alpcentaur
/
brieftaube

"""A cleanup tool for HTML.

Removes unwanted tags and content.  See the `Cleaner` class fordetails."""

import reimport copytry:    from urlparse import urlsplit    from urllib import unquote_plusexcept ImportError:    # Python 3    from urllib.parse import urlsplit, unquote_plusfrom lxml import etreefrom lxml.html import defsfrom lxml.html import fromstring, XHTML_NAMESPACEfrom lxml.html import xhtml_to_html, _transform_result
try:    unichrexcept NameError:    # Python 3    unichr = chrtry:    unicodeexcept NameError:    # Python 3    unicode = strtry:    bytesexcept NameError:    # Python < 2.6    bytes = strtry:    basestringexcept NameError:    basestring = (str, bytes)

__all__ = ['clean_html', 'clean', 'Cleaner', 'autolink', 'autolink_html',           'word_break', 'word_break_html']
# Look at http://code.sixapart.com/trac/livejournal/browser/trunk/cgi-bin/cleanhtml.pl#   Particularly the CSS cleaning; most of the tag cleaning is integrated now# I have multiple kinds of schemes searched; but should schemes be#   whitelisted instead?# max height?# remove images?  Also in CSS?  background attribute?# Some way to whitelist object, iframe, etc (e.g., if you want to#   allow *just* embedded YouTube movies)# Log what was deleted and why?# style="behavior: ..." might be bad in IE?# Should we have something for just <meta http-equiv>?  That's the worst of the#   metas.# UTF-7 detections?  Example:#     <HEAD><META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=UTF-7"> </HEAD>+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-#   you don't always have to have the charset set, if the page has no charset#   and there's UTF7-like code in it.# Look at these tests: http://htmlpurifier.org/live/smoketests/xssAttacks.php

# This is an IE-specific construct you can have in a stylesheet to# run some Javascript:_css_javascript_re = re.compile(    r'expression\s*\(.*?\)', re.S|re.I)
# Do I have to worry about @\nimport?_css_import_re = re.compile(    r'@\s*import', re.I)
# All kinds of schemes besides just javascript: that can cause# execution:_is_image_dataurl = re.compile(    r'^data:image/.+;base64', re.I).search_is_possibly_malicious_scheme = re.compile(    r'(?:javascript|jscript|livescript|vbscript|data|about|mocha):',    re.I).searchdef _is_javascript_scheme(s):    if _is_image_dataurl(s):        return None    return _is_possibly_malicious_scheme(s)
_substitute_whitespace = re.compile(r'[\s\x00-\x08\x0B\x0C\x0E-\x19]+').sub# FIXME: should data: be blocked?
# FIXME: check against: http://msdn2.microsoft.com/en-us/library/ms537512.aspx_conditional_comment_re = re.compile(    r'\[if[\s\n\r]+.*?][\s\n\r]*>', re.I|re.S)
_find_styled_elements = etree.XPath(    "descendant-or-self::*[@style]")
_find_external_links = etree.XPath(    ("descendant-or-self::a  [normalize-space(@href) and substring(normalize-space(@href),1,1) != '#'] |"     "descendant-or-self::x:a[normalize-space(@href) and substring(normalize-space(@href),1,1) != '#']"),    namespaces={'x':XHTML_NAMESPACE})

class Cleaner(object):    """
    Instances cleans the document of each of the possible offending    elements.  The cleaning is controlled by attributes; you can    override attributes in a subclass, or set them in the constructor.
    ``scripts``:        Removes any ``<script>`` tags.
    ``javascript``:        Removes any Javascript, like an ``onclick`` attribute. Also removes stylesheets        as they could contain Javascript.
    ``comments``:        Removes any comments.
    ``style``:        Removes any style tags.
    ``inline_style``        Removes any style attributes.  Defaults to the value of the ``style`` option.
    ``links``:        Removes any ``<link>`` tags
    ``meta``:        Removes any ``<meta>`` tags
    ``page_structure``:        Structural parts of a page: ``<head>``, ``<html>``, ``<title>``.
    ``processing_instructions``:        Removes any processing instructions.
    ``embedded``:        Removes any embedded objects (flash, iframes)
    ``frames``:        Removes any frame-related tags
    ``forms``:        Removes any form tags
    ``annoying_tags``:        Tags that aren't *wrong*, but are annoying.  ``<blink>`` and ``<marquee>``
    ``remove_tags``:        A list of tags to remove.  Only the tags will be removed,        their content will get pulled up into the parent tag.
    ``kill_tags``:        A list of tags to kill.  Killing also removes the tag's content,        i.e. the whole subtree, not just the tag itself.
    ``allow_tags``:        A list of tags to include (default include all).
    ``remove_unknown_tags``:        Remove any tags that aren't standard parts of HTML.
    ``safe_attrs_only``:        If true, only include 'safe' attributes (specifically the list        from the feedparser HTML sanitisation web site).
    ``safe_attrs``:        A set of attribute names to override the default list of attributes        considered 'safe' (when safe_attrs_only=True).
    ``add_nofollow``:        If true, then any <a> tags will have ``rel="nofollow"`` added to them.
    ``host_whitelist``:        A list or set of hosts that you can use for embedded content        (for content like ``<object>``, ``<link rel="stylesheet">``, etc).        You can also implement/override the method        ``allow_embedded_url(el, url)`` or ``allow_element(el)`` to        implement more complex rules for what can be embedded.        Anything that passes this test will be shown, regardless of        the value of (for instance) ``embedded``.
        Note that this parameter might not work as intended if you do not        make the links absolute before doing the cleaning.
        Note that you may also need to set ``whitelist_tags``.
    ``whitelist_tags``:        A set of tags that can be included with ``host_whitelist``.        The default is ``iframe`` and ``embed``; you may wish to        include other tags like ``script``, or you may want to        implement ``allow_embedded_url`` for more control.  Set to None to        include all tags.
    This modifies the document *in place*.    """

    scripts = True    javascript = True    comments = True    style = False    inline_style = None    links = True    meta = True    page_structure = True    processing_instructions = True    embedded = True    frames = True    forms = True    annoying_tags = True    remove_tags = None    allow_tags = None    kill_tags = None    remove_unknown_tags = True    safe_attrs_only = True    safe_attrs = defs.safe_attrs    add_nofollow = False    host_whitelist = ()    whitelist_tags = set(['iframe', 'embed'])
    def __init__(self, **kw):        for name, value in kw.items():            if not hasattr(self, name):                raise TypeError(                    "Unknown parameter: %s=%r" % (name, value))            setattr(self, name, value)        if self.inline_style is None and 'inline_style' not in kw:            self.inline_style = self.style
    # Used to lookup the primary URL for a given tag that is up for    # removal:    _tag_link_attrs = dict(        script='src',        link='href',        # From: http://java.sun.com/j2se/1.4.2/docs/guide/misc/applet.html        # From what I can tell, both attributes can contain a link:        applet=['code', 'object'],        iframe='src',        embed='src',        layer='src',        # FIXME: there doesn't really seem like a general way to figure out what        # links an <object> tag uses; links often go in <param> tags with values        # that we don't really know.  You'd have to have knowledge about specific        # kinds of plugins (probably keyed off classid), and match against those.        ##object=?,        # FIXME: not looking at the action currently, because it is more complex        # than than -- if you keep the form, you should keep the form controls.        ##form='action',        a='href',        )
    def __call__(self, doc):        """
        Cleans the document.        """
        if hasattr(doc, 'getroot'):            # ElementTree instance, instead of an element            doc = doc.getroot()        # convert XHTML to HTML        xhtml_to_html(doc)        # Normalize a case that IE treats <image> like <img>, and that        # can confuse either this step or later steps.        for el in doc.iter('image'):            el.tag = 'img'        if not self.comments:            # Of course, if we were going to kill comments anyway, we don't            # need to worry about this            self.kill_conditional_comments(doc)
        kill_tags = set(self.kill_tags or ())        remove_tags = set(self.remove_tags or ())        allow_tags = set(self.allow_tags or ())
        if self.scripts:            kill_tags.add('script')        if self.safe_attrs_only:            safe_attrs = set(self.safe_attrs)            for el in doc.iter(etree.Element):                attrib = el.attrib                for aname in attrib.keys():                    if aname not in safe_attrs:                        del attrib[aname]        if self.javascript:            if not (self.safe_attrs_only and                    self.safe_attrs == defs.safe_attrs):                # safe_attrs handles events attributes itself                for el in doc.iter(etree.Element):                    attrib = el.attrib                    for aname in attrib.keys():                        if aname.startswith('on'):                            del attrib[aname]            doc.rewrite_links(self._remove_javascript_link,                              resolve_base_href=False)            # If we're deleting style then we don't have to remove JS links            # from styles, otherwise...            if not self.inline_style:                for el in _find_styled_elements(doc):                    old = el.get('style')                    new = _css_javascript_re.sub('', old)                    new = _css_import_re.sub('', new)                    if self._has_sneaky_javascript(new):                        # Something tricky is going on...                        del el.attrib['style']                    elif new != old:                        el.set('style', new)            if not self.style:                for el in list(doc.iter('style')):                    if el.get('type', '').lower().strip() == 'text/javascript':                        el.drop_tree()                        continue                    old = el.text or ''                    new = _css_javascript_re.sub('', old)                    # The imported CSS can do anything; we just can't allow:                    new = _css_import_re.sub('', old)                    if self._has_sneaky_javascript(new):                        # Something tricky is going on...                        el.text = '/* deleted */'                    elif new != old:                        el.text = new        if self.comments or self.processing_instructions:            # FIXME: why either?  I feel like there's some obscure reason            # because you can put PIs in comments...?  But I've already            # forgotten it            kill_tags.add(etree.Comment)        if self.processing_instructions:            kill_tags.add(etree.ProcessingInstruction)        if self.style:            kill_tags.add('style')        if self.inline_style:            etree.strip_attributes(doc, 'style')        if self.links:            kill_tags.add('link')        elif self.style or self.javascript:            # We must get rid of included stylesheets if Javascript is not            # allowed, as you can put Javascript in them            for el in list(doc.iter('link')):                if 'stylesheet' in el.get('rel', '').lower():                    # Note this kills alternate stylesheets as well                    if not self.allow_element(el):                        el.drop_tree()        if self.meta:            kill_tags.add('meta')        if self.page_structure:            remove_tags.update(('head', 'html', 'title'))        if self.embedded:            # FIXME: is <layer> really embedded?            # We should get rid of any <param> tags not inside <applet>;            # These are not really valid anyway.            for el in list(doc.iter('param')):                found_parent = False                parent = el.getparent()                while parent is not None and parent.tag not in ('applet', 'object'):                    parent = parent.getparent()                if parent is None:                    el.drop_tree()            kill_tags.update(('applet',))            # The alternate contents that are in an iframe are a good fallback:            remove_tags.update(('iframe', 'embed', 'layer', 'object', 'param'))        if self.frames:            # FIXME: ideally we should look at the frame links, but            # generally frames don't mix properly with an HTML            # fragment anyway.            kill_tags.update(defs.frame_tags)        if self.forms:            remove_tags.add('form')            kill_tags.update(('button', 'input', 'select', 'textarea'))        if self.annoying_tags:            remove_tags.update(('blink', 'marquee'))
        _remove = []        _kill = []        for el in doc.iter():            if el.tag in kill_tags:                if self.allow_element(el):                    continue                _kill.append(el)            elif el.tag in remove_tags:                if self.allow_element(el):                    continue                _remove.append(el)
        if _remove and _remove[0] == doc:            # We have to drop the parent-most tag, which we can't            # do.  Instead we'll rewrite it:            el = _remove.pop(0)            el.tag = 'div'            el.attrib.clear()        elif _kill and _kill[0] == doc:            # We have to drop the parent-most element, which we can't            # do.  Instead we'll clear it:            el = _kill.pop(0)            if el.tag != 'html':                el.tag = 'div'            el.clear()
        _kill.reverse() # start with innermost tags        for el in _kill:            el.drop_tree()        for el in _remove:            el.drop_tag()
        if self.remove_unknown_tags:            if allow_tags:                raise ValueError(                    "It does not make sense to pass in both allow_tags and remove_unknown_tags")            allow_tags = set(defs.tags)        if allow_tags:            bad = []            for el in doc.iter():                if el.tag not in allow_tags:                    bad.append(el)            if bad:                if bad[0] is doc:                    el = bad.pop(0)                    el.tag = 'div'                    el.attrib.clear()                for el in bad:                    el.drop_tag()        if self.add_nofollow:            for el in _find_external_links(doc):                if not self.allow_follow(el):                    rel = el.get('rel')                    if rel:                        if ('nofollow' in rel                                and ' nofollow ' in (' %s ' % rel)):                            continue                        rel = '%s nofollow' % rel                    else:                        rel = 'nofollow'                    el.set('rel', rel)
    def allow_follow(self, anchor):        """
        Override to suppress rel="nofollow" on some anchors.        """
        return False
    def allow_element(self, el):        if el.tag not in self._tag_link_attrs:            return False        attr = self._tag_link_attrs[el.tag]        if isinstance(attr, (list, tuple)):            for one_attr in attr:                url = el.get(one_attr)                if not url:                    return False                if not self.allow_embedded_url(el, url):                    return False            return True        else:            url = el.get(attr)            if not url:                return False            return self.allow_embedded_url(el, url)
    def allow_embedded_url(self, el, url):        if (self.whitelist_tags is not None            and el.tag not in self.whitelist_tags):            return False        scheme, netloc, path, query, fragment = urlsplit(url)        netloc = netloc.lower().split(':', 1)[0]        if scheme not in ('http', 'https'):            return False        if netloc in self.host_whitelist:            return True        return False
    def kill_conditional_comments(self, doc):        """
        IE conditional comments basically embed HTML that the parser        doesn't normally see.  We can't allow anything like that, so        we'll kill any comments that could be conditional.        """
        bad = []        self._kill_elements(            doc, lambda el: _conditional_comment_re.search(el.text),            etree.Comment)                
    def _kill_elements(self, doc, condition, iterate=None):        bad = []        for el in doc.iter(iterate):            if condition(el):                bad.append(el)        for el in bad:            el.drop_tree()
    def _remove_javascript_link(self, link):        # links like "j a v a s c r i p t:" might be interpreted in IE        new = _substitute_whitespace('', unquote_plus(link))        if _is_javascript_scheme(new):            # FIXME: should this be None to delete?            return ''        return link
    _substitute_comments = re.compile(r'/\*.*?\*/', re.S).sub
    def _has_sneaky_javascript(self, style):        """
        Depending on the browser, stuff like ``e x p r e s s i o n(...)``        can get interpreted, or ``expre/* stuff */ssion(...)``.  This        checks for attempt to do stuff like this.
        Typically the response will be to kill the entire style; if you        have just a bit of Javascript in the style another rule will catch        that and remove only the Javascript from the style; this catches        more sneaky attempts.        """
        style = self._substitute_comments('', style)        style = style.replace('\\', '')        style = _substitute_whitespace('', style)        style = style.lower()        if 'javascript:' in style:            return True        if 'expression(' in style:            return True        return False
    def clean_html(self, html):        result_type = type(html)        if isinstance(html, basestring):            doc = fromstring(html)        else:            doc = copy.deepcopy(html)        self(doc)        return _transform_result(result_type, doc)
clean = Cleaner()clean_html = clean.clean_html
############################################################## Autolinking############################################################
_link_regexes = [    re.compile(r'(?P<body>https?://(?P<host>[a-z0-9._-]+)(?:/[/\-_.,a-z0-9%&?;=~]*)?(?:\([/\-_.,a-z0-9%&?;=~]*\))?)', re.I),    # This is conservative, but autolinking can be a bit conservative:    re.compile(r'mailto:(?P<body>[a-z0-9._-]+@(?P<host>[a-z0-9_.-]+[a-z]))', re.I),    ]
_avoid_elements = ['textarea', 'pre', 'code', 'head', 'select', 'a']
_avoid_hosts = [    re.compile(r'^localhost', re.I),    re.compile(r'\bexample\.(?:com|org|net)$', re.I),    re.compile(r'^127\.0\.0\.1$'),    ]
_avoid_classes = ['nolink']
def autolink(el, link_regexes=_link_regexes,             avoid_elements=_avoid_elements,             avoid_hosts=_avoid_hosts,             avoid_classes=_avoid_classes):    """
    Turn any URLs into links.
    It will search for links identified by the given regular    expressions (by default mailto and http(s) links).
    It won't link text in an element in avoid_elements, or an element    with a class in avoid_classes.  It won't link to anything with a    host that matches one of the regular expressions in avoid_hosts    (default localhost and 127.0.0.1).
    If you pass in an element, the element's tail will not be    substituted, only the contents of the element.    """
    if el.tag in avoid_elements:        return    class_name = el.get('class')    if class_name:        class_name = class_name.split()        for match_class in avoid_classes:            if match_class in class_name:                return    for child in list(el):        autolink(child, link_regexes=link_regexes,                 avoid_elements=avoid_elements,                 avoid_hosts=avoid_hosts,                 avoid_classes=avoid_classes)        if child.tail:            text, tail_children = _link_text(                child.tail, link_regexes, avoid_hosts, factory=el.makeelement)            if tail_children:                child.tail = text                index = el.index(child)                el[index+1:index+1] = tail_children    if el.text:        text, pre_children = _link_text(            el.text, link_regexes, avoid_hosts, factory=el.makeelement)        if pre_children:            el.text = text            el[:0] = pre_children
def _link_text(text, link_regexes, avoid_hosts, factory):    leading_text = ''    links = []    last_pos = 0    while 1:        best_match, best_pos = None, None        for regex in link_regexes:            regex_pos = last_pos            while 1:                match = regex.search(text, pos=regex_pos)                if match is None:                    break                host = match.group('host')                for host_regex in avoid_hosts:                    if host_regex.search(host):                        regex_pos = match.end()                        break                else:                    break            if match is None:                continue            if best_pos is None or match.start() < best_pos:                best_match = match                best_pos = match.start()        if best_match is None:            # No more matches            if links:                assert not links[-1].tail                links[-1].tail = text            else:                assert not leading_text                leading_text = text            break        link = best_match.group(0)        end = best_match.end()        if link.endswith('.') or link.endswith(','):            # These punctuation marks shouldn't end a link            end -= 1            link = link[:-1]        prev_text = text[:best_match.start()]        if links:            assert not links[-1].tail            links[-1].tail = prev_text        else:            assert not leading_text            leading_text = prev_text        anchor = factory('a')        anchor.set('href', link)        body = best_match.group('body')        if not body:            body = link        if body.endswith('.') or body.endswith(','):            body = body[:-1]        anchor.text = body        links.append(anchor)        text = text[end:]    return leading_text, links                def autolink_html(html, *args, **kw):    result_type = type(html)    if isinstance(html, basestring):        doc = fromstring(html)    else:        doc = copy.deepcopy(html)    autolink(doc, *args, **kw)    return _transform_result(result_type, doc)
autolink_html.__doc__ = autolink.__doc__
############################################################## Word wrapping############################################################
_avoid_word_break_elements = ['pre', 'textarea', 'code']_avoid_word_break_classes = ['nobreak']
def word_break(el, max_width=40,               avoid_elements=_avoid_word_break_elements,               avoid_classes=_avoid_word_break_classes,               break_character=unichr(0x200b)):    """
    Breaks any long words found in the body of the text (not attributes).
    Doesn't effect any of the tags in avoid_elements, by default    ``<textarea>`` and ``<pre>``
    Breaks words by inserting &#8203;, which is a unicode character    for Zero Width Space character.  This generally takes up no space    in rendering, but does copy as a space, and in monospace contexts    usually takes up space.
    See http://www.cs.tut.fi/~jkorpela/html/nobr.html for a discussion    """
    # Character suggestion of &#8203 comes from:    #   http://www.cs.tut.fi/~jkorpela/html/nobr.html    if el.tag in _avoid_word_break_elements:        return    class_name = el.get('class')    if class_name:        dont_break = False        class_name = class_name.split()        for avoid in avoid_classes:            if avoid in class_name:                dont_break = True                break        if dont_break:            return    if el.text:        el.text = _break_text(el.text, max_width, break_character)    for child in el:        word_break(child, max_width=max_width,                   avoid_elements=avoid_elements,                   avoid_classes=avoid_classes,                   break_character=break_character)        if child.tail:            child.tail = _break_text(child.tail, max_width, break_character)
def word_break_html(html, *args, **kw):    result_type = type(html)    doc = fromstring(html)    word_break(doc, *args, **kw)    return _transform_result(result_type, doc)
def _break_text(text, max_width, break_character):    words = text.split()    for word in words:        if len(word) > max_width:            replacement = _insert_break(word, max_width, break_character)            text = text.replace(word, replacement)    return text
_break_prefer_re = re.compile(r'[^a-z]', re.I)
def _insert_break(word, width, break_character):    orig_word = word    result = ''    while len(word) > width:        start = word[:width]        breaks = list(_break_prefer_re.finditer(start))        if breaks:            last_break = breaks[-1]            # Only walk back up to 10 characters to find a nice break:            if last_break.end() > width-10:                # FIXME: should the break character be at the end of the                # chunk, or the beginning of the next chunk?                start = word[:last_break.end()]        result += start + break_character        word = word[len(start):]    result += word    return result