js-xss/lib/xss.js

/**
 * 过滤XSS
 *
 * @author 老雷<leizongmin@gmail.com>
 */

var DEFAULT = require('./default');
var parser = require('./parser');
var parseTag = parser.parseTag;
var parseAttr = parser.parseAttr;


/**
 * 返回值是否为空
 *
 * @param {Object} obj
 * @return {Boolean}
 */
function isNull (obj) {
  return (obj === undefined || obj === null);
}

/**
 * 取标签内的属性列表字符串
 *
 * @param {String} html
 * @return {Object}
 *   - {String} html
 *   - {Boolean} closing
 */
function getAttrs (html) {
  var i = html.indexOf(' ');
  if (i === -1) {
    return {
      html:    '',
      closing: (html[html.length - 2] === '/')
    };
  }
  html = html.slice(i + 1, -1).trim();
  var isClosing = (html[html.length - 1] === '/');
  if (isClosing) html = html.slice(0, -1).trim();
  return {
    html:    html,
    closing: isClosing
  };
}

/**
 * XSS过滤对象
 *
 * @param {Object} options 选项：whiteList, onTag, onTagAttr, onIgnoreTag,
 *                               onIgnoreTagAttr, safeAttrValue, escapeHtml
 *                               stripIgnoreTagBody
 */
function FilterXSS (options) {
  options = options || {};

  if (options.stripIgnoreTag) {
    if (options.onIgnoreTag) {
      console.error('Notes: cannot use these two options "stripIgnoreTag" and "onIgnoreTag" at the same time');
    }
    options.onIgnoreTag = DEFAULT.onIgnoreTagStripAll;
  }

  options.whiteList = options.whiteList || DEFAULT.whiteList;
  options.onTag = options.onTag || DEFAULT.onTag;
  options.onTagAttr = options.onTagAttr || DEFAULT.onTagAttr;
  options.onIgnoreTag = options.onIgnoreTag || DEFAULT.onIgnoreTag;
  options.onIgnoreTagAttr = options.onIgnoreTagAttr || DEFAULT.onIgnoreTagAttr;
  options.safeAttrValue = options.safeAttrValue || DEFAULT.safeAttrValue;
  options.escapeHtml = options.escapeHtml || DEFAULT.escapeHtml;
  this.options = options;
}

/**
 * 开始处理
 *
 * @param {String} html
 * @return {String}
 */
FilterXSS.prototype.process = function (html) {
  var me = this;
  var options = me.options;
  var whiteList = options.whiteList;
  var onTag = options.onTag;
  var onIgnoreTag = options.onIgnoreTag;
  var onTagAttr = options.onTagAttr;
  var onIgnoreTagAttr = options.onIgnoreTagAttr;
  var safeAttrValue = options.safeAttrValue;
  var escapeHtml = options.escapeHtml

  // 如果开启了stripIgnoreTagBody
  if (options.stripIgnoreTagBody) {
    var stripIgnoreTagBody = DEFAULT.StripTagBody(options.stripIgnoreTagBody, onIgnoreTag);
    onIgnoreTag = stripIgnoreTagBody.onIgnoreTag;
  } else {
    stripIgnoreTagBody = false;
  }

  var retHtml = parseTag(html, function (sourcePosition, position, tag, html, isClosing) {
    var info = {
      sourcePosition: sourcePosition,
      position:       position,
      isClosing:      isClosing,
      isWhite:        (tag in whiteList)
    };

    // 调用onTag处理
    var ret = onTag(tag, html, info);
    if (!isNull(ret)) return ret;

    // 默认标签处理方法
    if (info.isWhite) {
      // 白名单标签，解析标签属性
      // 如果是闭合标签，则不需要解析属性
      if (info.isClosing) {
        return '</' + tag + '>';
      }

      var attrs = getAttrs(html);
      var whiteAttrList = whiteList[tag];
      var attrsHtml = parseAttr(attrs.html, function (name, value) {

        // 调用onTagAttr处理
        var isWhiteAttr = (whiteAttrList.indexOf(name) !== -1);
        var ret = onTagAttr(tag, name, value, isWhiteAttr);
        if (!isNull(ret)) return ret;

        // 默认的属性处理方法
        if (isWhiteAttr) {
          // 白名单属性，调用onIgnoreTagAttr过滤属性值
          value = safeAttrValue(tag, name, value);
          if (value) {
            return name + '="' + value + '"';
          } else {
            return name;
          }
        } else {
          // 非白名单属性，调用onIgnoreTagAttr处理
          var ret = onIgnoreTagAttr(tag, name, value, isWhiteAttr);
          if (!isNull(ret)) return ret;
          return;
        }
      });

      // 构造新的标签代码
      var html = '<' + tag;
      if (attrsHtml) html += ' ' + attrsHtml;
      if (attrs.closing) html += ' /';
      html += '>';
      return html;

    } else {
      // 非白名单标签，调用onIgnoreTag处理
      var ret = onIgnoreTag(tag, html, info);
      if (!isNull(ret)) return ret;
      return escapeHtml(html);
    }

  }, escapeHtml);

  // 如果开启了stripIgnoreTagBody，需要对结果再进行处理
  if (stripIgnoreTagBody) {
    retHtml = stripIgnoreTagBody.remove(retHtml);
  }

  return retHtml;
};


module.exports = FilterXSS;