1HTML::Restrict(3) User Contributed Perl Documentation HTML::Restrict(3)
2
6 HTML::Restrict - Strip unwanted HTML tags and attributes
7
9 version v2.5.0
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 $hr = HTML::Restrict->new(
23 rules => {
24 b => [],
25 img => [qw( src alt / )]
26 }
27 );
28 my $html = q[<body><b>hello</b> <img src="pic.jpg" alt="me" id="test" /></body>];
30 $processed = $hr->process( $html );
31 # $processed now equals: <b>hello</b> <img src="pic.jpg" alt="me" />
33
35 This module uses HTML::Parser to strip HTML from text in a restrictive
36 manner. By default all HTML is restricted. You may alter the default
37 behaviour by supplying your own tag rules.
38
40 new()
41 Creates and returns a new HTML::Restrict object.
42 my $hr = HTML::Restrict->new()
44 HTML::Restrict doesn't require any params to be passed to new. If your
46 goal is to remove all HTML from text, then no further setup is
47 required. Just pass your text to the process() method and you're done:
48 my $plain_text = $hr->process( $html );
50 If you need to set up specific rules, have a look at the params which
52 HTML::Restrict recognizes:
53 · "rules => \%rules"
55 Sets the rules which will be used to process your data. By default
57 all HTML tags are off limits. Use this argument to define the HTML
58 elements and corresponding attributes you'd like to use.
59 Essentially, consider the default behaviour to be:
60 rules => {}
62 Rules should be passed as a HASHREF of allowed tags. Each hash
64 value should represent the allowed attributes for the listed tag.
65 For example, if you want to allow a fair amount of HTML, you can
66 try something like this:
67 my %rules = (
69 a => [qw( href target )],
70 b => [],
71 caption => [],
72 center => [],
73 em => [],
74 i => [],
75 img => [qw( alt border height width src style )],
76 li => [],
77 ol => [],
78 p => [qw(style)],
79 span => [qw(style)],
80 strong => [],
81 sub => [],
82 sup => [],
83 table => [qw( style border cellspacing cellpadding align )],
84 tbody => [],
85 td => [],
86 tr => [],
87 u => [],
88 ul => [],
89 );
90 my $hr = HTML::Restrict->new( rules => \%rules )
92 Or, to allow only bolded text:
94 my $hr = HTML::Restrict->new( rules => { b => [] } );
96 Allow bolded text, images and some (but not all) image attributes:
98 my %rules = (
100 b => [ ],
101 img => [qw( src alt width height border / )
102 );
103 my $hr = HTML::Restrict->new( rules => \%rules );
104 Since HTML::Parser treats a closing slash as an attribute, you'll
106 need to add "/" to your list of allowed attributes if you'd like
107 your tags to retain closing slashes. For example:
108 my $hr = HTML::Restrict->new( rules =>{ hr => [] } );
110 $hr->process( "<hr />"); # returns: <hr>
111 my $hr = HTML::Restrict->new( rules =>{ hr => [qw( / )] } );
113 $hr->process( "<hr />"); # returns: <hr />
114 HTML::Restrict strips away any tags and attributes which are not
116 explicitly allowed. It also rebuilds your explicitly allowed tags
117 and places their attributes in the order in which they appear in
118 your rules.
119 So, if you define the following rules:
121 my %rules = (
123 ...
124 img => [qw( src alt title width height id / )]
125 ...
126 );
127 then your image tags will all be built like this:
129 <img src=".." alt="..." title="..." width="..." height="..." id=".." />
131 This gives you greater consistency in your tag layout. If you
133 don't care about element order you don't need to pay any attention
134 to this, but you should be aware that your elements are being
135 reconstructed rather than just stripped down.
136 As of 2.1.0, you can also specify a regex to be tested against the
138 attribute value. This feature should be considered experimental for
139 the time being:
140 my $hr = HTML::Restrict->new(
142 rules => {
143 iframe => [
144 qw( width height allowfullscreen ),
145 { src => qr{^http://www\.youtube\.com},
146 frameborder => qr{^(0|1)$},
147 }
148 ],
149 img => [ qw( alt ), { src => qr{^/my/images/} }, ],
150 },
151 );
152 my $html = '<img src="http://www.example.com/image.jpg" alt="Alt Text">';
154 my $processed = $hr->process( $html );
155 # $processed now equals: <img alt="Alt Text">
157 As of 2.3.0, the value to be tested against can also be a code
159 reference. The code reference will be passed the value of the
160 attribute, and should return either a string to use for the
161 attribute value, or undef to remove the attribute.
162 my $hr = HTML::Restrict->new(
164 rules => {
165 span => [
166 { style => sub {
167 my $value = shift;
168 # all colors are orange
169 $value =~ s/\bcolor\s*:\s*[^;]+/color: orange/g;
170 return $value;
171 } }
172 ],
173 },
174 );
175 my $html = '<span style="color: #0000ff;">This is blue</span>';
177 my $processed = $hr->process( $html );
178 # $processed now equals: <span style="color: orange;">
180 · "trim => [0|1]"
182 By default all leading and trailing spaces will be removed when
184 text is processed. Set this value to 0 in order to disable this
185 behaviour.
186 · "uri_schemes => [undef, 'http', 'https', 'irc', ... ]"
188 As of version 1.0.3, URI scheme checking is performed on all href
190 and src tag attributes. The following schemes are allowed out of
191 the box. No action is required on your part:
192 [ undef, 'http', 'https' ]
194 (undef represents relative URIs). These restrictions have been put
196 in place to prevent XSS in the form of:
197 <a href="javascript:alert(document.cookie)">click for cookie!</a>
199 See URI for more detailed info on scheme parsing. If, for example,
201 you wanted to filter out every scheme barring SSL, you would do it
202 like this:
203 uri_schemes => ['https']
205 This feature is new in 1.0.3. Previous to this, there was no
207 schema checking at all. Moving forward, you'll need to whitelist
208 explicitly all URI schemas which are not supported by default.
209 This is in keeping with the whitelisting behaviour of this module
210 and is also the safest possible approach. Keep in mind that
211 changes to uri_schemes are not additive, so you'll need to include
212 the defaults in any changes you make, should you wish to keep them:
213 # defaults + irc + mailto
215 uri_schemes => [ 'undef', 'http', 'https', 'irc', 'mailto' ]
216 · allow_declaration => [0|1]
218 Set this value to true if you'd like to allow/preserve DOCTYPE
220 declarations in your content. Useful when cleaning up your own
221 static files or templates. This feature is off by default.
222 my $html = q[<!doctype html><body>foo</body>];
224 my $hr = HTML::Restrict->new( allow_declaration => 1 );
226 $html = $hr->process( $html );
227 # $html is now: "<!doctype html>foo"
228 · allow_comments => [0|1]
230 Set this value to true if you'd like to allow/preserve HTML
232 comments in your content. Useful when cleaning up your own static
233 files or templates. This feature is off by default.
234 my $html = q[<body><!-- comments! -->foo</body>];
236 my $hr = HTML::Restrict->new( allow_comments => 1 );
238 $html = $hr->process( $html );
239 # $html is now: "<!-- comments! -->foo"
240 · max_parser_loops => [Integer]
242 Defaults to 25. Should never be less than 2.
244 As of v2.4.0, calling "process()" will force the parser to clean
246 the text multiple times, stopping only once the text is no longer
247 changed or once "max_parser_loops" has been reached.
248 The reason for this is that HTML::Parser could take malformed HTML
250 and turn it into well formed HTML. This can defeat our processing
251 logic and allow malicious input to be returned. In order to
252 mitigate this, we will clean all input at least two times. If the
253 second attempt at cleaning does not match the previous attempt, we
254 will make a third attempt and so on. This helps to ensure that we
255 get the expected output.
256 If we are unable to get unchanged values after reaching
258 "max_parser_loops", an exception will be thrown. Returning
259 partially cleaned text would be wrong, as would be returning
260 "undef" or an empty string. Throwing an exception forces the user
261 to choose the appropriate way of dealing with this.
262 If you choose to set this value, please note that it can be no less
264 than 2, or the parser will never be able to make a comparison with
265 a previous value. An exception will be thrown if you attempt to
266 set this to a value less than 2.
267 · replace_img => [0|1|CodeRef]
269 Set the value to true if you'd like to have img tags replaced with
271 "[IMAGE: ...]" containing the alt attribute text. If you set it to
272 a code reference, you can provide your own replacement (which may
273 even contain HTML).
274 sub replacer {
276 my ($tagname, $attr, $text) = @_; # from HTML::Parser
277 return qq{<a href="$attr->{src}">IMAGE: $attr->{alt}</a>};
278 }
279 my $hr = HTML::Restrict->new( replace_img => \&replacer );
281 This attribute will only take effect if the img tag is not included
283 in the allowed HTML.
284 · strip_enclosed_content => [0|1]
286 The default behaviour up to 1.0.4 was to preserve the content
288 between script and style tags, even when the tags themselves were
289 being deleted. So, you'd be left with a bunch of JavaScript or
290 CSS, just with the enclosing tags missing. This is almost never
291 what you want, so starting at 1.0.5 the default will be to remove
292 any script or style info which is enclosed in these tags, unless
293 they have specifically been whitelisted in the rules. This will be
294 a sane default when cleaning up content submitted via a web form.
295 However, if you're using HTML::Restrict to purge your own HTML you
296 can be more restrictive.
297 # strip the head section, in addition to JS and CSS
299 my $html = '<html><head>...</head><body>...<script>JS here</script>foo';
300 my $hr = HTML::Restrict->new(
302 strip_enclosed_content => [ 'script', 'style', 'head' ]
303 );
304 $html = $hr->process( $html );
306 # $html is now '<html><body>...foo';
307 The caveat here is that HTML::Restrict will not try to fix broken
309 HTML. In the above example, if you have any opening script, style
310 or head tags which don't also include matching closing tags, all
311 following content will be stripped away, regardless of any parent
312 tags.
313 Keep in mind that changes to strip_enclosed_content are not
315 additive, so if you are adding additional tags you'll need to
316 include the entire list of tags whose enclosed content you'd like
317 to remove. This feature strips script and style tags by default.
318
320 process( $html )
321 This is the method which does the real work. It parses your data,
322 removes any tags and attributes which are not specifically allowed and
323 returns the resulting text. Requires and returns a SCALAR.
324 get_rules
326 Accessor which returns a hash ref of the current rule set.
327 get_uri_schemes
329 Accessor which returns an array ref of the current valid uri schemes.
330
332 Please note that all tag and attribute names passed via the rules param
333 must be supplied in lower case.
334 # correct
336 my $hr = HTML::Restrict->new( rules => { body => ['onload'] } );
337 # throws a fatal error
339 my $hr = HTML::Restrict->new( rules => { Body => ['onLoad'] } );
340
342 There are already several modules on the CPAN which accomplish much of
343 the same thing, but after doing a lot of poking around, I was unable to
344 find a solution with a simple setup which I was happy with.
345 The most common use case might be stripping HTML from user submitted
347 data completely or allowing just a few tags and attributes to be
348 displayed. With the exception of URI scheme checking, this module
349 doesn't do any validation on the actual content of the tags or
350 attributes. If this is a requirement, you can either mess with the
351 parser object, post-process the text yourself or have a look at one of
352 the more feature-rich modules in the SEE ALSO section below.
353 My aim here is to keep things easy and, hopefully, cover a lot of the
355 less complex use cases with just a few lines of code and some brief
356 documentation. The idea is to be up and running quickly.
357
359 HTML::TagFilter, HTML::Defang, MojoMojo::Declaw, HTML::StripScripts,
360 HTML::Detoxifier, HTML::Sanitizer, HTML::Scrubber
361
363 Thanks to Raybec Communications <http://www.raybec.com> for funding my
364 work on this module and for releasing it to the world.
365 Thanks also to the following for patches, bug reports and assistance:
367 Mark Jubenville (ioncache)
369 Duncan Forsyth
371 Rick Moore
373 Arthur Axel 'fREW' Schmidt
375 perlpong
377 David Golden
379 Graham TerMarsch
381 Dagfinn Ilmari Mannsåker
383 Graham Knop
385 Carwyn Ellis
387
389 Olaf Alders <olaf@wundercounter.com>
390
392 This software is copyright (c) 2013-2017 by Olaf Alders.
393 This is free software; you can redistribute it and/or modify it under
395 the same terms as the Perl 5 programming language system itself.
396perl v5.28.1 2019-02-08 HTML::Restrict(3)
