274 my $html = '<html><head>...</head><body>...<script>JS here</script>foo';
275 my $hr = HTML::Restrict->new(
277 strip_enclosed_content => [ 'script', 'style', 'head' ]
278 );
279 $html = $hr->process( $html );
281 # $html is now '<html><body>...foo';
282 The caveat here is that HTML::Restrict will not try to fix broken
284 HTML. In the above example, if you have any opening script, style
285 or head tags which don't also include matching closing tags, all
286 following content will be stripped away, regardless of any parent
287 tags.
288 Keep in mind that changes to strip_enclosed_content are not
290 additive, so if you are adding additional tags you'll need to
291 include the entire list of tags whose enclosed content you'd like
292 to remove. This feature strips script and style tags by default.
293
295 process( $html )
296 This is the method which does the real work. It parses your data,
297 removes any tags and attributes which are not specifically allowed and
298 returns the resulting text. Requires and returns a SCALAR.
299 get_rules
301 Accessor which returns a hash ref of the current rule set.
302 get_uri_schemes
304 Accessor which returns an array ref of the current valid uri schemes.
305
307 Please note that all tag and attribute names passed via the rules param
308 must be supplied in lower case.
309 # correct
311 my $hr = HTML::Restrict->new( rules => { body => ['onload'] } );
312 # throws a fatal error
314 my $hr = HTML::Restrict->new( rules => { Body => ['onLoad'] } );
315
317 There are already several modules on the CPAN which accomplish much of
318 the same thing, but after doing a lot of poking around, I was unable to
319 find a solution with a simple setup which I was happy with.
320 The most common use case might be stripping HTML from user submitted
322 data completely or allowing just a few tags and attributes to be
323 displayed. With the exception of URI scheme checking, this module
324 doesn't do any validation on the actual content of the tags or
325 attributes. If this is a requirement, you can either mess with the
326 parser object, post-process the text yourself or have a look at one of
327 the more feature-rich modules in the SEE ALSO section below.
328 My aim here is to keep things easy and, hopefully, cover a lot of the
330 less complex use cases with just a few lines of code and some brief
331 documentation. The idea is to be up and running quickly.
332
334 HTML::TagFilter, HTML::Defang, MojoMojo::Declaw, HTML::StripScripts,
335 HTML::Detoxifier, HTML::Sanitizer, HTML::Scrubber
336
338 Thanks to Raybec Communications <http://www.raybec.com> for funding my
339 work on this module and for releasing it to the world.
340 Thanks also to the following for patches, bug reports and assistance:
342 Mark Jubenville (ioncache)
344 Duncan Forsyth
346 Rick Moore
348 Arthur Axel 'fREW' Schmidt
350 perlpong
352 David Golden
354 Graham TerMarsch
356 Dagfinn Ilmari Mannsåker
358 Graham Knop
360 Carwyn Ellis
362
364 Olaf Alders <olaf@wundercounter.com>
365
367 This software is copyright (c) 2013-2017 by Olaf Alders.
368 This is free software; you can redistribute it and/or modify it under
370 the same terms as the Perl 5 programming language system itself.
371perl v5.28.0 2018-02-09 HTML::Restrict(3)
