1 # cython: language_level=3str
3 """A cleanup tool for HTML.
5 Removes unwanted tags and content. See the `Cleaner` class for
9 from __future__ import absolute_import
14 from urlparse import urlsplit
15 from urllib import unquote_plus
18 from urllib.parse import urlsplit, unquote_plus
19 from lxml import etree
20 from lxml.html import defs
21 from lxml.html import fromstring, XHTML_NAMESPACE
22 from lxml.html import xhtml_to_html, _transform_result
37 basestring = (str, bytes)
40 __all__ = ['clean_html', 'clean', 'Cleaner', 'autolink', 'autolink_html',
41 'word_break', 'word_break_html']
43 # Look at http://code.sixapart.com/trac/livejournal/browser/trunk/cgi-bin/cleanhtml.pl
44 # Particularly the CSS cleaning; most of the tag cleaning is integrated now
45 # I have multiple kinds of schemes searched; but should schemes be
46 # whitelisted instead?
48 # remove images? Also in CSS? background attribute?
49 # Some way to whitelist object, iframe, etc (e.g., if you want to
50 # allow *just* embedded YouTube movies)
51 # Log what was deleted and why?
52 # style="behavior: ..." might be bad in IE?
53 # Should we have something for just <meta http-equiv>? That's the worst of the
55 # UTF-7 detections? Example:
56 # <HEAD><META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=UTF-7"> </HEAD>+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-
57 # you don't always have to have the charset set, if the page has no charset
58 # and there's UTF7-like code in it.
59 # Look at these tests: http://htmlpurifier.org/live/smoketests/xssAttacks.php
62 # This is an IE-specific construct you can have in a stylesheet to
63 # run some Javascript:
64 _css_javascript_re = re.compile(
65 r'expression\s*\(.*?\)', re.S|re.I)
67 # Do I have to worry about @\nimport?
68 _css_import_re = re.compile(
71 # All kinds of schemes besides just javascript: that can cause
73 _is_image_dataurl = re.compile(
74 r'^data:image/.+;base64', re.I).search
75 _is_possibly_malicious_scheme = re.compile(
76 r'(?:javascript|jscript|livescript|vbscript|data|about|mocha):',
78 def _is_javascript_scheme(s):
79 if _is_image_dataurl(s):
81 return _is_possibly_malicious_scheme(s)
83 _substitute_whitespace = re.compile(r'[\s\x00-\x08\x0B\x0C\x0E-\x19]+').sub
84 # FIXME: should data: be blocked?
86 # FIXME: check against: http://msdn2.microsoft.com/en-us/library/ms537512.aspx
87 _conditional_comment_re = re.compile(
88 r'\[if[\s\n\r]+.*?][\s\n\r]*>', re.I|re.S)
90 _find_styled_elements = etree.XPath(
91 "descendant-or-self::*[@style]")
93 _find_external_links = etree.XPath(
94 ("descendant-or-self::a [normalize-space(@href) and substring(normalize-space(@href),1,1) != '#'] |"
95 "descendant-or-self::x:a[normalize-space(@href) and substring(normalize-space(@href),1,1) != '#']"),
96 namespaces={'x':XHTML_NAMESPACE})
99 class Cleaner(object):
101 Instances cleans the document of each of the possible offending
102 elements. The cleaning is controlled by attributes; you can
103 override attributes in a subclass, or set them in the constructor.
106 Removes any ``<script>`` tags.
109 Removes any Javascript, like an ``onclick`` attribute. Also removes stylesheets
110 as they could contain Javascript.
113 Removes any comments.
116 Removes any style tags.
119 Removes any style attributes. Defaults to the value of the ``style`` option.
122 Removes any ``<link>`` tags
125 Removes any ``<meta>`` tags
128 Structural parts of a page: ``<head>``, ``<html>``, ``<title>``.
130 ``processing_instructions``:
131 Removes any processing instructions.
134 Removes any embedded objects (flash, iframes)
137 Removes any frame-related tags
140 Removes any form tags
143 Tags that aren't *wrong*, but are annoying. ``<blink>`` and ``<marquee>``
146 A list of tags to remove. Only the tags will be removed,
147 their content will get pulled up into the parent tag.
150 A list of tags to kill. Killing also removes the tag's content,
151 i.e. the whole subtree, not just the tag itself.
154 A list of tags to include (default include all).
156 ``remove_unknown_tags``:
157 Remove any tags that aren't standard parts of HTML.
160 If true, only include 'safe' attributes (specifically the list
161 from the feedparser HTML sanitisation web site).
164 A set of attribute names to override the default list of attributes
165 considered 'safe' (when safe_attrs_only=True).
168 If true, then any <a> tags will have ``rel="nofollow"`` added to them.
171 A list or set of hosts that you can use for embedded content
172 (for content like ``<object>``, ``<link rel="stylesheet">``, etc).
173 You can also implement/override the method
174 ``allow_embedded_url(el, url)`` or ``allow_element(el)`` to
175 implement more complex rules for what can be embedded.
176 Anything that passes this test will be shown, regardless of
177 the value of (for instance) ``embedded``.
179 Note that this parameter might not work as intended if you do not
180 make the links absolute before doing the cleaning.
182 Note that you may also need to set ``whitelist_tags``.
185 A set of tags that can be included with ``host_whitelist``.
186 The default is ``iframe`` and ``embed``; you may wish to
187 include other tags like ``script``, or you may want to
188 implement ``allow_embedded_url`` for more control. Set to None to
191 This modifies the document *in place*.
201 page_structure = True
202 processing_instructions = True
210 remove_unknown_tags = True
211 safe_attrs_only = True
212 safe_attrs = defs.safe_attrs
215 whitelist_tags = {'iframe', 'embed'}
217 def __init__(self, **kw):
218 not_an_attribute = object()
219 for name, value in kw.items():
220 default = getattr(self, name, not_an_attribute)
221 if (default is not None and default is not True and default is not False
222 and not isinstance(default, (frozenset, set, tuple, list))):
224 "Unknown parameter: %s=%r" % (name, value))
225 setattr(self, name, value)
226 if self.inline_style is None and 'inline_style' not in kw:
227 self.inline_style = self.style
229 if kw.get("allow_tags"):
230 if kw.get("remove_unknown_tags"):
231 raise ValueError("It does not make sense to pass in both "
232 "allow_tags and remove_unknown_tags")
233 self.remove_unknown_tags = False
235 # Used to lookup the primary URL for a given tag that is up for
237 _tag_link_attrs = dict(
240 # From: http://java.sun.com/j2se/1.4.2/docs/guide/misc/applet.html
241 # From what I can tell, both attributes can contain a link:
242 applet=['code', 'object'],
246 # FIXME: there doesn't really seem like a general way to figure out what
247 # links an <object> tag uses; links often go in <param> tags with values
248 # that we don't really know. You'd have to have knowledge about specific
249 # kinds of plugins (probably keyed off classid), and match against those.
251 # FIXME: not looking at the action currently, because it is more complex
252 # than than -- if you keep the form, you should keep the form controls.
257 def __call__(self, doc):
262 getroot = doc.getroot
263 except AttributeError:
264 pass # Element instance
266 doc = getroot() # ElementTree instance, instead of an element
267 # convert XHTML to HTML
269 # Normalize a case that IE treats <image> like <img>, and that
270 # can confuse either this step or later steps.
271 for el in doc.iter('image'):
273 if not self.comments:
274 # Of course, if we were going to kill comments anyway, we don't
275 # need to worry about this
276 self.kill_conditional_comments(doc)
278 kill_tags = set(self.kill_tags or ())
279 remove_tags = set(self.remove_tags or ())
280 allow_tags = set(self.allow_tags or ())
283 kill_tags.add('script')
284 if self.safe_attrs_only:
285 safe_attrs = set(self.safe_attrs)
286 for el in doc.iter(etree.Element):
288 for aname in attrib.keys():
289 if aname not in safe_attrs:
292 if not (self.safe_attrs_only and
293 self.safe_attrs == defs.safe_attrs):
294 # safe_attrs handles events attributes itself
295 for el in doc.iter(etree.Element):
297 for aname in attrib.keys():
298 if aname.startswith('on'):
300 doc.rewrite_links(self._remove_javascript_link,
301 resolve_base_href=False)
302 # If we're deleting style then we don't have to remove JS links
303 # from styles, otherwise...
304 if not self.inline_style:
305 for el in _find_styled_elements(doc):
306 old = el.get('style')
307 new = _css_javascript_re.sub('', old)
308 new = _css_import_re.sub('', new)
309 if self._has_sneaky_javascript(new):
310 # Something tricky is going on...
311 del el.attrib['style']
315 for el in list(doc.iter('style')):
316 if el.get('type', '').lower().strip() == 'text/javascript':
320 new = _css_javascript_re.sub('', old)
321 # The imported CSS can do anything; we just can't allow:
322 new = _css_import_re.sub('', old)
323 if self._has_sneaky_javascript(new):
324 # Something tricky is going on...
325 el.text = '/* deleted */'
329 kill_tags.add(etree.Comment)
330 if self.processing_instructions:
331 kill_tags.add(etree.ProcessingInstruction)
333 kill_tags.add('style')
334 if self.inline_style:
335 etree.strip_attributes(doc, 'style')
337 kill_tags.add('link')
338 elif self.style or self.javascript:
339 # We must get rid of included stylesheets if Javascript is not
340 # allowed, as you can put Javascript in them
341 for el in list(doc.iter('link')):
342 if 'stylesheet' in el.get('rel', '').lower():
343 # Note this kills alternate stylesheets as well
344 if not self.allow_element(el):
347 kill_tags.add('meta')
348 if self.page_structure:
349 remove_tags.update(('head', 'html', 'title'))
351 # FIXME: is <layer> really embedded?
352 # We should get rid of any <param> tags not inside <applet>;
353 # These are not really valid anyway.
354 for el in list(doc.iter('param')):
356 parent = el.getparent()
357 while parent is not None and parent.tag not in ('applet', 'object'):
358 parent = parent.getparent()
361 kill_tags.update(('applet',))
362 # The alternate contents that are in an iframe are a good fallback:
363 remove_tags.update(('iframe', 'embed', 'layer', 'object', 'param'))
365 # FIXME: ideally we should look at the frame links, but
366 # generally frames don't mix properly with an HTML
368 kill_tags.update(defs.frame_tags)
370 remove_tags.add('form')
371 kill_tags.update(('button', 'input', 'select', 'textarea'))
372 if self.annoying_tags:
373 remove_tags.update(('blink', 'marquee'))
377 for el in doc.iter():
378 if el.tag in kill_tags:
379 if self.allow_element(el):
382 elif el.tag in remove_tags:
383 if self.allow_element(el):
387 if _remove and _remove[0] == doc:
388 # We have to drop the parent-most tag, which we can't
389 # do. Instead we'll rewrite it:
393 elif _kill and _kill[0] == doc:
394 # We have to drop the parent-most element, which we can't
395 # do. Instead we'll clear it:
401 _kill.reverse() # start with innermost tags
407 if self.remove_unknown_tags:
410 "It does not make sense to pass in both allow_tags and remove_unknown_tags")
411 allow_tags = set(defs.tags)
413 # make sure we do not remove comments/PIs if users want them (which is rare enough)
414 if not self.comments:
415 allow_tags.add(etree.Comment)
416 if not self.processing_instructions:
417 allow_tags.add(etree.ProcessingInstruction)
420 for el in doc.iter():
421 if el.tag not in allow_tags:
430 if self.add_nofollow:
431 for el in _find_external_links(doc):
432 if not self.allow_follow(el):
435 if ('nofollow' in rel
436 and ' nofollow ' in (' %s ' % rel)):
438 rel = '%s nofollow' % rel
443 def allow_follow(self, anchor):
445 Override to suppress rel="nofollow" on some anchors.
449 def allow_element(self, el):
451 Decide whether an element is configured to be accepted or rejected.
453 :param el: an element.
454 :return: true to accept the element or false to reject/discard it.
456 if el.tag not in self._tag_link_attrs:
458 attr = self._tag_link_attrs[el.tag]
459 if isinstance(attr, (list, tuple)):
460 for one_attr in attr:
461 url = el.get(one_attr)
464 if not self.allow_embedded_url(el, url):
471 return self.allow_embedded_url(el, url)
473 def allow_embedded_url(self, el, url):
475 Decide whether a URL that was found in an element's attributes or text
476 if configured to be accepted or rejected.
478 :param el: an element.
479 :param url: a URL found on the element.
480 :return: true to accept the URL and false to reject it.
482 if self.whitelist_tags is not None and el.tag not in self.whitelist_tags:
484 scheme, netloc, path, query, fragment = urlsplit(url)
485 netloc = netloc.lower().split(':', 1)[0]
486 if scheme not in ('http', 'https'):
488 if netloc in self.host_whitelist:
492 def kill_conditional_comments(self, doc):
494 IE conditional comments basically embed HTML that the parser
495 doesn't normally see. We can't allow anything like that, so
496 we'll kill any comments that could be conditional.
498 has_conditional_comment = _conditional_comment_re.search
500 doc, lambda el: has_conditional_comment(el.text),
503 def _kill_elements(self, doc, condition, iterate=None):
505 for el in doc.iter(iterate):
511 def _remove_javascript_link(self, link):
512 # links like "j a v a s c r i p t:" might be interpreted in IE
513 new = _substitute_whitespace('', unquote_plus(link))
514 if _is_javascript_scheme(new):
515 # FIXME: should this be None to delete?
519 _substitute_comments = re.compile(r'/\*.*?\*/', re.S).sub
521 def _has_sneaky_javascript(self, style):
523 Depending on the browser, stuff like ``e x p r e s s i o n(...)``
524 can get interpreted, or ``expre/* stuff */ssion(...)``. This
525 checks for attempt to do stuff like this.
527 Typically the response will be to kill the entire style; if you
528 have just a bit of Javascript in the style another rule will catch
529 that and remove only the Javascript from the style; this catches
530 more sneaky attempts.
532 style = self._substitute_comments('', style)
533 style = style.replace('\\', '')
534 style = _substitute_whitespace('', style)
535 style = style.lower()
536 if 'javascript:' in style:
538 if 'expression(' in style:
542 def clean_html(self, html):
543 result_type = type(html)
544 if isinstance(html, basestring):
545 doc = fromstring(html)
547 doc = copy.deepcopy(html)
549 return _transform_result(result_type, doc)
552 clean_html = clean.clean_html
554 ############################################################
556 ############################################################
559 re.compile(r'(?P<body>https?://(?P<host>[a-z0-9._-]+)(?:/[/\-_.,a-z0-9%&?;=~]*)?(?:\([/\-_.,a-z0-9%&?;=~]*\))?)', re.I),
560 # This is conservative, but autolinking can be a bit conservative:
561 re.compile(r'mailto:(?P<body>[a-z0-9._-]+@(?P<host>[a-z0-9_.-]+[a-z]))', re.I),
564 _avoid_elements = ['textarea', 'pre', 'code', 'head', 'select', 'a']
567 re.compile(r'^localhost', re.I),
568 re.compile(r'\bexample\.(?:com|org|net)$', re.I),
569 re.compile(r'^127\.0\.0\.1$'),
572 _avoid_classes = ['nolink']
574 def autolink(el, link_regexes=_link_regexes,
575 avoid_elements=_avoid_elements,
576 avoid_hosts=_avoid_hosts,
577 avoid_classes=_avoid_classes):
579 Turn any URLs into links.
581 It will search for links identified by the given regular
582 expressions (by default mailto and http(s) links).
584 It won't link text in an element in avoid_elements, or an element
585 with a class in avoid_classes. It won't link to anything with a
586 host that matches one of the regular expressions in avoid_hosts
587 (default localhost and 127.0.0.1).
589 If you pass in an element, the element's tail will not be
590 substituted, only the contents of the element.
592 if el.tag in avoid_elements:
594 class_name = el.get('class')
596 class_name = class_name.split()
597 for match_class in avoid_classes:
598 if match_class in class_name:
600 for child in list(el):
601 autolink(child, link_regexes=link_regexes,
602 avoid_elements=avoid_elements,
603 avoid_hosts=avoid_hosts,
604 avoid_classes=avoid_classes)
606 text, tail_children = _link_text(
607 child.tail, link_regexes, avoid_hosts, factory=el.makeelement)
610 index = el.index(child)
611 el[index+1:index+1] = tail_children
613 text, pre_children = _link_text(
614 el.text, link_regexes, avoid_hosts, factory=el.makeelement)
617 el[:0] = pre_children
619 def _link_text(text, link_regexes, avoid_hosts, factory):
624 best_match, best_pos = None, None
625 for regex in link_regexes:
628 match = regex.search(text, pos=regex_pos)
631 host = match.group('host')
632 for host_regex in avoid_hosts:
633 if host_regex.search(host):
634 regex_pos = match.end()
640 if best_pos is None or match.start() < best_pos:
642 best_pos = match.start()
643 if best_match is None:
646 assert not links[-1].tail
647 links[-1].tail = text
649 assert not leading_text
652 link = best_match.group(0)
653 end = best_match.end()
654 if link.endswith('.') or link.endswith(','):
655 # These punctuation marks shouldn't end a link
658 prev_text = text[:best_match.start()]
660 assert not links[-1].tail
661 links[-1].tail = prev_text
663 assert not leading_text
664 leading_text = prev_text
665 anchor = factory('a')
666 anchor.set('href', link)
667 body = best_match.group('body')
670 if body.endswith('.') or body.endswith(','):
675 return leading_text, links
677 def autolink_html(html, *args, **kw):
678 result_type = type(html)
679 if isinstance(html, basestring):
680 doc = fromstring(html)
682 doc = copy.deepcopy(html)
683 autolink(doc, *args, **kw)
684 return _transform_result(result_type, doc)
686 autolink_html.__doc__ = autolink.__doc__
688 ############################################################
690 ############################################################
692 _avoid_word_break_elements = ['pre', 'textarea', 'code']
693 _avoid_word_break_classes = ['nobreak']
695 def word_break(el, max_width=40,
696 avoid_elements=_avoid_word_break_elements,
697 avoid_classes=_avoid_word_break_classes,
698 break_character=unichr(0x200b)):
700 Breaks any long words found in the body of the text (not attributes).
702 Doesn't effect any of the tags in avoid_elements, by default
703 ``<textarea>`` and ``<pre>``
705 Breaks words by inserting ​, which is a unicode character
706 for Zero Width Space character. This generally takes up no space
707 in rendering, but does copy as a space, and in monospace contexts
708 usually takes up space.
710 See http://www.cs.tut.fi/~jkorpela/html/nobr.html for a discussion
712 # Character suggestion of ​ comes from:
713 # http://www.cs.tut.fi/~jkorpela/html/nobr.html
714 if el.tag in _avoid_word_break_elements:
716 class_name = el.get('class')
719 class_name = class_name.split()
720 for avoid in avoid_classes:
721 if avoid in class_name:
727 el.text = _break_text(el.text, max_width, break_character)
729 word_break(child, max_width=max_width,
730 avoid_elements=avoid_elements,
731 avoid_classes=avoid_classes,
732 break_character=break_character)
734 child.tail = _break_text(child.tail, max_width, break_character)
736 def word_break_html(html, *args, **kw):
737 result_type = type(html)
738 doc = fromstring(html)
739 word_break(doc, *args, **kw)
740 return _transform_result(result_type, doc)
742 def _break_text(text, max_width, break_character):
745 if len(word) > max_width:
746 replacement = _insert_break(word, max_width, break_character)
747 text = text.replace(word, replacement)
750 _break_prefer_re = re.compile(r'[^a-z]', re.I)
752 def _insert_break(word, width, break_character):
755 while len(word) > width:
757 breaks = list(_break_prefer_re.finditer(start))
759 last_break = breaks[-1]
760 # Only walk back up to 10 characters to find a nice break:
761 if last_break.end() > width-10:
762 # FIXME: should the break character be at the end of the
763 # chunk, or the beginning of the next chunk?
764 start = word[:last_break.end()]
765 result += start + break_character
766 word = word[len(start):]