require 'cgi' require 'html5/tokenizer' module HTML5 # This module provides sanitization of XHTML+MathML+SVG # and of inline style attributes. # # It can be either at the Tokenizer stage: # # HTMLParser.parse(html, :tokenizer => HTMLSanitizer) # # or, if you already have a parse tree (in this example, a REXML tree), # at the Serializer stage: # # tokens = TreeWalkers.get_tree_walker('rexml').new(tree) # HTMLSerializer.serialize(tokens, {:encoding=>'utf-8', # :sanitize => true}) module HTMLSanitizeModule ACCEPTABLE_ELEMENTS = %w[a abbr acronym address area b big blockquote br button caption center cite code col colgroup dd del dfn dir div dl dt em fieldset font form h1 h2 h3 h4 h5 h6 hr i img input ins kbd label legend li map menu ol optgroup option p pre q s samp select small span strike strong sub sup table tbody td textarea tfoot th thead tr tt u ul var] MATHML_ELEMENTS = %w[maction math merror mfrac mi mmultiscripts mn mo mover mpadded mphantom mprescripts mroot mrow mspace msqrt mstyle msub msubsup msup mtable mtd mtext mtr munder munderover none] SVG_ELEMENTS = %w[a animate animateColor animateMotion animateTransform circle defs desc ellipse font-face font-face-name font-face-src g glyph hkern image linearGradient line marker metadata missing-glyph mpath path polygon polyline radialGradient rect set stop svg switch text title tspan use] ACCEPTABLE_ATTRIBUTES = %w[abbr accept accept-charset accesskey action align alt axis border cellpadding cellspacing char charoff charset checked cite class clear cols colspan color compact coords datetime dir disabled enctype for frame headers height href hreflang hspace id ismap label lang longdesc maxlength media method multiple name nohref noshade nowrap prompt readonly rel rev rows rowspan rules scope selected shape size span src start style summary tabindex target title type usemap valign value vspace width xml:lang] MATHML_ATTRIBUTES = %w[actiontype align columnalign columnalign columnalign columnlines columnspacing columnspan depth display displaystyle equalcolumns equalrows fence fontstyle fontweight frame height linethickness lspace mathbackground mathcolor mathvariant mathvariant maxsize minsize other rowalign rowalign rowalign rowlines rowspacing rowspan rspace scriptlevel selection separator stretchy width width xlink:href xlink:show xlink:type xmlns xmlns:xlink] SVG_ATTRIBUTES = %w[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 dx dy descent display dur end fill 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] ATTR_VAL_IS_URI = %w[href src cite action longdesc xlink:href xml:base] ACCEPTABLE_CSS_PROPERTIES = %w[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] ACCEPTABLE_CSS_KEYWORDS = %w[auto aqua black block blue bold both bottom brown center collapse dashed dotted fuchsia gray green !important italic left lime maroon medium none navy normal nowrap olive pointer purple red right solid silver teal top transparent underline white yellow] ACCEPTABLE_SVG_PROPERTIES = %w[fill fill-opacity fill-rule stroke stroke-width stroke-linecap stroke-linejoin stroke-opacity] ACCEPTABLE_PROTOCOLS = %w[ed2k ftp http https irc mailto news gopher nntp telnet webcal xmpp callto feed urn aim rsync tag ssh sftp rtsp afs] # subclasses may define their own versions of these constants ALLOWED_ELEMENTS = ACCEPTABLE_ELEMENTS + MATHML_ELEMENTS + SVG_ELEMENTS ALLOWED_ATTRIBUTES = ACCEPTABLE_ATTRIBUTES + MATHML_ATTRIBUTES + SVG_ATTRIBUTES ALLOWED_CSS_PROPERTIES = ACCEPTABLE_CSS_PROPERTIES ALLOWED_CSS_KEYWORDS = ACCEPTABLE_CSS_KEYWORDS ALLOWED_SVG_PROPERTIES = ACCEPTABLE_SVG_PROPERTIES ALLOWED_PROTOCOLS = ACCEPTABLE_PROTOCOLS def sanitize_token(token) case token[:type] when :StartTag, :EndTag, :EmptyTag if ALLOWED_ELEMENTS.include?(token[:name]) if token.has_key? :data attrs = Hash[*token[:data].flatten] attrs.delete_if { |attr,v| !ALLOWED_ATTRIBUTES.include?(attr) } ATTR_VAL_IS_URI.each do |attr| val_unescaped = CGI.unescapeHTML(attrs[attr].to_s).gsub(/`|[\000-\040\177\s]+|\302[\200-\240]/,'').downcase if val_unescaped =~ /^[a-z0-9][-+.a-z0-9]*:/ and !ALLOWED_PROTOCOLS.include?(val_unescaped.split(':')[0]) attrs.delete attr end end if attrs['style'] attrs['style'] = sanitize_css(attrs['style']) end token[:data] = attrs.map {|k,v| [k,v]} end return token else if token[:type] == :EndTag token[:data] = "" elsif token[:data] attrs = token[:data].map {|k,v| " #{k}=\"#{CGI.escapeHTML(v)}\""}.join('') token[:data] = "<#{token[:name]}#{attrs}>" else token[:data] = "<#{token[:name]}>" end token[:data].insert(-2,'/') if token[:type] == :EmptyTag token[:type] = :Characters token.delete(:name) return token end when :Comment token[:data] = "" return token else return token end end def sanitize_css(style) # disallow urls style = style.to_s.gsub(/url\s*\(\s*[^\s)]+?\s*\)\s*/, ' ') # gauntlet return '' unless style =~ /^([:,;#%.\sa-zA-Z0-9!]|\w-\w|\'[\s\w]+\'|\"[\s\w]+\"|\([\d,\s]+\))*$/ return '' unless style =~ /^(\s*[-\w]+\s*:\s*[^:;]*(;|$))*$/ clean = [] style.scan(/([-\w]+)\s*:\s*([^:;]*)/) do |prop, val| next if val.empty? prop.downcase! if ALLOWED_CSS_PROPERTIES.include?(prop) clean << "#{prop}: #{val};" elsif %w[background border margin padding].include?(prop.split('-')[0]) clean << "#{prop}: #{val};" unless val.split().any? do |keyword| !ALLOWED_CSS_KEYWORDS.include?(keyword) and keyword !~ /^(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)$/ end elsif ALLOWED_SVG_PROPERTIES.include?(prop) clean << "#{prop}: #{val};" end end style = clean.join(' ') end end class HTMLSanitizer < HTMLTokenizer include HTMLSanitizeModule def each super do |token| yield(sanitize_token(token)) end end end end