sanitize.js

'use strict';

var $sanitizeMinErr = angular.$$minErr('$sanitize');

/**
 * @ngdoc overview
 * @name ngSanitize
 * @description
 *
 * # ngSanitize
 *
 * The `ngSanitize` module provides functionality to sanitize HTML.
 *
 * {@installModule sanitize}
 *
 * <div doc-module-components="ngSanitize"></div>
 *
 * See {@link ngSanitize.$sanitize `$sanitize`} for usage.
 */

/*
 * 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) {}
 * });
 *
 */


/**
 * @ngdoc service
 * @name ngSanitize.$sanitize
 * @function
 *
 * @description
 *   The input is sanitized by parsing the html into tokens. All safe tokens (from a whitelist) are
 *   then serialized back to properly escaped html string. This means that no unsafe input can make
 *   it into the returned string, however, since our parser is more strict than a typical browser
 *   parser, it's possible that some obscure input, which would be recognized as valid HTML by a
 *   browser, won't make it through the sanitizer.
 *   The whitelist is configured using the functions `aHrefSanitizationWhitelist` and
 *   `imgSrcSanitizationWhitelist` of {@link ng.$compileProvider `$compileProvider`}.
 *
 * @param {string} html Html input.
 * @returns {string} Sanitized html.
 *
 * @example
   <doc:example module="ngSanitize">
   <doc:source>
     <script>
       function Ctrl($scope, $sce) {
         $scope.snippet =
           '<p style="color:blue">an html\n' +
           '<em onmouseover="this.textContent=\'PWN3D!\'">click here</em>\n' +
           'snippet</p>';
         $scope.deliberatelyTrustDangerousSnippet = function() {
           return $sce.trustAsHtml($scope.snippet);
         };
       }
     </script>
     <div ng-controller="Ctrl">
        Snippet: <textarea ng-model="snippet" cols="60" rows="3"></textarea>
       <table>
         <tr>
           <td>Directive</td>
           <td>How</td>
           <td>Source</td>
           <td>Rendered</td>
         </tr>
         <tr id="bind-html-with-sanitize">
           <td>ng-bind-html</td>
           <td>Automatically uses $sanitize</td>
           <td><pre>&lt;div ng-bind-html="snippet"&gt;<br/>&lt;/div&gt;</pre></td>
           <td><div ng-bind-html="snippet"></div></td>
         </tr>
         <tr id="bind-html-with-trust">
           <td>ng-bind-html</td>
           <td>Bypass $sanitize by explicitly trusting the dangerous value</td>
           <td>
           <pre>&lt;div ng-bind-html="deliberatelyTrustDangerousSnippet()"&gt;
&lt;/div&gt;</pre>
           </td>
           <td><div ng-bind-html="deliberatelyTrustDangerousSnippet()"></div></td>
         </tr>
         <tr id="bind-default">
           <td>ng-bind</td>
           <td>Automatically escapes</td>
           <td><pre>&lt;div ng-bind="snippet"&gt;<br/>&lt;/div&gt;</pre></td>
           <td><div ng-bind="snippet"></div></td>
         </tr>
       </table>
       </div>
   </doc:source>
   <doc:scenario>
     it('should sanitize the html snippet by default', function() {
       expect(using('#bind-html-with-sanitize').element('div').html()).
         toBe('<p>an html\n<em>click here</em>\nsnippet</p>');
     });

     it('should inline raw snippet if bound to a trusted value', function() {
       expect(using('#bind-html-with-trust').element("div").html()).
         toBe("<p style=\"color:blue\">an html\n" +
              "<em onmouseover=\"this.textContent='PWN3D!'\">click here</em>\n" +
              "snippet</p>");
     });

     it('should escape snippet without any filter', function() {
       expect(using('#bind-default').element('div').html()).
         toBe("&lt;p style=\"color:blue\"&gt;an html\n" +
              "&lt;em onmouseover=\"this.textContent='PWN3D!'\"&gt;click here&lt;/em&gt;\n" +
              "snippet&lt;/p&gt;");
     });

     it('should update', function() {
       input('snippet').enter('new <b onclick="alert(1)">text</b>');
       expect(using('#bind-html-with-sanitize').element('div').html()).toBe('new <b>text</b>');
       expect(using('#bind-html-with-trust').element('div').html()).toBe(
         'new <b onclick="alert(1)">text</b>');
       expect(using('#bind-default').element('div').html()).toBe(
         "new &lt;b onclick=\"alert(1)\"&gt;text&lt;/b&gt;");
     });
   </doc:scenario>
   </doc:example>
 */
function $SanitizeProvider() {
  this.$get = ['$$sanitizeUri', function($$sanitizeUri) {
    return function(html) {
      var buf = [];
      htmlParser(html, htmlSanitizeWriter(buf, function(uri, isImage) {
        return !/^unsafe/.test($$sanitizeUri(uri, isImage));
      }));
      return buf.join('');
    };
  }];
}

function sanitizeText(chars) {
  var buf = [];
  var writer = htmlSanitizeWriter(buf, angular.noop);
  writer.chars(chars);
  return buf.join('');
}


// 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,
  DOCTYPE_REGEXP = /<!DOCTYPE([^>]*?)>/i,
  CDATA_REGEXP = /<!\[CDATA\[(.*?)]]>/g,
  // Match everything outside of normal chars and " (quote character)
  NON_ALPHANUMERIC_REGEXP = /([^\#-~| |!])/g;


// 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 = angular.extend({},
                                            optionalEndTagInlineElements,
                                            optionalEndTagBlockElements);

// Safe Block Elements - HTML5
var blockElements = angular.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 = angular.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 = angular.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 = angular.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'));

function makeMap(str) {
  var obj = {}, items = str.split(','), i;
  for (i = 0; i < items.length; i++) obj[items[i]] = true;
  return obj;
}


/**
 * @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 ) {
        // comments containing -- are not allowed unless they terminate the comment
        index = html.indexOf("--", 4);

        if ( index >= 0 && html.lastIndexOf("-->", index) === index) {
          if (handler.comment) handler.comment( html.substring( 4, index ) );
          html = html.substring( index + 3 );
          chars = false;
        }
      // DOCTYPE
      } else if ( DOCTYPE_REGEXP.test(html) ) {
        match = html.match( DOCTYPE_REGEXP );

        if ( match ) {
          html = html.replace( match[0] , '');
          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 $sanitizeMinErr('badparse', "The sanitizer was unable to parse the following block " +
                                        "of html: {0}", html);
    }
    last = html;
  }

  // Clean up any remaining tags
  parseEndTag();

  function parseStartTag( tag, tagName, rest, unary ) {
    tagName = angular.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, singleQuotedValue, unquotedValue) {
        var value = doubleQuotedValue
          || singleQuotedValue
          || unquotedValue
          || '';

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

  function parseEndTag( tag, tagName ) {
    var pos = 0, i;
    tagName = angular.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) {
  if (!value) {
    return '';
  }
  // Note: IE8 does not preserve spaces at the start/end of innerHTML
  var spaceRe = /^(\s*)([\s\S]*?)(\s*)$/;
  var parts = spaceRe.exec(value);
  if (parts[2]) {
    hiddenPre.innerHTML=parts[2].replace(/</g,"&lt;");
    parts[2] = hiddenPre.innerText || hiddenPre.textContent;
  }
  parts[0] = '';
  return parts.join('');
}

/**
 * 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, uriValidator){
  var ignore = false;
  var out = angular.bind(buf, buf.push);
  return {
    start: function(tag, attrs, unary){
      tag = angular.lowercase(tag);
      if (!ignore && specialElements[tag]) {
        ignore = tag;
      }
      if (!ignore && validElements[tag] === true) {
        out('<');
        out(tag);
        angular.forEach(attrs, function(value, key){
          var lkey=angular.lowercase(key);
          var isImage = (tag === 'img' && lkey === 'src') || (lkey === 'background');
          if (validAttrs[lkey] === true &&
            (uriAttrs[lkey] !== true || uriValidator(value, isImage))) {
            out(' ');
            out(key);
            out('="');
            out(encodeEntities(value));
            out('"');
          }
        });
        out(unary ? '/>' : '>');
      }
    },
    end: function(tag){
        tag = angular.lowercase(tag);
        if (!ignore && validElements[tag] === true) {
          out('</');
          out(tag);
          out('>');
        }
        if (tag == ignore) {
          ignore = false;
        }
      },
    chars: function(chars){
        if (!ignore) {
          out(encodeEntities(chars));
        }
      }
  };
}


// define ngSanitize module and register $sanitize service
angular.module('ngSanitize', []).provider('$sanitize', $SanitizeProvider);