# Copyright 2010-2022 Kurt McKee # Copyright 2002-2008 Mark Pilgrim # All rights reserved. # # This file is a part of feedparser. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are met: # # * Redistributions of source code must retain the above copyright notice, # this list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above copyright notice, # this list of conditions and the following disclaimer in the documentation # and/or other materials provided with the distribution. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS' # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE # POSSIBILITY OF SUCH DAMAGE. import re from .html import BaseHTMLProcessor from .urls import make_safe_absolute_uri class HTMLSanitizer(BaseHTMLProcessor): acceptable_elements = { 'a', 'abbr', 'acronym', 'address', 'area', 'article', 'aside', 'audio', 'b', 'big', 'blockquote', 'br', 'button', 'canvas', 'caption', 'center', 'cite', 'code', 'col', 'colgroup', 'command', 'datagrid', 'datalist', 'dd', 'del', 'details', 'dfn', 'dialog', 'dir', 'div', 'dl', 'dt', 'em', 'event-source', 'fieldset', 'figcaption', 'figure', 'font', 'footer', 'form', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'header', 'hr', 'i', 'img', 'input', 'ins', 'kbd', 'keygen', 'label', 'legend', 'li', 'm', 'map', 'menu', 'meter', 'multicol', 'nav', 'nextid', 'noscript', 'ol', 'optgroup', 'option', 'output', 'p', 'pre', 'progress', 'q', 's', 'samp', 'section', 'select', 'small', 'sound', 'source', 'spacer', 'span', 'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'textarea', 'tfoot', 'th', 'thead', 'time', 'tr', 'tt', 'u', 'ul', 'var', 'video', } acceptable_attributes = { 'abbr', 'accept', 'accept-charset', 'accesskey', 'action', 'align', 'alt', 'autocomplete', 'autofocus', 'axis', 'background', 'balance', 'bgcolor', 'bgproperties', 'border', 'bordercolor', 'bordercolordark', 'bordercolorlight', 'bottompadding', 'cellpadding', 'cellspacing', 'ch', 'challenge', 'char', 'charoff', 'charset', 'checked', 'choff', 'cite', 'class', 'clear', 'color', 'cols', 'colspan', 'compact', 'contenteditable', 'controls', 'coords', 'data', 'datafld', 'datapagesize', 'datasrc', 'datetime', 'default', 'delay', 'dir', 'disabled', 'draggable', 'dynsrc', 'enctype', 'end', 'face', 'for', 'form', 'frame', 'galleryimg', 'gutter', 'headers', 'height', 'hidden', 'hidefocus', 'high', 'href', 'hreflang', 'hspace', 'icon', 'id', 'inputmode', 'ismap', 'keytype', 'label', 'lang', 'leftspacing', 'list', 'longdesc', 'loop', 'loopcount', 'loopend', 'loopstart', 'low', 'lowsrc', 'max', 'maxlength', 'media', 'method', 'min', 'multiple', 'name', 'nohref', 'noshade', 'nowrap', 'open', 'optimum', 'pattern', 'ping', 'point-size', 'poster', 'pqg', 'preload', 'prompt', 'radiogroup', 'readonly', 'rel', 'repeat-max', 'repeat-min', 'replace', 'required', 'rev', 'rightspacing', 'rows', 'rowspan', 'rules', 'scope', 'selected', 'shape', 'size', 'span', 'src', 'start', 'step', 'style', 'summary', 'suppress', 'tabindex', 'target', 'template', 'title', 'toppadding', 'type', 'unselectable', 'urn', 'usemap', 'valign', 'value', 'variable', 'volume', 'vrml', 'vspace', 'width', 'wrap', 'xml:lang', } unacceptable_elements_with_end_tag = { 'applet', 'script', 'style', } acceptable_css_properties = { 'azimuth', 'background-color', 'border-bottom-color', 'border-collapse', 'border-color', 'border-left-color', 'border-right-color', 'border-top-color', 'clear', 'color', 'cursor', 'direction', 'display', 'elevation', 'float', 'font', 'font-family', 'font-size', 'font-style', 'font-variant', 'font-weight', 'height', 'letter-spacing', 'line-height', 'overflow', 'pause', 'pause-after', 'pause-before', 'pitch', 'pitch-range', 'richness', 'speak', 'speak-header', 'speak-numeral', 'speak-punctuation', 'speech-rate', 'stress', 'text-align', 'text-decoration', 'text-indent', 'unicode-bidi', 'vertical-align', 'voice-family', 'volume', 'white-space', 'width', } # survey of common keywords found in feeds acceptable_css_keywords = { '!important', 'aqua', 'auto', 'black', 'block', 'blue', 'bold', 'both', 'bottom', 'brown', 'center', 'collapse', 'dashed', 'dotted', 'fuchsia', 'gray', 'green', 'italic', 'left', 'lime', 'maroon', 'medium', 'navy', 'none', 'normal', 'nowrap', 'olive', 'pointer', 'purple', 'red', 'right', 'silver', 'solid', 'teal', 'top', 'transparent', 'underline', 'white', 'yellow', } valid_css_values = re.compile( r'^(' r'#[0-9a-f]+' # Hex values r'|rgb\(\d+%?,\d*%?,?\d*%?\)?' # RGB values r'|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?' # Sizes/widths r')$' ) mathml_elements = { 'annotation', 'annotation-xml', 'maction', 'maligngroup', 'malignmark', 'math', 'menclose', 'merror', 'mfenced', 'mfrac', 'mglyph', 'mi', 'mlabeledtr', 'mlongdiv', 'mmultiscripts', 'mn', 'mo', 'mover', 'mpadded', 'mphantom', 'mprescripts', 'mroot', 'mrow', 'ms', 'mscarries', 'mscarry', 'msgroup', 'msline', 'mspace', 'msqrt', 'msrow', 'mstack', 'mstyle', 'msub', 'msubsup', 'msup', 'mtable', 'mtd', 'mtext', 'mtr', 'munder', 'munderover', 'none', 'semantics', } mathml_attributes = { 'accent', 'accentunder', 'actiontype', 'align', 'alignmentscope', 'altimg', 'altimg-height', 'altimg-valign', 'altimg-width', 'alttext', 'bevelled', 'charalign', 'close', 'columnalign', 'columnlines', 'columnspacing', 'columnspan', 'columnwidth', 'crossout', 'decimalpoint', 'denomalign', 'depth', 'dir', 'display', 'displaystyle', 'edge', 'encoding', 'equalcolumns', 'equalrows', 'fence', 'fontstyle', 'fontweight', 'form', 'frame', 'framespacing', 'groupalign', 'height', 'href', 'id', 'indentalign', 'indentalignfirst', 'indentalignlast', 'indentshift', 'indentshiftfirst', 'indentshiftlast', 'indenttarget', 'infixlinebreakstyle', 'largeop', 'length', 'linebreak', 'linebreakmultchar', 'linebreakstyle', 'lineleading', 'linethickness', 'location', 'longdivstyle', 'lquote', 'lspace', 'mathbackground', 'mathcolor', 'mathsize', 'mathvariant', 'maxsize', 'minlabelspacing', 'minsize', 'movablelimits', 'notation', 'numalign', 'open', 'other', 'overflow', 'position', 'rowalign', 'rowlines', 'rowspacing', 'rowspan', 'rquote', 'rspace', 'scriptlevel', 'scriptminsize', 'scriptsizemultiplier', 'selection', 'separator', 'separators', 'shift', 'side', 'src', 'stackalign', 'stretchy', 'subscriptshift', 'superscriptshift', 'symmetric', 'voffset', 'width', 'xlink:href', 'xlink:show', 'xlink:type', 'xmlns', 'xmlns:xlink', } # svgtiny - foreignObject + linearGradient + radialGradient + stop svg_elements = { 'a', 'animate', 'animateColor', 'animateMotion', 'animateTransform', 'circle', 'defs', 'desc', 'ellipse', 'font-face', 'font-face-name', 'font-face-src', 'foreignObject', 'g', 'glyph', 'hkern', 'line', 'linearGradient', 'marker', 'metadata', 'missing-glyph', 'mpath', 'path', 'polygon', 'polyline', 'radialGradient', 'rect', 'set', 'stop', 'svg', 'switch', 'text', 'title', 'tspan', 'use', } # svgtiny + class + opacity + offset + xmlns + xmlns:xlink svg_attributes = { 'accent-height', 'accumulate', 'additive', 'alphabetic', 'arabic-form', 'ascent', 'attributeName', 'attributeType', 'baseProfile', 'bbox', 'begin', 'by', 'calcMode', 'cap-height', 'class', 'color', 'color-rendering', 'content', 'cx', 'cy', 'd', 'descent', 'display', 'dur', 'dx', 'dy', 'end', 'fill', 'fill-opacity', 'fill-rule', 'font-family', 'font-size', 'font-stretch', 'font-style', 'font-variant', 'font-weight', 'from', 'fx', 'fy', 'g1', 'g2', 'glyph-name', 'gradientUnits', 'hanging', 'height', 'horiz-adv-x', 'horiz-origin-x', 'id', 'ideographic', 'k', 'keyPoints', 'keySplines', 'keyTimes', 'lang', 'marker-end', 'marker-mid', 'marker-start', 'markerHeight', 'markerUnits', 'markerWidth', 'mathematical', 'max', 'min', 'name', 'offset', 'opacity', 'orient', 'origin', 'overline-position', 'overline-thickness', 'panose-1', 'path', 'pathLength', 'points', 'preserveAspectRatio', 'r', 'refX', 'refY', 'repeatCount', 'repeatDur', 'requiredExtensions', 'requiredFeatures', 'restart', 'rotate', 'rx', 'ry', 'slope', 'stemh', 'stemv', 'stop-color', 'stop-opacity', 'strikethrough-position', 'strikethrough-thickness', 'stroke', 'stroke-dasharray', 'stroke-dashoffset', 'stroke-linecap', 'stroke-linejoin', 'stroke-miterlimit', 'stroke-opacity', 'stroke-width', 'systemLanguage', 'target', 'text-anchor', 'to', 'transform', 'type', 'u1', 'u2', 'underline-position', 'underline-thickness', 'unicode', 'unicode-range', 'units-per-em', 'values', 'version', 'viewBox', 'visibility', 'width', 'widths', 'x', 'x-height', 'x1', 'x2', 'xlink:actuate', 'xlink:arcrole', 'xlink:href', 'xlink:role', 'xlink:show', 'xlink:title', 'xlink:type', 'xml:base', 'xml:lang', 'xml:space', 'xmlns', 'xmlns:xlink', 'y', 'y1', 'y2', 'zoomAndPan', } svg_attr_map = None svg_elem_map = None acceptable_svg_properties = { 'fill', 'fill-opacity', 'fill-rule', 'stroke', 'stroke-linecap', 'stroke-linejoin', 'stroke-opacity', 'stroke-width', } def __init__(self, encoding=None, _type='application/xhtml+xml'): super().__init__(encoding, _type) self.unacceptablestack = 0 self.mathmlOK = 0 self.svgOK = 0 def reset(self): super().reset() self.unacceptablestack = 0 self.mathmlOK = 0 self.svgOK = 0 def unknown_starttag(self, tag, attrs): acceptable_attributes = self.acceptable_attributes keymap = {} if tag not in self.acceptable_elements or self.svgOK: if tag in self.unacceptable_elements_with_end_tag: self.unacceptablestack += 1 # add implicit namespaces to html5 inline svg/mathml if self._type.endswith('html'): if not dict(attrs).get('xmlns'): if tag == 'svg': attrs.append(('xmlns', 'http://www.w3.org/2000/svg')) if tag == 'math': attrs.append(('xmlns', 'http://www.w3.org/1998/Math/MathML')) # not otherwise acceptable, perhaps it is MathML or SVG? if tag == 'math' and ('xmlns', 'http://www.w3.org/1998/Math/MathML') in attrs: self.mathmlOK += 1 if tag == 'svg' and ('xmlns', 'http://www.w3.org/2000/svg') in attrs: self.svgOK += 1 # chose acceptable attributes based on tag class, else bail if self.mathmlOK and tag in self.mathml_elements: acceptable_attributes = self.mathml_attributes elif self.svgOK and tag in self.svg_elements: # For most vocabularies, lowercasing is a good idea. Many # svg elements, however, are camel case. if not self.svg_attr_map: lower = [attr.lower() for attr in self.svg_attributes] mix = [a for a in self.svg_attributes if a not in lower] self.svg_attributes = lower self.svg_attr_map = {a.lower(): a for a in mix} lower = [attr.lower() for attr in self.svg_elements] mix = [a for a in self.svg_elements if a not in lower] self.svg_elements = lower self.svg_elem_map = {a.lower(): a for a in mix} acceptable_attributes = self.svg_attributes tag = self.svg_elem_map.get(tag, tag) keymap = self.svg_attr_map elif tag not in self.acceptable_elements: return # declare xlink namespace, if needed if self.mathmlOK or self.svgOK: if any((a for a in attrs if a[0].startswith('xlink:'))): if not ('xmlns:xlink', 'http://www.w3.org/1999/xlink') in attrs: attrs.append(('xmlns:xlink', 'http://www.w3.org/1999/xlink')) clean_attrs = [] for key, value in self.normalize_attrs(attrs): if key == 'style' and 'style' in acceptable_attributes: clean_value = self.sanitize_style(value) if clean_value: clean_attrs.append((key, clean_value)) elif key in acceptable_attributes: key = keymap.get(key, key) # make sure the uri uses an acceptable uri scheme if key == 'href': value = make_safe_absolute_uri(value) clean_attrs.append((key, value)) super().unknown_starttag(tag, clean_attrs) def unknown_endtag(self, tag): if tag not in self.acceptable_elements: if tag in self.unacceptable_elements_with_end_tag: self.unacceptablestack -= 1 if self.mathmlOK and tag in self.mathml_elements: if tag == 'math' and self.mathmlOK: self.mathmlOK -= 1 elif self.svgOK and tag in self.svg_elements: tag = self.svg_elem_map.get(tag, tag) if tag == 'svg' and self.svgOK: self.svgOK -= 1 else: return super().unknown_endtag(tag) def handle_pi(self, text): pass def handle_decl(self, text): pass def handle_data(self, text): if not self.unacceptablestack: super().handle_data(text) def sanitize_style(self, style): # disallow urls style = re.compile(r'url\s*\(\s*[^\s)]+?\s*\)\s*').sub(' ', style) # gauntlet if not re.match(r"""^([:,;#%.\sa-zA-Z0-9!]|\w-\w|'[\s\w]+'|"[\s\w]+"|\([\d,\s]+\))*$""", style): return '' # This replaced a regexp that used re.match and was prone to # pathological back-tracking. if re.sub(r"\s*[-\w]+\s*:\s*[^:;]*;?", '', style).strip(): return '' clean = [] for prop, value in re.findall(r"([-\w]+)\s*:\s*([^:;]*)", style): if not value: continue if prop.lower() in self.acceptable_css_properties: clean.append(prop + ': ' + value + ';') elif prop.split('-')[0].lower() in ['background', 'border', 'margin', 'padding']: for keyword in value.split(): if ( keyword not in self.acceptable_css_keywords and not self.valid_css_values.match(keyword) ): break else: clean.append(prop + ': ' + value + ';') elif self.svgOK and prop.lower() in self.acceptable_svg_properties: clean.append(prop + ': ' + value + ';') return ' '.join(clean) def parse_comment(self, i, report=1): ret = super().parse_comment(i, report) if ret >= 0: return ret # if ret == -1, this may be a malicious attempt to circumvent # sanitization, or a page-destroying unclosed comment match = re.compile(r'--[^>]*>').search(self.rawdata, i+4) if match: return match.end() # unclosed comment; deliberately fail to handle_data() return len(self.rawdata) def sanitize_html(html_source, encoding, _type): p = HTMLSanitizer(encoding, _type) html_source = html_source.replace(' RE_ENTITY_PATTERN = re.compile(br'^\s*]*?)>', re.MULTILINE) # Match XML DOCTYPE declarations. # Example: RE_DOCTYPE_PATTERN = re.compile(br'^\s*]*?)>', re.MULTILINE) # Match safe entity declarations. # This will allow hexadecimal character references through, # as well as text, but not arbitrary nested entities. # Example: cubed "³" # Example: copyright "(C)" # Forbidden: explode1 "&explode2;&explode2;" RE_SAFE_ENTITY_PATTERN = re.compile(br'\s+(\w+)\s+"(&#\w+;|[^&"]*)"') def replace_doctype(data): """Strips and replaces the DOCTYPE, returns (rss_version, stripped_data) rss_version may be 'rss091n' or None stripped_data is the same XML document with a replaced DOCTYPE """ # Divide the document into two groups by finding the location # of the first element that doesn't begin with '\n\n]>' data = RE_DOCTYPE_PATTERN.sub(replacement, head) + data # Precompute the safe entities for the loose parser. safe_entities = { k.decode('utf-8'): v.decode('utf-8') for k, v in RE_SAFE_ENTITY_PATTERN.findall(replacement) } return version, data, safe_entities