Source code for bleach.sanitizer

from __future__ import unicode_literals
import re
from xml.sax.saxutils import unescape

import html5lib
from html5lib.constants import namespaces
from html5lib.filters import sanitizer
from html5lib.serializer import HTMLSerializer

from bleach.encoding import force_unicode
from bleach.utils import alphabetize_attributes

#: List of allowed tags

#: Map of allowed attributes by tag
    'a': ['href', 'title'],
    'abbr': ['title'],
    'acronym': ['title'],

#: List of allowed styles

#: List of allowed protocols
ALLOWED_PROTOCOLS = ['http', 'https', 'mailto']

[docs]class Cleaner(object): """Cleaner for cleaning HTML fragments of malicious content This cleaner is a security-focused function whose sole purpose is to remove malicious content from a string such that it can be displayed as content in a web page. This cleaner is not designed to use to transform content to be used in non-web-page contexts. To use:: from bleach.sanitizer import Cleaner cleaner = Cleaner() for text in all_the_yucky_things: sanitized = cleaner.clean(text) """ def __init__(self, tags=ALLOWED_TAGS, attributes=ALLOWED_ATTRIBUTES, styles=ALLOWED_STYLES, protocols=ALLOWED_PROTOCOLS, strip=False, strip_comments=True, filters=None): """Initializes a Cleaner :arg list tags: allowed list of tags; defaults to ``bleach.sanitizer.ALLOWED_TAGS`` :arg dict attributes: allowed attributes; can be a callable, list or dict; defaults to ``bleach.sanitizer.ALLOWED_ATTRIBUTES`` :arg list styles: allowed list of css styles; defaults to ``bleach.sanitizer.ALLOWED_STYLES`` :arg list protocols: allowed list of protocols for links; defaults to ``bleach.sanitizer.ALLOWED_PROTOCOLS`` :arg bool strip: whether or not to strip disallowed elements :arg bool strip_comments: whether or not to strip HTML comments :arg list filters: list of html5lib Filter classes to pass streamed content through .. seealso:: .. Warning:: Using filters changes the output of ``bleach.Cleaner.clean``. Make sure the way the filters change the output are secure. """ self.tags = tags self.attributes = attributes self.styles = styles self.protocols = protocols self.strip = strip self.strip_comments = strip_comments self.filters = filters or [] self.parser = html5lib.HTMLParser(namespaceHTMLElements=False) self.walker = html5lib.getTreeWalker('etree') self.serializer = HTMLSerializer( quote_attr_values='always', omit_optional_tags=False, # Bleach has its own sanitizer, so don't use the html5lib one sanitize=False, # Bleach sanitizer alphabetizes already, so don't use the html5lib one alphabetical_attributes=False, )
[docs] def clean(self, text): """Cleans text and returns sanitized result as unicode :arg str text: text to be cleaned :returns: sanitized text as unicode """ if not text: return u'' text = force_unicode(text) dom = self.parser.parseFragment(text) filtered = BleachSanitizerFilter( source=self.walker(dom), # Bleach-sanitizer-specific things attributes=self.attributes, strip_disallowed_elements=self.strip, strip_html_comments=self.strip_comments, # html5lib-sanitizer things allowed_elements=self.tags, allowed_css_properties=self.styles, allowed_protocols=self.protocols, allowed_svg_properties=[], ) # Apply any filters after the BleachSanitizerFilter for filter_class in self.filters: filtered = filter_class(source=filtered) return self.serializer.render(filtered)
def attribute_filter_factory(attributes): """Generates attribute filter function for the given attributes value The attributes value can take one of several shapes. This returns a filter function appropriate to the attributes value. One nice thing about this is that there's less if/then shenanigans in the ``allow_token`` method. """ if callable(attributes): return attributes if isinstance(attributes, dict): def _attr_filter(tag, attr, value): if tag in attributes: attr_val = attributes[tag] if callable(attr_val): return attr_val(tag, attr, value) if attr in attr_val: return True if '*' in attributes: attr_val = attributes['*'] if callable(attr_val): return attr_val(tag, attr, value) return attr in attr_val return False return _attr_filter if isinstance(attributes, list): def _attr_filter(tag, attr, value): return attr in attributes return _attr_filter raise ValueError('attributes needs to be a callable, a list or a dict')
[docs]class BleachSanitizerFilter(sanitizer.Filter): """html5lib Filter that sanitizes text This filter can be used anywhere html5lib filters can be used. """ def __init__(self, source, attributes=ALLOWED_ATTRIBUTES, strip_disallowed_elements=False, strip_html_comments=True, **kwargs): """Creates a BleachSanitizerFilter instance :arg Treewalker source: stream :arg list tags: allowed list of tags; defaults to ``bleach.sanitizer.ALLOWED_TAGS`` :arg dict attributes: allowed attributes; can be a callable, list or dict; defaults to ``bleach.sanitizer.ALLOWED_ATTRIBUTES`` :arg list styles: allowed list of css styles; defaults to ``bleach.sanitizer.ALLOWED_STYLES`` :arg list protocols: allowed list of protocols for links; defaults to ``bleach.sanitizer.ALLOWED_PROTOCOLS`` :arg bool strip_disallowed_elements: whether or not to strip disallowed elements :arg bool strip_html_comments: whether or not to strip HTML comments """ self.attr_filter = attribute_filter_factory(attributes) self.strip_disallowed_elements = strip_disallowed_elements self.strip_html_comments = strip_html_comments return super(BleachSanitizerFilter, self).__init__(source, **kwargs) def sanitize_token(self, token): """Sanitize a token either by HTML-encoding or dropping. Unlike sanitizer.Filter, allowed_attributes can be a dict of {'tag': ['attribute', 'pairs'], 'tag': callable}. Here callable is a function with two arguments of attribute name and value. It should return true of false. Also gives the option to strip tags instead of encoding. """ token_type = token['type'] if token_type in ['StartTag', 'EndTag', 'EmptyTag']: if token['name'] in self.allowed_elements: return self.allow_token(token) elif self.strip_disallowed_elements: pass else: if 'data' in token: # Alphabetize the attributes before calling .disallowed_token() # so that the resulting string is stable token['data'] = alphabetize_attributes(token['data']) return self.disallowed_token(token) elif token_type == 'Comment': if not self.strip_html_comments: return token else: return token def allow_token(self, token): """Handles the case where we're allowing the tag""" if 'data' in token: # Loop through all the attributes and drop the ones that are not # allowed, are unsafe or break other rules. Additionally, fix # attribute values that need fixing. # # At the end of this loop, we have the final set of attributes # we're keeping. attrs = {} for namespaced_name, val in token['data'].items(): namespace, name = namespaced_name # Drop attributes that are not explicitly allowed # # NOTE(willkg): We pass in the attribute name--not a namespaced # name. if not self.attr_filter(token['name'], name, val): continue # Look at attributes that have uri values if namespaced_name in self.attr_val_is_uri: val_unescaped = re.sub( "[`\000-\040\177-\240\s]+", '', unescape(val)).lower() # Remove replacement characters from unescaped characters. val_unescaped = val_unescaped.replace("\ufffd", "") # Drop attributes with uri values that have protocols that # aren't allowed if (re.match(r'^[a-z0-9][-+.a-z0-9]*:', val_unescaped) and (val_unescaped.split(':')[0] not in self.allowed_protocols)): continue # Drop values in svg attrs with non-local IRIs if namespaced_name in self.svg_attr_val_allows_ref: new_val = re.sub(r'url\s*\(\s*[^#\s][^)]+?\)', ' ', unescape(val)) new_val = new_val.strip() if not new_val: continue else: # Replace the val with the unescaped version because # it's a iri val = new_val # Drop href and xlink:href attr for svg elements with non-local IRIs if (None, token['name']) in self.svg_allow_local_href: if namespaced_name in [(None, 'href'), (namespaces['xlink'], 'href')]: if'^\s*[^#\s]', val): continue # If it's a style attribute, sanitize it if namespaced_name == (None, u'style'): val = self.sanitize_css(val) # At this point, we want to keep the attribute, so add it in attrs[namespaced_name] = val token['data'] = alphabetize_attributes(attrs) return token def sanitize_css(self, style): """Sanitizes css in style tags""" # disallow urls style = re.compile('url\s*\(\s*[^\s)]+?\s*\)\s*').sub(' ', style) # gauntlet # Validate the css in the style tag and if it's not valid, then drop # the whole thing. parts = style.split(';') gauntlet = re.compile( r"""^([-/:,#%.'"\sa-zA-Z0-9!]|\w-\w|'[\s\w]+'\s*|"[\s\w]+"|\([\d,%\.\s]+\))*$""" ) for part in parts: if not gauntlet.match(part): return '' if not re.match("^\s*([-\w]+\s*:[^:;]*(;\s*|$))*$", style): return '' clean = [] for prop, value in re.findall('([-\w]+)\s*:\s*([^:;]*)', style): if not value: continue if prop.lower() in self.allowed_css_properties: clean.append(prop + ': ' + value + ';') elif prop.lower() in self.allowed_svg_properties: clean.append(prop + ': ' + value + ';') return ' '.join(clean)