shell bypass 403
UnknownSec Shell
:
/
usr
/
lib64
/
python2.7
/
site-packages
/
lxml
/
html
/ [
drwxr-xr-x
]
upload
mass deface
mass delete
console
info server
name :
clean.py
"""A cleanup tool for HTML. Removes unwanted tags and content. See the `Cleaner` class for details. """ import copy import re import sys try: from urlparse import urlsplit except ImportError: # Python 3 from urllib.parse import urlsplit from lxml import etree from lxml.html import defs from lxml.html import fromstring, XHTML_NAMESPACE from lxml.html import xhtml_to_html, _transform_result try: unichr except NameError: # Python 3 unichr = chr try: unicode except NameError: # Python 3 unicode = str try: bytes except NameError: # Python < 2.6 bytes = str try: basestring except 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: _replace_css_javascript = re.compile( r'expression\s*\(.*?\)', re.S|re.I).sub # Do I have to worry about @\nimport? _replace_css_import = re.compile( r'@\s*import', re.I).sub _looks_like_tag_content = re.compile( r'</?[a-zA-Z]+|\son[a-zA-Z]+\s*=', *((re.ASCII,) if sys.version_info[0] >= 3 else ())).search # All kinds of schemes besides just javascript: that can cause # execution: _find_image_dataurls = re.compile( r'^data:image/(.+);base64,', re.I).findall _is_possibly_malicious_scheme = re.compile( r'(javascript|jscript|livescript|vbscript|data|about|mocha):', re.I).findall # SVG images can contain script content _is_unsafe_image_type = re.compile(r"(xml|svg)", re.I).findall def _is_javascript_scheme(s): is_image_url = False for image_type in _find_image_dataurls(s): is_image_url = True if _is_unsafe_image_type(image_type): return True if is_image_url: return False return bool(_is_possibly_malicious_scheme(s)) _substitute_whitespace = re.compile(r'[\s\x00-\x08\x0B\x0C\x0E-\x19]+').sub # 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 = _replace_css_javascript('', old) new = _replace_css_import('', 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 = _replace_css_javascript('', old) # The imported CSS can do anything; we just can't allow: new = _replace_css_import('', new) 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('', 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 if '@import' in style: return True if '</noscript' in style: # e.g. '<noscript><style><a title="</noscript><img src=x onerror=alert(1)>">' return True if _looks_like_tag_content(style): # e.g. '<math><style><img src=x onerror=alert(1)></style></math>' 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 ​, 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 ​ 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
© 2024 UnknownSec