sanitizer.js

'use strict';

/*
 * HTML Parser By Misko Hevery (misko@hevery.com)
 * based on:  HTML Parser By John Resig (ejohn.org)
 * Original code by Erik Arvidsson, Mozilla Public License
 * http://erik.eae.net/simplehtmlparser/simplehtmlparser.js
 *
 * // Use like so:
 * htmlParser(htmlString, {
 *     start: function(tag, attrs, unary) {},
 *     end: function(tag) {},
 *     chars: function(text) {},
 *     comment: function(text) {}
 * });
 *
 */

// Regular Expressions for parsing tags and attributes
var START_TAG_REGEXP = /^<\s*([\w:-]+)((?:\s+[\w:-]+(?:\s*=\s*(?:(?:"[^"]*")|(?:'[^']*')|[^>\s]+))?)*)\s*(\/?)\s*>/,
  END_TAG_REGEXP = /^<\s*\/\s*([\w:-]+)[^>]*>/,
  ATTR_REGEXP = /([\w:-]+)(?:\s*=\s*(?:(?:"((?:[^"])*)")|(?:'((?:[^'])*)')|([^>\s]+)))?/g,
  BEGIN_TAG_REGEXP = /^</,
  BEGING_END_TAGE_REGEXP = /^<\s*\//,
  COMMENT_REGEXP = /<!--(.*?)-->/g,
  CDATA_REGEXP = /<!\[CDATA\[(.*?)]]>/g,
  URI_REGEXP = /^((ftp|https?):\/\/|mailto:|#)/,
  NON_ALPHANUMERIC_REGEXP = /([^\#-~| |!])/g; // Match everything outside of normal chars and " (quote character)


// Good source of info about elements and attributes
// http://dev.w3.org/html5/spec/Overview.html#semantics
// http://simon.html5.org/html-elements

// Safe Void Elements - HTML5
// http://dev.w3.org/html5/spec/Overview.html#void-elements
var voidElements = makeMap("area,br,col,hr,img,wbr");

// Elements that you can, intentionally, leave open (and which close themselves)
// http://dev.w3.org/html5/spec/Overview.html#optional-tags
var optionalEndTagBlockElements = makeMap("colgroup,dd,dt,li,p,tbody,td,tfoot,th,thead,tr"),
    optionalEndTagInlineElements = makeMap("rp,rt"),
    optionalEndTagElements = extend({}, optionalEndTagInlineElements, optionalEndTagBlockElements);

// Safe Block Elements - HTML5
var blockElements = extend({}, optionalEndTagBlockElements, makeMap("address,article,aside," +
        "blockquote,caption,center,del,dir,div,dl,figure,figcaption,footer,h1,h2,h3,h4,h5,h6," +
        "header,hgroup,hr,ins,map,menu,nav,ol,pre,script,section,table,ul"));

// Inline Elements - HTML5
var inlineElements = extend({}, optionalEndTagInlineElements, makeMap("a,abbr,acronym,b,bdi,bdo," +
        "big,br,cite,code,del,dfn,em,font,i,img,ins,kbd,label,map,mark,q,ruby,rp,rt,s,samp,small," +
        "span,strike,strong,sub,sup,time,tt,u,var"));


// Special Elements (can contain anything)
var specialElements = makeMap("script,style");

var validElements = extend({}, voidElements, blockElements, inlineElements, optionalEndTagElements);

//Attributes that have href and hence need to be sanitized
var uriAttrs = makeMap("background,cite,href,longdesc,src,usemap");
var validAttrs = extend({}, uriAttrs, makeMap(
    'abbr,align,alt,axis,bgcolor,border,cellpadding,cellspacing,class,clear,'+
    'color,cols,colspan,compact,coords,dir,face,headers,height,hreflang,hspace,'+
    'ismap,lang,language,nohref,nowrap,rel,rev,rows,rowspan,rules,'+
    'scope,scrolling,shape,span,start,summary,target,title,type,'+
    'valign,value,vspace,width'));

/**
 * @example
 * htmlParser(htmlString, {
 *     start: function(tag, attrs, unary) {},
 *     end: function(tag) {},
 *     chars: function(text) {},
 *     comment: function(text) {}
 * });
 *
 * @param {string} html string
 * @param {object} handler
 */
function htmlParser( html, handler ) {
  var index, chars, match, stack = [], last = html;
  stack.last = function() { return stack[ stack.length - 1 ]; };

  while ( html ) {
    chars = true;

    // Make sure we're not in a script or style element
    if ( !stack.last() || !specialElements[ stack.last() ] ) {

      // Comment
      if ( html.indexOf("<!--") === 0 ) {
        index = html.indexOf("-->");

        if ( index >= 0 ) {
          if (handler.comment) handler.comment( html.substring( 4, index ) );
          html = html.substring( index + 3 );
          chars = false;
        }

      // end tag
      } else if ( BEGING_END_TAGE_REGEXP.test(html) ) {
        match = html.match( END_TAG_REGEXP );

        if ( match ) {
          html = html.substring( match[0].length );
          match[0].replace( END_TAG_REGEXP, parseEndTag );
          chars = false;
        }

      // start tag
      } else if ( BEGIN_TAG_REGEXP.test(html) ) {
        match = html.match( START_TAG_REGEXP );

        if ( match ) {
          html = html.substring( match[0].length );
          match[0].replace( START_TAG_REGEXP, parseStartTag );
          chars = false;
        }
      }

      if ( chars ) {
        index = html.indexOf("<");

        var text = index < 0 ? html : html.substring( 0, index );
        html = index < 0 ? "" : html.substring( index );

        if (handler.chars) handler.chars( decodeEntities(text) );
      }

    } else {
      html = html.replace(new RegExp("(.*)<\\s*\\/\\s*" + stack.last() + "[^>]*>", 'i'), function(all, text){
        text = text.
          replace(COMMENT_REGEXP, "$1").
          replace(CDATA_REGEXP, "$1");

        if (handler.chars) handler.chars( decodeEntities(text) );

        return "";
      });

      parseEndTag( "", stack.last() );
    }

    if ( html == last ) {
      throw "Parse Error: " + html;
    }
    last = html;
  }

  // Clean up any remaining tags
  parseEndTag();

  function parseStartTag( tag, tagName, rest, unary ) {
    tagName = lowercase(tagName);
    if ( blockElements[ tagName ] ) {
      while ( stack.last() && inlineElements[ stack.last() ] ) {
        parseEndTag( "", stack.last() );
      }
    }

    if ( optionalEndTagElements[ tagName ] && stack.last() == tagName ) {
      parseEndTag( "", tagName );
    }

    unary = voidElements[ tagName ] || !!unary;

    if ( !unary )
      stack.push( tagName );

    var attrs = {};

    rest.replace(ATTR_REGEXP, function(match, name, doubleQuotedValue, singleQoutedValue, unqoutedValue) {
      var value = doubleQuotedValue
        || singleQoutedValue
        || unqoutedValue
        || '';

      attrs[name] = decodeEntities(value);
    });
    if (handler.start) handler.start( tagName, attrs, unary );
  }

  function parseEndTag( tag, tagName ) {
    var pos = 0, i;
    tagName = lowercase(tagName);
    if ( tagName )
      // Find the closest opened tag of the same type
      for ( pos = stack.length - 1; pos >= 0; pos-- )
        if ( stack[ pos ] == tagName )
          break;

    if ( pos >= 0 ) {
      // Close all the open elements, up the stack
      for ( i = stack.length - 1; i >= pos; i-- )
        if (handler.end) handler.end( stack[ i ] );

      // Remove the open elements from the stack
      stack.length = pos;
    }
  }
}

/**
 * decodes all entities into regular string
 * @param value
 * @returns {string} A string with decoded entities.
 */
var hiddenPre=document.createElement("pre");
function decodeEntities(value) {
  hiddenPre.innerHTML=value.replace(/</g,"&lt;");
  return hiddenPre.innerText || hiddenPre.textContent || '';
}

/**
 * Escapes all potentially dangerous characters, so that the
 * resulting string can be safely inserted into attribute or
 * element text.
 * @param value
 * @returns escaped text
 */
function encodeEntities(value) {
  return value.
    replace(/&/g, '&amp;').
    replace(NON_ALPHANUMERIC_REGEXP, function(value){
      return '&#' + value.charCodeAt(0) + ';';
    }).
    replace(/</g, '&lt;').
    replace(/>/g, '&gt;');
}

/**
 * create an HTML/XML writer which writes to buffer
 * @param {Array} buf use buf.jain('') to get out sanitized html string
 * @returns {object} in the form of {
 *     start: function(tag, attrs, unary) {},
 *     end: function(tag) {},
 *     chars: function(text) {},
 *     comment: function(text) {}
 * }
 */
function htmlSanitizeWriter(buf){
  var ignore = false;
  var out = bind(buf, buf.push);
  return {
    start: function(tag, attrs, unary){
      tag = lowercase(tag);
      if (!ignore && specialElements[tag]) {
        ignore = tag;
      }
      if (!ignore && validElements[tag] == true) {
        out('<');
        out(tag);
        forEach(attrs, function(value, key){
          var lkey=lowercase(key);
          if (validAttrs[lkey]==true && (uriAttrs[lkey]!==true || value.match(URI_REGEXP))) {
            out(' ');
            out(key);
            out('="');
            out(encodeEntities(value));
            out('"');
          }
        });
        out(unary ? '/>' : '>');
      }
    },
    end: function(tag){
        tag = lowercase(tag);
        if (!ignore && validElements[tag] == true) {
          out('</');
          out(tag);
          out('>');
        }
        if (tag == ignore) {
          ignore = false;
        }
      },
    chars: function(chars){
        if (!ignore) {
          out(encodeEntities(chars));
        }
      }
  };
}